Hapnikusaturationi

Hapnikusaturationi, often called oxygen saturation, is the proportion of hemoglobin binding sites in the blood that are occupied by oxygen. It is typically expressed as a percentage and is denoted in arterial blood as SaO2 or noninvasively as SpO2 when measured with pulse oximetry. In healthy individuals at sea level, arterial saturation usually ranges from about 95 to 100 percent.

The concept reflects the balance between oxygen loading in the lungs and unloading in tissues. In the lungs, oxygen diffuses into the blood and binds to hemoglobin. In tissues, oxygen is released to meet metabolic needs. Normal saturation depends on adequate arterial oxygen partial pressure (PaO2) and normal hemoglobin function. Saturation can remain near 100 percent even as PaO2 varies within a certain range, but it declines with hypoxemia or impaired oxygen transport.

Measurement and interpretation: SaO2 is measured directly from arterial blood via co-oximetry in an arterial blood gas test. SpO2 is estimated continuously by pulse oximetry, using light absorption properties of oxyhemoglobin and deoxyhemoglobin. Limitations include the influence of dyshemoglobins (eg, carboxyhemoglobin, methemoglobin), perfusion quality, motion, ambient light, and substances like nail polish. SpO2 can misrepresent true oxygenation in certain conditions, requiring ABG analysis for exact assessment.

Normal and abnormal values: values outside the normal range can indicate hypoxemia or impaired oxygen delivery. SpO2 below about 90 percent is generally considered clinically significant hypoxemia, though targets vary with clinical context, altitude, and comorbidities.

Clinical use: hapnikusaturationi is routinely monitored in anesthesia, critical care, pulmonology, and emergency settings to guide oxygen therapy and assess respiratory function.