Respiratory failure: causes and complications

Question 1

What can cause hypoxaemia and tissue hypoxia

Answer 1

Insufficient ventilation
Insufficient rate of gas exchange
Insufficient oxygen carrying capacity
Insufficient oxygen in atmosphere

Question 2

Type 1 vs Type 2 respiratory failure

Answer 2

Type 1 - Decreased oxygenation, decreased PaO2

Type 2 - Decreased ventilation, decreased PAO2, PaO2, increased PaCO2, and decreased pH

Question 3

A vs a

Answer 3

A = Alveolar
a = arterial

Question 4

How to calculate PAO2

Answer 4

PAO2 = F1O2 x (PB - PH2O) - PaCO2 / RER

where
F1O2 = Fraction of oxygen present in inspired gas
PB = barometric pressure
PH2O = H2O vapour pressure
PaCO2 = Arterial CO2 pressure
RER = Respiratory exchange ratio

Question 5

What is the respiratory exchange ratio

Answer 5

The relationship between CO2 elimination and oxygen consumption

RER = VCO2 produced / VO2 consumed.

Question 6

Example of oxidation of carbohydrates

Answer 6

C6H12O6 + 6O2 -> 6CO2 + 6H2O

6 / 6 = 1

Question 7

How to determine alveolar oxygen content

Answer 7

Alveolar oxygen content = Oxygen inspired - Oxygen consumed

PAO2 = (previous flashcard)

Question 8

What is the A-a oxygen gradient

Answer 8

Difference between alveolar and arterial pressure: PAO2 - PaO2.

Question 9

What does each variable in the alveolar gas equation and alveolar-arterial oxygen gradient represent

Answer 9

F1O2 = 0.21
PB = 100 kPa at sea level
PH2O = 6 kPa if at sea level
PaCO2 = Measured in patient
RER = assume 0.8 unless indicated otherwise
PAO2 = Calculated in formula

Question 10

Clinical signs/symptoms of respiratory disease

Answer 10

Shortness of breath, tachypnoea, dyspnoea
Laboured breathing, audible lung sounds
Tiredness, drowsiness, loss of consciousness
Fatigue
Cyanosis

Question 11

Causes of hypoventilation due to physical obstruction

Answer 11

Asphyxia, choking
Obstructive sleep apnoea
Bronchial obstruction (e.g. asthma)
Oedema, contraction of smooth muscle, excess mucus secretion

Question 12

Hypoventilation even when the airway is clear is caused by

Answer 12

Drug overdose
Neuromuscular disease (motor neuron disease, dystrophy)
Stroke/trauma
Issue with lung mechanics (COPD, pulmonary fibrosis)

Question 13

What is the dead space effect

Answer 13

Reduced perfusion of lung regions causing an increase in V/Q ratio

Question 14

What is the shunt effect

Answer 14

Reduced ventilation or limited diffusion causing a decrease in V/Q ratio

Question 15

Effects of insufficient O2 supply as a result of acute hypoxaemia nad hypercapnia

Answer 15

Dyspnoea, cyanosis, fatigue, coma, seizure
Tissue hypoxia, organ failure, death
Polycythaemia, hypoxic pulmonary vasoconstriction -> Pulmonary heart failure

Question 16

Effects of insufficient CO2 removal

Answer 16

Dypsnoea, confusion, seizure, unconsciousness
Hypercapnia -> Acidosis -> Organ failure + Cardiac arrhythmia -> death