title: Cardiovascular adjustments in breath-hold diving: comparison between divers and non-divers in simulated dynamic apnoea.
abstract: The diving response is the sequence of cardiovascular, respiratory and metabolic adjustments produced by apnoea and further strengthened by cooling of the facial area and/or hypoxia. This study aimed at comparing the cardiovascular response to diving of trained divers with that of a control group. In this order, 14 trained divers were compared with 14 non-divers. By means of impedance cardiography and continuous monitoring of arterial pressure, hemodynamic data were collected during three different experimental sessions. Each session included a cycle-ergometer exercise against a workload of 0.5 W kg(-1) of body mass, pedalling in a steady-state condition. During exercise, each subject randomly accomplished 40 s of breath-hold exercise with face immersion (test A) or in air (test B). A control exercise test with normal breathing (test C) was also performed. Divers showed a faster onset of bradycardic response (ANOVA, P < 0.01) and a faster adjustment in systemic vascular resistance (P < 0.001 for divers vs. controls) than did non-divers. Moreover, cardiac output decreased only in divers during the first phase of test A (P < 0.01 for divers vs. controls). The most striking findings were that divers showed a more rapid cardiovascular adjustment with respect to controls, in particular in heart rate and systemic vascular resistance; moreover, with continued apnoea, a delayed increase in myocardial performance and stroke volume occurred and obscured the cardiovascular effects of the diving response.
authors: Dipartimento di Scienze Applicate ai Biosistemi, Sezione di Fisiologia Umana, Università di Cagliari, Via Porcell 4, 09124 Cagliari, Italy. filippo.tocco@tiscali.it
authors: Filippo
authors: F
authors: Tocco
authors: Antonio
authors: A
authors: Crisafulli
authors: Franco
authors: F
authors: Melis
authors: Cristina
authors: C
authors: Porru
authors: Gianluigi
authors: G
authors: Pittau
authors: Raffaele
authors: R
authors: Milia
authors: Alberto
authors: A
authors: Concu
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