Left ventricular dysfunction and extravascular fluid in the lung: physiological basis for symptoms.

Area of Science:

• Cardiology
• Respiratory Physiology
• Renal Physiology

Background:

• Left ventricular dysfunction increases left atrial pressure, causing pulmonary venous congestion.
• This congestion leads to fluid accumulation in the pulmonary microvasculature and airways.

Purpose of the Study:

• To investigate the role of airway rapidly adapting receptors (RAR) in response to left atrial pressure changes.
• To understand the mechanisms underlying symptoms and reflex diuresis in acute left ventricular dysfunction.

Main Methods:

• The study describes physiological responses to varying levels of increased left atrial pressure.
• It examines the activation patterns of RAR and C-fiber receptors in airways and alveoli.
• It discusses the mediation of reflex diuresis via neuronal nitric oxide synthase.

Main Results:

• Small acute increases in left atrial pressure (<10 mmHg) activate RAR, increasing respiratory rate, tracheal tone, and mucus secretion.
• Larger increases (~25 mmHg) activate both RAR and C-fiber receptors.
• Acute increases in airway fluid volume trigger a reflex diuresis.
• Chronic left atrial pressure elevation blunts RAR response to small fluid increments and abolishes reflex diuresis, though RAR remain sensitive to larger pressure increases.

Conclusions:

• Airway RAR are crucial for detecting changes in airway extravascular fluid volume.
• RAR activation mediates reflexes contributing to symptoms of acute left ventricular dysfunction.
• The sensitivity of RAR and associated reflexes is altered in chronic left ventricular dysfunction.