Lung Function Testing Flashcards
When is spirometry indicated for use?
- Diagnose or manage asthma
- Detect respiratory disease in patients presenting with symptoms of breathlessness, + distinguish respiratory from cardiac disease as the cause
- Measure bronchial responsiveness in patients suspected of having asthma
- Diagnose + differentiate between obstructive lung disease + restrictive lung disease
- Follow natural history of disease in respiratory conditions
- Assess of impairment from occupational asthma
- Conduct pre-operative risk assessment before anaesthesia or cardiothoracic surgery
- Measure response to treatment of conditions which spirometry detects (i.e.: bronchodilators)
- Diagnose the vocal cord dysfunction
What are contraindication of spirometry (when should it not be performed)?
Forced expiratory manoeuvres may aggravate some medical conditions.
- Haemoptysis of unknown origin
- Pneumothorax
- Unstable cardiovascular status (angina, recent myocardial infarction, etc.)
- Thoracic, abdominal, or cerebral aneurysms
- Cataracts or recent eye surgery
- Recent thoracic or abdominal surgery
- Nausea, vomiting, or acute illness
- Recent or current viral infection
- Undiagnosed hypertension
What is Spirometry?
A method of assessing lung function by measuring the volume of air that the patient can expel from the lungs after a maximal inspiration, & how fast they can expel it
What parameters are most commonly measured in spirometry?
- Vital capacity (VC)
- Forced vital capacity (FVC)
- Forced expiratory volume (FEV) – at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds
- Results usually given in both raw data (litres, litres per second) and percent predicted
Describe the procedure of Spirometry.
- Patient asked to take the deepest breath possible, and then exhale into the sensor as hard + long as possible
- During test: use a soft nose clip (prevent air escaping)
What are the limitations of Spirometry?
- Highly dependent on patient co-operation & effort (normally needed to repeat 3x for reproducibility)
- Only children old enough/ people able to comprehend & follow instructions (need patient co-operation)
- No unconscious/sedated patients
- Can’t always be used as a diagnostic tool, better at monitoring for sudden decrease in FEV1
(e.g.: asthma may be normal apart from during an attack)
What is considered a normal approx. value for male forced vital capacity (FVC)?
4.8 L
What is considered a normal approx. value for female forced vital capacity (FVC)?
3.7 L
What is considered a normal approx. value for male Tidal Volume (Vt)?
500 mL
What is considered a normal approx. value for female Tidal Volume (Vt)?
390 mL
What is considered a normal approx. value for male Total Lung Capacity (TLC)?
6.0 L
What is considered a normal approx. value for female Total Lung Capacity (TLC)?
4.7 L
Forced Expiratory Volume in 1 second (FEV1).
the volume of air that the patient is able to exhale in the 1st second of forced expiration, starting from full inspiration
Forced Vital Capacity (FVC) (& what is it measured in?).
- The total volume of air that the patient can forcibly exhale in 1 breath, after full inspiration
- Measured in litres
What is the FEV1/FVC ratio?
the ratio of FEV1 to FVC expressed as %
- FEV1 is 70%-80% of FVC in normal subjects (0.7-0.8)
- Excellent measure of airway limitation and allows differentiation obstructive from restrictive disease
- Standard diagnostic test for COPD
- Moderate airflow obstruction 0.5-0.6 (50-60%)
- Severe airflow obstruction 0.3 (30%)
- Restrictive disease 1.0
What happens to the FEV1/FVC ratio when the patient has a restrictive disease?
- Both FEV1 and FVC are reduced (in proportion)
- FEV1:FVC ratio is normal or increased (>80%)
What happens to the FEV1/FVC ratio when the patient has a obstructive disease?
- High intrathoracic pressures (generated by forced expiration) cause premature closure of the airways with trapping of air in the chest
- FEV1 is reduced
- FEV1:FVC ratio is reduced (<80%)
