M-mode ultrasound for the detection of pneumothorax during helicopter transport

BackgroundThe presence of the sonographic sliding lung sign (SLS) is a sensitive indicator for the absence of a pneumothorax. The addition of M-mode ultrasound (US) can be a useful adjunct in detecting the SLS.ObjectiveThe objective of this study is to determine the feasibility of using M-mode US in evaluating the SLS during helicopter transport.MethodsA model simulating human lung was used during image acquisition. M-mode images of the SLS were obtained during 3 distinct phases of transport: without rotor rotation, with rotor rotation while on the ground, and at level flight. Four US-credentialed emergency physicians evaluated M-mode US tracings of the model along with examples from human lungs, both with and without pneumothorax, in random fashion.ResultsA total of 104 images were reviewed (26 images per reviewer). All of the M-mode images were correctly identified. Motion artifact was noted on the M-mode tracings taken during rotor rotation, which was greatest during level flight. The rotor artifact was not felt to affect the diagnostic utility of the M-mode US tracing.ConclusionM-mode US may be used successfully to detect the SLS during helicopter transport.