title: Use of a two-way non-rebreathing valve to simplify the measurement of twitch mouth pressure using an inspiratory pressure trigger and the establishment of an optimal trigger threshold for healthy subjects and COPD patients.
abstract: OBJECTIVE
  Controlled twitch mouth pressure (Tw Pmo) via the use of a two-way non-rebreathing valve is a new method to assess diaphragm contractility. The optimal trigger threshold was confirmed.
  
  
  METHODS
  We sought to determine the optimal trigger threshold for 17 healthy subjects (29±4 years) and 17 COPD patients (64±10 years). The Tw Pmo, twitch oesophageal pressure (Tw Pes) and twitch transdiaphragmatic pressure (Tw Pdi) in response to phrenic nerve stimulation were measured using an inspiratory pressure trigger at -1, -2, -3, -4, -5 and -6 cmH2O.
  
  
  RESULTS
  The lung volume did not change during triggering at different trigger thresholds using a two-way non-rebreathing valve. The highest correlation between Tw Pmo and Tw Pes in healthy subjects and COPD patients occurred for a -2 cmH2O trigger threshold (r=0.939 and r=0.869, P<0.0001). The narrowest limits of agreement for Tw Pmo and Tw Pes both occurred at -2 cmH2O in healthy subjects, with a bias (range) of -0.4 cmH2O (-1.85 to 1.41), and in COPD patients, with a bias (range) of 0.1 6cmH2O (-1.36-1.67).
  
  
  CONCLUSIONS
  We conclude that the measurement of Tw Pmo using a two-way non-rebreathing valve is of clinical value to investigate the suspected diaphragm contractility. The highest trigger threshold for clinical applications was -2 cmH2O.
authors.affiliation: Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, No. 151 Yanjiang Road, Guangzhou, China.
authors.forename: D M
authors.initials: DM
authors.lastname: Hua
authors.affiliation: Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, No. 151 Yanjiang Road, Guangzhou, China.
authors.forename: Z M
authors.initials: ZM
authors.lastname: Lin
authors.affiliation: Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, No. 151 Yanjiang Road, Guangzhou, China.
authors.forename: Y E
authors.initials: YE
authors.lastname: Ou
authors.affiliation: Department of Intensive Care Unit, Guangzhou Brain Hospital, No. 36 Mingxin Road, Guangzhou, China.
authors.forename: Y K
authors.initials: YK
authors.lastname: Xie
authors.affiliation: Department of Intensive Care Unit, Guangzhou First People's Hospital, No. 1 Panfu Road, Guangzhou, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Zhengzhou University, No.1 Jianshe East Road, Zhengzhou, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, No. 151 Yanjiang Road, Guangzhou, China.
authors.forename: Z G
authors.initials: ZG
authors.lastname: Zheng
authors.affiliation: Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, No. 151 Yanjiang Road, Guangzhou, China. Electronic address: chenrc@vip.163.com.
authors.forename: R C
authors.initials: RC
authors.lastname: Chen
authors.affiliation: Guangzhou Institute of Respiratory Disease, State Key Laboratory of Respiratory Disease, The First Affiliated Hospital of Guangzhou Medical University, No. 151 Yanjiang Road, Guangzhou, China.
authors.forename: N S
authors.initials: NS
authors.lastname: Zhong
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003964:Diaphragm / Q000503:physiopathology*; D004558:Electric Stimulation; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009055:Mouth; D009119:Muscle Contraction / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D011312:Pressure; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology* / Q000503:physiopathology; D012123:Pulmonary Ventilation
keywords: Assessment of diaphragm; Inspiratory pressure trigger; Respiratory muscle strength twitch pressure