Physiology and Obstruction Flashcards
(23 cards)
what is an obstructive disorder
narrowing of airway - increased resistance
reduced inflow of gas
reduced inflation of alveolus
obstructive lung diseases
asthma
copd
causing obstructive picture - bronchiectasis, cystic fibrosis
factors affecting airway internal diameter
increased mucus production
anatomical features
autonomic and non-adrenergic/non-cholinergic (NANC) systems
inflammation
features of larger airways
contain cartilage
relatively rigid
features of small airways
no cartilage
susceptible to collapse
what does bronchoconstriction happen quickly in response to
agonists
what receptors are responsible for bronchoconstriction
muscarinic receptors
what receptors are responsible for bronchodilation
beta 2 adrenergic receptors
what neurotransmitter goes from the vagus nerve to muscarinic receptors for bronchoconstriction
acetyl choline
what is asthma characterised by
reversible airways obstruction and an early and late phase response to stimuli
features of asthma
multiple reasons for airway narrowing
smooth muscle thickening
bronchoconstriction
BM thickening
mucous plugging
features of copd
increased mucous production
destruction of alveoli and connective tissue leading to collapse of conducting airways
how is obstruction measured
peak flow
spirometry
lung volumes and flow
factors determining airway resistance and flow
airflow
upstream pressure
downstream pressure
what does airflow equal
airflow = (upstream pressure - downstream pressure) / resistance
airflow = volume of gas per unit of time
what does a small decrease in radius lead to
big increase in resistance
therefore decrease in flow
peak flow
peak expiratory flow fate
measures maximum speed of expiration
crude measurement of conducting airway flow
can aid in asthma diagnosis/management
excellent bedside and patient based tool
FEV1
how much a patient can exhale in one second
FVC
how much can a patient exhale altogether
spirometry
forced expired volume in one second (FEV1)
forced vital capacity (FVC)
compared to predicted values based on age, sex and height
predicted values based on population of healthy individuals
global lung initiative (GLI) lung function predicition
set up in 2008 to standardise predicted valued for spirometry
now adopted as gold standard
online tool for data interpretation
ratio of FEV1 to FVC
useful to differentiate between obstruction and restriction
if less than 0.7 the suggest obstructive airways pathology
mild obstruction - biggest impact on FEV1
severe obstruction - also lose FVC
reversibility of spirometry
used as diagnostic test for asthma - e.g. following bronchodilator
asthma reversible vs copd fixed obstruction
can also use bronchial challenge agents (histamine) to induce bronchospasm and obstructive spirometry
