Why was John instructed to avoid high altitudes and flying in non pressurized aircrafts?

John was instructed to avoid high altitudes and flying in non pressurized aircrafts because of the effects of decreased air pressure on the respiratory system. At high altitudes, there is a lower concentration of oxygen in the air, which can cause hypoxia, or a deficiency in the amount of oxygen reaching the tissues. This is due to the decreased atmospheric pressure at high altitudes, which causes the partial pressure of oxygen to decrease. Additionally, as altitude increases, the amount of air that can be taken in and expelled from the lungs decreases, making it more difficult to breathe.

In non-pressurized aircrafts, the cabin is not pressurized to sea level conditions, resulting in a decrease in atmospheric pressure as the aircraft climbs to higher altitudes. This can cause the same effects on the respiratory system as being at high altitudes, such as decreased oxygen concentration in the air and difficulty breathing.

In summary, high altitudes and flying in non-pressurized aircrafts can cause decreased air pressure, which can lead to hypoxia and difficulty breathing. As John’s lung had collapsed due to a spontaneous pneumothorax, he was at an increased risk of experiencing respiratory distress in situations where the air pressure was not at a normal level. Therefore, avoiding high altitudes and flying in non-pressurized aircrafts was an important precaution to ensure his safety and prevent further complications.

Reference: Gould, B. E. (2016). Pathophysiology for the health professions (5th ed.). Saunders.