p02

P02, sometimes written as p02, most commonly refers to the partial pressure of oxygen, denoted pO2. In physiology and medicine, pO2 measures the amount of oxygen available in a gas or biological system and is reported in units such as millimeters of mercury (mmHg) or kilopascals (kPa). Arterial oxygen tension (PaO2) reflects oxygen transfer from the lungs to the bloodstream and is typically about 75–100 mmHg at sea level. Venous oxygen tension (PvO2) and mixed venous pO2 are lower, corresponding to tissue oxygen extraction. The alveolar oxygen tension (PAO2) relates to inspired oxygen and alveolar gas exchange and influences PaO2.

Clinical measurement usually uses arterial blood gas analysis to determine PaO2; noninvasive estimates come from pulse oximetry, which measures oxygen saturation (SpO2) rather than pO2. Transcutaneous oxygen measurements (TcPO2) provide localized estimates of tissue pO2 and are used in wound care and anesthesia monitoring.

Several factors affect pO2, including ambient pressure (altitude), lung function, ventilation–perfusion matching, hemoglobin concentration, and diffusion capacity. Abnormal pO2 levels can indicate respiratory or circulatory disorders such as chronic obstructive pulmonary disease, pneumonia, pulmonary edema, or hypoxemia due to other causes.

The notation p02 is often a plain-text variant of pO2. In some contexts, it may serve as a code or identifier unrelated to oxygen tension. When encountered, the intended meaning typically depends on context, so clarification is advised.