Lung physiology 4

Question 1

respiratory failure

Answer 1

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
Acute, rapidly
For example, opiate overdose, trauma, pulmonary embolism
Chronic, over a period of time
For example, COPD, fibrosing lung disease

Question 2

PAO2 =

Answer 2

PiO2 - PaCO2/R

Question 3

Type 1 respiratory failure

Answer 3

• Most pulmonary and cardiac causes produce type 1 failure
• Hypoxia - Mismatching of ventilation and perfusion, shunt, diffusion impairment, alveolar hypoventilation
• Similar effects on tissues seen with: Anaemia, CO poisoning, methaemoglobinaemia

Question 4

Type 2 respiratory failure

Answer 4

low PaO2, High PaCO2
Mechanisms
(i)	Lack of respiratory drive 
(ii)	Excess workload 
(iii)	Bellows failure

Question 5

hypoxia clinical features

Answer 5

central Cyanosis 
irritability 
reduced intellectual function
reduced consciousness
convulsions 
coma 
death

Question 6

hypercapnia clinical features

Answer 6

variable patient to patient 
irritability 
headache 
papilloedema 
warm skin
bounding pulse 
confusion 
somnolence 
coma

Question 7

Type 1 respiratory failure; treatment

Answer 7

• Airway patency oxygen delivery
• Many differing systems
• Increasing FiO2
• Primary cause (e.g. antibiotics for pneumonia)

Question 8

Type 2 respiratory failure; treatment

Answer 8

• Airway patency oxygen delivery
• Primary cause (e.g. antibiotics for pneumonia)
• Treatment with O2 may be more difficult – for example; COPD patients rely on hypoxia to stimulate respiration
• Assisted ventilation – invasive/non-invasive, inadequate PaO2 despite increasing FiO2, increasing PaCO2, patient tiring