Recently, evaluation of the diaphragm by means of ultrasound has become popular.1  The increase in diaphragm thickness during inspiration (thickening fraction) has been proposed as a noninvasive bedside measure of diaphragm function,2,3  although previous studies have reported wide variability between thickening, inspiratory effort, and transdiaphragmatic pressure.4–6  We hypothesized that the force-length and force-generating relationship in the diaphragm is altered by different positive end-expiratory pressure (PEEP) levels in patients with SARS-CoV-2.7 

We investigated the relationship between diaphragm thickening fraction and transdiaphragmatic pressure swing during noninvasive helmet continuous positive airway pressure. From March to December 2021, a total of 26 consecutive patients with laboratory-confirmed SARS-CoV-2 infection admitted to the intensive care unit of Santa Chiara Hospital (Trento, Italy) were prospectively enrolled. The study was approved by the ethics committee (Rep. Int. 282/2022), and written informed consent was obtained. At intensive care unit admission, according to the...

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