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.

Right ventricular time intervals - Comparison between pulsed wave Doppler and tissue Doppler imaging.

BACKGROUND: Cardiac time intervals are used as indices of systolic and diastolic function. Echocardiographic assessment of these intervals is based on either pulsed wave Doppler (PWD) or tissue Doppler imaging (TDI). We investigated the agreement between the two techniques in the evaluation of right ventricular (RV) time intervals in healthy adults. METHODS: In 123 healthy volunteers we used both PWD and TDI to assess RV time intervals (filling time - RVFT, ejection time - RVET), heart rate-corrected intervals (total filling time - t-FT, total ejection time - t-ET) and RV performance indices (total isovolumic time - t-IVT, myocardial performance index - MPI). Intraclass correlation coefficient (ICC) and Pearson analysis (r coefficient) were used to evaluate the agreement and correlation between the two techniques. RESULTS: PWD and TDI had excellent agreement and correlation in measuring RVFT (ICC 0.94 [95% CI 0.85 - 0.97], r 0.91) whereas a good agreement was found for RVET (ICC 0.63[95% CI - 0.14 - 0.84]; r 0.68). Good agreement and strong correlation were found for both t-FT (ICC 0.67 [95% CI 0.36 - 0.82]; r 0.59) and t-ET (ICC 0.71 [95% CI - 0.06-0.88]; r 0.74). The two methods had lower agreement in assessing RV t-IVT (ICC 0.52 [95% CI 0.3187-0.6622]; r 0.57) and MPI (ICC 0.36 [95% CI - 0.05-0.43]; r 0.50). CONCLUSION: In healthy adults, PWD and TDI are interchangeable in measuring RVFT, RVET, RV t-FT and RV t-ET. Lower agreement between the two techniques was found for RV t-IVT and MPI.

Right ventricular total isovolumic time: Reference value study.

BACKGROUND: There is lack of noninvasive indices to detail the right side cardiovascular physiology. Total isovolumic time (tIVT) is a sensitive marker of left ventricular electromechanical efficiency and systolic-diastolic interaction. The aim of the study was to evaluate normal reference value of the right ventricular tIVT with increasing age. METHODS AND RESULTS: One hundred and eighty-one healthy volunteers (51% male) underwent transthoracic echocardiography. The population was divided into four categories according to age: A < 30 years; B 30-39 years; C 40-49 years; and C ≥ 50 years old. tIVT was computed in seconds/minutes as: 60 - (tET + tFT). tET and tFT are the total ejection and filling time adjusted by the heart rate, measured, respectively, from the onset to the end of the right ventricle (RV) forward flow through the pulmonary valve and from the onset of the E-wave and the end of the A-wave at the level of the tricuspid valve. The mean RV tIVT was 7 ± 1.1 s/min and increased significantly with age, from a 3.4 to 9.7 s/min(P < 0.0001). Significant correlation was found between tIVT and trans-tricuspid E/E' (P < 0.0001; 0.78 (95% CI: 0.715-0.831) while weaker between tIVT and E/A (P = 0.001; -0.283 95% CI: -0.413 to -0.143). CONCLUSION: The normal values of RV tIVT increase with age and correlate significantly with Doppler diastolic parameters.

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.