Noninvasive positive pressure ventilation (NPPV) refers to delivery of ventilatory support using a mechanical ventilator connected to a mask or mouthpiece instead of an endotracheal tube. In the past 10 years, there has been a resurgence in the use of NPPV because of technologic advances and the emergence of clinical trials evaluating its use. In their review, Rabatin and Gay describe equipment, techniques and complications, and examine indications for application.
NPPV can be delivered using a volume or pressure-cycled ventilator, a bilevel positive airway pressure ventilator or a continuous positive airway pressure (CPAP) device. Several manufacturers make portable devices that are easy to use. Tubing connects the ventilator to a noninvasive interface. Options for the interface include a mouthpiece, full-face mask, nasal mask and “nasal pillows” that fit into the nostrils. Complications include nasal congestion, facial skin reddening, eye irritation, nasal bridge ulceration, aspiration and gastric distention.
Patients with acute respiratory failure related to chronic obstructive pulmonary disease (COPD) or other mechanisms of carbon dioxide retention did notably well in studies evaluating NPPV effectiveness. If NPPV is initiated before the onset of severe symptoms, studies show decreases in mortality, length of stay in the hospital, incidence of complications and need for use of an endotracheal tube in these patients.
NPPV fared well in a trial comparing it with invasive ventilation in patients with acute respiratory failure. NPPV was shown to be as effective as invasive ventilation in improving gas exchange measurements in the first hour of ventilation. Total complications and intensive care unit (ICU) length of stay were less in the NPPV group. Studies of CPAP versus oxygen in patients with cardiogenic pulmonary edema showed that CPAP reduces hypercapnia, decreases ICU length of stay and the need for intubation, and improves oxygenation. Studies assessing the usefulness of NPPV in patients with status asthmaticus are currently underway.
NPPV is widely accepted as the ventilatory mode of choice in patients with chronic respiratory failure related to neuromuscular disease, thoracic deformities and idiopathic hypoventilation. Its use eliminates the need for tracheostomies and has improved many patient-oriented measurements. NPPV is indicated for use in patients with neuromuscular disorders who exhibit morning headache, daytime hypersomnolence, sleep difficulties or cognitive dysfunction. In the absence of symptoms, NPPV is recommended when the partial pressure of alveolar carbon dioxide (PaCO2) is higher than 45 mm Hg or when the partial pressure of arterial oxygen (PaO2) is less than 60 mm Hg on a morning blood gas measurement.
The role of NPPV in patients with chronic stable COPD is unclear, with some studies showing benefit and others not. Poor patient compliance was reported in studies not showing positive results. Benefits occurred in patients with more severe gas exchange abnormalities. NPPV clearly represents an important addition to the techniques of managing respiratory failure. It has a growing role that will continue to expand depending on the results of current clinical trials.