Pulmonary Circulation Flashcards
2 blood supplies to the lungs
the bronchial and the pulmonary circulations
bronchial circulation is part of what circulation and where does it arise from?
The bronchial circulation is part of the systemic circulation
– arises from the aorta
where does the bronchial vascular bed supply oxygen to?
The bronchial vascular bed supplies oxygen and nutrients to the
smooth muscle and interstitial tissues of the lung
where does blood supplied in the smooth muscle and interstitial tissue of the lungs go to afterwards
It drains into pulmonary veins and returns back to the left ventricle
because it drains into pulmonary veins and returns back to the left ventricle what does that mean for venous return and gas exchange
– so pulmonary venous return is slightly greater than cardiac output
– it is also why gas exchange will never be perfect
what does pulmonary circulation distribute and where
The pulmonary circulation transports deoxygenated blood from right ventricle to the alveolar capillaries
– and returns oxygenated blood to the left atrium
pulmonary circulation receives what cardiac output and why
• Pulmonary circulation receives the whole of cardiac output as right
ventricular output must equal left
the pressure in the pulmonary circulation
low pressure system
right ventricular pressure
25/0 mmHg
Pulmonary artery pressure
25/10 mmHg
Pulmonary Pulse pressure
15 mmHg
Mean Pulmonary pressure
15 mmHg
• Pulmonary capillary pressure
~6 mmHg
Left atrial pressure (LAP)
~ 2 mmHg
how is systemic pressure measured
plethysmography
where is pulmonary capillary pressure measured
capillary wedge pressure
– is slightly higher than left atrial pressure
– used to estimate left atrial pressure
HOW is pulmonary capillary pressure measured
• Catheter put through right side into branch of pulmonary artery
– it wedges at the pulmonary capillaries and stops flow
what is resistance and pressure like during inhalation and why?
• As lung expands during inspiration, the extra-alveolar vessels are
pulled open
resistance is low, pressure is low
what is resistance and pressure like during expiration and why
lungs constrict during expiration, alveolar vessels smaller,
greater resistance and pressure
how are the shapes of the alveolar capillaries changed by blood pressure and air pressure and wht
distended by blood pressure
compressed by air pressure
due to its thin walls
why is there a difference between base and apex of lung
Given the height of the lung there is a difference in pressure between
the base and the apex
– it is ~30 cm in height, so this is ~22 mmHg of difference
– apex is -14 mmHg; base is +8 mmHg relative to cardiac leve
3 different zones of pulmonary blood flow
zone 1 - no flow
zone 2 - intermittent flow
zone 3 - continuous flow
zone 1 of pulmonary blood flow
capillary systolic pressure is less than alveolar leads to capillary collapse
– but only under abnormal conditions,
• e.g. very low pulmonary systolic pressure is there no flow at apex
PA > Pa > Pv
zone 2 of pulmonary blood flow
– capillary diastolic pressure less than alveolar
– in exercise, increased pulmonary arterial pressure means continuous flow in lung
Pa > PA > Pv
