title: Cardiac function and oxygen saturation during maximal breath-holding in air and during whole-body surface immersion.
abstract: BACKGROUND
  The magnitude of the oxygen-sparing effect induced by the diving response in humans is still under debate. We wished to compare cardiovascular changes during maximal breath-holding (BH) in air and during whole-body immersion at the surface in a group of BH divers.
  
  
  METHODS
  Twenty-one divers performed a maximal static apnea in air or during whole-body immersion. Dopplerechocardiography, arterial blood pressure and haemoglobin saturation (SaO₂) were obtained at the beginning of, and at 1/3, 2/3 and maximal BH time.
  
  
  RESULTS
  BH time was on the average 3.6 ± 0.4 min, with no differences between the two conditions. SaO₂ significantly decreased during BH in both conditions, but was significantly higher during immersion as compared to the dry (P = 0.04). In both conditions, BH induced a significant linear increase in right ventricular diameter (P < 0.001), left ventricular (LV) volumes (P < 0.001) and LV stroke volume (P < 0.001) but a significant linear decrease in LV ejection fraction (P = 0.033). In both conditions, Doppler diastolic parameters showed changes suggesting a constrictive/restrictive left ventricular filling pattern (i.e., an increase of early diastolic left ventricular filling velocity, P = 0.005, and a decrease in the deceleration time of early diastolic left ventricular filling. P < 0.001).
  
  
  CONCLUSIONS
  BH induces progressive LV enlargement both in air and whole-body immersion, associated with reduced LV ejection fraction and progressive hindrance to diastolic filling. For a similar apnea duration, SaO₂ decreased less during immersed BH, indicating an O₂-sparing effect of diving, suggesting that interruption of apnea was not triggered by a threshold critical value of blood O₂ desaturation.
authors.affiliation: CNR Institute of Clinical Physiology, EXTREME Center, Scuola Superiore Sant' Anna, Piazza Martiri della Libertà 33, 56127 Pisa, Italy, Phone: +39-(0)47-335-7368, Fax: +39-(0)58-661-4268, E-mail: c.marabotti@alice.
authors.forename: Claudio
authors.initials: C
authors.lastname: Marabotti
authors.forename: Paolo
authors.initials: P
authors.lastname: Piaggi
authors.forename: Danilo
authors.initials: D
authors.lastname: Menicucci
authors.forename: Mirko
authors.initials: M
authors.lastname: Passera
authors.forename: Antonio
authors.initials: A
authors.lastname: Benassi
authors.forename: Remo
authors.initials: R
authors.lastname: Bedini
authors.forename: Antonio
authors.initials: A
authors.lastname: L'Abbate
mesh_terms: D000328:Adult; D000388:Air; D001794:Blood Pressure / Q000502:physiology; D062485:Breath Holding; D059267:Cardiomegaly, Exercise-Induced / Q000502:physiology; D003971:Diastole / Q000502:physiology; D004242:Diving / Q000502:physiology*; D004452:Echocardiography; D005260:Female; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles / Q000033:anatomy & histology; D006441:Hemoglobin A / Q000032:analysis; D006801:Humans; D007101:Immersion / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology
chemical_list: D006441:Hemoglobin A
keywords: Breath-hold diving; Doppler; cardiovascular; diving reflex; echocardiography; hypoxia; physiology