Department of Perioperative Medicine and Intensive Care, Karolinska University Hospital, Stockholm, Sweden.
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Acta Anaesthesiol Scand. 2023 Aug;67(7):936-942. doi: 10.1111/aas.14252. Epub 2023 Jun 24.
Patients 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 CO -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.
In 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.
After the removal of external DS, the alveolar minute ventilation and CO elimination improved, notwithstanding unchanged respiratory rate and tidal volumes. The increase in CO elimination was associated with a decrease in arterial CO partial pressure (PaCO ) 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.
Removal of external DS increased alveolar minute ventilation and CO elimination in Covid-19 patients with respiratory failure in the current study. This was associated with a decrease in PaCO . This may indicate a decreased CO 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.
患有新冠病毒呼吸衰竭的患者表现为低氧血症，常伴有高碳酸血症。在这项前瞻性观察研究中，我们研究了清除机械通气新冠患者的外部死腔 (DS) 对 CO 稳态的影响。此外，使用体外测量的 DS 体积作为参考，验证了容积二氧化碳描记法测量外部 DS 体积的能力。
共纳入 10 例新冠病毒所致急性呼吸窘迫综合征患者。在清除外部 DS 前后分析容积二氧化碳描记法、机械通气和动脉血气数据，并分析 DS 清除后潜在的显著变化。使用容积二氧化碳描记法在回路中测量外部 DS，并与回路外实际测量的 DS 体积进行比较。
在清除外部 DS 后，尽管呼吸频率和潮气量不变，但肺泡分钟通气量和 CO 清除量增加。CO 清除量的增加与动脉 CO 分压 (PaCO ) 降低有关。评估外部 DS 的容积二氧化碳描记法显示出较低的偏差（-9 毫升，下界限为-40，95%可信区间-60 至-20 毫升，上界限为 21 毫升，95%可信区间：1-40 毫升）和与体外绝对值相比的 48%的百分比误差。
在当前研究中，清除外部 DS 增加了新冠病毒呼吸衰竭患者的肺泡分钟通气量和 CO 清除量。这与 PaCO 的降低有关。这可能表明由于呼吸功降低和 DS 清除后更有效的气体交换，CO 生成减少。此外，在当前研究中，容积二氧化碳描记法似乎是一种连续测量外部 DS 的可行临床方法，可能有助于优化呼吸机治疗。
