Respiratory muscle strength as a predictive biomarker for survival in amyotrophic lateral sclerosis

Michael I. Polkey*, Rebecca A. Lyall, Ke Yang, Erin Johnson, P. Nigel Leigh, John Moxham

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

67 Citations (Scopus)
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Rationale: Biomarkers for survival in amyotrophic lateral sclerosis (ALS) would facilitate the development of novel drugs. Although respiratory muscle weakness is a known predictor of poor prognosis, a comprehensive comparison of different tests is lacking. 

Objectives: To compare the predictive power of invasive and noninvasive respiratory muscle strength assessments for survival or ventilator-free survival, up to 3 years. 

Methods: From a previously published report respiratory muscle strength measurements were available for 78 patients with ALS. Time to death and/or ventilation were ascertained. Receiver operating characteristic analysis was used to determine the cutoff point of each parameter. 

Measurements and Main Results: Each respiratory muscle strength assessment individually achieved statistical significance for prediction of survival or ventilator-free survival. In multivariate analysis sniff trans-diaphragmatic and esophageal pressure, twitch trans-diaphragmatic pressure (Tw Pdi), age, and maximal static expiratory mouth pressure were significant predictors of ventilationfree survival and Tw Pdi and maximal static expiratory mouth pressure for absolute survival. Although all measures had good specificity, there were differing sensitivities. All cutoff points for the VC were greater than 80% of normal, except for prediction of 3-month outcomes. Sequential data showed a linear decline for direct measures of respiratory muscle strength, whereas VC showed little to no decline until 12 months before death/ventilation. 

Conclusions: The most powerful biomarker for mortality stratification was Tw Pdi, but the predictive power of sniff nasal inspiratory pressure was also excellent. A VC within normal range suggested a good prognosis at 3 months but was of little other value.

Original languageEnglish
Pages (from-to)86-95
Number of pages10
JournalAmerican Journal of Respiratory and Critical Care Medicine
Issue number1
Early online date5 Aug 2016
Publication statusPublished - 1 Jan 2017


  • Amyotrophic lateral sclerosis
  • Diaphragm
  • Maximal inspiratory pressure
  • Sniff nasal inspiratory pressure
  • Survival


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