An Investigation into the Use of Ultrasound As a Surrogate Measure of Diaphragm Function

Purpose: Sonographic assessment of the diaphragm may be a surrogate for interpretation of diaphragm function in mechanically ventilated patients. This study aimed to determine the correlation between respiratory muscle function and diaphragm thickness in a healthy population.

Methods: A descriptive study was conducted. Diaphragm thickness was determined by sonographic measurement. Respiratory muscle strength, fatigue and endurance was determined using a mouth pressure manometer.

Results: 55 subjects with a mean (SD) age 21.16 ± 1.55 years were studied. Diaphragm thickness was moderately correlated with strength (r = 0.52; r=0.27; p < 0.001). Respiratory muscle fatigue was not correlated with thickness (r=-0.15; r=0.02; p = 0.29) or strength (r=-0.19; r=0.04; p = 0.16).

Conclusion: Diaphragm thickness was moderately correlated to strength but not to fatigue or endurance in healthy individuals. Sonography may be a surrogate measure of volitional respiratory muscle strength and requires confirmation in critically ill patients.