COPD Flashcards
what do inhaled irritants stimulate
in epithelial cells (in chronic bronchitis) and alveolar macrophages (in emphysema) to release inflammatory mediators that damage airways and alveoli. inflammatory products disseminate around the body, where, along with the others effects of the disease and its treatment, they predispose to commorbidities liked to inflammation such as bronchiectasis
what is chronic bronchitis
it is characterised by exces smcuus secretions due to an increase in the size and number of goblet cells- contributes to airflow obstruction, risk of exacerbation, a 50% risk of bronchiectasis, and a productive cough in morning and throughout day (AKA smokers cough). it may present without airflow obstruction to begin with, but repeated irritation of the airways leads to inflammation, fibrotic changes and bronchospasm
what is emphysema
repeated injury from cigarette smoke causes proteolytic degradation of the alveolar walls and destruction of elastic fibres. In the alveoli, erosion of the alveolar septa leading to enlargement of airway and sometimes breaking down in bullae. in distal airways, bronchioles are destabilised by loss of elastic recoil which usually splints them open, these then collapse trapping air
what are bullae
air filled spaces within walls of attenuated emphysematous lung tissue
when does hyperinflation occur
it occurs when FEV1 has declined to roughly half normal, it is caused by gas trapping
what causes hyperinflation
loss of elastic fibres reduces inward lung elastic recoil, which loses the fight to balance outward chest wall recoil, leading to static hyperinflation. active inspiratory muscle contraction to hold open the floppy airway, even during exhalation, leading to dynamic hyperinflation
what causes hyperinflation
loss of elastic fibres reduces inward lung elastic recoil, which loses the fight to balance outward chest wall recoil, leading to static hyperinflation. active inspiratory muscle contraction to hold open the floppy airway, even during exhalation, leading to dynamic hyperinflation
when is hyperinflation worse
worsens with exercise because the rapid RR makes it difficult for the lungs to empty, creating dyspnoea. hyperinflation impairs the function of the now-shortened inspiratory muscles, which are already struggling with inflammation and sometimes malnutrition.
how does hyperinflation effect mechanics of breathing
the flattened diaphragm inactive the bucket handle action of the ribs and works paradoxically by pulling the lower ribs on inspiration (hoovers sign), thus becoming expiratory in action. dynamic hyperinflation prevents full expiration before the beginning of inspiration= traping more gas and leads to positive pressure in chest know as intrinsic PEEP= inspiratory muscles having to overcome greater pressure
how is WOB effected by active expiration
it is increased by active exhalation if the air needs to be forced out through obstructed airways, contributing to fatigue of the abdominal muscles on exercise
