Pulmonary Function Testing Flashcards
What are the categories of PFTs?
- Airway function
- Spirometry - Lung volumes and ventilation
- FRC
- TLC
- RV - Diffusion capacity
- DLCO (diffusion capacity for carbon monoxide)
- KCO (transfer coefficient for carbon monoxide) - Blood gasses and gas exchange:
- Shunt studies - Cardiopulmonary exercise tests
What is a spirometer?
An apparatus for measuring the volume of air inspired and expired by the lungs
What are the clinical indications for spirometry?
- Diagnose the presence or absence of lung disease
- Quantify extent of known disease on lung function
- measure effects of occupational or environmental exposure
- Determine beneficial or negative effects of therapy (bronchodilators, steroids, lung transplant, beta-blockers)
What are some contraindications of spirometry?
Cardiopulmonary problems: pneumothorax, MI, haemoptysis, recent PE
Surgery: abdo, thoracic, brain, eye
Things that might pop lol: HTN, AAA
Stress incontinence
What is the normal range for spirometry?
80-120% of the predicted
Reference values depend on age, sex, race and ethnicity
What are the two types of spirometry?
Volume-time
Flow-volume
What are the 4 important spirometry parameters?
- FEV1: volume expired in first second of forced expiration after maximal inspiration
- FVC: max volume of air which can be expired with maximal force (after max insp)
- FEV1/FVC:
- gives an index of airflow limitation - PEF: Peak expiratory flow rate
What needs to happen to get good spirometry results?
- Proper use of spirometer: good mouth seal, nose plugs
- No hesitant start (underestimates FEV1)```
- Satisfactory exhalation
- No artefacts e.g. cough
- 2 largest FVC volumes must be within 150mL
- 2 largest FEV1 must be within 150mL
- Need three consistent flow-volume curves
What is the bronchodilator response?
- Done in the setting of airflow obstruction
- SABA ceased 4 hours before testing, LABA for 12 hours. No smoking for 1hr prior.
Spirometry –> 4 puffs salbutamol and wait 15 mins –> spirometry
200ml and 12% in FEV1 or FVC = significant bronchodilator response
How can you identify airflow obstruction with spirometry?
Reduced FEV1/FVC
What are the spirometry steps for obstructive airway disease?
- Is there evidence of airflow obstruction? Reduced FEV1/FVC
- How severe is the obstruction? Use FEV1
- Is there a significant bronchodilator response? (12% increase in FEV1)
- What do the flow-volume loops show
What suggests restrictive airway disease on spirometry?
Normal or high FEV1/FVC and reduced FEV1 and FVC BUT you can’t define it by spirometry alone.
You need to have reduced lung volumes (TLC)
What are the indications for lung volume determination?
- Diagnose or assess severity of restrictive lung disease
- Differentiate between obstructive and restrictive disease patterns
- Assess response to therapeutic interventions
- Make preoperative assessments of patients with compromised lung function
- Determine extent of hyperinflation and/or gas trapping
What are the three methods of determining lung volumes?
- Helium dilution
- Nitrogen washout
- Body plethysmography
What is diffusion capacity for carbon monoxide (DLCO)?
Measures the ability of gases to diffuse across the alveolar-capillary barrier. Diseases in which the uptake of O2 is reduced also cause a decrease in the uptake of CO
What is the overview pathway of PFT interpretation?
