hemoglobin-oxygen affinity; pO2 for 50% hemoglobin saturation with oxygen; oxygen P50

Introduction

Partial pressure of oxygen when hemoglobin is 50% saturated.

Reference interval

• Adult: 25-29 mm Hg
• Newborn: 18-24 mm Hg

Increases

increases with decreased affinity of hemoglobin for O2

• shift of hemoglobin dissociation curve to right
• hyperthermia
• acidemia
• hypercapnia
• increases in 2,3-DPG
• abnormal hemoglobin
  • hemoglobin Seattle

Decreases

decreases with increased affinity of hemoglobin for O2

• shift of hemoglobin dissociation curve to left
• hypothermia
• acute alkalemia
• hypocapnia
• decreased 2,3-DPG
• preeclampsia
• abnormal hemoglobin
  • hemoglobin Yakima
  • hemoglobin F

Methods

• determined by spectrophotometry

Specimen

• whole blood (heparin)

More general terms

• partial pressure of oxygen (pO2)

Additional terms

• SaO2