Pulm-Testing Flashcards
What is FEV1?
forced expiratory volume exhaled in 1 second (FEV1)
What is FVC?
and forced expiratory volume until full exhalation, or forced vital capacity (FVC)
What is the FEV1/FVC ratio?
The FEV1/FVC ratio is used to assess for airway obstruction; a value less than 70% (the lower limit of normal) is consistent with airflow obstruction.
What is the FEV1 speifically used for in the FEV1/FVC ratio?
With evidence of obstruction, the degree of reduction in FEV1 is used to characterize the degree of obstruction. An FEV1 of 50% to 80% of predicted is classified as moderately reduced, 34% to 49% of predicted is severely reduced, and less than 34% of predicted is very severely reduced.
What is the bronchodilator challenge? What is a positive bronchodilator response?
a bronchodilator challenge (2 to 4 puffs of a short-acting β2-agonist) is often given to determine the reversibility of obstruction (which may be helpful in differentiating between asthma and COPD); an increase in FEV1 of 12% and at least 200 mL is considered a positive bronchodilator response.
What does an FEV1/FVC <70% mean?
A value less than 70% is consistent with airflow obstruction!
What does a normal FEV1/FVC mean?
A normal FEV1/FVC ratio may reflect normal lung function or may indicate a restrictive lung defect. However, if the FEV1 and the FVC are reduced proportionately with each other and are below the predicted normal values, the spirometry results are consistent with a restrictive defect.
Draw a normal flow volume loop
Figure 1 in the pulm book
Draw a flow volume loop for asthma
Figure 1 in the pulm book
Draw a flow volume loop for COPD
Figure 1 in the pulm book
Draw a flow volume loop for fixed obstruction/tracheal stenosis
Figure 1 in the pulm book
What is a bronchial challenge test useful for?
If ppl have a cough or dyspnea but normal spirometry, it induces bronchospasm to test for disease
How does the bronchial challenge test work?
Bronchial challenge testing uses a controlled inhaled stimulus to induce bronchospasm in association with spirometry. Methacholine is a commonly used agent that induces cholinergic bronchospasm at low concentrations. A positive test is indicated by a drop in the measured FEV1
How are methacholine challenge tests measured?
The provocative dose 20% (PD20) is the dose of methacholine that causes a significant drop in the FEV1 of 20% or greater. The ability to achieve a PD20 at low concentrations of methacholine indicates more easily induced obstruction and is sensitive for detecting asthma.
What is the TLC and RV?
total lung capacity (TLC), or the amount of air in the lungs after maximal inhalation, and residual volume (RV), the volume of air remaining in the lungs after a maximal exhalation
What happens to the TLC in obstructive lung diseases?
In obstructive lung diseases, an increased TLC is suggestive of hyperinflation and high compliance, and an increased RV is suggestive of air trapping.
How is DLCO measured?
The diffusing capacity for carbon monoxide (DLCO) is performed by having the patient take a single, deep breath containing a very low percentage of carbon monoxide and measuring the amount of subsequently exhaled carbon monoxide following a short period of breath holding.
What is DLCO a measure of?
DLCO is therefore useful as a measure of the capacity for gas transfer through the alveolar-capillary membrane.
What can cause elevated DLCO?
Clinical disorders that recruit blood to the alveoli (cardiac shunt, asthma, erythrocytosis, alveolar hemorrhage) can elevate DLCO levels
What causes a decreased DLCO?
In contrast, conditions that decrease the surface area available for diffusion, decrease permeability across the alveolar-capillary membrane, or otherwise interfere with gas transfer can reduce DLCO.
Ex: COPD from parenchymal destruction, chronic thromboembolic disease blocks the area
What is the 6 minute walk test used for?
Simple pulse oximetry and oxygen desaturation studies performed at rest and with exertion assess the need for oxygen supplementation. During a 6MWT, oxygen saturation, heart rate, dyspnea and fatigue level, and distance walked in 6 minutes are recorded. This relatively simple maneuver quantifies exercise tolerance, determines effective interventions, and helps predict morbidity and mortality. The 6MWT is routinely used before, during, and after pulmonary rehabilitation programs.
