Hypoxia, not pulmonary vascular pressure induces blood flow through intrapulmonary arteriovenous anastomoses
Lovering, Andrew T.
Burgess, Keith R.
Lucas, Samuel J.E.
Lewis, Nia C. S.
Dominelli, Paolo B.
Henderson, William R.
Dominelli, Giulio S.
Sheel, A. William
The Physiological Society
MetadataShow full item record
Blood flow through intrapulmonary arteriovenous anastomoses (IPAVA) is increased with exposure to acute hypoxia and has been associated with pulmonary artery systolic pressure (PASP). We aimed to determine the direct relationship between blood flow through IPAVA and PASP in 10 participants with no detectable intracardiac shunt by comparing: (1) isocapnic hypoxia (control); (2) isocapnic hypoxia with oral administration of acetazolamide (AZ; 250 mg, three times-a-day for 48 h) to prevent increases in PASP, and (3) isocapnic hypoxia with AZ and 8.4% NaHCO3 infusion (AZ+HCO3-) to control for AZ-induced acidosis. Isocapnic hypoxia (20 min) was maintained by end-tidal forcing, blood flow through IPAVA was determined by agitated saline contrast echocardiography and PASP was estimated by Doppler ultrasound. Arterial blood samples were collected at rest before each isocapnic-hypoxia condition to determine pH, [HCO3-], and PaCO2. AZ decreased pH (-0.08 ± 0.01), [HCO3-] (-7.1 ± 0.7 mmol/l), and PaCO2 (-4.5 ± 1.4 mmHg; p<0.01), while intravenous NaHCO3 restored arterial blood gas parameters to control levels. Although PASP increased from baseline in all three hypoxic conditions (p<0.05), a main effect of condition expressed an 11 ± 2% reduction in PASP from control (p<0.001) following AZ administration while intravenous NaHCO3 partially restored the PASP response to isocapnic hypoxia. Blood flow through IPAVA increased during exposure to isocapnic hypoxia (p<0.01) and was unrelated to PASP, cardiac output and pulmonary vascular resistance for all conditions. In conclusion, isocapnic hypoxia induces blood flow through IPAVA independent of changes in PASP and the influence of AZ on the PASP response to isocapnic hypoxia is dependent upon the H+ concentration or PaCO2. Abbreviations list: AZ, acetazolamide; FEV1, forced expiratory volume in 1 second; FIO2, fraction of inspired oxygen; FVC, forced vital capacity; Hb, total haemoglobin; HPV, hypoxic pulmonary vasoconstriction; HR, heart rate; IPAVA, intrapulmonary arteriovenous anastomoses; MAP, mean arterial pressure; PASP, pulmonary artery systolic pressure; PETCO2, end-tidal partial pressure of carbon dioxide; PETO2, end-tidal partial pressure of oxygen; PFO, patent foramen ovale; PVR, pulmonary vascular resistance; Q̇c, cardiac output; RVOT, right ventricular outflow tract; SpO2, oxyhaemoglobin saturation; SV, stroke volume; TRV, tricuspid regurgitant velocity; V̇E, minute ventilation; VTI, velocity-time integral
The Journal of Physiology;
Tremblay, J.C., Lovering, A.T., Ainslie, P.N., Stembridge, M., Burgess, K.R., Bakker, A., Donnelly, J., Lucas, S.J., Lewis, N., Dominelli, P.B. and Henderson, W.R. (2015) 'Hypoxia, not pulmonary vascular pressure, induces blood flow through intrapulmonary arteriovenous anastomoses', The Journal of Physiology, 593(3), pp.723-737.
This article was published in The Journal of Physiology on 23 December 2014 (online), available at http://dx.doi.org/10.1113/jphysiol.2014.282962
Cardiff Metropolitan University (Grant ID: Cardiff Metropolian (Internal))
- Sport Research Groups 
Showing items related by title, author, subject and abstract.
Resting pulmonary haemodynamics and shunting: a comparison of sea-level inhabitants to high altitude Sherpas Foster, Glen; Ainslie, Philip; Stembridge, Mike; Day, Trevor A.; Bakker, Akke; Lucas, Samuel J.E.; Lewis, Nia C. S.; Macleod, David B.; Lovering, Andrew T. (Wiley, 2014-03-15)The incidence of blood flow through intracardiac shunt and intrapulmonary arteriovenous anastomoses (IPAVA) may differ between Sherpas permanently residing at high altitude (HA) and sea-level (SL) inhabitants as a result ...
The effects of graded changes in oxygen and carbon dioxide tension on coronary blood velocity independent of myocardial energy demand Boulet, Lindsey; Stembridge, Mike; Tymko, Michael; Tremblay, Joshua; Foster, Glen (American Physiological Society, 2016)In humans, coronary blood flow is tightly regulated by microvessels within the myocardium in order to match myocardial energy demand. However, evidence regarding inherent sensitivity of the microvessels to changes in ...
Bevan, Emma (Cardiff Metropolitan University, 2015)Exercise in hypoxia causes severe arterial hypoxemia. The acute cardiovascular responses include increases in heart rate (HR), cardiac output, and sympathetic nervous system activation. In the pulmonary system, ...