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Flashcards in Lec 6 Control of breathing Deck (62):
1

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

C) PaCO2

2

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

C) arterial blood gases show normal PaCO2 and PaO2

3

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) Obstructive Sleep Apnea

4

Normal PaO2?

90-100

5

Normal PaCO2?

40

6

Normal pH?

7.4

7

paCO2 if you
- hold your breath?
- fall asleep?
- exercise?
- hyperventilate?

hold breath: 55

fall asleep: 45

exercise: 40

hyperventilate: 20

8

What generally happens in respiration?

- 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

9

Where are the centers that initiate breathing located?

in medulla beneath floor of 4th ventricle

10

Where is the dorsal respiratory group located? action?

- in nucleus tractus solitarius
- mostly inspiratory neurons
- receive afferents from CN9 and CN10
- main site for driving phrenic nerve

11

What is the ventral respiratory group? action?

- contains inspiratory and expiratory neurons
- main respiratory pacemaker

12

What is the apneustic center?

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

13

What sets normal respiratory rhythm?

step1

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

14

What is the pneumotaxic center?

in pons; modulates apneustic center

15

What are main afferents to central respiratory center?

step1

CN 9 (glossopharyngeal) and CN 10 (vagus)

16

Where are central chemoreceptors? action?

step1

- 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

17

Where are the peripheral chemoreceptors? what stimulates them?

step1

- 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

18

What are steps of baroreceptor reflex in hypotension?

step1

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

19

Does baroreceptor fire more with hypotension or hypertension?

step1

fires more with hypotension

20

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

greater increase in tidal volume

21

What is the slope of hypercapnic ventilation drive?

2 L/min/torr

22

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

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

23

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

they must have a chronic pulmonary problem

24

What is normal minute ventilation?

5-6

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