Aetna considers noninvasive positive pressure ventilation (NPPV) with bi-level positive airway pressure (bilevel PAP, BIPAP) devices medically necessary durable medical equipment for members who have restrictive thoracic disorders, severe chronic obstructive pulmonary disease (COPD), central sleep apnea, or obstructive sleep apnea, and who meet the medical necessity criteria for these conditions:

1. Restrictive Thoracic Disorders:
   
   
   1. Member has a progressive neuromuscular disease (e.g., amyotrophic lateral sclerosis, etc.) or a severe thoracic cage abnormality (e.g., post-thoracoplasty for tuberculosis, etc.), and
   2. Member has symptoms of nocturnal hypoxemia, such as fatigue, dyspnea, morning headache, etc., and
   3. COPD does not contribute significantly to the member's pulmonary limitation, and
   4. Member has clinically significant hypoxemia, as indicated by any of the following:
      
      
      1. An arterial blood gas PaCO₂, done while awake and breathing the member's usual FIO₂ (fractional inspired oxygen concentration), is greater than or equal to 45 mm Hg, or
      2. Sleep oximetry demonstrates oxygen saturation less than or equal to 88% for at least five continuous minutes, done while breathing the member's usual FIO₂, or
      3. For progressive neuromuscular disease only, maximal inspiratory pressures less than 60 cm H₂0 or forced vital capacity (FVC) less than 50% predicted.
         

2. Severe Chronic Obstructive Pulmonary Disease:
   
   
   1. Member has symptoms of hypoxemia, such as fatigue, dyspnea, morning headache, etc., and
   2. Member has severe COPD, as indicated by either of the following:
      
      
      1. An arterial blood gas PaCO₂, done while awake and breathing the member's usual FIO₂, is greater than or equal to 55 mm Hg, or
      2. An arterial blood gas PaCO₂ of 50 to 54 mm Hg and either of the following:
         
         
         1. Sleep oximetry demonstrates oxygen saturation less than or equal to 88% for at least five continuous minutes, done while breathing oxygen at 2 liters per minute (LPM) or the member's usual FIO₂, whichever is higher, or
         2. Hospitalization related to recurrent (greater than or equal to 2 in a 12-month period) episodes of hypercapnic respiratory failure.
            

   3. Prior to initiating therapy, obstructive sleep apnea (OSA) (and treatment with CPAP) has been considered and ruled out.
      If all of the above criteria for members with COPD are met, a bilevel PAP device without a backup rate feature will be considered medically necessary.  A bilevel PAP device with a backup rate feature will only be considered medically necessary for COPD if the member continues to meet the criteria set forth in B.2. above, despite at least two months of compliant use (an average of 4 hours use per 24-hour period) of a bilevel PAP device without a backup rate feature.
      

3. Central Sleep Apnea (CSA), i.e., apnea not due to airway obstruction:
   Prior to initiating therapy, a complete inpatient, attended polysomnogram must be performed documenting the following:
   
   1. The diagnosis of CSA, and
   2. The exclusion of OSA as a primary cause of sleep-associated hypoventilation, and
   3. The ruling out of CPAP as effective therapy if OSA is a component of the sleep-associated hypoventilation, and
   4. Oxygen saturation less than or equal to 88% for at least five continuous minutes, done while breathing oxygen at 2 LPM or the member's usual FIO₂, whichever is higher, and
   5. Significant improvement of the sleep-associated hypoventilation with the use of NPPV device on the settings that will be prescribed for initial use at home, while breathing the member's usual FIO₂.
      

4. Obstructive Sleep Apnea:

   1. A complete, inpatient, attended polysomnogram has established the diagnosis of OSA, and
   2. Member meets the criteria for CPAP, as set forth in the CPB 4 -- Obstructive Sleep Apnea, and
   3. CPAP has been tried and proven ineffective.

If all of the above criteria are met, a bilevel PAP device without a backup rate feature will be considered medically necessary for members with OSA. A backup rate feature for a bilevel PAP device is of no proven value for the primary diagnosis of OSA and therefore will be considered experimental and investigational.

Members should be re-evaluated after 2 to 3 months to evaluate their continued medical necessity for noninvasive positive pressure ventilation.  For establishment of continued medical necessity beyond 3 months, the medical records should document that the member has been compliantly using the device (an average of 4 hours per 24-hour period), and that the member is benefiting from its use.

Aetna considers NPPV experimental and investigational for all other indications.

Single-Breath Tests for Determining Airway Closure Volume:

Aetna considers single-breath nitrogen test experimental and investigational because the value of this test in the management of persons with pulmonary disorders/diseases has not been established.  Single-breath tests for determining airway closure volume that are performed using other tracer gases such as xenon, argon, or helium are also considered experimental and investigational.  

Notes: Electrical generators to power respirators, bilevel PAP devices, etc. do not meet Aetna’s definition of DME because they are not primarily medical in nature, and they are of use in the absence of illness and injury.

Over the past decade, noninvasive positive-pressure ventilation (NPPV) delivered by a nasal or facemask has gained increasingly widespread acceptance for the support of both chronic and acute ventilatory failure.  The development of improved masks and ventilatory technology made this mode of ventilation acceptable.  This policy focuses on the use of the bilevel PAP ventilator, and is based on Medicare policy and on the conclusions of a recent consensus conference on noninvasive positive pressure ventilation (NAMDRC, 1999).

NPPV for Restrictive Thoracic Diseases:

A wide variety of restrictive thoracic diseases have been successfully treated with NPPV, including thoracic cage abnormalities (e.g., chest wall deformities, kyphoscoliosis, thoracoplasty, etc.) in addition to both rapidly and slowly progressive neuromuscular disorders (e.g., amyotrophic lateral sclerosis (ALS), neuropathies, myopathies, dystrophies, sequelae of polio, spinal cord injury, etc.).  These conditions result in derangement of hypoventilation, and oxygen therapy alone is not only usually ineffective in relieving symptoms, but may also be dangerous and lead to a marked acceleration of carbon dioxide (CO₂) retention.  NPPV is generally not indicated for patients who cannot cooperate with NPPV treatment or who need a protected airway to handle excessive secretions.  (Patients who have impaired ability to protect the upper airway or excessive secretions are usually better managed with tracheostomy.)  The availability of a full face mask, however, has made it possible to use NPPV even in patients with significant bulbar weakness.

Indications for NPPV are based on symptoms attributable to nocturnal hypoventilation and objective findings of nocturnal de-saturation.  The most common symptoms of chronic respiratory failure are associated with nocturnal sleep disruption, and include daytime hypersomnolence, excessive fatigue, morning headache, cognitive dysfunction, and even dyspnea.  A consensus conference suggested that any PaCO₂ greater than or equal to 45 mm Hg or abnormal nocturnal oxygen de-saturation is a sufficient indication for NPPV.  Clinically significant hypoxemia during sleep has been defined as an oxyhemoglobin saturation of less than or equal to 88% for at least 5 minutes.  This criterion for clinically significant nocturnal hypoxemia was favored because it is relatively simple to determine and is consistent with established guidelines for determination of hypoxemia for oxygen therapy.

For patients with progressive neuromuscular disorders, the consensus panel concluded that pulmonary function test results may be an additional indicator of nocturnal de-saturation.  Most amyotrophic lateral sclerosis patients have a forced vital capacity (FVC) below 50% predicted before either the physician or patient actually becomes aware of any respiratory system involvement.  Other measurements like maximal inspiratory pressure with a magnitude less than 60 cm H₂O have been shown to be highly sensitive albeit less specific indicator of nocturnal de-saturation.

What type of equipment and what specific ventilator settings should be chosen are controversial.  Most studies of long-term NPPV for patients with neuromuscular disease have used volume- rather than pressure-targeted devices.  More recent reviews have cited the advantages of pressure-targeted devices for comfort and in their ability to compensate for leaks.  Volume-targeted equipment may be favorable for patients simply because triggering mechanisms are more adjustable and pressure-targeted systems are not able to guarantee a minimum minute ventilation.  The need for a mandatory backup rate, however, is more generally accepted because of the profound rapid eye movement (REM) de-saturation that often occurs in patients with respiratory muscle weakness.

Physician reassessment of patient benefit and adherence to NPPV therapy should occur within 60 days of initiation of therapy.  The specific methods used may be as simple as a patient interview to assess compliance but usually involve some assessment of awake arterial blood gas values and overnight oximetry while using the designated NPPV therapy.

NPPV for COPD:

During the 1980s, investigators used negative-pressure ventilators, mainly of the tank or "wrap" type, to provide intermittent respiratory muscle rest in patients with severe COPD.  However, a number of long-term controlled clinical studies showed negative-pressure ventilation to be of no benefit in pulmonary function, daytime gas exchange, or functional capability.  Furthermore, patients tolerated negative-pressure ventilators poorly.

Clinical studies of NPPV in patients with COPD (e.g., chronic bronchitis, emphysema, bronchiectasis, cystic fibrosis, etc.) have shown that NPPV is better tolerated than negative-pressure ventilation.  In addition, advantages of ease of administration and portability as well as the ability to eliminate obstructive sleep apneas make NPPV the first choice of noninvasive modes.

Although the evidence is conflicting and far from definitive, the consensus conference concluded that patients with substantial daytime CO₂ retention, particularly those with nocturnal oxygen de-saturation, appear most apt to respond favorably to nocturnal NPPV.  Patients with little or no CO₂ retention, regardless of the severity of airway obstruction, appear to gain little or no benefit from NPPV.

NPPV for Other Respiratory Disorders Associated with Nocturnal Hypoventilation:

A variety of other respiratory disorders have been shown to predispose patients to nocturnal hypoventilation.  These include central (non-obstructive) sleep apnea and obstructive sleep apnea (OSA).

Most reports covering the effect of noninvasive ventilation on hypoventilation have focused on neuromuscular/chest wall disorders and patients with COPD.  In contrast, there are few reports on noninvasive ventilation in patients with other disorders leading to nocturnal hypoventilation that may be treated with NPPV.  Furthermore, although there are many reports demonstrating the benefits of CPAP in patients with OSA, there are only limited data supporting the use of NPPV in these types of patients who fail to respond to CPAP therapy.

Based on available literature, certain general statements regarding indications for noninvasive positive pressure ventilation for other nocturnal hypoventilation syndromes can be made.  Patients considered for this therapy should have the following: a disease known to cause hypoventilation; symptoms and signs of hypoventilation; failure to respond to first-line therapies in mild cases of hypoventilation (i.e., treatment of primary underlying disease with bronchodilators, respiratory stimulants, weight loss, supplemental oxygen, CPAP); or have moderate-to-severe hypoventilation.

A polysomnogram is required for diagnosis of sleep apnea.  A CPAP trial is recommended if OSA is documented unless a previous CPAP trial was unsuccessful.

Potential side effects from NPPV include gastric distention, aspiration of gastric contents, conjunctivitis, facial abrasions from tight-fitting masks, hypotension, and mask dislocation leading to transient hypoxemia.

NPPV for Respiratory Failure after Extubation/Acute Hypoxemic Respiratory Failure:

The need for re-intubation after extubation and discontinuation of mechanical ventilation is not uncommon and is associated with increased mortality.  NPPV has been suggested as a treatment for individuals with respiratory failure following extubation.  In a multi-center, randomized, controlled trial (n = 221), Esteban et al (2004) examined the effect of NPPV on mortality in this clinical setting.  These investigators concluded that NPPV does not prevent the need for re-intubation or reduce mortality in unselected patients who have respiratory failure following extubation.  This is in agreement with the findings of Keenan et al (2002) who reported that the addition of NPPV to standard medical therapy does not improve outcome in heterogeneous groups of patients who develop respiratory distress during the first 48 hours after extubation.

Furthermore, in a recent review, Keenan et al (2004) evaluated the effect of NPPV on the rate of endotracheal intubation, intensive care unit and hospital length of stay, and mortality for patients with acute hypoxemic respiratory failure not due to cardiogenic pulmonary edema.   The authors concluded that randomized trials suggest that patients with acute hypoxemic respiratory failure are less likely to require endotracheal intubation when NPPV is added to standard therapy.  However, the effect on mortality is less clear, and the heterogeneity found among studies suggests that effectiveness varies among different populations.  As a result, the literature does not support the routine use of NPPV in all patients with acute hypoxemic respiratory failure.

In a Cochrane review, Shah and colleagues (2005) stated that acute hypoxemic respiratory failure (AHRF) is an important cause of morbidity and mortality in children. Currently, positive pressure ventilation is the standard of care, although it is known to be associated with complications. Continuous negative extra-thoracic pressure ventilation (CNEP) or continuous positive airway pressure ventilation delivered via non-invasive approaches (Ni-CPAP) have demonstrated certain benefits in animal as well as uncontrolled human studies. These investigators evaluated the effectiveness of CNEP and Ni-CPAP in children with AHRF due to non-cardiogenic causes. They concluded that there is a lack of well-designed, controlled studies of non-invasive modes of respiratory support in pediatric patients with AHRF.

Single Breath Nitrogen Test:

The single breath nitrogen test (SBNT) is a pulmonary function test that provides information on the evenness of distribution of ventilation and on closing volume.  The test utilizes resident nitrogen (N₂) in the lung as the tracer gas, and a single inhalation of 100 % oxygen to cause a change in the N₂ concentration in the lungs.  It is performed by having the subject breathe air normally through a mouthpiece, and after a single vital capacity inspiration of 100% O₂, expire slowly and smoothly to residual volume.  Expired N₂ concentration is then plotted against expired volume (single breath nitrogen washout curve).  From this, information about the distribution of ventilation can be obtained.  Similar measurements may be made using other tracer gases such as xenon, argon, or helium.  

There are usually four phases to the single breath nitrogen washout curve -- phase I represents dead space gas containing zero N₂; phase II is mixed dead space and alveolar gas; phase III is gas from the alveoli; and phase IV represents a sharp increase in N₂ concentration.  In normal persons in whom the alveoli empty synchronously, phase III shows a plateau during which N₂ concentration rises only slowly.  The slope of phase III (change in N₂ concentration per 500 ml of expired air) should be less than 1.5 %.  The lung volume at which phase III changes to phase IV is closing volume (the volume at which closure of airways occur in the lower part of the lungs).  An increase in closing volume, especially when it is larger than functional residual volume, indicates premature closure of intrapulmonary airways as a result of the narrowing of small airways or reduced elastic recoil.

It was thought that the SBNT might detect chronic airway disease before it is clinically apparent.  However, it has not been demonstrated conclusively to be more sensitive than other tests. 

Most patients with established disease and an abnormal slope of phase III do not produce single breath tests from which closing volumes can be measured.  The American Thoracic Society (ATS) Standards for the Diagnosis and Care of Patients with Chronic Pulmonary Disease (1995) notes that small airways (i.e., less than 2 mm in diameter) are important sites of airflow obstruction, and that he relative contribution of peripheral airway disease and loss of elastic recoil from emphysema may vary.  However, the ATS Standards states that indices such as the closing capacity and the slope of the alveolar plateau derived from a SBNT are unable to identify individuals susceptible to chronic airway obstruction with cigarette smoke exposure.  The ATS Standards notes that tests reflecting emphysema (e.g., single-breath diffusing capacity, functional residue capacity, total lung capacity) predict survival in a relatively minor way. 

Fraser, et al. (1999) concluded that the SBNT has not been shown to be useful in identifying patients at risk for developing COPD.  Fraser explained that, although epidemiological studies have demonstrated that the results of the SBNT is abnormal in many asymptomatic smokers, there is controversy regarding the value of this measurement, as it appears that this test may not offer advantages over simple spirometry in detecting the progression of airflow obstruction.  Fraser, et al. explains that one reason SBNT has been less discriminating than was originally hoped in identifying smokers at risk for the development of progressive disease is the marked inter-subject and intra-subject variability in test results.  In addition, Fraser, et al. notes that it has not been convincingly shown that the rate of decrease in forced expiratory flow in smokers correlates with abnormalities in small airway function.  

A number of empirical studies have documented the limited clinical value of SBNT.  Teculescuet, et al. (1988) noted that the SBNT did not detect any effect of involuntary smoking in a limited sample of children.  Vestbo and Rasmussen (1990) reported that indices of the SBNT (e.g., closing volume, closing capacity, and slope of phase III) have no predictive value concerning overall mortality and cancer incidence.  Vestbo, et al. (1990) concluded that in a random population sample indices from only one SBNT do not provide prognostic information concerning hospitalization in addition to that provided by forced expiratory volume in 1 sec (FEV1).  Viegi, et al (1988) stated that the place of SBNT in large scale epidemiologic testing has not been justified.  Detels, et al. (1982) reported that the single-breath nitrogen test yielded less specific or different information than spirometry, the flow-volume curve, and the ratio of FEV1 to forced vital capacity (FVC) in identifying abnormal lung function.  Reporting on SBNT and FEV1 in a cohort of individuals followed over a 9 to 11 year period, Vollmer, et al. (1990) concluded that SBNT variables are less reproducible than FEV1.  Dahlqvist (1995) reported on the results of an 8-year correlational study involving 24 healthy subjects, and concluded that the “prognostic value of an abnormal single-breath nitrogen wash-out seems to be limited” in predicting an accelerated decline in FEV1.  Moreover, Bourgkard et al (1997) reported that subjects with dust exposure and roentgenologic pneumoconiosis nodulation were unable to adequately perform SBNT; however, these subjects were able to performed spirometry satisfactorily.  Thus, the SBNT has not been proven to be useful in detecting early lung dysfunction and selecting persons at risk for appropriate measures to prevent progression to advanced disease.