The chemical balance that keeps your internal chemistry from collapsing

Science · Published 25 October 2026 Swipe more like this →

In short: Your body is a delicate balancing act of gases and acids. By measuring specific pressures in your arteries, clinicians can see exactly how well your lungs and kidneys are functioning—or if your metabolic state is drifting into danger.

Arterial blood gas (ABG) analysis is a clinical tool used to assess respiratory and metabolic function by measuring the levels of oxygen (O2) and carbon dioxide (CO2) in the blood. Because arteries carry oxygenated blood from the heart, they provide a more accurate snapshot of these gases than veins do. This test also determines the acidity, or pH balance, of the blood, which is critical for maintaining homeostasis.

The procedure involves a respiratory therapist inserting a small needle into an artery—most commonly the radial artery in the wrist, but sometimes the brachial artery in the arm or the femoral artery in the groin. Because arteries are deeper and surrounded by nerves, this process is typically more painful than a standard venous blood draw. To ensure safety, providers may perform an Allen test to confirm circulation to the hand before proceeding.

The results provide specific data points for clinical judgment. At sea level, normal partial pressure of oxygen (PaO2) ranges from 75 to 100 mm Hg, while carbon dioxide (PaCO2) typically sits between 38 and 42 mm Hg. The blood pH should remain within a tight window of 7.38 to 7.42. These values help doctors evaluate the effectiveness of oxygen therapy, non-invasive ventilation like BiPAP, or identify underlying issues with kidney function and metabolic diseases.

Context matters: environmental factors like altitude can lower oxygen values, and specific medical conditions—including head injuries or medications like anticoagulants—can influence results. By turning these measurements into actionable data, healthcare providers can monitor how the body regulates its internal environment under stress.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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