The Inert Gas Rebreathing Method for Hemodynamic Measurements
Inert gas rebreathing is a pulmonary gas exchange method for determination of cardiac output and a number of other hemodynamic parameters.
During a rebreathing test Innocor® measures the relative levels of two inert gases - one blood soluble and one insoluble component - over a few respirations (about 5 breaths or 15 seconds).
The method relies on the simple principle that the rate of disappearance of the blood soluble gas from the alveolar space is proportional to the flow of blood perfusing the ventilated parts of the lungs (effective pulmonary blood flow). This is equal to cardiac output in the absence of a significant intrapulmonary shunt.
The blood insoluble gas is measured to determine the lung volume from which the soluble gas disappears and to account for other factors that affect the distribution of the blood soluble gas. The rebreathing bag is prefilled with an O2 enriched mixture typically containing 0.5% nitrous oxide (N2O) and 0.1% sulfur hexafluoride (SF6).
These gases and CO2 are measured continuously and simultaneously at the patient's mouth by a fast responding photoacoustic infrared gas analyzer inside Innocor®.
As opposed to other non-invasive techniques, Innocor® can be used equally well in patients at rest and during exercise. The only requirement is that the patient is capable of following the instructions from the operator.