Key result
5-bar normoxic exposure increases maximal left ventricular pressure and LVP velocities in anesthetized rats.
p-value: p=<0.01
Hyperbaric exposure to 5 bar significantly increases cardiac contractility in anesthetized rats, with helium producing a greater effect than nitrogen.
Supports investigation of hyperbaric cardiac effects; leaves open relevance beyond anesthetized rat models.
The left ventricular pressure, arterial blood pressure and heart rate were studied in three series of pentobarbital-anaesthetized rats exposed to 5-bar normoxic (PO2 = 0.2 bar) environments: nitrogen-oxygen (15 and 60 min) and helium-oxygen (15 min). The maximal left ventricular pressure (LVP max) and the maximal velocities of LVP rise (+ dP/dt max) and fall (- dP/dt) were significantly (P less than 0.01) increased immediately after reaching normoxic 5 bar (He, 13-28%; N2, 13-23%) and during the exposure at 5 bar (He, 22-44%; N2, 13-18%). The pulse pressure increased significantly (He, 50-62%; N2, 30-34%; P less than 0.01) during the hyperbaric exposure. No changes in heart rate or end-diastolic and mean arterial pressure were detected. The present findings indicate an enhanced cardiac contractility (+ dP/dt max) at 5 bar, with the greatest increase found when He was used as inert gas. The increased contractility was of significant duration (at least 60 min), and was not completely reversed until 5-10 min after decompression.
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Stuhr et al. (1989) studied this question. 5-bar normoxic environments (nitrogen-oxygen and helium-oxygen) was evaluated on Maximal left ventricular pressure and velocities of LVP rise and fall (p=<0.01). Exposure to 5-bar normoxic environments significantly increased maximal left ventricular pressure and velocities of LVP rise and fall in pentobarbital-anaesthetized rats (P<0.01).
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