How Do You Calculate Respiratory Rates From Respiratory Flow, CO2, or O2 Traces?

Transcript

hello this is a very quick tutorial just to look at calculating rates respiratory rates from either a respiratory flow trace or from a CO2 or O2 Trace taken from a um a serx here we have uh the incremental exercise protocol and we've been using for other analyses we've got uh flow volume from the respiratory pod we've got CO2 and O2 from serx uh bl... Read More

Key Insights

• Define rate as cyclic measurement: Respiratory rate is not read directly from the displayed flow trace. A new channel must be added, its calculation changed from no calculation to cyclic measurements, and rate chosen as the measurement. This setup turns repeating respiratory peaks into a derived breathing-rate channel that can be inspected alongside the original recordings.
• Choose the intended source trace: The source measurement determines which respiratory signal supplies the detected cycles. The tutorial first uses flow and later changes the same calculation to CO2. It also states that respiratory rates can be calculated from a CO2 or O2 trace taken from the serx, providing alternatives when a respiratory flow trace is not being used.
• Use the respiratory preset: After selecting flow as the source and rate as the measurement, the preset list is scrolled until respiratory air flow appears. The same preset is retained when the source is later changed to CO2. Selecting the preset establishes the peak-based respiratory calculation, but visual confirmation remains necessary before accepting its output.
• Inspect every detected peak: The tutorial zooms into the trace specifically to confirm that the calculation is picking up all peaks. Detection alone does not show whether each peak represents a separate respiratory event. Reviewing the trace connects the software's calculated rate to the recorded waveform and reveals why individual rate values may rise unexpectedly.
• Keep genuine double breaths: A double peak is not automatically an error. In the demonstrated flow trace, the apparent double peak corresponds to a real double breath, so it is left unchanged. This distinction matters because smoothing or adjusting detection simply to remove every double peak could also remove respiratory behavior actually present in the raw recording.
• Explain spikes from raw events: A large respiratory-rate increase is investigated by zooming into the associated section of the flow trace. The subject has taken a quick intake of breath that produces a triple breath, and the software counts it as three breaths. The waveform therefore explains the calculated spike rather than leaving it as an unexplained numerical result.
• Expect natural rate variability: The respiratory-rate channel is described as quite variable rather than stable, and some variation is expected. The displayed spikes must therefore be interpreted by returning to the respiratory trace. Variability itself is not sufficient evidence of a calculation failure, especially when the underlying flow shows closely spaced breaths.
• Select smoothing by purpose: The software provides triangular smoothing, a median filter, and averaging decimation. The tutorial chooses averaging decimation because it bins the data while smoothing the displayed rate. This makes it possible to view respiratory-rate changes over defined periods without replacing the raw respiratory trace used for closer analysis.
• Adjust the bin duration: Averaging decimation is first configured with 5-second bins, with each displayed section representing one 5-second period. The tutorial then considers 10-second bins and uses 30-second bins for visualization. Increasing the period makes the overall increase in respiratory rate across the practical especially clear.
• Treat smoothing as visualization: The smoothed channel is presented as a quick way to eyeball the data, identify changes, and see the expected trend. It is not presented as the preferred source for final averages. The tutorial instead recommends taking binning data and averages from the raw trace, where unusual events can be identified and excluded if necessary.
• Compare independent respiratory traces: Changing the source from flow to end-tidal CO2 produces the same overall rising trend. One description places the increase at about 20 to about 30, while the smoothed comparison is described as moving from around 15 to 20 up to around 30. Agreement is expected because both traces were recorded from the same person at the same time.
• Exclude clearly strange anomalies: The tutorial gives a respiratory-rate change from 20 to 71 breaths as an example that is clearly a mistake. Working from the raw trace allows such strange anomalies to be found and excluded from averages. The binned display helps locate general trends, while raw data supports decisions about questionable individual values.

Questions & Answers

Q: How do you calculate respiratory rates from respiratory traces?

Add a new channel through Setup and Channel Settings, then name it respiratory rate or RR. Open its calculation options, choose cyclic measurements, select the respiratory trace as the source, and set the measurement to rate. Choose the respiratory air flow preset and inspect the waveform to ensure that the software detects the relevant peaks. The resulting derived channel displays breathing rate, while the original trace remains available for checking unusual values.

Q: Can respiratory rate be calculated from flow, CO2, or O2 traces?

Yes, the tutorial describes calculating respiratory rate from a respiratory flow trace or from a CO2 or O2 trace taken from a serx. The worked setup begins with flow as the source measurement. It then changes the source to CO2 and derives rate from the end-tidal CO2 channel. In each case, the detected peaks must be reviewed to confirm that the calculation follows the respiratory cycles.

Q: How should respiratory peak detection be checked?

After choosing the respiratory air flow preset, zoom into the source trace and confirm that the calculation is detecting all peaks. Compare questionable detections with the underlying waveform rather than assuming that every close pair is an error. In the example, a double peak is retained because the trace shows a genuine double breath. This inspection establishes whether unusual calculated rates reflect real breathing events or mistaken detection.

Q: Why can calculated respiratory rate show sudden spikes?

A spike can occur when several breaths or respiratory peaks appear close together and are counted separately. The tutorial investigates a large increase by zooming into the relevant flow section. It finds a triple breath created when the subject takes a quick intake of breath, and the software counts this as three breaths. Looking back at the raw waveform explains the spike and supports a decision about whether it belongs in later analysis.

Q: How does averaging decimation smooth respiratory-rate data?

Create another channel, name it RR flow smooth, and select a smoothing calculation. Choose averaging decimation, set the source to the flow-derived rate, and select a period such as 5 seconds. The software divides the data into consecutive periods and averages respiratory rate within each period. The displayed value jumps between bins when their averages differ, making changes in the rate easier to inspect.

Q: Which respiratory-rate bin sizes are demonstrated?

The first averaging-decimation setup uses 5-second bins, with every displayed bin representing a 5-second period. The tutorial then shows that the smoothing can be changed to 10-second bins. For a broader visualization, it also uses 30-second bins. These longer periods make the overall upward trend during the practical clearer, while the raw trace remains the recommended basis for averages and exclusions.

Q: Should respiratory-rate averages come from smoothed or raw data?

The smoothed, binned channel is useful for a quick visual check of trends and expected changes. The tutorial recommends taking binning data and averages from the raw trace instead. Raw data allows strange anomalies to be inspected and excluded when necessary. A change from 20 to 71 breaths is given as a value that is clearly a mistake, illustrating why the source trace must remain part of the analysis.

Q: Do flow and end-tidal CO2 produce the same respiratory-rate trend?

The two demonstrated analyses produce the same overall trend. The end-tidal CO2 calculation shows respiratory rate increasing from about 20 to about 30 over the practical, and the smoothed comparison rises from around 15 to 20 up to around 30. This agreement is expected because the flow and CO2 traces were recorded from the same person at the same time. Comparing them therefore provides a practical check that both calculations reflect the same changing breathing pattern.

Summary & Key Takeaways

• Preparing the recorded channels: The tutorial uses an incremental exercise protocol containing flow volume from a respiratory pod, CO2 and O2 from a serx, plus blood pressure, heart rate, SpO2, ECG, and saturation measurements. The calculation initially focuses only on respiratory flow. Zooming is unnecessary at this stage because the immediate objective is to add a derived channel that converts the flow trace into breathing rate.

• Creating the respiratory-rate channel: In Setup, Channel Settings, another channel is added and named respiratory rate, or RR. Its calculation is configured as a cyclic measurement, with flow selected as the source and rate selected as the measurement. Decimal places remain at zero, although the stated default is normally four. The respiratory air flow preset is then selected before inspecting peak detection.

• Checking detected respiratory peaks: A closer view confirms whether the calculation detects all relevant peaks. One apparent double peak is retained because it corresponds to an actual double breath. The resulting respiratory-rate channel is variable and contains spikes. Inspection of one large increase reveals a triple breath caused by a quick intake of breath, which the software counts as three breaths and which explains the unusual value.

• Smoothing and viewing trends: A further channel called RR flow smooth is created with a smoothing algorithm. The software offers triangular smoothing, a median filter, and averaging decimation. Averaging decimation is selected with 5-second periods, producing consecutive bins whose values change as their averages change. The bin size can also be changed to 10 or 30 seconds, making the rise in respiratory rate across the practical easier to see.

• Repeating with the CO2 trace: The original derived channel is changed from flow to CO2 while retaining the respiration air flow preset, and its peaks are checked again. The resulting rate, derived from end-tidal CO2, rises from about 20 to about 30 during the practical. Both trace-based analyses show the same trend, as expected for measurements taken from the same person at the same time. Final averages should still be calculated from raw data so anomalies can be excluded.