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Associations between changes in oxygenation, dead space and driving pressure induced by the first prone position session and mortality in patients with acute respiratory distress syndrome.

ABSTRACT: Background:Outcome prediction in acute respiratory distress syndrome (ARDS) is challenging, especially in patients with severe hypoxemia. The aim of the current study was to determine the prognostic capacity of changes in PaO2/FiO2, dead space fraction (VD/VT) and respiratory system driving pressure (?PRS) induced by the first prone position (PP) session in patients with ARDS. Methods:This was a post hoc analysis of the conveniently-sized 'Molecular Diagnosis and Risk Stratification of Sepsis' study (MARS). The current analysis included ARDS patients who were placed in the PP. The primary endpoint was the prognostic capacity of the PP-induced changes in PaO2/FiO2, VD/VT, and ?PRS for 28-day mortality. PaO2/FiO2, VD/VT, and ?PRS was calculated using variables obtained in the supine position before and after completion of the first PP session. Receiving operator characteristic curves (ROC) were constructed, and sensitivity, specificity positive and negative predictive value were calculated based on the best cutoffs. Results:Ninety patients were included; 28-day mortality was 46%. PP-induced changes in PaO2/FiO2 and VD/VT were similar between survivors vs. non-survivors [+83 (+24 to +137) vs. +58 (+21 to +113) mmHg, and -0.06 (-0.17 to +0.05) vs. -0.08 (-0.16 to +0.08), respectively]. PP-induced changes in ?PRS were different between survivors vs. non-survivors [-3 (-7 to 2) vs. 0 (-3 to +3) cmH2O; P=0.03]. The area under the ROC of PP-induced changes in ?PRS for mortality, however, was low [0.63 (95% confidence interval (CI), 0.50 to 0.75]; PP-induced changes in ?PRS had a sensitivity and specificity of 76% and 56%, and a positive and negative predictive value of 60% and 73%. Conclusions:Changes in PaO2/FiO2, VD/VT, and ?PRS induced by the first PP session have poor prognostic capacities for 28-day mortality in ARDS patients.

SUBMITTER: van Meenen DM

PROVIDER: S-EPMC6987992 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Associations between changes in oxygenation, dead space and driving pressure induced by the first prone position session and mortality in patients with acute respiratory distress syndrome.

van Meenen David M DM Roozeman Jan-Paul JP Serpa Neto Ary A Pelosi Paolo P Gama de Abreu Marcelo M Horn Janneke J Cremer Olaf L OL Paulus Frederique F Schultz Marcus J MJ

Journal of thoracic disease 20191201 12

<h4>Background</h4>Outcome prediction in acute respiratory distress syndrome (ARDS) is challenging, especially in patients with severe hypoxemia. The aim of the current study was to determine the prognostic capacity of changes in PaO<sub>2</sub>/FiO<sub>2</sub>, dead space fraction (V<sub>D</sub>/V<sub>T</sub>) and respiratory system driving pressure (ΔP<sub>RS</sub>) induced by the first prone position (PP) session in patients with ARDS.<h4>Methods</h4>This was a post hoc analysis of the conven ...[more]

PMID: 32030216

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Project description:Rationale: Clinicians commonly use short-term physiologic markers to assess the benefit of ventilator adjustments. Improved arterial oxygen tension/pressure (PaO2)/fraction of inspired oxygen (FiO2) after ventilator adjustment in acute respiratory distress syndrome is associated with lower mortality. However, as driving pressure (ΔP) reflects lung stress and strain, changes in ΔP may more accurately reflect benefits or harms of ventilator adjustments compared with changes in oxygenation.Objectives: We aimed to compare the association between mortality and the changes in PaO2/FiO2 and ΔP following protocolized ventilator changes.Methods: We assessed associations between mortality and changes in PaO2/FiO2 (ΔPaO2/FiO2) and ΔP (ΔΔP) after postrandomization positive end-expiratory pressure (PEEP) and tidal volume adjustment in reanalyses of the ALVEOLI (Assessment of Low Tidal Volume and Elevated End-Expiratory Volume to Obviate Lung Injury) and ExPress (Expiratory Pressure) trials. We included subjects with available pre- and postintervention PaO2/FiO2 and ΔP (372 in ALVEOLI and 596 in ExPress). In each separate trial cohort, we performed multivariable Cox regression testing the association between ΔPaO2/FiO2 and ΔΔP with mortality.Results: In ALVEOLI, when analyzed as separate variables, ΔPaO2/FiO2 was associated with mortality only in subjects in whom PEEP increased, whereas ΔΔP was associated with mortality irrespective of direction of PEEP change. When modeled together, improved ΔPaO2/FiO2 was not associated with mortality, whereas ΔΔP remained associated with mortality (adjusted hazard ratio [aHR], 1.50 per 5 cm H2O increase; 95% confidence interval [95% CI], 1.21-1.85). When modeled together in ExPress, ΔΔP (aHR, 1.42; 95% CI, 1.14-1.78) was more strongly associated with mortality than ΔPaO2/FiO2 (aHR, 0.95 per 25 mm Hg increase; 95% CI, 0.90-1.00).Conclusions: Reduced ΔP following protocolized ventilator changes was more strongly and consistently associated with lower mortality than was increased PaO2/FiO2, making ΔΔP more informative about benefit from ventilator adjustments. Our results reinforce the primacy of ΔP, rather than oxygenation, as the key variable associated with outcome.

Project description:OBJECTIVES:Physiologic dead space is associated with mortality in acute respiratory distress syndrome, but its measurement is cumbersome. Alveolar dead space fraction relies on the difference between arterial and end-tidal carbon dioxide (alveolar dead space fraction = (PaCO2 - PetCO2) / PaCO2). We aimed to assess the relationship between alveolar dead space fraction and mortality in a cohort of children meeting criteria for acute respiratory distress syndrome (both the Berlin 2012 and the American-European Consensus Conference 1994 acute lung injury) and pediatric acute respiratory distress syndrome (as defined by the Pediatric Acute Lung Injury Consensus Conference in 2015). DESIGN:Secondary analysis of a prospective, observational cohort. SETTING:Tertiary care, university affiliated PICU. PATIENTS:Invasively ventilated children with pediatric acute respiratory distress syndrome. INTERVENTIONS:None. MEASUREMENTS AND MAIN RESULTS:Of the 283 children with pediatric acute respiratory distress syndrome, 266 had available PetCO2. Alveolar dead space fraction was lower in survivors (median 0.13; interquartile range, 0.06-0.23) than nonsurvivors (0.31; 0.19-0.42; p < 0.001) at pediatric acute respiratory distress syndrome onset, but not 24 hours after (survivors 0.12 [0.06-0.18], nonsurvivors 0.14 [0.06-0.25], p = 0.430). Alveolar dead space fraction at pediatric acute respiratory distress syndrome onset discriminated mortality with an area under receiver operating characteristic curve of 0.76 (95% CI, 0.66-0.85; p < 0.001), better than either initial oxygenation index or PaO2/FIO2. In multivariate analysis, alveolar dead space fraction at pediatric acute respiratory distress syndrome onset was independently associated with mortality, after adjustment for severity of illness, immunocompromised status, and organ failures. CONCLUSIONS:Alveolar dead space fraction at pediatric acute respiratory distress syndrome onset discriminates mortality and is independently associated with nonsurvival. Alveolar dead space fraction represents a single, useful, readily obtained clinical biomarker reflective of pulmonary and nonpulmonary variables associated with mortality.

Project description:BackgroundIn 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.ResultsWe 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.ConclusionsThere 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.

Dataset Information

Associations between changes in oxygenation, dead space and driving pressure induced by the first prone position session and mortality in patients with acute respiratory distress syndrome.

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Associations between changes in oxygenation, dead space and driving pressure induced by the first prone position session and mortality in patients with acute respiratory distress syndrome.

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