9.2 Lab Protocol

Approximate Time: 3 hours

“This material is adapted from iWorx Systems Inc with permission.”

Setup

1. On your table, find a new disposable respiratory kit (Figure 1A) and open it.
2. Attach the blue filter to one side of the flow head, then connect the mouthpiece to the other side, as shown in Figure 1B.

 1A.   

1B.

Figure 1. Spirometer Setup: A. The student respiratory kit. B. The flow head connected to the internal spirometer of the IXTA unit.

Before Starting

1. Please read the procedures for each exercise completely before beginning the lab. You should have a good understanding of how to perform these lab exercises before making recordings.
2. The spirometer will monitor breathing from a subject. It is important that the subject is healthy and has no history of respiratory or cardiovascular problems. 
3. The outlets connected to the airflow tubing should always be pointed up to avoid problems with condensation developing within the tubing.
4. To reduce turbulence, the subject should place their lips around the cardboard mouthpiece attached to the flow head.
5. Use a nose-clip to prevent air from entering or leaving the nose as the subject is breathing. Air passes through the nose causes errors in the lung volume values.

Start the Software

1. Turn on the iWorx TA-ROAM box.
2. Click the Labscribe25 icon on the computer screen.
3. A default mode box will appear, click OK. A pop-up box should appear indication that the iWorx IX-TA ROAM (hardware) has been found, click.
4. When the program opens, Click on Settings on the toolbar on top. Select Human Spirometry and then Breathing-Rest Exercise
5. LabScribe will appear on the computer screen as configured by the Human Spirometry settings.
6. Check the calibration of your spirometer on the Lung Volume channel:

Click on the words STPD Human (Air Flow), that are next to the title of the Lung Volumes channel, to open the computed function pull-down menu.

Select Setup Function from the drop-down menu to open the Spirometer Calibration dialog window. Ensure that the displayed numbers match those in the image below.

7. Allow the IXTA to warm up for 10 minutes before recording for the first time.

8. Ensure the subject breathes through the side of the flow head marked with red (the cable connected to the red port).

Procedure

1. Instruct the subject to:

• Sit quietly and become accustomed to breathing through the spirometer flow head.
• Make sure the subject is breathing through the red port side of the flow head (red mark on the flow head).
• Breathe normally before any recordings are made.
• Hold the flow head so that its outlets are pointed up.
• Remove the flow head from his or her mouth and hold it at the mouth level in a position that prevents a breath from moving through the flow head.

Note: The LabScribe software will zero the Lung Volumes channel during the first ten seconds of recording.  No air should be moving through the flow head during this time.

1. Type Resting in the Mark box.
2. Click Record. After waiting at least 10 seconds for the Lung Volumes channel to zero, have the subject place the flow head in his o her mouth and begin breathing.  Click the mark button to mark the recording.
3. Click the AutoScale All button. Notice the slowly moving wave on the Lung Volumes channel.  Record five-six breaths, which normally takes about forty-five seconds to record.
4. Type Forced in the Mark box. Click the mark button as the subject inhales as deeply as possible.  After reaching his or her maximum inhalation volume, the subject should exhale as quickly as possible, Do not hold it in. Then do another inhale before returning to breathing normally.  Make sure to blow all the air out of the maximum exhale.
5. After the forced exhalation is complete, the subject should continue to breathe normally through the spirometer for five-six breath cycles.
6. Click Stop to halt recording. Your data may look like the image below (Fig 2).

Fig. 2. Air flow and lung volumes of the normal and forced breathing of a subject at rest.

Data Analysis-Normal Breathing at Rest

1. Scroll through the recording and find the section of data recorded when the subject was breathing while resting.
2. Use the Display Time icons to adjust the Display Time of the Main Window to show the complete breathing cycles on the Main Window. The adjacent breathing cycles can also be selected by:

• Placing the cursors on either side a group of complete breathing cycles; and
• Clicking the Zoom between Cursors button on the LabScribe toolbar to expand the selected breathing cycles to the width of the Main Window.

3. Click on the Analysis window icon in the toolbar to transfer the data displayed in the Main window to the Analysis window.

4. Look at the Function Table that is above the uppermost channel displayed in the Analysis window. The mathematical functions, V2-V1, Max_dv/dt, and T2-T1 should appear in this table.  Values for V2-V1, Max_dv/dt, and T2-T1 on each channel are seen in the table across the top margin of each channel.

5. On the Lung Volumes channel, use the mouse to click on and drag the cursors to specific points on the recording to measure the following volumes:

• Tidal Volume (TV), which is the volume of air inhaled or exhaled during a normal breathing cycle.  Place one cursor in the through prior to inhalation, and the second cursor on the peak of the cycle.  The value for the V2-V1 function on the Lung Volumes channel is the tidal volume.
• Maximum Inspiratory Flow Rate, which is the maximum rate of air movement during inhalation.  Leave the cursors in the same positions used to measure the tidal volume.  The value for the Max_dv/dt function on the Lung Volumes channel is the maximum inspiratory flow rate for that breath cycle.Figure 3: Breathing pattern of a subject at rest, displayed on the Lung Volumes channel in the Analysis window.  The cursors are positioned on the trough and the peak of the breath cycle to measure the tidal volume (TV) with V2-V1 function and the maximum inspiratory flow rate with the Max_dv/dt function.

• Maximum Inspiratory Flow Rate, which is the maximum rate of air movement during inhalation.  Leave the cursors in the same positions used to measure the tidal volume.  The value for the Max_dv/dt function on the Lung Volumes channel is the maximum inspiratory flow rate for that breath cycle. This function is used since the exhalation portion of the breath cycle has a negative slope.

Figure 4: Breathing pattern of a subject at rest, displayed on the Lung Volumes channel in the Analysis window.  The cursors are positioned on the peak of the breath cycle and the trough of the succeeding cycle to measure the maximum expiratory flow rate with the Min_dv/dt function.

6. Once the cursors are placed in the correct positions for determining the volumes and rates of each breath cycle, the values of the parameters in the Function Table can be recorded in the table below.

7. Breath Period, which is the duration of each breathing cycle.  To measure the breath period of the subject during breathing at rest, place one cursor on a peak of a breath cycle, and the second cursor on the peak of an adjacent cycle.  The value for T2-T1 on the Lung Volumes channel is the period of the breath cycle.

Figure 5: Normal breathing pattern of a subject at rest, displayed on the Lung Volumes channel in the Analysis window.  The cursors are positioned on the peaks of successive breath cycles to measure the breath period with the T2-T1 function.

8. Repeat the measurements of tidal volume, maximum inspiratory flow rate, maximum expiratory flow rate, and breath period on two additional normal breath cycles.

9. Average the three values obtained for each parameter and enter the means in Table 1.

10. Calculate the normal breathing rate of the subject at rest using the following equation:

Breath Rate (breaths/minute) = 60 (seconds/minute) / mean breath period (seconds/breath)

12. Multiply the mean tidal volume by the breathing rate to calculate the volume of air passing in and out of the resting subject’s lungs each minute.

Volume of air passing in and out of the resting subject’s lungs each minute = Mean Tidal Volume x Breathing Rate

13. Record the values for these calculations in the table 1.

Table 1

Data Analysis-Forced Expiration at Rest

1. Use the slider or the arrows on the scroll bar, at the bottom of the Analysis window, to position data recorded when the subject exhaled with maximum force in the window.
2. Use the Display Time icons to adjust the Display Time of the Analysis window to show the forced expiration curve and the two normal breaths both before and after the force expiration curve, on the same window.
3. Place the cursors on the forced expiration data displayed on the Lung Volumes channel to measure the following volumes and rates using the V2-V1, T2-T1, Max_dv/dt, and Min_dv/dt functions.
   1. Inspiratory Reserve Volume (IRV), by placing one cursor on the peak of the normal breath prior to the maximum inhalation and the second cursor on the peak of the forced breath cycle.  The value for V2-V1 function on the Lung Volumes channel is the inspiratory reserve volume.  Enter the value in Table 2.
   2. Forced Inspiratory Flow Rate, by keeping the cursors in the same positions used of measuring IRV.  The value for the Max_dv/dt function on the Lung Volumes channel is the forced inspiratory flow rate. Enter the value in Table 2.
   3. Forced Vital Capacity (FVC), by placing one cursor on the peak of the forced breath cycle and the second cursor on the flat line after the subject has expelled all the air from their lungs. The value for the V2-V1 function on the Lung Volumes channels is the forced vital capacity. Enter the value in Table 2.
   4. Forced Expiratory Flow Rate, by keeping the cursors in the same positions used for measuring VC. The value for the Min_dv/dt function on the Lung Volumes channels is the forced expiratory flow rate. Enter the value in Table 2.
   5. Expiratory Reserve Volume (ERV), by placing one cursor in the trough before maximal inhalation and the second cursor on the flat line after subject has expelled all the air from their lungs.  The value for the V2-V1 function on the Lung Volumes channel is the expiratory reserve volume. Enter the value in Table 2.
   6. Forced Expiratory Volume at 1 Second (FEV1), by placing one cursor on the peak of the maximum inhalation and the second cursor on the data point that is one second after the peak.  Use the T2-T1 function to determine the data  point that is one second after the peak. The value for the V2-V1 function on the Lung Volumes channel is the forced expiratory volume at one second. Enter the value in Table 2.
   7. Forced Expiratory Volume at 3 Seconds (FEV3), by placing one cursor on the peak of the maximum inhalation and the second cursor on the data point that is three seconds after the peak.  Use the T2-T1 function to determine the data points that is three seconds after the peak.  The value for the V2-V1 function on the Lung Volumes channel is the forced expiratory volume at three seconds. Enter the value in Table 2.

Figure 6: Forced Expiration at Rest

Table 2

Compare the FEV₁/FVC and FEV₃/FVC ratios of the subject to the normal values of 0.80 and 0.95, respectively, for young healthy adults. Both of these ratios decrease with age.

• In obstructive airway disease, like asthma, bronchitis, or emphysema, both FVC and FEV₁ are reduced, and FEV₁/FVC ratios are usually less than 0.70.
• In restrictive lung diseases, like fibrosis, FVC is reduced.  But, because of the low compliance and high recoil of the lungs, the FEV₁/FVC ratio many be normal (about0.80) or greater than normal (higher than 0.85).

Procedure

1. In this exercise, use the same healthy subject whose breathing parameters at rest were measured in Activity 1.
2. TypeAfterExercise in the Mark Box.
3. The subject should exercise to sufficiently elevate breathing rate, but with minimal class disruption. Use the treadmills or exercise bikes are a good method.  The subject should sit down immediately after the exercise period.
4. Click Record. After waiting ten seconds have the subject place the flow head in his or her mouth and begin breathing.  Click the mark button to mark the recording.
5. Click the AutoScale All button. Record at least five-six breaths as the subject is recovering from exercise.  Remember the baseline of the Lung Volume channel automatically resets every sixty seconds.
6. Type Forced in the Mark box. Click the mark button as the subject inhales as deeply as possible.  After reaching his or maximum inhalation volume, the subject should exhale as quickly and as completely as possible.  Blow out as much as possible.
7. The subject should return to breathing as normally as possible through the spirometer.
8. Click Stop to halt recording.

Data Analysis-Forced Expiration After Exercise

1. Perform the same types of measurements on the data recorded in Activity 1. Record the measurements in the table.

Table 3

Table 4

Figure 7: Lung Volumes for an Average-Sized Human Male (70Kg).

Turn off the IXTA unit when finished, and properly discard all disposable kit items (blue filter, cardboard mouthpiece, and nose clip).