Key points

Introduction

High-resolution manometry (HRM) is the current gold standard technique to assess esophageal motility. It uses closely spaced pressure sensors to create a dynamic representation of pressure change along the entire length of the esophagus. Data acquisition is easier than with conventional manometry and interpretation is facilitated by esophageal pressure topography (Clouse) plots.

Along with the technological innovation, an international consensus process has evolved over recent years to define esophageal motility disorders using HRM, Clouse plots, and standardized metrics. This classification, titled the Chicago Classification, was firstly published in 2009 and was subsequently updated in 2012. It was intended to be applied to HRM studies performed in a supine position with 5-mL water swallows and for patients without previous esophagogastric surgery. The 2012 version of the Chicago Classification focused entirely on redefining esophageal motor disorders associated with dysphagia in HRM terms; it did not provide guidance on the assessment of the esophagogastric junction (EGJ) at rest or upper esophageal sphincter (UES) function. Since that publication, substantial further research has been presented and published, intended to improve the diagnostic accuracy and clinical utility of the Chicago Classification. In recognition of this, the international HRM Working Group met in Chicago in May 2014 in conjunction with Digestive Disease Week to discuss these new data in the context of working toward an update of the Chicago Classification (v3.0). This article presents a brief summary of these discussions and proposals to work toward the Chicago Classification 3.0; a process due to be completed in early 2015.

Introduction

High-resolution manometry (HRM) is the current gold standard technique to assess esophageal motility. It uses closely spaced pressure sensors to create a dynamic representation of pressure change along the entire length of the esophagus. Data acquisition is easier than with conventional manometry and interpretation is facilitated by esophageal pressure topography (Clouse) plots.

Along with the technological innovation, an international consensus process has evolved over recent years to define esophageal motility disorders using HRM, Clouse plots, and standardized metrics. This classification, titled the Chicago Classification, was firstly published in 2009 and was subsequently updated in 2012. It was intended to be applied to HRM studies performed in a supine position with 5-mL water swallows and for patients without previous esophagogastric surgery. The 2012 version of the Chicago Classification focused entirely on redefining esophageal motor disorders associated with dysphagia in HRM terms; it did not provide guidance on the assessment of the esophagogastric junction (EGJ) at rest or upper esophageal sphincter (UES) function. Since that publication, substantial further research has been presented and published, intended to improve the diagnostic accuracy and clinical utility of the Chicago Classification. In recognition of this, the international HRM Working Group met in Chicago in May 2014 in conjunction with Digestive Disease Week to discuss these new data in the context of working toward an update of the Chicago Classification (v3.0). This article presents a brief summary of these discussions and proposals to work toward the Chicago Classification 3.0; a process due to be completed in early 2015.

Metrics and swallow pattern characterization

The Chicago Classification is based on scoring of 10 5-mL water swallows performed in supine position. EGJ relaxation, esophageal contractile activity, and esophageal pressurization are evaluated for each swallow. However, a major indication for manometric studies is in the evaluation of patients for potential antireflux surgery and some description of EGJ morphology and quantification of contractility is desirable. Hence, the incorporation of simple metrics relevant to these aspects of motility will be incorporated into Chicago Classification v3.0. Proposed metrics under discussion include mean inspiratory pressure, mean expiratory pressure, the extent and variability of the separation between the lower esophageal sphincter (LES) and crural diaphragm (CD separation), and the EGJ contractile integral (CI), all of which have been used in publications. However, discrepancies exist in the details of calculation methodology for these metrics, the strength of data supporting their utility, and their normative ranges among HRM devices, all of which are important limitations meriting further consideration.

Esophagogastric Junction Morphology and Deglutitive Relaxation

With HRM and Clouse plots, the relative localization of the 2 constituents of the EGJ, the LES and the CD, define EGJ morphologic subtypes. This feature of EGJ morphology is fundamental, and is likely pertinent to its functional integrity. With type I EGJ morphology, there is complete overlap of the CD and LES with no spatial separation evident on the Clouse plot ( Fig. 1 ) and no double peak on the associated spatial pressure variation plot. With type II EGJ morphology, the LES and CD are separated (double-peaked spatial pressure variation plot), but the nadir pressure between the 2 peaks does not decline to gastric pressure; the separation between the pressure peaks is less than 3 cm. With type III EGJ morphology, the LES and CD are clearly separated as shown by a double-peaked spatial pressure variation plot and a nadir pressure between the peaks equal to or less than gastric pressure; with type IIIa the pressure inversion point remains at the CD level, whereas in type IIIb it is located at the LES level. However, the separation between LES and CD may fluctuate in the course of the study and in those instances this should be reported as a range. Hence in reporting the LES-CD, the range of observed LES-CD separation observed throughout the study is reported for types II and III EGJ morphology.

EGJ morphology subtypes. For each panel the instantaneous spatial pressure variation plot corresponding with the red line on the pressure topography plot is shown by the black line on the right. The 2 main EGJ components are the LES and the CD, which cannot be independently quantified when they are superimposed, as with a type I EGJ ( A ). The respiratory inversion point (RIP), shown by the horizontal dashed line, is at the proximal margin of the EGJ. During inspiration (I), EGJ pressure increases, whereas it decreases during expiration (E). Type II EGJ pressure morphology is shown in ( B ). Note the 2 peaks on the instantaneous spatial pressure variation plot; the nadir pressure between the peaks is greater than the intragastric pressure. ( C , D ) Type III EGJ pressure morphology defined as the presence of 2 peaks of the instantaneous spatial pressure variation plot with a nadir pressure between the peaks equal to or less than intragastric pressure. The RIP is proximal to the CD with type IIIa ( C ), whereas it is proximal to the LES in IIIb ( D ).

The simplest measurement of baseline EGJ pressure is an average pressure for 3 normal respiratory cycles, ideally in a quiescent portion of the recording, remote from either spontaneous or test swallows in order to exclude the effect of the postdeglutitive contraction. The inspiratory EGJ pressure is the mean maximal inspiratory EGJ pressure and the expiratory EGJ pressure is the average EGJ pressure midway between inspirations. Normative values are reported in Table 1 .

Table 1

Reported normal ranges of basal EGJ pressures for control subjects in a supine position among studies and among manometric devices

Author	Equipment	Number of Controls	End-expiratory EGJ Pressure (mm Hg)
Pandolfino et al, 2009	Given Imaging	75	Mean (±2 SD) = 18 (4–33)
Sweis et al, 2011	Given Imaging	23	Median (5th–95th percentile) 19 (5–38)
Niebisch et al, 2013	Given Imaging	68	Median (5th–95th percentile) 15 (3–31)
Weijenborg et al, 2014	Given Imaging	50	Median (5th–95th percentile) 15 (3–31)
Bogte et al, 2013	MMS (solid state; Unisensor AG)	52	Median (5th–95th percentile) 31 (9–51)
Kessing et al, 2014	MMS (water-perfused system)	50	Median (5th–95th percentile) 10 (3–30)

Abbreviation: MMS, medical measurement systems; SD, standard deviation.

During swallowing, EGJ relaxation is evaluated using the integrated relaxation pressure (IRP), which has been (and will continue to be) defined as the mean of the 4 seconds (contiguous or noncontiguous) of maximal deglutitive relaxation in the 10-second window beginning at deglutitive UES relaxation. The IRP is referenced to gastric pressure. However, normal values depend strongly on the specific manometric hardware used, making this an important diagnostic consideration ( Table 2 ).

Table 2

Reported normal ranges of IRP for control subjects in a supine position among studies and among manometric devices

Author	Equipment	Number of Controls	IRP (mm Hg) 95th Percentile = ULN
			Mean	Median (ULN)
Ghosh et al, 2007	Given Imaging	75	9	8 (15)
Sweis et al, 2011	Given Imaging	23	4	3 (9)
Niebisch et al, 2013	Given Imaging	68	9	9 (17)
Weijenborg et al, 2014	Given Imaging	50	8	7 (16)
Bogte et al, 2013	MMS (solid state; Unisensor AG)	52	13	12 (28)
Kessing et al, 2014	MMS (water-perfused system)	50	8	7 (19)

Abbreviation: ULN, upper limit of normal.

Deglutitive Peristaltic Vigor and Pattern

Metrics are used to evaluate esophageal contractile function are the distal esophageal integral (DCI) and the distal latency (DL) ( Fig. 2 , Table 3 ). They are used to characterize each of the 10 5-mL test swallows ( Table 4 ). Contractile vigor is summarized using the DCI. This metric applies an algorithm to quantify the contractile pressure exceeding 20 mm Hg for the region spanning from the transition zone to the proximal aspect of the EGJ. As such, it encompasses the space-time domain of the second and third contractile segments defined by Clouse and provides a single number summarizing contractile vigor in this region. Cutoff values between diagnostic categories depend on the manometric hardware and software used (see Table 3 ). A DCI between 450 and 8000 mm Hg·s·cm is considered normal. Based on the conclusions of a study on ineffective contractile contraction, the international HRM Working Group is inclined to define failed and weak contraction based on the DCI value in the Chicago Classification v3.0. The current proposal is that a contraction with a DCI less than 100 mm Hg·s·cm defines a failed contraction and a weak contraction is defined as a DCI greater than 100 mm Hg·s·cm but less than 450 mm Hg·s·cm. Both failed and weak contractions are ineffective. In addition, a DCI greater than or equal to 8000 mm Hg·s·cm defines hypercontractility.

Normal esophageal peristaltic contraction. The IRP is measured during the deglutitive window, indicated by the brown bracket. The IRP is the lowest pressure for 4 seconds (contiguous or noncontiguous), identified by the white boxes within the deglutitive window. The distal contractile integral (DCI) is measured from the transition zone to the EGJ, equating to the product of the amplitude times the duration times the length of the contraction located within the dashed box. The contractile deceleration point (CDP; black dot ) represents the inflexion point in the velocity of contractile front propagation. DL is measured from UES relaxation ( dashed vertical line ) to the CDP.

Table 3

Reported normal ranges of distal contractile integral (DCI) and DL for control subjects in a supine position among studies and among manometric devices

Author	Equipment	Number of Controls	Median DCI (5th–95th Percentile) (mm Hg·s·cm)	Median DL (5th Percentile) (s)
Xiao et al, 2012	Given Imaging	75	1612 (448–4721)	5.8 (4.3)
Niebisch et al, 2013	Given Imaging	68	1485 (420–4236)	6.8 (5.4)
Weijenborg et al, 2014	Given Imaging	50	834 (178–2828)	6.8 (5.4)
Bogte et al, 2013	MMS (solid state; Unisensor AG)	52	1008 (186–3407)	6.1 (5.0)
Kessing et al, 2014	MMS (water-perfused system)	50	970 (142–3675)	7.4 (6.2)

Table 4

Characteristics of deglutitive peristaltic function proposed for the Chicago Classification v3.0 (note that contraction pattern is not scored with failed or weak vigor)

Contractile Vigor
Failed	DCI <100 mm Hg·s·cm
Weak	DCI >100 mm Hg·s·cm, but <450 mm Hg·s·cm
Ineffective	Failed or weak
Normal	DCI >450 mm Hg·s·cm but <8000 mm Hg·s·cm
Hypercontractile	DCI ≥8000 mm Hg·s·cm
Contraction Pattern
Premature	DL <4.5 s
Fragmented	Large break (>5 cm) in the 20 mm Hg isobaric contour, but not failed and DCI >450 mm Hg·s·cm
Intact	Not achieving the diagnostic criteria listed earlier
Intrabolus Pressure Pattern (30 mm Hg Isobaric Contour Referenced to Atmospheric)
Panesophageal pressurization	Uniform pressurization of >30 mm Hg extending from the UES to the EGJ
Compartmentalized esophageal pressurization	Pressurization of >30 mm Hg extending from the contractile front to the EGJ
EGJ pressurization	Pressurization restricted to zone between the LES and CD in conjunction with LES-CD separation
Normal	No bolus pressurization >30 mm Hg

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