Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
A 50-year-old man presents to you with chronic cough and swelling of the lower limbs. He states that he smoked 2 packs of cigarettes a day for the past 30 years. O/E you find that he is cyanosed and you hear expiratory wheezes all over his chest. You start him on supplemental oxygen through a nasal cannula. Shortly, you notice that his RR is slowing down. He has also become increasingly confused. This change in the patient's clinical condition is due to decreased stimulation of which of the following?
A. Central chemoreceptors
B. Pulmonary C fibers
C. Pulmonary stretch receptors
D. Carotid bodies
E. Juxtaglomerular apparatus
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
A- Central chemoreceptors..Thank you
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
it is D, in this pt has chronic hypercapnia, leading to desensitization of the central chemoreceptors, and his respitory drive becomes solely dependent on hypoxia, which is monitored by carotid bodies, and this is why administering O2 caused respitory depression.
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
D
when the pt was given oxygen. his CO2 level doesn't change immediately. instead, his oxygen level increase. Central chemoreceptor is response to CO2 and ph change while it is the carotid receptor response to CO2, ph and oxygen.
But I was reading somewhere saying central chemoreceptor changes the respiratory rate while peripheral chemoreceptor changes the tidal volume. Does anyone have any idea on this?
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
it is not related to the answer of the current question but FYI:
Pneumotaxic center
■ is located in the upper pons.
■ inhibits inspiration and, therefore, regulates inspiratory volume and respiratory rate.
from BRS physiology
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
DD
-respiratory drive is stimulated by
-----Central chemoreceptors that sense changes in pH and Pco2 of brain interstitial
fluid, which in turn are influenced by arterial CO2. Do not directly respond
to Po2.
----Peripheral chemoreceptors—carotid and aortic bodies are stimulated by Po2 (< 60 mmHg),
high Pco2, and low pH of blood.
This pt is having probably COPD--> Chronic hypercapnia--> adaptation of the Central chemoreceptors to chronic high pCO2. but the Peripheral chemoreceptors are still stimulated by the low PO2. If you bring the PO2 high, there is no more stimulation to the respiratory drive..
Similar situation occurs in morphine overdose.
Thank you for the question.
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
D
but in the question it supposed to say high flow O2
now if suppression to the carotid receptor occurs then we should decrease the flow of
O2
Posts: 3,675,937
Threads: 734,344
Joined:
Sep 2021
Reputation:
5
"D" is correct as explained.
You are welcome.
