Pulmonary pressures at high flows in the intact pulsatile flow perfused lung

Area of Science:

• Physiology
• Cardiovascular Research
• Pulmonary Circulation

Background:

• Pulmonary pressure-flow (P-Q) curves are essential for assessing pulmonary vascular resistance and function.
• Previous methods for generating P-Q curves in intact animals were limited in pressure range, especially with pulsatile flow.

Purpose of the Study:

• To establish a reliable method for generating pulmonary pressure-flow curves in intact animals over a wider pressure range.
• To investigate the impact of unilateral pulmonary artery occlusion on the pulmonary pressure-flow relationship.

Main Methods:

• Systemic arteriovenous (a-v) fistulas and inferior vena cava (IVC) occlusion were used to manipulate blood flow and pressure.
• Pulmonary artery (PA) occlusion was employed to study the P-Q relationship in a single lung versus both lungs.
• Pressure-flow data were analyzed using linear regression.

Main Results:

• Pulmonary pressure-flow relationships were accurately described by linear equations for both one-lung and two-lung conditions (r2 ≈ 0.83).
• Unilateral PA occlusion significantly increased the slope of the P-Q relationship (from 3.6 to 5.9 mmHg·L⁻¹·s), indicating increased resistance in the remaining lung.
• No significant change was observed in the pressure axis intercept with PA occlusion, suggesting a consistent baseline pressure.

Conclusions:

• The pulmonary pressure-flow relationship in intact animals is linear above a mean pulmonary artery pressure of 10-12 mmHg.
• The described method provides a robust approach to studying pulmonary hemodynamics and the effects of interventions like PA occlusion.