How to Use
- Set the alveolar oxygen tension (PAO₂).
Blood leaving ventilated alveoli is assumed to equilibrate completely, so end-capillary PO₂ equals PAO₂. - Adjust the cardiovascular parameters:
- Cardiac output determines total oxygen delivery. With consumption unchanged, a lower cardiac output forces the tissues to extract more oxygen.
- Shunt fraction is the proportion of cardiac output that reaches the systemic circulation without taking part in gas exchange, and so retains mixed-venous oxygen content. Increasing the shunt fraction will lower arterial oxygen content.
- Set the metabolic demand with the oxygen consumption (VO₂) slider.
- Change the haemoglobin concentration to alter oxygen content without changing the saturation associated with a given PO₂.
- If desired, adjust the factors that alter the p50 of the oxyhaemoglobin dissociation curve.
Maximum VO2 varies depending on the DO2.
Limitations
This model makes several assumptions:
- Oxygen transport is at steady state
i.e. whole-body oxygen uptake equals whole-body oxygen consumption. - The Riley 3-compartment model of the lung is used
- Haemoglobin concentration, cardiac output, oxygen consumption, and shunt fraction are constant across the model
- PCO₂, plasma pH, 2,3-DPG, and temperature are adjustable but remain constant within each modelled state
i.e. pH is independent of CO₂ - Haemoglobinopathies are not modelled