title: The influence of varying inspired fractions of O₂ and CO₂ on the development of involuntary breathing movements during maximal apnoea.
abstract: The growing urge to breathe that occurs during breath-holding results in development of involuntary breathing movements (IBMs). The present study determined whether IBMs are initiated at critical levels of hypercapnia and/or hypoxia during maximal apnoea. Arterial blood gasses at the onset of IBM were monitored during maximal voluntary breath-holds. Eleven healthy men performed breath holds after breathing air, hyperoxic-normocapnia, hypoxic-normocapnia, and normoxic-hypercapnia. Pre-breathing of the gas mixtures facilitated the IBM onset, reducing the time-to-onset for ∼46% (hyperoxic condition) and for ∼80% (hypoxic condition) compared to the normoxic air breathing time. A strong correlation (R=0.83, P=0.002) between arterial partial pressure of CO₂ (PaCO₂) at IBM onset after pre-breathing hyperoxic and hypercapnic gas mixtures was observed, suggesting the existence of a possible IBM PaCO₂ threshold level of ∼6.5 ± 0.5 kPa. No clear "threshold" was observed for partial pressure of arterial O₂(PaO₂). However, we observed that IBM onset was influenced, in part, by an interaction between PaO₂ and PaCO₂ levels during maximal apnoea. This study demonstrated the complex interaction between arterial blood-gases and the physiological response to maximal breath holding.
authors.affiliation: Department of Integrative Physiology, University of Split School of Medicine, Split, Croatia.
authors.forename: Toni
authors.initials: T
authors.lastname: Breskovic
authors.forename: Mihajlo
authors.initials: M
authors.lastname: Lojpur
authors.forename: Petra Zubin
authors.initials: PZ
authors.lastname: Maslov
authors.forename: Troy J
authors.initials: TJ
authors.lastname: Cross
authors.forename: Jasenka
authors.initials: J
authors.lastname: Kraljevic
authors.forename: Marko
authors.initials: M
authors.lastname: Ljubkovic
authors.forename: Jasna
authors.initials: J
authors.lastname: Marinovic
authors.forename: Vladimir
authors.initials: V
authors.lastname: Ivancev
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Dujic
mesh_terms: D000328:Adult; D000388:Air; D001049:Apnea / Q000097:blood / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000097:blood / Q000502:physiology*; D006801:Humans; D008297:Male; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood / Q000502:physiology*; D010313:Partial Pressure; D012119:Respiration; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen