Evaluation of Diaphragmatic Dysfunction in Mechanically Ventilated Critically Ill Subjects

We sought to evaluate the prevalence and factors associated with diaphragmatic dysfunction using bedside ultrasound in critically ill subjects undergoing invasive mechanical ventilation in pressure-support ventilation (PSV) mode.

This cross-sectional study included 56 ICU subjects invasively ventilated for at least 24 h in PSV mode. Diaphragm excursion (DE) and thickening fraction (TF) were measured by ultrasound. DE < 1.0 cm and TF < 15% or > 30% were used to define DD. Clinical variables, ventilatory parameters, and comorbidities were analyzed. Poisson regression was used to identify independent factors associated with the outcome.

Fifty-six ICU subjects receiving mechanical ventilation in PSV mode were assessed. DD based on reduced excursion was identified in 37.5% of cases, while TF abnormalities were present in 57.1%. Reduced DE was significantly associated with neoplastic disease (P < .001), lower tidal volume (P = .003), superficial sedation (P < .001), and longer duration of intubation (P = .047). Abnormal TF was associated with cardiovascular disease (P = .046) and elevated heart rate (P = .046). In multivariate analysis, cardiovascular disease (prevalence ratio 1.71, 95% CI: 1.00-2.84, P = .037), heart rate (P = .02), and ICU stay (P = .02) remained independently associated with abnormal TF. No significant correlation was observed between DE and TF (P = .78).

DD was common in invasively ventiled subjects, with distinct predictors depending on the ultrasound parameter used. Bedside ultrasound is a valuable, noninvasive tool for identifying DD and optimizing ventilatory strategies in the ICU.