Prahlad S, Chockalingam P, Soundararajan DK.
Ultrasonographic Assessment of Diaphragmatic Inspiratory Amplitude and Its Association with Postoperative Pulmonary Complications in Upper Abdominal Surgery: A Prospective, Longitudinal, Observational Study. 
Indian J Crit Care Med
2021;
25
(9):1031-1039.