Pulmonary Pathophysiology - Vascular Disease Flashcards
Pulmonary oedema definition
Abnormal accumulation of fluid in extravascular spaces and tissues of the lung
Differences between capillary endothelium and alveolar epithelium
Capillary endothelium very permeable to fluid, ions and some proteins
Alveolar epithelium highly impermeable to fluid, ions and some proteins. Actively removes fluid from alveoli using Na+/K+ ATPase
Starling Equilibrium
Two forces acting for fluid movement:
- Hydrostatic pressures
- Colloid osmotic pressures
Most important protein for colloid osmotic pressures and why
Albumin as higher number of albumin protein particles than other proteins in blood (as it is a small protein)
Osmotic pressure determined by colligative properties - i.e concentration of protein is important rather than the protein identity
Two stages of pulmonary oedema
Interstitial oedema leads to increased blood gas barrier but no oedema in alveoli yet
As capillary pressure increases further, possibly alveolar epithelium becomes damaged and now fluid passes through epithelium
Pathogenesis of pulmonary oedema
Increased capillary hydrostatic pressure
Increased capillary permeability
Decreased interstitial hydrostatic pressure
Decreased colloid osmotic pressure
Lymphatic insufficiency
Uncertain aetiology
Causes of increased capillary hydrostatic pressure
MI
Hypertensive LV failure
Mitral stenosis
Transfusion Associated Circulatory Overload
Causes of increased capillary permeability
Inhaled / circulating toxins
Adult Respiratory Distress Syndrome
Radiation
Oxygen toxicity
Inhaled toxin that increases capillary permeability and therefore causes pulmonary oedema
Chlorine gas
Causes of decreased interstitial hydrostatic pressure
Rapid removal of pleural effusion or pneumothorax
Rapid re-expansion of collapsed lung
Hyperinflation of lung
Causes of decreased colloid osmotic pressure
Saline overtransfusion
Hypoproteinaemia
Causes of lymphatic insufficiency
Silicosis
Lymphangitis carcinomatosa
Lung transplantation
Uncertain aetiology causes of pulmonary oedema
High altitude pulmonary oedema
Opioid use
Neurogenic pulmonary oedema
Why does high altitude pulmonary oedema occur
Hypoxic pulmonary vasoconstriction increases pulmonary artery pressures
Uneven hypoxic vasoconstriction exposes some capillaries to high pressures resulting in capillary damage
Therefore pulmonary oedema occurs due to increased capillary pulmonary oedema
Cause for dyspnoea in pulmonary oedema
Likely stimulation of J receptors causing rapid shallow breathing
