Figure 3.

Inspiratory and endtidal pCO₂ concentrations. (A-B) Course of the inspiratory and endtidal pCO₂ using the experimental setting described in Figure 2. The gas flow was started after 50 seconds and continued for 60 seconds. The experiment was repeated with two different respiratory rates and tidal volumes: (A) 30/min | 90 ml (corresponding to 2-year-old child) and (B) 40/min | 65 ml (corresponding to a 9-months-old infant). In both cases we observed an increase of the inspiratory pCO₂ by a maximum of ≈20 mmHg. (C-D)In vivo respiration of 6 liter CO₂ over 3 minutes: the gas flow was again started at 50 seconds. The panels depict two different experimental conditions: (C) The test person tried to maintain a respiratory rate of 40/min in synchrony with a metronome over the entire period. Under these conditions the endtidal pCO₂ rose by 7 mmHg. In setting (D) the test person had hyperventilated before the start of the gas flow. Starting from a lower pCO₂ of 17 mmHg, the pCO₂ again rose by 7 mmHg.