| Q | A |
| what are spirometers used to measure? | Volumes and flow rates |
| what are the 2 types of spirometers used in PFTs? | water-seal and dry-rolling seal |
| what does a pneumotach measure? | flow |
| what are the 2 types of pneumotachometers used in PFTs? | turbine device (wright respirometer) and pressure differential (fleisch) |
| which type of spirometer is the most accurate? | water-sealed |
| what law is the body box based on? | Boyle's law--pressure and volume vary inversely if temperature is constant |
| what is measured with a plethysmograph? | FRC (functional residual capacity), Raw (airway resistant) |
| what 2 parameters does the calibration of the body box primarily involve? | Pressure: verified with a mercury or water barometer. Flows: verified with a rotometer |
| what is the advantage of the body box? | measures FRC more accurately in patients with obstructive lung disease |
| what are 3 disadvantages to the body box? | patients' physical limitations, claustrophobia, patient maybe unable to pant acceptably |
| Describe gas chromatograph | absorption type, measured in separator column by thermal conductivity. measures: Ne O2 N2 CO |
| Describe mass spectrometer | vacuumed into ionized chamber. gases are separated and analyzed. Measures: He N2 O2 CO2 |
| describe carbon dioxide/carbon monoxide gas analyzer | infrared absorption analyzer. measures CO and CO2 |
| describe Helium gas analyzer | thermal conductivity. measures percentage of He |
| describe nitrogen gas analyzer | geisler tube ionizer. measures percentage |
| describe the kymograph | plots volume (y-axis) against time (x-axis). inspiration upward deflection, expiration downward deflection |
| describe X-Y recorder | plots volume (x-axis) against flow(y-axis) records flow-volume loops |
| What standards must all equipment meet? | ATS-ACCP standards |
| how are volume calibrations and leak tests done? | using a large volume syringe (3 L) |
| how is flow calibration done? | using a rotometer |
| explain how gas analyzers are calibrated | by running a gas through it that is free of that particular gas |
| how are timing devices checked? | with a stopwatch |
| how is the plethysmograph calibrated? | rotometer for flows, barometer for pressure |
| describe how a patient is instructed to perform a vital capacity (VC)? | patient is instructed to take a maximal inspiration followed by a maximal exhalation with out force |
| What will the SVC provide? | important volumes to measure restrictive disease |
| what 5 volumes will be measured? | VT- tidal volume, normal breathing. IRV- inspiratory reserve volume. ERV- expiratory reserve volume. IC-inspiratory capacity. VC- vital capacity |
| IC formula | IRV + VT |
| VC formula | IRV + VT + ERV |
| what does a decrease in volume indicate (VC)? | restrictive disease |
| what is the best indicator of restrictive lung disease? | vital capacity |
| describe how a patient is instructed to perform a forced vital capacity? | take a maximal inspiration followed by a maximal expiration as forcefully and rapidly as possible |
| what will the FVC provide? | important flow rates used to measure obstructive disease |
| what 5 values will be measured? | FEV1- forced expiratory volume in 1 sec. FEF200-1200- forced expiratory flow. FEF25-75. PEFR-peak expiratory flow rate. FVC- forced vital capacity |
| is the FVC a volume or flow measurement? | volume |
| what is equal to the FVC? | SVC |
| what does it mean if the FVC is smaller than the SVC? | indicates obstruction (air trapping) |
| what does it mean if the FVC cannot be completed in 3 seconds? | obstruction |
| what is the best indicator of obstructive disease with a FVC? | FEV1/FVC |
| what is the minimum acceptable value for the FEV1/FVC? | 75% |
| what does it mean if the FEV1 is decreased but the FEV1/FVC is normal? | patient is restrictive only |
| what does a decrease in the FEF200-1200 indicate? | large airway obstruction |
| what is the FEF25-75 associated with? | the small airway |
| what is the PEFR used to evaluate? | asthmatic patients with pre & post bronchodilation |
| describe how the MVV is done | breath in and out as fast as possible until told to stop |
| what does it mean if the MVV is decreased? | obstructive disease, increased Raw, muscle weakness, decreased compliance and poor patient effort |
| what is pre and post bronchodilator used to measure? | measures the reversibility of an obstructive pattern |
| how much of a change in a post bronchodilator study is considered significant? | increase of 15% |
| how long should all bronchodilator therapy be held before a pre&post study? | 8 hours prior to testing |
| describe the He dilution test | (closed method) a know % of He is diluted by the patients FRC. changes in He% determine the FRC |
| describe the N2 washout test | (open method) the FRC is washed out by having patient breath 100% O2 to replace the N2 from the FRC. the amount of N2 removed is used to calculate FRC |
| what does the body box measure that is excluded from the FRC with the other procedures? | measures gases trapped inside the lung |
| what does a flow-volume loop measure? | measures the volumes and flow rates of the FVC |
| What does the single breath N2 elimination measure? | evenness of distribution of inspired gases, closing volume/closing capacity |
| where is the evenness of gas distribution shown on SB N2? | Phase III |
| what does phase IV show(SCN2)? | sudden rise in N2% called closing volume |
| what volumes make up closing capacity? | closing volume + RV = closing capacity |
| what does carbon monoxide diffusion capacity (DLco) measure? | all the factors that affect the diffusion of gas across the A-C membrane |
| explain the DLco-single breath procedure | patient breathes known amount of CO, He and air, holds breath for 10 seconds then exhales into machine then analyzed |
| what is the normal DLco? | 25 mL CO/min/mmHg |
| what 5 factors affect the DLco? | Hb, Hct; PCO2; body position; breath hold time; blood volume |
| what is the DLco decreased with? | pulmonary fibrosis, sarcoidosis, ARDS, edema, emphysema |
| how is a bronchial provocation performed? | administering a provocative agent to a patient to see if there is airway hyperactivity |
| how do you know if a bronchial provocation test is positive? | 20% decrease in FEV1 |
| what is meant by the provocative dose or PD20%? | the dosage of methacholine required for a positive test |
| when evaluating a PFT, what is the formula to calculate the % predicted? | actual value / predicted value = % predicted |
| what three factors are predicted values primarily based on? | age, height, gender |
| how many acceptable PFTs should be recorded? | minimum of 3 |
| how much should each PFT not differ by? | no more than 5% |
| what is meant by the "best test"? | highest FVC + FEV1 |
| restrictive only patients: | low volumes, VC or FVC |
| Obstructive only patients: | low flows, FEV1 |
| both obstructive and restrictive patients | low flows and low volumes |
| what type of lung disease has decreased flows? | obstructive disease |
| what type of lung disease has decrease volumes? | restrictive disease |
