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RES 131 PowerPoint Presentation

RES 131

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RES 131

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  1. RES 131 Pulmonary Function Testing

  2. Laboratory Instrumentation • TWO TYPES OF SPIROMETERS AVAILIBLE IN THE PFT LAB. • VOLUME-DISPLACING • Sometimes known as “volume collecting” • FLOW-SENSING

  3. VOLUME-DISPLACING SPIROMETERS • COLLECTS EXHALED AIR • ACTS AS A RESEVOIR FOR INHALED AIR.

  4. WATER SEAL SPIROMETER • CONSISTS OF THREE CYLINDERS • ONE CYLINDER WITH OPENING ON TOP • SECOND CYLINDER WITH OPENING ON BOTTOM • THIRD CYLINDER BETWEEN 1ST AND 2ND WITH OPENING ON BOTTOM

  5. BELLOWS SPIROMETER • USUALLY CONSISTS OF : • SOFT FLEXIBLE BELLOWS • LATEX OR RUBBER • RIGID OR SEMI-RIGID PANELS ON EITHER SIDE OF THE BELLOWS

  6. DRY ROLLING SEAL • COMPRISED OF A PISTON IN A CYLINDER • USES A SOFT SILICONE BASED ELASTIC MATERIAL AS A SEALING COMPONENT • OLD SYSTEMS USED A LEATHER ROLLING SEAL

  7. DIAPHRAGM SPIROMETER • CONSISTS OF: • HOUSING • UPPER AND LOWER • DIAPHRAGM • PUSHER PLATE

  8. VOLUME DISPLACEMENT SPIROMETER'S • GENERALLY, BEFORE TESTING STARTS, THESE SPIROMETER'S ARE EMPTY • SOME TYPES ALLOW PRESETTING OR FILLING BEFORE TESTING

  9. DESIRABLE CHARACTERISTICS • DIRECTLY MEASURE VOLUME • LOW COST • EASE OF OPERATION • WATER-SEAL SPIROMETER IS CONSIDERED TO BE THE “GOLD STANDARD”

  10. UNDESIRABLE CHARACTERISTICS • SOME VERY LARGE AND BULKY • LESS PORTABLE • WATER MUST BE CHANGED • LEAKS • MANUAL CALCULATION REQUIRED IF NO MICROPROCESSOR

  11. FLOW-SENSING SPIROMETER'S • VOLUME IS CALCULATED BY MULTIPLYING: • FLOW BY TIME • THIS IS KNOWN AS “INTEGRATION” • REQUIRES A COMPUTER OR MICROPROCESSOR

  12. FOUR TYPES OF FLOW SENSING SPIROMETER'S • PNEUMOTACHOGRAPH • HOT-WIRE ANEMOMETER • TURBINE DEVICE • VORTEX DEVICE

  13. PNEUMOTACHOGRAPH • ALSO KNOWN AS “DIFFERENTIAL PRESSURE DEVICE” • TUBE WITH FIXED RESISTANCE • CONTAINS A BUNDLE OF CAPILLARY TUBES OR FINE MESH SCREEN(S)

  14. PNEUMOTACHOGRAPH • ACCURACY BASED ON FIXED RESISTANCE • CHANGES IN RESISTANCE AFFECT ACCURACY • WATER VAPOR • SECRETIONS • MANY ARE HEATED TO PREVENT CONDENSATION

  15. HOT-WIRE ANEMOMETER • FINE WIRE IN CENTER OF TUBE • AIR MOVING THROUGH THE TUBE COOLS THE WIRE • ELECTRICAL CURRENT IS PASSED THROUGH WIRE TO MAINTAIN TEMPERATURE • CURRENT NEEDED TO MAINTAIN TEMP IS MEASURED

  16. HOT-WIRE ANEMOMETER • UNABLE TO MEASURE TURBULENT FLOWS ACCURATELY • LONG TUBE REQUIRED TO CREATE LAMINAR FLOW • FRAGILE

  17. TURBINE DEVICE • TURBINE INCREASES SPEED WITH INCREASING FLOW • REVOLUTIONS ARE MEASURED • INERTIA CREATES INACCURACY

  18. TURBINE DEVICE • NOT AFFECTED BY: • TURBULENT FLOW • MOISTURE • GAS COMPOSITION

  19. VORTEX DEVICE • STRUTS IN AIRFLOW CAUSE TURBULENCE RESULTING IN A VORTEX • VORTEXES ARE COUNTED

  20. VORTEX DEVICE • NOT SENSITIVE ENOUGH TO MEASURE LOW FLOWS

  21. Flow Sensing Spirometers • DESIRABLE CHARACTERISTICS • SMALLER AND MORE PORTABLE • COMPUTERIZED, NO MANUAL CALCULATIONS • MANY PROVIDE QUICK REFERENCE VALUES • CAN MEASURE BI-DIRECTIONAL FLOW

  22. Flow Sensing Spirometers • UNDESIRABLE CHARACTERISTICS • MORE KNOWLEDGE REQUIRE TO OPERATE COMPUTER • FREQUENT AND CAREFUL CALIBRATION • MOISTURE AND SECRETIONS CAUSE INACCURACY • GAS COMPOSITION CAN AFFECT RESULTS • MAY NOT SENSE LOW FLOWS

  23. CHOOSING A SPIROMETER • RECOMMENDATIONS FOR SPIROMETER'S ARE PUBLISHED BY THE AMERICAN THORACIC SOCIETY • PUBLISHED IN 1979, 1987 AND THE LATEST IN 1995

  24. SPIROMETER'S FOR FORCED EXPIRATORY MANEUVERS • ABLE TO MEASURE VOLUMES OF AT LEAST 8 LITERS • FLOWRATES (INSPIRATORY AND EXPIRATORY) BETWEEN 0 AND 12 LITERS PER SECOND

  25. SPIROMETER'S FOR FORCED EXPIRATORY MANEUVERS • ABLE TO COLLECT OR MEASURE VOLUMES FOR 15 SECONDS • IF THE SPIROMETER IS USED TO MEASURE THE FEV1, THE BACK EXTRAPOLATION METHOD SHOULD BE USED

  26. SPIROMETRY DISPLAYS • TWO WAYS TO DISPLAY THE SPIROGRAM • VOLUME-TIME • FLOW-VOLUME

  27. VOLUME-TIME DISPLAY • VOLUME IS DISPLAYED ON THE Y AXIS (VERTICAL) • TIME IS DISPLAYED ON THE X AXIS (HORIZONTAL)

  28. VOLUME-TIME DISPLAY • USEFUL IN EVALUATING THE LENGTH OF A TEST MANEUVER • ALLOWS ASSESSMENT OF VOLUME PLATEAU DURING THE TERMINAL PORTION OF THE TRIAL

  29. FLOW-VOLUME DISPLAY • FLOW IS DISPLAYED ON THE Y AXIS (VERTICAL) • VOLUME IS DISPLAYED ON THE X AXIS (HORIZONTAL)

  30. FLOW VOLUME DISPLAY • MOST USEFUL IN EVALUATING THE START OF TEST • TYPICALLY, THE GRAPH IS SCALED SO THAT THE FLOW REPRESENTATION IS TWICE THAT OF THE VOLUME

  31. CALIBRATION OF PULMONARY FUNCTION INSTRUMENTATION • Without a conscientiously applied calibration program, pulmonary function instruments may generate erroneous information

  32. CALIBRATION • Calibration of volume collecting and flow sensing SPIROMETER'S require the use of a calibration syringe

  33. Calibration of volume collecting SPIROMETER'S • Patient testing tubing should be attached • Inject the entire calibration syringe volume • Observe the pen or graphic display

  34. Calibration of volume collecting SPIROMETER'S • If the display or line does not travel in a straight line, there is a leak • If no leak is present, the indicated volume should be equal the volume of the calibration syringe within +/-3%

  35. Calibration of volume collecting SPIROMETER'S • Calculation of acceptable calibration error • Multiply the syringe volume by 3% (.03) • 3.0 x .03 = .09 • Add and subtract the calculated value from the known value • 3.0 L + .09 = 3.09 L • 3.0 L - .09 = 2.91 L

  36. Calibration of flow- sensing SPIROMETER'S • This type of spirometer of ten has a menu option for calibration • At least one injection from the calibration syringe should be with a reported value within +/- 3% • Usually several injections are completed

  37. Calibration of flow- sensing SPIROMETER'S • ATS recommends varying the flow rate of the injections • Once at approx. 3 L/sec (1 second) • Once at approx. .05 L/sec (6 seconds) • Once at a rate between the previous two

  38. Calibration • If either type of spirometer cannot meet the accuracy standards, the spirometer may not be used. • Calibration must be completed at least daily or whenever accuracy is questioned

  39. Calibration • ATS standards require the documentation of the calibration • A log book should be kept, documenting the calibration values obtained

  40. Quality Control • Activities used to maintain Quality • Laboratory Standards • Quarterly testing of known subjects with stable pulmonary conditions • Recorder time sweep • Check the accuracy of the recorder by stop watch