key: cord-0735475-k6yh9hh3
authors: Barthélémy, Romain; Beaucoté, Victor; Bordier, Raphaëlle; Collet, Magalie; Le Gall, Arthur; Hong, Alex; de Roquetaillade, Charles; Gayat, Etienne; Mebazaa, Alexandre; Chousterman, Benjamin G.
title: Haemodynamic impact of positive end expiratory pressure in SARS-CoV-2 acute respiratory distress syndrome: oxygenation vs oxygen delivery
date: 2020-11-05
journal: Br J Anaesth
DOI: 10.1016/j.bja.2020.10.026
sha: 05bd1f4974d8d963e52635a5d96098d6727548c2
doc_id: 735475
cord_uid: k6yh9hh3

nan

the pandemic in these patients. 4 COVID-19 ARDS can be associated with an increase in 23 intrapulmonary shunt fraction (Qs/Qt) related to abnormal pulmonary vasodilation and 24 increased perfusion in some lung areas 5 that might be related to endothelial and vascular 25 dysfunction. 6 Thus, although arterial oxygenation may improve through alveolar 26 recruitment, Qs/Qt reduction due to the decrease in cardiac output caused by higher PEEP 7 27 may be another mechanism to consider. Some studies have suggested that haemodynamic 28 deterioration may occur when higher PEEP is used in COVID-19 ARDS, 8 The effects of increasing PEEP levels on respiratory mechanics, oxygenation, haemodynamic 55 status and oxygen delivery are presented in Figure 1 . Increased PEEP was associated with an 56 increase in PaO 2 /FiO 2 (p<0.001) and a decrease in Qs/Qt (p<0.001), without changes in C RS 57 (p=0.192) but with decreases in cardiac output (p=0.003) and DaO 2 (p=0.049). For each cm 58 H 2 O of PEEP increase, PaO 2 /FiO 2 increased by 10 mm Hg (95% CI 8 to 13) and Qs/Qt 59 decreased by −1 % (95% CI −1 to −2), but cardiac output and DaO 2 decreased by −92 mL 60 min −1 (95% CI −152 to −33) and −8.5 mL min −1 (95% CI −17.1 to 0.1), respectively (results for 61 all variables in Supplementary data Table S2 ). In our cohort, 43% of PEEP-trials were 62 associated with a positive response to higher PEEP (10 cm H 2 O) for PaO 2 /FiO 2 . For DaO 2 , the 63 positive response to higher PEEP dropped to 27% (p=0.031). 64

We showed that higher PEEP was associated with an increase in PaO 2 /FiO 2 ratio without 65 improvement in oxygen delivery due to a decrease in cardiac output. When haemodynamic 66 status and oxygen delivery were considered, most patients did not benefit from higher PEEP unlikely to have prevented ventilation-induced lung injury. 69

Higher PaO 2 /FiO 2 ratio associated with higher PEEP does not only rely on alveolar 70 recruitment and improvement of lung mechanics. The correction of the ventilation-perfusion 71 mismatch, which may result partly from reduced Qs/Qt associated with reduced cardiac 72 output, may contribute to the improvement of arterial oxygenation. 7 This observation is in 73 line with a report of high interindividual variability of potential for lung recruitment, 3 and 74 ventilation-perfusion mismatch likely related to blood flow redistribution rather than non-75 ventilated units. 9 The relative contribution of increased pleural pressure and increased 76 transpulmonary pressure with PEEP increase, resulting from decreased right ventricle 77 preload and increased right ventriclar afterload (eventually leading to the decrease in 78 cardiac output) were not specifically evaluated in this study. Their co-existence has been 79 suggested by others as well. 8 80

Even though this is a small study with potential selection bias, our data suggest that 81 interpretation of results of PEEP titration in COVID-19 ARDS should not rely only on 82 PaO 2 /FiO 2 . C RS and cardiac output should be considered simultaneously to identify the 83 patient-centred effect of PEEP level on alveolar recruitment and hemodynamic effect. When 84 hemodynamic effect is preeminent, the apparent increase in PaO 2 /FiO 2 may not be 85 associated with more oxygen delivery to the patient. 86

In COVID-19 ARDS, higher PEEP may lead to a decrease in cardiac output without increases 87 in DaO 2 despite an increase in PaO 2 /FiO 2 . Higher PEEP could be unbeneficial to a significant 88 proportion of patients. These results require a cautious and multimodal approach including 89 cardiac output monitoring when using higher PEEP. PaO 2 /FiO 2 : arterial oxygen partial pressure (PaO 2 ) to fraction of inspired oxygen (FiO 2 ) ratio with FiO 2 =1, C RS : respiratory system compliance, Qs/Qt: intrapulmonary shunt, DaO 2 : arterial oxygen delivery. The values are presented in Supplementary data (Table S1 ).

J o u r n a l P r e -p r o o f

Formal guidelines: management of acute 105 respiratory distress syndrome

Hypoxaemia related to COVID-19: vascular and 116 perfusion abnormalities on dual-energy CT

Endothelial cell infection and endotheliitis in 119 COVID-19

Optimum end-expiratory airway pressure in 121 patients with acute pulmonary failure

The ARDSnet protocol may be detrimental in 123 COVID-19

Potential for Lung Recruitment and Ventilation-125

Perfusion Mismatch in Patients With the Acute Respiratory Distress Syndrome From 126

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