High-resolution esophageal manometry: addressing thermal drift of the manoscan system


Address for Correspondence
Dr Elaine Robertson, Division of Cardiovascular and Medical Sciences, University of Glasgow, 44 Church Street, Western Infirmary, Glasgow G11 6NT, UK.
Tel: +44 141 211 2513; fax: +44 141 211 2895;
e-mail: elaine.robertson@glasgow.ac.uk


Background  The high resolution esophageal manometry system manufactured by Sierra Scientific Instruments is widely used. The technology is liable to ‘thermal drift’, a change in measured pressure due to change in temperature. This study aims to characterize ‘thermal drift’ and minimize its impact.

Methods  Response of the system to immediate temperature change (20 °C to 37 °C) was tested. Accuracy of pressure measurement over two hours at 37 °C was examined. Six repetitions were performed and median pressure change calculated for each sensor. Sensors were compared using Kruskal-Wallis test. Current correction processes were tested.

Key Results  There was a biphasic response of the system to body temperature: an immediate change in recorded pressure, ‘thermal effect’ and an ongoing pressure change with time, ‘baseline drift’. Median thermal effect for all 36 sensors was 7 mmHg (IQR 3.8 mmHg). Median baseline drift was 11.1 mmHg (IQR 9.9 mmHg). Baseline drift varied between sensors but for a given sensor was linear. Interpolated thermal compensation, recommended for prolonged studies, corrects data assuming a linear drift of pressures. When pressures were corrected in this way, baseline pressure was almost restored to zero (Median 0.3 mmHg, IQR 0.3). The standard thermal compensation process did not address the error associated with baseline drift.

Conclusions & Inferences  Thermal effect is well compensated in the current operation of the system but baseline drift is not well recognized or addressed. Incorporation of a linear correction into current software would improve accuracy without impact on ease of use.