title: Breathing He-O2 increases ventilation but does not decrease the work of breathing during exercise.
abstract: We previously observed an increase in minute ventilation (V E) with resistive unloading (He-O2 breathing) in healthy elderly subjects with normal pulmonary function. To investigate the effects of resistive unloading in elderly subjects with mild chronic airflow limitation (FEV(1)/FVC: 61 +/- 4%), we studied 10 elderly men and women 70 +/- 3 yr of age. These subjects performed graded cycle ergometry to exhaustion, once breathing room air and once breathing a He-O2 gas mixture (79% He, 21% O2). V E, pulmonary mechanics, and PET(CO2) were measured during each 1-min increment in work rate. Data were analyzed by paired t test at rest, at ventilatory threshold (VTh), and during maximal exercise. V E was significantly (p < 0.05) increased at VTh (3.4 +/- 4.0 L/min or 12 +/- 15% increase) and maximal exercise (15.2 +/- 9.7 L/min or 22 +/- 13% increase) while breathing He-O2. Concomitant to the increase in V E, PET(CO2) was decreased at all levels (p < 0.01), whereas total work of breathing against the lung was not different. We concluded that V E is increased during He-O2 breathing because of resistive unloading of the airways and the maintenance of the relationship between the work of breathing and exercise work rate.
authors.affiliation: Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and University of Texas Southwestern Medical Center, Dallas, Texas, USA. tonybabb@TexasHealth.org
authors.forename: T G
authors.initials: TG
authors.lastname: Babb
mesh_terms: D000367:Age Factors; D000368:Aged; D015444:Exercise; D005260:Female; D005540:Forced Expiratory Flow Rates / Q000187:drug effects; D006371:Helium / Q000494:pharmacology*; D006801:Humans; D006985:Hyperventilation / Q000139:chemically induced*; D007320:Inspiratory Capacity / Q000187:drug effects; D008297:Male; D011659:Pulmonary Gas Exchange; D012044:Regression Analysis; D015656:Respiratory Mechanics / Q000187:drug effects*; D012737:Sex Factors; D016037:Single-Blind Method; D014939:Work of Breathing / Q000187:drug effects*
chemical_list: D006371:Helium