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
Why would you do diffusion capacity/DLCO testing?
- Differentiate obstructive diseases
- Differentiate restrictive diseases
- Follow progress of parenchymal lung disease
How can you differentiate emphysema and asthma?
Decreased DLCO in emphysema
Increased DLCO in asthma
How can you differentiate different types of restrictive disease?
Decreased DLCO in interstitial lung disease
Normal DLCO in extraparenchymal restriction
What is the overview pathway of PFT interpretation?
What can happen to TLC and RV in obstructive lung disease?
Increased TLC- hyperinflation
Increased RV- gas trapping
What if the lung tests all come back normal besides having a reduced DLCO (diffusion capacity)?
Do an echocardiogram to evaluate for HF
Do a V/Q scan to check for perfusion problems
