Cardiovascular changes during deep breath-hold dives in a pressure chamber

Abstract

Electrocardiogram, cardiac output, and blood lactate accumulation were recorded in three elite breath-hold divers diving to 40-55 m in a pressure chamber in thermoneutral (35 degrees C) or cool (25 degrees C) water. In two of the divers, invasive recordings of arterial blood pressure were also obtained during dives to 50 m in cool water. Bradycardia during the dives was more pronounced and developed more rapidly in the cool water, with heart rates dropping to 20-30 beats/min. Arrhythmias occurred, particularly during the dives in cool water, when they were often more frequent than sinus beats. Because of bradycardia, cardiac output decreased during the dives, especially in cool water (to <3 l/min in 2 of the divers). Arterial blood pressure increased dramatically, reaching values as high as 280/200 and 290/150 mmHg in the two divers, respectively. This hypertension was secondary to peripheral vasoconstriction, which also led to anaerobic metabolism, reflected in increased blood lactate concentration. The diving response of these divers resembles the one described for diving animals, although the presence of arrhythmias and large increases in blood pressure indicate a less perfect adaptation in humans.

Effects of head and body cooling on hemodynamics during immersed prone exercise at 1 ATA

“…It is possible that more extreme selective cooling of the face and head could induce larger changes in pulmonary artery pressure. However, studies of the hemodynamic effects of facial immersion published thus far have shown significant effects on HR at water temperatures of 25°C and 35°C (3,15). In a study of facial cooling, systematic evaluation of water temperatures (0 -35°C) failed to show any temperature effect on HR (19).…”

“…Bradycardia, hypertension, and peripheral vasoconstriction have been observed (9,21) associated with increased peripheral sympathetic nerve activity (14). Severe hypertension has been observed during breath-hold dives in cool water (15). It is likely that pulmonary hypertension also occurs.…”

Relationships between the extent of apnea-induced bradycardia and the vascular response in the arm and leg during dynamic two-legged knee extension exercise

“…mean arterial pressure; femoral blood flow; breath hold LARGE CARDIOVASCULAR RESPONSES occur during breath-hold diving in both animals and humans (10,12,14,19,28,36). The response is characterized by bradycardia and vasoconstriction related to the so-called "diving reflex" (1,8,10,20,24,36), and it has been proposed that the function of these changes is primarily to preserve an adequate O 2 supply to vital organs (1,4,15,18,19,24). Some diving animals, such as seals, show remarkable bradycardia during voluntary diving (36).…”

Apnea Training Specificity and its Implications for Performance in Aquatic Sports: Case Study Reports

“…The diving reflex, as a survival mechanism, is accompanied with an elevated arterial blood pressure though results are inconclusive [14,15]. The lack of oxygen due to apnea, inevitably triggers the anaerobic metabolism causing an increase in blood lactate [13,[16][17][18].…”