Effects of pulsed inhaled nitric oxide delivery on the distribution of pulmonary perfusion in spontaneously breathing and mechanically ventilated anesthetized ponies.

The research article investigates the impact of pulsed inhaled nitric oxide (PiNO) on pulmonary perfusion, especially in anesthetized ponies, whether they are spontaneously breathing or mechanically ventilated. The study concluded that PiNO delivery leads to an improvement in oxygenation by redirecting pulmonary perfusion from lung regions affected by atelectasis to aerated ones.

Methodology

• The study was conducted using 6 adult ponies were anesthetized and placed in dorsal recumbency inside a CT gantry. The ponies were allowed to breathe spontaneously, while pulmonary artery, right atrial, and facial artery catheters were positioned.
• Analysis time points were set at the baseline, following 30 minutes of PiNO, and 30 minutes post-ceasing of PiNO.
• At each point, an iodinated contrast medium was injected, and CT angiography was used to gauge pulmonary perfusion. Thermodilution measured the cardiac output, with arterial and mixed venous blood samples collected simultaneously and later analyzed.
• This procedure was then repeated with the ponies under mechanical ventilation.

Results

• During PiNO delivery, pulmonary perfusion increased to aerated lung regions and decreased to atelectatic (collapsed or shrunken) ones.
• The arterial partial pressure of oxygen increased, while the venous admixture and the alveolar-arterial difference in oxygen’s partial pressure saw a decrease.
• Changes in regional perfusion while administering PiNO were more pronounced in ponies that were spontaneously breathing compared to those under mechanical ventilation.

Conclusions

• Overall, PiNO application in anesthetized, dorsally recumbent ponies led to a redistribution of pulmonary perfusion. This transition took place from dependent, atelectatic lung regions to nondependent aerated regions, triggering enhancements in oxygenation.
• Based on the observed outcomes, PiNO may present as a potential treatment solution for oxygenation impairments prompted by recumbency.