title: Ventilatory response of prepubertal boys and adults to carbon dioxide at rest and during exercise.
abstract: The aim of this study was to determine whether the greater ventilation in children at rest and during exercise is related to a greater CO2 ventilatory response. The CO2 ventilatory response was measured in nine prepubertal boys [10.3 years (SD 0.1)] and in 10 adults [24.9 years (SD 0.8)] at rest and during moderate exercise (VCO2 = 20 ml.kg-1.min-1) using the CO2-rebreathing method. Three criteria were measured in all subjects to assess the ventilatory response to CO2: the CO2 sensitivity threshold (Th), which was defined as the value of end tidal PCO2 (PETCO2) where the ventilation increased above its steady-state level; the reactivity slope expressed per unit of body mass (SBM), which was the slope of the linear relation between minute ventilation (VE) and PETCO2 above Th; and the slope of the relationship between the quotient of tidal volume (VT) and inspiration time (tI) and PETCO2 (VT.tI-1.PETCO2(-1)) values above Th. The VE, VT, breathing frequency (fR), oxygen uptake (VO2), and CO2 production (VCO2) were also measured before the CO2-rebreathing test. The following results were obtained. First, children had greater ventilation per unit body weight than adults at rest (P < 0.001) and during exercise (P < 0.01). Second, at rest, only VT.tI-1.PETCO2(-1) was greater in children than in adults (P < 0.001). Third, during exercise, children had a higher SBM (P < 0.02) and VT.tI-1.PETCO2(-1) (P < 0.001) while Th was lower (P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Service d'Exploration Fonctionelle Respiratoire, Hôpital Aiguelongue, Montpellier, France.
authors.forename: A
authors.initials: A
authors.lastname: Gratas-Delamarche
authors.forename: J
authors.initials: J
authors.lastname: Mercier
authors.forename: M
authors.initials: M
authors.lastname: Ramonatxo
authors.forename: J
authors.initials: J
authors.lastname: Dassonville
authors.forename: C
authors.initials: C
authors.lastname: Préfaut
mesh_terms: D000293:Adolescent; D000328:Adult; D002245:Carbon Dioxide / Q000502:physiology*; D002648:Child; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D012119:Respiration / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide