Noninvasive ventilation in chronic obstructive pulmonary disease

Over the past 15 years, numerous studies have explored the possibility that intermittent ventilatory assistance using noninvasive ventilation is beneficial in patients with severe stable COPD. The results are conflicting and no sustained beneficial action has been proven, although some improvement in respiratory muscle function may occur after short-term rest, and lengthening of the total duration of sleep has been shown in a few studies. Based on the observation that studies with favorable findings have generally had considerably higher PaCO2s than studies with negative findings, the current consensus view is that patients with severe CO2 retention (PaCO2 > 50-55 mm Hg) warrant a trial of NPPV. In addition, the Health Care Financing Agency that determines Medicare reimbursement policy in the United States has recently published guidelines for use of NPPV in patients with severe stable COPD that are based partly on the consensus view. There remains a deficiency of evidence supporting this application, however, and no study has confirmed any survival benefit or sustained improvement in functional status. Of note, several uncontrolled studies suggest that days of hospital use may be reduced after initiation of NPPV in these patients, but confirmatory studies are pending. If NPPV is to be initiated in patients with severe stable COPD, a more difficult adaptation process should be anticipated than for patients with neuromuscular disease. Great care must be taken in selecting a proper mask and optimal ventilator settings, and patients usually require considerable reassurance and encouragement. Potential problems should be anticipated and prevented, if possible. With a patient and supportive approach and a willingness to devote time to the process, clinicians can help optimize the likelihood of success, but failure rates are apt to remain higher than for other forms of chronic respiratory failure until the patient subpopulations with COPD most likely to benefit from NPPV are better defined and improvements in mask and ventilator technology enhance tolerance rates.