Obstructive lung disease

Question 1

what is an obstructive disease

Answer 1

narrowing of airway (increased resistance)
reduced inflow of gas
reduced inflation of alveolus

Question 2

what are the main types of obstructive diseases

Answer 2

asthma
chronic obstructive pulmonary disorder
cystic fibrosis
bronchiectasis

Question 3

what are the factors affecting airway internal diameter

Answer 3

increased mucus production
anatomical features
autonomic and non-adrenergic/non-cholinergic (NANC) systems
inflammation

Question 4

action of mucus

Answer 4

sweeps along the airway, traps irritants and removes them from the lungs via coughing

Question 5

describe airways

Answer 5

not rigid tubes
larger airways - contain cartilage and are relatively rigid
small airways - no cartilage, susceptible to collapse

Question 6

how does bronchoconstriction occur

Answer 6

happens quickly in response to agonists muscarinic receptors (m3)
this is caused by the parasympathetic nerve (vagus)
substance p and neutrokinins also cause bronchoconstriction

Question 7

how does bronchodilation occur

Answer 7

beta-2 adrenergic receptors
vasoactive intestinal peptide (VIP)

Question 8

how can asthma be characterised

Answer 8

reversible airways obstruction and an early and late phase response to stimuli
smooth muscle thickening, bronchoconstriction, basement membrane thickening, mucus plugging

Question 9

pathology of COPD

Answer 9

increased mucus production
destruction of alveoli and connective tissue leading to collapse of conducting airways

Question 10

pathology of cystic fibrosis

Answer 10

mucus secretions are thick and sticky, causing mucus plugging

Question 11

how do we measure obstruction

Answer 11

peak flow
spirometry
lung volumes and flow

Question 12

what are the factors determining airway resistance and flow

Answer 12

airflow = upstream pressure-downstream pressure / resistance
small changes in airways create a big impact on flow (small decrease in radius causes a big increase in resistance)

Question 13

describe peak flow

Answer 13

peak expiratory flow rate
measures maximum speed of expiration
crude measurement of conducting airflow
can aid in asthma diagnosis/management
good bedside and patient based too

Question 14

what is airflow

Answer 14

volume of gas per unit time

Question 15

how can we measure airflow

Answer 15

how much the patient can exhale in a given time - usually 1 sec, which is FEV1 (forced expiratory volume)
how much they can exhale all together - FVC (forced vital capacity)

Question 16

spirometry

Answer 16

FEV1 and FVC compared against predicted values based in height, age and sex, these values are based on a population of healthy individuals
can also be used as a diagnostic test in asthma

Question 17

what is the ratio of FEV1 to FVC used for?

Answer 17

differentiates between obstruction and restriction
if it is less than 0.7 it suggests obstructive airways pathology
in mild obstruction there is the biggest impact on FEV1
in severe obstruction there is also a loss of FVC

Question 18

what are the subdivisions of lung volumes

Answer 18

tidal volume - volume between resting inspiration and expiration
residual volume - volume left in lungs after maximum expiration has occurred
total lung capacity - total volume in lungs after maximum inspiration
vital capacity - volume between maximum inspiration and expiration
inspiratory reserve volume - difference between resting inspiration and maximum inspiration
expiratory reserve volume - difference between resting expiration and maximum expiration
functional residual capacity - volume remaining in lungs after resting expiration