VALIDATION OF A NEW WATER-PERFUSED HIGH-RESOLUTION MANOMETRY SYSTEM

Water-perfused high resolution manometry system

reusable polyvinyl chloride (PVC) catheter had channels in different configuration for the analysis of the pharynx, the esophageal body and the lower esophageal sphincter (LES). Fourteen unilateral channels 2 cm a part (covering 28 cm) were used for the pharynx and esophageal body, while nine spiral channels at 5 mm intervals and angled 120° were used for the LES area (covering 4 cm). One channel was used to record gastric pressure (34 cm in total). Water-perfusion was provided by an original patented controlled peristaltic pump (Figures 1 and 2).

Normal values
Normal values for this new water-perfused HRM system were defined previously on 32 healthy volunteers 22 .

Manometric parameters
Manometric parameters evaluated were those standardized by the International High-Resolution Manometry Working Group in 2015, the Chicago classification 3.0 9 , with the addition of upper esophageal sphincter (UES) basal and relaxation pressures, and LES basal pressure, total and abdominal lengths that were part of the Chicago classification 11 . Data was obtained based on automated analysis by the dedicated software (Esofagica v.1492. Alacer Biomedica, São Paulo, Brazil).

pH monitoring test
Esophageal ambulatory pH monitoring (AL3, Alacer Biomedica, São Paulo, Brazil) was performed in all patients in group 1 after discontinuation of acid reducing medications. Patients were considered pH positive if the composite DeMeester score was higher than 14.7.

FIGURE 2 -Examples of esophageal motility disorders obtained
with a water-perfused high-resolution manometry system: A) normal peristalsis; B) ineffective motility in a patient with gastroesophageal reflux disease; C) jackhammer esophagus in a patient with dysphagia; D) achalasia; E) absent peristalsis in a patient with connective tissue disease; F) distal spasm

INTRODUCTION
H igh-resolution manometry (HRM) is more intuitive, comfortable and clinically superior as compared to conventional manometry; however, it is very costly 4,20 . HRM originated from a water-perfused system 7 and current parameters were defined based on solid-state systems 14 . Water-perfused systems may decrease costs using cheaper catheters with longer lifespan, but it has limitations on the total number of sensors, jeopardizing the maximum advantage of HRM, namely the high-density of close-spaced sensors. It is unclear if water-perfused systems are as reliable as solid-state systems and reference values may be imported from solid-state systems.
This study aims to validate normal values in a new water-perfusion HRM system.

METHODS
The project was approved by local ethics committee. The authors are responsible for the study, no professional or ghost writer was hired.

Subjects
Normal values were validated in 225 individuals prospectively studied with specific clinical complaints to encompass a large spectrum of esophageal motility disorders.

Group 2
Patients under evaluation for achalasia. Sample totaled 47 individuals. The mean age was 47.2±16.5 years, 14 males and 33 females.

Group 3
Individuals with systemic disease with possible impairment of esophageal motility. The sample totaled eight individuals. The mean age was 52±17.7 years, three males and five females. There were six patients with systemic sclerosis, one with myasthenia gravis and one with clozapine usage.

Group 4
Fourteen patients under evaluation for dysphagia who were not included in the prior groups. The sample totaled 14 individuals. The mean age was 55.26±17.2 years, four males and 10 females. There were three patients who underwent a Nissen fundoplication.

High-resolution manometry
HRM was performed as previously described 22 . The test was performed after 8 h fasting, and discontinuation of medications that could affect esophageal motility. The system was calibrated per manufacturer instructions. After a period for adaptation to the catheter, individuals were instructed to avoid swallowing for a period of 30 s in order to acquire resting parameters; subsequently 10 swallows of 5-ml every 30 s were given to acquire dynamic parameters. All tests were performed and interpreted by a single experienced esophagologist 21 .

Group 2 -achalasia
Manometric parameters and are shown in Table 2. All individuals had aperistalsis. In nine (19%) of the cases it was not possible to evaluate the LES. Incomplete relaxation was present in 24 (63%) of the cases when the LES was studied. Sixteen (34%) individuals were classified as achalasia type I, 31 (66%) type II, while no patient had type III achalasia.

Normative values
Very interestingly, the same normal values 18 were adopted by most authors irrespective of the used system. The same occurred at the beginning of the adoption of the HRM in clinical practice. Later, however, most authors realized that manometry systems are different and normative values must be defined for each type of equipment. There are different water-perfused systems available in which normal values were defined (Table 5) 2,3,9,24 . They clearly differ from solid state systems as they are associated with longer time variables and lower amplitudes due to the physical characteristics of the flow sensors. Normal values can always be obtained by recruiting and studying health volunteers; however, validation of the attained values must be always desirable in order to prove clinical application of this data. Our results show that solid-state reference values are not compatible with water perfused systems and that the reference values we studied for this specific system are adequate and sensitive in order to discriminate most motility disorders.

Group 1 -GERD
GERD pathophysiology is certainly multifactorial 13 but a defective LES is present in 50-70% of individuals with abnormal pH monitoring 1,5,15,27 . The rate of defective LES is within these limits in our study. Esophageal body hypomotility is also frequently found in GERD patients. Based on the current classification 9 the rate of IEM in GERD ranges from 38-50% 8,23 . Our rate is lower than in other published studies; however, in negative pH patients the rate is lower, consistent with other studies that show higher acid exposure in patients with IEM 17 . The rate of defective LES was also lower.

Group 2 -achalasia
The Chicago classification defines achalasia based on aperistalsis and impaired LES relaxation, and classifies the disease based on esophageal pressurization 9 . In our series, aperistalsis was consistently found in all patients that had untreated achalasia based on symptoms, endoscopic and radiologic evaluation. LES relaxation was, however, normal in 25% of the cases. This number is similar when a solidstate system is used 25 . Although this phenomenon was also found in idiopathic achalasia, it is more common in Chagas´ disease patients that comprised the majority of patients in our series 6,25 . For the same reason, achalasia Type III was not diagnosed as it is probably not found in Chagas´ disease esophagopathy 26 .

Group 3 -systemic diseases
Esophageal dysmotility when present in patients with connective tissue diseases is usually manifested by absent peristalsis 16 . All patients who underwent HRM had absent peristalsis in our series. However, they might represent biased referrals since they were all very symptomatic. Clozapine usage and myasthenia gravis also be associated with absent peristalsis as seen in our cases 12,19 .

Group 4 -dysphagia
Esophageal hypermotility and hypomotility may be both causes for functional dysphagia 30 . Both types of motility were found in our series. Esophagogastric junction outflow obstruction is a common cause of dysphagia after a Nissen fundoplication 28 . This diagnosis was found in 33% of the patients evaluated in this series as it is a common cause of postoperative dysphagia 29 .

CONCLUSIONS
We studied a water-perfused with permanent catheters HRM system with unique peristaltic pump and helicoidal sensor distribution. It is a low-cost (US$ 20,000) alternative do solid state system (US$ 60,000). The normal values determined for this system were discriminatory of most abnormalities in esophageal motility seem in clinical practice.