Figure 2

Functional algorithm of the ventilation and oxygen controller. (A) Ventilation controller. The partial pressure in end-tidal CO₂ (PEtCO₂) values are given with the quality index and derived from the mainstream CO₂ sensor with proprietary algorithms as a surrogate of arterial partial pressure of CO₂. PEtCO₂min and PEtCO₂max are adjustable by the user and depend on the patient's severity estimated by the level of inspiratory pressure; that is, the higher the inspiratory pressure and the more permissive the PEtCO₂ limits. As an example and by default for an inspiratory pressure of 10 cmH₂O, PEtCO₂min is 35 mmHg and PEtCO₂max is 41 mmHg. (B) Oxygen controller. The oxygen saturation from pulse oxymetry (SpO₂) limits (SpO₂safety and SpO₂min) are adjustable by the user and depending on the patient's severity estimated by the positive end-expiratory pressure (PEEP) level; that is, the higher the PEEP level and the more permissive the SpO₂ limits. As an example and by default for a PEEP level of 5 cmH₂O, SpO₂safety is 88%, SpO₂min is 93% and SPO₂max is 98%. The PEEPopt is defined according to a PEEP-fraction of inspired oxygen (FiO₂) table and PEEPmax set by the user. The patient SpO₂ is provided with a quality index and is derived from the pulse oxymeter with proprietary algorithms for artefact and motion rejections. MV, minute ventilation; RR, respiratory rate.