Pulmonary Blood Flow, Gas Exchange And Transport Flashcards
Describe bronchial circulation
Supplied via the bronchial arteries
Arises from systemic circulation to supply oxygenated blood to airway smooth muscle, nerves and lung tissue
Describe pulmonary circulation
Consists of L & R pulmonary arteries originating from the right ventricle.
Supplies the dense capillary network surrounding the alveoli and returns oxygenated blood to the left atrium via the pulmonary vein
Describe pulmonary circulation system in terms of flow and pressure
High flow
Low pressure
What is PaO2 the abbreviation for?
Partial pressure of oxygen in arterial blood
What is PACO2 the abbreviation of?
Partial pressure of carbon dioxide in alveolar air
State the partial pressure gradient for O2
PO2 = 100 mmHg in alveoli, moves down pp gradient to PO2 = 40 mmHg in arterial blood
State the partial pressure gradient for CO2
PCO2 = 46 mmHg in arterial blood and moves down pp gradient to PCO2 = 40 mmHg in the alveoli
State the proportions of the rate of diffusion across the membrane
- directly proportional to the partial pressure gradient
- Directly proportional to gas solubility
- Directly proportional to the available surface area
- inversely proportional to the thickness of the membrane
- most rapid over short distances
What is emphysema?
Destruction of the alveoli which reduces surface area for gas exchange
State the alveolar and arterial PO2 in emphysema
PAO2 - normal or low
PaO2 - low
Describe fibrotic lung disease
Thickened alveolar membrane which slows gas exchange. Loss of lung compliance which may decrease ventilation
State the alveolar and arterial PO2 in fibrotic lung disease
PAO2 - normal or low
PaO2 - low
Describe pulmonary oedema
Fluid in interstitial space increases diffusion distance
State the alveolar and arterial PO2 in pulmonary oedema, and the effect of diffusion distance
PAO2 - normal
PaO2 - low
Diffusion distance - increased
Describe asthma
Increased airway resistance, decreases airway ventilation
State the alveolar and arterial PO2 in asthma
PAO2 - low
PaO2 - low
Define ventilation
Air getting to the alveoli L/min
Define perfusion
Local blood flow L/min
Describe the optimal relationship between ventilation and perfusion
Ventilation = blood flow
Describe the factors that influence the distribution of blood flow in the lung
Hydrostatic (blood pressure)
Alveolar pressure
Describe blood flow in the base of the lung
Blood flow is high because arterial pressure exceeds alveolar pressure and vascular resistance is therefore low
Describe blood flow at the apex of the lung
Blood flow is low because arterial pressure is less than alveolar pressure, compressing the Arteriolar and vascular resistance is increased
Describe how the ratio of ventialtion to perfusion can be changed
When in the upright position, the V/Q ration changes front he base to the apex due to gravity
State the ratio of perfectly matched V/Q
Ventilation: perfusion = 1.0
State the ratio in mismatch 1 V/Q
Ventilation > perfusion ratio > 1.0
State the ratio in mismatch 2 V/Q
Ventilation < perfusion < 1.0
Where does the majority of mismatch take place?
In the apex
Define shunt
Opposite to alveolar dead space
Passage of blood through areas of the lung that are poorly ventilated
Alveoli are ventilated but not perfused
Describe the control mechanisms stimulated when ‘shunt’ occurs
Tissue PO2 is decreased around underventilated alveoli which constricts their arterioles, diverting blood to better-ventilated alveoli
Describe alveolar dead space
Opposite to shunt
Alveoli that are ventilated but not perfused
Define anatomical dead space
Air in the conducting zone of the respiratory tract which is unable to participate in gas exchange as walls are too thick
Define physiological dead space
Alveolar dead space + anatomical dead space
