Group 3 - Respiratory Physiology Quiz

• During what kind of procedure would you expect a unilateral impairment of the hypoxic ventilatory response? 

• Hint: consider the location of the carotid bodies and the function of the hypoxic ventilatory response.

Answer explanation

• Carotid endarterectomy 

• Anesthesia implications: during a carotid endarterectomy, the afferent limb of the hypoxic ventilatory response is severed - this would unilaterally affect the peripheral chemoreceptors ability to respond to low oxygen content. This is also part of the reason why bilateral CEA are not performed.

Give one example of an agent that obliterates hypoxic pulmonary vasoconstriction and one anesthetic implication of this dysfunction?

Answer explanation

All volatile anesthetics impair HPV - one example of when this would have a negative consequence would be if a patient had an increased A-a gradient from a disease like COPD. The impairment of HPV from the volatile agent would increase the shunting the patient already has.

• Calculate the A-a gradient given the following values: 

  • FiO2: 50 

  • Atmospheric pressure: 718 mmHg

  • PaCO2: 73 mmHg

  • PaO2: 57 mmHg

You decide to give an amp of sodium bicarbonate for a patient who is acidotic. A few minutes later, you notice their EtCO2 level increase. This is because sodium bicarbonate dissociates into Na+ and HCO3-. HCO3- then reacts with H+ to form ________ ____, which then dissociates into CO2 and H2O

Regarding the Haldane effect, deoxygenated hemoglobin will cause a ____ shift which results in increased CO2 loading at the capillaries, while oxygenated hemoglobin will cause a _____ shift which results in CO2 offloading at the lungs.

• What is one potential cause of a leftward-shift in the CO2 ventilatory response curve?

• metabolic acidosis

• metabolic alkalosis

• deep anesthesia

• narcotic administration

in the left lateral decubitus position, which lung (dependent or nondependent) corresponds with the following description: Blood flow is increased, ventilation is increased, the alveoli are highly compliant, and the V/Q ratio is relatively lower.

What is P50?

What are examples of conditions that can cause a low or high P50?

Answer explanation

P50 is the PaO2 where hemoglobin is 50% saturated by O2

Lower P50 reflects left shift

Higher P50 reflects right shift

Based on the following values, what is the DO2 (ml/min)?

Hgb: 9 (g/dL) 

SaO2: 81 (%)

PaO2: 50 (mmHg)

CO: 5 (L/min)

What is the most common V/Q mismatch in PACU and why? What is the name of the Law that governs this?

Answer explanation

Atelectasis - resulting from decreased FRC and less radial traction to hold the airways open

Law of Laplace - Tension = (pressure * radius) / 2