the figure on the LEFT is a normally ventialted and perfused lung. at the right an airway obstruction prevents ventilation of a segement of lung. The alveoli become HYPOXIC. In response the blood vessels of that alveolar wals constrict. the vasoconstriction decreases bloodflow to the unventilated alveoli and effectivley decrease the shunt. Teh mechanism is not fully understood but is it presumd to be mediated by local factors
in response to alveolar hypoxia the alveolar arterioles do what?, therby decreasing shint blood flow
what type of drugs inhibit HPV, therby increasing the shunt and decreasing the PaO2?
Direct acting vasodilators
VAA's inhibit HPV when?
w/ high MAC (
a Pneumoectomy is underway. the non-dependent lung is deflated, and the PaO2 is 95mmHg. the pt becomes hypertensive and sodium nitroprusside is given. the PaO2 drops to 80mmHg. why?
HPV is inhibited