title: Ventilatory oscillations at exercise: effects of hyperoxia, hypercapnia, and acetazolamide.
abstract: Periodic breathing has been found in patients with heart failure and sleep apneas, and in healthy subjects in hypoxia, during sleep and wakefulness, at rest and, recently, at exercise. To unravel the cardiorespiratory parameters liable to modulate the amplitude and period of ventilatory oscillations, 26 healthy subjects were tested under physiological (exercise) and environmental (hypoxia, hyperoxia, hyperoxic hypercapnia) stresses, and under acetazolamide (ACZ) treatment. A fast Fourier transform spectral analysis of breath-by-breath ventilation (V˙E) evidenced an increase in V˙E peak power under hypercapnia (vs. normoxia and hyperoxia, P < 0.001) and a decrease under ACZ (vs. placebo, P < 0.001), whereas it was not modified in hyperoxia. V˙E period was shortened by exercise in all conditions (vs. rest, P < 0.01) and by hypercapnia (vs. normoxia, P < 0.05) but remained unchanged under ACZ (vs. placebo). V˙E peak power was positively related to cardiac output (Q˙c) and V˙E in hyperoxia (P < 0.01), in hypercapnia (P < 0.001) and under ACZ (P < 0.001). V˙E period was negatively related to Q˙c and V˙E in hyperoxia (P < 0.01 and P < 0.001, respectively), in hypercapnia (P < 0.05 and P < 0.01, respectively) and under ACZ (P < 0.05 and P < 0.01, respectively). Total respiratory cycle time was the main factor responsible for changes in V˙E period. In conclusion, exercise, hypoxia, and hypercapnia increase ventilatory oscillations by increasing Q˙c and V˙E, whereas ACZ decreases ventilatory instability in part by a contrasting action on O2 and CO2 sensing. An intrinsic oscillator might modulate ventilation through a complex system where peripheral chemoreflex would play a key role.
authors.affiliation: Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France eric.hermand17@gmail.com.
authors.forename: Eric
authors.initials: E
authors.lastname: Hermand
authors.affiliation: Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne Service de Physiologie explorations fonctionnelles et médecine du sport, Bobigny, France.
authors.forename: François J
authors.initials: FJ
authors.lastname: Lhuissier
authors.affiliation: Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Larribaut
authors.affiliation: Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Pichon
authors.affiliation: Université Paris 13 Sorbonne Paris Cité Laboratoire "Hypoxie et poumon", Bobigny, France Assistance Publique-Hôpitaux de Paris, Hôpital Avicenne Service de Physiologie explorations fonctionnelles et médecine du sport, Bobigny, France.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Richalet
keywords: Acetazolamide; exercise; hypercapnia; hyperoxia; hypoxia; periodic breathing; ventilatory oscillations