Lung Volumes and Gas Distribution - Testing Equipment

1. Lung Volumes and Gas Distribution - Testing Equipment RET 2414L Pulmonary Function Testing Module 3.1

2. Lung Volumes / Gas Distribution • Open-Circuit N2 Washout

3. Lung Volumes / Gas Distribution • Open-Circuit N2 Washout • Equipment Required • Spirometer • Tissot; a water-sealed spirometer with a volume of approximately 100 liters. Designed for collecting large volumes of exhaled air • Pneumotachometer

4. Lung Volumes / Gas Distribution • Open-Circuit N2 Washout • Equipment Required • Free- Breathing valve • Valve is opened or closed either manually or by computer control to allow patient to be switched from breathing room air to breathing gas from spirometer or special circuit • Deadspace of valve is determined by closing off all ports and filling the valve with water. The volume of water is the deadspace volume • Oxygen source

5. Lung Volumes / Gas Distribution • Open-Circuit N2 Washout • Equipment Required • Nitrogen analyzer • Giesler Tube Ionizer • Measurement on the basis of photointensity (emission spectroscopy) • Sample is pumped (vacuum pump) into an ionizer chamber where a light is emitted and monitored by a phototube. Intensity of light is directly proportional to the percent of N2

6. Lung Volumes / Gas Distribution • Open-Circuit N2 Washout • Equipment Required • Nitrogen analyzer • Measurement range (0 – 80%) • Calibrate to zero using 100% O2 (0% N2) and a known concentration of N2 • Troubleshooting • Sporadic or erratic zero readings which return to the expected value are caused by aspiration of water through the needle valve

7. Lung Volumes / Gas Distribution • Single-Breath N2 Washout • Equipment Required • Same as equipment used for open-circuit N2 washout

8. Lung Volumes / Gas Distribution • Closed-Circuit He Dilution

9. Lung Volumes / Gas Distribution • Closed-Circuit He Dilution • Equipment Required • Spirometer • Volume displacement • Directional breathing circuit • Free breathing valve • He source • O2 source • Allows addition of O2 during test to replenish O2 consumed by patient • Maintains constant system volume

10. Lung Volumes / Gas Distribution • Closed-Circuit He Dilution • Equipment Required • He analyzer • Thermal conductivity analyzer (wheatstone bridge) • Measurement range (0 – 10%) • Calibrate to room air (0% He) and a know amount of He (10%), then re-zero. • CO2 and water vapor must be removed from gas prior to being analyzed

11. Lung Volumes / Gas Distribution • Closed-Circuit He Dilution • Equipment Required • Fan or Blower • Promotes gas mixing within a rebreathing circuit • CO2 absorber (Scrubber) • Needed for tests requiring rebreathing • Sodium hydroxide (NaOH) – “Soda lime” • Light brown to white - exhausted • Barium hydroxide (BaOH2) – “Baralyme” • White to purple – exhausted • By product is water • Place upstream from H2O absorber

12. Lung Volumes / Gas Distribution • Closed-Circuit He Dilution • Equipment Required • H2O absorber • Removes moisture as patient breaths through the system • Moisture adversely affects analyzer • Calcium sulfate (CaSO4) • Place in-line after CO2 absorber • Desiccant color changes from blue to pink when exhausted

13. Lung Volumes / Gas Distribution • Body Plethysmograph • AKA: “Body Box”

14. Lung Volumes / Gas Distribution • Body Plethysmograph • Two types • Constant-volume, variable-pressure • “Pressure Plethysmograph” • Flow or variable-volume • “Flow Plethysmograph” • Both measure thoracic gas volumes and airway resistance and it derivatives • Both use a pneumotachometer to measure flow and a mouth transducer with a shutter to measure alveolar pressure

15. Lung Volumes / Gas Distribution • Body Box • Calibration • Mouth pressure is verified with a mercury or water barometer • Flows are verified with a rotometer (flow-metering device) or a 3-liter syringe • Box pressure is calibrated by using a sine-wave rotary pump • simulates inspiratory/expiratory volumes