Clinical meaning
Arterial blood gas (ABG) analysis provides critical information about a patient's acid-base balance, oxygenation, and ventilation status. The normal ABG values — pH 7.35-7.45, PaCO2 35-45 mmHg, PaO2 80-100 mmHg, HCO3 22-26 mEq/L, and SaO2 95-100% — represent the body's tightly regulated homeostatic mechanisms. Respiratory acidosis (pH < 7.35, PaCO2 > 45) results from hypoventilation, while respiratory alkalosis (pH > 7.45, PaCO2 < 35) results from hyperventilation. Metabolic acidosis (pH < 7.35, HCO3 < 22) occurs from bicarbonate loss or acid accumulation, while metabolic alkalosis (pH > 7.45, HCO3 > 26) occurs from acid loss or bicarbonate excess. Compensation occurs when the opposing system attempts to normalize pH.
Exam relevance
Risk factors: - Acute respiratory distress syndrome (ARDS) triggers: sepsis, aspiration, trauma - Mechanical ventilation complications: barotrauma, VILI - Airway obstruction risk: post-extubation laryngeal edema - Neuromuscular weakness affecting ventilation - Massive pulmonary embolism - Severe pneumonia with sepsis