Diagnostics: PFT Flashcards
Most accurate measure of Pulmonary fxn
Pleth Box
Signs of Air Trapping/Pseudorespiration
Decreased FVC, Increased TLC
Three types of pulmonary fxn testing?
Spirometry Lung Volumes Diffusing Capacity
Types of Spirometry tests
Methacholine Cronchodilator Challenge Neuromuscular Protocol
Types of Lung Volume Tests
Helium dilution Nitrogen washout Plethysmography
Why do PFTs?
Explain Dyspnea, hypoxemia Objectively Follow Disease Pre-Op Exams
Total Lung Capacity =
Inspir. Reserve + Tidal + Expiratory Reserve + Residual
Vital Capacity =
Insp. Reserve + Tidal + Exp. Reserve
Functional Residual Capacity =
Expiratory Reserve Vol + Residual Vol.
What do patients do in spirometry?
Maximal breath to TLC, then blows out as hard/fast as possible
Name for total volume expired in a spirometry test
Forced Vital Capacity
Name of the volume expired in the first second of a spirometry test?
FEV1
Most reproducible measure of flow rate over time
FEV1
In PFTing curves, the portion above the axis is _______ and the portion below the axis is ______
Exhalation Inhalation
Criteria for an acceptable PFT?
Smooth, Continuous curve Good Start Finish w/ plateau for 1 sec
Obstructive pattern should make you suspect…
Asthma, emphysema, Chronic Bronchitis
Restrictive pattern of PFT should make you suspect…
Pulm. fibrosis, Hypersensitivity pneumonitis, sarcoidosis, silicosis, neuromuscular probs
What happens in an extrathoracic resp probs
Closure on insp. Opening on expiration (Flat on bottom of loop) Example – Laryngeal Cancer, Vocal Cord Adduction
What happens in intrathoracic resp probs
Open on inspiration, Closure on expiration (Flat on top, normal curve below)
If no confidence intervals are given, what is the cutoff for diagnosing an obstruction?
70% FEV1/FVC Look for a scooped loop
With an FEV1/FVC ration below 70%, you determine the patient has an obstructive disease. They have a normal FVC. What do you assess next?
Post-dilator FEV1 and FVC. If Albuterol fixes it, its Asthma. If not, its COPD
How do you distinguish which type of COPD you have?
DLCO Down in emphysema Normal in Chronic bronchitis
How do you determine is a restrictive lung disease patient has a parenchymal or extrapulmonary restriction?
DLCO Down in parenchymal Normal in extrapulmonary
Sign of a positive bronchodilator change
FEV1 or FVC increase of 12% AND absolute chance of 200 mL after bronchodilaton
In mathacholine testing, a FEV1 drop of ______ at a low concentration is diagnostic of hyperresponsiveness
more than 20%
Neuromuscular disease presents as…
Restriction
What do you do in neuromuscular testing
Assess resp. muscle strength (make patient forcibly inhale/exhale against a closed mouthpiece attached to a pressure gauge).
Normal Max Inspiratory Pressure? Expiratory?
Insp. – 65 Expiratory – 80
Normal Maximal Voluntary Ventillation
Normal is FEV1 x 35
How does a Helium Dilution test work?
Known volume of inert gas (He) at a known concentration is inhaled. Gas is diluted by air volume already in lungs. Concentration of exhaled gas is measured, reflects the initial volume of gas in the lungs.
How does a Nitrogen Washout test work?
Put a person on 100% Oxygen, measure the amount of Nitrogen being released with their breaths over time.
What happens in plethysmography?
Subject makes an inspiratory effort against a closed airway, which increased the volume of the lung. Airway pressure decreases and the box pressure increases. Use P1V1=P2V2
Volume measured by He dilutiona nd Nitrogen washout?
Functional Volume Does NOT measure areas with Trapped Gas Inaccurate in severe obstructive lung disease
What are you learning in a DLCO test?
The amoutn of gas that is able to diffuse across the alveolar-capillary membrane
How do you measure diffusing capacity?
Inhale known conc. of CO + Helium to TLC. Hold breath for 10 seconds Exhale and measure the CO and Helium in expired gas
Main determinants of diffusing capacity?
Surface Area Capillary Flow Membrane Diffusing Capacity (kCO)
DLCO =
KCO X VA
In a patient with normal lung volumes and spirometry, a low DLCO indicates…
Pulmonary vascular disorder.
Interpret
Normal PFT
Interpret
PFT Obstructive
Intrepret
PFT - Restrictive
Fixed, Variable Extrathoracic, or Variable Intrathoracic?
Fixed
Fixed, Variable Extrathoracic, or Variable Intrathoracic?
Variabe Extrathoracic
Fixed, Variable Extrathoracic, or Variable Intrathoracic?
Variable Intrathoracic
