Physiology and Gas Laws Flashcards

According to Dalton's Law, if the total atmospheric pressure at sea level is 760 mmHg and oxygen comprises 21% of air, what is the partial pressure of oxygen (PaO2) at sea level?

Answer: 159.6 mmHg

Dalton's Law states that the partial pressure of a gas equals its fractional concentration multiplied by total pressure (0.21 × 760 = 159.6 mmHg).

A flight nurse is caring for a patient at 8,000 feet cabin altitude. Compared to sea level, which physiological change is expected in a healthy individual?

Answer: Increased respiratory rate to compensate for lower PaO2

At altitude, lower PaO2 stimulates peripheral chemoreceptors causing compensatory hyperventilation and increased respiratory rate.

Which gas law explains why a pneumothorax can expand during flight as the aircraft ascends to altitude?

Answer: Boyle's Law

Boyle's Law states that at constant temperature, gas volume varies inversely with pressure; as cabin pressure decreases at altitude, trapped gas expands.

The oxyhemoglobin dissociation curve shifts to the RIGHT in which of the following conditions encountered during flight?

Answer: Acidosis, hyperthermia, and increased 2,3-DPG

Acidosis, hyperthermia, hypercarbia, and increased 2,3-DPG shift the curve right, reducing hemoglobin's oxygen affinity and facilitating tissue oxygen release.

Henry's Law is most clinically relevant for the flight nurse when managing a patient with:

Answer: Decompression sickness after SCUBA diving

Henry's Law states that the amount of gas dissolved in liquid is proportional to its partial pressure; decompression sickness results from nitrogen bubbling out of solution as pressure decreases.

At a cruising altitude with a cabin pressure equivalent to 8,000 feet, the inspired partial pressure of oxygen (PiO2) is approximately:

Answer: 109 mmHg

At 8,000 feet, barometric pressure is approximately 565 mmHg; PiO2 = 0.21 × (565 - 47) = approximately 109 mmHg after subtracting water vapor pressure.

Which statement correctly describes the Fick Principle as it applies to oxygen delivery during aeromedical transport?

Answer: Oxygen consumption equals cardiac output multiplied by the arteriovenous oxygen content difference

The Fick Principle states VO2 = CO × (CaO2 - CvO2), making cardiac output and hemoglobin critical determinants of tissue oxygen delivery.