• Tomas Öhman, JaldeFrancesca CampocciaFCDepartment of Thoracic Anesthesiology, Surgical Services and Intensive Care, Karolinska University Hospital, Stockholm, Sweden.Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden., Magnus Fredby, Håkan Björne, and Jacob Karlsson.
• Department of Perioperative Medicine and Intensive Care, Karolinska University Hospital, Stockholm, Sweden.
• Acta Anaesthesiol Scand. 2023 Aug 1; 67 (7): 936942936-942.

BackgroundPatients with Covid-19 respiratory failure present with hypoxemia, often in combination with hypercapnia. In this prospective, observational study we examined the effect of removing external dead space (DS) on CO2 -homeostasis in mechanically ventilated Covid-19 patients. In addition, volumetric capnography was validated for its ability to estimate external DS volume using in vitro measured DS volumes as reference.MethodsIn total, 10 patients with acute respiratory distress syndrome from Covid-19 were included. Volumetric capnography, mechanical ventilation, and arterial blood gas data were analyzed before and after removal of external DS and analyzed for potentially significant changes in response to DS removal. Measurements of external DS were obtained in circuit using volumetric capnography and compared to actual measured DS volumes off the circuit.ResultsAfter the removal of external DS, the alveolar minute ventilation and CO2 elimination improved, notwithstanding unchanged respiratory rate and tidal volumes. The increase in CO2 elimination was associated with a decrease in arterial CO2 partial pressure (PaCO2 ). The volumetric capnography method for assessment of external DS showed a low bias of -9 mL (lower limit of agreement -40, 95% CI -60 to -20 mL, upper limit of agreement 21 mL, 95% CI: 1-40 mL) and a percentage error of 48% compared to absolute values measured in vitro.ConclusionRemoval of external DS increased alveolar minute ventilation and CO2 elimination in Covid-19 patients with respiratory failure in the current study. This was associated with a decrease in PaCO2 . This may indicate a decreased CO2 production due to decreased work of breathing and more effective gas-exchange in response to DS removal. In addition, volumetric capnography appears to be a clinically feasible method for continuous measurement of external DS in the current study and may be of value in optimizing ventilator treatment.© 2023 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.

20 keywords...

hide…