Assessment of respiratory muscle strength in motor neurone disease: is asking enough?

Abstract

Motor neurone disease (MND), also known as amyotrophic lateral sclerosis (ALS), is a progressive degenerative neuromuscular disease against which the only licensed drug, Riluzole (Rilutek; Sanofi-Aventis, Paris, France), is only partially effective. When respiratory muscle weakness is sufficiently severe, type-II respiratory failure occurs. Several data suggest that noninvasive ventilation (NIV) improves quality of life and, at least in nonbulbar patients, extends life 1–3. The timing of initiation of NIV requires considerable clinical skill. As the therapy involves hospital attendance, whether or not the patient is admitted 4, it erodes the limited amount of “quality time” the patient has remaining. If administered too early the burdens of the treatment ( i.e. the need to use a mask, its associated complications and increased carer dependence) may outweigh the perceived benefits, in that symptoms of sleep-disordered breathing (SDB) may initially be mild. Evidence from Duchene muscular dystrophy suggests that if used too early, negative initial experience may deter patients from using the therapy when they are more symptomatic and/or in ventilatory failure 5. However, if administered too late the patient may experience unplanned deterioration, which carries the risk of either intubation or poorly managed end-of-life care 6. The most appropriate method of screening for respiratory failure in these patients with a high pre-test probability remains unclear. The ideal test would be noninvasive, simple to perform and simple to interpret allowing …