Waveform Self-Assessment
How would your own capnography change if you intentionally started to breath at a rate of 30 breaths per minute. What would the capnography frequency look like? How long of an alveolar plateau would there be? What height would you expect to see and what would the shape be?
Consider the following:
- Frequency
- Duration
- Height
- Shape
Review a normal waveform for reference: Respiratory rate 12-20 breaths per minute; EtCO₂ 35-45 mmHg.
If you intentionally increased your breathing rate to 30 breaths per minute, your capnography waveform
Frequency Increases: The waveforms appear more often on the screen, reflecting more breaths per minute.
Duration Decreases: Each individual waveform becomes narrower (shorter time between start and end of a breath).
Height: May decrease: Reduced exhalation time can result in lower end-tidal CO₂ (EtCO₂) values due to less complete exhalation.
Shape: May appear more “clipped” or slanted. If exhalation is too brief, Phase III (alveolar plateau) may not fully form, leading to a sloped or truncated waveform.
These changes are characteristic of hyperventilation, often showing a quicker, shallower, and lower waveform pattern as shown in Figure 2.
Figure 2. Hyperventilation (Hypocapnia < 35 mmHg)
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