Pulmonary Function

The Q-CPX system with ComPAS software allows for full cardio-pulmonary testing complete with dynamic and static spirometry that may be measured before, during and after CPX tests.

Flow-Volume Loops

Flow volume loops are perhaps the most recognizable of all pulmonary function tests. The shape of the curves are extremely diagnostic but the very nature of the effort required to reproduce the shape (loop) means that often data are of a poor quality. In ComPAS software we have gone to extraordinary lengths to help the technician acquire high quality clinical data. Each of the test efforts is automatically reviewed against ATS standards and a “confidence” rating is also applied by an even stricter performance

Mini Results Test Screen


The “Mini Results” test screen provides key summary information on the test in progress. If you wish you see more detail of the results a variety of screens are available.  Along the top of the “Mini Results” page are a group of tabs that provide helpful review options:

Single Test

ATS Review

Volume Time

The default position for the tabs displays the current highlighted test effort.The Flow Volume Loop selected is drawn compared to predicted values.  A larger display of the data is available under the Flow Volume tab.

Details the clinical review of the highlighted individual test effort and compares it to other efforts completed. Effort Acceptability dteects potential artefacts.  Reproducibility ensures that repeated efforts fall within accepted ATS guidelines.

Displays a large Volume-Time graphic  with each effort overlaid.  Reveals which efforts should be kept and which should be discarded.  The selected effort is shown as a bolder line on the overlaid tests screen.

Overlay Best

View All

Overlays the best Pre and Post Flow Volume Loops (i.e. those currently selected to go to the final report).  Report Graphs overlays selected PRE and POST loops.  Selected Efforts allows you to check those loops you wish to overlay.

Displays a miniature graph of each Flow Volume Loop completed.  Useful for making selections of graphics (complete loops, inspired or expired choices). All of the right-click functions available on the spreadsheet also operate clicking a graph.

Reviewing Flow Volume Spreadsheets

Although the ‘Mini Results” screen can provide essential information when performing tests, spreadsheets within ComPAS software provide numerical data in greater depth.  Scroll bars can be clicked, held and dragged up and down or  up and down arrows may be used to navigate the spreadsheets.

A Details View shows key information together with the volume time graphic and percent best for any effort selected.  A Full Spreadsheet View displays all parameters stored in the database for the test type selected (FVC, SVC, MVV etc.).

Maximum Voluntary Ventilation (MVV)

MVV is the volume of gas that can be breathed during a 15 second period when a person breathes as deeply and quickly as possible. In older journals and publications, MVV is also called maximum breathing capacity. The result is extrapolated from 15 seconds to show what could be achieved over a one minute period. As a general guide, the value should correlate closely to the FEV1 x 35.

This test is usually performed whenever spirometry is done. It identifies weakness in the muscles used for breathing.  In exercise testing, the MVV is used in the calculation of Breathing Reserve.

The run-time screen displays target lines at 6, 12 and 15 seconds. The patient MUST reach the 6-second mark and it is preferable to encourage them to the full 15 seconds.  If the patient reaches 15 seconds, the test will automatically end. If  the [Spacebar] is pressed at any time after six seconds test duration, the result are calculated and stored, but will not, of course, pass the ATS recommended criteria.

The values shown for FEV1 x 35 and FEV1 x 40 are very good guides of what to expect from a good patient effort. They will only be displayed if you have completed a flow volume loop prior to doing the MVV test.  A genuine effort should get very close to the FEV1 x 35 or exceed it.

The MVV result is automatically processed to obtain the greatest value across the panting effort. At the same time, each test effort is evaluated and given a “confidence” rating. By clicking Adjust MVV it is possible to review which segment of the effort was evaluated to calculate the result and view a detailed evaluation.

By clicking on either the starting or ending markers these can be dragged to include or exclude different segments of the test. Once released, the MVV is recalculated. Since the evaluation utilizes the Tidal Volume (TV), Breathing Frequency (F) and Tidal Volume/Vital Capacity ratio (TV/VC), each of these values are recalculated any time an adjustment is made.

To return to the original computer assessment of the MVV, the Revert MVV button is clicked.

As for flow volume loops, the operator may manually override the automatic selection of reported MVV results.  Both the data and the graphic can be selected using the right-click options on the mini-results screen.

Meaurements FVC and IC During Exercise

For users wanting to evaluate ventilatory responses to exercise, the ability to perform either a maximal Forced Vital Capacity (FVC) or just an Inspiratory Capacity (IC) is provided.  The baseline flow volume loop taken from the separate FVC test is shown including the position and size of the tidal volume.

During any stage of the exercise test, subsequent FVC or IC efforts along with the tidal volumes can be recorded by clicking the Perform FVC button.

TLC is recognized as the most reproducible measures of lung volume; it is a natural feeling for subjects to “breathe right-in” and fill their lungs.  For this reason performing an IC during exercise provides a reliable ‘anchor point’ to record the true position of tidal volume.  At the conclusion of the test the user can select which efforts and views to record and send to the final report.