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.
- diagnostic techniques and procedures
- brachial plexus
Data availability statement
Data are available upon reasonable request.
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Presented at American Society of Regional Anesthesia and Pain Medicine Annual meeting, Hollywood, Florida, April 21, 2023.
Contributors DDC prepared the first draft of the manuscript and approved the final manuscript. AP is the PI, oversaw the data collection, data analysis, revised the manuscript, approved the final manuscript and is the guarantor of the study. LGA edited the manuscript, prepared the ultrasound figures and approved the final manuscript. KW conceived the study and wrote the study protocol. QL and EH performed the statistical analysis and prepared figures 4 and 5. JC performed the data collection, maintained study records, prepared all data for analysis and approved the final manuscript. VC was the senior author. He provided study infrastructure and research staff, assisted with protocol development, revised the manuscript and approved the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests AP performs consulting work for Fujifilm Sonosite.
Provenance and peer review Not commissioned; externally peer reviewed.
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