Sildenafil, nifedipine and acetazolamide do not allow for blood flow through intrapulmonary arteriovenous anastomoses during exercise while breathing 100% oxygen

Accordingly, the purpose of this study was to investigate the independent effects of sildenafil, nifedipine and acetazolamide on the regulation of Q ̇ IPAVA during exercise while breathing 100% O2. To this end, we studied nine healthy human subjects at rest and during submaximal exercise. This was performed while breathing room air and 100% O2 at base-line without any pharmacological intervention, with a single dose of sildenafil, with a single dose of nifedipine, and after acetazolamide administration. We hypothesized that if the hyperoxia-mediated reduction in Q ̇ IPAVA was regulated primarily by L-type calcium channels then oral nifedepine would allow for Q ̇ IPAVA during exercise while breathing 100% O2. Additionally, we hypothesized that if the hyperoxia-mediated reduction in Q ̇ IPAVA was regulated primarily through nitric oxide, then oral sildenafil would allow for Q ̇ IPAVA during exercise while breathing 100% O2. Lastly, we hypothesized that if the hyperoxia-mediated reduction in Q ̇ IPAVA was regulated primarily by non-L-type calcium channels then oral acetazolamide would allow for Q ̇ IPAVA during exercise while breathing 100% O2.