Hemodynamics and vascular oxygenation measured at the forehead during changes in respiration: A SPA-fNIRS study.

SIGNIFICANCE: Cerebral blood flow is influenced by respiration, primarily through changes in the CO2 concentration of arterial blood.

AIM: The objective of this study was to investigate the effect of changes in arterial CO2 concentration induced by respiratory changes on oxygenation and hemodynamics in the cerebral and extracerebral tissue layers of the forehead.

APPROACH: We used systemic physiology augmented functional near-infrared spectroscopy (SPA-fNIRS) to assess changes in forehead hemodynamics and oxygenation as well as systemic physiology in 20 healthy subjects. All participants performed two respiratory tasks (breath-holding and hyperventilation).

RESULTS

In our SPA-fNIRS study we found that changes in breathing affected hemodynamics and oxygenation in both the extracerebral and cerebral tissue layers of the forehead in characteristic ways, depending on the two respiratory tasks.

CONCLUSION

The results show that extracerebrovascular reactivity (ECVR) exists in parallel with the well-known cerebrovascular reactivity (CVR). CVR and ECVR must be considered when performing fNIRS neuroimaging studies involving changes in respiration.