BINGO WORDS - 8 pulmonary hemodynamics

Blood pressure (BP)

The force of blood pushing against vessel walls as it moves through the body.
Affected by CO, VR, pump strength, blood volume, and viscosity.

Mean arterial pressure (MAP)

The average pressure pushing blood through the circulation.
MAP = (2 × diastolic + systolic) / 3.
Indicator of tissue perfusion.

Cardiac output (CO)

The volume of blood the heart pumps per minute.
CO = HR × SV; normal 4–8 L/min.

Vascular resistance (VR)

The resistance blood encounters as it flows through vessels.
Used in BP formula: BP = CO × VR.
Includes SVR and PVR.

Systemic circulation

Higher-pressure circulation that delivers oxygen and nutrients to tissues.
Originates from left ventricle → body → returns to right atrium.

Pulmonary circulation

Low-pressure circulation focused on gas exchange.
Right ventricle → lungs → left atrium.

Systemic blood pressure

Includes ~120/80 mmHg pressures and decreases through arteries → capillaries → veins.

Pulmonary blood pressure

Much lower pressures (20–30/6–15 mmHg) than systemic to protect alveoli and support gas exchange.

Capillaries

Pulmonary vessels where gas exchange occurs; pulmonary capillary pressure is 4–12 mmHg.

Venules

Low-pressure vessels (~4–12 mmHg) that carry oxygenated blood from pulmonary capillaries to pulmonary veins.

Right atrium

The chamber that receives systemic venous blood at ~2–6 mmHg pressure.

Pulmonary vascular resistance (PVR)

Resistance posed by pulmonary vessels; normal <250 dyn·s·cm⁻⁵.
Affected by gravity, hydrostatic pressure, lung volumes, vascular pressures, hypoxia, hypercapnia, and NO.

Systemic vascular resistance (SVR)

Resistance posed by systemic vessels; normal 900–1400 dyn·s·cm⁻⁵.

Gravity

Causes blood to pool in the lowest parts of the lung:
Erect → bases
Supine → posterior
Lateral → dependent lung
Trendelenburg → apices

Hydrostatic pressure

Pressure exerted by the blood column; increases from apex → base.
Apex = lowest pressure; Base = highest pressure.

Lung zones (Zone 1, 2, 3)

Zone 1: PA > Pa > Pv — no flow; not present normally (appears in PPV or hemorrhage).
Zone 2: Pa > PA > Pv — pulsatile flow.
Zone 3: Pa > Pv > PA — continuous flow; at bases

Perfusion

Flow of blood through pulmonary capillaries for gas exchange.
Highest at lung bases.

Ventilation

Airflow into and out of alveoli; alveoli at bases expand more and receive more ventilation.

Alveolar vessels

Vessels in contact with alveoli; influenced by alveolar pressure; compressed at high lung volumes.

Extra-alveolar vessels

Vessels away from alveoli; influenced by intrapleural pressure; dilate at high lung volumes.

Lung volumes

Affect vessel diameter:
High volumes → alveolar vessels compress, extra-alveolar vessels dilate; total PVR lowest at FRC.

Recruitment

Opening of previously closed capillaries, increasing surface area for blood flow.
Occurs before distension.

Distension

Widening of already perfused capillaries to increase flow without raising pressure.

Hypoxia

Low alveolar oxygen (PAO₂ <70 mmHg) causes pulmonary vasoconstriction, increasing PVR.
(Opposite of systemic response.)

Hypercapnia

High CO₂ causes pulmonary vasoconstriction; less potent than hypoxia; related to ↓pH.

Nitric oxide (NO)

Potent vasodilator that selectively reduces PVR; used clinically in pulmonary hypertension.

Gas exchange

Pulmonary circulation's main role; low pressures support efficient O₂ and CO₂ diffusion.

Ventilation-perfusion (V/Q) matching

At the bases, both ventilation and perfusion are highest, optimizing gas exchange.