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The immediate shock of the cold causes involuntary inhalation, which if underwater can result in drowning. The cold water can also cause heart attack due to vasoconstriction; [4] the heart has to work harder to pump the same volume of blood throughout the body, and for people with heart disease, this additional workload can cause the heart to ...
Conversely, if the peripheral chemoreceptors are stimulated by hypoxia while the animal is breathing, the ventilation, heart rate and vasodilation of skeletal muscles is increased. [3] Oxygen consumption during a dive can be reduced by about 70%, attributed to anaerobic metabolism and probably also cooling of the body. [3]
Sudden drop in ambient pressure during an ascent to the surface from a 6 m final stop on oxygen. A shift from breathing oxygen at the final 6 m decompression stop at a partial pressure of 1.6 bar to breathing air at the surface with a partial pressure of 0.2 bar, could have vasodilatory effects during the period directly after surfacing.
Breathing pure oxygen significantly reduces the nitrogen loads in body tissues by reducing the partial pressure of nitrogen in the lungs, which induces diffusion of nitrogen from the blood into the breathing gas, and this effect eventually lowers the concentration of nitrogen in the other tissues of the body.
Gas is breathed at ambient pressure, and some of this gas dissolves into the blood and other fluids. Inert gas continues to be taken up until the gas dissolved in the tissues is in a state of equilibrium with the gas in the lungs (see saturation diving), or the ambient pressure is reduced until the inert gases dissolved in the tissues are at a higher concentration than the equilibrium state ...
A sufficiently large decrease in the partial pressure of oxygen leads to hypoxia, especially if the patient hypoventilates (which allows more time for evolving nitrous to dilute alveolar oxygen each breath). [5] Nonetheless, this effect only lasts a couple of minutes and hypoxia can be avoided by increasing the fractional inspired oxygen ...
The type I (glomus) cells in the carotid (and aortic bodies) are derived from neuroectoderm and are thus electrically excitable. A decrease in oxygen partial pressure, an increase in carbon dioxide partial pressure, and a decrease in arterial pH can all cause depolarization of the cell membrane, and they affect this by blocking potassium currents.
Slowing the heart rate reduces the cardiac oxygen consumption, and compensates for the hypertension due to vasoconstriction. However, breath-hold time is reduced when the whole body is exposed to cold water as the metabolic rate increases to compensate for accelerated heat loss even when the heart rate is significantly slowed. [2]