Variability in Diaphragm Motion During Normal Breathing, Assessed With B-Mode Ultrasound

Abstract

STUDY DESIGN Clinical measurement, cross-sectional. OBJECTIVES To establish a set of normal values for diaphragm thickening with tidal breathing in healthy subjects. BACKGROUND Normal values for diaphragm contractility, as imaged sonographically, have not been described, despite the known role of the diaphragm in contributing to spinal stability. If the normal range of diaphragm contractility can be defined in a reliable manner, ultrasound has the potential to be used clinically and in research as a biofeedback tool to enhance diaphragm activation/contractility. METHODS B-mode ultrasound was performed on 150 healthy subjects to visualize and measure hemi-diaphragm thickness on each side at resting inspiration and expiration. Primary outcome measures were hemi-diaphragm thickness and thickening ratio, stratified for age, gender, and body mass index. Interrater and intrarater reliability were also measured. RESULTS Normal thickness of the diaphragm at rest ranged from 0.12 to 1.18 cm, with slightly greater thickness in men but no effect of age. Average ± SD change in thickness from resting expiration to resting inspiration was 20.0% ± 15.5% on the right and 23.5% ± 24.4% on the left; however, almost one third of healthy subjects had no to minimal diaphragm thickening with tidal breathing. CONCLUSION There is wide variability in the degree of diaphragm contractility during quiet breathing. B-mode ultrasound appears to be a reliable means of determining the contractility of the diaphragm, an important muscle in spinal stability. Further studies are needed to validate this imaging modality as a clinical tool in the neuromuscular re-education of the diaphragm to improve spinal stability in both healthy subjects and in patients with low back pain.

Ultrasonographic findings of the normal diaphragm: thickness and contractility

“…14 Boon et al suggested that a decrease in thickening ratio below 1.2 (DTF = 20%) may help to identify an abnormality. 8,9 Prior studies have shown a relationship of diaphragm thickness and body size and gender, similar to the findings in this study. 8,9 In our study, DTF was relatively unaffected by demographic factors compared with diaphragm thickness.…”

“…8,9 Prior studies have shown a relationship of diaphragm thickness and body size and gender, similar to the findings in this study. 8,9 In our study, DTF was relatively unaffected by demographic factors compared with diaphragm thickness. Although DTF was affected by age for the left side and by sex for the right side, the findings were not consistent for both sides and were minimal compared with thickness.…”

“…One large study on normal diaphragm values was done by Boon et al, who studied 150 healthy individuals in the USA. 8,9 In their study, the mean diaphragm thickness was 0.33 cm and the lower limit of the normal resting thickness was 0.15 cm, which are much larger than the reference values in …”

Ultrasonographic Assessment of Diaphragm Function in Critically Ill Subjects

“…Harper et al 96 described a mean thickening fraction of 20% during tidal breathing, without significant difference between right or left hemidiaphragm in mechanically ventilated subjects. Other authors reported how left hemidiaphragm measurements could not be consistently obtained, whereas right hemidiaphragm thickness measurements are highly reproducible, particularly after marking the location of the probe.…”

Effectiveness of Conservative Physical Therapy Treatment with and Without Diaphragmatic Strengthening Exercises in Non Specific Low Back Pain

“…[7] Bmode ultrasound appears to be a reliable means of determining the contractility of the diaphragm, an important muscle in spinal stability. [8] In a recent study, patients suffering from Chronic Low Back Pain (cLBP) improved significantly with breath therapy. [5] Nociceptive factors have a major role in acute pain conditions.…”