Ultrasound Analysis of Diaphragm Kinetics and the Diagnosis of Airway Obstruction: The Role of the M-Mode Index of Obstruction

Abstract Diaphragm motion in forced expiration can be analyzed using M-mode ultrasound in an anterior subcostal approach. Maximum expiratory diaphragmatic excursion (EDEMax ) and forced expiratory diaphragmatic excursion in the first second (FEDE1 ) are considered the physiopathological analogues of vital capacity (VC) and forced expiratory volume in the first second (FEV1 ). As the FEV1 /VC % ratio is used as a marker of obstruction, our aim was to determine if the ratio FEDE1 /EDEMax (M-mode index of obstruction [MIO]) differs between healthy subjects and patients with airway obstruction. One hundred twenty-four outpatients were examined by diaphragm ultrasound after spirometry. The MIO, expressed as the mean ± standard deviation (range), was 87.08 ± 6.64 (72.84–100) in the healthy group (N = 61) and 67.09 ± 12.49 (33.33–91.30) in the group with obstructed airways (N = 63). The difference between the two groups was significant ( p