Decreased arterial P-O2, not O-2 content, increases blood flow through intrapulmonary arteriovenous anastomoses at rest

作者：Duke Joseph W^*; Davis James T; Ryan Benjamin J; Elliott Jonathan E; Beasley Kara M; Hawn Jerold A; Byrnes William C; Lovering Andrew T

来源：The Journal of Physiology, 2016, 594(17): 4981-4996.

DOI：10.1113/JP272211

Alveolar hypoxia causes increased blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA) in healthy humans at rest. However, it is unknown whether the stimulus regulating hypoxia-induced QIPAVA is decreased arterial P-O2 (P-aO2) or O-2 content (C-aO2). C-aO2 is known to regulate blood flow in the systemic circulation and it is suggested that IPAVA may be regulated similar to the systemic vasculature. Thus, we hypothesized that reduced C-aO2 would be the stimulus for hypoxia-induced QIPAVA. Blood volume (BV) was measured using the optimized carbon monoxide rebreathing method in 10 individuals. Less than 5 days later, subjects breathed room air, as well as 18%, 14% and 12.5% O-2, for 30 min each, in a randomized order, before (CON) and after isovolaemic haemodilution (10% of BV withdrawn and replaced with an equal volume of 5% human serum albumin-saline mixture) to reduce [Hb] (Low [Hb]). P-aO2 was measured at the end of each condition and QIPAVA was assessed using transthoracic saline contrast echocardiography. [Hb] was reduced from 14.2 +/- 0.8 to 12.8 +/- 0.7 g dl(-1) (10 +/- 2% reduction) from CON to Low [Hb] conditions. P-aO2 was no different between CON and Low [Hb], although C-aO2 was 10.4%, 9.2% and 9.8% lower at 18%, 14% and 12.5% O-2, respectively. QIPAVA significantly increased as P-aO2 decreased and, despite reduced C-aO2, was similar at iso-P-aO2. These data suggest that, with alveolar hypoxia, low P-aO2 causes the hypoxia-induced increase in QIPAVA. Whether the low P-O2 is detected at the carotid body, airway and/or the vasculature remains unknown.

• 出版日期2016-9-1