Standardization of Sonographic Diaphragm Thickness Evaluations in Healthy Volunteers

BACKGROUND: B-mode ultrasound can be used to measure diaphragm thickness at the zone of apposition. We believe it is necessary to develop normal values for diaphragm thickness at rest in a large group of healthy subjects and compare them with international results. METHODS: Ultrasound measurements of diaphragm thickness at expiratory rest were taken in 109 healthy individuals, with results stratified by sex, body mass index, and thorax circumference. The following methods were used for analysis and interpretation. Multivariable databases with descriptive statistical analyses were made. The Pearson chi-square test was used to evaluate the distribution between variables. Additionally, mean and SD values were calculated. For standardization, the data were separated by sex within a 95% CI, and we calculated a Z test. A 95% CI was also constructed for proportion analyses. RESULTS: One hundred nine healthy volunteers were included in the study, and the correlation between the body mass index and thorax circumference values with a Pearson chi-square test resulted in an r = 0.69. Additionally, the average value of diaphragmatic thickness was 0.19 +/- 0.04 cm (95% CI 0.17-0.20 cm) for men and 0.14 +/- 0.03 cm (95% CI 0.13-0.15 cm) for women (P = .001). There was no relation between body mass index thorax circumference, and diaphragmatic thickness. CONCLUSION: Real-time ultrasound of the diaphragm is a simple, inexpensive, and portable imaging technique that can provide qualitative anatomical information. The findings in this study show that sonographic diaphragm evaluations can be applied to the general population.