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Characteristics of Analyzing Acid Base Balance

Acid-base balance is defined as the balance between acidity and alkalinity in the body. Blood pH measures the degree of acidity or alkalinity in blood. The respiratory system and the renal system act as buffering systems to maintain the blood's acid-base balance. The body regulates the blood's acid-base balance minute by minute because even a minor deviation from the normal range can damage organ systems.

  1. Acid-Base Balance

    • The respiratory system and the renal system interact to regulate the body's acid-base balance. Carbon dioxide combines with water to form carbonic acid. Carbonic acid breaks down into hydrogen ions and bicarbonate. Movement through the carbonic acid system is fluid and constant. An arterial blood gas measures the acid-base balance of arterial blood. This test analyzes blood pH, the amount of dissolved carbon dioxide (pCO2) in the blood and the amount of bicarbonate (HCO3) in the blood.

    pH Scale

    • The pH scale ranges from zero (strong acidic) to 14 (strong basic, or alkaline). A pH of 7.0 is neutral. Blood has a pH range between 7.35 and 7.45. The body maintains a blood pH close to 7.40. If blood pH is below 7.35, it is acidic; if blood pH is above 7.45, it is alkaline.

    Respiratory System

    • The respiratory system regulates the acid-base balance. Carbon dioxide is mildly acidic and is a byproduct of oxygen metabolism. Normal pCO2 levels are 35-45mmHg. A pCO2 reading below 35 is alkalotic, while a pCO2 reading above 45 is acidotic. The lungs regulate blood pH by regulating the speed and depth of breathing. Fast, deep breathing lowers carbon dioxide levels; conversely, slow, shallow breathing increases carbon dioxide.

    Renal System

    • The renal system regulates the acid-base balance. Normal urine has a pH of 6.0 (slightly acidic). A normal HCO3 level is 22-26mEg/L. If the HCO3 level is below 22, the patient is acidotic; if the HCO3 is above 26, the patient is alkalotic. The kidneys secrete excess hydrogen ions to balance the pH level. However, this may take several days.

    Compensation

    • The body uses the opposite system to regulate pH. For example, if the respiratory system disrupts the pH, the renal system counteracts it. Conversely, if the renal system disrupts the pH, the respiratory system counteracts it. This process is called compensation and returns the pH balance to normal.

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