Lung Physiology 5

Question 1

CO2 carried in 3 ways

Answer 1

Bound to Haemoglobin
Plasma dissolved
As carbonic acid

Question 2

Physiological causes of a high CO2

Answer 2

V’A reduced: reduce minute ventilation

V’A reduced: increase dead space ventilation by rapid shallow breathing

V’A reduced: increase dead space by ventilation/perfusion mismatching

Increased CO2 production

Question 3

Parabolic relationship between alveolar ventilation and arterial CO2

Answer 3

If you increase the ventilation, you reduce the CO2

If you reduce your ventilation Carbon dioxide moves really quickly

this is the thermostat control for acid base balance

Question 4

Causes of low hypoxemia

Answer 4

Alveolar hypoventilation

Reduced piO2

Ventilation/Perfusion mismatching (V/Q)

Diffusion abnormality

Question 5

Definition of respiratory failure

Answer 5

Failure of gas exchange (inability to maintain normal blood gases)

Low PaO2- with or without a rise in PaCO2

Respiratory failure can occur with normal or abnormal lungs

Question 6

Respiratory failure blood gases

Answer 6

PaO2 is < 8KPa and PaCO2 >6.5KPa

Question 7

Respiratory failure- basic types

Answer 7

Type I and Type II

Question 8

Type I

Answer 8

Low PaO2 (hypoxia) and Low/Normal PaCO2 (hypocapnia/normal)

Question 9

Type II

Answer 9

Low PaO2 (hypoxia) and High PaCO2 (hypercapnia)

Lack of respiratory drive
Excess workload
Bellows failure

Question 10

Respiratory failure; Time course

Answer 10

Acute, rapidly. Eg; opiate overdose, trauma, pulmonary embolism

Chronic, over a period of time. Eg; COPD, Fibrosing lung disease

Question 11

Most pulmonary and Cardiac causes produce type I failure- Hypoxia

Answer 11

Mismatching of ventilation and perfusion
Shunting
Diffusion impairment
Alveolar hypoventilation

Similar effects on tissues seen with: anaemia, carbon monoxide poisoning, methaemoglobinaemia

Question 12

Hypoxia clinal features- central cyanosis

Answer 12

Tongue appears blue because of sluggish peripheral circulation. This means theres an increase in the extraction of O2 from haemoglobin because the blood is taking longer to get through the preference, resulting in the presence of deoxygenated haemoglobin in the preference

Question 13

Other clinical features of hypoxia

Answer 13

Irritability, reduced intellectual function, reduced consciousness, convulsions, coma, death

Question 14

Hypocapnia: clinical features

Answer 14

Varies from patient to patient

Irritability, headache, Papilloedema, Warm skin, Bounding pulse, Confusion, Somnolence, Coma