High-altitude effects on respiratory gases, acid-base balance and pulmonary artery pressures in equids.

The research study investigates the impact of high altitudes on the respiratory gases, acid-base balance, and pulmonary artery pressures in equids (a family of horses). The study finds that high altitudes lead to significant changes in the respiratory system and the most profound changes occur during the initial three days.

Study Methodology

• The study was conducted on six equids that were exposed to an altitude of 3800 meters for a period of 10 days.
• The arterial and venous blood of the equids were analyzed both at rest and post-exercise for several parameters such as pH levels, PCO2 (partial pressure of carbon dioxide), PO2 (partial pressure of oxygen), and bicarbonate concentrations. Furthermore, base excess and strong ion difference were calculated as part of the research methodology.

Findings on Respiratory Gases

• The equids experienced a profound hypoxia-hypocapnia, a condition characterized by decreased oxygen and carbon dioxide in the blood, and a respiratory alkalosis, which is an increased alkalinity (reduced acidity) of the blood and body tissues. This is seen in the decrease of 42% in PaO2 and 41% in PaCO2.
• The PaCO2, which is the partial pressure of carbon dioxide in arterial blood, increased to 80% of the initial values after 8 days at altitude, indicating a degree of recovery in the respiratory system in response to the altitude change.

Findings on Acid-Base Balance

• The study found that arterial bicarbonate concentration decreased by 34% initially, but it returned to the normal level by Day 4 of the altitude exposure, indicating a successful physiological adaption in the equids.
• The base excess, an indicator of the acid-base balance in the blood, also decreased initially but stabilized at altitude with time.
• However, the strong ion difference, an essential tool for understanding acid-base balance, remained depressed during the entire altitude exposure and even after the return to the lower altitude.

Findings on Pulmonary Artery Pressure

• The study measured the resting pulmonary artery pressure (PAP) and found that it increased by 63% on the first day of altitude exposure.
• However, thirty-six hours after returning to a lower altitude, most variables including the PAP, returned to their normal values with the exception of Strong Ion Difference (SID) and post exercise base excess.

Conclusion

• The research confirms that high altitude exposure induces major changes in the respiratory gases, acid-base balance, and pulmonary artery pressure in equids.
• The most substantial changes were observed during the first three days of altitude exposure and the adaptation process was led by the return of bicarbonate concentration to the normal level.