Pulmonary Blood Flow (Chapter 6)

Vocabulary flashcards covering key concepts, terms, and mechanisms from the pulmonary blood flow chapter.

Pulmonary circulation

The portion of the circulatory system that carries blood from the right heart to the lungs and back to the left heart; low pressure and low resistance.

Systemic circulation

The circulation that supplies blood to all body tissues; higher pressure and resistance than the pulmonary circuit.

Pulmonary vascular resistance (PVR)

Resistance to blood flow through the pulmonary vasculature; (mean PAP − PCWP) / Qt; units mmHg·min/L or dyn·s·cm−5 (×80).

Pulmonary capillary wedge pressure (PCWP)

Indirect measure of left atrial pressure obtained by balloon wedging the distal end of a pulmonary artery catheter; reflects left atrial filling pressure.

Pulmonary artery pressure (PAP)

Pressure within the pulmonary arteries, reflecting the right heart’s afterload.

Right atrial pressure (RAP) / Central venous pressure (CVP)

measured via the proximal port of a PAC; approximates right-sided filling pressure.

Left atrial pressure

PCWP is an estimate of LAP.

West Zone I

Zone where alveolar pressure exceeds arterial pressure: PA > Pa > Pv; associated with alveolar dead space.

West Zone II

Zone where arterial pressure exceeds alveolar pressure but alveolar pressure exceeds venous pressure: Pa > PA > Pv; intermittent flow.

West Zone III

Zone where arterial pressure exceeds venous pressure: Pa > Pv > PA; continuous flow.

Hypoxic pulmonary vasoconstriction (HPV)

Contraction of pulmonary arterioles in hypoxic regions to redirect blood flow; increases PVR and RV afterload but reduces shunt.

Endothelium-derived relaxing factor (EDRF) / Nitric oxide (NO)

Endothelial vasodilator (NO) that increases cGMP and relaxes vascular smooth muscle; key local regulator of pulmonary vessels.

Nitric oxide (NO)

Gaseous vasodilator used therapeutically (inhaled) for pulmonary hypertension; rapidly inactivated by red blood cells.

Prostacyclin (PGI2)

Endothelium-derived vasodilator; used to dilate pulmonary vessels and treat pulmonary hypertension.

Sildenafil (Viagra)

PDE-5 inhibitor that increases cGMP, promoting pulmonary vasodilation.

Inhaled vasodilators

Vasodilators delivered by inhalation (e.g., NO, PGI2, sildenafil) that preferentially dilate pulmonary vessels with limited systemic effects.

Bronchial circulation

Systemic (bronchial) arteries supplying the tracheobronchial tree; accounts for about 1–2% of cardiac output and creates an anatomical shunt.

Pulmonary edema

Fluid accumulation in the alveolar spaces; caused by increased hydrostatic pressure, increased capillary permeability, decreased plasma oncotic pressure, or lymphatic failure.

Hydrostatic pressure in pulmonary capillaries

~7 mmHg; net filtration pressure ~ 1 mmHg outward.

interstitial hydrostatic pressure

~ 8 mmHg

Capillary oncotic pressure

~28 mmHg

interstitial Oncotic pressure

~14 mmHg; governs fluid movement across the capillary wall.

Net filtration pressure

driving fluid out of capillaries across the alveolar-capillary membrane; in normal lungs ≈ 1 mmHg outward.

Pulmonary edema mechanisms

Causes include increased hydrostatic pressure (e.g., LV failure), increased capillary permeability (ARDS), decreased plasma oncotic pressure, and lymphatic insufficiency.

Pulmonary artery catheterization (PAC / Swan-Ganz)

Invasive catheter (flow-directed, balloon-tipped) inserted via IJ or subclavian and advanced into the pulmonary artery to measure PAP, PCWP, and RAP.

PCWP measurement technique

Obtained with the balloon inflated from the distal port to occlude a pulmonary artery branch, approximating left atrial pressure.

LAP

Pressure within the left atrium; estimated by PCWP.

Left ventricular end-diastolic pressure (LVEDP)

filling pressure at end-diastole; an index of LV preload and filling status.

PVR and PAP relationship

An increase in PVR tends to raise PAP more than PCWP, increasing right ventricular afterload.

Exercise and PVR

During exercise, the pulmonary vasculature recruits and distends, allowing greater blood flow with only a modest rise in PAP.

Scintigraphy (V/Q scan)

Imaging technique to visualize ventilation and perfusion distribution in the lungs; used to identify mismatches such as emboli.