PAVIA, ITALY--Noninvasive mechanical ventilation (NIMV) produces immediate improvements in most patients with chronic obstructive pulmonary disease (COPD) and acute respiratory insufficiency, but about 20% of these patients go on to experience late failure, a new study has found.[1]

Continuing NIMV in patients who relapse may delay endotracheal intubation and lead to unnecessary morbidity and mortality.

"It is a common experience to detect a late failure of NIMV, but this problem was never really assessed before," study author Stefano Nava, MD, told PULMONARY REVIEWS.

"We also wanted to assess the role of preexisting comorbidities in patient prognosis," reported Dr. Nava, head of the Respiratory Intensive Care Unit at the Fondazione Salvatore Maugeri, in Pavia, Italy. Another study objective was to determine the best ventilatory approach in patients with late failure.

Study subjects included 186 consecutive COPD patients who were admitted to one of two ICUs following an episode of acute hypercapnic respiratory failure (defined as an acute decrease in pH to 7.34 or less, sudden increase in PaCO2 to more than 60 mm Hg, tachypnea and/or paradoxical abdominal movements, and severe dyspnea). The initial response to NIMV was successful in 137 patients; this group experienced improvements in symptoms and arterial blood gas results within the first few hours of beginning NIMV.

However, 31 of these patients (23%) experienced a second episode of acute respiratory distress after a mean 8.4 days of NIMV.

Three variables, all present on or before admission, appeared to predict the occurrence of late NIMV failure: functional limitations in activities of daily living, a low pH, and the presence of medical complications.

However, only the presence of metabolic complications--particularly hyperglycemia--was found to independently predict late failure.

During late failure, patients were given a choice between increasing the daily hours of NIMV or switching to endotracheal intubation.

The in-hospital mortality rate was much higher in patients who relapsed than in those in whom NIMV continued to be successful (68% vs 0%, respectively).

Among the patients with late failure who continued receiving NIMV, the in-hospital mortality rate was 92% (11/12); it was 53% (10/19) among those who agreed to endotracheal intubation.

Other than the type of ventilation administered after late failure, the authors were unable to identify any differences between the two groups that would have explained the difference in mortality. The leading causes of in-hospital death were pneumonia, shock, cardiac failure, pulmonary embolism, and multiple organ failure.

Among the patients who survived to hospital discharge, there were no differences in 90-day survival.

"It is apparent from our study that the preadmission clinical status and the presence of comorbidities are strong determinants of late NIMV failure," said Dr. Nava.

"Indeed, when this occurs in patients on NIMV, endotracheal intubation is preferable to increasing the daily hours of NIMV. The latter approach only delays necessary intubation and increases morbidity and mortality," said Dr. Nava.

--Stanley Nelson

Reference
1. Moretti M, Cilione C, Tampieri A, et al. Incidence and causes of noninvasive mechanical ventilation failure after initial success. Thorax. 2000;55:819-825.

Return to table of contents