Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Adaptation and follow-up after initiation

INTRODUCTION — Noninvasive ventilation (NIV) is commonly used to assist ventilation in patients with chronic respiratory failure from neuromuscular and chest wall diseases. In some patients with neuromuscular disease, facilitating adjustment to NIV for chronic use is important, as regular use has been shown to lengthen survival, improve quality of life, and delay the need for tracheostomy [1].

While many patients initially have difficulty tolerating NIV, education and addressing reasons for intolerance can improve adherence. Our approach to the adaptation and optimization of NIV in patients with chronic respiratory failure due to neuromuscular and chest wall diseases is reviewed here. The indications for and the practical aspects of NIV initiation in this population are discussed separately.

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

●(See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Patient selection and alternative modes of ventilatory support".)

●(See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation".)

ADAPTATION PHASE AFTER INITIAL TITRATION — The aim of chronic NIV is to lower and stabilize daytime arterial partial pressure of carbon dioxide (PaCO₂) and improve sleep quality, oxygenation, and daytime symptoms of hypoventilation.

Initial instructions — The adaptation phase, which occurs during the first few weeks after initiation, poses the greatest challenge in gaining patient acceptance of NIV. Using settings discovered during the initial titration trial (see "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Initial trial'), patients are instructed to use NIV each night for at least a few hours, or for as long as is possible. Further adjustments are subsequently made during follow-up visits as indicated by symptoms, tolerance, and gas exchange parameters. Selection of interface, ventilator, and initial titration of NIV are discussed separately. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation".)

We encourage patients to attempt adaptation for at least several weeks or months before giving up. Most patients are able to sleep successfully through the night after a few weeks, but some may require months of adaptation. In our experience, adaptation is more likely to be successful when patients begin noticing symptomatic improvement. However, approximately 5 to 10 percent of patients fail to adapt successfully to NIV, usually because of intolerance (eg, mask discomfort or claustrophobia). (See 'Symptoms and gas exchange fail to improve' below.)

In rare circumstances, we use low-dose hypnotics to encourage adaptation. However, they should be used with great caution in this population, and we avoid them in patients with substantial nocturnal or daytime respiratory acidosis with carbon dioxide (CO₂) retention (eg, PaCO₂ >50 mm Hg).

Assess symptoms and tolerance — We typically see patients approximately four to six weeks after the initiation of NIV. Assessment at that time should focus on the following:

●Hours of nightly use – This can be evaluated by directly questioning the patient or the patient's bed partner, and/or by obtaining data downloaded from the device itself. (See "Downloading data from positive airway pressure devices in adults".)

●Symptoms of hypoventilation – We ask whether the symptoms of hypoventilation have improved (eg, fatigue, early morning headache or dyspnea, daytime hypersomnolence). Improvements in symptoms should be evident when the patient has successfully adapted and is sleeping for at least four to five hours per night with NIV and when ventilation is sufficient. Daytime heart rate also often slows when NIV has been successful. While the normalization of PaCO₂ is ideal, we place a greater importance on targeting elimination or good control of daytime symptoms.

●Intolerance or complications – We ask about intolerance and potential complications of NIV that are interfering with adherence. This includes mask intolerance, nasal dryness or congestion, nasal bridge ulceration, air leaks, and abdominal distension from gastric insufflation. We address these issues before attempting to increase NIV settings. (See 'Addressing intolerance and complications' below and 'Other complications' below.)

Assess gas exchange

Timing — We obtain follow-up measurements of oxygenation and CO₂ after a few weeks on NIV when the patient is using the device for at least four hours out of every 24-hour cycle.

Measurement parameters — To assesses adequacy of gas exchange and determine whether oxygen supplementation is indicated, we obtain overnight pulse oximetry (peripheral oxygen saturation [SpO₂]) with or without transcutaneous partial pressure of carbon dioxide (PtcCO₂) monitoring while the patient is using NIV at home. End-tidal CO₂ monitoring (P_ETCO₂) is not recommended during NIV because the variable air leakage from the mask renders tracings unreliable.

We also assess daytime PaCO₂. Arterial blood gas (ABG) measurement is most accurate, but venous blood gas (VBG) analysis, PtcCO₂, or P_ETCO2 (the latter when not using NIV) are alternatives that can be compared with the pre-NIV baseline measurements. When using VBG analysis, interpretation should be done knowing that the PaCO₂ on VBG analysis is usually 3 to 8 mm Hg higher than that on ABG analysis, and varies considerably, especially when PaCO₂ is severely elevated. (See "Venous blood gases and other alternatives to arterial blood gases".)

In patients receiving optimal settings, we periodically assess serum bicarbonate. If the bicarbonate level rises, we typically proceed with more detailed gas exchange assessment and possible re-optimization of settings. (See 'Worsening symptoms or gas exchange after initial improvement' below.)

Targets — We aim to achieve the following targets:

●In patients with evidence of CO₂ retention, we target a near-normal daytime PaCO₂ (by a few weeks). However, normalization of PaCO₂ may not be attainable because of the patient's inability to tolerate a high enough inspiratory pressure or duration of NIV, or mechanical factors such as chest wall stiffness or obesity. In such cases, we accept daytime PaCO₂ elevation up to 60 mm Hg (7.98 kPa) as long as symptoms of hypoventilation are well controlled.

●In patients without evidence of CO₂ retention, we target maintenance of normocapnia.

●In all patients, SpO₂ should ideally be ≥90 percent for ≥95 percent of sleep time (five minutes or less with the SpO₂ ≤88 percent during sleep may be acceptable).

We also analyze the tracing for frequent intermittent drops in SpO₂ (ie, "sawtooth" pattern) that could be due to breakthrough sleep-related obstructive events, sustained episodes of desaturation that could be indicative of sleep-disordered breathing, persistent hypoventilation, nonadherence, or comorbidities such as airway or parenchymal disease.

If the overnight oximetry shows desaturations, the ABG shows no improvement, and/or obstructive sleep apnea is suspected, we obtain overnight polysomnography and re-titrate NIV, if necessary.

ADDRESSING INTOLERANCE AND COMPLICATIONS — Intolerance to NIV is common. Addressing the reasons for intolerance is key for the future success of NIV in patients with chronic respiratory failure from neuromuscular and chest wall disorders. Typically, we educate the patient regarding alternative options for interfaces, headgear, humidity, and pressure settings, which enables them to be an active participant in the adjustment period and encourages acceptance. If patients remain intolerant nocturnally, they may still achieve gas exchange benefits if the device is used during the day. Educating patients regarding the alternatives (eg, tracheostomy) may also facilitate motivation.

Mask (interface) intolerance — Discomfort from nasal or oronasal masks (picture 1) is the most common problem encountered in patients adapting to NIV (eg, sense of claustrophobia) [2].

The most common initial interface chosen is a nasal mask. To prevent mask intolerance, we ensure that the nasal mask fit is optimal and that minimal strap tension is used to control air leaking (see "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Interface and strap tension'). If mask intolerance is an issue, we perform one or both the following:

●Change the interface:

•Perform brief trials with different types of interfaces such as the "memory foam" nasal masks, mini-masks, nasal pillows (picture 2 and picture 3), nose cradles, or custom-fit masks.

•Oronasal masks are also an alternative, provided the patient can manipulate the mask themselves (ie, those with adequate upper extremity strength) or has caregivers readily available to remove the mask in the event of an emergency (eg, vomiting, secretion buildup, power failure) to prevent asphyxiation.

•Oral-only interfaces may be successful in some patients, and can be started during wakefulness.

Further details regarding choosing an interface are provided separately. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Interfaces (masks)'.)

●Increase mask tolerance by instructing the patient to wear the mask for brief, but progressively longer, periods during nonsleep hours while watching television or participating in another distracting activity.

Despite these efforts, a minority of patients may be unable to tolerate the sensation of a foreign body strapped to the face, and alternative options should be discussed with the patient (eg, tracheostomy). (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 'Other options'.)

Nasal congestion or dryness — Both nasal congestion and dryness occur commonly during NIV, and sometimes in the same patient. These complaints tend to be seasonal (eg, dryness worse during the winter months) and should be treated symptomatically.

●Nasal dryness – We treat nasal dryness with the intranasal application of a saline spray or gel and the use of heated humidification, tubing insulation, or heated tubing.

Nasal dryness often responds well to nasal saline and water-based nasal gels. Nasal gels can be applied in a thin layer along the inside of the nose and can help reduce mucosal discomfort and irritation. We do not use petroleum gels due to the risk of lipid aspiration. (See "Aspiration pneumonia in adults", section on 'Lipoid pneumonia'.)

In-line heated humidification with heated tubing (used to avoid condensation (see 'Condensation' below)) has become standard with most newer devices to reduce the incidence of nasal dryness from NIV [3]. Both the warmth and increased humidity of air enhance comfort and decrease nasal resistance to airflow, which is particularly helpful for patients with concomitant obstructive sleep apnea [4]. However, not all devices have built-in humidifiers. Thus, it behooves the clinician to be aware of the device being used by the patient and the humidification system necessary for that device.

When a humidifier is in place, the heater may be adjusted to increase or decrease the humidity of the incoming air as needed depending on the local environmental conditions, the pressures at which the ventilator is set, and patient preference [5].

Pass-over humidifiers (ie, gas passes over the surface of water) are most often used with pressure-limited ventilators, in order to avoid the drop in pressure that could occur with pass-through humidifiers (ie, gas is bubbled through water). The drop in pressure is less concerning for volume-limited devices such that either humidification can be used. (See "Noninvasive ventilation in adults with acute respiratory failure: Practical aspects of initiation", section on 'Ventilator type'.)

●Nasal congestion – We treat nasal congestion with over-the-counter antihistamine or antimuscarinic decongestants. For patients who fail this approach, we use nasal glucocorticoid alone or in combination with decongestants.

Condensation — Condensation inside the tube or mask is known as "rain-out." "Rain-out" is particularly problematic in cold climates where the indoor temperatures are often lower at night or when the heated humidifier is set too high and the room air is cold.

To address this phenomenon, we typically increase the heat on the heated tubing (if this is available) or reduce the temperature setting of the heated humidifier.

Heated tubing has significantly decreased the problem of water condensation and is available with several brands of positive airway pressure (PAP) devices. In addition, water chamber and tube temperatures can be linked in an "auto" mode that regulates the humidity based upon the desired setting and the ambient air humidity. If heated tubing is not available and condensation is still noted, the tubing may be insulated with a light-weight cloth, a commercially available tube sleeve made for PAP tubing, or other insulating material created by the patient or caregivers.

Strap-related or nasal bridge ulceration or rash — Nasal bridge redness or ulceration is caused by excessive pressure on the nasal bridge from a nasal mask due to excessive strap tension. Excessive strap tension usually results from efforts to reduce air leaking around the mask, which may irritate the eyes.

●To address this issue, we minimize strap tension and optimize the seal. An adequate seal can be achieved by using foam or rubber "spacers," silicone inserts, or artificial skin to the bridge of the nose (eg, Duoderm, Restore).

●As an alternative, switching to another mask is an option. Suitable alternatives include masks with a foam inner seal, mini-masks, or nasal pillows and nose "cradles" (picture 2). These masks usually have a soft silicone membrane with a hole for the nostrils that seals on the skin around them.

In addition, there are several oronasal masks that fit under the nose and do not rest on the bridge of the nose. However, use of an oronasal mask is limited to those with adequate upper body strength who can use quick release straps in the event that the mask needs to be removed in an emergency (eg, vomiting, secretion buildup, power failure) to prevent asphyxiation. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Interfaces (masks)'.)

●Alternating between different masks in patients who need NIV most or all of the time may allow irritation at one site (eg, bridge of nose or facial skin) to resolve while another contact site (eg, inside the nostril) is used. For this to be effective, the patient needs to be comfortable and the seal good with both interfaces.

Some patients develop acneiform skin rashes where the mask contacts the skin. We typically prescribe low-potency corticosteroid creams, oral doxycycline, or clindamycin lotion. Washing the face with a mild soap prior to application of the mask and soft cloth liners that fit between the mask and the skin may also be helpful.

If the cheek or neck becomes irritated by the strap edges, we place soft cloth strips of fleece or cotton under the straps to help protect the skin and ask patients to wash their face before mask application at night and to wash or wipe down the mask in the morning. In addition, there are several companies that make thin liners with or without Velcro to hold the liners in place to treat this complication.

Air leaking through the mouth — Leakage of air through the mouth is universal among users of NIV. Some air leaks are small and insignificant and others big enough to impact ventilation and contribute to sleep arousals [6], oxygen desaturations [7], and mouth dryness [6,7]. Air leak may be noticed by the patient and/or determined from data downloaded from the device. (See "Downloading data from positive airway pressure devices in adults".)

●Most patients have small air leaks during NIV and can usually be satisfactorily ventilated despite such leakage. Pressure-limited ventilators can compensate for leaks by increasing airflow to maintain mask pressure. However, leak compensation during volume-limited ventilation may require an upward adjustment in tidal volume (eg, by 2 cm H₂0). Excessive increases of tidal volume, however, may result in some narrowing of the glottis, which may, in turn, increase the air leak or gastric insufflation without increasing effectiveness of ventilation [8].

●For patients who have nasal devices and an air leak that interferes with ventilatory assistance or sleep or causes mouth dryness, we typically ensure that strap tension is appropriate and adjust it, if needed. Failing strap adjustment, the addition of a chin strap may also help.

If neither of these maneuvers reduce the leak, then we trial an oronasal mask, but only one with an anti-asphyxia valve and one with a good seal at the chin (air leaking under the mask at the chin seal may be substantial). However, use of an oronasal mask should only be used in those with adequate upper body strength, or those who have an available caregiver, to access quick release straps needed for mask removal during an emergency (eg, vomiting, secretion buildup, power failure) to prevent asphyxiation. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Oronasal masks'.)

●If a chin strap or oronasal mask fails, mouthpiece ventilation during the day will eliminate problems with air leaking through the mouth, but air leaking through the nose may still occur and necessitate use of nasal plugs. Although mouthpieces may interfere with swallowing, aspiration pneumonia has not been reported as a complication. Some mouthpieces are designed to be expectorated, but with strapped-on mouthpieces in quadriplegic patients, anti-asphyxia valves should be in place to prevent rebreathing in the event of an emergency. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Mouthpieces'.)

Gastric insufflation — Many patients notice mild abdominal distention, nausea, burping in the morning, and flatulence in association with NIV. These symptoms are usually tolerable and transient, and do not warrant changes in settings.

Intolerable distention is infrequent, probably because pressures used during NIV rarely exceed 25 cm H₂O. However, if intolerable symptoms occur, we reduce inflation pressure and add oral simethicone, which sometimes helps.

Other complications — Although generally rare, one study of 176 patients with Duchenne muscular dystrophy reported a 9 percent rate of pneumothorax following the application of NIV, under one-half of which were asymptomatic. Chest computed tomography scan revealed a cause in several patients in whom chest radiography did not identify a cause [9].

FOLLOW-UP AFTER ADAPTATION — Most patients have improvements in symptoms and gas exchange within weeks of initiating NIV, but a smaller proportion fail (5 to 10 percent). Initial assessment is described above. (See 'Assess symptoms and tolerance' above and 'Assess gas exchange' above.)

Once optimized, we continue to assess patients periodically with intermittent nocturnal oximetry, transcutaneous partial pressure of carbon dioxide monitoring, and serum bicarbonate. The frequency and intensity of monitoring has to be tailored to the severity of the patient's respiratory impairment and anticipated rate of disease progression (if applicable). Frequency of follow-up depends on whether patients are starting therapy (every few weeks), stable on therapy (twice yearly), or deteriorating clinically (every few days or weeks). (See 'Worsening symptoms or gas exchange after initial improvement' below.)

If the underlying disease progresses, additional hours of NIV are typically necessary, culminating in continuous ventilation in some patients. Many patients can succeed with continuous NIV, but some will switch to invasive ventilation via tracheostomy, especially if swallowing function is impaired. (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 'Tracheostomy with positive pressure ventilation'.)

Improved symptoms and gas exchange — If NIV is well tolerated, symptoms and daytime arterial carbon dioxide tension are well controlled, and nocturnal oximetry shows no desaturation, no further adjustments in minute ventilation are necessary.

However, for patients who have improved but fall short of the above-stated goals (see 'Assess symptoms and tolerance' above and 'Assess gas exchange' above), we further optimize NIV by increasing inspiratory pressure in small increments as tolerated such as 1 to 2 cm H₂O per week (to a maximum of 20 cm H₂O) (algorithm 1).

The larger the difference between inspiratory and expiratory pressure, the greater the inspiratory support provided to assist ventilation. This difference is usually at least 8 to 10 cm H₂O and may range up to 20 cm H₂O or more in patients with high chest wall compliance associated with obesity or a stiff chest wall (eg, due to scoliosis). (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Ventilators' and "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Adjustments during the trial'.)

Symptoms and gas exchange fail to improve — In 5 to 10 percent of patients, improvement does not occur in symptoms and gas exchange despite adaptation and tolerance. Common factors that should be considered include the following:

●Poor adherence or low number of hours of use

●Excessive air leak during inspiration

●Inappropriate ventilator settings resulting in insufficient support of minute ventilation

The differential in this scenario is different than that in patients who initially improve or stabilize following adaptation but then deteriorate. Further details on evaluating this phenomenon are provided separately. (See 'Worsening symptoms or gas exchange after initial improvement' below.)

Poor adherence and air leak — We typically initially monitor for adherence and air leak using downloads from the respiratory support device and address reasons for poor adherence with the patient, such as mask intolerance (see 'Mask (interface) intolerance' above) and air leaks. (See 'Air leaking through the mouth' above.)

Insufficient minute ventilation — When insufficient minute ventilation is suspected (eg, persistence of symptoms and lack of improvement in hypercapnia and/or hypoxemia), we increase the inspiratory pressure (for pressure-limited ventilation), tidal volume (for volume-limited ventilation), and/or ventilator rate.

In addition, if there is evidence of inability to trigger the ventilator (eg, the absence of patient-initiated breaths on the data download or observation of ineffective inspiratory efforts), adjustment of the trigger sensitivity or upward adjustment of the backup rate may be helpful [10].

Others — If the above maneuvers do not reveal poor adherence, air leak, or insufficient minute ventilation as a cause for failure, other issues that need to be addressed include:

●Rebreathing carbon dioxide (CO₂) – CO₂ rebreathing has been identified as a potential problem when blood gases fail to improve with pressure-limited ventilation (eg, bilevel positive airway pressure [PAP]) [11]. This is attributed to the use of passive exhalation valves that rely upon bias flow (ie, the continuous flow of gas responsible for replenishing oxygen and removing CO₂ from the patient's circuit). To address CO₂ rebreathing, we use expiratory PAP (EPAP) of 4 cm H₂O or greater (to assure adequate bias flow). However, this problem is less common than in the past when some devices could deliver EPAPs <4 cm H₂O [12,13].

●Residual obstructive events during sleep – In some patients, failure to improve is due to unidentified or undertreated obstructive sleep apnea which would be evident on the data downloaded from the unit and may be suggested by clinical history such as persistent snoring. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)

Nocturnal monitoring during sleep at home can be used to detect this problem [14-16]. (See "Home sleep apnea testing for obstructive sleep apnea in adults".)

When home monitoring is unhelpful, we typically obtain full in-laboratory nocturnal polysomnography. (See "Overview of polysomnography in adults".)

In addition to detection of sleep apnea and hypoventilation, these studies allow sleep staging and detection of arousals that are associated with ineffective inspiratory effort (ie, patient effort that does not trigger the ventilator), asynchrony, air leaking through the mouth or around the mask, desaturations, and other factors that may contribute to a less than optimal symptom resolution [17].

In at least one study of patients with amyotrophic lateral sclerosis, persisting obstructive events were associated with a worse prognosis, even in the absence of significant oxygen desaturation [18]. Whether adjusting settings to eliminate these obstructive events improves survival needs to be confirmed prospectively. (See "Downloading data from positive airway pressure devices in adults".)

If a reason is not evident, we consider changing ventilator mode from pressure limited to volume limited, particularly in patients with diminished chest wall compliance due to scoliosis or obesity. This strategy targets better assurance that the desired tidal volume is delivered. Another consideration in this situation is to use a volume-assured pressure support (VAPS) mode. This is a hybrid mode designed to assure target tidal volume (or minute volume) by automatically adjusting pressure support and/or respiratory rate and has been used successfully in patients with neuromuscular disease. The average VAPS-auto expiratory PAP may also be used, which allows for automatic adjustment of the expiratory PAP for ventilator-perceived obstructive events during ventilation. Superiority has not been shown, however, in achieving target blood gas levels over properly adjusted bilevel settings [19]. (See "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Ventilators'.)

WORSENING SYMPTOMS OR GAS EXCHANGE AFTER INITIAL IMPROVEMENT — Chronic worsening of symptoms or gas exchange after initial improvement is often encountered among patients with progressive neuromuscular diseases. In most cases, this is due to deteriorating lung function from disease progression. Other causes include faulty equipment, medication changes, growth of facial hair, or weight gain and other medical issues that worsen obstructive apneas or hypoventilation during sleep.

●Deteriorating lung function – We perform periodic surveillance of pulmonary function studies and arterial blood gas measurements to predict such deterioration. (See 'Assess gas exchange' above.)

Stability in these patients may be restored by increasing minute ventilation (eg, an increase in inspiratory pressure, tidal volume, ventilator rate) and/or extending the total duration of NIV per 24-hour period (eg, adding daytime naps while using NIV or using NIV while awake).

In addition, we promote good pulmonary toilet by various combinations of manually assisted coughing, mechanically assisted coughing with insufflation/exsufflation devices, and glossopharyngeal breathing [20-22]. (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 'Adjunctive therapy (cough supplementation, nutrition)'.)

●Faulty equipment – Problems with the equipment, such as a worn mask that no longer seals well or inadequate connections or holes in the tubing, may contribute to ineffective therapy. We suggest routine equipment maintenance and/or replacement when faulty equipment is an issue. The medical supply company providing the equipment should be routinely replacing components, but it is important to confirm that this is occurring and with what frequency.

●Worsening obstructive sleep apnea – In patients with concomitant obstructive sleep apnea, we typically obtain follow-up nocturnal sleep testing to determine whether hypopneas or apneas have become problematic. (See "Clinical presentation and diagnosis of obstructive sleep apnea in adults".)

●Medications and comorbidities – We review the medication list to determine if new medications have been started, which might contribute to respiratory depression or obstruction related to relaxation of upper airway muscles.

INVASIVE VENTILATORY SUPPORT — In the chronic setting, the decision to switch from noninvasive to invasive ventilation (tracheostomy) mostly depends upon patient preference. Indications include inability to tolerate NIV or inability to protect the upper airway due to impaired swallowing or cough, excessive secretions, or a combination of these factors. In our experience, most patients are reluctant to undergo invasive ventilation, and most prefer to continue NIV as long as possible; some remain on NIV indefinitely. Indications for tracheostomy are discussed separately. (See "Tracheostomy: Rationale, indications, and contraindications".)

Short-term invasive ventilation (eg, up to three weeks) may be needed for acute issues that result in failure to maintain adequate oxygenation and acute respiratory acidosis, or a combination of both. The use of invasive ventilation is often temporary if deterioration is due to an acute reversible issue (eg, infection-induced increase in secretions, atelectasis due to inspissated secretions from dehydration). A conversation between the patient and clinician is critical to determine the patient’s preferences in this regard. Further details regarding ventilatory support during acute events in patients with respiratory muscle weakness from neuromuscular disease are provided separately. (See "Respiratory muscle weakness due to neuromuscular disease: Management", section on 'Acute ventilatory support'.)

After an acute event, most patients should be able to wean back to NIV. Transitioning from invasive ventilation to NIV in those with neuromuscular disease is discussed separately. (See "Noninvasive ventilatory support and mechanical insufflation-exsufflation for patients with respiratory muscle dysfunction", section on 'Extubation to CNVS and MIE' and "Noninvasive ventilatory support and mechanical insufflation-exsufflation for patients with respiratory muscle dysfunction", section on 'Tracheostomy to noninvasive ventilatory support'.)

SUMMARY AND RECOMMENDATIONS

●Introduction – In patients with a chronic respiratory failure from neuromuscular and chest wall diseases, noninvasive ventilation (NIV) is commonly used to assist ventilation, particularly at night. While many patients initially have difficultly tolerating NIV, most adapt successfully within a few weeks or months. (See 'Introduction' above.)

●Four- to six-week assessment and goals – The aim of nocturnal NIV is to improve or eliminate daytime symptoms of hypoventilation, lower and stabilize daytime arterial partial pressure of carbon dioxide (PaCO₂) and improve oxygenation. Using settings discovered during the initial titration trial (see "Noninvasive ventilation in adults with chronic respiratory failure from neuromuscular and chest wall diseases: Practical aspects of initiation", section on 'Initial trial'), patients are instructed to use NIV each night for at least a few hours, or as long as is possible. Four to six weeks later, we evaluate patients for the following (see 'Adaptation phase after initial titration' above):

•Symptoms, adherence, tolerance – Symptoms of hypoventilation (eg, fatigue, early morning headache, daytime hypersomnolence), hours of nightly use, and evidence of intolerance or complications. (See 'Assess symptoms and tolerance' above.)

•Parameters of gas exchange – We typically obtain overnight pulse oximetry and transcutaneous carbon dioxide (tcCO₂) monitoring while the patient is wearing NIV at home. In hypercapnic patients, we target a near-normal daytime PaCO₂ level but accept a level up to 60 mm Hg (7.98 kPa), provided symptoms of hypoventilation are well controlled. We also assess daytime PaCO₂, preferably with arterial blood gas (ABG) analysis. In normocapnic patients, we target maintenance of normocapnia. For oxygenation, we target a pulse oxygen saturation ≥90 percent for ≥95 percent of sleep time (less than five minutes of peripheral oxygen saturation ≤88 percent may be acceptable) and administer oxygen supplementation if needed. (See 'Assess gas exchange' above.)

●Managing intolerance – Addressing the reasons for intolerance is key for the future success of NIV:

•For patients with discomfort from the mask (typically a nasal mask), we ensure that mask fit is optimal and that the least strap tension is used to adequately control air leaking. Trials with different types of interfaces (eg, masks with gel or foam seals or nasal pillows) and distraction techniques (eg, wearing NIV while watching television) may also help. (See 'Mask (interface) intolerance' above.)

•We treat nasal dryness with nasal saline or gel and in-line heated humidification. Nasal congestion often responds to an over-the-counter antihistamine or antimuscarinic decongestants. For patients who fail this approach, we suggest nasal glucocorticoids (Grade 2C). (See 'Nasal congestion or dryness' above.)

•Irritation at the interface contact sites (eg, bridge of the nose, face straps) can be alleviated by local measures (eg, silicone inserts or artificial skin), alternating interfaces (eg, nasal pillows), and avoiding over-tightening of the mask. (See 'Strap-related or nasal bridge ulceration or rash' above.)

•Pressure-limited ventilators can compensate for small leaks by increasing airflow to maintain mask pressure. Leak compensation during volume-limited ventilation requires an upward adjustment in tidal volume. Mouth leaks that interfere with adequate ventilation are decreased by use of a chinstrap or by changing to an oronasal mask. Use of an oronasal mask is limited to those with upper body strength in case quick release straps need to be used for an emergency to prevent asphyxiation or those who have an available caregiver to perform this task. Mouthpiece ventilation is rarely used with or without nasal pledgets in place. (See 'Air leaking through the mouth' above.)

•Intolerable gastric distention or flatulence is infrequent, but may be treated by reducing inflation pressure or adding oral simethicone, if needed. (See 'Gastric insufflation' above.)

●Additional follow-up – Most patients have improvements in symptoms and gas exchange within weeks of initiating NIV. (See 'Follow-up after adaptation' above.)

•For those who improve, further adjustments in minute ventilation can be made for optimization of NIV, if necessary. Once optimized, patients can be seen periodically with intermittent nocturnal oximetry with ABG or tcCO₂ and serum bicarbonate. Frequency of follow-up depends on whether patients are starting therapy (every few weeks), stable on therapy (twice yearly), or deteriorating clinically (every few days or weeks). (See 'Improved symptoms and gas exchange' above.)

•A small proportion of patients fail during the initial few weeks (5 to 10 percent). We typically re-address compliance and intolerance that might explain poor adherence or an air leak. When insufficient ventilation is suspected, we increase the minute ventilation. (See 'Symptoms and gas exchange fail to improve' above.)

•Worsening gas exchange after initial improvement is often due to deteriorating lung function from disease progression. Other causes include faulty equipment, medication changes, weight gain, or other medical issues that worsen obstructive apneas or hypoventilation during sleep. For those with progressive neuromuscular disease, stability may be restored by increasing minute ventilation and/or extending the total duration of NIV per 24-hour period (eg, adding daytime naps while using NIV, or using NIV while awake). (See 'Worsening symptoms or gas exchange after initial improvement' above.)

●Invasive ventilatory support – Long-term invasive mechanical ventilation with tracheostomy is typically declined. However, it may be performed in those who desire it or those with an inability to tolerate NIV or protect their upper airway. Invasive mechanical ventilation may be needed in the short term to support patients with an acute reversible issue (eg, pneumonia). (See 'Invasive ventilatory support' above.)