The effects of nitric oxide inhalation on respiratory mechanics and gas exchange during endotoxaemia in the pig.
BACKGROUND
In the adult respiratory distress syndrome, nitric oxide (NO) inhalation improves oxygenation through reducing ventilation-perfusion mismatching, but detailed information on the pulmonary effects of NO inhalation in septic shock is scarce. The present study investigated the effects of inhaled NO on alveolar dead space (Vdalv) and venous admixture as well as on respiratory system compliance (Crs) and respiratory system resistance (Rrs) in a porcine model of septic shock. Protective effects of NO are discussed.


METHODS
Thirteen anaesthetised and ventilated pigs were given an infusion of endotoxin for an observation time of 220 min to induce acute lung injury (ALI). In the NO-early group (n=6), an inhalation of 60 ppm NO was started simultaneously with the endotoxin infusion and continued for 190 min. In 7 control/NO-late animals, 60 ppm NO was administered for 30 min following 190 min of endotoxin infusion. Haemodynamics, single-breath CO2-, pressure-, and flow signals were recorded.


RESULTS
Endotoxin induced haemoconcentration, pulmonary vasoconstriction, and a decrease in Crs, while venous admixture, Vdalv, and Rrs increased. In the NO-early group, the pulmonary vasoconstriction was attenuated, no increase in pulmonary venous admixture or in Vdalv was seen before cessation of NO, and the improvements in oxygenation outlasted the NO inhalation. In the control/NO-late group, the NO inhalation reversed the changes in dead space and venous admixture. NO had no effect on the changes in respiratory mechanics.


CONCLUSIONS
In porcine ALI, 60 ppm NO diminishes pulmonary vasoconstriction and improves gas exchange by reducing pulmonary venous admixture and alveolar dead space, but does not prevent a fall in Crs. NO inhalation may help prevent long-lasting pulmonary failure.
Dahm
P L
PL
Department of Anaesthesia & Intensive Care, The Institute of Experimental Surgery, University Hospital of Lund, Sweden.
Jonson
B
B
De Robertis
E
E
Myhre
E
E
Svantesson
C
C
Thörne
J
J
Blomquist
S
S
D000280:Administration, Inhalation; D000403:Airway Resistance / Q000187:drug effects; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism; D004195:Disease Models, Animal; D019446:Endotoxemia / Q000188:drug therapy* / Q000503:physiopathology; D004927:Escherichia coli Infections / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D008170:Lung Compliance / Q000187:drug effects; D009569:Nitric Oxide / Q000008:administration & dosage / Q000627:therapeutic use*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000187:drug effects; D011312:Pressure; D011659:Pulmonary Gas Exchange / Q000187:drug effects*; D012123:Pulmonary Ventilation / Q000187:drug effects; D012126:Respiratory Dead Space / Q000187:drug effects; D012128:Respiratory Distress Syndrome / Q000188:drug therapy / Q000503:physiopathology; D015656:Respiratory Mechanics / Q000187:drug effects*; D012772:Shock, Septic / Q000188:drug therapy / Q000503:physiopathology; D013552:Swine; D014661:Vasoconstriction / Q000187:drug effects; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000627:therapeutic use*
D014665:Vasodilator Agents; D002245:Carbon Dioxide; D009569:Nitric Oxide; D010100:Oxygen