Pulmonary Circulation and Gas Exchange

These flashcards cover terms and definitions related to pulmonary circulation, blood flow, pressures, ventilation, and shunting mechanisms.

Pulmonary circulation

Carries deoxygenated blood from the right ventricle to the lungs for oxygenation.

Systemic circulation

Carries oxygenated blood from the left ventricle to the body.

Transmural pressure

Difference between pressure inside a vessel or airway and the pressure outside it.

Driving pressure

Pressure difference between two points in a system that moves gas or liquid.

Hypoxic Pulmonary Vasoconstriction (HPV)

Reflex vasoconstriction when alveolar O2 < 60-70 mmHg, redirecting blood to ventilated alveoli.

Intrapulmonary shunt

Blood passes lungs without gas exchange, leading to venous admixture.

Shunt types

Absolute (total) shunt has no gas exchange; relative shunt occurs when ventilation < perfusion.

Dead Space

Alveoli that are ventilated but underperfused.

Pulmonary Vascular Resistance (PVR)

Resistance to blood flow from the right ventricle through pulmonary circulation.

Anatomic shunt

Unoxygenated blood bypasses alveoli, normal in 2-3% of cardiac output.

Patent Ductus Arteriosus (PDA)

Fetal ductus arteriosus fails to close, causing a left-to-right shunt.

V/Q Ratio

Indicates airflow-blood flow balance, normally 0.8.

Zone 1

No perfusion as alveolar pressure > arterial/venous pressure.

Zone 2

Intermittent flow where arterial pressure > alveolar pressure > venous pressure.

Zone 3

Continuous perfusion with arterial/venous pressure > alveolar pressure.

Transrespiratory pressure

The difference between alveolar pressure and ambient pressure that drives airflow.

Transthoracic pressure

Difference between pleural pressure and body surface pressure, expanding lungs/chest wall.

Recruitment vs Distention

Recruitment is opening closed capillaries; distention is widening open capillaries.

Swan-Ganz Catheter

Measures pressures in right atrium, right ventricle, pulmonary artery, and pulmonary capillary wedge pressure.