Ventilation

Question 1

Why are respiratory adjustments needed in health and disease?

Answer 1

To maintain arterial PO2 and CO2 within normal limits

Question 2

What are the changes in oxygen delivery during exercise?

Answer 2

Increased O2 needs and CO2 output, increased minute and alveolar ventilation, increased pulmonary blood flow, increased diffusing capacity

Question 3

Define hypoxia

Answer 3

Oxygen deficiency at tissue level

Question 4

What are the types of hypoxia?

Answer 4

• Hypoxic hypoxia (hypoxaemia)
• Anaemic hypoxia
• Stagnant/ischaemic hypoxia
• Histotoxic/cytotoxic hypoxia

Question 5

What physiological changes occur during exercise?

Answer 5

Increased metabolic rate and need to deliver more O2 and eliminate more CO2

Question 6

What happens to barometric pressure at high altitude?

Answer 6

Decreased barometric pressure results in decreased PIO2

Question 7

What is hyperventilation and its stimulus at high altitude?

Answer 7

Increased ventilation due to hypoxaemia (reduced PaO2)

Question 8

What are the initial changes during acclimatization at high altitude?

Answer 8

• Hyperventilation
• Respiratory alkalosis
• Increased 2,3 DPG in red cells

Question 9

What is the net effect of increased 2,3 DPG on the O2-Hb dissociation curve?

Answer 9

Small increase in the P50

Question 10

What physiological changes occur during pregnancy?

Answer 10

• Increased minute ventilation
• Increased tidal volume
• Slight increase in respiratory rate
• Reduced FRC

Question 11

What is the effect of ageing on diffusing capacity?

Answer 11

Decreased due to loss of alveolar surface area and reduced pulmonary blood flow

Question 12

What is hypoxic hypoxia?

Answer 12

A reduction in PaO2

Question 13

What causes ventilatory failure?

Answer 13

• Mechanical defects in the chest wall
• Muscle disorders
• Airway obstruction

Question 14

What is a physiological shunt?

Answer 14

Blood that enters the arterial system without going through ventilated areas of the lung

Question 15

What is the consequence of nitrogen narcosis during deep diving?

Answer 15

Disruption of the function of ion channels, similar to ethanol effects

Question 16

What is decompression sickness?

Answer 16

N2 ‘boils’ out of tissue causing air bubbles that can block blood vessels

Question 17

What happens to gas volume during increased barometric pressure in diving?

Answer 17

Volume of gas decreases

Question 18

What is the definition of hypocapnoea?

Answer 18

Reduced CO2 in the blood

Question 19

What is hypercapnoea?

Answer 19

Increased CO2 in the blood

Question 20

What is dyspnoea?

Answer 20

Difficulty in breathing

Question 21

What is the physiological response to hypoxia?

Answer 21

Increased ventilation and pulmonary vasoconstriction

Question 22

What is the role of chemoreceptors during shunting?

Answer 22

Increase ventilation to normalize arterial PCO2

Question 23

What is the impact of ageing on respiratory muscle strength?

Answer 23

Diminished respiratory muscle strength

Question 24

Fill in the blank: The FRC and RV are increased, while the VC is _______.

Answer 24

decreased

Question 25

What is the effect of pulmonary embolism on V/Q ratio?

Answer 25

Increased V/Q ratio

Question 26

True or False: In hypoxic hypoxia, PaO2 is normal.

Answer 26

False

Question 27

What is the main cause of hypoxic hypoxia in clinical practice?

Answer 27

Ventilation perfusion imbalance

Question 28

What happens during respiratory alkalosis?

Answer 28

Increased pH due to decreased CO2

Question 29

What is the effect of increased renal excretion of bicarbonate during acclimatization?

Answer 29

Increased ventilatory response to hypoxia

Question 30

What is the primary adjustment during deep diving?

Answer 30

Increased partial pressures of gases

Question 31

What is a shunt in respiratory physiology?

Answer 31

A shunt allows blood to pass to systemic circulation without being oxygenated.

Question 32

What effect does a shunt usually have on arterial PCO2?

Answer 32

A shunt usually does not result in a raised PCO2 in arterial blood.

Question 33

How do chemoreceptors respond to elevated arterial PCO2?

Answer 33

They respond by increasing ventilation, which reduces the PCO2 of un-shunted blood.

Question 34

What is hypoxaemia?

Answer 34

Hypoxaemia refers to reduced PaO2 in the arterial blood.

Question 35

List compensatory mechanisms to increase O2 delivery during hypoxaemia.

Answer 35

* Increased ventilation (VA) by increasing respiratory rate and tidal volume * Increased cardiac output by increasing heart rate * Increased number of RBC (polycythaemia) * Cellular changes (increased 2,3 DPG)

Question 36

What is cyanosis?

Answer 36

Cyanosis is a dusky, dark bluish discoloration of tissues due to high concentrations of reduced (deoxygenated) hemoglobin.

Question 37

What is the minimum concentration of reduced hemoglobin in capillary blood that can lead to cyanosis?

Answer 37

More than 5 g/dL.

Question 38

What factors affect the occurrence of cyanosis?

Answer 38

* Total amount of hemoglobin in blood * Degree of unsaturation of hemoglobin * State of capillary circulation

Question 39

Where is cyanosis easily seen?

Answer 39

* Nail beds * Mucous membranes * Ear lobes * Lips * Fingers (thin skin)

Question 40

What causes peripheral cyanosis?

Answer 40

Impaired local circulation.

Question 41

What causes central cyanosis?

Answer 41

Hypoxaemia.

Question 42

Is cyanosis seen in CO poisoning?

Answer 42

No.

Question 43

What is the difference in cyanosis visibility in dark-skinned individuals?

Answer 43

Cyanosis is difficult to see in dark-skinned people.

Question 44

What is the impact of polycythaemia on cyanosis?

Answer 44

Cyanosis is more prominent in polycythaemia.

Question 45

What is the definition of hypoxic hypoxia?

Answer 45

Hypoxic hypoxia is due to lung failure, shunt, or pump failure.

Question 46

What is anemic hypoxia?

Answer 46

Anemic hypoxia is due to low hemoglobin content in blood.

Question 47

What happens to arterial PO2 in anemic hypoxia?

Answer 47

Arterial PO2 should be normal.

Question 48

What is the effect of CO poisoning on hemoglobin?

Answer 48

It forms COHb, which cannot take up O2.

Question 49

What is stagnant (ischaemic) hypoxia?

Answer 49

Hypoxia due to impaired circulation.

Question 50

What is histotoxic hypoxia?

Answer 50

Hypoxia due to the inability of cells to utilize O2, such as in CN- poisoning.

Question 51

What characterizes acidosis?

Answer 51

Increased acids in blood (H+) or a reduction in bases.

Question 52

What characterizes alkalosis?

Answer 52

Increased bases in blood (HCO3-) or a reduction in acids.

Question 53

What is the role of the respiratory system in acid-base balance?

Answer 53

Controls ECF CO2 concentration and pH.

Question 54

What happens to ventilation during increased H+ concentration?

Answer 54

Alveolar ventilation increases.

Question 55

What are the clinical features of hypoxia?

Answer 55

* Dyspnoea * Tachypnoea * Cyanosis * Cerebral hypoxia (impaired judgment, drowsiness, restlessness) * Headache * Vomiting * Tachycardia

Question 56

What is hypercapnoea?

Answer 56

Retention of excessive amounts of CO2.

Question 57

What is hypocapnoea?

Answer 57

Elimination of large amounts of CO2.

Question 58

What defines respiratory failure?

Answer 58

Failure to maintain normal arterial blood gas partial pressures, with hypoxia as an essential feature.

Question 59

What is the management approach for hypoxic hypoxia?

Answer 59

Oxygen therapy is valuable except in R to L shunts.

Question 60

What are the types of respiratory failure?

Answer 60

* Type I: hypoxia + normal or low PCO2 * Type II: hypoxia + hypercapnoea

Question 61

What is an example of a situation where respiratory adjustments are needed?

Answer 61

During exercise, high altitude, or pregnancy.

Question 62

What is the definition of dyspnoea?

Answer 62

Sensation of difficulty in breathing.

Question 63

What is the definition of apnoea?

Answer 63

Absence of breathing.

Question 64

What happens to compliance of lungs in a prematurely born infant with surfactant deficiency?

Answer 64

Compliance of lungs is reduced.

Question 65

What happens to arterial oxygen saturation in a patient with severe acute asthma?

Answer 65

Arterial oxygen saturation is likely to be reduced.