Diaphragmatic thickness-lung volume relationship in vivo

Abstract

To characterize the relationship of changes in diaphragmatic thickness during contraction to changes in lung volume, we developed a technique to measure diaphragm thickness based on M-mode ultrasonography. First, diaphragmatic thickness was measured in situ at necropsy with ultrasound and verified by measuring the same resected segment of diaphragm by ruler (correlation coefficient = 0.93, slope = 0.97). The technique of imaging the diaphragm in living subjects was developed by using a 15-MHz transducer coupled to an M-mode echocardiograph. Ten normal male volunteers were studied while sitting. The ultrasound transducer was held between the ribs in the ninth lateral interspace, and tidal volume was measured by spirometry. The thickening fraction (TF) was calculated as TF = (thickness at peak inspiration - thickness at end expiration)/thickness at end expiration for each of a series of different sized breaths. The function, TF vs. lung volume, for a range of volumes was linear for each subject and had intrasubject reproducibility with intersubject variability. We conclude that diaphragmatic TF is related to function as determined by lung volume, and this may prove to be a useful technique for in vivo studies of diaphragmatic function.

B-Mode Ultrasound Assessment of Diaphragm Structure and Function in Patients With COPD

“…9 Th at study confi rmed the fi ndings of prior smaller studies and provided normal values for future comparative studies; however, we did not know whether these values could be applied to the population of patients with COPD. 5,[12][13][14][15] We hypothesized that patients with moderate COPD would demonstrate compensatory overuse hypertrophy of the diaphragm and that patients with severe air trapping would have impaired diaphragm contractility because of the displacement of the muscle and subsequent suboptimal length-tension relationship of the muscle fi bers, resulting in a decreased thickening ratio. Contrary to our hypotheses, our results show that patients with COPD have comparable diaphragm thickness and contraction to that of normal subjects.…”

Ultrasonographic evaluation of diaphragmatic motion.

“…18 A chronically paralyzed diaphragm is atrophic and does not thicken during inspiration. 19 On the opposite end, the resting diaphragm thickness is increased in young patients with Duchenne's muscular dystrophy and impaired respiratory muscle force.…”

Ultrasonographic Assessment of Diaphragm Function in Critically Ill Subjects

“…85 Ultrasonographic examination can also allow for the direct visualization of diaphragm thickness in its zone of apposition. 86 Thickening during active breathing has been proposed to reflect the magnitude of diaphragm effort, similar to an ejection fraction of the heart. 87 A number of recent studies have employed ultrasound to measure diaphragm thickness and inspiratory thickening in ventilated subjects.…”

“…The right hemidiaphragm can be visualized in the zone of apposition of the diaphragm to the rib cage with the probe placed in the midaxillary line, between the 8th and 10th intercostal space, as a 3-layered structure consisting of pleural and peritoneal (hyperecogenic) membranes and the hypoecogenic layer of muscle itself 86,91 (Fig. 3).…”