PFTs Flashcards
What are the types of PFTs?
Spirometry
Lung Volumes
Diffusion Capacity
What is spirometry?
What is the primary measurement?
measures how an individual inhales or exhales volume of air as a function of time
Primary measurement in spirometry is either volume or flow
What are the indications for spirometry?
Detecting & quantifying pulmonary impairment in cardiopulmonary diseases
Following the evolution of diseases & monitoring response to therapy
Monitoring the effects of environmental, occupational & drug exposures associated with lung injury
Assess preoperative risk
Assessing disability & impairment
What are the primary spirometric indices?
What else can be found with spirometry?
Forced Vital Capacity (FVC)
Forced Expiratory volume in 1 sec (FEV1)
Ratio FEV1/FVC
Flow-Volume Loop
How is the FVC test performed
having patient inhale to TLC & make a maximally forced exhalation into a spirometer
How is Exhaled volume measured in spirometry?
How is flow measured?
exhaled volume is measured as a function of time (volume-time curve)
Flow is also measured & displayed as function of exhaled volume (flow-volume loop)
How are patients classifed with spirometry?
Normal
Airflow obstruction
Restriction
What are the three types of ventilatory defects?
Obstructive Ventilatory Defects
Restrictive Ventilatory Defects
Mixed Ventilatory Defects
what are obstructive ventilatory defect?
decreased expiratory flows compared with a healthy persons
Early airway obstruction begins in the small airways & tends to reduce flows at lower lung volumes
Progressive slowing of expiratory flow is reflected in the concave shape on flow-volume curve
What is the primary marker for presence of airway obstruction?
FEV1/FVC ratio
FEV1/FVC<70% predicted
How is airway obstruction classified?
using the FEV1%
What is FEF25-75?
How is it useful?
How can it be used to diagnose airflow obstruction?
average forced expiratory flow rate over the mid 50% of FVC
helpful in diagnosing obstruction, but dependent on FVC
, a reduced FEF25-75 <60% & FEV1/FVC in low-normal range can confirm airflow obstruction
What is the degree o severity in obstructive defects using FEV1% pred?
mild= FEV1% > 80%
moderate = FEV1% 50-79%
severe = FEV1% 30-49%
very severe <35%
What is bronchodilator response?
How is the test performed?
used for patients with obsructive lung disease
obtaining baseline spirometry
administering SABA, waiting 15 mins
then repeat the spirometry
What is an improvement when administering a bronchodialtor response?
An improvement in FEV1 or FVC of 12% & 200ml from baseline is considered a positive response
Lack of response does not preclude a clinical response
What are restrictive defect characterized by?
why?
What is suggestive of a restrictive defect?
reduced FVC
reduced because of the smaller absolute lung volumes
FVC < 80% predicted is suggestive of a restrictive defect
When would you obtain lung volume to confirm restrictive defect?
If airway obstruction is present & FVC is low, a defect maybe present
Would recommend obtaining lung volumes to confirm the restrictive defect
What are differentials for restrictive lung disease?
Pleural Disease
Parenchymal Lung Disease
Chest Wall Disease
Neuromuscular Disorders
When are lung volume test used?
diagnose a restrictive lung disease & to determine the severity of the impairment
To help clarify whether a decrease in FVC is due to restriction or a consequence of air trapping due to airflow obstruction
What is restrictive lung disease defined as in lung volume test?
Restrictive lung disease is defined as a reduction in lung volumes, particularly VC & TLC
What are TLC ranges in normal restrictive lung diseases and obstructive lung diseases?
TLC Normal Range is 80-120% predicted
Restrictive Defect
TLC < 80% predicted
Obstructive Defect
TLC > 120% predicted
What does diffusion capacity represent and measure?
Represents the gas exchange capabilities of the lung
Measures the ability of gas to diffuse across the alveolar-capillary membrane using carbon monoxide (DLCO)
What does diffusion capacity depend upon?
Alveolar-capillary membrane
Hemoglobin concentration
Cardiac output
What is a decreased DLCO<80% predictive of?
Obstructive Lung Disease
Parenchymal Lung Disease
Pulmonary Vascular Disease
Anemia
What is a increased DLCO> 120% predictive of?
Asthma (maybe also normal)
Pulmonary Hemorrhage
Polycythemia
Left to Right Shunt
What is a systematic way to interpret spirometry?
Look at the Force Vital Capacity (FVC) to see if its within normal limits
Look at the FEV1 & determine if it is within normal limits
If both FVC & FEV1 are normal, then you do not have to go any further
If the FEV1/FVC is <70%, you probably have an obstructive defect
Severity can be determined by the FEV1%
If FEV1/FVC is >88% and/or FVC <80%, you probably have a restrictive defect & would consider obtaining lung volumes and/or diffusion capacity
What is a systematic way to determine Lung volume testing?
If the TLC < 80% predicted, then there is a restrictive ventilatory defect
If the TLC >80% predicted, but the FVC <80%, the patient does not have a restrictive defect
If the TLC >120% predicted, then there is a an obstructive ventilatory defect
when would you order DLCO?
To help differentiate asthma from emphysema
To help in the evaluation & determine, the severity of interstitial lung disease or restrictive lung disease
Evaluate cardiovascular disease
