Published ahead of print on October 29, 2004, doi:10.1164/rccm.200403-314OC Am. J. Respir. Crit. Care Med., Volume 171, Number 3, February 2005, 269-274 A more recent version of this article appeared on February 1, 2005
Submitted on March 11, 2004 Use of Sniff Nasal Inspiratory Force to Predict Survival in Amyotrophic Lateral SclerosisRoss K Morgan1,1 Department of Medicine, Beaumont Hospital, Dublin, Ireland, 2 Department of Neurology, Beaumont Hospital, Dublin, Ireland, 3 Department of Epidemiology RCSI, Beaumont Hospital, Dublin, Ireland * To whom correspondence should be addressed. E-mail: rcostello{at}rcsi.ie.
Respiratory muscle weakness is the usual cause of death in amyotrophic lateral sclerosis. The prognostic value of the forced vital capacity, mouth-inspiratory force and sniff nasal-inspiratory force were established in a group of 98 patients with amyotrophic lateral sclerosis who were followed tri-monthly for three years. Sniff nasal-inspiratory force correlated with the trans-diaphragmatic 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 to either the forced vital capacity or mouth-inspiratory force (86% and 81%, p<0.01). A sniff nasal inspiratory-force <40 cm H2O was significantly related with nocturnal hypoxemia. When sniff nasal inspiratory-force was <40 cm H2O the hazard ratio for death was 9.1, (p=0.001) and the median survival was 6 ± 0.3 months. The sensitivity of forced vital capacity <50% for predicting 6 month mortality was 58% with a specificity of 96%, while sniff nasal-inspiratory force <40 H2O had a sensitivity of 97% and a specificity of 79% for death within 6 months. Thus, the SNIF 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. Key words: Respiratory muscle strength, respiratory failure, non-invasive ventialtion, neuromuscular disease
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