Phys 54: Chem Control

Front 1

Why does alveolar CO2 and O2 increase when breathing CO2 enriched mixture

Back 1

CO2 will increas because inspired CO2 increases. PO2 increases because breathing increases (compensate by hyperventilating)

Front 2

Why does breating rate increase when breathing elevated CO2

Back 2

Activation of carotid (fast) and intracranial (slower) chemo's stimulates breathing

Front 3

Describe a subjects H+ status during CO2 breathing

Back 3

acute respiratory acidosis

Front 4

Describe the affects of chronic alveolar hypoventilation on breathing and plasma H+

Back 4

To compensate for the acidosis caused by hypoventilation, the kidneys generate increased bicarb to restore plasma pH to near normal. The chemorecepotrs also become less sensitive to hypecapnia and any residual acidosis.

Front 5

Wy does alveolar CO2 and O2 decrease when breathing a hypoxic gas mixture?

Back 5

O2 decreased because inspired O2 is reduced. CO2 decreases because of increased breathing (hyperventilation)

Front 6

Compare the rate of breathing when inspiring a CO2 enriched mixture to a hypoxic mixture

Back 6

The high CO2 mixture increases breahting more than the low O2 mixture due to the differences in sensitivty of the 2 sets of chemoreceptors. CO2 is more important than O2 in regulation eupneic breathing.

Front 7

How would you characterize a subject's H status druing hypoxia

Back 7

usually acute respiratory alkalosis develops during breif periods of hypoxia because there is an increase in breathing rate and therefore less CO2

Front 8

Describe the "phases" that occur over the course of chronic hypoxia

Back 8

1. intial hypernea caused by actication of carotid O2 chemoreception 2. return to normal breathing caused by attenuated sensitivty and hypoxic brain depression 3. a second increase in breathing caused by increased sensitivy to hypoxia of carotid chemo's 4. return to normal breathing caused by attenutaiton of carotid chemo's (phase 4 only occurs at high altitude or in children because there is increased lung growth)

Front 9

WHat is hypoxic brain depression

Back 9

refers to the direct depressant effect of hypoxia on the excitabilty of neurons, occus during phase 2 of adaptation to hypoxia as the breathing rate returns to normal

Front 10

Describe how breathing rate changes over time in resopnse to hypoxia in an adult who is not native to a high altitude area

Back 10

1. initial increase (activation of chemo's) 2. Decrease (decreased sensitivity of chemo's and HBD) 3. increase and maintenacne at elevated rate (increased sensitivty to hypoxia)

Front 11

In which situation would a subject likely experience dyspnea-breathing a high CO2 mixture or a low oxygen mixture

Back 11

More likley to feel dyspnea with high CO2 because there is a more dramatic effect on breathing rate because the chemo's are more sensitivey to high CO2 than low O2

Front 12

Describe congenital central alveolar hypoventilation

Back 12

absent CO2/H chemo sensitivity, absent carotid hypoxic sensitivity, central sleep apnea but normal exercise hyperpnea, airway reflexes and mechanics. Tx w/ diaphragm pacing or mechanical ventilation during sleep.

Front 13

What is the primary stimulus for hypernea when breathing elevated CO2

Back 13

intracranial chemoreceptors

Front 14

What happens to PaO2 when breathing increase CO2

Back 14

increases because breathing rate increases

Front 15

What is the affect of breathing increased CO2 on tidal volume

Back 15

Tidal volume increases as breathing rate increases

Front 16

When does the PaO2 stabilize when breathing a hypoxic gas mixture

Back 16

continues to decline for several minutes until the reserve of O2 in the FRC is used up, then approcahes inspired pressure

Front 17

How will breathing a hypoxic gas mixture affect intracranial chemoreceptor activty

Back 17

activity will incrase because the hypoxia leads to an increased breathing rate which decreases PCO2 which leads to a respiratory alkalosis

Front 18

Compare the decrese in alveolar O2 pressure and arterial O2  saturation when insipiring increasingly hypoxic mixtures

Back 18

There will be a greater relative decrease in the pressure of Oxygen in the alveoli  than the saturation of oxygen in the arteries because the oxygen in the ateries can remain bound to Hb over a wide range of oxyen pressures (you can go from a P of 100 to 60 and still remain ~95% saturated)