Efficacy of eucapnic voluntary hyperpnea to estimate the oxygen cost of breathing during exercise

Abstract

Study Objective: The O2 cost of breathing is typically measured at rest utilizing a eucapnic voluntary hyperpnea (EVH) protocol that requires multiple levels of minute ventilation (V̇E). However, the ability of the EVH test to predict the O2 cost of breathing during exercise remains unknown. This study investigated whether EVH testing can be used to estimate the O2 cost of breathing during exercise by comparing two EVH protocols: one while seated at rest (‘EVHREST’) and one during steady state exercise (‘EVHEX’). Hypothesis: No significant difference would be found between the slopes of EVHREST and EVHEX. Methods: 12 men and 12 women (age:36±8yr; height:171±12cm; weight:108±26kg; BMI:36±5kg/m2) without cardiovascular disease, asthma, a history of smoking, or musculoskeletal abnormalities, completed EVHREST and EVHEX testing on two separate visits to the laboratory. The O2 cost of breathing during EVHREST was determined by calculating the slope of the V̇O2 (ml/min) vs. V̇E (L/min) relationship at rest and during voluntary hyperpnea at two levels of V̇E (‘EVHLOW’ and ‘EVHHIGH’), which amounted to 40 and 60L/min for women, and 60 and 90L/min for men. On a subsequent visit, the O2 cost of breathing during EVHEX was determined via 6min of cycling at 30W with and without voluntary hyperpnea at a V̇E of 70L/min for both men and women. During the voluntary hyperpnea portion of each test, participants were instructed to inhale and exhale along with a metronome to clamp breathing frequency and tidal volume at EVHLOW (men:36br/min, 1.7L; women:30br/min, 1.3L), EVHHIGH (men:40br/min, 2.3L; women:36br/min, 1.7L) and EVHEX (men:40br/min, 1.8L; women:40br/min, 1.8L). A Student’s paired t-test was used to assess the difference in O2 cost slopes between EVHREST and EVHEX. Results: During EVHREST, the target V̇E values of 40 and 60L/min were well-matched for women (EVHLOW:40±1L/min; EVHHIGH:60±4L/min) and the target V̇E values of 60 and 90L/min were well-matched for men (EVHLOW:61±2L/min; EVHHIGH:91±2L/min). Likewise, during EVHEX for men and women combined, the target V̇E value of 70L/min was also well-matched (70±4L/min). During EVHREST for men and women combined, V̇O2 increased from rest (257±55ml/min) to EVHLOW (348±70ml/min) and again to EVHHIGH (406±92ml/min). During EVHEX, V̇O2 increased from exercise at 30W without voluntary hyperpnea (808±126ml/min) to exercise at 30W with voluntary hyperpnea (915±129ml/min). No significant difference was detected between the O2 cost slopes obtained from EVHREST (2.24±0.75ml/L) and EVHEX (2.28±0.83ml/L; p=0.802). Conclusion: Measurements demonstrated no difference in the mean O2 cost slope between EVHREST and EVHEX, suggesting that a traditional EVH protocol while seated at rest may be utilized to effectively approximate the O2 cost of breathing during submaximal steady-state exercise. NIH AG070262, NIH HL096782, NIH HL136643-05S1, King Charitable Foundation Trust, Cain Foundation, Texas Health Presbyterian Hospital Dallas. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.