Gastro-oesophageal reflux (GOR) during spirometry: prevalence and effects

Background: Variability during spirometry can persist despite control of technical and personal factors. We postulate spirometry induces GOR, which may cause variability of spirometry. Aims and Objectives: Pilot study assessing prevalence of GOR during spirometry and its effects on spirometry variability in subjects having outpatient GOR assessment. Methods: At the end of oesophageal manometry and 24hr pH monitoring, 56 subjects performed 2 sets of spirometry separated by a 10-minute break. We quantify 24hr GOR with the De-Meester score (≥14.72 in significant GOR). Assessment for GOR during spirometry starts with 1st spirometry and ends with 2nd spirometry. Variability of spirometry (%)=max value-min value/max value x 100. Results: 26 subjects (44%) had GOR during assessment: 18 during the 10-minute break with 3 persisting into the 2nd spirometry, 5 throughout assessment, and 3 during spirometry only. They tend to have higher De-Meester scores (mean 39.8 vs 26.8, t test p=0.13) and are more likely have a GOR event preceding the 1st spirometry (median time interval [min] 8.5 [IQR 5–12] vs 25 [IQR 10–70]), compared to 30 subjects without GOR during spirometry assessment. 15 subjects with GOR had reproducible spirometry: mean 2nd FVC and FEV1 were non-significantly higher by 20 & 12mL respectively. Mean variability of spirometry (%) ± SD was similar between GOR and non-GOR groups: Conclusion: GOR occurs during and following spirometry in subjects having outpatient GOR assessment, but does not significantly impact spirometry variability over 10 minutes.