Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine.
The ratio of tidal volume to functional residual capacity (FRC), defined as "volumetric" strain, causes physical lung deformation. The corresponding change in transpulmonary pressure at end inspiration, defined as stress, is directly applied to the alveolus [1]. Both stress and strain may cause global or local lung deformation and microscopic or macroscopic tissue damage, representing significant determinants of ventilator-induced lung injury [1]. A modified nitrogen washout/washin technique, measuring end-expiratory lung volume (EELV), correlated well with computed tomography and was proposed as a valuable tool to optimize ventilator settings, improving lung protective ventilation [2]. The aim of this study was to evaluate the effect of positive end-expiratory pressure (PEEP) on EELV, compliance of the respiratory system (Crs), and stress/strain in children with acute respiratory distress syndrome (ARDS), and compare it with children "at risk of ARDS" and those with no lung injury using the modified nitrogen washout/washin technique (see electronic supplementary material). To monitor the effects of the disease evolution on the PEEP-induced increases in lung stress/strain, measurements were repeated at predetermined time points. We hypothesized that PEEP escalation increases EELV, Crs, strain, and stress in mechanically ventilated children, potentially influenced by disease severity and timing. A total of 700 measurements were recorded in 25 mechanically ventilated critically ill children (ARDS, n = 8; at risk of ARDS, n = 5; without lung injury, n = 12). ARDS patients had higher oxygenation index (OI > 4) and PaCO 2 , lower PaO 2 /FiO 2 , PaO 2 , and prolonged length of
BACKGROUND: It is unknown whether lung mechanics differ between patients with pediatric ARDS and at risk for ARDS. We aimed to examine the hypothesis that, compared to ARDS, subjects at risk of ARDS are characterized by higher end-expiratory lung volume (EELV) or respiratory system compliance (C RS) and lower distending pressure (stress) applied on the lung or parenchymal deformation (strain) during mechanical ventilation. METHODS: Consecutively admitted subjects fulfilling the PALICC ARDS criteria were considered eligible for inclusion in this study. A ventilator with an integrated gas exchange module was used to calculate EELV, C RS , strain, and stress after a steady state had been achieved based on nitrogen washout/washin technique. All subjects were subjected to incremental PEEP trials at 0, 6, 12, 24, 48, and 72 h. RESULTS: A total of 896 measurements were longitudinally calculated in 32 mechanically ventilated subjects (n 5 15 subjects with ARDS; n 5 17 subjects at risk for ARDS). EELV correlated positively with strain or stress in the ARDS group (r 5 0.30, P < .001) and the at risk group (r 5 0.60, P < .001). C RS correlated with strain (r 5 0.40, P < .001) only in subjects at risk for ARDS. EELV increased over time as PEEP rose from 4 to 10 cm H 2 O in subjects with ARDS (P 5 .001). In the at risk group, EELV only increased at 48 h (P 5 .001). Longitudinally, C RS (P 5 .001) and EELV (P 5 .002) were lower and strain and stress were higher in subjects with ARDS compared to those at risk for ARDS (P 5 .002), remaining within safe limits. Strain and stress increased by 24 h but declined by 72 h in subjects with ARDS at a PEEP of 4 cm H 2 O (P 5 .02). In the at risk group, strain and stress declined from 6 h to 72 h at a PEEP of 10 cm H 2 O (P 5 .001). CONCLUSIONS: Longitudinally, C RS and EELV were lower and strain and stress were higher in subjects with ARDS compared to subjects at risk for ARDS. These parameters behaved differently over time at PEEP values of 4 or 10 cm H 2 O. At these PEEP levels, strain and stress remained within safe limits in both groups.
Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high‐ (HICs) and low‐ and middle‐income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7‐day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally.
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