Version May 2024
INTRODUCTION — Patients with neuromuscular or chest wall disease, or ventilatory pump failure for any reason, can develop severe hypercapnia, difficulty clearing airway secretions with ventilation-perfusion mismatching, and ultimately acute on chronic respiratory failure. Noninvasive ventilatory assistance is usually first needed at night, but, with progressive muscle dysfunction, patients can become dependent on continuous full ventilator setting noninvasive ventilatory support (CNVS) and require the use of mechanical insufflation-exsufflation (MIE) to expel airway secretions during intercurrent respiratory tract infections. Patients with severe dysphagia and aspiration often require MIE many times per day. Indeed, virtually all patients with neuromuscular disorders (NMDs) caused by myopathic or lower motor neuron lesions can be managed noninvasively indefinitely, whereas patients with upper motor neuron (UMN) lesions, such as many of those with bulbar amyotrophic lateral sclerosis, develop stridor and spastic upper airway collapse that can render MIE ineffective [1] and necessitate tracheotomy for continued survival [2,3]. In addition, intubated patients and those dependent on up to continuous tracheostomy mechanical ventilation (CTMV) can be extubated [4] or decannulated to CNVS and MIE [5]. CNVS via active or passive circuits and MIE aid and can substitute for the use of inspiratory and expiratory muscles. In our experience, ventilator-dependent patients can be extubated [4] and decannulated [5] to CNVS and, if their cough flows are ineffective, have their airways cleared and oxygenation maintained using MIE. The latter can also be used to wean intubated patients with UMN disease from ventilatory support.
The use of CNVS, whether via active or passive ventilator circuits, will be reviewed here. Nocturnal ventilatory assistance/support, types of ventilators, and the role of tracheostomy are discussed separately (see "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation").
DEFINITIONS — While the term noninvasive ventilation has come to be synonymous with continuous positive airway pressure and low-span bilevel positive airway pressure (BPAP), the latter is usually used via passive ventilation circuits and nonvented interfaces and used at much less than full ventilatory support settings. It can, however, be used with volume targeting for full ventilatory support. Even so, lung volume recruitment cannot be provided using any pressure settings. The BPAP is counterproductive.
While expiratory positive airway pressure (EPAP)/positive end-expiratory pressure (PEEP) tends to increase arterial oxygen tension for patients with acute respiratory distress syndrome, it does not do so for patients with ventilatory pump failure (VPF). In a study using BPAP for patients with bulbar amyotrophic lateral sclerosis, PEEP increased sympathetic activation and increased arousals due to more leaks and heart rate variability with increased leaks in those with VPF 4 cm H2O [6]. In another study, PEEP also caused a reduction in non-rapid eye movement (REM) stage 2 sleep [7]. Autotriggering associated with the increased leaks due to EPAP and by EPAP/PEEP offsetting the threshold load imposed by intrinsic PEEP was often followed by arousals and predominance of light non-REM sleep while decreasing stage N3 sleep as well [6]. Nonrespiratory effects of EPAP include increasing or decreasing transvascular fluid flux that affects alveolar and extra-alveolar vessels, most often increasing lung water. Also affected by EPAP were alveolar epithelial and pulmonary endothelial permeability, the bronchial circulation, cardiac function, regional distribution of systemic perfusion, and central nervous system pressure and blood flow. Induced mediastinal pressures can also be associated with left ventricular dysfunction. EPAP/PEEP induced increases in right atrial pressures, and reduced venous return affects cerebral venous pressures, affects renal blood flow, increases renal venous pressures, and decreases urine output and sodium excretion [8].
INDICATIONS — Symptomatic respiratory muscle dysfunction, often with alveolar hypoventilation, is the primary indication for ongoing nocturnal ventilatory assistance [9]. Typical symptoms include fatigue, exertional dyspnea, reduced appetite, inattention, and impaired concentration and memory. Initially, hypoventilation occurs during rapid eye movement sleep and is manifest by oxyhemoglobin desaturation and hypercapnia. Hypoventilation subsequently extends throughout sleep and, eventually, into daytime hours [3,10]. (See "The effect of sleep in patients with neuromuscular and chest wall disorders".)
However, infants with paradoxical breathing, whether hypercapnic or not and irrespective of any apnea-hypopnea indices, require sleep nasal NVS to reverse their paradoxical breathing and ease the symptoms of frequent arousals with flushing, perspiration, and tachypnea and to avoid pectus and other chest wall deformities and to promote lung growth [11].
Symptoms (eg, dyspnea, somnolence, fatigue) and blood gas derangements related to chronic hypoventilation are typically relieved by nocturnal noninvasive positive pressure ventilatory assistance/support. While the effect of limiting the application of NVS to nocturnal-only does not result in markedly prolonged survival [12], clinicians who understand how to accommodate the patient's eventual need for up to continuous NVS (CNVS) report decades of prolonged survival for patients with ventilatory pump failure. As the need for ventilatory support extends into daytime hours and is ultimately needed continuously, the properly equipped and informed patient can use it indefinitely as an alternative to tracheostomy ventilation (picture 1).
TYPES OF INSPIRATORY AIDS — The respiratory muscles can be aided by manually or mechanically applying forces to the body or delivering intermittent pressure to the airway. Some devices assist inspiratory muscles, whereas others facilitate coughing, predominantly by assisting expiratory muscles. Specific types of useful devices include the following [13,14]:
●Devices that apply intermittent pressure changes directly to the airway (eg, mouthpiece and nasal NVS)
●Body ventilators (eg, intermittent abdominal pressure ventilator [IAPV] and chest shell ventilator) that apply positive or negative pressures to the body
●Manual and mechanical exsufflation techniques that apply forces directly to the body to mechanically displace respiratory muscles to increase cough flows (see 'Types of expiratory aids for cough assistance' below)
The most useful of the daytime inspiratory aids are mouthpiece and nasal NVS and the IAPV [15,16]. However, chest shell, and other negative pressure ventilators, can provide a bridge for ventilatory support when extubating or decannulating a ventilator-dependent patient to NVS and MIE. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support".)
Noninvasive ventilatory support via mouthpiece — A convenient method of daytime ventilatory support involves the delivery of volume preset ventilation via a 15 mm angled mouthpiece, a 22 mm mouthpiece, or a wide plastic straw kept adjacent to the mouth for easy access to supplement tidal volumes as needed. Active ventilator circuits on portable ventilators that can be volume preset so that users can retain several consecutively delivered volumes for active lung volume recruitment using assist/control mode NVS without expiratory positive airway pressure. Intermittent mouthpiece NVS has been used in conjunction with nocturnal nasal or lip cover phalange NVS for up to 32 years of continuous NVS (CNVS) for patients with Duchenne muscular dystrophy (DMD), for ambulating patients unable to breathe (picture 2), up to 66 years for post-polio patients, 29 years for patients with Werdnig-Hoffmann disease (spinal muscular atrophy type 1), and 38 years for high-level spinal cord tetraplegia, as well as for other conditions [17-20].
In one report, 108 patients with DMD required CNVS including daytime mouthpiece NVS and nocturnal nasal/oronasal NVS for a mean of 9 years and up to 29 years. Mouthpiece NVS maintained normal alveolar ventilation for many patients with as little as 0 mL of slow vital capacity (VC) [20].
Mouthpiece NVS has also been used nocturnally since 1954 with or without a lip cover phalange and straps to retain the mouthpiece. Interface designs that deliver air via both the mouth and nose can provide closed systems of CNVS with minimal strap/skin pressure (picture 3).
Noninvasive ventilatory support via nasal interface — Nasal NVS is used during daytime hours if neck rotation or lip strength are not adequate for the patient to grab a mouthpiece (picture 4). During periods of nasal congestion, oronasal interface NVS must usually be used. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation".)
Noninvasive ventilatory support via oronasal interfaces — Oronasal interfaces can be used for patients with excessive oral leakage using NVS via mouthpiece/lip cover or nasal interfaces.
Intermittent abdominal pressure ventilation — Intermittent abdominal pressure ventilation is provided by pneumatic intermittent abdominal pressure ventilators (IAPVs) that consist of a wide belt or girdle with an inflatable sac inside it. The sac is cyclically inflated by air delivered from a portable positive pressure ventilator. Sac inflation compresses the abdomen, and the resulting movement of the abdominal contents elevates the diaphragm forcing expiration to a volume below the functional residual capacity. With sac deflation, the diaphragm returns to its resting position and air enters the patient's upper airway. The IAPV is only effective when the patient is in the sitting position or at least over 30° from the horizontal. The patient can add to IAPV-provided volumes with spontaneous tidal volumes or by glossopharyngeal breathing. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support", section on 'Abdominal respirators'.)
Glossopharyngeal breathing — Both inspiratory and, indirectly, expiratory muscle activity can be assisted by glossopharyngeal breathing (GPB) [21]. GPB is described in detail elsewhere. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support", section on 'Glossopharyngeal breathing'.)
Many CNVS-dependent patients can use GPB all day and remain ventilator-free. GPB can also be used to generate volumes for coughing that approach the deep lung volumes achieved by air stacking (2 to 3 L over VC). It can also be used in the event of sudden ventilator failure. Anecdotally, we have had CNVS-dependent patients with no VC use GPB upon wakening to discover that their ventilators were no longer functioning.
Negative pressure ventilation — Negative pressure ventilation was used in the past but is not used at this time. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support", section on 'Negative pressure ventilators'.)
TYPES OF EXPIRATORY AIDS FOR COUGH ASSISTANCE — The ability to generate sufficient expiratory flow for effective coughing is the most important factor permitting use of CNVS indefinitely as an alternative to tracheostomy ventilation [20]. There are both manual and mechanical methods to create effective cough flows.
An effective cough involves a deep inspiration or assisted insufflation, followed by the creation of sufficient thoracoabdominal pressure to generate an explosive decompression and high expiratory flows. Aiding expiratory muscles is required to optimize cough peak flow rates [22].
For patients with vital capacities (VCs) less than 1.5 L, a deep insufflation or air stacking of consecutively delivered volumes of air (active lung volume recruitment [LVR]) should precede cough. A manual resuscitator (eg, Ambu bag) or ventilator can be used to deliver preset volumes of air consecutively for air stacking [22,23]. Volumes are delivered to approach a maximum lung insufflation capacity, that is, until the glottis can hold no additional air. Volume cycling ventilation permits the stacking of air volumes to increase cough peak flows and are, therefore, preferred for assisted and supported ventilation over pressure-cycling, which does not permit air stacking [22].
Manually assisted cough — A forceful manual thrust to the abdomen directed posterior and cephalad manually assists coughing but may not be sufficiently effective in the presence of severe scoliosis or severely impaired bulbar-innervated muscles.
It should also be used cautiously following meals due to the risk of aspiration and the thrusts avoided following abdominal trauma.
Mechanical insufflation-exsufflation — The most effective method for generating effective cough flows for clearing airway debris of patients with ventilatory pump failure (VPF) is the use of MIE. It can be used in combination with the manual thrusts; however, when used via the upper airways at positive and negative pressures of 50 to 60 cm H2O to insufflate then exsufflate the lungs, concomitant thrusts usually do not further increase the exsufflation flows (MIE-EF). Following insufflation, the exsufflation occurs in 0.02 seconds to generate approximately 10 L per second of MIE-EF. The goal is to fully inflate then fully empty the lungs in four to six seconds to clear airway debris, while avoiding both hypo- and hyperventilation.
The MIE can also be used for passive LVR for patients unable to air stack such as whenever glottis strength is inadequate to hold consecutively delivered air volumes. Thus, MIE can also be used for LVR as well as to increase cough flows to clear airway mucus [3]. When mucus plugs cause oxyhemoglobin desaturation, clearance of the secretions by MIE can increase VC and oxyhemoglobin saturation (SpO2). In one study, a 55 percent increase in VC was noted following MIE in congested patients with neuromuscular conditions [24]. In another study, MIE improved VC by 15 to 50 percent and normalized pulse SpO2 in patients with neuromuscular disease who were in acute respiratory failure [25]. When MIE is applied through translaryngeal or tracheostomy tubes, it must be used at 60 to 70 cm H2O pressure because of the pressure drop off across the narrow gauge tubes. Its use via invasive tubes can eliminate the need for deep airway suctioning over which it is greatly preferred by patients and can return ambient air oxyhemoglobin saturation to normal in preparation for successful extubation or decannulation [3,5,26]. No serious complications have been reported to result from the use of MIE for patients with VPF [14,27].
Meta-analyses do not report MIE efficacy for patients, and controlled studies using a placebo are not ethical [28]. However, limited data support its use when adequate pressure is used. Older studies that used pressures of 54.1 cm H2O used for MIE suggest benefit [29,30] and similar success using similar pressures has been reported for successful extubations and decannulations of ventilator-dependent patients with VPF [4,5]. In our opinion, for success, MIE must be used at effective settings and regimens.
PATIENT SELECTION — Patients with the diagnoses listed in the table (table 1) are often candidates for the use of NVS/continuous NVS (CNVS) and MIE. Ventilatory support either in the acute setting or on a long-term basis can usually be managed by up to CNVS as an alternative to endotracheal intubation or tracheostomy if the following criteria are met:
●The patient is mentally competent, cooperative, and not using heavy sedation or opiates.
●Full ventilatory support settings and MIE, and subsequently CNVS, can return and/or maintain ambient air oxygen saturation over 94 percent. Supplemental oxygen depresses ventilatory drive, exacerbating hypercapnia and rendering the pulse oximeter useless for monitoring decreases in alveolar ventilation and increasing airway congestion, both of which can cause oxyhemoglobin saturation to decrease below 95 percent. Supplemental oxygen is both unnecessary in the absence of severe intrinsic lung disease and potentially harmful [31].
●There is sufficient upper airway patency for MIE to be effective in expelling airway secretions to maintain normal room air oxyhemoglobin saturation, that is, MIE-exsufflation flows over approximately 150 to 200 L/minute [32]. This is invariably the case, except for upper motor neuron bulbar muscle impairment or other causes of irreversible upper airway obstruction.
●There is no significant risk of substance abuse or uncontrollable seizures.
PRACTICAL ASPECTS — Patients with neuromuscular and chest wall disease usually tolerate alveolar hypoventilation until acute respiratory distress is provoked by an otherwise benign upper respiratory tract infection or, possibly, by an elective surgical procedure requiring general anesthesia. Ventilator-free breathing may or may not be possible during or following the acute episode.
To avoid the need for intubation, and to permit successful extubation should intubation be required, patients with ventilatory pump failure (VPF) and diminished vital capacity (VC) should be trained in NVS and MIE before any such episode occurs. This is particularly important once assisted and unassisted cough peak flows are less than 270 to 300 L/minute [33]. The NVS and MIE may need to be used aggressively, NVS continuously and MIE up to every 15 to 30 minutes, around the clock if necessary, to maintain oxyhemoglobin saturation (SpO2) over 94 percent until it remains normal without them. Thus, home monitoring of patients requiring daytime NVS and MIE should include monitoring of pulse oxyhemoglobin saturation during intercurrent respiratory tract infections.
●Pulse oxyhemoglobin saturation – Ambient air SpO2 monitoring is useful to gauge the extent of diurnal or nocturnal hypoventilation, airway congestion, and any possible intrinsic lung disease. An oximeter that can average data hourly during nocturnal monitoring can be useful to quantitate the efficacy of continuous NVS (CNVS) during sleep [3,15].
Patient monitoring also should include regular clinic evaluations of the following:
●VC – VC is measured in sitting and supine positions and with thoracolumbar bracing on and off (if applicable).
●Maximum insufflation capacity (MIC) – The MIC represents the maximum quantity of air that the patient can hold with a closed glottis by air stacking of consecutively delivered air volumes, or by glossopharyngeal breathing. The greater the MIC, the greater the cough peak flow rates and the potential to increase voice volume and maintain pulmonary compliance (by decreasing microatelectasis and maintaining or increasing lung volume and chest wall compliance).
●Capnography and transcutaneous carbon dioxide monitoring is useful for demonstrating diurnal and nocturnal hypercapnia. Daytime hypercapnia (>44 mmHg) can signal severe sleep hypercapnia and oxyhemoglobin desaturation below 95 percent.
●Cough peak flow rates – Cough peak flow rates, both unassisted and assisted by air stacking to deep lung insufflation followed by abdominal thrust, are measured using a peak flow meter (eg, Assess peak flow meter) or any digital spirometer that measures expiratory flow. Effective rates range from 300 to 1200 L/minute [34].
Preventing pneumonia — The risk of developing pneumonia during an upper respiratory tract infection is inversely related to cough peak flow rates and the ability to use manually assisted coughing and MIE.
●Patients are at increased risk for developing pneumonia during upper respiratory tract infections when cough peak flow rates are below 300 L/minute, with risk increasing as a function of decreasing cough flows. When even manually assisted cough flows are less than 160 L/minute, MIE can be vital to cough effectively. (See 'Mechanical insufflation-exsufflation' above.)
●If the VC is relatively preserved, typically 2 L or more, a low cough peak flow rate is indicative of severe bulbar muscle dysfunction with airway obstruction from upper airway closure or other etiology. Although manually assisted coughing and MIE can be helpful, significant benefit is often precluded by inability to maintain upper airway patency in order to achieve the expiratory flows (MIE-EF) necessary to eliminate airway secretions. This happens almost exclusively in patients with upper motor neuron disease, such as with bulbar amyotrophic lateral sclerosis (ALS) or other diseases of the central nervous system (CNS). Interestingly, however, even patients in chronic vegetative states from severe CNS pathology dependent on continuous tracheostomy mechanical ventilation can often wean from ventilator use entirely by frequently using MIE via the tube with the cuff inflated until the baseline oxyhemoglobin saturation is normal [35].
●If the VC is below 40 percent of predicted and assisted cough peak flow rates are below 300 L/minute, the patient is at risk for pneumonia and respiratory failure when VC and cough flows decrease further during upper respiratory tract infections. This can usually be prevented by an effective protocol of CNVS and MIE [20,36].
Protocol — At our institution, patients obtain an oximeter and have rapid access to MIE when their maximum assisted cough peak flows are below 270 to 300 L/minute. Symptomatic patients with diminished VC use NVS for sleep and increase use through the day with advancing muscle weakness and when they are ill. A volume-cycling ventilator is preferred because of the need to air stack for manually assisted coughing, increase voice volume, and maintain lung compliance [3,36].
The patient is instructed to maintain SpO2 always greater than 94 percent without the aid of supplemental oxygen in the home. The patient is also told that a SpO2 below 95 percent can result from hypoventilation, bronchial mucus plugging, or intrinsic lung disease. The last of these results mainly from ineffective airway mucus clearance.
While using NVS, oxyhemoglobin desaturation is usually due to mucus plugging, not hypoventilation. The SpO2 returns to baseline as the airway mucus is eliminated by some combination of assisted coughing and MIE. Properly equipped and instructed patients with MIE very infrequently develop pneumonia or require hospitalization for respiratory management. As an example, our center has 15 adult patients with spinal muscular atrophy type 1 (Werdnig-Hoffman disease), five over 25 years of age, who have been CNVS dependent without tracheostomy tubes since infancy, but only one has been hospitalized and intubated during the last 10 years. All when younger and intubated with little or no spontaneous breathing ability were extubated to CNVS and MIE without resort to tracheotomy (picture 4). As the infections resolve, patients usually wean back to their premorbid NVS regimen. In contrast, such patients who undergo tracheotomy typically remain continuously ventilator dependent indefinitely (CTMV).
Typically, as long-term NVS users become symptomatic from alveolar hypoventilation despite nocturnal use of NVS, they extend NVS use into daytime hours and eventually to CNVS. Two of our three patients with Duchenne muscular dystrophy (DMD) over 50 years of age who have been dependent on CNVS for almost 30 years have never been to a hospital or experienced respiratory failure. The extent of daytime use can be guided by a protocol of oximetry feedback. The patient is provided with a 15 mm angled mouthpiece for convenient daytime ventilatory support. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation".)
Tracheostomy to noninvasive ventilatory support — Patients with VPF who have a tracheostomy for mechanical ventilation are candidates for tube decannulation to up to CNVS if they meet the criteria in the table (table 2). Specifically, patients should have sufficiently intact bulbar musculature to protect their airways, or be maintained in position to drool rather than aspirate, to maintain SpO2 at 95 percent or higher in ambient air with or without ventilator use. This includes patients with spinal cord injury, previous poliomyelitis, spinal muscular atrophy, and most myopathies including DMD. Individuals with nonbulbar ALS and other conditions who undergo tracheostomy during an episode of acute respiratory failure have especially improved quality of life with decannulation and transition to NVS/CNVS and MIE.
The following are key steps in the transition from tracheostomy to noninvasive aids:
●Before decannulation, CNVS should be used via mouthpieces and nasal interfaces with the tube capped and a fenestrated tube in place or with a tracheostomy button placed. Various nasal interfaces should be tried to optimize seal and comfort (picture 5 and picture 6 and picture 7). Note that when used with an active ventilator circuit, one with an exhalation valve, the exhalation ports of these interfaces must be covered or capped.
●NVS may be required continuously (CNVS) but must be used without any supplemental oxygen, yet with oxygen saturation over 94 percent during waking hours.
●Once criteria are met, the tracheostomy tube is removed [5,20,36,37]. A temporary tracheostomy button or, sometimes, use of a cuffless fenestrated tube can be placed in the tracheostomy site to permit the patient to continue to practice NVS without letting the ostomy close and without the partial airway obstruction that would be caused by practicing NVS with the continued presence of a tracheostomy tube. If the patient is an outpatient and using tracheostomy mechanical ventilation, whether part-time or continuously, they should use NVS for a few days before the button or cuffless fenestrated tracheostomy tube is permanently removed and a pressure dressing is placed over the ostomy. If an inpatient, the tube can be left out and the dressing placed and conversion to NVS done in the hospital itself. A tracheostomy button or, at times, use of a cuffless fenestrated tube allows the patient to practice NVS as needed before permanent ostomy closure.
●Regular clearance of airway secretions by manual assisted coughing and MIE via a mouthpiece or oronasal mask continues after decannulation of the trachea and is critical for any oxygen desaturations below 95 percent to return oxygen saturation to normal.
●If a tracheostomy button is used, it is useful to document oxyhemoglobin saturation and carbon dioxide levels during sleep using capnography or transcutaneous carbon dioxide monitoring. Once adequate nocturnal SpO2 is documented, the button can be removed and the tracheostomy site allowed to close [5]. An airtight dressing is applied over the site until it is closed [5]. At our center, we no longer use tracheostomy buttons because, with a comfortable interface, CNVS has always been successful for patients with VPF.
Extubation to CNVS and MIE — Patients are extubated to CNVS to wean rather than weaned to be extubated. When a patient receiving mechanical ventilation via translaryngeal tube is unable to be weaned from ventilatory support, endotracheal tube removal and transition to CNVS and MIE permit extubation without resort to tracheotomy [4]. Upon extubation, the patient inexperienced in NVS first uses nasal CNVS but is then transitioned to mouthpiece and/or nasal NVS, by which they can take fewer and fewer mouthpiece ventilations as tolerated to wean themselves. Patients usually wean back to their prehospitalization regimen, often to nocturnal-only NVS, provided that their VC exceeds 250 mL. Patients with lower VCs usually continue to require ongoing CNVS. No weaning schedule is imposed on the patient, and the anxiety inherent in the "standard" weaning approaches is avoided since patients always receive full alveolar ventilation at physiologic respiratory rates. Patients know that they can take deep assisted breaths anytime they feel the need and can use feedback from pulse oximetry to guide ventilator use [3,4,33,38,39]. (See "Initial weaning strategy in mechanically ventilated adults".)
In one study, 155 of 157 intubated patients who refused tracheostomy and who failed spontaneous breathing trials both before and after extubation were extubated to full ventilator setting CNVS and MIE [4]. Ninety-three who had failed extubations were transferred to our center specifically for extubation to CNVS. All "unweanable" patients, even with no measurable cough flows, were successfully extubated to CNVS. Approximately 80 percent of first extubation attempts were successful, but all were ultimately successful on second or third attempts.
Deflation of cuffs — Cuff deflation is used to allow patients to talk while mechanically ventilated through a tracheostomy tube, to practice NVS for decannulation, and to prevent complications from cuff pressure on the trachea. When deflating a cuff, the ventilator insufflation volume should be increased, often to 1500 mL or more, to compensate for air leakage through the upper airway, or pressure assist control ventilation should be used to compensate for the leak. In general, the delivered volumes are increased until they generate the same positive inspiratory pressures that were generated by the smaller delivered volumes before cuff deflation. The patient is encouraged to learn to control and use the insufflation "leak" of air across the vocal cords for speech. The leak also carries airway debris up to the mouth.
If the leak is inadequate for speech, a cuffless tube can be used and/or the tracheostomy tube downsized. Cuff removal, however, prevents optimal MIE for elimination of airway secretions. In contrast, a wider gauge tube should be placed if there is too much leakage for effective alveolar ventilation, as indicated by decreases in SpO2. In general, patients who can speak with deflated cuffs are strong candidates to have their tracheostomy tubes removed in favor of NVS.
INDICATIONS FOR TRACHEOSTOMY — No extent of inspiratory or expiratory muscle failure or ventilator dependence is, in itself, an indication for tracheotomy. The only indication for tracheostomy in patients with ventilatory pump failure is inability to cooperate with NVS, or upper motor neuron (UMN) disease that causes spasticity, stridor, and inadequate patency of the upper airways to permit MIE or assisted or unassisted coughing, and a persistent decrease in the oxyhemoglobin saturation below 95 percent despite NVS and optimal use of MIE. Generally speaking, this only occurs for patients with advanced UMN bulbar amyotrophic lateral sclerosis (ALS) such that mechanical insufflation-exsufflation flows (MIE-EF) decrease to little more than 100 L/minute [1]. Since many patients with no measurable vital capacity (VC) have depended on and used continuous NVS (CNVS) for decades, tracheotomy is unnecessary for long-term ventilatory support for anyone who is simply too weak to breathe. However, if airway secretions cause chronic congestion that MIE cannot reverse because of UMN disease, whether the patient requires ventilatory assistance/support, a tracheostomy tube can become necessary for survival. It is important to review with patients and caregivers their goals and preferences for ongoing medical care and ventilatory support. However, it should be understood that clinician experience with over 2000 patients using NVS/CNVS (over 109 of our patients are among the 335 CNVS-dependent ALS patients), none of these patients have ever volitionally ceased using CNVS to die or undergo tracheostomy, and few have failed to tolerate nasal NVS [40]. Also, no matter how vehemently patients reject tracheotomy as a future possibility, when intubated and facing death, many if not most of our patients at least change their minds. When patients are told that, if intubated, they can probably be extubated to CNVS and MIE without resort to tracheotomy, they usually accept intubation.
CNVS-dependent patients who require intubation for acute respiratory failure can usually be extubated back to CNVS once their lung disease has cleared [4,38]. Avoidance of tracheostomy eliminates the risk of glottic and subglottic stenosis and other serious and potentially fatal complications of tracheostomy [41]. Long-term tracheostomy tube cuff inflation is also associated with the following problems:
●Increased risk of trachiectasis and tracheal perforation, along with many other potentially deadly complications
●Prevention of effective verbalization
●Impaired swallowing and aspiration from elevation of the larynx and esophageal dysfunction during swallowing and tying down of the strap muscles of the neck [38,42]
PITFALLS — The term noninvasive ventilation has come to be synonymous with continuous positive airway pressure and low spans of bilevel positive airway pressure (BPAP). While the former is useless as a respiratory muscle aid, BPAP assists lung ventilation as a function of the drive pressure (span) being used. To avoid endotracheal intubation, patients with severe respiratory muscle dysfunction often need to use full ventilator setting volume or pressure preset ventilatory support (CNVS), which can be provided by delivering bilevel at spans over 15 cm H2O or by intermittent positive pressure ventilation without expiratory positive airway pressure (EPAP) or positive end-expiratory pressure (PEEP). Since the EPAP is counterproductive for administering ventilatory assistance [43], intermittent positive pressure ventilation without EPAP or PEEP, whether volume or pressure preset, is preferred for these patients. Full-setting CNVS normalizes alveolar ventilation, more fully rests inspiratory muscles, optimizes lung volume recruitment, and augments cough flows. A publication demonstrated for bulbar ALS that any EPAP at all is counterproductive [43]. In fact, bulbar ALS patients on pressure support of 12 cm H2O with no PEEP/EPA had less ventilator autocycling, central sleep apneas, and glottis closure than patients on 5 cm H2O.
Frequently, patients who are able to walk (ie, myotonic dystrophy or kyphoscoliosis) do not use NVS sufficiently during daytime hours to normalize alveolar ventilation. These patients can have repeated respiratory complications until they spend most of their time in wheelchairs, from which they can more conveniently use mouthpiece NVS and CNVS.
The clinician is often tempted to prescribe oxygen therapy. However, if arterial blood gases can be normalized by NVS and MIE, then oxygen therapy is not needed and can be hazardous. When oxygen supplementation is used along with NVS, it decreases the efficiency of nocturnal NVS, increases the risk of pulmonary complications, and exacerbates hypercapnia [31]. Domiciliary supplemental oxygen should not be used for patients with ventilatory pump failure except for those with advanced ALS and upper motor neuron bulbar impairment who need, but refuse, tracheotomy for secretion management and ventilation.
OTHER CONSIDERATIONS — Many of the same general interventions and cautions for patients with primary lung disease are also applicable to patients with ventilatory pump failure (VPF). Patients are cautioned to avoid extremes of temperature; humidity; fatigue; crowded areas; or exposure to respiratory tract pathogens, sedatives, supplemental oxygen, and opiates. Patients should be advised to receive influenza and pneumococcal vaccines. They should also be instructed about using NVS/continuous NVS (CNVS) and MIE in the event of an upper respiratory tract infection or postoperatively for general anesthesia. Diaphragm pacing is ineffective and often harmful for patients with all neuromuscular diseases, including amyotrophic lateral sclerosis [44,45].
Nutrition — Heavy meals should be avoided and obesity prevented or managed. General weight charts are not applicable to these patients. However, a specific weight chart has been developed for patients with Duchenne muscular dystrophy (DMD) [46]. A useful equation for estimating caloric need for DMD patients up to 20 years of age is [47]:
Daily energy intake (Kcal) = 2000 – [age (years) × 50]
As bulbar muscles weaken, these patients must often limit oral intake to high-calorie, thick liquids. While some patients with neuromuscular disease eventually require indwelling gastrostomy tubes for enteral nutrition, this can be greatly delayed by NVS. As a patient's vital capacity decreases, the patient develops tachypnea to 40 to 50 breaths per minute and the patient has only approximately one second to swallow, rendering swallowing unsafe, thereby reducing their appetite; this phenomenon is exacerbated by hypercapnia, which is frequently present. By administering mouthpiece NVS at 1000 to 1500 mL volume, normal minute ventilation can be provided by only grabbing the mouthpiece four or five times a minute, giving patients 10 to 15 seconds to swallow their food [48]. By using NVS during meals and definitely avoiding tracheotomies, only 15 percent of patients with DMD ever require gastrostomy tubes, whereas close to 100 percent using tracheostomy mechanical ventilation have them placed. These tubes, though, when needed, should only be placed under local anesthesia [49].
Physical therapy — Although most patients with VPF who require pulmonary interventions are wheelchair dependent, some who require up to 24-hour ventilatory support can walk. Indeed, some can only walk if using CNVS [50]. Musculotendinous releases and physical and occupational therapy are useful to maintain their orthopedic status and function. In addition, preventing back deformity can permit the use of the intermittent abdominal pressure ventilator and prevent the untoward effects of back deformity on cardiopulmonary and physical functioning [51].
There is no evidence that skeletal muscle exercise improves pulmonary function or prognosis in patients with neuromuscular disease [52]. Activities of daily living can be greatly facilitated by use of a wheelchair, adaptive equipment, and energy conservation. There are a multitude of orthoses including robotic manipulators and other assistive devices for helping the patient with dressing, grooming, personal hygiene, transfers, wheelchair mobility, and, possibly, ambulation. Environmental control systems can permit the severely disabled individual to have access to the telephone and all electrical appliances. Robot arms [52], including the JACO, specifically assist with feeding and other upper limb activities of daily living from motorized wheelchairs and are operated using motorized wheelchair controls, so anyone who can operate a motorized wheelchair can operate the robot arm. Commercial robot arms are programmable, lightweight, and easy to mount on the wheelchair and manipulate.
For many patients, an efficient bowel and bladder management program greatly facilitates the activities of daily living. Constipation, associated with increased gastrointestinal transit time, is common. High fluid intake should be encouraged.
●The most useful single technique for facilitating a bowel movements is using a lift so that the patient's hips are flexed and the buttocks are in a dependent position over a commode. This can decrease post-suppository evacuation waiting time from hours to minutes.
●A condom catheter drainage system can permit patients to urinate without the need for personal assistance or interruption of the activities of daily living.
●Use of mattresses that slowly rotate patients from side to side during sleep can decrease arousals and eliminate the need for assisted turning.
SUMMARY AND RECOMMENDATIONS
●Introduction – In patients with ventilatory pump failure (VPF), respiratory insufficiency is manifest by symptomatic alveolar hypoventilation, difficulty clearing airway secretions, and ventilation-perfusion mismatching and should initially be treated by nocturnal noninvasive ventilatory support (NVS). (See 'Introduction' above.)
●Indications and patient selection – When alveolar hypoventilation extends into the daytime hours, use of NVS is typically extended into daytime hours and eventually becomes continuous (CNVS). Criteria for dependence on CNVS rather than tracheostomy ventilation are discussed above. (See 'Indications' above and 'Patient selection' above.)
●Inspiratory aids – The most practical daytime NVS interface is usually a mouthpiece for NVS. Mouthpiece NVS delivers positive pressure via a 15 mL angled mouthpiece or tygon "straw" kept adjacent to the mouth for easy access. This can augment breaths by volumes >1 L, and the patient can take as much as they want. (See 'Types of inspiratory aids' above.)
In patients who have neck rotation or lip strength inadequate for grabbing a mouthpiece, nasal NVS or the intermittent abdominal pressure ventilator can be used during daytime hours for full ventilatory support.
●Expiratory aids – The ability to generate sufficient expiratory flow for effective coughing is the most important factor permitting the definitive use of NVS. When ventilatory pump dysfunction results in ineffective cough flows, insufflation to increase lung recoil, combined with exsufflation and, at times, abdominal thrusts, can make cough flows more effective, as can the use of mechanical insufflation-exsufflation (MIE). (See 'Types of expiratory aids for cough assistance' above.)
●Practical aspects
•Monitoring – Home monitoring of oxyhemoglobin saturation is needed to assure adequacy of cough and ventilation, especially during upper respiratory infections. (See 'Practical aspects' above.)
•Transitioning from tracheostomy to NVS – Many patients with neuromuscular or chest wall disease who undergo tracheostomy for mechanical ventilation during a respiratory tract infection are candidates for NVS and removal of the tracheostomy tube, if the criteria in the table (table 2) are fulfilled. (See 'Tracheostomy to noninvasive ventilatory support' above.)
●Tracheostomy indications – Since even with unmeasurable vital capacity, patients do not need tracheostomy tubes, the only true indication for tracheostomy for patients with VPF is the decrease in MIE exsufflation flows to approximately 100 L/minute. This indicates inadequate upper airway patency for MIE to effectively expel airway secretions to prevent a decrease in baseline peripheral oxygen saturation below 95 percent. These patients generally have stridor and hyperactive deep tendon reflexes. (See 'Indications for tracheostomy' above.)
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