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An objective study of acid reflux and cough in children using an ambulatory pHmetry–cough logger
  1. A B Chang1,2,
  2. F L Connor3,
  3. H L Petsky1,
  4. M M Eastburn1,4,
  5. P J Lewindon3,
  6. C Hall3,
  7. S J Wilson4,
  8. P H Katelaris5
  1. 1Queensland Children's Respiratory Centre and Queensland Children's Medical Research Institute, Royal Children's Hospital, Brisbane, Australia
  2. 2Child Health Division, Menzies School of Health Research, Darwin, Australia
  3. 3Department of Gastroenterology, Royal Children's Hospital, Brisbane, Australia
  4. 4School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Australia
  5. 5Department of Gastroenterology, Concord Hospital, University of Sydney, Sydney, Australia
  1. Correspondence to Professor Anne B Chang, Queensland Children's Respiratory Centre, Royal Children's Hospital, Herston Rd, Herston, Queensland 4029, Australia; annechang{at}


Objective There are no objective ambulatory studies on the temporal relationship between reflux and cough in children. Commercial pHmetry loggers have slow capture rates (0.25 Hz) that limit objective quantification of reflux and cough. The authors aimed to evaluate if there is a temporal association between cough and acid pH in ambulatory children with chronic cough.

Design, setting and patients The authors studied children (aged <14 years) with chronic cough, suspected of acid reflux and considered for pHmetry using a specifically built ambulatory pHmetry–cough logger that enabled the simultaneous ambulatory recording of cough and pH with a fast (10 Hz) capture rate.

Main outcome measures Coughs within (before and after) 10, 30, 60 and 120 s of a reflux episode (pH<4 for >0.5 s).

Results Analysis of 5628 coughs in 20 children. Most coughs (83.9%) were independent of a reflux event. Cough–reflux (median 19, IQR 3–45) and reflux–cough (24.5, 13–51) sequences were equally likely to occur within 120 s. Within the 10 and 30 s time frame, reflux–cough (10 s=median 2.5, IQR 0–7.25; 30 s=6.5, 1.25–22.25) sequences were significantly less frequent than reflux–no cough (10 s=27, IQR 15–65; 30 s=24.5, 14.5–55.5) sequences, (p=0.0001 and p=0.001, respectively). No differences were found for 60 and 120 s time frame. Cough–reflux sequence (median 1.0, IQR 0–8) within 10 s was significantly less (p=0.0001) than no cough–reflux sequences (median 29.5, 15–67), within 30 s (p=0.006) and 60 s (p=0.048) but not within 120 s (p=0.47).

Conclusions In children with chronic cough and suspected of having gastro-oesophageal reflux disease, the temporal relationship between acid reflux and cough is unlikely causal.

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  • Funding Royal Children's Hospital Foundation.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Royal Children's Hospital and University of Queensland.

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