Pulmonary blood flow distribution in anesthetized ponies.

The researchers investigated the factors that affect how blood is distributed in the lungs of ponies. They found that factors other than gravity play a major role in determining these blood flow patterns.

Research Methods

• The study was carried out on five prone ponies under the influence of pentobarbital sodium anesthesia.
• Pulmonary blood flow distribution was examined by the injection of 15-microns radionuclide-labeled microspheres.
• Post the experiments, the ponies were euthanized, and their lungs were excised, inflated with air, and dried.
• The dried lungs were sliced transversely, along the dorsal-ventral axis parallel to gravity. The slice thickness ranged between 1-2 cm.
• Radioactivity levels of pieces cut from alternate slices were then measured with a gamma well counter.

Key Findings

• The researchers discovered a preferential distribution of pulmonary blood flow to the dorsal-caudal regions and a higher flow in the center of each lung slice, as compared to the slice periphery.
• Lower flow was observed in the cranial and ventral areas.
• Apart from that, differences of about +/- 2 SD were found between the core and peripheral blood flow, but no medial-lateral differences were noted.
• The researchers also found that the pulmonary blood flow distribution remained consistent over 5 hours of anesthesia and was not different between the left and right lung.

Conclusions

• From the results, the researchers suggested that in mechanically ventilated ponies that were intact and prone, factors other than gravity are primary determinants of pulmonary blood flow.
• This research built upon previous studies in humans and dogs, and it further emphasized the importance of non-gravitational factors in determining pulmonary blood flow distribution.