Ultrasound Assessment of Diaphragm Thickness and Thickening: Reference Values and Limits of Normality When in a Seated Position

Abstract

Background: Diagnosing diaphragm dysfunction in the absence of complete paralysis remains difficult. The aim of the present study was to assess the normal values of the thickness and the inspiratory thickening of both hemidiaphragms as measured by ultrasonography in healthy volunteers while in a seated position.Methods: Healthy volunteers with a normal pulmonary function test were recruited. The diaphragmatic thickness was measured on both sides at the zone of apposition of the diaphragm to the rib cage during quiet breathing at end-expiration, end-inspiration, and after maximal inspiration. The thickening ratio, the thickening fraction, and the thickness at end-inspiration divided by the thickness at deep breathing were determined. The mean values and the lower and upper limits of normal were determined for men and women.Results: 200 healthy volunteers (100 men and 100 women) were included in the study. The statistical analysis revealed that women had a thinner hemidiaphragm than men on both sides and at the various breathing times studied. The lower limit of normality of the diaphragm thickness measured at end-expiration was estimated to be 1.3 mm in men and 1.1 mm in women, on both sides. The thickening fraction did not differ significantly between men and women. In men, it ranged from 60 to 260% on the left side and from 57 to 200% on the right side. In women, it ranged from 58 to 264% on the left side and from 60 to 229% on the right side. The lower limits of normality of the thickening fraction were determined to be 40 and 39% in men and 39 and 48% in women for the right and left hemidiaphragms, respectively. The upper limit for normal of the mean of both sides of the ratio thickness at end-inspiration divided by the thickness at deep breathing was determined to be 0.78 in women and 0.79 in men.Conclusion: The normal values of thickness and the indexes of diaphragmatic function should help clinicians with detecting diaphragm atrophy and dysfunction.

Association of diaphragm thickness and echogenicity with age, sex, and body mass index in healthy subjects

“…In agreement with previous studies, diaphragm thickness was larger in men than women 9,15,20 . The calculation of thickening ratio cancels out sex differences.…”

“…The larger variation in T max-insp compared to T end-exp is in accordance with other reports. 20 This may be attributed to variation in subjects' performance of the maneuver to take a deep breath and affects the level of diaphragm recruitment and the anatomical position of the diaphragm relative to the ultrasound probe.…”

“…21 In agreement with previous studies, diaphragm thickness was larger in men than women. 9,15,20 The calculation of thickening ratio cancels out sex differences. We also identified BMI as significant predictor of T end-exp and thickening ratio, but the size of this effect was small.…”

Diaphragm dysfunction after severe COVID-19: An ultrasound study

“…This observational study performed on patients suffering from persistent adverse health effects 3-4 months after severe COVID-19 pneumonia found that their diaphragm function was nonetheless essentially normal. The mean values of excursions and thicknesses were close to the normal values previously reported in healthy volunteers assessed while in a seated position (19,20). Furthermore, and as expected, men had larger excursions during deep breathing, and their hemidiaphragm thickness was increased compared to women.…”

Methods and Applications in Respiratory Physiology: Respiratory Mechanics, Drive and Muscle Function in Neuromuscular and Chest Wall Disorders

“…Ultrasound imaging of the diaphragm is a non-invasive means of measuring diaphragm thickness and inspiratory thickening because an increase in diaphragm thickness leads to inspiratory strength ( Roussos et al, 1979b ; Boussuges et al, 2021 ). When applied by experienced users it provides reproducible results, with good inter- and intra-observer reliability ( Cohn et al, 1997 ; Schepens et al, 2015 ).…”