Objective: The objective of this study was to determine the PO2 at 50% hemoglobin oxygenation (P50) of feline hemoglobin (Hb).
Design: Prospective in vitro laboratory study.
Setting: Research laboratory.
Animals: Blood from 10 healthy cats.
Interventions: Individual blood samples were equilibrated with calibrated gases of 95, 21, 8, 5, 4, and 2.5% oxygen for tonometric analysis.
Measurements: Partial pressure of oxygen (PO2), oxygen content, oxyhemoglobin saturation, methemoglobin (MetHb), carboxyhemoglobin (COHb), Hb, packed cell volume, hydrogen ion concentration (pH), and partial pressure of carbon dioxide (PCO2) were measured in duplicate for each blood sample by tonometry. The P50 was calculated from both PO2/oxyhemoglobin saturation and PO2/oxygen content (per gram of Hb) curves.
Main results: The P50 from the PO2/oxyhemoglobin saturation curve was 35.6 mmHg and from the PO2/oxygen content (per gram of Hb) curve was 36.2 mmHg.
Conclusions: The oxyhemoglobin dissociation curve for the cat is shifted to the right, and thus, feline Hb has lower oxygen affinity compared with human and canine Hb.