Relationships between diaphragm ultrasound, spirometry, and respiratory mouth pressures in children

Relationship Between Diaphragm Thickness, Thickening Fraction, Dome Excursion, and Respiratory Pressures in Healthy Subjects: An Ultrasound Study

PURPOSE

Diaphragm ultrasonography is used to identify causes of diaphragm dysfunction. However, its correlation with pulmonary function tests, including maximal inspiratory (MIP) and expiratory pressures (MEP), remains unclear. This study investigated this relationship by measuring diaphragm thickness, thickening fraction (TF), and excursion (DE) using ultrasonography, and their relationship to MIP and MEP. It also examined the influence of age, sex, height, and BMI on these measures.

METHODS

We recruited healthy Japanese volunteers and conducted pulmonary function tests and diaphragm ultrasonography in a seated position. Diaphragm ultrasonography was performed during quiet breathing (QB) and deep breathing (DB) to measure the diaphragm thickness, TF, and DE. A multivariate analysis was conducted, adjusting for age, sex, height, and BMI.

RESULTS

Between March 2022 and January 2023, 109 individuals (56 males) were included from three facilities. The mean (standard deviation) MIP and MEP [cmH2O] were 72.2 (24.6) and 96.9 (35.8), respectively. Thickness [mm] at the end of expiration was 1.7 (0.4), TF [%] was 50.0 (25.9) during QB and 110.7 (44.3) during DB, and DE [cm] was 1.7 (0.6) during QB and 4.4 (1.4) during DB. Multivariate analysis revealed that only DE (DB) had a statistically significant relationship with MIP and MEP (p = 0.021, p = 0.008). Sex, age, and BMI had a statistically significant influence on relationships between DE (DB) and MIP (p = 0.008, 0.048, and < 0.001, respectively).

CONCLUSION

In healthy adults, DE (DB) has a relationship with MIP and MEP. Sex, age, and BMI, but not height, are influencing factors on this relationship.

Deterioration of Cough, Respiratory, and Vocal Cord Functions in Patients with Multiple System Atrophy

The purpose of this study was to clarify changes in cough function in patients with multiple system atrophy (MSA). Seventeen probable patients with MSA were studied. Peak cough flow (PCF), respiratory function (percentage of vital capacity, percentage of forced vital capacity, and percentage of predicted forced expiratory volume in one second), respiratory muscle strength (percentage of maximal inspiratory mouth pressure and percentage of maximal expiratory mouth pressure), and maximum phonation time (MPT) were assessed. Walking ability, disease duration, possibility of air stacking, Unified MSA Rating Scale (UMSARS), and Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III were also assessed. Data were separately analyzed for ambulatory and non-ambulatory groups categorized by Functional Ambulation Categories. PCF, respiratory function, respiratory muscle strength, and MPT were significantly lower in the non-ambulatory group than in the ambulatory group. On the other hand, no correlation between PCF and disease duration was observed. A significant number of patients in the non-ambulatory group were unable to hold their breath. The UMSARS and MDS-UPDRS Part III in the non-ambulatory group were significantly higher than in the ambulatory group. It was concluded that ambulatory dysfunction is associated with the decline of cough function and respiratory-related function in patients with MSA.

Diaphragm excursion correlates with performance and ventilation on the 6-min walk test in children with sickle cell disease

INTRODUCTION

Diaphragm function may be impaired in children with sickle cell disease (SCD). We hypothesized that diaphragm function is related to performance and ventilation on the 6-min walk test (6MWT).

METHODS

Respiratory muscle testing, diaphragm ultrasonography, and the 6MWT with portable gas analysis were performed on children with SCD and age- and sex-matched controls.

RESULTS

Fourteen children with SCD were enrolled. Comparisons were made between nine children with SCD (9.89  ± $\pm $  2.93 years) and nine controls (10.33  ± $\pm $  2.35 years). Diaphragm thickness at total lung capacity, thickening fraction, and excursion time during quiet breaths and deep breaths (DB), all normalized by forced vital capacity, were greater in children with SCD ( p < $p\lt $ 0.05 for all). 6MWT distance was shorter in children with SCD (450.87  ± $\pm $  74.2 m vs. 579.22 ± $\pm $ 72.46 m, p = $p=$ 0.01). Tidal volume ( V T ${V}_{T}$ ), minute ventilation ( V ˙ E ${\dot{V}}_{E}$ ), and oxygen consumption ( V ˙ O 2 ${\dot{V}}_{{O}_{2}}$ ) were also lower ( p < $p\lt $ 0.05 for all). DB excursion correlated positively with 6MWT distance ( r = $r=$ 0.648, p = $p=$ 0.023) and negatively with rate of perceived exertion (RPE) ( r = $r=$ -0.759, p = $p=$ 0.003). RPE correlated negatively with distance ( r = $r=$ -0.680, p = $p=$ 0.015). DB excursion time correlated positively with distance ( r = $r=$ 0.611, p = $p=$ 0.035), V T ${V}_{T}$ ( r = $r=$ 0.770, p = $p=$ 0.009), V ˙ E ${\dot{V}}_{E}$ ( r = $r=$ 0.736, p = $p=$ 0.015), and V ˙ O 2 ${\dot{V}}_{{O}_{2}}$ ( r = $r=$ 0.751, p = $p=$ 0.012).

CONCLUSIONS

Increased diaphragm excursion may be a strategy used to relieve air hunger while longer excursion time may reflect compensations to increase lung recruitment. Further studies are needed to better understand how these mechanisms affect exercise tolerance in children with SCD.