Arterial Respiration: The Journey of Oxygen from Lungs to Tissues

Arterial respiration refers to the entire process of oxygen delivery via the arterial system—from pulmonary gas exchange to tissue perfusion.

Stepwise Pathway

1. Inhalation: Air enters alveoli (PO₂ ~100 mmHg).
2. Alveolar-capillary diffusion: O₂ crosses alveolar epithelium, interstitium, capillary endothelium into blood (driven by PO₂ gradient).
3. Hemoglobin binding: Each Hb binds 4 O₂; cooperative binding yields sigmoidal dissociation curve.
4. Arterial transport: Oxygenated blood (PaO₂ ~95–100 mmHg) travels via pulmonary veins → left heart → aorta → systemic arteries.
5. Capillary-tissue exchange: At tissues (PO₂ ~40 mmHg), O₂ dissociates from Hb, diffuses to mitochondria.
6. Venous return: Deoxygenated blood (PvO₂ ~40 mmHg) → vena cava → right heart → pulmonary artery → repeat.

Key Determinants of Delivery

• Cardiac output (heart rate × stroke volume).
• Hemoglobin concentration.
• O₂ saturation (SaO₂).
• Tissue perfusion distribution.

Arterial respiration ensures continuous O₂ supply for aerobic ATP production and CO₂ removal.