The course of diaphragm atrophy in ventilated patients assessed with ultrasound: a longitudinal cohort study

Introduction: Mechanical ventilation and the effect of respiratory muscle unloading on the diaphragm cause ventilator-induced diaphragmatic dysfunction (VIDD). Atrophy of the diaphragmatic muscle is a major part of VIDD, and has a rapid onset in most animal models. We wanted to assess the clinical evolution and risk factors for VIDD in an adult intensive care unit (ICU) by measuring diaphragm thickness using ultrasound. Method: We performed a single-centre observational cohort study, including 54 mechanically ventilated patients. The right hemidiaphragm was measured daily at the zone of apposition on the midaxillary line. Results: Mean baseline thickness was 1.9 mm (SD +/- 0.4 mm), and mean nadir was 1.3 mm (SD +/- 0.4 mm), corresponding with a mean change in thickness of 32 % (95 % CI 27-37 %). Length of mechanical ventilation (MV) was associated with the degree of atrophy, whereas other known risk factors for muscle atrophy in an ICU were not. The largest decrease in thickness occurred during the first 72 hours of MV. Conclusions: Diaphragm atrophy occurs quickly in mechanically ventilated patients and can accurately be monitored using ultrasound. Length of MV, as opposed to other variables, is associated with the degree of atrophy.