title: Increased flow resistance and decreased flow rate in patients with acute respiratory distress syndrome: The role of autonomic nervous modulation.
abstract: BACKGROUND
  The aim of this study was to investigate the flow resistance and flow rate in patients with acute respiratory distress syndrome (ARDS) in the surgical intensive care unit and their relation with autonomic nervous modulation.
  
  
  METHODS
  Postoperative patients of lung or esophageal cancer surgery without ARDS were included as the control group (n = 11). Patients who developed ARDS after lung or esophageal cancer surgery were included as the ARDS group (n = 21). The ARDS patients were further divided into survivor and nonsurvivor subgroups according to their outcomes. All patients required intubation and mechanical ventilation.
  
  
  RESULTS
  The flow rate was significantly decreased, while the flow resistance was significantly increased, in ARDS patients. The flow rate correlated significantly and negatively with positive end-expiratory pressure (PEEP), while the flow resistance correlated significantly and positively with PEEP in ARDS patients. Furthermore, the flow rate correlated significantly and negatively with the tidal volume-corrected normalized high-frequency power but correlated significantly and positively with the tidal volume-corrected low-/high-frequency power ratio. In contrast, the flow resistance correlated significantly and negatively with normalized very low-frequency power and tidal volume-corrected low-/high-frequency power ratio, but correlated significantly and positively with tidal volume-corrected normalized high-frequency power.
  
  
  CONCLUSIONS
  The flow rate is decreased and the flow resistance increased in patients with ARDS. PEEP is one of the causes of increased flow resistance and decreased flow rate in patients with ARDS. Another cause of decreased flow rate and increased flow resistance in ARDS patients is the increased vagal activity and decreased sympathetic activity. The monitoring of flow rate and flow resistance during mechanical ventilation might be useful for the proper management of ARDS patients.
authors.affiliation: Institute of Emergency and Critical Care Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan, ROC; Intensive Care Unit, National Taiwan University Hospital, Taipei, Taiwan, ROC.
authors.forename: I-Chen
authors.initials: IC
authors.lastname: Chen
authors.affiliation: Laboratory of Biophysics, Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan, ROC.
authors.forename: Jane
authors.initials: J
authors.lastname: Kuo
authors.affiliation: Intensive Care Unit, National Taiwan University Hospital, Taipei, Taiwan, ROC.
authors.forename: Wen-Je
authors.initials: WJ
authors.lastname: Ko
authors.affiliation: Institute of Emergency and Critical Care Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan, ROC.
authors.forename: Hsin-Chin
authors.initials: HC
authors.lastname: Shih
authors.affiliation: Institute of Emergency and Critical Care Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan, ROC; Laboratory of Biophysics, Department of Medical Research, Taipei Veterans General Hospital, Taipei, Taiwan, ROC. Electronic address: cdkuo23@gmail.com.
authors.forename: Cheng-Deng
authors.initials: CD
authors.lastname: Kuo
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*
keywords: acute respiratory distress syndrome; autonomic; flow rate; flow resistance; intensive care unit; vagal