title: Hyperventilation with He-O2 breathing is not decreased by superimposed external resistance.
abstract: The purpose of this study was to determine the effect of imposed external resistance on the ventilatory response to He-O(2) breathing during peak exercise. To accomplish this purpose, separate inspiratory and expiratory external resistances were applied to offset for the decrease in intrapulmonary airway resistance with He-O(2) breathing. Seven men and three women (69+/-3 years, mean+/-S.D.) with normal pulmonary function performed graded cycle ergometry to exhaustion breathing room air, He-O(2) (79% He, 21% O(2)), He-O(2) with imposed expiratory resistance, and He-O(2) with imposed inspiratory resistance. Ventilation (VE), lung mechanics, and PET(CO(2)) were measured during each 1 min increment in work rate and were analyzed by one-way ANOVA for repeated measures at rest, ventilatory threshold (VTh), and peak exercise. In response, VE was increased and PET(CO(2)) was decreased at VTh (P<0.01) and peak exercise (P<0.01) whenever breathing He-O(2). Thus, VE was increased during exercise above VTh with He-O(2) breathing regardless of increases in inspiratory or expiratory external resistance. In conclusion, these data suggest that inspiratory resistive unloading is no more important than expiratory resistive unloading to the increase in VE with He-O(2) breathing during heavy and peak exercise.
authors.affiliation: Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and The University of Texas Southwestern Medical Center, 7232 Greenville Avenue, Dallas, TX 77231, USA. tonybabb@texashealth.org
authors.forename: T G
authors.initials: TG
authors.lastname: Babb
authors.forename: Darren S
authors.initials: DS
authors.lastname: DeLorey
mesh_terms: D000368:Aged; D000388:Air; D000403:Airway Resistance / Q000502:physiology*; D000704:Analysis of Variance; D005080:Exercise Test / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006371:Helium; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D007321:Inspiratory Reserve Volume / Q000502:physiology; D008297:Male; D010100:Oxygen; D012123:Pulmonary Ventilation / Q000502:physiology*; D012129:Respiratory Function Tests / Q000379:methods / Q000706:statistics & numerical data; D014797:Vital Capacity / Q000502:physiology
chemical_list: D006371:Helium; D010100:Oxygen