Vascular physiology of the lung Flashcards
1
Q
The pulmonary & bronchial circulation
A
• Unique dual blood supply • Pulmonary Circulation – From Right Ventricle – 100% of blood flow – Bronchial Circulation – 2% of Left Ventricular Output
2
Q
Pulmonary circulation
A
- Receives 100% of cardiac output (4.5-8L/min.)
- Red cell transit time ≈5 seconds.
- 280 billion capillaries & 300 million alveoli.
- Surface area for gas exchange 50 – 100 m2
3
Q
Pressure across pulmonary circulation
A
Pressure across circuit = Cardiac Output x Resistance
Pressure across pulmonary circulation = mPAP – Left Atrial Pressure x Pulmonary Vascular Resistance
4
Q
mPAP - PAWP =
A
CO x PVR
5
Q
exercise
A
mPAP – PAWP = CO x PVR
CO = (mPAP – PAWP)/PVR
• On exercise mPAP remains stable in normal subjects but CO increases significantly
6
Q
respiratory failure
A
Type I Respiratory Failure pO2 < 8 kPA pCO2 <6 kPA Type II Respiratory Failure pO2 < 8 kPA pCO2 >6 kPA
7
Q
causes of Hypoxaemia
A
- Hypoventilation
- Diffusion Impairment
- Shunting
- V/Q mismatch
8
Q
Hypoventilation
A
• Type II Respiratory Failure – pO2 < 8 kPA – pCO2 >6 kPA • Failure to ventilate the alveoli • Muscular weakness • Obesity • Loss of respiratory drive
9
Q
shunt
A
• Physiological – Bronchial Arteries • Intracardiac – Eg VSD - R-L Shunt (Eisenmenger’s Syndrome) • Pulmonary – ArterioVenous Malformation (AVM) – Complete Lobar Collapse
10
Q
Eisenmenger’s Syndrome
A
- Cyanosis
- Clubbing
- Polycythaemia
11
Q
V/Q mismatch causes
A
- Physiological
- Pulmonary Emboli
- Asthma
- Pneumonia
- Pulmonary Oedema
12
Q
Hypoxic pulmonary vasoconstriction
A
• Poorly understood • Local action of hypoxia on pulmonary artery wall • Weak response as little muscle • Aims to improve V/Q matching – Local hypoxia (eg peanut) – Generalised hypoxia (eg altitude)
13
Q
Diseases of the pulmonary circulation
A
- Pulmonary Embolism
- Pulmonary Hypertension
- Pulmonary AVMs
