lung physiology 2 (spirometry) Flashcards
define tidal volume
volume of air that enters and leaves with each breath, from a normal quiet inspiration to a normal quiet expiration
what is average tidal volume
0.5 L
what can cause tidal volume to change (2)
- it changes with pattern of breathing
- increases with pregnancy
define inspiratory reserve volume
extra volume that can be inspired above tidal volume, from normal quiet inspiration to maximum inspiration
average inspiratory reserve volume
2.5 L
what does inspiratory reserve volume rely on (3)
- muscle strength
- lung compliance (elastic recoil)
- a normal starting point (end of tidal volume)
define expiratory reserve volume
extra volume that can be expired below tidal volume, from normal quiet expiration to maximum expiration
average expiratory reserve volume
1.5 L
what does expiratory reserve volume rely on (2)
muscle strength
low airway resistance
what reduces expiratory reserve volume (3)
- in pregnancy
- obesity
- severe obstruction or proximal (of trachea/bronchi obstruction)
define residual volume/reserve volume
volume remaining after maximum expiration
average residual volume/reserve volume
1.5 L
can residual volume/reserve volume be measured by spirometry
no
what are capacities
composed of 2 or more lung volumes.
these are fixed as they do not change with the pattern of breathing
what can simple spirometry measure
- tidal volume
- inspiratory reserve volume
-expiratory reserve volume.
it cannot measure residual volume
which values are standardised in spirometry
height - has the greatest influence upon capacities
age
sex
describe process of spirometry
- the subject breathes from a closed circuit over water.
- the chamber is filled with oxygen and as they breathe, gas increases and reduces the volumes within the circuit.
- a weight above the chamber changes height with each ventilation according to the circuit volume.
- its height is recorded with a pen to reflect the volume inspired or expired over time.
what is a vitalograph
creates plots of volume against time, using data collected from spirometry tests.
what can you measure from a vitalograph (2)
FVC (forced vital capacity)
and
FEV1 (forced expiratory volume in one second)
what is FVC (forced vital capacity)
the maximal volume of air that a subject can expel in one maximal expiration from a point of maximal inspiration
FEV1 (forced expiratory volume in one second)
the maximal volume of air that a subject can expel in one second from a point of maximal inspiration
what is the FEV1/FVC ratio
The proportion of air that can be exhaled in the first second compared to the total volume of air that can be exhaled is important in assessing for possible airway obstruction.
what is the flow volume loop
plots flow over volume (showing expiratory flow and inspiratory flow as positive and negative values respectively).
what are important factors to consider when assessing flow-volume curves (3)
- Peak Expiratory Flow Rate (PEFR) – the rate of flow.
- Vital capacity – the volume expired, calculated from the X-axis.
- Shape of the curve – ‘spooning’ in obstructive disease, small overall loop in restrictive disease.
define spirometry
a method of assessing lung function by measuring the volume of air that the patient is able to expel from the lungs after a maximal inspiration
what are typical spirometry findings in obstructive lung disease
- reduced FEV1 (<80% of the predicted normal) - due to increased resistance during expiration
- reduced FVC (but to a lesser extent than FEV1)
- FEV1/FVC ratio reduced (<0.7)
examples of obstructive lung disorders
chronic obstructive pulmonary disease, asthma, cystic fibrosis
what are typical spirometry findings in restrictive lung disease
- reduced FEV1 (<80% of the predicted normal)
- reduced FVC (<80% of the predicted normal)
- FEV1/FVC ratio normal (>0.7)
example of restrictive lung disease
fibrotic lung disease, asbestosis, sarcoidosis
what are obstructive lung diseases
conditions that make it hard to exhale all the air in the lungs leading to shortness of breath
because of damage to the lungs or narrowing of the airways inside the lungs, exhaled air comes out more slowly than norma
what are restrictive lung diseases
people with restrictive lung disease cannot fully fill their lungs with air. their lungs are restricted from fully expanding
what is a peak flow test
a simple measurement of how quickly you can blow air out of your lungs. (exhale)
It’s often used to help diagnose and monitor asthma.
what does peak flow test show
can indicate whether your airways are narrowed
could be a sign that you have asthma, although other tests such as spirometry will often be needed to confirm the diagnosis
units for peak flow
litres/minute
