Hemodynamic Effects of Awake Prone Positioning With COVID-19 Acute Respiratory Failure.

INTRODUCTION: Awake prone positioning (PP) reduces need for intubation for patients with COVID-19 with acute respiratory failure. We investigated the hemodynamic effects of awake PP in non-ventilated subjects with COVID-19 acute respiratory failure. METHODS: We conducted a single-center prospective cohort study. Adult hypoxemic subjects with COVID-19 not requiring invasive mechanical ventilation receiving at least one PP session were included. Hemodynamic assessment was done with transthoracic echocardiography before, during, and after a PP session. RESULTS: Twenty-six subjects were included. We observed a significant and reversible increase in cardiac index (CI) during PP compared to supine position (SP): 3.0 ± 0.8 L/min/m2 in PP, 2.5 ± 0.6 L/min/m2 before PP (SP1), and 2.6 ± 0.5 L/min/m2 after PP (SP2, P < .001). A significant improvement in right ventricular (RV) systolic function was also evidenced during PP: The RV fractional area change was 36 ± 10% in SP1, 46 ± 10% during PP, and 35 ± 8% in SP2 (P < .001). There was no significant difference in PaO2 /FIO2 and breathing frequency. CONCLUSION: CI and RV systolic function are improved by awake PP in non-ventilated subjects with COVID-19 with acute respiratory failure.

ARNI Pre-Operative Use and Vasoplegic Syndrome in Patients Undergoing Heart Transplantation or Left Ventricular Assist Device Surgery.

Background: Vasoplegic syndrome after orthotopic heart transplantation (OHT) or left ventricular assist device (LVAD) implantation is a rare but highly lethal syndrome with complex etiologies. The objective of this study was to assess if the preoperative use of sacubitril-valsartan combination is associated with an increased vasoplegic syndrome (VS) frequency after OHT or LVAD implantation and its relationship with 30-day mortality. Methods: A retrospective review of perioperative data, between January 2016 and December 2017, from 73 consecutive OHT and LVAD surgery adult patients at our institution was performed. VS was defined as normal cardiac output with persistent low systemic resistance requiring a norepinephrine intravenous perfusion > 0.5 µg/kg/min and the absence of sepsis or hemorrhagic shock within 48 h after surgery. Patients were all followed-up for adverse events and all-cause mortality at 30 days. Results: In our cohort of 73 patients (median age 51.7 years, 65% male patients), 25 (34%) patients developed VS. Twenty-two (30.1%) patients were on ARNI at the time of surgery, 31 (42.5%) were on other RAS blockers, 12 (16.4%) were on norepinephrine and 8 (11%) had no pre-operative drug. The pre-operative use of any vasoactive agent, was not significantly associated with VS (OR = 1.36; IC95% [0.78; 2.35]; p = 0.38). The pre-operative use of an ARNI compared to all other groups was not significantly associated with VS (OR = 2.0; IC95% [0.71; 5.62]; p = 0.19). The pre-operative use of an ARNI compared to other RAS blockers was also not significantly associated with VS (OR = 1.25; IC95% [0.37; 4.26]; p = 0.72). At 30 days, 18 (24.7%) patients had died. The pre-operative treatment with ARNI, or other RAS inhibitors was associated with a significantly lower rate of death compared to the absence of treatment (HR = 0.11; IC95% [0.02; 0.55]; p = 0.009 for ARNI and HR = 0.20; IC95% [0.06; 0.69]; p = 0.011 for other RASi). Conclusions: Preoperative use of sacubitril-valsartan was not significantly associated with development of vasoplegic syndrome in patients undergoing OHT or LVAD surgery. Furthermore, our data suggests a significant 30-day survival benefit with efficient renin-angiotensin blockade before surgery.

A Comprehensive Bench Assessment of Automatic Tube Compensation in ICU Ventilators for Better Clinical Management.

BACKGROUND: Automatic tube compensation (ATC) unloads endotracheal tube (ETT) resistance. We conducted a bench assessment of ATC functionality in ICU ventilators to improve clinical management. METHODS: This study had 2 phases. First, we performed an international survey on the use of ATC in clinical practice, hypothesizing a rate of ATC use of 25%. Second, we tested 7 modern ICU ventilators in a lung model mimicking a normal subject (Normal), a subject with ARDS, and a subject with COPD. Inspiratory effort consisted of esophageal pressure over 30 consecutive breaths obtained in a real patient under weaning. A brand new 8-mm inner diameter ETT was attached to the lung model, and ATC was set at 100% compensation for the ETT. The 30 breaths were first run with ATC off and no ETT (ie, reference period), and then with ATC on and ETT (ie, active period). The primary end point was the difference in tidal volume (VT) between reference and active periods. We hypothesized that the VT difference should be equal to 0 in an ideally functioning ATC. VT difference was compared across ventilators and respiratory mechanics conditions using a linear mixed-effects model. RESULTS: The clinical use of ATC was 64% according to 644 individuals who responded to the international survey. The VT difference varied significantly across ventilators in all respiratory mechanics configurations. The divergence between VT difference and 0 was small but significant: the extreme median (interquartile range) values were -0.013 L (-0.019 to -0.002) in the COPD model and 0.056 L (0.051-0.06) in the Normal model. VT difference for all ventilators was 0.015 L (95% CI 0.013-0.018) in the ARDS model, which was significantly different from 0.021 L (95% CI 0.018-0.024) in the Normal model (P < .001) and 0.010 L (0.007-0.012) in the COPD model (P = .003). CONCLUSIONS: ATC is used more frequently in clinical practice than expected. In addition, VT delivery by ATC differed slightly though significantly between ventilators.

Hemodynamic effects of extended prone position sessions in ARDS.

BACKGROUND: Hemodynamic response to prone position (PP) has never been studied in a large series of patients with acute respiratory distress syndrome (ARDS). The primary aim of this study was to estimate the rate of PP sessions associated with cardiac index improvement. Secondary objective was to describe hemodynamic response to PP and during the shift from PP to supine position. METHODS: The study was a single-center retrospective observational study, performed on ARDS patients, undergoing at least one PP session under monitoring by transpulmonary thermodilution. PP sessions performed more than 10 days after ARDS onset, or with any missing cardiac index measurements before (T1), at the end (T3), and after the PP session (T4) were excluded. Changes in hemodynamic parameters during PP were tested after statistical adjustment for volume of fluid challenges, vasopressor and dobutamine dose at each time point to take into account therapeutic changes during PP sessions. RESULTS: In total, 107 patients fulfilled the inclusion criteria, totalizing 197 PP sessions. Changes in cardiac index between T1 and T2 (early response to PP) and between T1 and T3 (late response to PP) were significantly correlated (R2 = 0.42, p < 0.001) with a concordance rate amounting to 85%. Cardiac index increased significantly between T1 and T3 in 49 sessions (25% [95% confidence interval (CI95%) 18-32%]), decreased significantly in 46 (23% [CI95% 16-31%]), and remained stable in 102 (52% [CI95% 45-59%]). Global end-diastolic volume index (GEDVI) increased slightly but significantly from 719 ± 193 mL m-2 at T1 to 757 ± 209 mL m-2 at T3 and returned to baseline values at T4. Cardiac index and oxygen delivery decreased slightly but significantly from T3 to T4, without detectable increase in lactate level. Patients who increased their cardiac index during PP had significantly lower CI, GEDVI, global ejection fraction at T1, and received significantly more fluids than patients who did not. CONCLUSION: PP is associated with an increase in cardiac index in 18% to 32% of all PP sessions and a sustained increase in GEDVI reversible after return to supine position. Return from prone to supine position is associated with a slight hemodynamic impairment.

Effects of positive end-expiratory pressure strategy in supine and prone position on lung and chest wall mechanics in acute respiratory distress syndrome.

BACKGROUND: In acute respiratory distress syndrome (ARDS) patients, it has recently been proposed to set positive end-expiratory pressure (PEEP) by targeting end-expiratory transpulmonary pressure. This approach, which relies on the measurement of absolute esophageal pressure (Pes), has been used in supine position (SP) and has not been investigated in prone position (PP). Our purposes were to assess Pes-guided strategy to set PEEP in SP and in PP as compared with a PEEP/FIO2 table and to explore the early (1 h) and late (16 h) effects of PP on lung and chest wall mechanics. RESULTS: We performed a prospective, physiologic study in two ICUs in university hospitals on ARDS patients with PaO2/FIO2 < 150 mmHg. End-expiratory Pes (Pes,ee) was measured in static (zero flow) condition. Patients received PEEP set according to a PEEP/FIO2 table then according to the Pes-guided strategy targeting a positive (3 ± 2 cmH2O) static end-expiratory transpulmonary pressure in SP. Then, patients were turned to PP and received same amount of PEEP from PEEP/FIO2 table then Pes-guided strategy. Respiratory mechanics, oxygenation and end-expiratory lung volume (EELV) were measured after 1 h of each PEEP in each position. For the rest of the 16-h PP session, patients were randomly allocated to either PEEP strategy with measurements done at the end. Thirty-eight ARDS patients (27 male), mean ± SD age 63 ± 13 years, were included. There were 33 primary ARDS and 26 moderate ARDS. PaO2/FIO2 ratio was 120 ± 23 mmHg. At same PEEP/FIO2 table-related PEEP, Pes,ee averaged 9 ± 4 cmH2O in both SP and PP (P = 0.88). With PEEP/FIO2 table and Pes-guided strategy, PEEP was 10 ± 2 versus 12 ± 4 cmH2O in SP and 10 ± 2 versus 12 ± 5 cmH2O in PP (PEEP strategy effect P = 0.05, position effect P = 0.96, interaction P = 0.96). With the Pes-guided strategy, chest wall elastance increased regardless of position. Lung elastance and transpulmonary driving pressure decreased in PP, with no effect of PEEP strategy. Both PP and Pes-guided strategy improved oxygenation without interaction. EELV did not change with PEEP strategy. At the end of PP session, respiratory mechanics did not vary but EELV and PaO2/FIO2 increased while PaCO2 decreased. CONCLUSIONS: There was no impact of PP on Pes measurements. PP had an immediate improvement effect on lung mechanics and a late lung recruitment effect independent of PEEP strategy.

Change in cardiac output during Trendelenburg maneuver is a reliable predictor of fluid responsiveness in patients with acute respiratory distress syndrome in the prone position under protective ventilation.

BACKGROUND: Predicting fluid responsiveness may help to avoid unnecessary fluid administration during acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate the diagnostic performance of the following methods to predict fluid responsiveness in ARDS patients under protective ventilation in the prone position: cardiac index variation during a Trendelenburg maneuver, cardiac index variation during an end-expiratory occlusion test, and both pulse pressure variation and change in pulse pressure variation from baseline during a tidal volume challenge by increasing tidal volume (VT) to 8 ml.kg-1. METHODS: This study is a prospective single-center study, performed in a medical intensive care unit, on ARDS patients with acute circulatory failure in the prone position. Patients were studied at baseline, during a 1-min shift to the Trendelenburg position, during a 15-s end-expiratory occlusion, during a 1-min increase in VT to 8 ml.kg-1, and after fluid administration. Fluid responsiveness was deemed present if cardiac index assessed by transpulmonary thermodilution increased by at least 15% after fluid administration. RESULTS: There were 33 patients included, among whom 14 (42%) exhibited cardiac arrhythmia at baseline and 15 (45%) were deemed fluid-responsive. The area under the receiver operating characteristic (ROC) curve of the pulse contour-derived cardiac index change during the Trendelenburg maneuver and the end-expiratory occlusion test were 0.90 (95% CI, 0.80-1.00) and 0.65 (95% CI, 0.46-0.84), respectively. An increase in cardiac index ≥ 8% during the Trendelenburg maneuver enabled diagnosis of fluid responsiveness with sensitivity of 87% (95% CI, 67-100), and specificity of 89% (95% CI, 72-100). The area under the ROC curve of pulse pressure variation and change in pulse pressure variation during the tidal volume challenge were 0.52 (95% CI, 0.24-0.80) and 0.59 (95% CI, 0.31-0.88), respectively. CONCLUSIONS: Change in cardiac index during a Trendelenburg maneuver is a reliable test to predict fluid responsiveness in ARDS patients in the prone position, while neither change in cardiac index during end-expiratory occlusion, nor pulse pressure variation during a VT challenge reached acceptable predictive performance to predict fluid responsiveness in this setting. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01965574 . Registered on 16 October 2013. The trial was registered 6 days after inclusion of the first patient.