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Neural respiratory drive as a physiological biomarker to monitor change during acute exacerbations of COPD
  1. Patrick B Murphy1,
  2. Atul Kumar2,
  3. Charles Reilly1,
  4. Caroline Jolley1,
  5. Stephan Walterspacher2,
  6. Fiammetta Fedele3,
  7. Nicholas S Hopkinson4,
  8. William D-C Man4,
  9. Michael I Polkey4,
  10. John Moxham1,
  11. Nicholas Hart5
  1. 1Department of Asthma, Allergy and Respiratory Science, Division of Asthma, Allergy and Lung Biology, King's College London, London, UK
  2. 2School of Medicine, King's College London, London, UK
  3. 3Department of Medical Physics, Guy's and St Thomas' NHS Foundation Trust, London, UK
  4. 4National Heart and Lung Institute, Respiratory Biomedical Research Unit, Royal Brompton Hospital and Imperial College London, London, UK
  5. 5Guy's and St Thomas' NHS Foundation Trust and King's College London, National Institute of Health Research Comprehensive Biomedical Research Centre, London UK
  1. Correspondence to Dr Patrick B Murphy, Lane Fox Respiratory Unit, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK; patrick.b.murphy{at}



Background Acute exacerbations of chronic obstructive pulmonary disease have a significant negative impact on both patients and healthcare systems. Currently, there are no physiological biomarkers that effectively monitor clinical change or predict respiratory readmission. Acute exacerbations impose a change in the respiratory muscle load-capacity-drive relationship. It was hypothesised that lack of a fall in neural respiratory drive would identify patients at risk of treatment failure and early hospital readmission.


Methods An observational study was performed at two UK teaching hospitals. Routine clinical physiological parameters and neural respiratory drive index (NRDI), calculated as the product of second intercostal space parasternal electromyography (EMG) activity normalised to the peak EMG activity during a maximum inspiratory sniff manoeuvre and respiratory rate, were recorded daily from admission to discharge.


Results 30 acutely unwell patients of mean (SD) age 72 (10) years, forced expiratory volume in 1 s 0.60 (1.65) l, NRDI 455 (263) AU and median length of stay 6 days were studied. Changes in NRDI correlated with changes in Borg score (r=+0.60; p<0.001), discriminated between patients deemed to have clinically improved rather than deteriorated (mean difference 339 AU; 95% CI 234 to 444; p<0.001) and identified those patients readmitted within 14 days (mean difference 203 AU; 95% CI 39 to 366; p=0.017).


Conclusions NRDI is a feasible clinical physiological parameter in patients with an acute exacerbation of chronic obstructive pulmonary disease and can provide useful information on treatment response and risk of readmission.

  • Respiratory physiology
  • chronic obstructive pulmonary disease
  • hospital readmission
  • COPD exacerbations
  • respiratory muscles

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  • Funding The work included within this manuscript was supported with grants from Guy's and St Thomas' Innovation Fund for Technology Transfer and NHS Innovations London. The authors acknowledge support from the Department of Health via the National Institute of Health Research (NIHR) Comprehensive Biomedical Research Centre award to Guy's and St Thomas' NHS Foundation Trust in partnership with King's College London and King's College Hospital NHS Foundation Trust. MIP's salary is part funded by the NIHR Respiratory Biomedical Research Unit of the Royal Brompton Hospital and Imperial College.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the King's College Hospital REC.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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