Plethysmography Procedure

Overview

Plethysmography is a test to measure lung volume and airway resistance. This guide provides a step-by-step process for conducting plethysmography and alternative methods if needed.

Setup

• Patient Preparation
  • Sit the patient in the plethysmography box.
  • Attach a nose clip to the patient.
  • Instruct the patient to place their hands on their cheeks.
  • Close the door of the plethysmography box.
  • Ensure the patient breathes normally.

Procedure for Total Lung Capacity (TGV)

1. Pressure Equilibration

   • Close the box vent, open, and then close it again to equilibrate pressure.
   • Ensure the patient breathes in the stability area (green area on the quality control gauge).

2. Breath Collection

   • Select TGV on the screen.
   • Collect at least four stable tidal breaths.

3. Closed Shutter Panting

   • At the end of a breath, press the space bar to start closed shutter panting.
   • Use a metronome to guide the panting rate.
   • Instruct the patient to inhale and exhale maximally, ensuring they blow out completely.
   • Press the space bar to end the test.

4. Quality Control

   • Check the quality graph for closed panting rate.
   • The graph will show green if within the acceptable range.
   • Display switch and error in the center if present.

Alternative Method

• Nitrogen Washout: Use as an alternative if plethysmography is not feasible.

Procedure for Airways Resistance and Thoracic Gas Volume

1. Initial Setup

   • Follow similar setup as TGV with patient seated in the box and nose clip attached.
   • Equilibrate box pressure similar to TGV.

2. Breath Collection

   • Select RAW on the screen.
   • Collect at least four stable tidal breaths.

3. Panting

   • Press space bar to begin open shutter panting, guided by a metronome.
   • After open shutter panting, press space bar to collect four closed shutter pants.
   • Use a metronome to guide the panting rate.
   • Press space bar to end the test.

4. Notes on TGV and RAW Combination

   • Performing both tests together may result in difficulty achieving an acceptable switch.
   • Recommended to perform TGV separately.

Graph Adjustment

• Graph Types

  • Double-click on the TGV RAW graph.
  • Select ‘Close’ for TGV and ‘Open’ for RAW.
  • Adjust graph angle and position as needed.

• Guides and Display

  • Select 'Show Guides' to place parallel lines on the graph.
  • Select 'Open' to display open shutter pants, showing four breaths superimposed or separately.