The Science Journal of the American Association for Respiratory Care

2007 OPEN FORUM Abstracts

NONINVASIVE POSITIVE PRESSURE VENTILATION IN ACUTE RESPIRATORY FAILURE: A STUDY OF CLINICAL OUTCOME

S. Johnson1, A. Shenoy2, R. Davis3


Background
Noninvasive ventilation (NIV) is increasingly being used in the treatment of acute respiratory failure in patients with various causes. Our aim of this study is to analyze the clinical outcome in patients treated with noninvasive positive pressure ventilation (Bilevel Positive Airway Pressures-BiPAP) and to identify the determinants, which predict the success and failure of this technique.

Methods
Retrospective analysis of 57 patients who presented to our Multidisciplinary Intensive Care Unit (MICU) in acute respiratory failure due to various causes during the period 2004 to 2006 and treated with noninvasive positive pressure ventilation (NIPPV). Arterial blood gases were assessed immediately before (baseline) and during an initial 1 to 2 hour trial of NIPPV. Chest radiograph on first and third day of NIPPV, total duration of NIPPV treatment, MICU stay and total hospital stay were also taken in to consideration. Clinical outcomes were analyzed considering each NIPPV treatment as successful or failure according to survival and need for endotracheal intubation.
Results
Out of total 57 patients, only 53 patients were included in the analysis, since four patients got discharged against medical advice due to financial constraints.

Noninvasive mechanical ventilation (NIV) was successful in 35 episodes of acute respiratory failure-Group I (66.03%). 18 patients (33.9%) had failure in NIV – Group II, which was defined by the need for endotracheal intubation. The overall mortality was 13.2% (7 out of 53 patients).

The changes in arterial blood gas tension before and during the initial trial of NIV are shown in Figure1. An improvement in pH and PaCO2 after 1-2 hours has been shown to be associated with a successful out come from NIV. The level of PaO2 did not differ significantly between successful and unsuccessful cases.

The duration of NIV, ICU stay and hospital stay were compared between the two groups. The duration of ICU stay was shorter by 3.65 days in patients in whom NIV was successful.

Conclusion
An improvement in pH and a reduction in PaCO2 after 1-2 hours of NIV have been shown to be associated with a successful outcome from it. The effectiveness of NIV in improving PaCO2 and pH in initial hours could be used to predict whether the patients with acute respiratory failure could be successfully treated with NIV and also to avoid unnecessary delay in intubation of those who deteriorate on NIV.


Change in Blood Gas after NIV
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