Evaluation of Diaphragmatic Dysfunction in Mechanically Ventilated Critically Ill Subjects

Background: 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. Methods: 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. Results: 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). Conclusions: 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.