Nocturnal oximetry: utility in the respiratory management of amyotrophic lateral sclerosis.

OBJECTIVE

Current recommendations are to institute nocturnal nasal ventilation for amyotrophic lateral sclerosis patients with a forced vital capacity (FVC) of <50% of predicted normal. The purpose of this study was to determine whether this is appropriate.

DESIGN

A total of 87 nocturnal oximetry evaluations were performed on 78 consecutive amyotrophic lateral sclerosis patients symptomatic for sleep-disordered breathing. Nocturnal oximetry measurements were compared for those with FVC >50% vs. those with FVC of <50% of normal. FVC was measured sitting and supine.

RESULTS

A considerable number of these symptomatic patients manifested evidence of nocturnal hypoxemia as measured by oximetry. However, there was no significant difference between patients with sitting percentage-predicted FVC above and below 50% predicted in minimum oxygen saturation, mean oxygen saturation, percentage of time spent with oxygen saturation of <88%, and number of events per hour. There was no significant difference between patients with supine percentage-predicted FVC above and below 50% predicted in minimum oxygen saturation, mean oxygen saturation, percentage of time spent with oxygen saturation of <88%, and number of events per hour.

CONCLUSION

The recommendation that FVC be <50% of normal is inappropriate for justifying introduction of nocturnal nasal ventilation. Many patients are symptomatic at higher FVC and manifest evidence of nocturnal hypoxemia. Nocturnal oximetry adds additional practical information for justifying earlier respiratory intervention for symptomatic patients.