A new cross-sectional study assessing respiratory impairment characteristics in patients with Duchenne muscular dystrophy (DMD), a rapidly progressive and highly lethal hereditary muscle disease, identified different changing pulmonary function patterns in various stages of the disease for those aged between 6 and 18 years old. These findings provide a reference for the respiratory management of pediatric patients with DMD.1
Among 144 pediatric patients with DMD, 30% of the cohort exhibited abnormal pulmonary ventilation function, with restrictive ventilation dysfunction (48.94%) and/or small airway dysfunction (40.48%) as the most prevalent reported. The precent predicted values forced vital capacity (FVC%) and forced expiratory volume in the first second (FEV1%) had an increasing trend and reached a plateau before the age of 10 years, followed by a decreasing trend after the age of 10 years. After 7 years of age, investigators observed a decreasing trend in precent predicted values peak expiratory flow (P <.001) and forced mid-expiratory flow (FEF25%)(P = .001).
Top Clinical Takeaways
- Among pediatric patients with DMD, 30% showed abnormal pulmonary ventilation function, with distinct changing patterns in various respiratory parameters.
- PEF% and FEF25% were identified as potentially more sensitive markers for early respiratory impairment compared with traditional measurements like FVC% and FEV1%.
- The study underscores the importance of considering inspiratory function, and highlights a positive correlation between end-expiratory carbon dioxide levels and age in these patients.
Presented at the 2024 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, held March 3-6, in Orlando, Florida, the study collected data on patients with DMD aged 6-18 years from West China Second Hospital of Sichuan University between July 2023 and January 2024 were included in the analysis. Led by coauthor Huayan Xu, PhD, postdoctoral researcher at West China Second Hospital of Sichuan University, the investigators gathered information on clinical phenotypes, pulmonary function parameters, anthropometrics, and end-expiratory carbon dioxide (EtCO2). Following that, researchers analyzed the differences in respiratory function and related factors among different age groups using t-test, analysis of variance, and Pearson correlation analysis.
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Since PEF% and FEF25% were more sensitive than FVC% and FEV1% in responding to early respiratory impairment in DMD, authors noted that these measurements may be potentially used as novel monitoring markers for early respiratory impairment. Although investigators observed that maximal expiratory pressure (MEP) and maximal inspiratory pressure (MIP) both increased with age, the rate of increase slowed down significantly from 6 years onwards in patients. Additionally, authors noted that inspiratory function was more impacted than the expiratory function (MIP% IQ2 = 37.8%, IQ1-IQ3 = 30.8%-47.2%, MEP% IQ2 = 40%, IQ1- IQ3 = 40%-51.6%). Notably, EtCO2 revealed a significant positive correlation with age (r = 0.221, P = .009).
In a recent analysis on respiratory data in patients with DMD from the Canadian Neuromuscular Disease Registry (CNDR) published in Pediatric Pulmonology, findings showed a significant association between the loss of ambulation and the rate of FVC% decline.2 These results provide evidence toward understanding the impact of disease parameters on pulmonary function decline and the need for ventilatory support. The study enrolled 414 participants aged between 2 and 36 years old but only had pulmonary function test data available for 323 patients. Investigators observed the use of ventilatory support in a significant proportion (19.5%) of participants aged 14-16 years and used by the majority (69.2%) for those aged 20-22 years. Notably, FVC% declined at a rate of 3.19% per year with every 1-year increase in age and annually by 2.47% in nonambulatory participants compared with 0.96% in ambulatory participants. Authors noted that FVC% did not significantly change over age with presence of scoliosis or use of ventilatory technology.
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REFERENCES
1. Zhou L, Cai X, Huang M, Wang Q, Xu H, Zhang M. Natural history and related factors of respiratory function in children with Duchenne muscular dystrophy: a cross-sectional study. Presented at: 2024 MDA Clinical and Scientific Conference; March 3-6; Poster V449.
2. Hnaini M, Downs M, Miller MR, Campbell C, St-Laurent A. Duchenne muscular dystrophy respiratory profiles from real world registry data. Pediatr Pulmonol. 2023;58(10):2725-2732. doi:10.1002/ppul.26554
