DTF showed moderate correlation with ΔPoes and discriminated between exercise loads during noninvasive ventilation, whereas ITF did not correlate with ΔPoes or discriminate between exercise phases, suggesting ITF adds no value to DTF in healthy subjects.
Key Findings
Results
Diaphragm thickening fraction (DTF) showed a moderate correlation with tidal oesophageal pressure swing (ΔPoes) as a surrogate for respiratory effort.
Repeated measures correlation analysis revealed ρ = 0.419, p < 0.001 between DTF and ΔPoes.
38 healthy volunteers were included in the study.
Participants completed three exercise sets on a semi-recumbent cycle ergometer, each consisting of five randomised phases with different ventilatory settings.
ΔPoes was measured using a nasogastric balloon catheter as the reference standard for respiratory effort.
Results
Intercostal muscle thickening fraction (ITF) did not correlate with ΔPoes or with DTF.
ITF showed no statistically significant correlation with ΔPoes.
ITF also did not correlate with DTF.
Parasternal intercostal muscle thickening fraction was assessed by ultrasound in B-mode.
These findings were observed across different exercise loads and ventilatory settings during noninvasive ventilation.
Results
Both DTF and ΔPoes increased with exercise load and allowed discrimination between different exercise phases, but ΔPoes provided more accurate separation.
DTF and ΔPoes both discriminated between different exercise loads using Friedman's test analysis.
ΔPoes provided a more accurate separation between exercise phases compared to DTF.
ITF did not discriminate between exercise phases.
Three exercise sets with five randomised phases each were used to assess discrimination across varying respiratory demands.
Discussion
ITF may only be informative in the presence of diaphragmatic dysfunction, based on findings in healthy subjects.
In healthy subjects, the diaphragm is the primary driver of inspiratory effort, which may explain why intercostal muscles did not show measurable thickening fraction changes.
The authors hypothesize that ITF reflects accessory muscle recruitment, which would be more prominent when the diaphragm is dysfunctional.
The study population consisted of healthy volunteers with no contraindications to noninvasive ventilation, limiting generalizability to clinical populations.
The authors recommend further investigations in clinical populations to test hypotheses derived from this study.
Methods
The study design employed repeated measures correlation and Friedman's test to analyze associations and differences between ultrasound-derived muscle parameters and esophageal pressure.
38 individuals were included in a physiological study design.
Diaphragmatic and parasternal intercostal muscle thickening fractions were assessed by ultrasound in B-mode.
Each participant completed three exercise sets on a semi-recumbent cycle ergometer with five randomised ventilatory phases per set.
Repeated measures correlation was used to assess associations, while Friedman's test was used to assess differences between phases.