RP - Spirometry Practical Flashcards
What is FEV₁, FVC, and PEF?
FEV₁:
- Forced Expiratory Volume in the 1st second of expiration
- volume of air that can be ejected in the first second of the forced expiratory manoeuvre
FVC:
- Forced Vital Capacity
- volume of air subject can eject from full lungs during a maximal expiration after full inspiration
PEF:
- Peak Expiratory Flow
- Maximum flow rate achieved during the forced exhalation
How do you differentiate between obstructive and restrictive diseases from the results of a spirometry ?
Obstructive:
- FEV₁/FVC ratio: <70%
- increased resistance to air flow
- slower to exhale fully
- e.g, asthma, COPD
- FEV₁ is reduced, FVC: Normal or reduced
Restrictive:
- FEV₁/FVC ratio: >70%
- FEV₁ and FVC both reduced
- less compliant lungs which don’t inflate as easily
- e.g, fibrosis or scoliosis
- Reduced lung compliance or chest wall restriction leading to decreased lung volumes
How would you simulate obstruction and restriction?
Obstruction:
- decreased airway diameter
- e.g. in asthma makes it harder to move air into and out of the lungs
- ↓ FEV1/FVC
Restriction:
- Reduced lung volume
- e.g. fibrosis (replacement of elastic fibres with collagen) reduces the ability to inflate the lungs with ease
- attach bands at full expiration as tight as possible before performing forced expiratory manoeuvre
Describe the factors affecting spirometry results:
Age - lung function declines with age
Height - taller individuals typically have larger lung volumes
Gender - males generally have higher lung volumes than females
Ethnicity - differences in thoracic dimensions can influence predicted values
How do you perform the forced expiratory manoeuvre ?
Preparation:
- ensure is patient is seated with nose clip attached
- instruct the patient to take a deep breath in, filling the lungs completely
Performance - the patient should then exhale as forcefully and rapidly as possible into the spirometer until no more air can be expelled
Repeat:
- procedure should be repeated 3 times to ensure reproducibility
- The best values are selected based on consistency and effort
