title: Alveolar gas composition during maximal and interrupted apnoeas in ambient air and pure oxygen.
abstract: We tested the hypothesis that the alveolar gas composition at the transition between the steady phase II (φ2) and the dynamic phase III (φ3) of the cardiovascular response to apnoea may lay on the physiological breaking point curve (Lin et al., 1974).
  
  
  
  Twelve elite divers performed maximal and φ2-interrupted apnoeas, in air and pure oxygen. We recorded beat-by-beat arterial blood pressure and heart rate; we measured alveolar oxygen and carbon dioxide pressures (PAO2and PACO2, respectively) before and after apnoeas; we calculated the PACO2difference between the end and the beginning of apnoeas (ΔPACO2).
  
  
  
  Cardiovascular responses to apnoea were similar compared to previous studies. PAO2and PACO2at the end of φ2-interrupted apnoeas, corresponded to those reported at the physiological breaking point. For maximal apnoeas, PACO2was less than reported by Lin et al. (1974). ΔPACO2was higher in oxygen than in air.
  
  
  
  The transition between φ2 and φ3 corresponds indeed to the physiological breaking point. We attribute this transition to ΔPACO2, rather than the absolute PACO2values, both in air and oxygen apnoeas.
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Italy; Dipartimento di Specialità Medico-chirurgiche, Scienze Radiologiche e Sanità Pubblica, Università di Brescia, Italy. Electronic address: nazzareno.fagoni@unibs.it.
authors.forename: Nazzareno
authors.initials: N
authors.lastname: Fagoni
authors.affiliation: Dipartimento di Scienze Cliniche e Sperimentali, Università di Brescia, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Taboni
authors.affiliation: Dipartimento di Scienze Cliniche e Sperimentali, Università di Brescia, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Vinetti
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Bottarelli
authors.affiliation: Département des Neurosciences Fondamentales, Université de Genève, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Moia
authors.affiliation: Département des Neurosciences Fondamentales, Université de Genève, Switzerland.
authors.forename: Aurélién
authors.initials: A
authors.lastname: Bringard
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Italy; Département des Neurosciences Fondamentales, Université de Genève, Switzerland.
authors.forename: Guido
authors.initials: G
authors.lastname: Ferretti
mesh_terms: D000328:Adult; D000388:Air; D001049:Apnea / Q000378:metabolism*; D056352:Athletes; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism; D004242:Diving / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D011312:Pressure; D011650:Pulmonary Alveoli / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: Alveolar gas; Diaphragmatic contraction; Interrupted apnoea; Maximal apnoea; Oxygen apnoea; P(A)CO(2)