Assessing Respiratory Function in the Patient with Neuromuscular Disease

Assessing respiratory function in patients with neuromuscular disease first begins with a detailed history of symptoms and a thorough physical examination that looks for abnormal breathing patterns and accessory muscle use. Simple spirometry with particular attention to forced vital capacity (FVC) as well as muscle force testing are commonly used tests that assess respiratory muscle strength and function. Additional tests such as slow vital capacity (SVC) and sniff nasal inspiratory pressure (SNIP) may be used for those patients with technical difficulty performing spirometry and standard muscle force testing. For more comprehensive evaluations of diaphragm function, electromyography (EMG) and ultrasound can be utilized, but require extensive training and technical expertise for proper interpretation. Recent studies have shown the harmful effects of elevated blood carbon dioxide. Therefore, longitudinal assessment of PCO2, particularly for those patients on noninvasive ventilation, has become increasingly important.