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Respiratory Part 10
Question | Answer |
---|---|
A-a gradient for O2 | A-a gradient is used to distinguish whether it is pulmonary or non-pulmonary. Larger the A-a gradient, the larger the mismatch/shunt |
Describe how the gas from the Alveolus with high PO2 mixes with gas from Alveolus with low PO2 | The resultant gas mixture is the arithmetic mean. |
Describe how blood with high PO2 mixes with blood with low PO2 | The resultant blood mixture is less than the arithmetic mean. |
What happens when blood leaves an alveolus with a low VA/Qc and mixes with blood from an alveolus with hihg VA/Qc? | The mixture will have a lower PaO2 than the mixed alveolar gas from which those bloods originated. |
True or False: A-a gradient is positional in a normal individual | True. When a person lays down the A-a gradient will go away. |
True or False: A-a gradient in individual with pulmonary disease is positional | False. No matter how the person is positioned, the A-a gradient will be there. |
True or False: A-a gradient is abnormal is individual with non-pulmonary disease | False. A-a gradient is normal when individual has non-pulmonary disease |
Dorsal Respiratory Group (DSG) | DSG of neurons in the medulla contains cells that discharge in phase with inspiration. The Ventral Respiratory Group fires with inspiration and expiration |
Mechanoreceptors in small airways | 1. Small airways-stretch receptors stretched in inspiration leads to increase in afferent activity to DRG. Cease inspiration so that the lung limits is size. |
Mechanoreceptors, free nerve endings (J-receptors) | Pulmonary edema. Causes rapid, shallow breathing |
Chemoreceptors (Peripheral) | Aortic body: Aff 10 to DRG, increase in VA. Carotid body: Aff 9 to DRG, increase in VA. |
Carotid body | Per gm of tissue receives more blood than any other. All needs for O2 can be utilizing O2 dissolved in blood. Only responds to PO2, can do w/o hemoglobin. Stimulus: Drop in PaO2 at about 60mmHg. Not responsible for breath by breath. Does not Adapt. |
What does a decrease in pH and fall in blood flow do to the carotid body? | Decrease in pH will lead to extremely deep and rapid pattern of breathing. A drop in blood flow can compromise O2 delivery to the carotid body. |
Central Chemoreceptors | Located on the ventrolateral surface of the medulla in contact with CSF. Stimulus: CSF H+ (reflection of CO2). It is very sensitive & responsible to breath by breath control. System does adapt. |
How does central chemorecptors adapt? | Usually takes about 12-24 hours. It adapts by pumping HCO3 into or out of the CSF. HCO3 buffers the acidosis caused by the H+ |
Severe pulmonary disease | Drop in PaO2 drives respiration. Increase in PaCO2 is adapted to. Peripheral chemoreceptors respond to hypoxia. |
In Anemia will A-a gradient be in normal range? | Yes |
What does the presence of Carbon monoxide do to O2 affinity to hemoglobin? | Makes O2 hang onto Hb much tighter. |