Oxygen saturation of blood is a fundamental clinical parameter that assesses how much oxygen is being carried by red blood cells (RBCs). The importance of these so-called oximetery measurements is highlighted by the current COVID-19 crisis because patients present a profound drop in blood oxygen, known as hypoxaemia. However, another aspect of oxygen handling by blood that is not currently measured is the speed with which RBCs exchange gases. Indeed, routinely performed tests for gas-carrying capacity (for example, total hemoglobin) cannot determine how fast RBCs take-up and release oxygen. Such information is critical for evaluating the physiological fitness of RBCs, which have less than one second to exchange large volumes of oxygen in the lungs and tissues.
To address this problem, a team led by Associate Professor Pawel Swietach has designed a method to quantify gas exchange in individual RBCs. Applying this method to various blood disorders has highlighted the barriers to efficient gas exchange. The results identify the adaptations that allow healthy RBCs to exchange gases quickly, and explain how disease-related changes may impair oxygen transport.
According to Prof Swietach: “With single-cell resolution, we can identify physiologically inferior subpopulations, providing a clinically useful appraisal of blood quality. Our technique can provide new information about oxygen transport, particularly in disorders such as COVID-19 where the cause of hypoxaemia is not established and therefore the choice of treatment remains unclear.”
The full paper 'Single-cell O2 exchange imaging shows that cytoplasmic diffusion is a dominant barrier to efficient gas transport in red blood cells' is available to read in PNAS.