Chest
Volume 128, Issue 3, September 2005, Pages 1657-1666
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Clinical Investigations in Critical Care
Noninvasive Positive Pressure Ventilation in Patients With Acute Exacerbations of COPD and Varying Levels of Consciousness

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Study objectives

A severely altered level of consciousness (ALC) has been considered a contraindication to noninvasive positive pressure ventilation (NPPV). We compared the clinical outcome of patients with acute respiratory failure (ARF) due to COPD exacerbations and different degrees of ALC.

Design

A 5-year case-control study with a prospective data collection.

Setting

Respiratory Monitoring Unit.

Patients

Eighty of 153 consecutive COPD patients requiring NPPV for ARF were divided into four groups, which were carefully matched for the main physiologic variables, according to the level of consciousness assessed with the Kelly-Matthay Score, in which 1 is normal (control subjects) and 6 is severely impaired.

Measurement and results

Changes from baseline in arterial blood gas (ABG) levels and Kelly score, the rate and causes of NPPV failure, the rate of nosocomial pneumonia, and the 90-day mortality rate were compared. NPPV significantly improved ABG levels and Kelly score in all groups after 1 to 2 h. NPPV failure (Kelly score 1 = 15%; Kelly score 2 = 25%; Kelly score 3 = 30%; Kelly score > 3 = 45%) and 90-day mortality rate (Kelly score 1 = 20%; Kelly score 2 = 35%; Kelly score 3 = 35%; Kelly score > 3 = 50%) significantly increased with the worsening of the level of consciousness. Using a multivariate analysis, the acute nonrespiratory component of the acute physiology and chronic health evaluation (APACHE) III score, and baseline pH independently predicted baseline Kelly score. After 1 to 2 h of NPPV, changes in the Kelly score were associated with those in pH. No correlation was found with Paco2.

Conclusions

This study confirms that NPPV may be successfully applied to patients experiencing COPD exacerbations with milder ALCs, whereas the rate of failure in patients with severely ALCs (ie, Kelly score > 3) is higher, even though better than expected, so that an initial and cautious attempt with NPPV may be performed even in this latter group. Changes in the level of consciousness induced by NPPV are not correlated with those in Paco2.

Section snippets

Materials and Methods

This was an observational matched case-control study with prospectively collected data that was performed in patients who received NPPV for treatment of ARF due to COPD exacerbation, in our Respiratory Monitoring Unit,17 which is located within the Respiratory Ward of Arezzo “S. Donato” Hospital, between January 1998 and January 2003. The study protocol was approved by the local ethics committee of our hospital, and the study was performed in accordance with the ethical standards laid down in

Results

During the study period, 685 patients with acute decompensation of COPD were admitted to our unit; most of them improved quickly with medical therapy (485 of 685 patients; 70.8%). Among the remaining 200 eligible patients with ARF, 32 (16%) were excluded from the study because of the need for urgent ETI, and 15 (7.5%) were excluded because of their refusal of NPPV. The remaining 153 patients received NPPV a median time of 9.0 h (IQR, 1.50 to 69.75 h) after admission into our unit; 60 of them

Discussion

This is the first case-control study performed in patients experiencing acute exacerbations of COPD that was aimed at evaluating the efficacy of NPPV in patients with increasing degrees of ALC compared to fully alert subjects. The application of NPPV was able to quickly improve gas exchange and neurologic status in the large majority of patients, irrespective of the severity of the ALC. However, while in patients with mild-to-moderate ALC (Kelly score, ≤ 3) NPPV was highly successful in terms

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