This results in deoxygenated blood being sent into the systemic circulation, which can lead to hypoxemia, a condition where your body or a region of your body is deprived of adequate oxygen supply. This can occur due to various reasons, such as when blood vessels bypass the lung tissue (anatomical shunt), or when parts of the lungs are perfused, but not ventilated, leading to a lack of gas exchange (physiological shunt). Conclusions Monitoring of dead space was useful for detecting lung collapse and for establishing open-lung PEEP after a recruitment maneuver.A shunt refers to a condition where blood passes from the right side to the left side of the heart without being oxygenated in the lungs. The receiver operating characteristics curve demonstrated a high specificity and sensitivity of VDalv (0.89 and 0.90), VDalv/VTalv (0.82 and 1.00), and Pa − etCO2 (0.93 and 0.95) for detecting lung collapse. Measurements and results Alveolar dead space (VDalv), the ratio of alveolar dead space to alveolar tidal volume (VDalv/VTalv), and the arterial to end-tidal PCO2 difference (Pa-etCO2) showed a good correlation with PaO2, normally aerated areas, and non-aerated CT areas in all animals (minimum–maximum r2 = 0.83–0.99 p 5%) started at 12 cmH2O PEEP hence, open-lung PEEP was established at 14 cmH2O. Each PEEP step was maintained for 10 min. PEEP was decreased from 24 to 6 cmH2O in steps of 2 cmH2O and then to 0 cmH2O. Recruitment maneuver was achieved within 2 min at pressure levels of 60/30 cmH2O for Peak/PEEP. PEEP was increased in steps of 6 cmH2O from 6 to 24 cmH2O.

Baseline measurements were performed at 6 cmH2O of PEEP. Interventions Animals were ventilated using constant flow mode with VT of 6 ml/kg, respiratory rate of 30 bpm, inspiratory-to-expiratory ratio of 1 : 2, and FiO2 of 1. Setting Department of Clinical Physiology, University of Uppsala, Sweden. Objective To test the usefulness of dead space for determining open-lung PEEP, the lowest PEEP that prevents lung collapse after a lung recruitment maneuver.

Dead space vs shunt