From the Guidelines
Normal body fluid pH is typically maintained between 7.35 and 7.45 units. This range is crucial for maintaining proper cellular function and enzyme activity throughout the body, as significant deviations can lead to serious conditions like acidosis or alkalosis, which can disrupt normal physiological processes and potentially become life-threatening if not corrected [ 1 ]. The body maintains this narrow pH range through several buffer systems, primarily the bicarbonate buffer system in the blood, along with respiratory and renal mechanisms that can adjust pH when needed.
- The lungs help regulate pH by controlling carbon dioxide levels, which forms carbonic acid when dissolved in blood.
- The kidneys excrete or retain hydrogen ions and bicarbonate as needed to maintain the balance. According to the British Thoracic Society guideline for oxygen use in adults in healthcare and emergency settings, published in Thorax in 2017 [ 1 ], acidosis is defined as a pH < 7.35 and alkalosis is defined as a pH > 7.45.
- Acidosis can be caused by respiratory or metabolic disorders, and it is determined by the concentration of hydrogen ions [H+], which is normally regulated between 35 and 45 nmol/L.
- The normal pH range of the blood in humans is between 7.35 and 7.45 units, as expressed in terms of pH where pH = −log10 [H+].
From the Research
Normal Body Fluid pH
The normal body fluid pH is slightly alkaline, ranging from 7.35 to 7.45 2. This narrow range is maintained by the body's acid-base balance system, which involves the regulation of hydrogen ion concentration in the blood and other bodily fluids.
Factors Affecting Body Fluid pH
Several factors can affect body fluid pH, including:
- Respiratory acidosis or alkalosis, which occurs when there is an imbalance in the levels of carbon dioxide in the blood 2
- Metabolic acidosis or alkalosis, which occurs when there is an imbalance in the levels of bicarbonate and other ions in the blood 3, 4
- Renal function, which plays a critical role in maintaining acid-base balance by regulating the excretion of hydrogen ions and bicarbonate 3
Maintaining Acid-Base Balance
The body maintains acid-base balance through various mechanisms, including:
- Buffering systems, which help to regulate the concentration of hydrogen ions in the blood 5
- Respiratory compensation, which involves changes in breathing rate to regulate the levels of carbon dioxide in the blood 2
- Renal compensation, which involves changes in the excretion of hydrogen ions and bicarbonate to regulate the levels of these ions in the blood 3