Regional VA, Q, and VA/Q during PLV: effects of nitroprusside and inhaled nitric oxide.
Partial liquid ventilation (PLV) with high-specific-weight perfluorocarbon liquids has been shown to improve oxygenation in acute lung injury, possibly by redistributing perfusion from dependent, injured regions to nondependent, less injured regions of the lung. Our hypothesis was that during PLV in normal lungs, a shift in perfusion away from dependent lung zones might, in part, be due to vasoconstriction that could be reversed by infusing sodium nitroprusside (NTP). In addition, delivering inhaled NO during PLV should improve gas exchange by further redistributing blood flow to well-ventilated lung regions. To examine this, we used a single transverse-slice positron emission tomography camera to image regional ventilation and perfusion at the level of the heart apex in six supine mechanically ventilated sheep during five conditions: control, PLV, PLV + NTP, and PLV + NO at 10 and 80 ppm. We found that PLV shifted perfusion from dependent to middle regions, and the dependent region demonstrated marked hypoventilation. The vertical distribution of perfusion changed little when high-dose intravenous NTP was added during PLV, and inhaled NO tended to shift perfusion toward better ventilated middle regions. We conclude that PLV shifts perfusion to the middle regions of the lung because of the high specific weight of perflubron rather than vasoconstriction.
Harris
R Scott
RS
Department of Medicine (Pulmonary and Critical Care Unit), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA. rharris@partners.org
Willey-Courand
Donna-Beth
DB
Head
C Alvin
CA
Galletti
Gaetano G
GG
Call
Daniel M
DM
Venegas
José G
JG
D000280:Administration, Inhalation; D000818:Animals; D007275:Injections, Intravenous; D021061:Liquid Ventilation; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000008:administration & dosage / Q000494:pharmacology; D009599:Nitroprusside / Q000008:administration & dosage / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000502:physiology*; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology*; D012756:Sheep; D014055:Tomography, Emission-Computed; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*
D020030:Nitric Oxide Donors; D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide