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
Pulmonary function changes with pulmonary oedema
Reduced lung compliance
Pulmonary vascular resistance and airway resistance increased due to airway / vascular wall oedema reducing lumen radius
Gas exchange changes with pulmonary oedema
Hypoxaemia due to shunt and ventilation perfusion mismatch
No CO2 retention
Triad of coagulopathy
Stasis
Increased coagulability of blood
Abnormality / Damage of vessel wall
Causes of blood stasis
Immobilisation
Venous obstruction
Dehydration
Causes of increased coagulability of blood
Sickle cell disease
Malignancy
Oral contraceptive pill
Polycythaemia
Causes of damage / abnormality of vessel wall
Trauma
Inflammation
How are pulmonary emboli cleared
Lytic components of blood
Gas exchange changes with pulmonary embolism
Hypoxaemia due to ventilation perfusion mismatch
Dead space is increased
Pulmonary function changes with PE
Surfactant depletion to embolised area as surfactant has rapid turnover
This can lead to atelectasis
Classification of pulmonary hypertension
Increased left atrial pressure
Increased pulmonary blood flow
Increased pulmonary vascular resistance
Primary pulmonary hypertension
Causes of increased pulmonary vascular resistance
Vasoconstriction eg with alveolar hypoxia
Obstructive eg PE
Obliterative eg emphysema
Primary pulmonary hypertension features
Uncommon and cause unknown
Often females between 20 and 40 years
Exertion causes SOB + syncope
Signs RV hypertrophy
Management of primary pulmonary hypertension
Vasodilators - can be catheter directed for local effect
Prognosis is poor
Cor pulmonale definition
Right heart disease secondary to lung disease
Pulmonary HTN caused by capillary bed obliteration or hypoxic vasoconstriction
