# Unveiling the Respiratory Muscle Strength in Duchenne Muscular Dystrophy: The Impact of Nutrition and Thoracic Deformities, Beyond Spirometry

## TL;DR

This study explores how nutrition and chest deformities affect respiratory muscle strength in children with Duchenne muscular dystrophy, beyond standard lung tests.

## Contribution

The study introduces a combined approach using supine and upright spirometry with additional pressure measurements to better assess respiratory muscle strength in DMD patients.

## Key findings

- Supine FVC, MIP, MEP, and SNIP measurements are crucial for assessing respiratory muscle strength in DMD patients.
- Low BMI significantly correlates with reduced MIP, MEP, and SNIP values in DMD patients.
- Respiratory parameters decrease significantly in the supine position for both ambulatory and non-ambulatory DMD patients.

## Abstract

Background/Objectives: Duchenne muscular dystrophy (DMD) is the most prevalent progressive muscular dystrophy, and the guidelines recommend the regular assessment of respiratory muscle function. This study aimed to assess the relationship between maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP) and sniff nasal inspiratory pressure (SNIP) measurements and upright-supine spirometry parameters in children with DMD, the predictability of upright–supine spirometry in terms of diaphragm involvement, and the impact of nutrition on muscle strength. Methods: This prospective cross-sectional study examined patients with DMD by comparing upright and supine FVC, MIP, MEP, and SNIP measurements. The effects of the ambulatory status, kyphoscoliosis, chest deformity, and low BMI on respiratory parameters were investigated. Results: Forty-four patients were included in the study. The mean patient age was 10.8 ± 2.9 years. Twenty-five patients were ambulatory. A significant decrease in FVC, FEV1, and FEF25–75 values was detected in the supine position in both ambulatory and non-ambulatory patients (p < 0.05). All patients had low MIP, MEP, and SNIP measurements (less than 60 cm H2O). MIP, MEP, and SNIP values were significantly lower in patients with a low BMI than in those without (p < 0.05). Conclusions: To accurately assess respiratory muscle strength, supine FVC should be combined with upright FVC, MIP, MEP, and SNIP measurements. It is crucial to regularly screen patients for nutrition, as this can significantly affect respiratory muscle function during pulmonology follow-up.