The human body maintains a precise pH range of arterial blood between 7.35 and 7.45. Deviations result in either acidosis (pH 7.45). These conditions are further classified as respiratory or metabolic disorders based on their underlying cause.
Respiratory Acidosis and Alkalosis
Respiratory acidosis occurs due to an increase in the partial pressure of carbon dioxide PCO2 in the blood. It often arises from shallow breathing or impaired gas exchange caused by pneumonia, cystic fibrosis, or emphysema. These conditions lead to CO2 accumulation, resulting in a decrease in blood pH.
Respiratory alkalosis, by contrast, is caused by a decrease in blood PCO2 below 35 mmHg, typically due to hyperventilation. Common triggers include oxygen deficiency, stroke, or severe anxiety. This reduction in PCO2 causes an increase in blood pH, shifting the body into an alkalotic state.
Metabolic Acidosis and Alkalosis
Unlike respiratory disorders, which originate from changes in CO2 levels, metabolic disorders arise due to fluctuations in bicarbonate levels or non-carbonic acids. Metabolic acidosis is characterized by decreased blood bicarbonate ion (HCO3⁻) levels below 22 mEq/L. This condition may result from:
These factors contribute to a drop in blood pH.
Metabolic alkalosis occurs when blood HCO3⁻ levels rise above 26 mEq/L, causing a corresponding increase in blood pH above 7.45. This condition often results from:
Respiratory and metabolic acid-base disorders can disrupt homeostasis and require prompt intervention to restore pH balance. If left untreated, these disorders may lead to severe physiological complications. Prompt intervention is critical to restoring pH balance.
The normal pH range of systemic arterial blood is between 7.35 and 7.45.
An arterial blood pH and bicarbonate concentration below 7.35 and 20 mEq/L indicates acidosis, while pH and a bicarbonate concentration above 7.45 and 20 mEq/L indicates alkalosis. These conditions can be respiratory or metabolic.
Respiratory imbalances result from changes in the partial pressure of CO2.
Respiratory acidosis occurs when arterial PCO2 exceeds 45 mm Hg, in diseases like pneumonia, or emphysema.
In respiratory alkalosis, arterial PCO2 drops below 35 mm Hg, caused by oxygen deficiency, stroke, or anxiety.
Metabolic imbalances result from changes in blood pH.
Metabolic acidosis occurs when bicarbonate ion levels drop below 22 mEq/liter due to excessive ion loss in conditions like persistent diarrhea or excessive alcohol consumption.
In metabolic alkalosis, arterial bicarbonate ion concentration exceeds 28 mEq/liter due to vomiting, diuretics, or excessive intake of alkaline drugs.
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