Chest
Volume 112, Issue 2, August 1997, Pages 472-477
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clinical investigations in critical care
The Effect of Sepsis on Breathing Pattern and Weaning Outcomes in Patients Recovering From Respiratory Failure

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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). WBC 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

Abbreviations

APACHE
acute physiology and chronic health evaluation
Cl
confidence interval
MICU
medical ICU
MIP
maximal inspiratory pressure
Pplt
static airway pressure
RVR
respiratory rate: tidal volume ratio
Tmax
maximal temperature
e
minute volume

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