In this article we will discuss about the causes and effects of hyperpnoea mostly seen in human bodies.
The term hyperpnoea means increased breathing. Any rise in the quantity of air breathed per minute is called hyperpnoea.
Causes of Hyperpnoea:
i. Voluntary
ii. Impulses from the cerebral cortex to the respiratory centres, e.g., emotion.
iii. Impulses from the hypothalamus.
iv. Reflexly by the stimulation of nerves of general sensation (pain, heat, cold, etc.) in the skin,
v. All conditions where metabolic rate is very high demanding more oxygen supply and producing more CO2 for elimination, for instance muscular exercise.
vi. Factors causing dyspnoea will evidently cause hyperpnoea. Voluntary hyperpnoea, being of special interest, is discussed in detail below.
Effects of Voluntary Hyperpnoea:
When a person, at bodily and mental rest, goes on breathing deeply and quickly (causing over-ventilation) for about 3 minutes and then stops, the following changes are found to take place:
i. Breathing remains suspended for a period (apnoea). This is due to the washing-out of excess CO2 and consequent reduction of CO2 in the arterial blood. After this period of apnoea, periodic breathing (alternate breathing and apnoea) may follow for some time and then normal breathing is restored.
ii. Alkaosis, due to washing out of excess CO2, blood becomes more alkaline.
iii. Increased execration of alkaline urine containing bicarbonates. This is due to failure of the renal tubular cells to provide sufficient H+ due to washing-out excess CO2. Normally secretion of H+ and absorption of HCO3– are interdependent. In the absence of secretion of H+, HCO3– and Na+ are eliminated in the urine.
iii. Presence of keto acids in the urine.
iv. Skin vessels are constricted and the skin is white and cold.
v. Increase in cardiac output and a slight rise of blood pressure.
vi. Dizziness and paraesthesia of the extremities. The consciousness may be dulled. The development of the cerebral symptoms is due to anoxia which causes cerebral vasoconstriction.
vii. Tetany, (may be due to alkalosis). This is due to failure of renal tubular cells to secrete H+. As a result NH3 manufactured by the renal distal tubular cells cannot form ammonium salts. Keto acids as such are eliminated in the urine.