title: Physiological Correlation of Airway Pressure and Transpulmonary Pressure Stress Index on Respiratory Mechanics in Acute Respiratory Failure.
abstract: BACKGROUND
  Stress index at post-recruitment maneuvers could be a method of positive end-expiratory pressure (PEEP) titration in acute respiratory distress syndrome (ARDS) patients. However, airway pressure (Paw) stress index may not reflect lung mechanics in the patients with high chest wall elastance. This study was to evaluate the Pawstress index on lung mechanics and the correlation between Pawstress index and transpulmonary pressure (PL) stress index in acute respiratory failure (ARF) patients.
  
  
  METHODS
  Twenty-four ARF patients with mechanical ventilation (MV) were consecutively recruited from July 2011 to April 2013 in Zhongda Hospital, Nanjing, China and Ospedale S. Giovanni Battista-Molinette Hospital, Turin, Italy. All patients underwent MV with volume control (tidal volume 6 ml/kg) for 20 min. PEEP was set according to the ARDSnet study protocol. The patients were divided into two groups according to the chest wall elastance/respiratory system elastance ratio. The high elastance group (H group, n = 14) had a ratio ≥30%, and the low elastance group (L group, n = 10) had a ratio <30%. Respiratory elastance, gas-exchange, Pawstress index, and PLstress index were measured. Student's t-test, regression analysis, and Bland-Altman analysis were used for statistical analysis.
  
  
  RESULTS
  Pneumonia was the major cause of respiratory failure (71.0%). Compared with the L group, PEEP was lower in the H group (5.7 ± 1.7 cmH2O vs. 9.0 ± 2.3 cmH2O, P < 0.01). Compared with the H group, lung elastance was higher (20.0 ± 7.8 cmH2O/L vs. 11.6 ± 3.6 cmH2O/L, P < 0.01), and stress was higher in the L group (7.0 ± 1.9 vs. 4.9 ± 1.9, P = 0.02). A linear relationship was observed between the Pawstress index and the PLstress index in H group (R2 = 0.56, P < 0.01) and L group (R2 = 0.85, P < 0.01).
  
  
  CONCLUSIONS
  In the ARF patients with MV, Pawstress index can substitute for PLto guide ventilator settings.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT02196870 (https://clinicaltrials.gov/ct2/show/NCT02196870).
authors.affiliation: Department of Critical Care Medicine, Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Pan
authors.affiliation: Department of Critical Care Medicine, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Critical Care Medicine, Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Yun-Hang
authors.initials: YH
authors.lastname: Zhang
authors.affiliation: Department of Biopharmaceutics, School of Life Science and Technology, Chinese Pharmaceutical University, Nanjing, Jiangsu 210009, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Ospedale S. Giovanni Battista-Molinette, Turin 10126, Italy.
authors.forename: Rosario
authors.initials: R
authors.lastname: Urbino
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Ospedale S. Giovanni Battista-Molinette, Turin 10126, Italy.
authors.forename: V Marco
authors.initials: VM
authors.lastname: Ranieri
authors.affiliation: Department of Critical Care Medicine, Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Qiu
authors.affiliation: Department of Critical Care Medicine, Zhongda Hospital, Medical School, Southeast University, Nanjing, Jiangsu 210009, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
mesh_terms: D000328:Adult; D002681:China; D005260:Female; D006801:Humans; D008168:Lung / Q000502:physiology; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012044:Regression Analysis; D012128:Respiratory Distress Syndrome / Q000628:therapy*; D015656:Respiratory Mechanics; D013990:Tidal Volume / Q000502:physiology