pulmonary blood flow

How do pulmonary and systemic circulations differ?

Pulmonary = low pressure

What is the pulmonary capillary blood volume?

~75–100 mL spread over ~70 m² surface

What supplies oxygenated blood to lung tissue?

Bronchial arteries (systemic circulation)

How much of cardiac output is bronchial blood flow?

1–2% (creates small anatomical shunt)

Concept Q 6-1: Why does bronchial shunt lower arterial PO₂?

Because deoxygenated bronchial blood drains into pulmonary veins

How does pulmonary circulation compare in pressure and resistance to systemic?

Much lower pressure and resistance

What is a Swan-Ganz catheter used for?

To measure pulmonary artery pressures

What does PCWP reflect?

Left atrial pressure (LAP)

Concept Q 6-2: Why does mitral stenosis raise PCWP?

Because narrowing increases left atrial pressure

What is PVR?

Pulmonary vascular resistance = (mean PAP − PCWP) / cardiac output

Concept Q 6-3: Which rises with ↑ PVR

PAP or PCWP?

Concept Q 6-4: When does ↓ CO still cause ↑ PAP?

When blood dams up in pulmonary vessels due to LV failure

What passive factors affect PVR?

Increased PAP or LAP (recruit/dilate vessels)

What active factors affect PVR?

NO (vasodilator)

What is hypoxic pulmonary vasoconstriction (HPV)?

Response where pulmonary vessels constrict in low O₂ areas to redirect flow to better ventilated alveoli

What diseases reduce HPV response?

ARDS

Concept Q 6-5: Effect of NOS inhibitor?

Less NO → less vasodilation → more vasoconstriction → ↑ PVR

What inhaled vasodilators are used in ARDS?

Nitric oxide

Concept Q 6-6: Why does mucus plug look like PE on scan?

Both reduce perfusion to area; difference = mucus plug also reduces ventilation

What are West’s zones?

Zone I: PA > Pa > Pv (dead space)

What factors shift zones?

Positive pressure ventilation

Where is V/Q highest?

At apex (low flow

Where is V/Q lowest?

At base (much more blood flow → shunt-like)

What determines pulmonary edema?

Balance of hydrostatic pressure

What causes cardiogenic pulmonary edema?

Increased hydrostatic pressure (LV failure

What causes noncardiogenic pulmonary edema?

Increased capillary permeability (ARDS

What causes edema from low oncotic pressure?

Starvation

Concept Q 6-7: Patient with normal PCWP + proteins but edema?

Cause = ↑ permeability (noncardiogenic pulmonary edema

Which pressure reflects LVEDP?

Pulmonary capillary wedge pressure (PCWP ≈ LAP)

In which conditions is PAP increased?

Hypervolemia