Certified Flight Registered Nurse (CFRN) Practice Exam

When transporting a patient on a ventilator, what FiO2 setting adjustment is needed if the altitude changes the pressure from 700 torr to 500 torr?

1. 0.40 FiO2

2. 0.56 FiO2

3. 0.70 FiO2

4. 0.32 FiO2

The correct answer is: 0.56 FiO2

When transporting a patient on a ventilator between altitudes where the atmospheric pressure changes significantly, such as from 700 torr to 500 torr, it is essential to understand how these changes affect the delivery of oxygen. At lower atmospheric pressures, the partial pressure of oxygen decreases, which can lead to lower oxygen availability in the inspired air. In this scenario, with a decrease from 700 torr to 500 torr, the reduction in barometric pressure necessitates an adjustment in the fraction of inspired oxygen (FiO2) to maintain adequate oxygen levels in the patient's blood. To ensure that the patient receives a sufficient supply of oxygen despite the altitude's influence, the FiO2 would need to be increased. A setting of 0.56 FiO2 is calculated to compensate for the drop in ambient oxygen pressure due to the reduced atmospheric pressure, ensuring that oxygen saturation remains stable in the patient. This adjustment helps mitigate the risk of hypoxemia during transport at high altitudes where the environmental conditions could otherwise diminish the effectiveness of oxygen delivery. Thus, the choice that indicates an adjustment to 0.56 FiO2 is consistent with the physiological and mechanical demands placed on the ventilated patient in a lower pressure environment.