Purpose: To evaluate the ability of a novel ultrasound (US) device, DiaMon, to monitor diaphragm movement via its proxy liver movement, and compare it with the respired flow measured with a flowmeter, in awake and healthy volunteers. We wanted to (1) establish the optimal anatomical position for attaching the DiaMon device to the abdominal wall, and (2) evaluate the accuracy of continuous monitoring of respiratory frequency.
Methods: Thirty healthy subjects were recruited. The DiaMon probe was applied subcostally in four different positions with the subjects in five different postures. The subjects breathed tidal volumes into a spirometer for 30-60 s with the DiaMon recording simultaneously.
Results: The device detected a readable signal in 83-100% of the position/posture-combinations. The technical correlation between the two signals was highest in the anterior axillary-supine position (mean ± SD: 0.95 ± 0.03), followed by paramidline-supine (0.90 ± 0.09) and midclavicular-supine (0.89 ± 0.12). The frequency measurements yielded a mean difference of 0.03 (95% limits of agreement - 0.11, 0.16) breaths per minute in the anterior axillary-supine position.
Conclusion: The DiaMon device is able to detect liver movement in most subjects, and it measures breathing frequency accurately.
Keywords: Diaphragm; Non-invasive; Respiration; Ultrasound.