Lec 38 Control of Ventilation Flashcards
What is PaCO2 when you voluntarily hyperventilate?
20 torr, low
What is PaCO2 when you hold your breath?
55 torr, very high
What is PaCO2 when you fall asleep?
45 torr, a little high
what is PaCO2 when you exercise?
40 torr, normal
Where is the respiratory generator
the medulla
What happens to breathing if you make cut below medulla [so entire brainstem gone]?
stop breathing without medulla
what happens if you make cut above pons [so still have pons, medulla, spinal cord but no cortex?
get normal breathing
What are two main inspiratory muscles?
- external intercostals
- diaphragm
is external or internal intercostal expiratory muscle?
internal is expiratory
What is the pre-BOT complex?
acts as pacemaker for respiration in medulla
What 3 places are chemoreceptors located? which is most important
most important: in medulla
- also in carotid body and aortic body
What are 4 types of lung receptors
- stretch receptors
- J receptors
- irritant receptors
- chest wall receptors
Where are central chemoreceptors? what do they respond to?
- near surface of medulla on brain side of blood brain barrier
- fast response to small changes in CO2 [also respond to H+ but not as strongly]
Where are the peripheral chemoreceptors? What do they respond to?
- in carotid bodies and aortic bodies
- respond mostly to oxygen
- some respond to CO2
- also respond to changes in arterial pressure
What does increased CO2 do to minute ventilation?
increases minute ventilation
What is normal minute ventilation?
5 L/min
What is hypercapnic drive? value?
- the drive to decrease CO2
- normal value 2 L/min/Torr
means for every 1 torr you increase PCO3 by, you will increase minute ventilation by 2 L/min
What is shape of hypercapnic drive curve compared with hypoxic drive?
hypercapnic: linear
hypoxic:
When does hypoxic drive kick in?
pretty much kicks in at 60 mmHg
At what PO2 do you lose consciousness?
35 mmHg
What 2 things mediate hypoxic drive?
- carotid bodies
- aortic body
Can you be hypoxic with no dyspnea?
yes – this is very common since hypoxic drive is weak until very low [less than 60] PO2
When do stretch receptors increase firing? where are they located? function?
- increase firing with stretch [inflation] of lung
- located in airway smooth muscle
- decrease respiratory frequency
What is hering-breuer reflex?
- hyperinflation of lung causes apnea, inhibits inspiration so you exhale
What is the afferent part of stretch receptors?
vagus
What do irritant receptors in lung respond to? where are there located? What action?
- respond to chemical or mechanical irritation of airway [smoke, chem, dust, cold air]
- in receptors in superficial lining of airways
- increase respiratory frequencey
What is afferent part of irritant receptors?
vagus
What is afferent part of juxtacapillary receptors?
vagus
What do juxtacapillary [J] receptors respond to?
- pulmonary vascular congestion
- interstitial inflammation
- chemicals in pulm circulation
- pulmonary hypertension
- lung deflation
Where are chest wall receptors? what do they respond to?
- muscle spindles of intercostals, chest wall
- gives info about work of breathing –> if you are working too hard to breath it tells your brain
what is afferent part of chest wall receptors?
- spinal nerves
What are the two different general reasons for elevated PaCO2? Examples of each
Can’t do: your body physically can’t get rid of the CO2
- bad lungs, bad muscles
won’t do: your body is capable but not doing it, things that mess up CO2 drive
- drugs, medications, sleep related, ondine’s curse
Which stage of sleep takes up 50% of sleep time?
stage 2 non-rem sleep
What are the 3 stages of non-rem sleep?
stage 1: light sleep, easily arousable
stage 2: about 50% of sleep time
stage 3: slow wave or delta sleep
What is deepest/most refreshing stage of sleep?
stage 3
What is REM sleep?
- brain active, muscles nearly paralyzed including respiratory muscles
- paradoxical sleep
- dreaming sleep
- most cardiac and respiratory instability
What does increased CO2 do to minute ventilation?
increases minute ventilation
What is normal minute ventilation?
5 L/min
What is hypercapnic drive? value?
- the drive to decrease CO2
- normal value 2 L/min/Torr
means for every 1 torr you increase PCO3 by, you will increase minute ventilation by 2 L/min
What is shape of hypercapnic drive curve compared with hypoxic drive?
hypercapnic: linear
hypoxic:
When does hypoxic drive kick in?
pretty much kicks in at 60 mmHg
At what PO2 do you lose consciousness?
35 mmHg
What 2 things mediate hypoxic drive?
- carotid bodies
- aortic body
Can you be hypoxic with no dyspnea?
yes – this is very common since hypoxic drive is weak until very low [less than 60] PO2
What is voluntary hyperventilation?
- forcing yourself to hyperventilate to lower CO2 so you can hold breath longer
- what forces you to breathe when you are swimming is the CO2
- have more time breath holding before CO2 becomes unbearable but not much more O2 to consume
What is hering-breuer reflex?
- hyperinflation of lung causes apnea, inhibits inspiration so you exhale
What is the afferent part of stretch receptors?
vagus
What do irritant receptors in lung respond to? where are there located? What action?
- respond to chemical or mechanical irritation of airway [smoke, chem, dust, cold air]
- in receptors in superficial lining of airways
- increase respiratory frequencey
What is afferent part of irritant receptors?
vagus
What is afferent part of juxtacapillary receptors?
vagus
What do juxtacapillary [J] receptors respond to?
- pulmonary vascular congestion
- interstitial inflammation
- chemicals in pulm circulation
- pulmonary hypertension
- lung deflation
Where are chest wall receptors? what do they respond to?
- muscle spindles of intercostals, chest wall
- gives info about work of breathing –> if you are working too hard to breath it tells your brain
what is afferent part of chest wall receptors?
- spinal nerves
What are the two different general reasons for elevated PaCO2? Examples of each
Can’t do: your body physically can’t get rid of the CO2
- bad lungs, bad muscles
won’t do: your body is capable but not doing it, things that mess up CO2 drive
- drugs, medications, sleep related, ondine’s curse
Which stage of sleep takes up 50% of sleep time?
stage 2 non-rem sleep
What are the 3 stages of non-rem sleep?
stage 1: light sleep, easily arousable
stage 2: about 50% of sleep time
stage 3: slow wave or delta sleep
What is deepest/most refreshing stage of sleep?
stage 3
What is REM sleep?
- brain active, muscles nearly paralyzed including respiratory muscles
- paradoxical sleep
- dreaming sleep
- most cardiac and respiratory instability
What does sleep do to ventilatory drive
lowers it
What happens to breathing in slow wave [stage 3] sleep?
very regular breathing [ and heartbeat]
body on autopilot
What happens to ventilatory drive in REM sleep? muscle tone?
- biggest decrease in ventilatory drive
- greater dependence on diaphragmatic function
- decreased muscle tone
What happens to PCO2 on transition to sleep?
rises 2-6 torr
What is definition of sleep apnea?
stopping breathing for at least 10 seconds at least 10 times per hour
What are two types of sleep apnea? which is more common
central: ventilatory drive problem
- ex. obesity
obstructive = more common
What is ondine’s curse?
- rare disease
- congenital central hypoventilation syndrome
- defect in PHOX2b gene
What is Cheyne-Stokes respiration? What is example of why it happens
- periodic breathing wtih central apneas
- best ex: CHF with increased circulation time so get delayed thermostat = delayed/slow to turn on and then slow to turn off
- receptors not working really well
What happens to CO2 and O2 in volutnary hyperventilation?
- very decreased CO2
- increased PaO2, not much actual increase in content of oxygen in blood
