Hundal M, Ghattas C, Price LL, Lacamera P, Unterborn J (2019) Forced Mid-Expiratory Flow Can Predict Ventilatory Limitation and Exercise Capacity. Int J Respir Pulm Med 6:104.


© 2019 Hundal M, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Forced Mid-Expiratory Flow Can Predict Ventilatory Limitation and Exercise Capacity

Mandeep Hundal1*, Christian Ghattas1, Lori Lyn Price2, Peter Lacamera1 and John Unterborn1

1Division of Pulmonary, Critical Care & Sleep Medicine, St. Elizabeth Medical Center, USA

2Institute for Clinical Research and Health Policy Studies, Tufts Clinical and Translational Science Institute, Tufts Medical Center, USA



Exercise limitation associated with most lung diseases is multifactorial and is due to complex interactions between impaired ventilatory, cardiovascular, and peripheral muscle responses. Cardiopulmonary exercise tests (CPETs) are often required to ascertain the primary cause of exercise limitation particularly in patients with multiple co-morbidities. CPETs are generally offered only at tertiary care medical centers.


To evaluate if forced expiratory flow from 25% to 75% of vital capacity (FEF25-75%) can be used to predict both reduced exercise capacity and ventilatory limitation to exercise.


We retrospectively reviewed paired CPETs and spirometry tests performed on all adult patients (> 18 years of age) in the Pulmonary Physiology Laboratory at St. Elizabeth's Medical Center between April, 2006 and April, 2016 to explore the association between spirometric parameters and ventilatory limitation to exercise. Ventilatory limitation was defined as ventilatory reserve ≤ 15% at peak exercise. We defined reduced exercise capacity as peak oxygen consumption VO(2) < 20 mL/kg/min.


FEF25-75% was strongly associated with low breathing reserve (area under the ROC curve - 0.81). FEF25-75% was also significantly associated with the combined outcome of low ventilatory reserve and reduced exercise capacity. The area under the ROC curve was 0.86 (p < 0.0001) suggesting excellent predictive ability. In patients with FEV25-75% ≥ 40%, exercise limitation was much more commonly non-ventilatory in nature. In patients with mid-expiratory flow, FEV25-75% ≤ 20%, nearly 7 of 10 patients had ventilatory limitations to exercise.


Mid-expiratory flow FEF 25-75% is closely associated with both pulmonary ventilatory limitation to exercise and reduced exercise capacity.