title: Repeated apneas and hypercapnic ventilatory response before and after apnea training.
abstract: BACKGROUND
  Habitual exposure to carbon dioxide (CO2) is expected, but it is not proven, to dull ventilatory sensitivity to co2 by reducing hypercapnic ventilatory response (HCVR) as it is expressed by the slope of the derived response curve (CO2 sensitivity: ΔVE/ΔPetCO2). It was hypothesized that HCVR is decreased by repeated breath hold maximal efforts (RBHE) before and after apnea training in comparison with no training and the control condition.
  
  
  METHODS
  Two groups of breath holders, a control (CBH) group and novices to breath hold activities (NBH), visited the laboratory on four different occasions. In the first visit, subjects performed a HCVR test, whereas in the second visit they completed five successive RBHE separated by 2-min intervals. Another HCVR test was performed 2 min after cessation of the last apnea. For the next 14 d, only the NBH group trained by performing daily five RBHE separated by 2-min intervals. Subsequently, in a third and a fourth condition, subjects repeated the experimental protocol of the second and first visit.
  
  
  RESULTS
  Although breath hold time (BHT) increased after apnea training in the NBH group by ~46%, CO2 sensitivity slopes were not different among experimental conditions and groups (2.8 0.3, 2.9 0.4 L min(1) mmHg(1) in the CBH and 2.7 0.5, 2.7 0.3 L min(1) mmHg(1) in the NBH during the second and third visit, respectively).
  
  
  CONCLUSIONS
  HCVR after five RBHE or 14 d of apnea training was not decreased despite the achieved BHT enhancement. Hypercapnic dullness of ventilation is a complex biological process which takes more than 14 d of training to develop. Bourdas DI, Tsakiris TS, Pavlakis KI, Triantafillou DV, Geladas ND. Repeated apneas and hypercapnic ventilatory response before and after apnea training.
authors.affiliation: Department of Sports Medicine & Biology of Exercise, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Dimitrios I
authors.initials: DI
authors.lastname: Bourdas
authors.forename: Theodoros S
authors.initials: TS
authors.lastname: Tsakiris
authors.forename: Konstantinos I
authors.initials: KI
authors.lastname: Pavlakis
authors.forename: Despoina V
authors.initials: DV
authors.lastname: Triantafillou
authors.forename: Nickos D
authors.initials: ND
authors.lastname: Geladas
mesh_terms: D000222:Adaptation, Physiological; D001049:Apnea / Q000503:physiopathology*; D062485:Breath Holding; D002245:Carbon Dioxide / Q000378:metabolism / Q000502:physiology*; D004311:Double-Blind Method; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D008297:Male; D009326:Naval Medicine; D010313:Partial Pressure; D012123:Pulmonary Ventilation; D015203:Reproducibility of Results; D013997:Time Factors; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide