Assessment and management of respiratory function in patients with Duchenne muscular dystrophy: current and emerging options

Abstract

Duchenne muscular dystrophy (DMD) is an X-linked myopathy resulting in progressive weakness and wasting of all the striated muscles including the respiratory muscles. The consequences are loss of ambulation before teen ages, cardiac involvement and breathing difficulties, the main cause of death. A cure for DMD is not currently available. In the last decades the survival of patients with DMD has improved because the natural history of the disease can be changed thanks to a more comprehensive therapeutic approach. This comprises interventions targeted to the manifestations and complications of the disease, particularly in the respiratory care. These include: 1) pharmacological intervention, namely corticosteroids and idebenone that significantly reduce the decline of spirometric parameters; 2) rehabilitative intervention, namely lung volume recruitment techniques that help prevent atelectasis and slows the rate of decline of pulmonary function; 3) scoliosis treatment, namely steroid therapy that is used to reduce muscle inflammation/degeneration and prolong ambulation in order to delay the onset of scoliosis, being an additional contribution to the restrictive lung pattern; 4) cough assisted devices that improve airway clearance thus reducing the risk of pulmonary infections; and 5) non-invasive mechanical ventilation that is essential to treat nocturnal hypoventilation, sleep disordered breathing, and ultimately respiratory failure. Without any intervention death occurs within the first 2 decades, however, thanks to this multidisciplinary therapeutic approach life expectancy of a newborn with DMD nowadays can be significantly prolonged up to his fourth decade. This review is aimed at providing state-of-the-art methods and techniques for the assessment and management of respiratory function in DMD patients.

Keywords: DMD; GRMD; NIV; cough device; idebenone; lung volume recruitment; mdx; respiratory function; respiratory muscles; scoliosis; spinal fusion; spirometry; steroids.

Figure 1

Schematic diagram summarizing the natural course of the different respiratory functional parameters in DMD. Notes: Upward arrow: increase; Downward arrow: decrease. Abbreviations: FVC, forced vital capacity; MIP, maximal static inspiratory; P_DI, trans-diaphragmatic pressure; P_OES, esophageal pressure; RV, residual volume; P_GA, abdominal gastric pressure; SNIP, sniff nasal inspiratory pressure; TLC, total lung capacity; ERV, expiratory reserve volume; IRV, inspiratory reserve volume; DMD, Duchenne muscular dystrophy.