Key Point

Noninvasive ventilation may avoid intubation and decrease complications in patients with acute respiratory failure who need mechanical ventilation. When given prophylactically after extubation, noninvasive ventilation may prevent respiratory failure and improve survival.

MADRID AND BARCELONA—Three recent studies appear to confirm the usefulness of noninvasive ventilation (NIV) in the critically ill. In the first study, Honrubia et al showed that NIV reduced the need for conventional mechanical ventilation in acute respiratory failure with the possible exception of pneumonia-related cases.¹

"We also found a nonsignificant trend of reduction in ICU and hospital mortality, together with fewer complications during ICU stay," the study authors added. Moreover, compared to conventional ventilation, NIV required less therapeutic intervention during the first few days and did not increase the nursing workload.

The second study, a meta-analysis of NIV in patients with acute cardiogenic pulmonary edema, produced similar results.² "Our meta-analysis demonstrated an overall reduction in mortality of 45% and in the need for intubation of 57% with NIV compared to conventional oxygen therapy," said lead author Josep Masip, MD, Director of the ICU at the Hospital Dos de Maig Consorci Sanitari Integral, a community hospital in Barcelona. "NIV should be considered a first-line treatment for acute cardiogenic pulmonary edema," he told Pulmonary Reviews.

The effect of NIV prophylaxis on the risk of extubation failure was evaluated in the third study.³ "In mechanically ventilated patients with chronic respiratory disorders and hypercapnia who tolerate a spontaneous breathing trial with a T-piece, 24 hours of NIV prophylaxis immediately after extubation results in a reduced incidence of respiratory failure and improved survival," related lead author Miquel Ferrer, MD. Dr. Ferrer is a Consultant Physician in the Respiratory Intensive and Intermediate Care Unit at the Hospital Clinic in Barcelona.

NIV IN ACUTE RESPIRATORY FAILURE

The 64 patients with acute respiratory failure in the Honrubia et al study were randomized to conventional mechanical ventilation or NIV through a face mask. The NIV group received pressure support (adjusted to maintain a baseline tidal volume of 5 to 7 mL/kg) and positive end-expiratory pressure; success was defined as the ability to breathe spontaneously for at least 48 hours after the withdrawal of NIV.

Of the 31 patients in the NIV group, 18 (58%) were intubated, for a relative reduction in the risk of intubation of 43% compared to conventional ventilation. The relative risks of ICU and hospital mortality were reduced by 47% and 24%, respectively, in the NIV group, although these reductions did not achieve significance.

There were no differences between groups in complication rates, ventilation times, lengths of stay, or the amount of direct nursing care needed. However, the score on the Therapeutic Intervention Scoring System–28, a tool for measuring the nursing workload, was lower in the NIV group on the first day of ventilation and when averaged over the first three days.

Because the inclusion criteria did not preclude the use of NIV and the study protocol assured a 100% intubation rate in the conventional ventilation group, it is not surprising that NIV significantly reduced the need for intubation, stated Garpestad and Hill in an editorial.⁴

NIV META-ANALYSIS

For their meta-analysis, Dr. Masip and colleagues searched MEDLINE, EMBASE, and the Cochrane databases for randomized controlled trials and systematic reviews of NIV for acute cardiogenic pulmonary edema. The search covered January 1, 1988, to October 31, 2005, and yielded 559 papers. Of these, 15 studies involving a total of 727 patients with acute cardiogenic pulmonary edema were included in the meta-analysis.

Although NIV decreased overall mortality relative to oxygen therapy, the decline was significant for continuous positive airway pressure (CPAP) but not for bilevel noninvasive pressure support ventilation (NIPSV); a nonsignificant trend toward a 40% mortality decrease was seen with the latter. However, compared to oxygen, both types of NIV significantly reduced the need for intubation—by 60% and 49%, respectively.

No differences in mortality or intubation rates were observed when the authors analyzed the studies that directly compared the two types of NIV. "We also found that some trials showed faster improvement in subrogate end points such as oxygenation or dyspnea score using NIPSV instead of CPAP," Dr. Masip told Pulmonary Reviews.

Dr. Masip concluded that almost all patients with acute cardiogenic pulmonary edema may receive CPAP on admission. Administration of NIPSV may be equally useful at that time, but only by teams experienced with that technique, he said.

PREVENTION OF EXTUBATION FAILURE

To evaluate the ability of early NIV to prevent extubation failure, Dr. Ferrer and coworkers prospectively randomized 162 mechanically ventilated patients to 24 hours of NIV or to conventional oxygen therapy following extubation. While all of the patients tolerated a spontaneous breathing trial after the acute phase of illness, they were considered to be at increased risk for extubation failure due to older age, a high APACHE II score, facial or cranial trauma, or other factors.

The extubation failure and ICU mortality rates were lower in the NIV group than in the oxygen therapy group (16% vs 33% and 3% vs 14%). Ninety-day survival and the ICU and hospital lengths of stay were not significantly different between groups. When the patients were stratified according to the presence or absence of hypercapnia during the spontaneous breathing trial, NIV significantly improved ICU mortality and 90-day survival in the hypercapnic group.

"If our results are confirmed by a new randomized trial in this specific population, a prophylactic postextubation course of noninvasive ventilation should be incorporated into the clinical practice guidelines for the management of these patients," Dr. Ferrer told Pulmonary Reviews. "This would improve the survival of a subset of patients who otherwise have very bad medium-term survival."

—Timothy Begany

References
1. Honrubia T, López FJG, Franco N, et al. Noninvasive vs conventional mechanical ventilation in acute respiratory failure: a multicenter, randomized controlled trial. Chest. 2005;128:3916-3924.
2. Masip J, Roque M, Sánchez B, et al. Noninvasive ventilation in acute cardiogenic pulmonary edema: systematic review and meta-analysis. JAMA. 2005;294:3124-3130.
3. Ferrer M, Valencia M, Nicolas JM, et al. Early noninvasive ventilation averts extubation failure in patients at risk: a randomized trial. Am J Respir Crit Care Med. 2006;173:164-170.
4. Garpestad E, Hill N. Noninvasive ventilation for acute respiratory failure: but how severe? Chest. 2005;128: 3790-3791.

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