Diaphragmatic Dysfunction Is Characterized by Increased Duration of Mechanical Ventilation in Subjects With Prolonged Weaning

Abstract

BACKGROUND:

Diaphragmatic dysfunction is often underdiagnosed and is among the risk factors for failed weaning. The purpose of this study was to determine the prevalence of diaphragmatic dysfunction diagnosed by B-mode ultrasonography and to determine whether prolonged weaning subjects with diaphragmatic dysfunction have increased duration of mechanical ventilation compared with those without diaphragmatic dysfunction.

METHODS:

This was a prospective observational study in mechanically ventilated subjects who failed ≥3 spontaneous breathing trials or required >7 d of weaning after the first spontaneous breathing trial. Diaphragm thickness was measured in the zone of apposition using a 6–13-MHz ultrasound transducer during a spontaneous breathing trial. The diaphragmatic thickening fraction was calculated as a percentage from the formula: (Thickness at peak inspiration − thickness at end expiration)/thickness at end expiration. Intra-observer and inter-observer reliability were also evaluated.

RESULTS:

Forty-one subjects (24 males; 62.2 ± 15.9 y old) were included in the study. Of these, the prevalence of ultrasonographic diaphragmatic dysfunction (defined as diaphragmatic thickening fraction of <20% with inspiration) was 34.1% (n = 14). Subjects with diaphragmatic dysfunction had longer ventilation time after inclusion (293.4 ± 194.8 vs 145.1 ± 101.3 h, P = .02) and ICU stay (29.2 ± 11.4 vs 22.4 ± 7.7 d, P = .03) than subjects without diaphragmatic dysfunction.

CONCLUSIONS:

Diaphragmatic dysfunction as assessed by B-mode ultrasonography is common in subjects with prolonged weaning. Subjects with such diaphragmatic dysfunction show longer mechanical ventilation durations and ICU stays.