CVPR Week 5: Pulmonary function tests Flashcards
Spirometry measures?
lung function
- FVC
- FEV1
FVC AKA
Forced vital capacity
FVC definition
s defined as the amount of air that can be forcibly exhaled from the lungs after taking the deepest breath possible
FEV1 AKA
Forced expiratory volume in 1 second
FEV1 definition
FEV1 is the maximal amount of air you can forcefully exhale in one second
the test shows if there is airway obstruction
Lung volume tests measure?
Measures lung capacity
- TLC
- RV
TLC AKA
Total lung capacity
TLC definition
- about 6,000 mL
- is the maximum amount of air that can fill the lungs
- (TLC = TV + IRV + ERV + RV)
RV AKA
Residual volume
RV Definition
the volume of air still remaining in the lungs after the most forcible expiration possible
PFT AKA
Pulmonary function tests
PFT Values

In pulmonary, capacity is?
The sum of at least 2 volumes

What are PFTs used for?
- Diagnosis and treatment of lung disease
- Evaluate disease progression or improvement during treatment
- Pre-operative evaluation
- Clinical diagnosis of dyspnea
- Evaluate impairment
- Changes due to exposures or drugs (occupational exposures or drugs like amiodarone and chemotherapies)
Common drugs that cause pulmonary toxicity
- Chemotherapies
- amiodarone
Preoperative PFTs value and indications
4 listed
- somewhat useful for predicting the risk of postoperative complications
- Lung function alone should not be used to deny a patient non-pulmonary surgery
- In lung resection, used to predict a post-resection FEV1 of 0.8L
- Exercise testing may also be useful
Symptom diagnostics to help in the evaluation
5 listed
- Cough
- Dyspnea
- Wheezing
- Orthopnea
- Chest pain
Lab or imaging study diagnostics to help in the evaluation
4 listed
- Hypoxemia
- Hypercapnia
- Polycythemia
- Abnormal CXRs
Physical exam finding diagnostics to help in the evaluation
- signs of overinflation
- Wheezing
- Crackles
- Cyanosis
Spirometry values measured
Often measured before and after bronchodilators
- FEV1
- FVC
For most cases, what test values are needed to define lung disease is present and follow patients with obstructive disease
- FEV1
- FVC
How to perform spirometry
8 listed

The flow volume loop of spirometry

How is an obstructive defect determined from PFTs?
- FVC is the total amount of air exhaled from total lung capacity down to residual volume
- FEV1 is the amount of air exhaled in 1 second (most people should be able to exhale 70% of their VC in 1 second)
- Expressed as FEV1/FVC ratio
- This is a difficulty in getting air out rather than in
Air movement deficits in Obstructive lung diseases
Difficulty getting air “out”
Air movement deficits in Restrictive lung diseases
Difficulty getting air “in”
Ratio of what indicates airflow obstruction?
<70% of FEV1/FVC
FEV1/FVC of <100 and >70
mild
FEV1/FVC of <70 and >60
Moderate
FEV1/FVC of <60 and >50
Moderately severe
FEV1/FVC of <50 and >35
Severe
FEV1/FVC of <35
Very severe
Severity of airflow obstruction classifications

Common obstructive lung defects
- Asthma
- COPD/Chronic bronchitis
- Ephysema
- Bronchiectasis
Asthma level of obstruction
It may be variable obstruction improving post-bronchodilator
Asthma PFTs
- PFTs may be normal if patient’s asthma is under control
- Normal spirometry doesn’t rule out the disease for this reason
- Spirometry can help define the severity of the disease
- Bronchodilatory response - increase in FEV1 of 12% and greater than 0.2 L suggests response
- Lack of bronchodilator response does not rule out asthma or mean that bronchodilators are not useful
- Lung volumes are usually not needed
Asthma normal spirometry
spirometry may be normal if the patient’s asthma is under control and for this reason the disease cannot be ruled out by normal spirometry
Asthma bronchodilator response considerations
- increase in FEV1 of 12% and greater than 0.2 L suggests a response
- Lack of a bronchodilator response does not rule out asthma or mean that bronchodilators are not useful
Asthma lung volumes
Lung volumes are not usually needed
COPD PFTs
3 listed
- A decrease in FEV1 helps define the severity of the disease along with functional status and exacerbations for prognostication
- Lack of bronchodilator response does not mean that bronchodilators are of no use
- Lung volumes can show hyperinflation (elevated TLC) and air trapping (elevated RV)
Lung volumes measure
TLC and RV
Lung volume testing usefulness
not needed as a routine test but is useful in defining restrictive lung diseases
Increased TLC in obstruction
means hyperinflation and increased RV air trapping
Lung volume testing for defining restrictive diseases
3 listed
- Defined as a decrease in lung volume
- decreased TLC below the lower limit of normal
- FVC and FEV1 are both reduced but the ratio is normal meaning difficulty getting air in and not getting air out
Restrictive defect is defined by?
Based on a reduced TLC
A decreased VC in the presence of a normal to increased FEV1?FVC ratio is suggestive of restriction but should also have lung volumes to confirm
Mild restrictive disease
TLC = <lln>70</lln>
Moderate restrictive disease
TLC = <70 and >60
Severe restrictive disease
TLC = <60
Causes of decreased TLC in restrictive lung disease
- Interstital lung disease/pneumoconiosis
- scarring and fibrosis of alveolar septae
- Loss of lung tissue
- Surgical resection
- Breathing mechanics
- mechanical/neuromuscular disease leads to a restrictive process however the lungs themselves are normal
- Obesity
- restriction due to the chest wall and abdomen impinging on the thoracic space
- lung parenchyma is normal
Obesity mechanism of decreased TLC
2 listed
- restriction due to the chest wall and abdomen impinging on the thoracic space
- lung parenchyma is normal
Breathing mechanics mechanism of decreased TLC
A mechanical/neuromuscular disease leads to a restrictive process however the lungs themselves are normal
Loss of lung tissue mechanisms of decreased TLC
Surgical resection
Interstitial lung disease/pneumoconiosis mechanism of decreased TLC
scarring and fibrosis of alveolar septae
DLCO AKA
Diffusion capacity for Carbon Monoxide
DLCO test
- Assesses the amount of functional alveolar-capillary surface area or how much blood is in the lung available for gas exchange
- Used to assess whether lung parenchyma is normal; particularly in restrictive processes
- Decrease can be an early sign of pulmonary fibrosis or pulmonary vascular disease
What can cause a decreased DLCO?
- Obstructive lung disease (emphysema: loss of alveolar surface area)
- Restrictive lung disease (interstital lung disease, not usually in obesity or neuromuscular weakness)
- Radiation therapy
- Amiodarone Bleomycin Nitrofurantoin and other chemotherapies
- Pulmonary vascular disease: PE/pHTN

Interpretation considerations of PFTs
5 listed
- Interpretation should be made in light of the clinical question
- No single test is diagnostic
- Results can be affected by patient effort, machine reproducibility, disease state of the patient
- Evaluate the quality of the test
- Use of prediction equations are based on population studies and may not represent the patient being studied
Considerations for the quality of a test
3 listed
- The lab should follow ATS recommendations (special training and certification for RTs to perform PFTs
- Results should be reproducible
- Minimum of 6 seconds exhalation time with a 2-second plateau on a volume-time curve
Interpretation criteria
5 listed

PFT study

normal test

PFT Study

- this is obstructed
- and looks like they have a bronchodilator response
- FEV1/FVC = <48 so pretty bad and there is a response to bronchodilators

PFT Study

normal
PFT Study

- mildly restrictive and a little DLCO
- FEV1 and FVC is reduced but their ratio is normal
- DLCO is corrected for anemia
Obstructive vs Restrictive: Lung volume
obstructive ↑
Restrictive ↓
Obstructive vs Restrictive: FEV1
Obstructive: ↓↓
Restrictive: ↓
Obstructive vs Restrictive: FVC
Obstructive: ↓
Restrictive: ↓
Obstructive vs Restrictive: FEV1/FVC
Obstructive: ↓
Restrictive: nml/↑
Obstructive vs Restrictive
- Lung volume
- FEV1
- FVC
- FEV1/FVC

Case

Upper airway obstruction

PFT Prediction equations

PFT Normal curve

PFT Prediction equations Crapo

Obstructive defect
- A disproportionate reduction of maximal airflow with respect to the maximal lung volume
- FEV1 decreases more than FVC
- Earliest limitation is in small airways (FEF 25-75)
Obstructive defects treatments

Bronchodilatory response

Bronchodilator response

