Relationship Between Decrease of Oxygenation During Incremental Exercise and Partial Pressure End-Tidal Carbon Dioxide: Near-Infrared Spectroscopy Vector Analysis

• Published in: Advances in experimental medicine and biology Vol. 1269; p. 119
• Main Authors: Kojima, Sho, Morishita, Shinichiro, Hotta, Kazuki, Qin, Weixiang, Kato, Toshinori, Oyama, Katsunori, Tsubaki, Atsuhiro
• Format: Journal Article
• Language: English
• Published: United States 01.01.2021
• Subjects: Carbon Dioxide; Exercise; Humans; Male; Oxygen Consumption; Partial Pressure; Spectroscopy, Near-Infrared; Partial pressure end-tidal carbon dioxide; Prefrontal cortex oxygenation; Incremental load exercise; NIRS vector analysis; Near-infrared spectroscopy
• ISSN: 0065-2598
• DOI: 10.1007/978-3-030-48238-1_19

A previous study considered that a decrease in cerebral oxyhemoglobin (O Hb) immediately before maximal exercise during incremental exercise is related to cerebral blood flow (CBF) and partial pressure end-tidal carbon dioxide (P CO ). This study aimed to investigate the relationship between O Hb, P CO , and the estimated value of cerebral blood volume (CBV) with cerebral oxygen exchange (COE) by using vector analysis. Twenty-four healthy young men participated in this study. They performed the incremental exercise (20 W/min) after a 4-min rest and warm-up. The O Hb and deoxyhemoglobin (HHb) in the prefrontal cortex (PFC) were measured using near-infrared spectroscopy (NIRS). The P CO was measured using a gas analyzer. The O Hb, HHb, and P CO were calculated as the amount of change (ΔO Hb, ΔHHb, and ΔP CO ) from an average 4-min rest. Changes in the CBV (ΔCBV) and COE (ΔCOE) were estimated using NIRS vector analysis. Moreover, the respiratory compensation point (RCP), which relates to the O Hb decline, was detected. The Pearson correlation coefficient was used to establish the relationships among ΔO Hb, ΔP CO , ΔCBV, and ΔCOE from the RCP to maximal exercise. The ΔP CO did not significantly correlate with the ΔO Hb (r = 0.03, p = 0.88), ΔCOE (r = -0.19, p = 0.36), and ΔCBV (r = -0.21, p = 0.31). These results showed that changes in the ΔP CO from the RCP to maximal exercise were not related to changes in the ΔO Hb, ΔCOE, and ΔCBV. Therefore, we suggested that the decrease of O Hb immediately before maximal exercise during incremental exercise may be related to cerebral oxygen metabolism by neural activity increase, not decrease of CBF by the P CO .