Anesthesia for patients with interstitial lung disease or other restrictive disorders

INTRODUCTION — Restrictive respiratory diseases are a heterogeneous group of disorders characterized on pulmonary function tests by reduced total lung capacity and decreased compliance, with preserved expiratory flow. These patients share a tendency towards smaller tidal volumes, higher respiratory rates, increased work of breathing, and frequent hypoxemia, all of which contribute to increased perioperative morbidity and mortality. This topic addresses anesthetic and perioperative management of patients with restrictive physiology due to [1,2]:

●Intrinsic disorders such as interstitial lung diseases (ILDs; also called diffuse parenchymal lung diseases) that cause diffuse inflammation or scarring of the lung tissue

●Extrinsic disorders such as abnormalities of the chest wall (eg, pectus excavatum, kyphoscoliosis), pleura (eg, effusion, trapped lung), or abdomen (eg, ascites, obesity, masses) that mechanically compress the lungs or limit their expansion

Management of patients with restrictive physiology due to neuromuscular disease is discussed in separate topics:

●(See "Respiratory muscle weakness due to neuromuscular disease: Clinical manifestations and evaluation".)

●(See "Respiratory muscle weakness due to neuromuscular disease: Management".)

●(See "Perioperative care of the surgical patient with neurologic disease".)

Perioperative and anesthetic management of patients with COPD are addressed in separate topics. (See "Evaluation of perioperative pulmonary risk" and "Anesthesia for patients with chronic obstructive pulmonary disease".)

PREANESTHETIC ASSESSMENT — Preanesthetic consultation for patients with chronic restrictive respiratory disease is similar to that for patients with other chronic pulmonary disease, and includes assessing the severity of lung disease and working with the patient's pulmonary specialist to optimize preoperative status. Comorbid conditions that can significantly impact overall perioperative risk are common in patients with chronic restrictive respiratory disease; treatable issues should be identified and managed [3]. (See "Anesthesia for patients with chronic obstructive pulmonary disease", section on 'Preanesthesia consultation'.)

Overview of pathologic processes causing restrictive lung disease — Patients with an underlying disease that causes restrictive physiology have decreased intrapulmonary or chest wall compliance, which impedes lung expansion. This results in increased work of breathing and/or reduced minute ventilation, as well as a predisposition to hypoxemia from intrinsic lung disease, lung atelectasis, or both. Hypoxemia due to preoperative atelectasis generally worsens in the perioperative setting due to hyperoxygenation and loss of muscle tone, which can exacerbate the condition [4]. (See "Evaluation of perioperative pulmonary risk", section on 'Interstitial lung disease'.)

In one study, the prevalence of a restrictive spirometric pattern on pulmonary function testing was approximately 7 to 11 percent, similar to the prevalence of a spirometric pattern indicating chronic obstructive pulmonary disease (COPD) [1]. Examples of pathological processes that cause such restrictive physiology include:

●Intrinsic restrictive lung disorders interstitial lung disease (ILD) – Various chronic intrinsic parenchymal lung disorders may cause inflammation or scarring of the lung tissue, which results in restriction on pulmonary function testing accompanied by impairments in gas exchange (algorithm 1) (see "Approach to the adult with interstitial lung disease: Clinical evaluation" and "Approach to the adult with interstitial lung disease: Diagnostic testing"):

•Exposure-associated ILDs – Several varieties of ILD arise from an immune or inflammatory response of the lung to repeated exposure to a pathogenic stimulus. These disorders share the feature that cessation of exposure usually improves lung function or halts disease progression (except in patients with severe chronic disease).

-Smoking related ILDs include respiratory bronchiolitis ILD, desquamative interstitial pneumonitis, and pulmonary Langerhans cell histiocytosis. Smoking cessation is the mainstay of treatment.

-A variety of occupational and environmental exposures are associated with ILD (table 1 and table 2). Organic exposures most frequently result in an acute granulomatous hypersensitivity reaction (hypersensitivity pneumonitis), whereas inorganic agents have several different presentations. Acute hypersensitivity pneumonitis can typically be effectively treated with anti-inflammatory agents; longstanding environmental exposure-related disease most typically results in lung fibrosis. (See "Approach to the adult with interstitial lung disease: Clinical evaluation", section on 'Occupational and environmental exposures'.)

-Drug-induced lung injury results in acute and occasionally chronic interstitial lung inflammation (table 3). Common offending agents include nitrofurantoin, bleomycin, and immune checkpoint inhibitors. Treatment usually entails discontinuation of the offending agent, with or without a few weeks of systemic glucocorticoid therapy. (See "Approach to the adult with interstitial lung disease: Clinical evaluation", section on 'Prior medication use and irradiation'.)

•Chronic fibrosing ILD – Idiopathic pulmonary fibrosis (IPF) is an ILD of unknown etiology characterized primarily by progressive scarring and restriction of the lung (image 1 and image 2 and image 3). Other lung diseases that may be associated with progressive fibrosis include non-specific interstitial pneumonitis, chronic hypersensitivity pneumonitis, and ILDs associated with autoimmune diseases. Progressive fibrotic lung diseases share a predisposition to "acute exacerbations," whereby lung injury results in marked worsening of disease over days to weeks with only partial recovery. Thoracoabdominal surgery and mechanical ventilation are potential risk factors for these exacerbations. (See "Acute exacerbations of idiopathic pulmonary fibrosis", section on 'Pathophysiology and risk factors'.)

•Granulomatous ILD – Granulomatous ILDs include sarcoidosis and rare granulomatous disorders (berylliosis, granulomatous-lymphocytic ILD). Sarcoidosis is an inflammatory disease that has protean manifestations in multiple organ systems, but it is most frequently found in the lung and intrathoracic lymph nodes. Many patients are asymptomatic with no or minimal lung disease, but others develop significant pulmonary symptoms, granulomatous inflammation, and lung scarring. Prednisone, methotrexate, and other anti-inflammatory therapies are effective at controlling active pulmonary disease in most symptomatic patients. (See "Clinical manifestations and diagnosis of sarcoidosis".)

•Organizing pneumonia – Organizing pneumonia can arise idiopathically (cryptogenic organizing pneumonia) or due to a variety of secondary causes (table 4). The pathology arises due to a reversible inflammatory and fibroproliferative process in the alveolar (not interstitial) space that does not disrupt the underlying lung architecture. Because of this, treatment with anti-inflammatory agents is generally effective at restoring normal pulmonary function. However, many patients develop disease recurrence and may require extended anti-inflammatory therapy. (See "Cryptogenic organizing pneumonia".)

•Connective tissue disease-associated ILD – Several connected tissue diseases are highly predisposed to development of ILD, including rheumatoid arthritis, polymyositis/dermatomyositis, systemic sclerosis, Sjögren syndrome, and systemic lupus erythematosus. Treatment with anti-inflammatory agents active in the lung is often effective, but progressive fibrotic changes develop in a significant minority over time. (See "Interstitial lung disease in rheumatoid arthritis" and "Overview of pulmonary complications of systemic sclerosis (scleroderma)" and "Interstitial lung disease in dermatomyositis and polymyositis: Clinical manifestations and diagnosis" and "Interstitial lung disease associated with Sjögren's disease: Clinical manifestations, evaluation, and diagnosis" and "Pulmonary manifestations of systemic lupus erythematosus in adults".)

Any intrinsic restrictive lung disease may also result in development of group 3 pulmonary hypertension (PH). Patients with sarcoidosis, systemic sclerosis, and very severe restrictive disease are at the highest risk. (See "Pulmonary hypertension due to lung disease and/or hypoxemia (group 3 pulmonary hypertension): Epidemiology, pathogenesis, and diagnostic evaluation in adults".)

●Extrinsic restrictive disorders – Several conditions extrinsic to the lung parenchyma result in chronically reduced lung volumes (eg, total lung capacity [TLC] and vital capacity [VC]) due to mechanical limitations on lung expansion. For most of these processes, the restrictive pattern on pulmonary function tests (PFTs; low TLC and VC) is not accompanied by abnormal gas transfer out of proportion to the limitation on lung expansion.

•Abnormalities of the chest wall or pleura – Processes that alter chest wall geometry and lesions that occupy space within the chest disrupt proper expansion of the lung during tidal breathing (see "Chest wall diseases and restrictive physiology"). Examples include:

-Space-occupying lesions – Pleural effusion, pneumothorax, hemothorax with pleural, and primary or metastatic tumors occupy space within the chest.

-Ankylosing spondylitis, kyphosis, scoliosis – Ankylosing spondylitis causes fixation of the chest wall through fusion of the costovertebral joints; kyphosis (ie, anteroposterior angulation of the spine) may also be present. (See "Chest wall diseases and restrictive physiology", section on 'Ankylosing spondylitis' and "Chest wall diseases and restrictive physiology", section on 'Kyphosis and scoliosis'.)

-Congenital abnormalities of the chest wall – Congenital deformities such as pectus excavatum and pectus carinatum may cause impaired lung expansion. These are discussed in more detail separately. (See "Chest wall diseases and restrictive physiology", section on 'Congenital and childhood abnormalities'.)

-Traumatic and iatrogenic abnormalities of the chest wall – Prior thoracoplasty with rib resection or flail chest due to multiple rib and/or sternal fractures may result in reduced vital capacity; residual volume (RV) is typically preserved (figure 1). (See "Chest wall diseases and restrictive physiology", section on 'Traumatic and iatrogenic processes'.)

•Increased intra-abdominal pressure – Processes that increase intra-abdominal pressure impede diaphragmatic excursion and reduce respiratory system compliance, resulting in reduced lung volumes and lung atelectasis. (See "Chest wall diseases and restrictive physiology", section on 'Abdominal processes'.)

-Central obesity – Patients with central obesity (body mass index [BMI] >30 kg/m²) and an increased waist-to-hip ratio and/or abdominal girth may have restrictive physiology due to increased weight of the chest wall and decreased diaphragmatic excursion. (See "Chest wall diseases and restrictive physiology", section on 'Obesity'.)

Other anesthetic concerns in patients with obesity, including hypoventilation with carbon dioxide retention and obstructive sleep apnea (OSA), are discussed separately. (See "Anesthesia for the patient with obesity" and "Intraoperative management of adults with obstructive sleep apnea".)

-Ascites – Ascites is an accumulation of extravascular fluid within the peritoneum that may cause mild to moderate reductions in functional residual capacity (FRC), total lung capacity (TLC), forced vital capacity (FVC), and expiratory reserve volume (ERV) typically occur. (See "Chest wall diseases and restrictive physiology", section on 'Ascites'.)

-Pregnancy – Although several changes in respiratory mechanics occur in pregnancy, restrictive physiology is relatively rare [5]. Although pregnant women do not have restriction, the reduced FRC and predisposition to atelectasis from intrabdominal pressure reduces the safe apnea time (see "Maternal adaptations to pregnancy: Dyspnea and other physiologic respiratory changes"). Patients with concomitant significant restrictive lung diseases (eg, advanced sarcoidosis or lymphangioleiomyomatosis) may be extremely vulnerable to hypoxemia during anesthesia [6].

History and physical examination

●History – The patient's current functional capacity and issues related to the cause and treatment of restrictive respiratory disease should be assessed. Specific issues include (see "Approach to the adult with interstitial lung disease: Clinical evaluation", section on 'History'):

•Symptom assessment – Current cardiopulmonary symptoms, including respiratory symptoms such as dyspnea, cough, wheezing, or hemoptysis. Additional inquiry regarding symptoms of hypoxemia (eg, dyspnea, morning headaches) and symptoms of hypercapnia (eg, muscle twitching, lethargy, confusion, headache) may be helpful. Patients with significant orthopnea, peripheral edema, skeletal muscle weakness, respiratory muscle weakness, pleuritis, or fever should undergo further evaluation for myocardial or pericardial disease, respiratory muscle weakness, or flareup of the rheumatic or mixed connective tissue disease (table 5).

•Positional intolerance – Activities or positions that worsen symptoms. For example, positional dyspnea may worsen when lying supine in a patient with diaphragm dysfunction, or when lying in right decubitus position in those with significant right-sided pleural disease.

•Tobacco exposure – Current or former tobacco use (eg, pack years, past or anticipated quit date) and efforts directed toward smoking cessation. (See "Smoking or vaping: Perioperative management".)

•Oxygen requirements – Need for oxygen therapy, including current or past oxygen requirements and the frequency and flow rate required for symptom relief.

•Heart failure and pulmonary hypertension – Presence of associated cardiorespiratory conditions, particularly PH with pulmonary artery systolic pressure ≥20 mmHg at rest and right heart failure [7,8]. Significant cardiomyopathy may be present in patients with sarcoidosis. Anesthetic management of patients with right and/or left heart failure is discussed separately. (See "Anesthesia for noncardiac surgery in patients with pulmonary hypertension or right heart failure" and "Intraoperative management for noncardiac surgery in patients with heart failure".)

•Prior anesthesia or hospitalizations – Records of previous hospitalizations, particularly episodes of respiratory failure requiring endotracheal intubation.

●Physical examination – Patients should be evaluated for signs and symptoms of hypoxemia, hypercapnia, increased work of breathing, or difficulty clearing pulmonary sections. Also noted are the body patient's mass index, any external deformities of the chest wall, findings noted on lung auscultation such as presence of crackles, and pulse oximetry values at rest and with exertion. If possible, breathing and presence of dyspnea are assessed in the position required necessary for the planned surgical procedure. (See "Approach to the adult with interstitial lung disease: Clinical evaluation", section on 'Physical examination'.)

Pulmonary function and other tests — In most patients with chronic restrictive respiratory disease, PFTs will have been previously obtained by the patient's primary physician or specialist. Examination of PFTs can clarify the type and severity of respiratory impairment to guide ventilation during surgery, assess the likelihood for prolonged ventilator dependence, and identify patients with severe respiratory impairment so that elective surgery can be reconsidered. (See "Evaluation of perioperative pulmonary risk", section on 'Pulmonary function testing'.)

An updated comprehensive preoperative pulmonary evaluation should be performed for patients with:

●Severe symptoms (ie, dyspnea at rest or with minimal exertion) of uncertain etiology

●Persistently worsened dyspnea after an ILD exacerbation

●Hypoxemia that is new or if unknown etiology (including chart diagnosis of COPD without spirometric confirmation)

●Serum bicarbonate level >33 mEq/L or arterial carbon dioxide tension (PaCO₂) >50 mmHg

●Imaging studies demonstrating new or significantly worsening pulmonary abnormalities

●Suspicion of new or worsening PH (unless recently evaluated)

●Need to predict lung function after planned lung resection

Measurements typically include upright spirometry, measurement of lung volumes, and diffusing capacity for carbon monoxide (DLCO). (See "Overview of pulmonary function testing in adults", section on 'Restrictive ventilatory defect'.)

In selected patients, particularly those undergoing cardiac or thoracic surgery, a six-minute walk test (6MWT), supine spirometry, or a cardiopulmonary exercise test assessing exercise capacity may be obtained to aid in surgical decision-making. (See "Overview of pulmonary function testing in adults", section on 'Other testing'.)

For patients with worsening symptoms, the patient's pulmonologist or a pulmonary consultant may order additional tests such as arterial blood gases or non-contrast high resolution chest computed tomography (CT) scanning.

Optimize pulmonary function and overall condition — Many chronic interstitial lung diseases are progressive, and postponing surgery will not improve perioperative outcomes. However, when possible, postponement of elective surgery is useful to optimize status for selected patients with:

●Acute respiratory conditions – These include active upper respiratory infection or ongoing acute ILD exacerbation. (See "Anesthesia for adults with upper respiratory infection".)

Also, elective surgery is postponed in those with fulminant manifestations of ILD (eg, organizing pneumonia, acute hypersensitivity pneumonitis) or rare acute forms of ILD (acute interstitial pneumonitis) or should avoid surgery when possible until after their condition improves or stabilizes.

●Untreated hypoxemia – Untreated hypoxemia may increase risk for perioperative exacerbation of PH, particularly in a patient who is debilitated due to decreased preoperative activity. A few weeks of oxygen therapy may improve functional and cardiac status. (See "Long-term supplemental oxygen therapy".)

●Inactive or frail patients – Pulmonary rehabilitation may be helpful in some patients with ILD to alleviate dyspnea and improve exercise capacity and quality of life [3]. (See "Pulmonary rehabilitation".)

●Current tobacco-users – Preoperative smoking cessation reduces the risk of postoperative pulmonary complications, particularly in patients with markedly reduced baseline functional capacity [9] (see "Evaluation of perioperative pulmonary risk", section on 'Smoking'). Although optimal timing for cessation is at least eight weeks prior to surgery, some benefits are achieved in as little as two days (eg, decreased carboxyhemoglobin levels, elimination of nicotine effects, and improved mucociliary clearance).

Detailed discussions regarding strategies to implement smoking cessation are available in other topics:

•(See "Smoking or vaping: Perioperative management", section on 'Smoking cessation'.)

•(See "Strategies to reduce postoperative pulmonary complications in adults", section on 'Smoking cessation'.)

●Other patients with exposure-related disease – Patients with recently diagnosed restrictive disease associated with an exposure (eg, hypersensitivity pneumonitis, drug-induced pneumonitis, respiratory bronchiolitis ILD) may improve after avoiding exposure for days or weeks, with or without additional anti-inflammatory therapies. (See 'Overview of pathologic processes causing restrictive lung disease' above.)

●Patients starting anti-inflammatory treatments – For certain ILDs typically responsive to anti-inflammatory therapy (eg, organizing pneumonia, active sarcoidosis), pulmonary function may improve significantly over the first several weeks of treatment. (See 'Overview of pathologic processes causing restrictive lung disease' above.)

●Patients starting antifibrotic therapy – For patients with IPF, antifibrotic therapy has been shown to improve mortality and decrease rates of acute exacerbation [10-14]. Limited observational data also suggest that IPF patients receiving antifibrotic therapy prior to general anesthesia may have decreased risk of postoperative exacerbation [15,16].

●Obesity – For patients with obesity, weight reduction prior to elective surgery may improve respiratory mechanics, as well as minimize risk for sleep apnea. (See "Obesity in adults: Overview of management", section on 'Importance of weight loss'.)

●Pleural effusion or ascites – Patients with restrictive physiology due to large pleural effusions or ascites may benefit from fluid drainage before surgery.

●End-stage lung disease – For patients with poor prognosis due to severe restrictive respiratory impairment, the risks and benefits of surgical intervention must be weighed very carefully. In some cases, palliative care consultation may be appropriate. (See "Palliative care for adults with nonmalignant chronic lung disease".)

INTRAOPERATIVE ANESTHETIC MANAGEMENT — Selection of anesthetic techniques and intraoperative anesthetic management of a patient with chronic restrictive respiratory disease depends on the patient's baseline disease (eg, etiology of disease, severity, functional status) and the planned surgical procedure and approach.

Positioning — Surgical positioning during general anesthesia and mechanical ventilation has significant physiologic effects on ventilation, pulmonary perfusion, and intrathoracic pressure. These physiologic effects are often exaggerated in patients with restrictive lung disease, causing inadequate tissue perfusion that may necessitate alternative positioning approaches. (See "Patient positioning for surgery and anesthesia in adults", section on 'General considerations'.)

Specific position-related concerns include:

●Supine position – The supine position is associated with a marked reduction in functional residual capacity (FRC) that is further reduced during general anesthesia [17,18]. Lung compliance may be reduced with resultant airway closure, atelectasis, and ventilation/perfusion (V/Q) mismatch. Changing position from supine to semi-recumbent (30 degrees head-up) increases lung volumes, but may not always improve oxygenation [17]. (See "Patient positioning for surgery and anesthesia in adults", section on 'Physiologic effects of supine position'.)

In comparison with the supine position, other positions result in the following changes:

●Lateral decubitus position – The lateral decubitus position results in V/Q mismatch due to gravitational forces, particularly during general anesthesia. Perfusion increases while ventilation decreases in the dependent lung, and perfusion decreases while ventilation increases in the nondependent lung. FRC and lung compliance are reduced [19,20]. (See "Patient positioning for surgery and anesthesia in adults", section on 'Physiologic effects of lateral decubitus positioning'.)

These changes can cause severe impairments in oxygenation in a patient with restrictive lung disease, necessitating an increase in fraction of inspired oxygen (FiO₂). Applying positive end-expiratory pressure (PEEP) may improve oxygenation by reducing atelectasis in the dependent lung areas; however, high levels of PEEP may have adverse hemodynamic effects or predispose to barotrauma [21,22]. V/Q matching may improve with lung isolation during thoracic surgery because ventilation and perfusion are both driven to the dependent lung. (See 'Mechanical ventilation' below.)

●Prone position – Prone positioning causes variable effects on pulmonary and vascular function. Systemic and pulmonary vascular resistances are increased and venous return is reduced, particularly if the abdomen is compressed [23]. However, the prone position often has beneficial effects on pulmonary function if abdominal compression can be avoided. These include increased FRC, improved V/Q matching, and improved oxygenation (figure 2 and table 6) [24]. (See "Patient positioning for surgery and anesthesia in adults", section on 'Physiologic effects of prone positioning' and "Prone ventilation for adult patients with acute respiratory distress syndrome", section on 'Physiologic effects on oxygenation'.)

●Sitting position – The sitting position results in low intrathoracic pressure and optimal respiratory mechanics during mechanical ventilation. Compared with supine, lateral, and prone positions, FRC and lung compliance increase in the sitting position because the abdominal contents fall away from the diaphragm [24]. The ultimate effect on oxygenation depends also on cardiac output, which tends to fall in the sitting position, particularly in hypovolemic patients [25]. (See "Patient positioning for surgery and anesthesia in adults", section on 'Physiologic effects of sitting position'.)

●Trendelenburg position – The Trendelenburg position is associated with increased venous return and central blood volume, resulting in increased mean arterial pressure. Cephalad movement of the abdominal viscera against the diaphragm decreases FRC and pulmonary compliance, which can lead to atelectasis.

●Reverse Trendelenburg position – The head-up tilt, or reverse Trendelenburg position, causes pooling of blood in the lower extremities and abdominal vasculature. The reduction in central blood volume and venous return leads to decreases in stroke volume and cardiac output. However, the reverse Trendelenburg position relieves pressure from the abdominal contents on the diaphragm and chest wall, and this results in increased FRC and pulmonary compliance.

●Lithotomy position – The lithotomy position is often associated with minor transient increases in venous return. Cephalad displacement of the diaphragm might result in decreased FRC and pulmonary compliance.

Monitored anesthesia care — For appropriately-selected patients and surgical procedures, monitored anesthesia care (MAC) with a conscious patient receiving only minimal sedation has advantages compared with other types of anesthesia. This technique allows a faster recovery time and reduced risk of pulmonary complications compared with general anesthesia. (See "Monitored anesthesia care in adults", section on 'Appropriateness of monitored anesthesia care'.)

However, it is important to avoid unintentional over-sedation, which can reduce cerebral and mechanical pulmonary responsiveness to hypercapnia and hypoxemia, as well as decrease tidal volume. The consequences of these effects are exacerbated by underlying restrictive respiratory impairment [26]. Therefore, we select sedative and/or analgesic agents that are short-acting or have minimal or rapidly reversible respiratory depressant effects, and we administer carefully titrated doses of these agents as needed. Titrated infusion of the alpha₂ agonist dexmedetomidine is a good choice because normal ventilatory responses to hypercapnia are maintained. (See "Monitored anesthesia care in adults", section on 'Drugs used for sedation and analgesia for monitored anesthesia care'.)

The patient's respiratory pattern, end-tidal carbon dioxide (ETCO₂), and peripheral oxygen saturation (SpO₂) should be closely monitored for signs of respiratory decompensation, and urgent airway management and ventilatory support provided if necessary. (See "Monitored anesthesia care in adults", section on 'Monitoring depth of sedation and analgesia'.)

Peripheral nerve blocks — For appropriately-selected patients and surgical procedures, advantages of peripheral nerve blocks include provision of surgical anesthesia as well as for postoperative analgesia, with minimal supplemental sedation or opioid administration. However, certain brachial plexus blocks have inherent risks of respiratory complications that is increased in those with restrictive pulmonary physiology [27]. Immediate recognition and treatment of respiratory decompensation is critically important. (See "Overview of peripheral nerve blocks".)

●Brachial plexus blocks – Specific concerns for brachial plexus blocks are discussed in detail in a separate topic (see "Upper extremity nerve blocks: Techniques"). These include:

•Interscalene block – We avoid interscalene blocks due to association with a 100 percent incidence of phrenic nerve block resulting in hemidiaphragmatic paralysis. Physiologic consequences include a 25 to 30 percent reduction in forced expiratory volume in one second (FEV₁) as well as forced vital capacity (FVC), which can result in dyspnea and/or significant hypoventilation in patients with restrictive disease. There is also a risk of causing a pneumothorax, although less than for supraclavicular blocks. (See "Interscalene block procedure guide", section on 'Clinical implications of anatomy'.)

•Supraclavicular block – Supraclavicular blocks should be used with caution due to an association with pneumothorax (incidence up to 6 percent) that may present with immediate or delayed symptoms. However, this risk is likely reduced with use of ultrasound guidance. (See "Upper extremity nerve blocks: Techniques", section on 'Supraclavicular block'.)

•Infraclavicular block – Infraclavicular blocks are associated with increased risk of pneumothorax due to the proximity of the brachial plexus to the lung apices in this fossa, but they are rarely associated with phrenic nerve blockade. The risk of pneumothorax can be minimized with appropriate procedural technique, as discussed separately. (See "Infraclavicular brachial plexus block procedure guide".)

●Other regional nerve blocks

•Other upper extremity blocks – Axillary block, wrist block, or intercostobrachial nerve block do not increase risk for respiratory complications. Techniques are described in a separate topic. (See "Upper extremity nerve blocks: Techniques", section on 'Axillary block' and "Upper extremity nerve blocks: Techniques", section on 'Wrist blocks' and "Upper extremity nerve blocks: Techniques", section on 'Intercostobrachial nerve block'.)

•Lower extremity blocks – These do not increase the risk of respiratory complications. Techniques are described in a separate topic. (See "Lower extremity nerve blocks: Techniques".)

•Thoracic nerve blocks – Thoracic nerve blocks (eg, paravertebral blocks, intercostal nerve blocks, and various fascial plane blocks of the chest wall) may be helpful to reduce pain and splinting in patients having thoracic surgical procedures, and do not increase the risk of respiratory complications. Techniques are described in a separate topic. (See "Thoracic nerve block techniques".)

Neuraxial anesthesia — Similar to peripheral nerve blocks, neuraxial anesthesia (ie, spinal or epidural anesthesia) of the lower body may be advantageous for intraoperative surgical anesthesia as well as for postoperative analgesia, with minimal supplemental sedation or opioid administration. Effects of neuraxial anesthesia on respiratory mechanics depend on the extent of motor blockade. Typically, pulmonary gas exchange is only mildly impaired; thus, arterial oxygenation and carbon dioxide elimination are well maintained [28-30]. Diaphragmatic function is often spared even if a sensory block reaches the cervical segments. However, high neuraxial techniques that include all thoracic and lumbar segments do reduce inspiratory capacity and expiratory reserve volume [31].

In one retrospective study of patients with interstitial lung disease (ILD) undergoing thoracoscopic lung biopsy, 29 patients received general anesthesia while 15 received thoracic epidural anesthesia (TEA) [29]. Eight patients in the general anesthesia group experienced acute worsening of lung function with one perioperative death, while no patient in the TEA group experienced worsened lung function. In addition, operative and recovery times were shorter in the TEA group. No patients with TEA required conversion to general anesthesia [29]. Another retrospective study included 18 patients with ILD having laparoscopic abdominal surgery with TEA (without general anesthesia) [30]. None had an acute pulmonary exacerbation or required conversion to general anesthesia. One patient required conversion to an open abdominal cholecystectomy, but the procedure was completed under epidural anesthesia [30].

General anesthesia — General anesthesia is necessary for many types of surgical procedures (see "Overview of anesthesia", section on 'Types of anesthesia'). Arterial oxygenation is impaired during general anesthesia even in patients with healthy lungs, and more so in those with chronic restrictive respiratory disease and additional comorbidities that impair gas exchange such as tobacco use, abdominal obesity, and pulmonary hypertension (PH) [32,33].

Induction and airway management — We preoxygenate using passive apneic oxygenation administered by nasal cannula at 10 L/minute in addition to 100 percent oxygen administered by facemask. The use of nasal cannula for passive apneic oxygenation during laryngoscopy can prolong the time to desaturation during airway management in patients with poor pulmonary reserve. Alternatively, preoxygenation with high-flow nasal cannula can deliver up to 100 percent humidified and heated oxygen at flow rates of up to 60 L per minute, resulting in a higher arterial oxygen tension (PaO₂) compared with other preoxygenation modalities including low-flow nasal cannula, non-rebreather mask, or non-invasive ventilation [34,35]. Use of high-flow nasal cannula during preoxygenation can significantly increase the acceptable duration of apnea during induction of general anesthesia, and can significantly improve oxygenation during intubation. (See "Airway management for induction of general anesthesia", section on 'Preoxygenation'.)

Induction of general anesthesia in a head-up position (eg, reverse Trendelenburg or semi-recumbent position) rather than the supine position may be helpful in patients with moderate-to-severe restriction or known orthopnea. This positioning can optimize FRC, reduce work of breathing, and preserve lung compliance.

Since extended periods of apnea are poorly tolerated, the airway is rapidly secured immediately after induction to avoid atelectasis and pulmonary shunt, leading to reduced FRC. Administration of intravenous (IV) lidocaine 1 to 1.5 mg/kg one to three minutes before tracheal intubation may decrease airway irritability during laryngoscopy and insertion of an endotracheal tube or laryngeal mask airway. (See "Induction of general anesthesia: Overview", section on 'Intravenous anesthetic induction'.)

If an inhalation anesthetic induction is desired, this can be accomplished with sevoflurane in patients without significant risk factors for pulmonary aspiration. (See "Inhalation anesthetic agents: Clinical effects and uses", section on 'Induction of general anesthesia'.)

An awake intubation technique may be selected in patients with severe restrictive respiratory disease and a potentially difficult airway to avoid a period of apnea with rapid development of hypoxemia during apnea. This option is particularly desirable if mask ventilation is potentially difficult. Detailed discussion of awake intubation techniques is available in a separate topic. (See "Management of the difficult airway for general anesthesia in adults", section on 'Awake intubation'.)

Selection of anesthetic agents — Generally, anesthetic agents are selected based on individual procedure-related considerations. However, long-acting opioids and sedative agents diminish respiratory drive and pose additional risk to patients with restrictive disease during emergence and the postoperative period. Specific considerations for patients with restrictive lung disease include the following:

●Propofol – In hemodynamically stable patients, propofol is typically used for rapid induction and/or ongoing maintenance of general anesthesia because it has bronchodilatory properties associated with decreases in airway resistance. (See "General anesthesia: Intravenous induction agents", section on 'Advantages and beneficial effects'.)

●Ketamine – In hemodynamically unstable patients, ketamine is often used for induction because it increases sympathetic tone and also has bronchodilatory properties. (See "General anesthesia: Intravenous induction agents", section on 'Advantages and beneficial effects'.)

●Opioids – Opioids may be administered to suppress the cough reflex and deepen anesthesia. Short-acting opioids such as remifentanil or fentanyl are preferred to minimize the risk of opioid-induced respiratory depression in the postoperative period (table 7). Opioids with prolonged respiratory depressant effects (eg, morphine, hydromorphone) should be used with utmost caution. (See "Maintenance of general anesthesia: Overview", section on 'Analgesic component: Opioid agents' and "Perioperative uses of intravenous opioids: Specific agents".)

●Dexmedetomidine – Dexmedetomidine is often selected as an adjunct agent during general anesthesia to reduce doses of inhalation or other IV anesthetic agents and to reduce opioid requirements. (See "Maintenance of general anesthesia: Overview", section on 'Dexmedetomidine'.)

●Volatile anesthetics – Most potent volatile inhalation anesthetic agents (eg, sevoflurane, isoflurane) are bronchodilators that decrease airway responsiveness and attenuate bronchospasm. Of the available inhalation anesthetics, sevoflurane has the most pronounced bronchodilatory properties. We typically avoid desflurane in patients with any type of chronic lung disease since high concentrations cause bronchial irritation and may increase airway resistance. (See "Inhalation anesthetic agents: Clinical effects and uses", section on 'Respiratory effects' and "Inhalation anesthetic agents: Clinical effects and uses", section on 'Sevoflurane' and "Inhalation anesthetic agents: Clinical effects and uses", section on 'Desflurane'.)

All volatile inhalation agents progressively reverse hypoxic pulmonary vasoconstriction at higher doses by promoting perfusion of poorly ventilated lung, thereby increasing V/Q mismatch. These effects may worsen intrapulmonary shunting with resultant hypoxemia, necessitating an increase in the FiO₂ and/or small increases in PEEP. (See 'Mechanical ventilation' below.)

All volatile inhalation anesthetics are rapidly eliminated via the lungs. However, patients with diffuse interstitial lung disease who have a large V/Q mismatch have delayed uptake and elimination, particularly with the more soluble inhalation anesthetic agents (eg, isoflurane) [36]. (See "Inhalation anesthetic agents: Properties and delivery", section on 'Respiratory factors'.)

●Nitrous oxide – We typically avoid nitrous oxide (N₂O) in patients with PH due to potential increases in pulmonary vascular resistance (PVR). Also, N₂O should be used with caution in patients with honeycomb cysts due to ILD since this gas diffuses into any air-filled cavity to displace nitrogen, which may result in enlargement or rupture of a cyst and development of tension pneumothorax. (See "Inhalation anesthetic agents: Clinical effects and uses", section on 'Disadvantages and adverse effects'.)

Mechanical ventilation

●General considerations – Goals of intraoperative mechanical ventilation include facilitation of optimal oxygenation and ventilation. Equally important is the need to recognize and minimize the inherent risk of ventilator-induced lung injury since patients with interstitial lung diseases are particularly vulnerable to this complication. (See "Mechanical ventilation during anesthesia in adults", section on 'Lung protective ventilation during anesthesia'.)

Administration of a neuromuscular blocking agent (NMBA) and maintaining adequate anesthetic depth facilitates coordination with ventilator-delivered breaths and minimizes airway pressures. In patients with reversible bronchoconstriction, administration of inhaled bronchodilators may further improve oxygenation and ventilation.

Other measures employed during mechanical ventilation include maintenance of adequate humidification of inspired gases to keep the airways moist, thereby preventing desiccation of respiratory secretions and consequent atelectasis [37]. This can be achieved by placing a heat and moisture exchange filter (HMEF) at the endotracheal tube connection to the anesthesia machine breathing circuit or by using low inspiratory gas flows).

●Ventilator settings

•Tidal volume (TV) – We use low TV (approximately 6 mL/kg) and increase the inspiratory time of the respiratory cycle to an inspiratory to expiratory [I:E] ratio of 1:1 to 2:1 to minimize the risk of high intrathoracic pressures. Patients with restrictive respiratory disease and poor respiratory system compliance are at risk for development of high intrathoracic pressures, particularly when receiving high tidal volumes. These can cause a significant decrease in venous return and cardiac output, resulting in systemic hypotension, as well as barotrauma and volutrauma leading to the development of acute lung injury or acute respiratory distress syndrome. (See "Mechanical ventilation during anesthesia in adults", section on 'Tidal volume' and "Mechanical ventilation during anesthesia in adults", section on 'Inspiratory to expiratory ratio'.)

Respiratory acidosis is a known consequence of low TV ventilation. However, this may be offset by a small increase in respiratory rate (RR), as well as measures to reduce dead space such as shortening the ventilator tubing.

Most patients with restrictive disease have low risk of dynamic hyperinflation during exhalation due to low lung compliance and can be managed with high I:E ratios and higher respiratory rates. Exceptions include patients with concomitant obstructive physiology (eg, those with emphysema and some patients with airway involvement of sarcoidosis).

•Respiratory rate – In general, the RR should be adjusted to maintain PaCO₂ in a range that results in arterial pH 7.35 to 7.45. Patients with chronic respiratory acidosis due to severe restrictive respiratory disease should be maintained close to their baseline PaCO₂. (See "Mechanical ventilation during anesthesia in adults", section on 'Respiratory rate'.)

•Fraction of inspired oxygen – The FiO₂ and ventilator settings should be adjusted to maintain PaO₂ >60 mmHg and/or SpO₂ >90 percent. Hyperoxia (PaO₂ >120 mmHg, SpO₂ of 100 percent) should generally be avoided, as this can lead to increased absorptive atelectasis and may cause some direct pulmonary toxicity. (See "Mechanical ventilation during anesthesia in adults", section on 'Fraction of inspired oxygen' and "Adverse effects of supplemental oxygen".)

However, it is usually appropriate to preoxygenate with 100 percent oxygen before endotracheal intubation (see 'Induction and airway management' above), as well as before other surgical or positional maneuvers that may induce hypoxemia.

•Positive end-expiratory pressure – We initially use a PEEP of 5 cm H₂O in patients with restrictive respiratory disease, and subsequently increase the level of PEEP cautiously up to 10 to 12 cm H₂O if necessary to achieve adequate oxygenation. (See "Positive end-expiratory pressure (PEEP)".)

-Potential beneficial effects – Use of PEEP prevents alveolar collapse and maintains adequate FRC and end-expiratory lung volume recruited during inspiration [38]. Additionally, PEEP can partially re-expand atelectatic lung regions, thereby increasing alveolar ventilation and decreasing the degree of intrapulmonary shunt and V/Q mismatch [39]. However, application of PEEP does not typically result in a proportional increase in arterial oxygenation.

-Potential adverse effects – Higher PEEP levels (eg, >10 to 12 cm H₂O) are more likely to increase intrathoracic plateau pressures with impaired venous return, decreased cardiac output, and hypotension. Also, PEEP sometimes results in redistribution blood flow away from aerated lung toward atelectatic areas, thereby worsening V/Q mismatch and hypoxemia [40]. (See "Mechanical ventilation during anesthesia in adults", section on 'Positive end-expiratory pressure'.)

Emergence and extubation — Preparations for emergence are similar to those for patients without restrictive lung disease. It is particularly important to avoid residual effects of NMBAs or anesthetic agents that would contribute to poor respiratory effort during and after emergence. (See "Emergence from general anesthesia", section on 'Preparations for emergence' and "Emergence from general anesthesia", section on 'Assess and reverse effects of neuromuscular blocking agents'.)

If possible, tracheal extubation should be accomplished in the reverse Trendelenburg position to improve lung compliance and minimize work of breathing. Extubation is considered only when the patient is alert, cooperative, and able to demonstrate adequate ventilatory effort without tachypnea, tachycardia, hypoxemia, hypercapnia, or other signs of respiratory distress (eg, diaphoresis). Understanding baseline respiratory parameters (eg, respiratory rate, oxygenation) may help guide appropriate parameters in patients with more severe restrictive disease. General guidelines indicating a high probability of successful extubation include the following:

●Inspiratory capacity (VC) >15 mL/kg ideal body weight (IBW); however, patients with severe restrictive respiratory diseases may have a significantly lower baseline VC

●PaO₂ >60 mmHg or SpO₂ >90 percent with an FiO₂ <0.5 (FiO₂ <0.6 may be appropriate for patients on >6LPM home oxygen [O₂])

●Negative inspiratory pressure >–20 cm H₂O

●RR <20 breaths/minute, or close to baseline RR

●Normal arterial pH (7.35 to 7.45), if available

MANAGEMENT OF INTRAOPERATIVE COMPLICATIONS

Hypoxemia — Regardless of anesthetic technique, intraoperative hypoxemia is common in patients with chronic restrictive respiratory disease. Prompt identification and treatment of underlying causes of hypoxemia are essential to maintain adequate tissue oxygenation and minimize perioperative morbidity.

●V/Q mismatch and shunt – The most common cause of hypoxemia during general anesthesia is ventilation/perfusion (V/Q) mismatch. Sudden hypoxemia due to V/Q mismatch is usually due to atelectasis, which leads to intrapulmonary shunting that may not respond to an increase in the fraction of inspired oxygen content (FiO₂). In such cases, we typically apply increased positive end-expiratory pressure (PEEP) up to 10 to 12 cm H₂O. (See 'Mechanical ventilation' above.)

Changing positioning or notifying the surgical team of possible direct or indirect compression of the lung may also facilitate improvements in oxygenation. Other causes of inadequate ventilation (eg, mucus plugging or migration of the endotracheal tube into the right or left main-stem bronchus) should also be evaluated and treated.

In severe cases, V/Q mismatch may be improved by administration of an inhaled pulmonary vasodilator (eg, nitric oxide or epoprostenol). These agents result in pulmonary vasodilation in the well-ventilated areas of the lung, facilitating V/Q matching. They are most typically used when there is also concern for residual volume (RV) dysfunction, which can be precipitated by poor oxygenation or ventilation.

●Impaired diffusion – In conditions of impaired diffusion, most frequently seen in patients with significant pulmonary hypertension (PH) and/or severe fibrotic interstitial lung disease, the entire length of the capillary may be required to fully oxygenate capillary blood, even under resting conditions. If the perfusion time and distance is not sufficient to facilitate oxygen equilibrium between the alveolus and capillary, the arterial oxygen content drops. In such patients, increases in heart rate decrease the perfusion time and result in rapid decreases in arterial oxygen tension (PaO₂) [41]. This physiology also results in exertional hypoxemia, which should be noted during the preanesthetic assessment. Most patients with such physiology are receiving supplemental oxygen, and an increase in intraoperative FiO₂ may be necessary. (See 'History and physical examination' above.)

●Decreased mixed venous oxygen – In patients with significant diffusion impairments or intrapulmonary shunting (from atelectasis or severe interstitial lung disease [ILD]), rapid development of hypoxemia can occur due to decreased oxygen content of mixed venous blood. Specific causes include (see "Oxygen delivery and consumption"):

•Decreased oxygen delivery due to decreased cardiac output (eg, hypovolemia)

•Decreased oxygen content in delivered arterial blood (eg, severe anemia)

•Increased oxygen consumption

V/Q mismatching and shunting strongly contribute to decreases in mixed venous oxygen. For example, baseline PaO₂ may be 80 mmHg when mixed venous oxygen tension (PvO₂) is 50 mmHg. However, if PvO₂ is suddenly decreased to 20 mmHg due to a decrease in cardiac output, the PaO₂ would decrease to 40 mmHg without any change in the degree of V/Q mismatch or shunt.

●Pneumothorax or pulmonary embolism – Rarely, pneumothorax or pulmonary embolism may occur, causing sudden hypoxemia and severe hypotension. Emergency treatment is described in a separate topic. (See "Intraoperative management of shock in adults", section on 'Tension pneumothorax or hemothorax' and "Intraoperative management of shock in adults", section on 'Pulmonary embolism'.)

Arrhythmias — Patients with severe chronic restrictive respiratory disease are particularly vulnerable to atrial and ventricular arrhythmias due to hypoxemia and/or hypercapnia, acid-base disturbances, increased sympathetic nervous system activity, medication effects (eg, beta₂-agonists), and the frequent presence of comorbid conditions such as ischemic heart disease or PH with cor pulmonale [7]. Prompt diagnosis of the arrhythmia and correction of the underlying cause are necessary, and antiarrhythmic agents may be indicated. Management of specific arrhythmias is discussed separately. (See "Arrhythmias during anesthesia".)

Exacerbation of pulmonary hypertension — For patients with chronic PH and cor pulmonale, factors that increase pulmonary vascular resistance (PVR) should be avoided. These include hypoxemia, hypercapnia, acidosis, hyperthermia, nitrous oxide, and hyperinflation of the lungs (ie high PEEP or large tidal volumes) [7].

Patients with severe ILD often require increases in PEEP to maintain adequate oxygenation, but treatment can be particularly challenging if concomitant right heart failure is present [7]. For example, a patient with idiopathic pulmonary fibrosis (IPF) and secondary PH who is ventilated with low lung volumes might require relatively higher PEEP to achieve adequate tissue oxygenation. However, the resultant increase in intrathoracic pressures can increase PVR and right ventricular strain, and may also decrease venous return to the right heart, thereby decreasing preload and further worsening right ventricular failure. These effects can result in significant systemic hypotension requiring vasopressor and inotropic support. In such cases, a pulmonary artery catheter may be inserted to guide therapy. Details regarding treatment for suspected acute worsening of PH is described in a separate topic. (See "Anesthesia for noncardiac surgery in patients with pulmonary hypertension or right heart failure", section on 'Intraoperative management'.)

MANAGEMENT IN THE POST-ANESTHESIA CARE UNIT — Patients with chronic restrictive respiratory disease should be closely monitored in the immediate postoperative period for any signs of respiratory decompensation. (See "Respiratory problems in the post-anesthesia care unit (PACU)".)

Optimal recovery is facilitated by (see "Strategies to reduce postoperative pulmonary complications in adults", section on 'Postoperative strategies'):

●Ensuring adequate postoperative analgesia – Adequate analgesia facilitates the patient's ability to cough and take a deep breath, thereby minimizing development of pain-associated splinting, inhibition of coughing, and development of atelectasis.

●Preventing of atelectasis – Deep breathing, lung expansion, coughing, and early mobilization are promoted to prevent atelectasis, an important cause of hypoxemia in the early postoperative period [42].

●Using high flow oxygen or noninvasive ventilatory support as needed – Providing continuous positive airway pressure (CPAP) is more effective than increasing fraction of inspired oxygen (FiO₂) for treatment of hypoxemia [43], particularly when the cause is extrinsic compression (atelectasis) or pulmonary edema. If necessary, a trial of high-flow oxygen delivered via nasal cannulae (HFNC) is used to decrease work of breathing, reduce respiratory rate, and decrease risk of requiring reintubation. Patients should be monitored closely on non-invasive positive pressure support to avoid aspiration or very high work of breathing, either of which may result in lung injury. Rarely, postoperative mechanical ventilation is necessary in a patient with severe pulmonary dysfunction. (See "Respiratory problems in the post-anesthesia care unit (PACU)".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pulmonary function testing" and "Society guideline links: Interstitial lung disease" and "Society guideline links: Pulmonary hypertension in adults" and "Society guideline links: Idiopathic scoliosis in adolescents".)

SUMMARY AND RECOMMENDATIONS

●Preanesthetic assessment and management

•Assessment – Restrictive respiratory diseases are pathological processes causing a restrictive pattern on pulmonary function tests (ie, reduced total lung capacity [TLC] and vital capacity [VC]), decreased pulmonary compliance, and preservation of expiratory airflow). Severity of lung disease and presence of comorbid conditions such as pulmonary hypertension [PH], obstructive sleep apnea [OSA], chronic obstructive pulmonary disease [COPD], cardiomyopathy, rheumatic diseases, or obesity should be determined. (See 'Preanesthetic assessment' above and 'History and physical examination' above and 'Pulmonary function and other tests' above.)

•Optimize preoperative condition – Goals include working with the patient's pulmonary specialist to optimize pulmonary and overall condition. Elective surgery should be postponed in patients with active upper respiratory infection, acute interstitial lung disease (ILD) exacerbation, or fulminant presentations of ILD. (See 'Optimize pulmonary function and overall condition' above.)

●Intraoperative positioning – Surgical positioning has significant physiologic effects on ventilation, pulmonary perfusion, and intrathoracic pressure, as noted above. (See 'Positioning' above.)

●Monitored anesthesia care (MAC) – Advantages of MAC with minimal sedation include faster recovery time and reduced risk of pulmonary complications compared with general anesthesia. Avoid unintentional over-sedation by carefully titrating doses of short-acting agents as necessary. Closely monitor respiratory pattern, end-tidal carbon dioxide (ETCO₂), and peripheral oxygen saturation (SpO₂) for signs of respiratory decompensation. (See 'Monitored anesthesia care' above.)

●Peripheral nerve blocks – Advantages of peripheral nerve blocks include provision of surgical anesthesia with minimal sedation, as well as postoperative analgesia. However, some brachial plexus blocks (interscalene, supraclavicular, infraclavicular) are avoided or used cautiously due to inherent risks of phrenic nerve block or pneumothorax. (See 'Peripheral nerve blocks' above.)

●Neuraxial anesthesia – Advantages of spinal or epidural anesthesia include provision of surgical anesthesia for the lower body as well as postoperative analgesia, typically with only mildly impaired pulmonary gas exchange. Although high neuraxial techniques that include all thoracic and lumbar segments reduce inspiratory capacity and expiratory reserve volume, diaphragmatic function is usually spared. (See 'Neuraxial anesthesia' above.)

●General anesthesia – General anesthesia is necessary for many types of surgical procedures. Impairment of arterial oxygenation during general anesthesia is worse in patients with restrictive respiratory disease compared with other patients. (See 'General anesthesia' above.)

•Induction and airway management – We preoxygenate using passive apneic oxygenation administered by nasal cannula at 10 L/minute in addition to 100 percent oxygen by facemask. (See "Airway management for induction of general anesthesia", section on 'Preoxygenation'.)

Induction in the head-up position (eg, reverse Trendelenburg or semi-recumbent position) may be advantageous compared to the supine position to optimize functional residual capacity (FRC), improve lung compliance, reduce work of breathing, and minimize atelectasis. Since extended periods of apnea are poorly tolerated, the airway is rapidly secured immediately after induction. (See 'Induction and airway management' above.)

•Selection of anesthetic agents – Anesthetic agents are selected based on individual procedure-related considerations. However, long-acting opioids and sedative agents should be avoided to optimize respiratory drive during emergence and the postoperative period. (See 'Selection of anesthetic agents' above.)

•Management of mechanical ventilation – Typical settings for mechanical ventilation in patients with restrictive diseases include (see 'Mechanical ventilation' above):

-Low tidal volume (TV; approximately 6 mL/kg), with inspiratory to expiratory [I:E] ratio 1:1 to 2:1 to minimize intrathoracic pressures

-Fraction of inspired oxygen (FiO₂) to maintain arterial oxygen tension (PaO₂) >60 mmHg and/or peripheral oxygen saturation (SpO₂) >90 percent. Hyperoxia should be avoided except in preparation for apnea or adverse positioning.

-Respiratory rate (RR) to maintain arterial carbon dioxide tension (PaCO₂) and arterial pH 7.35 to 7.45 (or close to baseline PaCO₂ in patients with chronic respiratory acidosis)

-Initial positive end-expiratory pressure (PEEP) of 5 cm H₂O. We avoid high levels of PEEP (>10 to 12 cm H₂O) due to adverse hemodynamic effects of high intrathoracic pressures and out of concern for barotrauma in those with severe fibrotic or cystic lung disease.

●Emergence and extubation – If possible, tracheal extubation is accomplished in the reverse Trendelenburg position to reduce atelectasis, improve lung compliance, and decrease work of breathing. We proceed with a trial of extubation when the patient is alert and cooperative with the following parameters (see 'Emergence and extubation' above):

•Inspiratory capacity (VC) >15 mL/kg ideal body weight (IBW); however, patients with severe restrictive respiratory diseases may have a significantly lower baseline VC

•PaO₂ >60 mmHg or SpO₂ >90 percent with an FiO₂ <0.5

•Negative inspiratory pressure >–20 cm H₂O

•RR <20 breaths/minute, or close to baseline RR

•Normal arterial pH (7.35 to 7.45), if available

●Management of complications – Hypoxemia may occur due to ventilation/perfusion mismatch or intrapulmonary shunting, impaired diffusion, decreased venous oxygenation, pneumothorax, or pulmonary emboli. Other likely complications are arrhythmias or exacerbations of PH. Management is described above. (See 'Management of intraoperative complications' above.)

●Postoperative care – Management in the immediate postoperative period includes (see 'Management in the post-anesthesia care unit' above):

•Close monitoring for signs of respiratory decompensation

•Ensuring adequate analgesia to facilitate coughing and to minimize splinting

•Preventing atelectasis by promoting deep breathing and early mobilization

•If necessary, continuous positive airway pressure (CPAP) or a trial of high-flow oxygen delivered via nasal cannulae (HFNC) is used to decrease work of breathing, reduce respiratory rate, and decrease risk of requiring reintubation. Rarely, postoperative mechanical ventilation is needed.