Validation of a novel point-of-care ultrasound method to assess diaphragmatic excursion.

Introduction: Point-of-care ultrasound can assess diaphragmatic function and rule in or rule out paresis of the diaphragm. While this is a useful bedside tool, established methods have significant limitations. This study explores a new method to assess diaphragmatic motion by measuring the excursion of the uppermost point of the zone of apposition (ZOA) at the mid-axillary line using a high-frequency linear ultrasound probe and compares it with two previously established methods: the assessment of the excursion of the dome of the diaphragm (DOD) and the thickening ratio at the ZOA.

Methods: This is a single-centre, prospective comparative study on elective surgical patients with normal diaphragmatic function. Following research ethics board approval and patient written consent, 75 elective surgical patients with normal diaphragmatic function were evaluated preoperatively. Three ultrasound methods were compared: (1) assessment of the excursion of the DOD using a curvilinear probe through an abdominal window; (2) assessment of the thickening fraction of the ZOA; and (3) assessment of the excursion of the ZOA. The last two methods performed with a linear probe on the lateral aspect of the chest.

Results: Seventy-five patients were studied. We found that the evaluation of the excursion of the ZOA was more consistently successful (100% bilaterally) than the evaluation of the excursion of the DOD (98.7% and 34.7% on the right and left sides, respectively). The absolute values of the excursion of the ZOA were greater than and well correlated with the values of the DOD.

Conclusion: Our preliminary data from this exploratory study suggest that the evaluation of the excursion of the ZOA on the lateral aspect of the chest using a linear probe is consistently successful on both right and left sides. Future studies are needed to establish the distribution of normal values and suggest diagnostic criteria for diaphragmatic paresis or paralysis.

Trial registration number: NCT03225508.