The effect of inspired gas density on pulmonary artery transmural pressure and exercise induced pulmonary haemorrhage.

The research article investigates the effect of gas density on pulmonary artery pressures and how it affects exercise-induced hemorrhage in horses. The experiment concludes that the density of the inhaled gas doesn’t cause significant variations in these parameters, and hence, does not affect the extent of hemorrhage during exercise.

Objective

• The research aims to determine the role of the respiratory system and the type of gas inhaled on the occurrence and severity of Exercise Induced Pulmonary Haemorrhage (EIPH) in horses.

Methods

• A total of 8 Thoroughbred horses were subjected to exercise sessions while breathing different types of gases: air, 21% oxygen/79% helium, or 21% oxygen/79% argon.
• During exercise, heart rate, respiratory rate, pulmonary arterial pressure, and oesophageal pressure were measured.
• 40 minutes post-exercise, Bronchoalveolar lavage fluid (BALF) was collected from different regions of the lungs and red blood cell (RBC) counts were made. This helped in evaluating the extent of EIPH.

Results

• The tests resulted in mild EIPH in the horses, with little variation across the different gas mixtures.
• Changes in esophageal pressure were lower on the helium-oxygen mix compared to the argon-oxygen mix. However, the transmural pulmonary arterial pressures (TPAP) and median RBC counts were similar across all gas mixtures.
• RBC counts from left and right lungs were significantly correlated.
• RBC counts were higher in the left lung as compared to the right.

Conclusions

• The results indicate that altering the inspired gas density does not significantly affect TPAP or EIPH severity, as changes in it aligned with the alterations in esophageal pressure.
• Hence, interventions that bring down the fluctuating intrapleural pressure may only decrease EIPH to some degree in horses that are severely affected by the condition.