Ghijselings Idris E, Bockstael Brecht, De Waele Elisabeth, Jonckheer Joop
Department of Intensive Care, University Hospital of Brussels, Brussels, Belgium.
Department of Anesthesia, University Hospital of Brussels, Brussels, Belgium.
Exp Physiol. 2022 May;107(5):424-428. doi: 10.1113/EP090282. Epub 2022 Apr 15.
What is the main observation in this case? Several studies have reported progressive hypoxaemia once extracorporeal carbon dioxide removal is started in patients with hypercapnic respiratory failure, possibly attributable to an altered respiratory quotient. What insights does it reveal? In this quality control report, we show that the respiratory quotient exhibits only minimal alteration when extracorporeal carbon dioxide removal is started and assume that the progressive hypoxaemia is attributable to an increase in intrapulmonary shunt.
The use of extracorporeal carbon dioxide removal (ECCO R) has been proposed in patients with acute respiratory distress syndrome to achieve lung-protective ventilation and in patients with selective hypercapnic respiratory failure. However, several studies have reported progressive hypoxaemia, as expressed by a need to increase the inspired oxygen fraction (F O ) to maintain adequate oxygenation or by a decrease in the ratio of arterial oxygen tension (P O ) to F O once ECCO R is started. We present the case of a patient who was admitted to the intensive care unit for a coronavirus disease 2019 pneumonia and who was intubated because of hypercapnic respiratory insufficiency. Extracorporeal carbon dioxide removal was started, and the patient subsequently developed progressive hypoxaemia. To test whether the hypoxaemia was attributable to the ECCO R, blood samples were taken in different settings: (1) 'no ECCO R', blood flow 150 ml/min with a ECCO R gas flow of 0 L/min; and (2) 'with ECCO R', blood flow 400 ml/min with gas flow 12 L/min. We measured P O , alveolar oxygen tension, P O /F O , alveolar-arterial oxygen tension difference, arterial carbon dioxide tension and the respiratory quotient (RQ) by indirect calorimetry in each setting. The RQ was 0.60 without ECCO R and 0.57 with ECCO R. The alveolar oxygen tension was 220.4 mmHg without ECCO R and increased to 240.3 mmHg with ECCO R, whereas P O /F O decreased from 177 to 171. Our study showed only a minimal change in RQ when ECCO R was started. We were the first to measure the RQ directly, before and after the initiation of ECCO R, in a patient with hypercapnic respiratory failure.
该病例的主要观察结果是什么？多项研究报告称，高碳酸血症性呼吸衰竭患者开始进行体外二氧化碳清除后会出现进行性低氧血症，这可能归因于呼吸商的改变。它揭示了哪些见解？在这份质量控制报告中，我们表明开始体外二氧化碳清除时呼吸商仅出现极小的改变，并认为进行性低氧血症归因于肺内分流增加。
已有人提出在急性呼吸窘迫综合征患者中使用体外二氧化碳清除（ECCO R）以实现肺保护性通气，在选择性高碳酸血症性呼吸衰竭患者中也可使用。然而，多项研究报告称出现了进行性低氧血症，表现为需要增加吸入氧分数（F O ）以维持足够的氧合，或者在开始ECCO R后动脉血氧分压（P O ）与F O 的比值降低。我们报告了一例因2019冠状病毒病肺炎入住重症监护病房且因高碳酸血症性呼吸功能不全而插管的患者。开始进行体外二氧化碳清除后，患者随后出现进行性低氧血症。为了检验低氧血症是否归因于ECCO R，在不同情况下采集了血样：（1）“未进行ECCO R”，血流量150 ml/min，ECCO R气体流量0 L/min；（2）“进行ECCO R”，血流量400 ml/min，气体流量12 L/min。我们在每种情况下通过间接量热法测量了P O 、肺泡氧分压、P O /F O 、肺泡 - 动脉氧分压差、动脉二氧化碳分压和呼吸商（RQ）。未进行ECCO R时RQ为0.60，进行ECCO R时为0.57。未进行ECCO R时肺泡氧分压为220.4 mmHg，进行ECCO R时升至240.3 mmHg，而P O /F O 从177降至171。我们的研究表明开始ECCO R时RQ仅出现极小变化。我们是首个在高碳酸血症性呼吸衰竭患者中在开始ECCO R之前和之后直接测量RQ的。
