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Phys2 Intro to PFT
| Question | Answer |
|---|---|
| 2 main types of pulmonary function tests | 1.Tests of ventilatory capacity (forced expiration, measuring lung Vol, FRC measurement). 2.Tests for detection of Hypoxemia (Measuring arterial BL gases, V/Q scan, measuring vent inequality, measuring diffusion capacity). |
| Obstructive Vs Restrictive disease in terms of lung VOLUME and airway RESISTANCE | OBSTRUCTIVE: 1.Vol: Large. 2.Resistance: Increased. RESTRICTIVE: 1.Vol: small. 2.Resistance: Normal/Dec. **These 2 main types of lung disease can be detected & differentiated b/w on the basis of ventilatory capacity. |
| What type of ventilatory capacity test is used to differentiate b/w Obstructive and Restrictive lung diseases? | Forced Expiration test. **Adv: Simple, cheap, no need for large equipment, performed in most clinics |
| What two key parameters can be measured by forced expiration spirometry? | 1.Forced Expiratory Vol (FEV1): Total volume of air exhaled in the 1st second. 2.Forced Vital Capacity (FVC): total volume of air exhaled before the start of next inspiration. **These are altered w/ lung disease. |
| Obstructive lung disease affect on FEV1 and FVC | Both are reduced, FEV1 is decreased MORE than FVC: 1FEV1: 1.3L (normal: 4L). 2.FVC: 3.1L (5L). **FEV1/FVC ratio: (LESS than normal 80%) 0.42 (normal: 0.8), less steep dec in vol slope |
| Restrictive lung disease affect on FEV1 and FVC | Both are reduced. FVC is decreased MORE than FEV1: 1.FEV1: 2.8L (normal: 4L). 2.FVC: 3.1L (normal: 5L). **FEV1/FVC ratio: (HIGHER than normal 80%) 0.9 (normal: 0.8), STEEPER dec in vol slope. |
| Which lung disease causes an INCREASE FEV1/FVC ratio? | RESTRICTIVE |
| Which Lung disease causes a DECREASE FEV1/FVC ratio? | OBSTRUCTIVE |
| What is the most useful parameter for distinguishing b/w obstructive and restrictive lung disease? | FEV1/FVC ratio: Obstructive < 0.8 < Restrictive |
| Factors determining FEV | 1.Lung Volume (Amt of air to be exhaled in 1 sec). 2.Airway resistance (affects Max airflow during expiration). 3.Airway Collapse (becomes main site of resistance during forced expiration). |
| How does Lung volume change FEV1 in obstructive lung disease? | A large starting volume means more air can potentially be exhaled in 1 second. **Increases FEV1 |
| How does Lung volume change FEV1 in restrictive lung disease? | A small starting volume means less air will be able to be exhaled in 1 second. **Decreases FEV1 |
| How will an INCREASE in airway resistance affect FEV1? | DECREASE it |
| How will airway collapse affect FEV1? | DECREASE it |
| Which of the 3 FEV1 parameters contributes the MOST to the decreased FEV1 in Obstructive disease? | Increased AIRWAY RESISTANCE |
| Which of the 3 FEV1 parameters contributes the MOST to the decreased FEV1 in Restrictive disease? | Small LUNG VOLUME |
| How is FVC reduced from 5L to 3.1L in restrictive disease? | function of Lower Lung volume |
| How is FVC reduced from 5L to 3.1L in obstructive disease? | The Inc airway resistance cuases an earlier airway collapse in the lungs, preventing further airflow and ending expiration EARLY! |
| What does Forced Expirational Flow Rate 25-75% measure? | This measures the rate of air flow over the middle portion of the expiration, and is a measure of airway resistance. **obtained from Forced Expiration Test |
| What is the normal FEF25-75% | 3.5L/sec |
| What is FEF in obstructive disease? | DECREASED to 1.4L/sec **expected with Inc airway resistance |
| What is FEF in restrictive disease? | INCREASED to 3.7L/sec **Due to Inc Radial Traction reducing airway resistance. |
| What type of Flow-volume curve can be created with simple spirometry? | Change in Lung Volume cruve |
| What is required in order to plot an absolute lung volume Flow-volume curve? | The Total volume inside the lungs (TLC, cannot obtain with simple spirometry) |
| Shape of an Obstructive Flow-Volume curve | tend to have reduced max flow rates & a scooped appearance during the latter part of expiration. **Low flow rate for high lung volume. |
| Shape of a Restrictive Flow-Volume curve | Similar shape as normal but the overall changes in volume are smaller. **High flow rate for low lung volume. |
| What is the lung capacity needed for conversion of volumes measured w/ simple sirometer into absolute lung volumes? | Function Residual Capacity (FRC) needed to determine where 0 lung volume is. |
| 2 tests used to find FRC? | 1.Helium Dilution: (breathe in gas mix w/ known Vol of He, which is diluted by vol of gas already in lungs. extent of dilute is measured). 2.Whole body plethysmography (sit in sealed box) |
| 3 main tests assessing Hypoxemia | 1.BL gas measurement. 2.V/Q inequality. 3.Diffusion capacity. |
| How is V/Q inequality tested? | Using inhaled Radioactive xenon to asses the distribution of ventilation. Radioactive albumin can be used to asses lung perfusion. |
| What molecule is used to measure diffusion capacity? | Carbon Monoxied (CO). **CO is used because its partial pressure in the capillary blood does not increase appreciably as CO diffuses |
| How is CO used to measure diffusion capacity? | The rate of disappearance of CO from the alveolar gas during a 10 sec breathe hold is measured. **DLCO (properties of barrier DL x mol wgt of CO) |
| What will happen to DLCO if there is a significant regional inequality of ventilation? | When the CO is breathed in, some wont get to the alveoli. This will DECREASE DLCO even though the barrier is not thickened. **Diffusion capacity will appear impared. |
| What will happen to the N2 at the lips if there is a ventilation inequality? | Once the pure O2 is expired first (coming from the dead space) and then the Initial spike of N2 (normal) but the less well ventilated areas release their N2 more slowly so the [N2] will continue to rise with expiration. |
| Will a well ventilated area have diluted N2? | YES. the not well ventilated lung units will have a much higher [N2] since O2 doesnt normally get in to dilute the N2 |
| Obstructive Lung Disease with DECREASED DLCO? | Emphysema **Decreased diffusion capacity |
| Obstructive Lung Disease with normal DLCO? | 1.Asthma. 2.Chronic Bronchitis. |
| Restrictive Lung Disease with DECREASED DLCO? | Interstitial Fibrosis **Decreased diffusion capacity |
| Restrictive Lung Disease with normal DLCO? | 1.Chest wall abnormality. 2.Neuromuscular problem. |
Created by:
WeeG
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