The Effect of Sepsis on Breathing Pattern and Weaning Outcomes in Patients Recovering From Respiratory Failure

¹ From the Pulmonary and Critical Care Division, Bridgeport Hospital and Yale University School of Medicine, Bridgeport, Conn.

Objective: To determine the effects of sepsis on breathing pattern and weaning outcome in medical patients recovering from respiratory failure.

Design: Prospective, observational study.

Setting: Medical ICU of a 300-bed community teaching hospital.

Measurements: Patients were classified as having sepsis or not having sepsis on the first day of weaning. The respiratory rate:tidal volume ratio (RVR), maximal inspiratory pressure (MIP), respiratory system mechanics, minute volume, WRC count, and maximal temperature (Tmax) were recorded for the first day of weaning. Weaning was then conducted by the patients' primary physicians; weaning outcomes and days spent receiving mechanical ventilation were recorded.

Results: Sixty patients were studied over 64 separate ICU admissions. Twenty-five patients met criteria for sepsis and had a higher mean APACHE II (acute physiology and chronic health evaluation) score than patients without sepsis (mean±SE: 23.4±1.3 vs 18.7±1.0; p<0.05). Respiratory mechanics, age, and minute volumes were not different between patients with and without sepsis. Patients with sepsis had a higher RVR than patients without sepsis (94.3±10.1 vs 66.6±6.4 breaths/min/L; p<0.05) and tended to have a lower MIP (25.0±2.0 vs 31.0±2.3 cm H₂O; p=0.055). The MIP and RVR were moderately correlated (r=0.50, p<0.001). WRC count and Tmax did not correlate with RVR in the total population or in sepsis/nonsepsis subpopulations. First-day weaning success was higher in patients without sepsis (17/39=44%) than patients with sepsis (6/25=24%; odds ratio=2.4; 95% confidence interval=0.8 to 7.3). Patients with sepsis tended to require a longer duration of weaning (3.8±0.6 vs 2.5±0.5 days; p=0.1) and mechanical ventilation (7.4±1.0 vs 5.6±1.0 days; p=0.2) than patients without sepsis. Differences were not significant when patients were stratified by ICU admission APACHE II scores.

Conclusions: Patients recovering from sepsis breathe with a higher RVR, tend to have a lower MIP, and tend to be more likely to encounter first-day weaning failure compared to patients without sepsis. Our data also suggest that the severity of illness on ICU admission could explain some of these differences.

Key Words: diaphragm • mechanical ventilation • rapid shallow breathing • respiratory failure • respiratory muscles • sepsis • weaning parameters

Submitted on September 24, 1996
Accepted on January 16, 1997

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