Noninvasive ventilation in adults with acute respiratory failure: Practical aspects of initiation

INTRODUCTION — Noninvasive ventilation (NIV) refers to the delivery of positive pressure ventilation through a noninvasive interface (eg, nasal mask, face mask, or nasal plugs), rather than an invasive interface (endotracheal tube, tracheostomy).

NIV can be used as ventilatory support for patients with acute or chronic respiratory failure. The practical aspects of initiating NIV in adult patients with acute respiratory failure are discussed here. The data that support the indications for NIV in adults with acute respiratory failure and the use of NIV for the treatment of chronic respiratory failure (eg, neuromuscular disorders, chest wall disease, or obesity hypoventilation syndrome) are described separately. (See "Noninvasive ventilation in adults with acute respiratory failure: Benefits and contraindications" and "Noninvasive ventilatory support and mechanical insufflation-exsufflation for patients with respiratory muscle dysfunction" and "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support" and "Noninvasive positive airway pressure therapy for the obesity hypoventilation syndrome".)

TIMING, SITE, ANCILLARY STAFF — When a trial of NIV is indicated for acute respiratory failure, it should be initiated as soon as possible. Delays in NIV implementation result in deterioration and increase the likelihood of NIV failure [1-3].

Most commonly, NIV is initiated in the emergency department (ED), the intensive care unit, or a specialized respiratory or high/intermediate-care dependency unit. NIV may also be successfully used in the general ward setting [4]. Regardless of the setting, support with appropriate staff knowledgeable and experienced in NIV use is critical to its success. Appropriate use of NIV is often dependent upon bedside experts who ensure the provision of a comfortable snug-fitting interface with minimal air leaks, appropriate initial settings, and patient reassurance with follow-up that comprises frequent check-ins and altered settings, if needed. (See 'Initial monitoring and follow-up' below.)

Although preliminary studies suggest that prehospital NIV administered by emergency medical transport personnel may reduce mortality and/or rates of intubation, data are conflicting and further randomized trials are required before NIV can be routinely recommended in this setting [5-11]. (See "Noninvasive ventilation in adults with acute respiratory failure: Benefits and contraindications", section on 'Acute cardiogenic pulmonary edema (ACPE)'.)

CHOOSING THE COMPONENTS OF NONINVASIVE VENTILATION

Ventilator type — NIV can be delivered via a standard ventilator available in most intensive care units (ICUs) or via a bedside portable ventilator/NIV machines.

In most cases, the ventilator choice is determined by the institutional resources, practices, and policies, the location of the service (eg, ward or ICU), chosen mode of ventilation, and the required fraction of inspired oxygen (FiO₂) [12-14]. Although most newer bedside portable ventilators can deliver several complex modes of ventilation that closely approximate that delivered by standard ICU ventilators, some of the older bedside devices cannot. For patients in whom oxygenation is tenuous, more precise FiO₂ can be delivered via a standard ICU ventilator since many portable ventilators are limited in the flow rate of oxygen that can be delivered. In addition, if hypercapnia is a concern, the dual-limb tubing (separate inspiratory and expiratory tubing) used on standard ventilators and select portable devices minimizes the rebreathing of carbon dioxide (CO₂) compared with single-limb tubing used on most portable devices (see 'Ventilator circuit' below). ICU ventilators also have better monitoring and alarm features (eg, tidal volume, major air leaks, and/or patient disconnection are more readily detected).

Interface (mask) — NIV can be delivered through several types of interfaces. Straps hold the interface in place and should be adjusted to avoid excess pressure on the nose or face. Generally, the straps should be loose enough to allow one or two fingers to pass between the face and the strap.

Common interfaces used for NIV in patients with acute respiratory failure include the following:

●Oronasal mask – This interface includes the nose and mouth, but not the eyes and is sometimes referred to as a face mask or orofacial mask. It is the mask that is most commonly used in patients with acute respiratory failure for the delivery of NIV (picture 1) since they are reasonably well tolerated and eliminate CO₂ effectively, provided the mask fit is good (table 1).

●Nasal mask – A nasal mask covers just the nose (picture 2) and may be an alternative in those who do not tolerate an oronasal mask (eg, if the patient feels an uncomfortable sense of pressure or suffocation). However, NIV delivered by a nasal mask may result in a large air leak through the mouth and interfere with effective ventilation [15]. For those who demonstrate an air leak that interferes with ventilation a chin strap may alleviate the problem.

●Nasal prongs – Nasal prongs (nasal pillows) are inserted into the nares (picture 3 and picture 4) and are an option in patients who are intolerant of an oronasal or nasal mask. A chin strap is also often needed to minimize oral air leak.

●Full face mask – A full face mask includes the eyes, nose, and mouth. Although this mask is superior in terms of maximizing the NIV delivered and minimizing air leaks, it often poorly tolerated.

Although the following interfaces may be used to deliver NIV, they are less commonly used in patients with acute respiratory failure:

●Mouth piece – Mouth pieces are devices that can be inserted into the mouth (picture 5). However, air leak through the nose can occur unless nasal pledgets are used. These are more commonly used in some patients with chronic respiratory failure due to neuromuscular disorders, but they are less practical for patients with acute respiratory failure. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support".)

●Helmet – A helmet interface is also available for NIV (figure 1). The helmet interface allows patients to talk, read, and drink through a straw, while minimizing complications such as skin necrosis, gastric distension, and eye irritation [16-18]. Mechanically, the helmet behaves as a reservoir between the ventilator and the patient. High flow and short inspiratory time are required to pressurize the helmet rapidly. The helmet may also be able to deliver higher levels of positive end-expiratory pressure (PEEP) to improve oxygenation than high flow oxygen delivered via nasal cannulae (HFNC) [19], possibly making it more suitable in those who are PEEP-responsive.

Drawbacks of the helmet device include the accumulation of CO₂ within the helmet (alleviated by increasing gas flow rates), a level of noise exposure sufficiently high to cause hearing damage, more patient-ventilator asynchrony (due to delayed triggering and cycling), and less relief of inspiratory effort [20-23]. In addition, the actual tidal volume delivered via helmet ventilation is unknown, owing to the distensibility of the device.

Helmet use has been proposed for NIV of patients who need droplet precautions (eg, coronavirus disease 2019 [COVID-19]), although this function is unproven [24]. Data have also shown that helmet NIV may reduce the risk of death and intubation in patients with acute hypoxemic respiratory failure when compared with low flow oxygen or NIV via a facemask [25,26]. However, neither mortality nor length of stay were impacted by the use of helmet NIV in a COVID-19 population [27]. Data discussing the potential efficacy of helmet-delivered NIV in patients with acute hypoxemic respiratory failure and acute respiratory distress syndrome (ARDS) in COVID-19 and non-COVID-19 patients are discussed separately. (See "Noninvasive ventilation in adults with acute respiratory failure: Benefits and contraindications", section on 'Hypoxemic nonhypercapnic respiratory failure not due to ACPE' and "Acute respiratory distress syndrome: Ventilator management strategies for adults", section on 'Selecting invasive versus noninvasive ventilation' and "COVID-19: Respiratory care of the nonintubated hypoxemic adult (supplemental oxygen, noninvasive ventilation, and intubation)", section on 'Noninvasive modalities'.)

The efficacy of different interfaces in patients with acute respiratory failure has been examined [28-30]. Three interfaces were compared in a trial that randomly assigned 26 patients with an acute exacerbation of chronic obstructive pulmonary disease (AECOPD) complicated by hypercapnia to receive NIV via full-face mask, nasal mask, or nasal prongs (pillows) [28]. Although the full face mask conferred the greatest physiologic improvement, it was poorly tolerated. Nasal masks or plugs were better tolerated. Similar results were found in an observational study of 36 patients with a do-not-intubate order [29]. Another study that randomly assigned 90 patients to nasal or oronasal mask found that more than one-half of patients initially treated using a nasal mask needed to be changed to an oronasal mask, most often due to a significant air leak through the mouth [30].

Ventilator circuit — Positive pressure and oxygen are delivered via tubing attached to the interface. If a standard mechanical ventilator is used, then high flows up to an FiO₂ of 1 can be effectively delivered, provided air leaks are minimized. However, many portable ventilators can only deliver lower flow (eg, up to 10 or 15 liters of oxygen/minute, although higher flows may be feasible with a helmet interface). Oxygen should be heated and humidified to improve tolerance and prevent mucosal dryness (figure 2), which is a common complication when the duration of NIV is prolonged [31]. For standard ventilators, typical dual-limb circuitry is used (ie, with inspiratory and expiratory tubing) while portable ventilators typically have a single-limb circuit (figure 3). (See "The ventilator circuit".)

INITIAL SETTINGS — There is no universal approach to selecting initial settings for NIV. Selecting appropriate initial settings depends upon the mode selected to deliver NIV, resource availability, clinician and staff expertise, and patient tolerance. In this section, we provide a general guide to selecting initial NIV settings for the commonly used modes in patients with acute respiratory failure. However, one of the key features required for success is adjustment of initial settings and mode (if necessary) to ensure patient comfort and tolerance. This is best achieved at the bedside when experienced staff take the time to provide patient education and reassurance during the initial trial. This individualized approach to initial settings increases the likelihood that a patient will undergo an adequate trial of NIV, thereby ensuring either success or failure. Electronic advisory programs that assist in recommending NIV adjustments are investigational [32].

Commonly used modes — Bilevel NIV (also known as bilevel positive airway pressure [BPAP]) is the most commonly used mode of NIV in patients with acute respiratory failure. BPAP should not be confused with BiPAP; BiPAP refers to a device that provides positive pressure ventilation including BPAP. BPAP is particularly helpful in patients with acute hypercapnic respiratory failure. This includes patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and disorders associated with acute hypoventilation (eg, patients with drug overdose, patients with acute respiratory failure associated with underlying neuromuscular disorders or obesity hypoventilation syndrome [OHS]). Bilevel NIV is also the most commonly used mode in patients with nonhypercapnic hypoxemic acute respiratory failure due to conditions such as pneumonia, early acute respiratory distress syndrome, or asthma.

Continuous positive airway pressure (CPAP) is most often indicated in patients with acute cardiogenic pulmonary edema but bilevel NIV is an appropriate alternative especially when hypercapnia is present or if CPAP fails.

Data that support these indications are discussed in detail separately. (See "Noninvasive ventilation in adults with acute respiratory failure: Benefits and contraindications" and "Treatment of acute decompensated heart failure: Specific therapies", section on 'Supplemental oxygen and assisted ventilation' and "COPD exacerbations: Management", section on 'Ventilatory support'.)

Bilevel noninvasive ventilation — Our suggested protocol for initiating bilevel NIV is outlined in the table (table 2). Bilevel NIV provides inspiratory positive airway pressure (IPAP) and expiratory PAP (EPAP) at two different levels. The difference between IPAP and EPAP ("delta" PAP) determines and directly correlates with the tidal volume delivered. Alveolar ventilation is enhanced by a larger tidal volume (ie, larger "delta" PAP), assuming that the respiratory rate is constant. The patient is spontaneously breathing during bilevel NIV and each breath is supported to the same level.

In general, we suggest the following initial settings:

●Bilevel NIV (BPAP) mode in the spontaneous/timed (S/T) setting with a backup rate of 8 to 12 breaths/minute – Although the spontaneous mode (ie, the patient is supported only during spontaneous breaths) or timed mode (ie, the patient is only supported during timed breaths) can be selected, the S/T setting is most often selected since it ensures that all breaths are supported and that a minimum respiratory rate is provided if the patient hypoventilates for whatever reason.

●IPAP 8 to 12 cm H₂O – The IPAP may be titrated upward as tolerated, usually in increments of 2 cm H₂O, to a maximum of 20 cm H₂O. Close attention needs to be paid during titration looking for improved dyspnea, decreased respiratory rate, increased tidal volume and minute ventilation, and good patient-ventilator synchrony. An adequate tidal volume that meets the patient’s needs should decrease the work of breathing and also improve alveolar ventilation, thereby treating acute hypercapnia.

●EPAP 3 to 5 cm H₂O – If oxygenation remains inadequate, the EPAP may also be increased minimally (eg, up to 10 cm H₂O) but clinicians should be aware that this maneuver may decrease the delivered tidal volume.

●Fraction of inspired oxygen (FiO₂) as needed to keep peripheral O₂ saturation (SpO₂) >90 percent – The target oxygenation is determined by the underlying disorder. Useful targets are discussed separately. (See "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Fraction of inspired oxygen'.)

A similar protocol for bilevel NIV and other forms of NIV used in patients with OHS who have acute hypercapnia are described separately. (See "Noninvasive positive airway pressure therapy for the obesity hypoventilation syndrome", section on 'Patients with acute hypercapnic respiratory failure and OHS'.)

The physiology of BPAP is discussed in more detail separately. (See "Modes of mechanical ventilation", section on 'Bilevel positive airway pressure'.)

Continuous positive airway pressure (CPAP) — CPAP refers to the delivery of a continuous level of positive airway pressure throughout the respiratory cycle. No additional pressure above the level of CPAP is provided, and patients must initiate all breaths. Although the spontaneous tidal volume is augmented with CPAP, the tidal volume cannot be titrated as effectively as bilevel NIV; thus it is not the optimal mode for treating disorders that require increased alveolar ventilation (ie, disorders associated with acute hypercapnia). However, since CPAP is functionally similar to positive end-expiratory pressure (PEEP), it is typically more effective at improving oxygenation than ventilation. (See "Modes of mechanical ventilation", section on 'Continuous positive airway pressure' and "Positive end-expiratory pressure (PEEP)".)

In general, we suggest the following initial settings:

●Mode: CPAP

●CPAP level: 5 to 8 cm H₂O

●FiO₂: as needed to keep SpO₂ >90 percent (target range is variable according to the underlying disorder) (see "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Fraction of inspired oxygen')

CPAP may be titrated up to 20 cm H₂O as tolerated to achieve improvement of dyspnea and decreased respiratory rate. Although higher pressures up to 25 cm H₂O may be attempted, they are generally poorly tolerated and not every CPAP device can achieve this pressure.

Uncommon modes — Volume-limited modes and pressure support ventilation (PSV) may be delivered noninvasively. In general, their use is limited to patients with specific requirements or poor tolerance of BPAP or CPAP. However, not all portable NIV ventilators have these modes. So, if volume-limited or pressure supported ventilation is required, switching to a standard ventilator may be necessary.

Volume-limited ventilation in the assist controlled mode (ACVC) — ACVC is chosen when patients need a "guaranteed" tidal volume or minimal minute ventilation. Initial settings are similar to those on a standard ventilator, the details of which are provided separately (table 3). (See "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Volume-limited assist control ventilation'.)

Pressure support ventilation — PSV is chosen when patient comfort and synchrony need to be maximized (table 3). Initial settings and titration are similar to those for bilevel NIV (ie, inspiratory support 8 to 12 cm H₂O [titration to a maximum of 20 cm H₂O] and PEEP 3 to 5 cm H₂O with titration to a maximum of 10 cm H₂O). (See 'Bilevel noninvasive ventilation' above and "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Others'.)

Rarely used modes — Controlled mechanical ventilation, intermittent mandatory ventilation (IMV), synchronized IMV (SIMV), pressure controlled ventilation, proportional assist ventilation, and neurally adjusted ventilatory assist (NAVA) are rarely used during NIV. Observational data suggest no difference between NIV-pressure support compared with NAVA-NIV [33]. Descriptions of these modes are described separately and may need a standard ICU ventilator for delivery. (See "Modes of mechanical ventilation".)

INITIAL MONITORING AND FOLLOW-UP — After NIV is initiated, the patient should be observed closely for the first few minutes to troubleshoot any initial problems [34] (see 'Trouble shooting dyssynchrony' below). Once the patient is comfortable, vital signs, oxygenation, and mental status are observed for the next one to two hours in a closely monitored setting (see 'Trial duration and reassessment' below). At that point, we typically re-evaluate the patient clinically and obtain arterial blood gases. When the patient demonstrates improvement in clinical signs and symptoms and gas exchange, we typically persist with NIV (see 'Trial success' below). However, if they do not improve or show signs of deterioration at any time during the trial, NIV should be abandoned and the patient promptly intubated. (See 'Trial failure' below.)

Trouble shooting dyssynchrony — Many patients do not initially tolerate NIV due to patient discomfort or ventilator dyssynchrony (ie, the phases of ventilator breath do not match that of the patient) [35,36]. Ventilator dyssynchrony may be due to one or more issues including auto-positive end-expiratory pressure (auto-PEEP), reduced flow due to an interface leak, or discomfort and anxiety. (See "Acute respiratory distress syndrome: Ventilator management strategies for adults", section on 'Treat dyssynchrony'.)

Management involves treating the underlying reason(s). For example:

●Auto-PEEP should be treated (if present) – Depending on the ventilator used, this may involve reduction in respiratory rate and/or tidal volume, raising the inspiratory flow rate, treating the underlying airflow obstruction, when present, and the application of extrinsic PEEP. (See "Invasive mechanical ventilation in acute respiratory failure complicating chronic obstructive pulmonary disease", section on 'Dynamic hyperinflation'.)

●Reducing interface leak – A mask leak can increase the time required for the ventilator to achieve its pressure target, prolonging inspiration and causing discomfort. Tightening the straps or changing the mask is typically the first maneuver but, in some cases, changing the mode of ventilation may be needed. For example, pressure-regulated volume-controlled ventilation (rather than flow-limited) may help, although only select standard ventilators are typically capable of delivering time-limited ventilatory modes (table 3) [37]. (See "Modes of mechanical ventilation", section on 'Pressure-limited ventilation'.)

●Improving patient comfort and reducing anxiety – For many patients, careful explanation and reassurance help alleviate fears and anxieties associated with NIV. For ill-fitting masks or local discomfort associated with the interface, switching to an alternate interface may improve comfort and tolerance. For example, patients who feel a sense of pressure or suffocation with an oronasal mask may do better on a nasal mask or pillows with or without chin straps. When these simple adjustments fail, lowering the settings or changing the mode or may help improve tolerance. Sedation is rarely needed. (See 'Sedation' below.)

When a change in mode is desired for comfort or dyssynchrony, we prefer pressure support ventilation (PSV). PSV allows the patient to trigger each breath and independently regulate the depth and pattern of breathing. It is reasonable to expect that bilevel NIV provides a similar level of comfort, although this has not been studied. Proportional assist ventilation (PAV) or neurally adjusted ventilatory assist (NAVA) may be helpful in patients who do not tolerate PSV or bilevel NIV. PAV has the advantage of having an inspiratory flow and delivered volume that is proportional to the patient's effort. Cessation of inspiration is determined entirely by the patient, allowing the patient to control the entire respiratory cycle [38]. Randomized trials that compared PAV with PSV in patients with acute respiratory failure found that PAV was more comfortable and better tolerated than PSV [39-41]. However, there was no difference in mortality or intubation rates, and experience with PAV as a mode of ventilation is limited. Other retrospective studies suggest minimal differences between PSV and NAVA, although one suggested that PSV may be superior to NAVA [33,42].

Trial duration and reassessment — Most initial trials of NIV should target one to two hours, unless the patient acutely deteriorates during that period. This time-frame is based upon trials in patients with acute hypercapnic hypoxemic respiratory failure (mostly due to acute exacerbations of chronic obstructive pulmonary disease [AECOPD]) [15,43]; these data suggest that improvement of the pH and arterial carbon dioxide tension (PaCO₂) within 30 minutes to two hours predicts continued success. These data are discussed in detail separately. (See "Invasive mechanical ventilation in acute respiratory failure complicating chronic obstructive pulmonary disease", section on 'Failure of noninvasive ventilation'.)

In practice, a significant amount of clinical judgement is required when assessing the response to NIV. For example, for patients who do not demonstrate improvement and who have a do-not-intubate order in place, increasing the settings or changing to a full-face mask may be appropriate with a view to re-evaluation in another one to two hours. Similarly, in patients who are minimally improved but in whom further optimization of medical therapy is pending (eg, further diuresis, bronchodilators, inotropic support, or ultrafiltration), it is not unreasonable to persist with NIV provided the delay in administering treatment is relatively short. Some patients may demonstrate partial improvement, such as improved respiratory acidosis but no improvement in oxygenation, in which case increasing the fraction of inspired oxygen (FiO₂) or switching to a mode that provides PEEP may help.

There have been efforts to develop prediction tools for NIV failure. One score includes heart rate, acidosis, consciousness, oxygenation, and respiratory rate; a higher score is predictive of NIV failure with good predictive power after one hour of NIV (area under the receiver operating curve [AUC] 0.88) [44]. Physiologic parameters and predictive scores may be integrated into management based on clinical judgement of the providers at the bedside. Further study is needed before this score can be routinely used.

Trial success — A trial is considered successful when both clinical and gas exchange criteria are improved. In such cases, persisting with NIV and monitoring for another two hours or more for continued success is reasonable. Patients should also be monitored for complications such as aspiration and pressure ulcers. Continued improvement should prompt weaning while deterioration at any point should prompt intubation and mechanical ventilation. (See 'Complications' below and 'Weaning' below.)

Trial failure — If a patient does not improve or deteriorates following a one to two hour trial of NIV, the patient should be considered to have failed NIV and be promptly intubated. Clinical judgement is imperative as no explicit physiologic thresholds are indicative of the need for intubation and invasive mechanical ventilation [45]. Clinical criteria suggesting failure include worsening gas exchange, increasing respiratory rate, worsening encephalopathy or agitation, inability to clear secretions, inability to tolerate any of the interfaces, or hemodynamic instability [43].

NIV failure rates are high [43,46,47]. Two observational studies found that approximately one-third of patients who received a trial of NIV failed [48-50]. Other observational studies suggest variable rates of NIV failure that may relate to the underlying disorder [51].

Weaning — A patient is deemed ready to wean when gas exchange and clinical parameters of acute respiratory failure have improved dramatically and the cause of respiratory failure has improved. While there are no universal physiologic parameters that support a readiness for weaning from NIV, we consider the following as reasonable:

●A respiratory rate ≥12 and ≤22 breaths per minute.

●Peripheral oxygen saturation (SpO₂) ≥90 percent on ≤60 percent FiO₂ or predicted needs can be met with oxygen delivered via high flow nasal cannulae (HFNC) or low flow oxygen.

●Hemodynamic stability (preferably off or on low dose vasopressors and heart rate ≥50 and ≤120 beats per minute).

●The pH is preferably >7.25 and the patient should ideally be afebrile, awake and alert, or easily arousable.

●Minimal NIV settings (eg, bilevel positive airway pressure 10 cm H₂O/5 cm H₂O or continuous positive airway pressure ≤10 cm H₂O).

Similarly, there is no universal protocol for weaning and in general, it is individualized and dependent upon the patient’s response to decreased support. Weaning from NIV may be accomplished by progressively decreasing the amount of positive airway pressure, by permitting the patient to be disconnected from the NIV for progressively longer durations, or a combination of both [52]. For example, some patients may be able to tolerate being off NIV for only one to two hours once or twice in the day while others can discontinue NIV immediately. In contrast, others may require reduced pressure support for 12 to 24 hours before tolerating an "off" period.

COMPLICATIONS — NIV is generally safe. Most complications are local and related to a tightly fitting mask:

●Local skin damage may occur due to the pressure effects of the mask and straps [53]. Cushioning the forehead and the bridge of the nose prior to attaching the mask can decrease the likelihood of these problems. Newer models may have reduced this complication, although evidence to support this observation is lacking.

●Eye irritation, sinus pain, congestion, or epistaxis due to mucosal dryness may occur and require either a lower inspiratory pressure or an oronasal mask rather than a nasal mask. Heated humidification may help prevent this complication.

●Mild gastric distention occurs frequently but is rarely clinically significant at typical levels of inspiratory pressure. However, vomiting and aspiration can occur occasionally. This complication may be more likely in those with full face or oronasal masks. Routine use of a nasogastric tube is not typically warranted. One case of pneumoperitoneum and percutaneous endoscopic gastrostomy (PEG) tube displacement has been described in association with NIV [54].

Anxiety, fear, and claustrophobia are not uncommon during the NIV experience [55]. Many of these feelings may be alleviated by bedside education and reassurance. Sedation is rarely needed. (See 'Sedation' below.)

Delirium is not uncommon in patients undergoing NIV, although it is unknown whether NIV treated patients are at an increased risk of delirium compared with other patients and if there are differences regarding the interface used [56]. The development of delirium in patients treated with NIV has been associated with an increased risk of NIV failure and a higher incidence of intensive care unit and hospital mortality [57].

Complications related to positive pressure ventilation (eg, barotrauma, hemodynamic instability) are rare during NIV compared with invasive positive pressure ventilation [58]. (See "Clinical and physiologic complications of mechanical ventilation: Overview".)

While older studies reported an association between NIV and myocardial infarction (MI) in patients with acute cardiogenic pulmonary edema (ACPE) [59-61], meta-analyses detected a possible increase in MI risk that was not statistically significant [62,63]. This risk does not generally preclude the use of NIV in patients with ACPE [64].

A case report of parotitis with prolonged NIV in ACPE use has been described [65].

SUPPORTIVE CARE AND PROCEDURES

Patient position — The patient is preferably in the upright or semi-upright position. However, NIV can be delivered in the supine or Trendelenburg position, if necessary (eg, during procedures such as central venous catheter insertion).

Sedation — Sedative and analgesic therapy that decreases respiratory drive may be administered in small doses on an individualized basis. On one hand, such therapy may enhance tolerance of NIV when anxiety or pain is limiting NIV use. On the other hand, sedatives may precipitate worsening respiratory failure or arrest and prompt intubation.

The risks benefit ratio of sedatives and analgesics for patients with acute respiratory failure on NIV are poorly studied. One prospective observational study reported that, compared with the administration of either a sedative or an analgesic, the combined use of both agents was associated with a five-fold increase in NIV failure (due to worsening respiratory failure) [66]. Single-agent therapy was not associated with adverse outcomes. However, methodologic flaws prohibit firm conclusions from this study. In another meta-analysis of 12 studies, the use of dexmedetomidine reduced the risk of intubation (relative risk [RR] 0.54, 95% CI 0.41-0.71; moderate certainty), delirium (RR 0.34, 95% CI 0.22-0.54, moderate certainty), and intensive care unit length of stay (mean difference -2.40 days, 95% CI -3.51 to -1.29 days; low certainty) [67]. These benefits came at the price of increased incidence of bradycardia (RR 2.80, 95% CI 1.92-4.07; moderate certainty) and hypotension (RR 1.98, 95% CI 1.32-2.98; moderate certainty).

Feeding — Patients in acute respiratory failure, particularly those on an orofacial mask, are not typically enterally fed due to the slight increased risk of aspiration that can occur from NIV-related gastric distension. Nasogastric tubes also disrupt the seal in the interface and promote air leaks. If malnutrition is a concern, parenteral feeding is an option. (See "Nutrition support in intubated critically ill adult patients: Initial evaluation and prescription".)

However, in rare cases, some patients may be allowed to eat small meals during their "off" period when weaning, especially if parenteral feeding is not desirable. Enteral tube feeding (eg, via a nasogastric or gastrostomy tube) is rarely permitted.

Bronchoscopy — Bronchoscopy is not typically performed during NIV, most often due to the theoretical risk of precipitating worsening respiratory failure or respiratory arrest that might prompt intubation. However, bronchoscopy is technically feasible and, if necessary, it can be performed using a full face mask with a swivel adapter through which the bronchoscope can pass [68]. In most cases, the bronchoscope is passed through the nose and the airways examined in the usual fashion. The procedure can be performed in the upright or supine position, preferably the former. (See "Flexible bronchoscopy in adults: Preparation, procedural technique, and complications", section on 'Procedural technique'.)

Nebulizers — Ventilator circuits have universal nebulizer or inhaler ports that allow nebulized or inhaled medication to be administered (eg, bronchodilators or antibiotics) [69]. The optimal method of drug delivery to the lung during NIV is unclear. Some experts reduce inspiratory flow during nebulization to maximize drug deposition while others do not change ventilatory settings. Alternatively, some patients may tolerate being off NIV for a short period (a few minutes) while the drug is being nebulized in the standard fashion. No method has been proven superior over another and most institutions develop their own policy such that the clinician should be aware of local practices. (See "Invasive mechanical ventilation in acute respiratory failure complicating chronic obstructive pulmonary disease", section on 'Bronchodilators' and "COPD exacerbations: Management", section on 'Hospital-based bronchodilator therapies'.)

Suctioning — Suctioning is routine during NIV. When needed, patients wearing nasal masks or prongs may be suctioned orally or orotracheally. For patients wearing oronasal or full-face masks, the interface can be temporarily removed for a limited period to allow rapid suctioning or give the patient time to cough and clear their own secretions.

NIV is relatively contraindicated in patients who need frequent suctioning to clear their own secretions or who are at increased risk of vomiting into an orofacial mask. These and other contraindications are discussed separately. (See "Noninvasive ventilation in adults with acute respiratory failure: Benefits and contraindications", section on 'Contraindications'.)

Circuit — Circuit maintenance is similar to that described for patients on mechanical ventilation. (See "The ventilator circuit".)

Nursing care and travel — Routine nursing care such as turning and mouth care can be delivered during NIV. For procedures that require travel (eg, computed tomography imaging), a portable ventilator can be used understanding that settings on many portable devices may not exactly mimic those provided by standard ventilators. Thus, procedures that require travel should be minimized, performed only when absolutely necessary, and trained staff should always accompany the patients (eg, nursing and respiratory therapy).

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: Noninvasive ventilation in adults".)

SUMMARY AND RECOMMENDATIONS

●Definition – Noninvasive ventilation (NIV) refers to the delivery of positive pressure ventilation through a noninvasive interface (eg, nasal mask, face mask, or nasal plugs), rather than an invasive interface (endotracheal tube, tracheostomy). (See 'Introduction' above.)

●Timing, site, ancillary staff – Once a patient has been selected to receive a trial of NIV, it should be initiated as soon as possible by staff experienced in its use. NIV is typically initiated in the emergency department (ED), the intensive care unit (ICU), or a specialized respiratory or high dependency unit but may also be successfully used in the general ward setting. Support with appropriate staff knowledgeable and experienced in NIV use is critical to its success. (See 'Timing, site, ancillary staff' above.)

●Components – NIV can be delivered via a standard ICU ventilator or a bedside portable ventilator. The oronasal mask (picture 1) is the most common mask used to deliver NIV, although a nasal mask or prongs (picture 2 and picture 3) with or without a chin strap is appropriate alternative when an oronasal mask is not tolerated. Positive pressure and oxygen are delivered via circuit tubing attached to the interface. (See 'Choosing the components of noninvasive ventilation' above.)

●Initial settings – Selecting appropriate initial settings depends upon the mode selected to deliver NIV, resource availability, clinician and staff expertise, and patient tolerance. While there is no universal approach to selecting initial settings for NIV, we suggest the following as a guide (table 2):

•Bilevel positive airway pressure (BPAP) – For patients in whom BPAP is chosen, typical initial settings include (see 'Bilevel noninvasive ventilation' above):

-BPAP mode in the spontaneous/timed (S/T) setting with a backup rate of 8 to 12 breaths/minute

-Inspiratory positive airway pressure 8 to 12 cm H₂O

-Expiratory positive airway pressure 3 to 5 cm H₂O

-Fraction of inspired oxygen (FiO₂) targeting peripheral O₂ saturation (SpO₂) >90 percent

•Continuous positive airway pressure (CPAP) – For patients in whom CPAP is chosen, typical initial settings include (see 'Continuous positive airway pressure (CPAP)' above):

-CPAP at 5 to 8 cm H₂O

-FiO₂ targeting SpO₂ >90 percent

•Other modes – For patients who require more complex modes of mechanical ventilation (eg, pressure support ventilation or volume-limited ventilation in the assist controlled mode) switching to a standard ventilator may be necessary and settings adjusted according to that mode. (See 'Uncommon modes' above and "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Mode-specific settings'.)

●Monitoring and follow-up – After NIV is initiated, the patient should be observed closely for the first few minutes to troubleshoot any initial problems. If needed, the settings can be titrated upward as tolerated. Close attention needs to be paid during titration looking for improved dyspnea, decreased respiratory rate, increased tidal volume and minute ventilation (if being monitored), and good patient-ventilator synchrony.

Once the patient is comfortable, vital signs, oxygenation, and mental status are observed for the next one to two hours in a closely monitored setting. At that point, we typically re-evaluate the patient clinically and obtain arterial blood gases. When the patient demonstrates improvement in clinical signs, symptoms, and gas exchange, we typically persist with NIV. We wean from NIV when clinical parameters of acute respiratory failure have improved dramatically and the cause of respiratory failure has improved. However, if the patient does not improve or shows signs of deterioration at any time during the trial, NIV should be abandoned and the patient promptly intubated. (See 'Initial monitoring and follow-up' above.)

●Complications – NIV is generally safe. Most complications are local and related to the tightly fitting mask. These include local skin ulcerations, nasal and eye irritation and dryness, and gastric distention. Aspiration and complications related to positive pressure ventilation (eg, barotrauma, hemodynamic instability) are rare. (See 'Complications' above.)

●Supportive care and procedures – NIV is typically administered in the upright or semi-upright position. Sedative and analgesic therapy that decreases respiratory drive may be administered in small doses on an individualized basis when the benefit of NIV tolerance is thought to outweigh the risk of worsening respiratory failure. Enteral feeding is typically withheld, and while bronchoscopy is technically feasible, many experts, including us, avoid it unless necessary. Nebulized medications, suctioning, circuit maintenance, and nursing care are performed in a similar fashion to that in patients who are intubated. (See 'Supportive care and procedures' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Kristy Bauman, MD, who contributed to earlier versions of this topic review.