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Pulm > Lec 6 Control of breathing > Flashcards

Lec 6 Control of breathing Flashcards

1
Q

The most important stimulus for ventilatory drive is:
A) Oxygen saturation
B) Pa O2
C) Pa CO2

A

C) PaCO2

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2
Q

At maximal levels of exercise:

A) arterial blood gases show elevated PaCO2

B) arterial blood gases show reduced PaO2

C) arterial blood gases show normal PaCO2 and PaO2

A

C) arterial blood gases show normal PaCO2 and PaO2

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3
Q 
Assuming a reasonable number of hours of sleep, the most common reason to be sleepy during the day is
A) Obstructive Sleep Apnea
B) Central Sleep Apnea
C) Depression
D) Narcolepsy
A

A) Obstructive Sleep Apnea

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4
Q

Normal PaO2?

A

90-100

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5
Q

Normal PaCO2?

A

40

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6
Q

Normal pH?

A

7.4

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7
Q

paCO2 if you

  • hold your breath?
  • fall asleep?
  • exercise?
  • hyperventilate?
A

hold breath: 55

fall asleep: 45

exercise: 40
hyperventilate: 20

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8
Q

What generally happens in respiration?

A
  • brain signals phrenic nerve to send signals to inspiratory [mostly diaphragm] muscles –> causes diaphragm to contract and pull down leading to inspiration
  • expiration is passive
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9
Q

Where are the centers that initiate breathing located?

A

in medulla beneath floor of 4th ventricle

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10
Q

Where is the dorsal respiratory group located? action?

A
  • in nucleus tractus solitarius
  • mostly inspiratory neurons
  • receive afferents from CN9 and CN10
  • main site for driving phrenic nerve
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11
Q

What is the ventral respiratory group? action?

A
  • contains inspiratory and expiratory neurons

- main respiratory pacemaker

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12
Q

What is the apneustic center?

A

in the pons = site of neurons which normally turn off inspiration

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13
Q

What sets normal respiratory rhythm?

step1

A

pre-botzinger complex in the VRG [ventral respiratory group] of medulla

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14
Q

What is the pneumotaxic center?

A

in pons; modulates apneustic center

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15
Q

What are main afferents to central respiratory center?

step1

A

CN 9 (glossopharyngeal) and CN 10 (vagus)

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16
Q

Where are central chemoreceptors? action?

step1

A
  • near surface of medulla
  • on brain side of blood brain barrier
  • stimulated by change in pCO2 [directly measures pCO2/pH of blood interstitial fluid which is influence by arterial CO2]
  • quicker response to respiratory acidosis than metabolic acidosis b/c CO2 can diffuse across BBB and H+ cant
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17
Q

Where are the peripheral chemoreceptors? what stimulates them?

step1

A
  • carotid and aortic bodies = between external/internal carotid branch and on top of aortic arch
  • mostly respond to pO2 < 60
    also respond to
  • high PCO2
  • low pH
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18
Q

What are steps of baroreceptor reflex in hypotension?

step1

A

hypotension –> decrease arterial P –> decrease stretch –> decrease afferent baroreceptor firing –> increase efferent sympathetic and decrease efferent parasympathetic –> vasoconstriction, increase HR, increase contractility, increase BP

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19
Q

Does baroreceptor fire more with hypotension or hypertension?

step1

A

fires more with hypotension

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20
Q

Does signal to increase ventilation in response to chemoreceptors cause greater increase in rate or tidal volume?

A

greater increase in tidal volume

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21
Q

What is the slope of hypercapnic ventilation drive?

A

2 L/min/torr

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22
Q

What happens minute ventilation in person if PCO2 increase from normal 40 to 43?

A

hypercapnic drive = 2 L/min/torr
so if we increase by 3 torr –> increase ventilation rate by 6 L/min

normal = 6 L /min so we can more than double minute ventilation

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23
Q

IF someone who looks comfortable has a PCO2 of 45 what should you think?

A

they must have a chronic pulmonary problem

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24
Q

What is normal minute ventilation?

A

5-6

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25
What happens to hypercapnic drive in response to hypoxemia?
in hypoxia hypercapnic drive increases = we are more sensitive to PCO2 when we don't have enough O2
26
What happens to ventilation drive with hypoxia?
very little change in ventilation with decreased PO2 until you reach ~ 60 torr then exponential increase with further hypoxia
27
At what PO2 do you lose consciousness?
35 torr
28
What happens if you plot O2 sat vs ventilation rate [rather than PO2 vs ventilation]?
relationship is linear | --> increase ventilation wen decrease O2 sat
29
Do peripheral chemoreceptors respond to O2 sat or PO2?
PO2
30
What symptoms if you are hypoxic?
may be asymptomatic; not uncommon to be hypoxic with little or no dyspnea
31
What are the types of lung receptors?
- stretch receptors = increase firing with inflation of lung - J receptors = next to capillaries; respond to inflammation or fluid in interstitium by increasing rate - nociceptors = respond to chemicals/smoke/dust to stimulate ventilation by increasing resp frequency - chest wall receptors = in muscle of chest wall; feedback to respiratory centers about work of breathing
32
What is the definition of hypoventilation?
elevated PCO2
33
What is can't do vs won't do hypoventilation?
can't do = decreased pulmonary function from bad lungs or muscle won't do = decreased ventilatory drive from drugs/meds, sleep related, or ondine's curse
34
What are the 3 stages of non-rem sleep?
stage 1 = light sleep, easily arousable stage 2 = deeper sleep, about 50% of the time stage 3 = slow wave or delta sleep = most refreshing
35
What kind of sleep decreases most with age?
stage 3 sleep
36
What is cheyne-stokes respiration?
specific pattern of periodic breathing seen mostly in sleep respiration waxes/wanes with period of apnea betwen cycles seen with neurologic disease or CHF its a feedback control problem related to circulation time = like delayed thermostat
37
What is REM sleep?
- brain is active, muscles nearly paralyzed including respiratory muscles - most cardiac and respiratory instability
38
What happens to PCO2 in sleep?
rises 2-6 torr
39
What is breathing like in stage 3 [slow wave] sleep?
- very regular breathing and HR | body on autopilot
40
What happens to breathing in REM sleep
- decrease in ventilatory drive - greater dependence on diaphragmatic function - decreased muscle tone --> if you are dependent on muscle tone you will get problems here; if you die in your sleep most likely REM
41
What is obstructive sleep apnea?
- sleep apnea cause by diminished diameter of airway - decreased muscular activity + supine posture creates obstruction you keep trying to breath but you cant have really loud snoring
42
What is sleep apnea?
repeated cessation of breathing for > 10 seconds during sleep 5 or more times / hr
43
Who most commonly gets obstructive sleep apnea?
- obese | - those with family hisotry
44
Is obstructive or central sleep apnea more common?
obstructive
45
What causes central sleep apnea?
obesity or ondines curse
46
What is ondine's curse?
- congenital central hypoventilation syndrome - due to defect in PHOX2b gene - causes central sleep apnea
47
What is mild vs moderate vs severe sleep apnea?
``` mild = 5-15 times /hr sleep stop breathing moderate = 15-30 times / hr severe = > 30 times / hr ```
48
Sleep apnea puts you at risk for what diseases? step1
- coronary artery disease - stroke - CHF - systemic/pulp HTN - arrhythmias [AFib/flutter] - sudden death
49
What are signs/symptoms of sleep apnea?
- snoring | - daytime sleepiness
50
How does exercise change ox cunsumption?
- increases ox consumption - increases minute ventilation - arterial blood gases unchanges
51
What is respiratory system response to exercise? step1
- increase CO2 production - increase O2 consumption - increase ventilation to meat O2 demand - increase pulm blood flow to increase CO - decrease pH during strenuous exercise - no change PaO2 and PaCO2 but increase in venous CO2 and decrease venous O2
52
What happens to O2/CO2 in arteries in exercise? what about in veins? step1
- no change PaO2 and PaCO2 | - increase in venous CO2 and decrease venous O2
53
What is fick principle equation?
Qt [CO] = VO2 / (CaO2 - CvO2) | = ox consumption / (arterial O2 - venous O2)
54
What is the equation for CaO2 oxygen content? step1
CaO2 = 1.34 * Hb * SaO2 + 0.003 * PaO2 ``` SaO2 = usually closet to 1 PaO2 = usually 100 ```
55
How does minute ventilation change in exercise?
Ve = Vt * frequency - increase tidal volume and frequency
56
What is the anaerobic threshold?
threshold of exercise [oxygen uptake] after which you start building up lactate = function of how good your heart is [not your lungs] usually about 40% of your max oxygen uptake
57
How do you increase muscle oxygen extraction in exercise?
- shunt blood from other organs [at rest muscles = 20% of CO; in max exercise 80%] - increase CO
58
What is limiting factor on exercise?
mostly limited by CO not by lungs
59
What happens to O2 hemoglobin dissociation curve in exercise?
shifts to the right --> hemoglobin decrease affinity; increase P50
60
What are the risk factors for obstructive sleep apnea?
- obesity - crowded upper airway - male - advanced age - family history - drugs and meds - HTN and AFib
61
What is obesity hypoventilation syndrome?
- morbid obesity (BMI > 30) --> hypoventilation --> decrease PaO2 and increase PaCO2 during waking hours hypoventilation during sleep without much apnea; particularly occurs in REM sleep
62
What is treatment for sleep apnea?
CPAP, surgery, weight loss

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