Effects of Carbon Dioxide and Temperature on the Oxygen-Hemoglobin Dissociation Curve of Human Blood: Implications for Avalanche Victims.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study on human blood samples assessing physiological mechanisms
PubMed 35198571 · doi:10.3389/fmed.2021.808025
What was done
Venous blood samples from 30 healthy volunteers (15 male, 15 female) were evaluated in an in vitro factorial experiment testing four carbon dioxide partial pressures (PCO2: 20, 40, 60, and 80 mmHg) across five temperatures (13.7°C, 23°C, 30°C, 37°C, and 42°C). Oxygen dissociation curves (ODC) were measured in unbuffered whole blood, and P50, Hill coefficients, CO2-Bohr coefficients, and temperature coefficients were analyzed with a linear mixed model. Findings were then applied to a mathematical model of avalanche burial combining cooling rates and hypercapnia.
What was found
Baseline mean P50 at 37°C and 40 mmHg PCO2 was 27.1 ± 2.6 mmHg. Both CO2-Bohr and temperature coefficients significantly affected P50 (both p < 0.001). While absolute CO2 effects remained prominent at 37°C and 42°C, the relative CO2-Bohr coefficient increased significantly at lower temperatures (interaction p < 0.001). Mathematical modeling suggested that combined hypothermia and hypercapnia can lead to a net increase in hemoglobin oxygen affinity in hypoxic avalanche conditions.
Why it matters
This study clarifies how temperature and hypercapnia interact to influence oxygen-hemoglobin binding, offering mechanistic insight into oxygen delivery and consumption during avalanche burial and severe accidental hypothermia.
Limits
The study was conducted entirely in vitro on blood from healthy volunteers, which cannot fully reproduce the dynamic metabolic acidosis, microvascular responses, or organ-level perfusion changes seen in vivo. Application to avalanche burial is based on theoretical modeling rather than real-world physiological measurements from hypothermic patients.
Cited by
- supports Elevated carbon dioxide levels trigger the dissociation and release of oxygen from hemoglobin.