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    Acid-base Equilibrium and High Altitude Disease

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    How is high altitude disease related to acid-base equilibrium?

    © BrainMass Inc. brainmass.com December 24, 2021, 8:29 pm ad1c9bdddf

    SOLUTION This solution is FREE courtesy of BrainMass!

    I presume it is to do with carbonic acid equilibrium in blood.

    At high altitude, the pO2 is lower and therefore the body is less able to remove CO2. Search for the Bohr effect. This effective increase in blood CO2 at high altitude will effect the equilibrium positions of bloods natural buffer system.

    Read the following extracts I got from the web with links to the websites.


    Bicarbonate is an alkaline, and a vital component of the pH buffering system[1] of the body (maintaining acid-base homeostasis). 70%-75% of CO2 in the body is converted into carbonic acid (H2CO3), which can quickly turn into bicarbonate (HCO3−).

    With carbonic acid as the central intermediate species, bicarbonate, in conjunction with water, hydrogen ions, and carbon dioxide forms this buffering system which is maintained at the volatile equilibrium[1] required to provide prompt resistance to drastic pH changes in both the acidic and basic directions. This is especially important for protecting tissues of the central nervous system, where pH changes too far outside of the normal range in either direction could prove disastrous. (See acidosis, or alkalosis.)

    Bicarbonate also acts to regulate pH in the small intestine. It is released from the pancreas in response to the hormone secretin to neutralize the acid chyme entering the duodenum from the stomach [2]


    Another biological fluid in which a buffer plays an important role in maintaining pH is blood plasma. In blood plasma, the carbonic acid and hydrogen carbonate ion equilibrium buffers the pH. In this buffer, carbonic acid (H2CO3) is the hydrogen-ion donor (acid) and hydrogen carbonate ion (HCO3-) is the hydrogen-ion acceptor (base).

    H2CO3(aq) H+(aq) + HCO3-(aq)

    This buffer functions in exactly the same way as the phosphate buffer. Additional H+ is consumed by HCO3- and additional OH- is consumed by H2CO3. The value of Ka for this equilibrium is 7.9 × 10-7, and the pKa is 6.1 at body temperature. In blood plasma, the concentration of hydrogen carbonate ion is about twenty times the concentration of carbonic acid. The pH of arterial blood plasma is 7.40. If the pH falls below this normal value, a condition called acidosis is produced. If the pH rises above the normal value, the condition is called alkalosis.

    The concentrations of hydrogen carbonate ions and of carbonic acid are controlled by two independent physiological systems. Carbonic acid concentration is controlled by respiration, that is through the lungs. Carbonic acid is in equilibrium with dissolved carbon dioxide gas.

    H2CO3(aq) = CO2(aq) + H2O(l)

    An enzyme called carbonic anhydrase catalyzes the conversion of carbonic acid to dissolved carbon dioxide. In the lungs, excess dissolved carbon dioxide is exhaled as carbon dioxide gas.

    CO2(aq) = CO2(g)

    The concentration of hydrogen carbonate ions is controlled through the kidneys. Excess hydrogen carbonate ions are excreted in the urine.

    The much higher concentration of hydrogen carbonate ion over that of carbonic acid in blood plasma allows the buffer to respond effectively to the most common materials that are released into the blood. Normal metabolism releases mainly acidic materials: carboxylic acids such as lactic acid (HLac). These acids react with hydrogen carbonate ion and form carbonic acid.

    HLac(aq) + HCO3-(aq) = Lac-(aq) + H2CO3(aq)

    The carbonic acid is converted through the action of the enzyme carbonic anhydrase into aqueous carbon dioxide.

    H2CO3(aq) = CO2(aq) + H2O(l)

    An increase in CO2(aq) concentration stimulates increased breathing, and the excess carbon dioxide is released into the air in the lungs.

    The condition called respiratory acidosis occurs when blood pH falls as a result of decreased respiration. When respiration is restricted, the concentration of dissolved carbon dioxide in the blood increases, making the blood too acidic. Such a condition can be produced by asthma, pneumonia, emphysema, or inhaling smoke.

    Metabolic acidosis is the decrease in blood pH that results when excessive amounts of acidic substances are released into the blood. This can happen through prolonged physical exertion, by diabetes, or restricted food intake. The normal body response to this condition is increases breathing to reduce the amount of dissolved carbon dioxide in the blood. This is why we breathe more heavily after climbing several flights of stairs.

    Respiratory alkalosis results from excessive breathing that produces an increase in blood pH. Hyperventilation causes too much dissolved carbon dioxide to be removed from the blood, which decreases the carbonic acid concentration, which raises the blood pH. Often, the body of a hyperventilating person will react by fainting, which slows the breathing.

    Metabolic alkalosis is an increase in blood pH resulting from the release of alkaline materials into the blood. This can result from the ingestion of alkaline materials, and through overuse of diuretics. Again, the body usually responds to this condition by slowing breathing, possibly through fainting.

    The carbonic acid-hydrogen carbonate ion buffer works throughout the body to maintain the pH of blood plasma close to 7.40. The body maintains the buffer by eliminating either the acid (carbonic acid) or the base (hydrogen carbonate ions). Changes in carbonic acid concentration can be effected within seconds through increased or decreased respiration. Changes in hydrogen carbonate ion concentration, however, require hours through the relatively slow elimination through the kidneys

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