Applying High-Resolution Impedance Manometry for Detecting Swallowing Change in Anterior Cervical Spine Surgery Patients

Abstract

Background: Objectively detecting perioperative swallowing changes is essential for differentiating the reporting of subjective trouble sensations in patients undergoing anterior cervical spine surgery (ACSS). Swallowing indicates the transmission of fluid boluses from the pharynx (velopharynx, oropharynx, and hypopharynx) through the upper esophageal sphincter (UES). Abnormal swallowing can reveal fluid accumulation at the pharynx, which increased the aspiration risk. However, objective evidence is limited. High-resolution impedance manometry (HRIM) was applied for an objective swallowing evaluation for a more detailed analysis. We aimed to elucidate whether HRIM can be used to detect perioperative swallowing changes in patients undergoing ACSS.

Methods: Fourteen patients undergoing elective ACSS underwent HRIM with the Dysphagia Short Questionnaire (DSQ, score: 0-18) preoperatively (PreOP), on postoperative at day 1 (POD1), and postoperative at day seven (POD7). We calculated hypopharyngeal and UES variables, including hypopharyngeal mean peak pressure (PeakP) and UES peak pressure, representing their contractility (normal range of PeakP, 69-280 mmHg; peak pressure, 149-548 mmHg). The velopharynx-to-tongue base contractile (VTI) was also calculated (normal range, 300-700 mmHg.s.cm), indicating contractility. The swallowing risk index (SRI) from HRIM combined with four hypopharyngeal parameters, including PeakP, represents the global swallowing function (normal range, 0-11). A higher SRI value indicated higher aspiration.

Results: SRI was significantly higher on POD1 (10.88 ± 5.69) than PreOP (6.06 ± 3.71) and POD7 (8.99 ± 4.64). In all patients, PeakP was significantly lower on POD1 (61.8 ± 18.0 mmHg) than PreOP (84.9 ±34.7 mmHg) and on POD7 (75.3 ± 23.4 mmHg). The UES peak pressure was significantly lower on POD1 (80.4 ± 30.0 mmHg) than PreOP (112.9 ± 49.3 mmHg) and on POD7 (105.6 ± 59.1 mmHg). Other variables, including VTI, did not change significantly among the three time points. DSQ scores were 1.36, 3.43, and 2.36 at PreOP, POD1, and POD7 respectively.

Conclusions: With similar trends in DSQ and SRI, swallowing was significantly decreased on POD1 because of decreased hypopharyngeal and UES contractility but recovered to the preoperative state on POD7 after ACSS. Applying HRIM is superior to DSQ in detecting mechanisms and monitoring the recovery from swallowing dysfunction.

Clinical trial registration: The study was registered at ClinicalTrials.gov (NCT03891940).

Keywords: anterior cervical spine surgery; high-resolution impedance manometry; hypopharynx; perioperative swallowing physiology; upper esophageal sphincter.

Figure 1

Swallowing mechanisms of bolus through the oral cavity into the esophagus. The red pattern in (B–D) depicts the bolus in the same way that does in the (A). (A) The bolus is kept in the oral cavity, initiating the swallowing process. The figure in the dialog box below the pharynx illustrates that the pharynx includes the velopharynx, oropharynx and hypopharynx. The base of tongue is part of the oropharynx, and usually not visible when the mouth is open. (B) During the pharyngeal phase, the velopharynx, oral cavity, and larynx are sealing, and the bolus is transmitted through the pharynx and into the esophagus by pharyngeal peristalsis. (C) Airway protection is essential during the swallowing process, which includes tilting back of epiglottis, closing the laryngeal vestibule, trucking of the sealed airway under the tongue base from the bolus path, and the neuronal suppression of respiration while the bolus passes through the pharynx. (D) As the bolus passing into the esophagus, the airway reopens.

Figure 2

Swallow function recorded by High-Resolution Impedance Manometry (HRIM). The HRIM tube is shown in a patient's pharyngeal segment.

Figure 3

Swallowing function assessment via High -Resolution Impedance Manometry (HRIM). (A) Illustrative example of our data from the pressure sensors on the HRIM catheter (y-axis) over time (x-axis). The graph shows the oropharyngeal pressure topography, from the velopharynx to the tongue base, hypopharynx, and into the upper esophageal sphincter (UES). The high-pressure zone is the UES. The impedance channels from the velopharynx into the esophagus are indicated by white horizontal lines. Effective oropharyngeal muscle contraction relies on bolus transmission, during which the impedance level decreases. (B) Illustrative example of measurement of the parameters of hypopharyngeal and upper esophageal sphincter (UES) pressures. The upper red line represents the pressure waveform recorded at the hypopharynx during the swallow (apogee + 1 cm). The lower red line represents the UES pressure waveform, constructed from pressures recorded at the maximum UES pressure position over time. The mean pre-deglutitive UES basal pressure (UES-BP), UES integrated relaxation pressure (UES-IRP), and post-deglutitive UES peak pressure (UES-PeakP) can be identified at the lower red lines. (C) Illustrative example of measurement of the parameters of hypopharyngeal and upper esophageal sphincter admittance. Admittance (S) is the inverse product of impedance (Ω), i.e., S = 1/Ω. Admittance increases with bolus distension of the hypopharynx and UES. The maximum admittance within the UES (Max UES Adm) is represented by the maximum cross-sectional area of the lumen. The lower white line represents the UES admittance waveform, which is constructed from impedance recorded at the Pmax position over the swallowing period. The upper white line represents the admittance waveform at the hypopharyngeal position during the swallow (apogee +1 cm). (D) Illustrative example of measurement of bolus presence time (BPT) and upper esophageal sphincter (UES) open time. The lower section of the graph represents the UES region. The red line represents the UES pressure waveform, which is constructed from pressures recorded at the Pmax position over time. The white line represents the admittance waveform. UES open time was calculated from UES admittance and the pressure waveform, which were used together to define the onset of UES opening (based on the admittance upstroke in the UES), and UES closure (based on the pressure upstroke in the UES). The upper section of the graph represents the hypopharynx region (apogee + 1 cm). The red line represents the hypopharyngeal pressure waveform, and the white line represents the admittance waveform. The UES admittance level at the time of closure was used as the threshold to commence the hypopharyngeal admittance recording. The period when hypopharyngeal admittance exceeded this threshold was defined as the bolus presence time (BPT). (E) Illustrative example of measurement of the hypopharyngeal parameters. The white line indicates the maximum admittance (Max Adm) in the hypopharynx region. The red line indicates the mean value of the hypopharyngeal peak pressure (Mean Peak) in the hypopharynx region. Distension-contraction latency (DCL) reflects the time of maximum bolus distension and maximum contraction of the hypopharynx during the swallow. Hypopharyngeal intrabolus distension pressure (IBP) is defined as the pressure at maximum distension (at the position of Max Adm), 1 cm proximal to the UES apogee. The upper esophageal sphincter (UES) apogee is defined by visualization of the orad movement of the UES high-pressure zone to determine the highest position of the proximal edge of the high-pressure zone during swallowing. The Pmax position is defined as the position at the maximum pressure of UES.

Figure 4

Swallowing Risk Index (SRI) and associated hypopharyngeal parameters changes at three time points. The three time points are PreOP (preoperative day), POD1 (postoperative day 1), and POD7 (postoperative day 7). The formula to calculate SRI is (IBP × BPT)/(DCL × PeakP) ×100. (A–E) Presented the error bar of IBP, BPT, DCL, PeakP, and SRI at PreOP, POD1 and POD7, respectively. *P < 0.05; **P < 0.01. SRI, Swallowing risk index; IBP, intrabolus pressure (mmHg); BPT, bolus present time (s); DCL, hypopharyngeal distention contraction latency (s); PeakP: hypopharyngeal mean peak pressure (mmHg).