UMMS Affiliation

Department of Neurology

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Diagnosis | Infectious Disease | Nervous System Diseases | Neurology | Virus Diseases


Objective: To measure the correlation between single breath counting (SBC) and forced vital capacity (liters, FVCL) in amyotrophic lateral sclerosis (ALS) patients and to define the utility of SBC for determining when patients meet the threshold for initiation of noninvasive positive pressure ventilation (FVC < 50% predicted [FVCpred]).

Methods: Both patient paced (SBCpp) or externally paced (SBCep) counting along with FVCL+pred and standard clinical data were collected. Linear regression was used to examine SBCpp and SBCep as a predictor of FVCL. Receiver operating characteristic curve analysis evaluated the sensitivity and specificity of SBC categorically predicting FVCpred of < /=50%.

Results: In 30 ALS patients, SBC explained a moderate proportion of the variance in FVCL (SBCpp: R(2)= 0.431, p < 0.001; SBCep: R(2) = 0.511, p < 0.01); this proportion improved when including covariates (SBCpp: R(2)= 0.635, p < 0.01; SBCep: R(2)= 0.657, p < 0.01). Patients with minimal speech involvement performed similarly in unadjusted (SBCpp: R(2) = 0.511, p < 0.01; SBCep: R(2)= 0.595, p < 0.01) and adjusted (SBCpp: R(2) = 0.634, p < 0.01; SBCep: R(2)= 0.650, p < 0.01) models. SBCpp had 100% sensitivity and 60% specificity (area under curve (AUC) = 0.696) for predicting FVCpred < 50%. SBCep had 100% sensitivity and 56% specificity (AUC = 0.696). With minimal speech involvement SBCpp and SBCep both had 100% sensitivity and 76.1% specificity (SPCpp: AUC = 0.845; SBCep: AUC = 0.857).

Conclusions: SBC explains a moderate proportion of variance in FVC and is an extremely sensitive marker of poor FVC. When FVC cannot be obtained, such as during the current COVID-19 pandemic, SBC is helpful in directing patient care.


Single breath count, amyotrophic lateral sclerosis, biomarker, neuromuscular disease, ventilation

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© 2021 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (, which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

DOI of Published Version



Quinn C, Mcmillan CT, Owegi MA, Almasy K, Douthwright C, Mckenna-Yasek D, Goyal NA, Berry J, Brown RH. Single breath counting is an effective screening tool for forced vital capacity in ALS. Amyotroph Lateral Scler Frontotemporal Degener. 2021;22(sup1):5-8. doi: 10.1080/21678421.2021.1915337. PMID: 34348533. Link to article on publisher's site

Journal/Book/Conference Title

Amyotrophic lateral sclerosis and frontotemporal degeneration

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Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.