Overnight Pulse Oximetry to Determine Prognostic Factors in Subjects With Amyotrophic Lateral Sclerosis

BACKGROUND: The objective of the current study was to determine whether overnight pulse oximetry in patients with amyotrophic lateral sclerosis is prognostic of the onset of awake respiratory failure and hospital admissions.

METHODS: This was an observational study in a cohort of subjects with amyotrophic lateral sclerosis. The study included subjects with a baseline S_pO2 ≥ 94% on home overnight pulse oximetry testing. Patients age ≥ 80 y and those with comorbidities and with poor short-term prognosis or sleep apnea were excluded. The subjects were classified as nocturnal desaturators according to percentage of sleep time with S_pO2 < 90% (T90) > 10%.

RESULTS: A total of 76 subjects were included: 40 men (53%), mean ± SD age 60 ± 14.4 y, mean ± SD body mass index 25.7 ± 4.60 kg/m², and spinal presentation in 63.2%. After overnight pulse oximetry, 20 subjects (26%) were classified as desaturators and 56 (74%) as non-desaturators. In the first year, the subjects with nocturnal desaturation had respiratory failure more often compared with the subjects without desaturation (35% vs 10.91%; P = .02) and had a higher risk of developing respiratory failure during the course of the study (hazard ratio 2.48; P = .030). The desaturator group also had a higher rate of ≥ 1 admission (40% vs 7.3%; P = .01) and a higher likelihood of respiratory-related hospitalization (hazard ratio 2.41; P = .02). Median survival was almost 1 year less if T90 > 10% was observed in the overnight pulse oximetry: 21 months versus 32 months survival if T90 was ≤ 10%.

CONCLUSIONS: In subjects with amyotrophic lateral sclerosis, nocturnal desaturation conferred a higher risk of respiratory failure and poorer prognosis. Even in the absence of other clinical criteria, early pulse oximetry should be performed and the need for nocturnal ventilatory support assessed.