Acid-base balance respiration

Respiration—transport of oxygen from the lungs to the tissues and of COj from the tissues to the lungs Nutrition—transport of absorbed food materials Excretion—transport of metabolic waste to the kidneys, lungs, skin, and intestines for removal Maintenance of the normal acid-base balance in the body... 

Mode of action. Acetylsalicylic acid is unique among NSAIDs in that it also irreversibly inhibits COX by acylating the active site of the enzyme, so preventing the formation of products including thromboxane, prostacyclin and other prostaglandins, imtil more COX is synthesised. Acetylsalicylic acid is rapidly hydrolysed to salicylic acid in the plasma. Salicylic acid also has an anti-inflammatory action but additionally exerts important effects on respiration, intermediary metabolism and acid-base balance, and it is highly irritant to the stomach. 

The reverse is true when a patient with metabolic acidosis is treated with HCOT When the pH in plasma increases as the result of HCOj administration, stimulation of the peripheral chemoreceptors returns to normal. However, because of the slow equilibration of HCOj between plasma and CSF, the central chemoreceptors continue to be stimulated, and the patient continues to hyperventilate, even when the blood pH has returned to normal. Respiration does not return to normal until normal acid-base balance in the CSF of the brain is restored. 

Minerals dissolved in the body fluids are responsible for nerve impulses and the contraction of muscles, as well as for water- and acid-base balance. They play an important role in maintaining the respiration, heart rate, and blood pressure in normal limits. Deficiency of minerals in the diet may lead to severe, chronic clinical signs of diseases, frequently reversible after their supplementation in the diet, or following the total parenteral nutrition. Their influence on biochemical reactions in living systems also makes it possible to use them intentionally in many food processes. 

Cellular metabolism results in the production of large quantities of hydrogen that need to be excreted in order to maintain acid-base balance. In addition, small amounts of acid and alkali are also presented to the body through the diet. The bulk of acid production is in the form of CO2, from the metabolism of carbohydrates, proteins, and lipids. When respiratory function is normal, the amount of CO2 produced metabolically is equal to the amount lost by respiration, and the blood CO2 concentration remains constant. The average adult produces approximately 15,000 mmol of CO2 each day from the catabolism of carbohydrate, protein, and fat. ... 

The low carbon dioxide level and the high pH while on the respirator were unexpected. These levels led the physician to check the settings on the respirator. The volume adjustment on the respirator had slipped. The patient was receiving twice the recommended quantity of air. This caused respiratory alkalosis, a condition of decreased acidity of the blood and tissues. When the respirator was adjusted, the blood levels returned to normal as the acid-base balance was reestablished, and the patient began to recover. 

Respiratory alkalosis is much less common than acidosis but can occur when respiration is stimulated or is no longer subjcci to feedback control (Fig. 4). Usually these are acute conditions, and there is no renal compensation. The treatment is to inhibit or remove the cause of the hyperventilation, and the acid-base balance should return to normal. Examples are ... 

The bicarbonate ion (HCO3A is the second-largest anionic contributor to maintaining acid-base balance, and its secretion from the pancreas helps to neutralize the contents of the small intestine. Respiration controlling the carbon dioxide concentration of the blood (PaCOj) and renal excretion of bicarbonate are the two main homeostatic influences on plasma bicarbonate. Within the renal tubular lumen, carbonic anhydrase converts carbonic acid into carbon dioxide, which diffuses into the epithelial cells and forms carbonic acid, which later dissociates to bicarbonate. 

The respiratory effects of salicylates contribute to the serious acid—base balance disturbances that characterize poisoning. Salicylates stimulate respiration directly and indirectly. Uncoupling of oxidative phosphorylation leads to increased peripheral CO2 production and a compensatory increase in minute ventilation, usually with no overall change in PCO2. Uncoupling of oxidative phosphorylation also leads to excessive heat production, and salicylate toxicity is associated with hyperthermia, particularly in children. 

Changes in the pH of the body are resisted through varied buffer systems that convert a strong acid or base to a weak one and thus bind H+ ions or leave more ions free. The body has several mechanisms for regulation of the acid-base balance of the body. The first mechanism is respiration. Respiration affects the acid-base balance by influencing the amount of carbon dioxide in the bloodstream. Carbon dioxide mixes with water to form carbonic acid, a weak acid, which breaks down into hydrogen ions (H ) and bicarbonate (HC03 ) 6... 

An adequate understanding of the acid-base balance in the blood demands an elementary knowledge of the mechanism of respiration. In respiration, oxygen is used in metabolism and carbon dioxide and pairs of hydrogen atoms are produced. Thus, respiration refers to the consumption of oxygen and the production of CO2. 

Acid-base and electrolyte balance High therapeutic dose especially when used in rheumatic fever, stimulates respiration and causes respiratory alkalosis. Reduction in bicarbonate and potassium level reduces the buffering capacity of the extracellular and intracellular fluid. Hypokalemia may lead to dehydration and hypernatremia. They also interfere with carbohydrate metabolism resulting in accumulation of pyruvic acid and lactic acid. 

---