Noninvasive ventilation for hypercapnic respiratory failure in COPD: Encephalopathy and initial post support deterioration of pH and PaCO2 may not predict failure

A b st ra ct Objectives: To correlate the degree of encephalopathy, baseline values of PaCO and pH, and their early 2 response to NIV with eventual in-hospital outcome in patients of severe acute-on-chronic hypercapnic respiratory failure in COPD. Design: Retrospective review. Setting: Intensive care unit. Material and methods: 24 episodes of acute exacerbation of COPD in 17 patients (10 females, 7 males) with a mean age of 59.5 years (range 48 – 82) where NIV was initiated. Data collected: encephalopathy score at base­ line and at 24 hours, respiratory rate, breathing pattern, serial arterial blood gases, duration of NIV support per day and hospital days. Results: All patients had severe hypercapnia (mean peak PaCO 89.0 mm Hg 2 ± 21; range 66-143), respiratory acidosis (mean nadir pH 7.24 ± 0.058, range 7.14 – 7.33) and tachypnoea (mean respiratory rate 29.5 ± 4.69/mt; range 24 – 40). In 17 episodes, altered mental state was present (encephalopathy score 1.92 ± 1.32, median 2.5). Clinically stable condition occurred over several days (mean 13± 9.6 days; range 5 – 40). Intubation was avoided in 22 out of 24 episodes (91.6%) despite significant initial worsening of PaCO and pH. Two patients died. The mean time on NIV was16.5 hours/day 2 (range 4 – 22). Conclusions: In selected patients of COPD with acute hypercapnic failure on NIV worsen­ ing PaCO and pH in the initial hours may not predict failure provided the level of consciousness and 2 respiratory distress improve.