Comparative Effectiveness

Noninvasive positive pressure ventilation improves COPD patient outcomes

Patients with acute respiratory failure due to severe worsening of chronic obstructive pulmonary disease (COPD) or congestive heart failure have improved outcomes, including mortality and intubation rates, with noninvasive positive pressure ventilation (NPPV) compared to supportive care (hospital support without invasive ventilation) alone, according to a new research review. In the United States, millions of patients are admitted to intensive care each year because of acute respiratory failure. This condition is severe enough to require life support with invasive mechanical ventilation for approximately 800,000 Americans a year, many of whom do not survive. NPPV is increasingly recognized as an alternative to conventional mechanical ventilation for treating acute respiratory failure, and may offer several benefits with minimal side effects for patients suffering from COPD.
Current evidence suggests that NPPV offers potential benefits for patients with acute respiratory failure who are postoperative or post-transplant. In select populations it may facilitate weaning from invasive ventilation, or prevent recurrent respiratory failure after a breathing tube is removed. These findings are generally consistent with previous systematic reviews and clinical guidelines on NPPV. There is a need for more research in patient populations where NPPV has not been rigorously studied, and to better understand how clinician experience, setting, system resources, and patient characteristics affect treatment as part of routine clinical care.
Details on current research on the effectiveness of NPPV can be found in the evidence-based review, Noninvasive Positive Pressure Ventilation for Acute Respiratory Failure from the Effective Health Care Program of the Agency for Healthcare Research and Quality. To access this review and other materials that explore the effectiveness and risks of treatment options for various conditions, visit the Effective Health Care Program Web site, http://www.effectivehealthcare.ahrq.gov.

Executive Summary – Jul. 11, 2012

Noninvasive Positive-Pressure Ventilation (NPPV) for Acute Respiratory Failure

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Background

Acute respiratory failure is a life-threatening condition characterized by an inability to maintain normal levels of oxygen and/or carbon dioxide gas exchange due to dysfunction of the respiratory system. In its most basic sense, the respiratory system comprises a gas exchanging organ (lung) and a ventilatory pump (respiratory muscles and controllers, chest wall). Respiratory failure is classified based on failure of one or both of these elements, as well as the timing of such failure. Acute respiratory failure develops over minutes to several days. Respiratory failure is deemed chronic when derangements occur over several days or longer. Acute-on-chronic respiratory failure occurs when a patient with chronic respiratory failure suffers an acute deterioration in gas exchange; this is most commonly seen in patients with severe chronic obstructive pulmonary disease (COPD).
The epidemiology of acute respiratory failure is not fully known. In the United States, millions of patients are admitted to the intensive care unit (ICU) each year, and acute respiratory failure is the most common cause.¹ Acute respiratory failure is severe enough to require life support with invasive mechanical ventilation for approximately 800,000 Americans a year, a high proportion of whom do not survive the episode.² Epidemiological studies have estimated the annual incidence of acute respiratory failure to be between 77.6 and 430 patients per 100,000.^1,3-5 The estimated health care costs related to critical care are approximately 0.7 percent of the annual gross domestic product, and the human and financial costs are only expected to increase with an aging population.^6-9
Supplemental oxygen is a mainstay of therapy for acute respiratory failure. In severe cases, acute respiratory failure requires respiratory support with invasive mechanical ventilation. Invasive ventilation (also known as conventional mechanical ventilation) is a form of life support in which positive pressure delivers a mixture of air and oxygen through an endotracheal or tracheostomy tube to central airways, which then flows distally to the alveoli. Despite the benefits of invasive ventilation in patients with respiratory failure, up to 40 percent of such patients die in the hospital; some of these deaths are directly attributable to the complications of invasive ventilation and artificial airways.^10-13 In addition, many survivors of acute respiratory failure require prolonged invasive ventilation and suffer persistent decrements in quality of life and functional independence.^14-16
An increasingly recognized option in the management of selected cases of acute respiratory failure is to employ noninvasive positive-pressure ventilation (NPPV). NPPV refers to a form of mechanical support in which positive pressure delivers a mixture of air and oxygen throughout the respiratory tree via a noninvasive interface. Patient-ventilator interfaces for NPPV include a face mask, nasal mask or plugs, or a helmet that covers the head. NPPV collectively includes several modalities of noninvasive ventilation, which can be delivered via a standard ICU ventilator or a portable device. Continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BPAP) are the two most commonly used modes of NPPV. CPAP is applied throughout the respiratory cycle of a spontaneously breathing patient and is physiologically identical to constant positive end-expiratory pressure. BPAP delivers two pressure levels according to the respiratory cycle and improves ventilation, oxygenation, and alveolar recruitment. BPAP provides both an inspiratory positive airway pressure and a continuous expiratory positive airway pressure, and the difference between these reflects the volume of air displaced with each breath. NPPV can provide modes nearly identical to standard ICU ventilators, such as pressure, volume, assist control, or even proportional assist ventilation.
The use of NPPV for support during the treatment of respiratory failure is attractive because it does not require either endotracheal intubation or moderate and/or deep sedation and can be safely initiated or discontinued as needed. It is also associated with few of the nosocomial complications recognized with endotracheal intubation, such as ventilator-associated pneumonia, critical illness-associated weakness, pneumothorax, delirium, and infections associated with the invasive monitoring typically required during invasive life support.^11,14 NPPV is not appropriate for some patients, such as those with cardiopulmonary arrest or shock, where greater airway control is required, or those with facial trauma, where the interface (e.g., mask) cannot be used appropriately.
NPPV has been evaluated in a large number of trials, often with clinically important benefits, but use of NPPV remains highly variable across institutions and geographical regions.^17-21 Surveys in the United States have shown high variability in estimated use across hospitals.²¹ Barriers to use include a lack of physician knowledge, low rates of perceived efficacy, lack of standard protocols and team-based care at some hospitals, and, among older clinicians, little training or experience with NPPV.²² A specific knowledge gap is uncertainty about the efficacy of NPPV for patients with acute respiratory failure for conditions other than COPD or acute cardiogenic pulmonary edema (ACPE). In addition, NPPV is a resource-intensive modality and requires a substantial amount of training and experience to implement successfully. As a result, some experts have questioned whether the benefits of NPPV seen in highly specialized settings are replicated in routine practice.

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