hypoxemic

Hypoxemic is an adjective used in medicine to describe conditions in which the arterial blood carries abnormally low levels of oxygen. It denotes hypoxemia, defined by reduced PaO2 (the partial pressure of oxygen in arterial blood) or decreased arterial oxygen saturation (SaO2/SpO2). Hypoxemia can lead to tissue hypoxia if oxygen delivery to organs does not meet metabolic needs. The term hypoxemic is distinct from hypoxia: hypoxemia refers to low blood oxygen content, while hypoxia refers to insufficient oxygen delivery to tissues regardless of blood levels.

Causes and mechanisms commonly involve impaired transfer of oxygen in the lungs. This includes ventilation–perfusion mismatch, diffusion impairment, shunt, or sustained hypoventilation. Conditions such as pneumonia, acute respiratory distress syndrome, pulmonary edema, COPD exacerbation, interstitial lung disease, pulmonary embolism, and high altitude can produce hypoxemic states. Anemia or abnormalities in hemoglobin concentration can affect oxygen content but do not by themselves define hypoxemia unless arterial oxygen pressure or saturation is reduced.

Diagnosis relies on arterial blood gas testing to measure PaO2, with hypoxemia typically defined as PaO2 ≤ 80 mmHg, and/or reduced SaO2. Pulse oximetry provides continuous noninvasive monitoring of SpO2. The alveolar-arterial gradient may help differentiate causes. Hypoxemia may be accompanied by symptoms such as shortness of breath, tachypnea, and tachycardia, and in severe cases can cause confusion or organ dysfunction.

Management focuses on correcting the underlying cause and ensuring adequate oxygen delivery. Supplemental oxygen is used to reach target oxygen saturations (commonly 88–92% in COPD and 92–96% in others). More advanced support, including noninvasive or invasive ventilation, may be required for severe or worsening hypoxemia.

See also: hypoxia, respiratory failure.