Figure 1.

The size of the pathway for breathing is visualized for both calorimeters, Oxycon on the left, Omnical on the right. The Oxycon triple‐V sensor has an inner diameter of 2.6 cm, an in‐line sputum catcher (metal mesh), and an in‐line turbine behind the sputum catcher. It is estimated to provide 400 mm² surface for breathing flow. The Omnical has an open pathway with an inner diameter of 3.5 cm, and it provides ±960 mm² surface for breathing flow. Both use common industry face mask or mouthpiece with nose‐clip