CO2 Ventilatory Response Curve APEX (question 19) respiratory material

What is the difference between the right and left shift of the CO2 ventilatory response curve? What happens with the slope of the curve with the right shift and the left shift?(Think what happens with alveolar ventilation and PaCO2 levels). Respiratory acidosis or alkalosis for the right and left shift?

- A Left shift has an increased slope, this indicates that Ve(alveolar ventilation) is higher than expected for a given PaCO2, this creates a respiratory alkalosis -A right shift will result in a decreased slope. Indicates that Ve (alveolar ventilation) is decreased (hypo ventilation) for a given PaCO2, this results in respiratory acidosis

What is the MAC of CO2?

200mmHg

What happens with the apneic threshold with a left and right shift?

A left shift implies that the apneic threshold has decreaed A right shift implies that the apneic threshold has increased

What is the range PaCO2?

PaCO2 range is between 20-80mmHg

Look at the slope of the curve in APEX. Study it and explain it. What does the curve represent?

Represents the sensitivity of the entire respiratory apparatus to PaCO2

What are the central chemoreceptors? Where are the located? What do they monitor?

The central chemoreceptors are located in the medulla and primarily monitor PaCO2

What is the apneic threshold? What occurs once the PaCO2 moves beyond the apneic threshold?

This is the highest PaCO2 in which a person will not breathe. Once the PaCO2 exceeds the patients apneic threshold, they will begin to breathe

What does the CO2 ventilatory response curve describe the relationship between?

Describes the relationship between PaCO2 and minute ventilation

What things can cause a left shift in the CO2 ventilatory response curve?

1) hypoxemia 2)metabolic acidosis 3)surgical stimulation 4)CNS etiologies (increased ICP, fear, anxiety) 5)drugs: (salicylates, aminophylline, doxpram, and NE)

What things can result in the right shift of the CO2 ventilatory response curve?

1) metabolic alkalosis 2)carotid endarterectomy 3)natural sleep 4)drugs: (volatile anesthetics, opioids, NMBs) -remember, opioid antagonists do not affect the curve

Is CO2 a respiratory stimulant or a respiratory depressant? Why?What happens to minute ventilation?

BOTH PaCO2's range is between 20-80 mmHg. As the PaCO2 increases, there is a linear increase in minute ventilation (respiratory stimulant) When PaCO2 reaches beyond 80-100mmHg, then this can result in respiratory depression

Where are the peripheral chemoreceptors located? What do they play a role in?

Located in the carotid bodies and the transverse arch of the aorta. They play a secondary role in monitoring PaCO2