11.JCAHO. EC Revisions approved, annual equipment PM dropped. Environ Care News 2001;4:1, 3, 9.

12.JCAHO. Hospital Accreditation Standards. Oakbrook Terrace, IL: Joint Commission Resources; 2005.

13.Stiefel RO. Developing an effective inspection and preventive maintenance program. Biomed Instrument Technol 2002;36: 405–408.

14.Fennigkoh L, Smith B. Clinical equipment management. Plant, Technology & Safety Management Series Number 2, Chicago (IL): JCAHO; 1989.

15.Maxwell J. Prioritizing verification checks and preventive maintenance. Biomed Instrument Technol 2005;39:275– 277.

16.Ridgway MG. Personal communication. 2005.

17.Baker T. Journal of Clinical Engineering Roundtable: Debating the medical device preventive maintenance dilemma and what is the safest and most cost-effective remedy. J Clin Eng 2003;28:183–190.

18.ASHE. Maintenance Management for Medical Equipment. Chicago, IL: American Hospital Association; 1996.

19.AAMI. Recommended Practice for Medical Equipment Management Program. ANSI/AAMI EQ 56:1999. Arlington, VA: AAMI; 1999.

20.NFPA. NFPA 99, Standard for Health Care Facilities. Quincy (MA): NFPA; 2005.

21.Moubray J. Reliability-Centered Maintenance. New York: Industrial Press; 1997.

22.Ridgway MG. Analyzing planned maintenance (PM) inspection data by failure mode and effect analysis methodology. Biomed Instrument Technol 2003;37:167–179.

23.Acosta J. Data-driven PM Intervals. Biomed Instrument Technol 2000;34:439–441.

24.JCAHO. Data-driven medical equipment maintenance. Environ Care News 2000;3:6–7.

25.Ridgway MG. Making peace with the PM police. Healthcare Technol Manag 1997; Apr: 44.

26.ECRI. Maintaining life support and non-life support equipment. Health Devices 2004;33(7):244–250.

27.AAMI. JCAHO connection. Questions on life support equipment and NPSG # 6. Biomed Instrument Technol 2005;39: 284.

28.Cohen T. Computerized Maintenance Management Systems for Clinical Engineering. Arlington (VA): AAMI; 2003.

29.Cohen T, Cram N. Chapter 36. Computerized maintenance management systems. In: Dyro JF, editor. Clinical Engineering Handbook Burlington (MA): Elsevier Academic Press; 2004;.

30.AHA. Maintenance Management for Medical Equipment. Chicago, IL: American Hospital Association; 1988.

31.Glouhove M, Kolitsi Z, Pallikarakis N. International survey on the practice of clinical engineering: Mission, structure, personnel, and resources. J Clin Eng 2000;25:269–276.

32.Guerrant S. A sticker is worth a thousand words. 24 7 44, March 2003.

33.Ridgway MG. Masterplan’s Medical Equipment Management Program. Chatsworth (CA): Masterplan; 2005.

See also CODES AND REGULATIONS: MEDICAL DEVICES; SAFETY PROGRAM,

HOSPITAL.

ERG. See ELECTRORETINOGRAPHY.

ERGONOMICS. See HUMAN FACTORS IN MEDICAL

DEVICES.

ESOPHAGEAL MANOMETRY

229

ESOPHAGEAL MANOMETRY

VIC VELANOVICH

Henry Ford Hospital

Detroit, Michigan

INTRODUCTION

The purpose of the esophagus is to act as a conduit for food from the mouth to the stomach. This is an active process that is initially a conscious act with chewing and swallowing, then becomes unconscious when the bolus of food enters the esophagus. As part of this process, the esophageal musculature acts to propagate the food bolus to the stomach and to prevent reflux of gastric contents to the esophagus to protect the esophagus itself. There are several disease processes of the esophagus for which the assessment the esophageal musculature function would contribute to the diagnosis and management. This assessment is done indirectly through the measurement of intraesophageal pressures. This pressure measurement is accomplished with esophageal manometry (1).

ESOPHAGEAL ANATOMY AND PHYSIOLOGY

The esophagus is, in essence, a muscular tube that connects the mouth to the stomach. The esophagus anatomically starts in the neck, traverses the thorax, and enters into the abdomen to join the stomach. It is 20–25 cm in length, with the start of the esophagus being the upper esophageal sphincter and the end being the gastroesophageal junction. The upper esophageal sphincter is primarily made up of the cricopharyngeus muscle attached to the cricoid cartilage anteriorly. The musculature of the upper esophagus is made of striated muscle, and this transitions to smooth muscle in the lower esophagus. The esophagus is made up of three primarily layers: the inner-mucosa, the middle-submucosa, and the outer-muscle layer. The muscle layer is made up of an inner-circular muscle layer and an outer-longitudinal layer. At the inferior end of the esophagus is the lower esophageal sphincter. This is not a true anatomical sphincter, but rather a physiological high pressure zone that is the cumulation of thickening of the distal 5 cm of the esophageal musculature, the interaction of the esophagus with the diaphragmatic hiatus, and at 2 cm of intraabdominal esophagus. The lower esophageal sphincter should not be confused with the gastroesophageal junction, which is the entrance of the esophagus to the stomach, nor with the Z line, which is the transition of the esophageal squamous mucosa to the glandular gastric mucosa.

The lower esophageal sphincter is tonically contracted during rest to prevent reflux of gastric contents into the esophagus. It relaxes with a swallow. Swallowing is divided into an oral stage, pharyngeal stage, and esophageal stage. The oral and pharyngeal stage prepare food by chewing, the tongue pushing the food bolus to the pharynx, the soft palate is pulled upward, the vocal cords are closed and the epiglottis covers the larynx, the upper esophageal sphincter relaxes, and the contraction of the pharyngeal

230 ESOPHAGEAL MANOMETRY

muscles initiate the primary peristaltic wave. The esophageal stage consists of a peristaltic wave that pushes the food bolus to the stomach. There are primary peristaltic waves, which are initiated by the pharynx with a swallow. Secondary peristaltic waves are initiated within the esophagus due to distention of the esophagus with food. As the bolus reaches the lower esophagus, the lower esophageal sphincter relaxes.

INDICATIONS FOR ESOPHAGEAL MANOMETRY

Indications for esophageal manometry include the following five problems. (1) Dysphagia, to assess for an esophageal motility disorder, such as achalasia or nutcracker esophagus. It is important that mechanical causes of dysphagia, such as cancer, have been excluded. (2) Gastroesophageal reflux disease, not for primary diagnosis, but for possible surgical planning. (3) Noncardiac chest pain, which may be of esophageal origin. (4) Exclusion of generalized gastrointestinal disease (e.g., scleroderma or chronic idiopathic pseudoobstruction), and exclusion of an esophageal etiology for anorexia nervosa. (5) Determination of lower esophageal sphincter location for proper placement of an esophageal pH probe (2).

EQUIPMENT

The basic equipment used for manometry is the manometry catheter, infusion system (for water perfused systems), transducers, Polygraf or A/D converter, and computer with appropriate software (Fig. 1).

Esophageal manometry catheters come in two basic types: water perfused and solid state. The water perfused catheter contains several hollow tubes. Each tube has one side opening at a specific site on the catheter. The openings are at various points around the circumference of the catheter. There is a 4 cm catheter with side holes placed 5 cm apart, and a 8 cm catheter with 4 lumens placed 1 cm apart in the most distal end of the catheter, then 5 cm apart for the next proximal 4 lumens. The radial spacing helps to accurately measure upper and lower esophageal sphincter pressures that are asymmetrical. The water perfused catheters require an infusion system. The manometric pump uses regulated compressed nitrogen gas to deliver distilled water through the channels of the catheter. The pressurized water from each channel is connected to a single opening in the catheter within the patient’s esophagus. The pressure changes are transmitted to the transducer, and these pressure changes are recorded and charted by a computer with the appropriate software.

The solid-state catheter has internal microtransducers. These directly measure intraesophageal pressures and contractions. Some advantages are that the sensors respond faster, do not require that the patient lie down, and record pressures circumferentially. An additional advantage is that as these catheters do not require fluid containers, potential pitfalls with fluid disinfection are avoided. Some drawbacks are that they are delicate, more expensive to purchase and repair, and are prone to baseline drift. As with the water-perfused system, the

Figure 1. The esophageal manometry console with computer. (Courtesy of Medtronic Corp., Minneapolis, MN.)

solid-state system requires that the catheter be connected to a computer console for recording and storing pressure data.

Additional items are needed. These include a manometer calibration tube for calibrating the solid-state catheter, a viscous lidocaine, a lubricating jelly, tissues, tape, an emesis basin, a syringe, a cup of water, a penlight, and tongue blades.

CONDUCT OF THE TESTING

Prior to the procedure, the pressure channels require calibration and connection to the computer console. The patient sits upright and one of the nares is anesthetized. Lubricating jelly is applied to the catheter and inserted through one the nares into the pharynx. The patient is asked to swallow and the catheter advance into the esophagus to the stomach. The catheter is advanced for 65 cm to insure all the sensor ports are within the stomach. If using water-perfused catheters, the patient is moved to the supine position. If using solid-state catheters, the patient is kept in the semi-Fowler position, which is the head and torso of the patient at a 458 angle bent at the waist.

The esophageal motility study consists of (1) the lower esophageal sphincter study, (2) esophageal body study, and (3) the upper esophageal sphincter study. Before beginning the study, insure that all sensor ports are within the stomach by having the patient take a deep breath and

watching the motility recording. It should show a smooth tracing with a pressure increase during inspiration. An alternative method of determining that all side holes are within the stomach is to apply gentle pressure to the epigastrium to confirm that there is a simultaneous increase in the recorded pressure. When all channels are within the stomach, a gastric baseline is set to establish a reference for pressure changes.

The lower esophageal sphincter study measures sphincter pressure, length, location, and relaxation. This is done using either the ‘‘station pull-through’’ or ‘‘slow continuous pull through’’ methods. With the station pull-through technique, the catheter is slowly withdrawn through the sphincter at 1 cm increments while looking for changes in pressure. When the first channel enters the sphincter, pressure will increase from baseline by at least 2 mmHg (0.266 kPa). This identifies the lower border of the sphincter. As the catheter is continued to be pulled back, the ‘‘respiratory inversion point’’ is reached. This is the transition from the intraabdominal to the intrathoracic esophagus. With inspiration, the catheter will record positive pressures within the abdomen, but negative pressures within the thorax. Inferior to the respiratory inversion point is the lower esophageal sphincter high pressure zone. This is the physiologic landmark used to perform pressure measurements and relaxation studies. When the distal channel passes through the upper border of the lower esophageal sphincter, the pressure should decrease from baseline. The length traveled from the lower to the upper

ESOPHAGEAL MANOMETRY

231

Figure 2. Lower esophageal sphincter profile as determined by esophageal manometry. (Courtesy of Medtronic Corp., Minneapolis, MN.)

border of the sphincter measures the sphincter length. The slow continuous pull-through method is done while the catheter is pulled back continuously, while pressures are being recorded. The catheter is pulled back 1 cm every 10 s. These methods lead to identifying the distal and proximal borders of the sphincter, overall sphincter length, abdom inal sphincter length, and resting sphincter pressure (Fig. 2). Sphincter relaxation involves observing the response of the lower esophageal sphincter to swallowing (Fig. 3). This is done by asking the patient to swallow 5 mL of water with the catheter positioned in the high

Figure 3. Manometric tracings of lower esophageal sphincter relaxation. (Courtesy of Medtronic Corp., Minneapolis, MN.)

232 ESOPHAGEAL MANOMETRY

Figure 4. Manometric tracings of esophageal body peristalsis. (Courtesy of Medtronic Corp.,

Minneapolis, MN.)

pressure zone. The pressures are recorded with the swallow. Accurate determination of lower esophageal relaxation requires a Dent sleeve. Although this can be measured using side holes, artifact can be created.

The study of the esophageal body determines the muscular activity of the esophagus during swallowing. There are four components of the study: (1) peristalsis, (2) amplitude of contractions, (3) duration of contraction, and (4) contraction morphology (Fig. 4). These measurements are made with the distal pressure sensor positioned 3 cm superior to the upper border of the lower esophageal sphincter. The patient takes 10 wet swallows with 5 mL of room temperature water. Esophageal body amplitude is the force with which the esophageal musculature contracts. The amplitude is measured from baseline to the peak of the contraction wave. Duration is the length of time that the esophageal muscle remains contracted. It is measured from the point at which the major upstroke of the contraction begins to the point at which it ends. Velocity is a measurement of the time it takes for a contraction to migrate down the esophagus (unit of measure is cm s 1). These measurements are used to determine esophageal body motility function.

The study of the upper esophageal sphincter includes (1) resting pressure, (2) relaxation, and (3) cricopharyngeal coordination (Fig. 5). The study is done by withdrawing the catheter in 1 cm increments until the upper esophageal sphincter is reached. This is determined when the pressure measured rises above the esophageal baseline. The cathe-

ter is positioned so that the first sensor is just superior to the sphincter and the second sensor is at the proximal border of the sphincter. The remaining channels are in the body of the esophagus. The patient is given 5 mL of water for wet swallows. The catheter is withdrawn during this process. However, it should be emphasized that the upper esophageal sphincter is quite asymmetric; therefore, pressure readings are meaningless unless the exact position of the side holes are known.

This concludes the study and the catheter is removed from the patient.

INTERPRETATION OF THE TEST

Esophageal motility disorders are categorized into primary, secondary, and nonspecific (3). Primary esophageal disorders are those in which the dysfunction is limited only to the esophagus. Examples of these include the hypotensive lower esophageal sphincter associated with gastroesophageal reflux disease, achalasia, diffuse esophageal spasm, hypertensive lower esophageal sphincter, and nutcracker esophagus. Secondary esophageal motility disorders are those in which the swallowing occurs as a result of a generalized disease. Examples of these include collagenvascular disease (e.g., scleroderma), endocrine and metabolic disorders (diabetes mellitus), neuromuscular diseases (myasthenia gravis, multiple sclerosis, and Parkinson’s disease), chronic idiopathic intestinal pseudo-obstruction,