title: Use of Sniff nasal-inspiratory force to predict survival in amyotrophic lateral sclerosis.
abstract: Respiratory muscle weakness is the usual cause of death in amyotrophic lateral sclerosis. The prognostic value of the forced vital capacity (FVC), mouth-inspiratory force, and sniff nasal-inspiratory force were established in a group of 98 patients with amyotrophic lateral sclerosis who were followed trimonthly for 3 years. Sniff nasal-inspiratory force correlated with the transdiaphragmatic pressure (r = 0.9, p < 0.01). Sniff nasal-inspiratory force was most likely to be recorded at the last visit (96% of cases), compared with either the FVC or mouth-inspiratory force (86% and 81%, respectively, p < 0.01). A sniff nasal-inspiratory force less than 40 cm H(2)O was significantly related with nocturnal hypoxemia. When sniff nasal-inspiratory force was less than 40 cm H(2)O, the hazard ratio for death was 9.1 (p = 0.001), and the median survival was 6 +/- 0.3 months. The sensitivity of FVC < 50% for predicting 6-month mortality was 58% with a specificity of 96%, whereas sniff nasal-inspiratory force less than 40 H(2)O had a sensitivity of 97% and a specificity of 79% for death within 6 months. Thus the sniff nasal-inspiratory force test is a good measure of respiratory muscle strength in amyotrophic lateral sclerosis, it can be performed by patients with advanced disease, and it gives prognostic information.
authors.affiliation: Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.
authors.forename: Ross K
authors.initials: RK
authors.lastname: Morgan
authors.forename: Stephen
authors.initials: S
authors.lastname: McNally
authors.forename: Michael
authors.initials: M
authors.lastname: Alexander
authors.forename: Ronan
authors.initials: R
authors.lastname: Conroy
authors.forename: Orla
authors.initials: O
authors.lastname: Hardiman
authors.forename: Richard W
authors.initials: RW
authors.lastname: Costello
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009055:Mouth / Q000503:physiopathology; D009666:Nose / Q000503:physiopathology*; D011379:Prognosis; D016016:Proportional Hazards Models; D012133:Respiratory Paralysis / Q000503:physiopathology; D012680:Sensitivity and Specificity; D012890:Sleep / Q000502:physiology; D013147:Spirometry; D015996:Survival Rate; D014797:Vital Capacity / Q000502:physiology; D014939:Work of Breathing / Q000502:physiology