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Prediction of extubation outcome in infants using the tension time index
  1. Andrew Currie,
  2. Deena-Shefali Patel,
  3. Gerrard F Rafferty,
  4. Anne Greenough
  1. Division of Asthma, Allergy & Lung Biology, MRC-Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, UK
  1. Correspondence to Professor Anne Greenough, Department of Child Health, 4th Floor Golden Jubilee Wing, King's College Hospital, London SE5 9RS, UK; anne.greenough{at}


Objective Approximately one-third of ventilated infants fail extubation. The objective of this study was to determine whether assessment of the load relative to the capacity of respiratory muscles by measurement of the tension time index (TTI) successfully predicted extubation outcome in infants.

Design Prospective study.

Setting Tertiary neonatal intensive care unit.

Patients Twenty ventilated infants, with a median gestational age of 31 (range 24–39) weeks, were studied at a median postnatal age of 2.5 (range 1–37) days.

Interventions The diaphragm tension time index (TTdi) was derived from measurements of transdiaphragmatic pressure using a dual-pressure transducer tipped catheter. The respiratory muscle tension time index (TTmus) was derived from non-invasive airway pressure measurements. Measurements were made within the 6 h prior to extubation.

Main outcome measures Extubation failure was defined as the need for reintubation within 48 h of extubation.

Results Five infants failed extubation; their median TTdi (p=0.001) and TTmus (p=0.001) were significantly higher than those of the successfully extubated infants. A TTdi of >0.15 and a TTmus of >0.18 were 100% sensitive and 100% specific in predicting extubation failure

Conclusion In ventilated infants, invasive and non-invasive measurements of the TTI could provide an accurate prediction of extubation outcome.

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  • Funding DS-P was supported by The Charles Wolfson Charitable Trust.

  • Competing interests None.

  • Ethics approval Not commissioned; externally peer reviewed.

  • Patient consent Obtained from the parents.

  • Provenance and peer review Ethics approval was provided by the King's College Hospital Research Ethics Committee.