NPPV has also been evaluated as a measure to prevent respiratory failure in patients at high risk for extubation failure. When applied immediately after extubation in patients with COPD and obesity, NPPV reduced reintubation rates and ICU mortality.3,4 In 2004, Esteban and colleagues examined NPPV in patients who had respiratory failure following extubation. In this setting, NPPV was ineffective at preventing reintubation and had no survival benefit.
In summary, NPPV may facilitate early extubation and prevent extubation failure in appropriate patients, such as those with COPD, but is unlikely to be beneficial and is not recommended in patients with existing respiratory failure after extubation.4,15
Immunosuppressed patients. A 2001 single-center, randomized-controlled trial by Holbert and colleagues demonstrated decreased intubation rates and mortality with the application of NPPV in immunosuppressed patients with hypoxemic respiratory failure, fever, and pulmonary infiltrates.16
In this study, immunosuppression occurred most commonly as a result of malignancy. In the group receiving NPPV alternating with oxygen (at least 45 minutes of NPPV alternated every three hours with periods of spontaneous breathing), the rate of subsequent intubation decreased to 46%, compared with 77% in those receiving oxygen alone. The mortality rate was 38% in the NPPV group, as compared with 69% in the standard treatment group.
Though the outcomes in immunocompromised patients with hypoxemia, fever, and pulmonary infiltrates were very poor (38% mortality even with NPPV), this small study and recent guidelines suggest a trial of NPPV in this population.4,16
Other indications. NPPV has been applied in multiple other clinical scenarios, including exacerbation of asthma, community-acquired pneumonia, acute lung injury, and bronchoscopy in hypoxemic patients. It has also been evaluated in the postsurgical period and in chest trauma. There are mixed and less robust data in these various applications, and larger controlled trials are lacking.
In asthma exacerbation, NPPV may improve dyspnea, but data regarding outcomes (intubation, mortality) are lacking. A 2005 Cochrane review concluded that data remain controversial due to insufficient evidence, and guidelines make no recommendations concerning NPPV in asthma exacerbation.4,17 Similarly, in community-acquired pneumonia without prior history of COPD, there is no major role for NPPV.1,3,4 Limited data suggest that NPPV lacks efficacy in preventing post-surgical respiratory failure, though it may be useful in treating existing respiratory failure or preventing intubation in patients following lung resection or abdominal surgery.1,4 In hypoxemic patients undergoing bronchoscopy, NPPV may improve oxygenation (lower respiratory rates and improved PaO2 to FiO2 ratios, compared with oxygen alone) as well as hemodynamics (minimizing the drop in mean arterial pressure). However, outcome data are lacking and the data set is small.4,18 In acute lung injury/acute respiratory distress syndrome, data are also limited, but NPPV appears to have a high failure rate and confers little benefit.1,4
Back to the Case
The patient was admitted to the hospital and placed on BiPAP for approximately 1.5 hours. The patient’s respiratory rate improved to 20/minute and he appeared increasingly comfortable and alert. A repeat ABG revealed improved hypercarbia and acidosis. He was continued on steroids and antibiotics and eventually was weaned from BiPAP and discharged home.
Bottom Line
NPPV is an effective method to decrease mortality, intubation rates, and duration of ICU stay in severe exacerbations of COPD, cardiogenic pulmonary edema, immunosuppressed patients with pulmonary infiltrates, and hypoxia, and as a bridge to extubation in COPD patients.
Dr. Kraynek is an internal medicine resident in the Department of Medicine at the University of Washington School of Medicine in Seattle. Dr. Best is assistant professor of medicine in the Division of General Internal Medicine at the University of Washington School of Medicine.