Venoarterial Extracorporeal Membrane Oxygenation in High-Risk Pulmonary Embolism: A Case Series and Literature Review.

Background: High-risk Pulmonary Embolism (PE) has an ominous prognosis and requires emergent reperfusion therapy, primarily systemic thrombolysis (ST). In deteriorating patients or with contraindications to ST, Veno-Arterial Extracorporeal Membrane Oxygenation (VA-ECMO) may be life-saving, as supported by several retrospective studies. However, due to the heterogeneous clinical presentation (refractory shock, resuscitated cardiac arrest (CA) or refractory CA), the real impact of VA-ECMO in high-risk PE remains to be fully determined. In this study, we present our centre experience with VA-ECMO for high-risk PE. Method: From 2008 to 2020, we analyzed all consecutive patients treated with VA-ECMO for high-risk PE in our tertiary 35-bed intensive care unit (ICU). Demographic variables, types of reperfusion therapies, indications for VA-ECMO (refractory shock or refractory CA requiring extra-corporeal cardiopulmonary resuscitation, ECPR), hemodynamic variables, initial arterial blood lactate and ICU complications were recorded. The primary outcome was ICU survival, and secondary outcome was hospital survival. Results: Our cohort included 18 patients (9F/9M, median age 57 years old). VA-ECMO was indicated for refractory shock in 7 patients (2 primary and 5 following resuscitated CA) and for refractory CA in 11 patients. Eight patients received anticoagulation only, 9 received ST, and 4 underwent surgical embolectomy. ICU survival was 1/11 (9%) for ECPR vs 3/7 (42%) in patients with refractory shock (p = 0.03, log-rank test). Hospital survival was 0/11 (0%) for ECPR vs 3/7 for refractory shock (p = 0.01, log-rank test). Survivors and Non-survivors had comparable demographic and hemodynamic variables, pulmonary obstruction index, and amounts of administered vasoactive drugs. Pre-ECMO lactate was significantly higher in non-survivors. Massive bleeding was the most frequent complication in survivors and non-survivors, and was the direct cause of death in 3 patients, all treated with ST. Conclusions: VA-ECMO for high-risk PE has very different outcomes depending on the clinical context. Furthermore, VA-ECMO was associated with significant bleeding complications, with more severe consequences following systemic thrombolysis. Future studies on VA-ECMO for high-risk PE should therefore take into account the distinct clinical presentations and should determine the best strategy for reperfusion in such circumstances.

Physiological response to prone positioning in intubated adults with COVID-19 acute respiratory distress syndrome: a retrospective study.

BACKGROUND: COVID-19 related acute respiratory distress syndrome (ARDS) has specific characteristics compared to ARDS in other populations. Proning is recommended by analogy with other forms of ARDS, but few data are available regarding its physiological effects in this population. This study aimed to assess the effects of proning on oxygenation parameters (PaO2/FiO2 and alveolo-arterial gradient (Aa-gradient)), blood gas analysis, ventilatory ratio (VR), respiratory system compliance (CRS) and estimated dead space fraction (VD/VT HB). We also looked for variables associated with treatment failure. METHODS: Retrospective monocentric study of intubated COVID-19 ARDS patients managed with an early intubation, low to moderate positive end-expiratory pressure and early proning strategy hospitalized from March 6 to April 30 2020. Blood gas analysis, PaO2/FiO2, Aa-gradient, VR, CRS and VD/VT HB were compared before and at the end of each proning session with paired t-tests or Wilcoxon tests (p < 0.05 considered as significant). Proportions were assessed using Fischer exact test or Chi square test. RESULTS: Forty-two patients were included for a total of 191 proning sessions, median duration of 16 (5-36) hours. Considering all sessions, PaO2/FiO2 increased (180 [148-210] vs 107 [90-129] mmHg, p < 0.001) and Aa-gradient decreased (127 [92-176] vs 275 [211-334] mmHg, p < 0.001) with proning. CRS (36.2 [30.0-41.8] vs 32.2 [27.5-40.9] ml/cmH2O, p = 0.003), VR (2.4 [2.0-2.9] vs 2.3 [1.9-2.8], p = 0.028) and VD/VT HB (0.72 [0.67-0.76] vs 0.71 [0.65-0.76], p = 0.022) slightly increased. Considering the first proning session, PaO2/FiO2 increased (186 [165-215] vs 104 [94-126] mmHg, p < 0.001) and Aa-gradient decreased (121 [89-160] vs 276 [238-321] mmHg, p < 0.001), while CRS, VR and VD/VT HB were unchanged. Similar variations were observed during the subsequent proning sessions. Among the patients who experienced treatment failure (defined as ICU death or need for extracorporeal membrane oxygenation), fewer expressed a positive response in terms of oxygenation (defined as increase of more than 20% in PaO2/FiO2) to the first proning (67 vs 97%, p = 0.020). CONCLUSION: Proning in COVID-19 ARDS intubated patients led to an increase in PaO2/FiO2 and a decrease in Aa-gradient if we consider all the sessions together, the first one or the 4 subsequent sessions independently. When considering all sessions, CRS increased and VR and VD/VT HB only slightly increased.

[Classic ventilatory modes for invasive mechanical ventilation]. / Modes ventilatoires de base en ventilation mécanique invasive.

Invasive mechanical ventilation is part of the daily practice of the intensivist and anesthetist. The comprehensive knowledge of ventilatory modes is mandatory for managing the ventilated patients. The objective of this article is to explain the characteristics of the barometric and volumetric modes and the differences between controlled, assist-controlled, and assisted ventilation. The most common modes (volume and pressure assist-control, dual modes and pressure support) are described in detail. Parameters that must be set and those that must be monitored in each mode are also described. Finally, suggestions for initial settings are provided in order to offer the reader unfamiliar with mechanical ventilation a practical decision-making aid.

La ventilation mécanique invasive est un outil indispensable à la pratique de l'intensiviste et de l'anesthésiste. La connaissance des modes ventilatoires est nécessaire pour la prise en charge des patients ventilés. L'objectif de cet article est, d'une part, de distinguer les caractéristiques des modes barométriques et volumétriques, et de comprendre les différences entre les modes contrôlé, assisté-contrôlé et assisté et, d'autre part, de distinguer les paramètres qui doivent être réglés de ceux qui doivent être monitorés. Les modes les plus utilisés (volume contrôlé, pression contrôlée, modes mixtes et aide inspiratoire) font l'objet d'une description détaillée. Des suggestions de réglages initiaux sont proposées pour ces modes afin d'offrir au lecteur peu familier avec la ventilation mécanique une aide décisionnelle pratique.

Assisted mechanical ventilation promotes recovery of diaphragmatic thickness in critically ill patients: a prospective observational study.

BACKGROUND: Diaphragm atrophy and dysfunction are consequences of mechanical ventilation and are determinants of clinical outcomes. We hypothesize that partial preservation of diaphragm function, such as during assisted modes of ventilation, will restore diaphragm thickness. We also aim to correlate the changes in diaphragm thickness and function to outcomes and clinical factors. METHODS: This is a prospective, multicentre, observational study. Patients mechanically ventilated for more than 48 h in controlled mode and eventually switched to assisted ventilation were enrolled. Diaphragm ultrasound and clinical data collection were performed every 48 h until discharge or death. A threshold of 10% was used to define thinning during controlled and recovery of thickness during assisted ventilation. Patients were also classified based on the level of diaphragm activity during assisted ventilation. We evaluated the association between changes in diaphragm thickness and activity and clinical outcomes and data, such as ventilation parameters. RESULTS: Sixty-two patients ventilated in controlled mode and then switched to the assisted mode of ventilation were enrolled. Diaphragm thickness significantly decreased during controlled ventilation (1.84 ± 0.44 to 1.49 ± 0.37 mm, p < 0.001) and was partially restored during assisted ventilation (1.49 ± 0.37 to 1.75 ± 0.43 mm, p < 0.001). A diaphragm thinning of more than 10% was associated with longer duration of controlled ventilation (10 [5, 15] versus 5 [4, 8.5] days, p = 0.004) and higher PEEP levels (12.6 ± 4 versus 10.4 ± 4 cmH2O, p = 0.034). An increase in diaphragm thickness of more than 10% during assisted ventilation was not associated with any clinical outcome but with lower respiratory rate (16.7 ± 3.2 versus 19.2 ± 4 bpm, p = 0.019) and Rapid Shallow Breathing Index (37 ± 11 versus 44 ± 13, p = 0.029) and with higher Pressure Muscle Index (2 [0.5, 3] versus 0.4 [0, 1.9], p = 0.024). Change in diaphragm thickness was not related to diaphragm function expressed as diaphragm thickening fraction. CONCLUSION: Mode of ventilation affects diaphragm thickness, and preservation of diaphragmatic contraction, as during assisted modes, can partially reverse the muscle atrophy process. Avoiding a strenuous inspiratory work, as measured by Rapid Shallow Breathing Index and Pressure Muscle Index, may help diaphragm thickness restoration.

A Calibration Technique for the Estimation of Lung Volumes in Nonintubated Subjects by Electrical Impedance Tomography.

BACKGROUND: Electrical impedance tomography (EIT) is a bedside monitoring technique of the respiratory system that measures impedance changes within the thorax. The close correlation between variations in impedance (ΔZ) and lung volumes (Vt) is known. Unless Vt is measured by an external reference (e.g., spirometry), its absolute value (in milliliters) cannot be determined; however, measurement of Vt would be useful in nonintubated subjects. OBJECTIVE: To validate a simplified and feasible calibration method of EIT, which allows estimation of Vt in nonintubated subjects. MATERIALS AND METHODS: We performed a prospective study on 13 healthy volunteers. Subjects breathed 10 times in a nonexpandable "calibration balloon" with a known volume while wearing the EIT belt. The relationship between ΔZ and the balloon volume was calculated (ΔZ/Vt). Subsequently, subjects were connected to a mechanical ventilator by a mouthpiece under different settings. Vt was calculated from EIT measurements (VtEIT) by means of the ΔZ/Vt coefficient and compared with the value obtained from the ventilator (Vtflow). RESULTS: There was a close correlation between Vtflow and VtEIT (r2 = 0.89). The fit equation was VtEIT = 0.9 × Vtflow +10.1. The highest correlation was found at positive endexpiratory pressure (PEEP) 0 (mean: VtEIT = 0.93 × Vtflow) versus PEEP 8 (mean: VtEIT = 0.8 × Vtflow), p = 0.01. No differences in the fit equation were found between pressure support ventilation (PSV) 0 and PSV 8, p = 0.50. Further analysis showed no statistically significant differences between sex, height, and BMI. CONCLUSION: A simple and fast EIT calibration technique enables reliable, noninvasive monitoring of Vt in nonintubated subjects.

Early prediction of hospital outcomes in patients tracheostomized for complex mechanical ventilation weaning.

BACKGROUND: Tracheostomy is often performed in the intensive care unit (ICU) when mechanical ventilation (MV) weaning is prolonged to facilitate daily care. Tracheostomized patients require important healthcare resources and have poor long-term prognosis after the ICU. However, data lacks regarding prediction of outcomes at hospital discharge. We looked for patients' characteristics, ventilation parameters, sedation and analgesia use (pre-tracheostomy) that are associated with favorable and poor outcomes (post-tracheostomy) using univariate and multivariate logistic regressions. RESULTS: Eighty tracheostomized patients were included (28.8% women, 60 [52-71] years). Twenty-three (28.8%) patients were intubated for neurological reasons. Time from intubation to tracheostomy was 14.7 [10-20] days. Thirty patients (37.5%) had poor outcome (19 patients deceased and 11 still tracheostomized at hospital discharge). All patients discharged with tracheostomy (n = 11) were initially intubated for a neurological reason. In univariate logistic regressions, older age and higher body-mass index (BMI) were associated with poor outcome (OR 1.18 [1.07-1.32] and 1.04 [1.01-1.08], p < 0.001 and p = 0.025). No MV parameters were associated with poor outcome. In the multiple logistic regression model higher BMI and older age were also associated with poor outcome (OR 1.21 [1.09-1.36] and 1.04 [1.00-1.09], p < 0.001 and p = 0.046). CONCLUSIONS: Hospital mortality of patients tracheostomized because of complex MV weaning was high. Patients intubated for neurological reasons were frequently discharged from the acute care hospital with tracheostomy in place. Both in univariate and multivariate logistic regressions, only BMI and older age were associated with poor outcome after tracheostomy for patients undergoing prolonged MV weaning.

Response to the first awake prone positioning relates with intubation rate in SARS-CoV-2 patients suffering from acute respiratory failure with moderate to severe hypoxaemia: a retrospective study.

AIMS OF THE STUDY: Awake prone positioning (aPP) in non-intubated patients with severe SARS-CoV-2-related pneumonia improves oxygenation and reduces the intubation rate, but no early predictors for success or failure of the strategy have been described. The main objective of this study was to assess whether response to the first aPP in terms of PaO2/FiO2, alveolar-arterial gradient (Aa-O2), respiratory rate and PaCO2 could predict the need for intubation. As secondary objective, we assessed the effects of aPP on the same parameters for all the sessions considered together. METHODS: Retrospective analysis of consecutive SARS-CoV-2 pneumonia patients suffering from acute respiratory failure with moderate to severe hypoxaemia for whom aPP was performed for at least 45 minutes based on the prescription of the clinician in charge according to predefined criteria. Respiratory rate, blood gases and oxygenation parameters (PaO2/FiO2 and Aa-O2), before and after the first aPP were compared between patients who were subsequently intubated or not. Effects of all the aPP sessions together were also analysed. RESULTS: One hundred and sixty-six patients were admitted for SARS-CoV-2 pneumonia during the study period. Among them, 50 received aPP lasting at least 45 minutes. Because 17 denied consent for data analysis and 2 were excluded because of a "do not intubate order", 31 patients (for a total of 116 aPP sessions without any severe adverse events reported) were included. Among them, 10 (32.3%) were intubated. Mean age ± standard deviation (SD) was 60 ± 12 years. At ICU admission, respiratory rate was 26 ± 7/minute, median PaO2/FiO2 94 (interquartile range [IQR] 74-116) mm Hg and median Aa-O2 412 (IQR 286-427) mm Hg (markedly increased). Baseline characteristics did not statistically differ between patients who subsequently needed intubation or not. During the first aPP, PaO2/FiO2 increased and Aa-O2 decreased. When comparing patients who later where intubated or not, we observed, in the non intubated group only, a clinically significant decrease in median Aa-O2, from 294 (280-414) to 204 (107-281) mm Hg, corresponding to a 40% (26-56%) reduction, and a PaO2/FiO2 increase, from 103 (84-116) to 162 (138-195), corresponding to an increase of 48% (11-93%). The p value is <0.005 for both. When all the aPP sessions (n = 80) were considered together, aPP was associated with a significant increase in PaO2/FiO2 from 112 (80-132) to 156 (86-183) mm Hg (p <0.001) and Aa-O2 decrease from 304 (244-418) to 224 (148-361) mm Hg (p = 0.001). CONCLUSIONS: Awake pronation in spontaneously breathing patients is feasible, and improves PaO2/FiO2 and Aa-O2. Response to the first session seems to be associated with lower intubation rate.