Assessment of pulmonary function in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterised by diffuse and progressive death of motor neurons and deteriorating pulmonary functions. At diagnosis most patients with ALS usually do not have any respiratory complaints. However, sub-clinical pulmonary dysfunction is known.

To study pulmonary dysfunction in patients who clinically and electro-physiologically fulfil El escorial criteria of probable and definite ALS.

We performed a standard battery of pulmonary function tests (PFTs) including spirometry, maximum voluntary ventilation (MVV) and maximum inspiratory and expiratory pressure (MEP, MIP) on 63 patients fulfilling the El escorial criteria for probable and definite ALS. Results were compared between the El escorial groups, bulbar- and limb-onset ALS and with age- and sex-matched healthy volunteers, taken as controls.

Only 11% of the patients had respiratory complaints at diagnosis. There was no statistical difference in pulmonary parameters between bulbar- and limb-onset ALS. The pulmonary dysfunction was restrictive. Both definite and probable ALS patients had significant reduction in all the measured pulmonary function parameters. The reduction in definite ALS patients was greater in forced vital capacity percent (FVC%) predicted, peak expiratory flow rate (PEFR) percent predicted and MIP. The proportion of patients with severe and very severe dysfunction was higher in the definite ALS group as compared to probable ALS group.

Significant pulmonary dysfunction of restrictive type was noted in ALS patients. Both types of ALS, bulbar- and limb-onset, had similar levels of dysfunction.