REGULATION OF ALVEOLAR VENTILATION high altitude vs acclimatization

Question 1

ALVEOLAR VENTILATION

Answer 1

• mediated by
• CENTRAL CHEMORECEPTORS
• PERIPHERAL CHEMORECEPTORS

Question 2

CENTRAL CHEMORECEPTORS

Answer 2

• in the MEDULLA of the brain
• MONITOR MAINLY ARTERIAL CARBON DIOXIDE
• monitor hydrogen ions
• main drive for alveolar ventilation

Question 3

PERIPHERAL CHEMORECEPTORS

only ARTERIAL OXYGEN MAIN JOB

Answer 3

• located in the CAROTID SINUS AND AORTIC ARCH
• monitor arterial OXYGEN MAINLY
• LEAST extent monitor arterial CO2

Question 4

PERIPHERAL CHEMORECEPTORS
(only ARTERIAL OXYGEN MAIN JOB) takes over the job of CENTRAL CHEMORECEPTORS (only MONITOR MAINLY ARTERIAL CARBON DIOXIDE)

Answer 4

• when there is dramatic fall in PaO2

Question 5

arterial hydrogen ions

Answer 5

• cannot cross the BBB area

- any H+ ions affecting or stimulating the central chemoreceptors come from INFECTION IN THE CSF (meningitis)

Question 6

MENINGITIS

Answer 6

• hyperventilation
• due to excessive production of H+ ions in the CSF due to infection stimulating the central chemoreceptors
• increase H+ in the blood it will not affect the chemical receptors because it will not cross the BBB

Question 7

chronic hypoventilation

Answer 7

• overdose of morphine and heroin
• it will suppress the MEDULLA causing depression of ventilation causing hypoventilation
• causing INCREASE IN CARBON DIOXIDE it will stimulate central receptors, in cases of overdose it blocks central receptors causing it not to control the increase in carbon dioxide
• ## arterial oxygen DECREASES PaO2 stimulate peripheral receptors

Question 8

treatment of DECREASE PaO2

Answer 8

• dont correct the PaO2 to normal because we need to keep the peripheral receptor in play
• correcting the O2 to normal is removing the ventilatory drive of the patient, can cause collapse

Question 9

ANEMIA

Answer 9

• decrease total O2 content
• normal PaO2
• normal PaCO2
• no ventilatory changed

Question 10

CASE: from room air to oxygen mask 21% (same as room air)

Answer 10

• SAME/NORMAL ventilation

- central chemoreceptors

Question 11

CASE: from room air to oxygen mask 100% for 15 mins.

Answer 11

• SAME/NORMAL ventilation
• central chemoreceptors
• increasing O2 does not stimulate peripheral receptors and its just a waste in O2
• decreasing O2 stimulates peripheral receptors

Question 12

CASE: room air to 3% CO2 and 15% O2

normal CO2 in room air

Answer 12

• hyperventilation by peripheral chemoreceptors

- due to decrease in O2

Question 13

normal ventilation center

Answer 13

• medulla
• normal ventilatory rhythm EXPIRATION > INSPIRATION
• MOST COMMONLY AFFECTED IN STROKE PATIENTS

Question 14

ABNORMAL BREATHING PATTERNS

Answer 14

• APNEUSTIC BREATHING
• BIOT’S BREATHING
• CHEYNE-STOKES BREATHING

Question 15

APNEUSTIC BREATHING

Answer 15

• prolonged inspiration alternating with short period of expiration
• CAUDAL PONS LESION where pneumatic center is located (stroke)
• I > E

Question 16

BIOT’S BREATHING

Answer 16

• irregular patterns of APNEA
• seen in patients with INCREASED INTRACRANIAL PRESSURE
• MIDBRAIN LESION

Question 17

CHEYNE-STOKES BREATHING

Answer 17

• cycles gradually INCREASING IN DEPTH AND FREQUENCY followed by a GRADUAL DECREASE IN DEPTH AND FREQUENCY between periods of apnea
• lesion in the MIDBRAIN
• INFANTS
• during sleep in high altitude

Question 18

unusual environment

Answer 18

• increase altitude

- increase pressure

Question 19

INCREASE ALTITUDE

Answer 19

• O2 content is equal to PaO2 + HgB saturation + HgB concentration

Question 20

FACTORS DETERMINING HIGH ALTITUDE

PaO2 is determined by

Answer 20

• PAO2

Question 21

FACTORS DETERMINING HIGH ALTITUDE

PAO2 is determined by

Answer 21

• Patm

- fO2

Question 22

FACTORS DETERMINING HIGH ALTITUDE

HgB concentration is determined by

Answer 22

• O2 release by erythropoietin by the kidney

Question 23

FACTORS DETERMINING HIGH ALTITUDE

HgB saturation is determined by

Answer 23

• alveolar O2 (PAO2)

Patm and fO2

Question 24

HIGH ALTITUDE

Acute changes

Answer 24

1 - decrease Patm

#2 - decrease PaO2 and decrease PAO2 due to #1
- decrease PaCO2 and decrease PACO2 due to #2 peripheral chemoreceptors take place
- increase peripheral ventilation, increase systemic arterial pH CAUSING RESPIRATORY ALKALOSIS
- HYPERVENTILATION due to #2
- decrease HgB saturation due to #1 and # 2
- decrease O2 content
- no change HgB concentration

Question 25

alkalosis

Answer 25

- increase blood pH > 7.45

Question 26

alkalemia

Answer 26

- increase arterial blood pH > 7.45

Question 27

RESPIRATORY ALKALOSIS may be produced as a result of medical treatment (iatrogenically) during excessive mechanical ventilation.

Answer 27

Other causes include: - psychiatric causes: anxiety, hysteria and stress - CNS causes: stroke, subarachnoid haemorrhage, meningitis - drug use: doxapram, aspirin, caffeine and coffee abuse - moving into high altitude areas, where the low atmospheric pressure of oxygen stimulates increased ventilation - lung disease such as pneumonia, where a hypoxic drive governs breathing more than CO2 levels (the normal determinant) - fever, which stimulates the respiratory centre in the brainstem - pregnancy - high levels of NH4+ leading to brain swelling and decreased blood flow to the brain - vocal cord paralysis, compensation for loss of vocal volume results in over-breathing and breathlessness

Question 28

HIGH ALTITUDE | acclimatization 3-4 weeks the pH returned to NORMAL vs adaptation physiologic comes into play

Answer 28

#1 - decrease Patm #2 - decrease PaO2 and decrease PAO2 due to #1 - decrease PaCO2 and decrease PACO2 due to #2 peripheral chemoreceptors take place causing - increase in ventilation HYPERVENTILATION - SYSTEMIC arterial pH decrease to normal via renal compensation by decreasing production of HCO3 - increase HgB CONCENTRATION due to increase production of erythropoietin by the kidney - decrease HgB SATURATION due to #1 and # 2 - increase O2 content back to normal - POLYCYTHEMIA - INCREASED MITOCHONDRIA - ANGIOGENESIS - decrease PaO2 is due to increased cellular oxidative enzymes

Question 29

VENTILATION IS

Answer 29

- INVERSE TO CO2

Question 30

O2

Answer 30

- 21% | - side effects O2 toxicity

Question 31

nitrogen

Answer 31

- 79% of breath insoluble at sea level, it cannot dissolve or diffuse - dissolved in the plasma - nitrogen narcosis - caissons disease

Question 32

caissons disease (bends)

Answer 32

- breathing high pressure nitrogen for prolonged period - sudden decompression- nitrogen bubbles due to undissolving of nitrogen in plasma nitrogen narcosis same as air embolism

Question 33

treatment caissons disease (bends)

Answer 33

- repressurized | - redissolved the nitrogen to slowly release pressure

Question 34

decompression sickness

Answer 34

- gas bubbles blocking blood vessels