Distribution of ventilation-perfusion ratios in paraquat-induced interstitial pneumonia in dogs
Ogasawara, H.
Hokkaido Journal of Medical Science 71(2): 259-270
1996
ISSN/ISBN: 0367-6102 PMID: 8641680 Document Number: 459971
To clarify the mechanism of hypoxemia observed in interstitial lung diseases we investigated the ovrhdot VA/ ovrhdot Q distribution in the paraquat-induced pneumonitis of the dogs. Sixteen mongrel dogs were given 20mg/kg of paraquat per os repeatedly with the dose and times of administration modified according to the general status of the dogs. Ventilation-perfusion relationships were measured using multiple inert gas elimination techniques, and these parameters were compared to arterial blood gases. The same procedures were also done in 11 normal dogs. Arterial oxygen tension (Pao-2) was significantly lower and alveolar-arterial oxygen gradient (A-aDo-2) was significantly larger in paraquat dogs than normal dogs. In ovrhdot V-A/ ovrhdot Q measurement of paraquat dogs, mean shunt was 5.3% (range 0-28.8%), and there was a mean of 10.0% of blood flow to very low ovrhdot V-A/ ovrhdot Q units ( ovrhdot V-A/ ovrhdot Q lt 0.1, range 0-43.4%). These values were larger than those of normal dogs (p lt 0.05, respectively) but dogs with large shunt or blood flow to low ovrhdot V-A/ ovrhdot Q units were not many in paraquat group. In the paraquat dogs, PaO-2 significantly correlated with a shunt (r = -0.69, p lt 0.01) and blood flow to low ovrhdot V-A/ ovrhdot Q ( lt 0.1) units (r= -0.77, p lt 0.01) and it also correlated with dispersion of blood flow (log SD(Q), r= -0.66, p lt 0.01). Pathological study of paraquat lungs showed large variety of interstitial pneumonia and fibrosis, and morphometrical analyses did not demonstrate structure-function correlation in paraquat dogs. From these results, we concluded that ovrhdot V-A/ ovrhdot Q mismatch including increased very low ovrhdot V-A/ ovrhdot Q units is important as a cause of arterial hypoxemia in interstitial lung diseases.