Cardiovascular changes during underwater static and dynamic breath-hold dives in trained divers

Abstract

Limited information exists concerning arterial blood pressure (BP) changes in underwater breath-hold diving. Simulated chamber dives to 50 m of freshwater (mfw) reported very high levels of invasive BP in two divers during static apnea (SA), whereas a recent study using a noninvasive subaquatic sphygmomanometer reported unchanged or mildly increased values at 10 m SA dive. In this study we investigated underwater BP changes during not only SA but, for the first time, dynamic apnea (DA) and shortened (SHT) DA in 16 trained breath-hold divers. Measurements included BP (subaquatic sphygmomanometer), ECG, and pulse oxymetry (arterial oxygen saturation, SpO₂, and heart rate). BP was measured during dry conditions, at surface fully immersed (SA), and at 2 mfw (DA and SHT DA), whereas ECG and pulse oxymetry were measured continuously. We have found significantly higher mean arterial pressure (MAP) values in SA (∼40%) vs. SHT DA (∼30%). Postapneic recovery of BP was slightly slower after SHT DA. Significantly higher BP gain (mmHg/duration of apnea in s) was found in SHT DA vs. SA. Furthermore, DA attempts resulted in faster desaturation vs. SA. In conclusion, we have found moderate increases in BP during SA, DA, and SHT DA. These cardiovascular changes during immersed SA and DA are in agreement with those reported for dry SA and DA.

Exercise at depth alters bradycardia and incidence of cardiac anomalies in deep-diving marine mammals

“…3a). Similar to humans [24][25][26] , these irregular IBI patterns were associated with independent ectopic heart beats that were most evident during periods of constant elevated SF (Fig. 3b).…”

“…In view of this, are there consequences when routine behaviours are disrupted? We have found that behaviours contributing to cardiac anomalies when submerged (elevated levels of physical exertion, deep-diving and rapid ascent from depth) are remarkably similar for terrestrial 18,[24][25][26][27] and marine (Figs 1-4) mammals. Coincidentally, these also comprise the suite of behaviours displayed during the flight response of beaked whales 34 and blue whales 35 exposed to shipping noise and midfrequency sonars.…”

“…In human breath-hold divers, when exercise is superimposed on the diving response, sympathetic neural activation dictates cardiac variability and the ultimate level of bradycardia that is achieved 25,26 . Similarly, in deep-diving Weddell seals, IBI fluctuated rapidly between short periods of tachycardia and bradycardia, especially during dive ascents (Fig.…”

Breath-hold diving performance factors

“…Throughout the test, the average heart rate (AHR-avg) and the minimum heart rate (AHR-min) were recorded. In order to calculate the HRsta, only HR data starting from the first 30 seconds of apnea, once the HR was stabilized (Breskovic, 2011), were considered for further analysis. The SpO2 was monitored by a pulse oximeter (CMS 50F) placed on the second finger of the left hand.…”

Developing and testing an instrument to assess aquaticity in humans

“…The abilities to see (task 7) and hear (task 8) underwater are related to chronic adaptations to the water environment (Gislen, Dacke et al 2003, Pau, Warkentin et al 2011 and are important features of professional divers' training related to performance and safety issues. The ability to perform a dynamic apnea for 25 m (task 9) reflects general physical adequacy in the water but more strongly breath-hold diving ability (Breskovic, Uglesic et al 2011). Moreover diving after voluntary expiration (task 10), near to the functional residual capacity of the lung, requires a good level of familiarization with underwater activities (Breskovic, Steinback et al 2011).…”