Reduced Endotracheal Tube Cuff Pressure to Assess Dysphagia After Anterior Cervical Spine Surgery.

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RIMARY

RESEARCH

Reduced Endotracheal Tube Cuff Pressure to Assess Dysphagia After Anterior Cervical Spine Surgery Izabela Kowalczyk, BHSc,*w Won Hyung A. Ryu, MSc,z Doron Rabin, MD, FRCS(C),y Miguel Arango, MD,8 and Neil Duggal, MD, MSc, FRCS(C)*z

Study Design: This was a prospective, randomized control pilot study.

timepoints (P < 0.01). DDI scores Z10 related to dysphagia were in 59% of patients at 24 hours, 35% at 6 weeks, 24% at 3 months, and 18% at 6 months.

Objective: The aim of this study was to determine whether continuous monitoring and adjustment of the endotracheal tube cuff pressure (ETTCP) to 15 mm Hg during ACSS would alter the incidence of postoperative dysphagia.

Conclusions: This study suggests decreased ETTCP has no effect on the prevalence of dysphagia. The incidence of dysphagia decreases over time and normalizes by 6 months postsurgery.

Summary of Background Data: Postoperative dysphagia is a recognized potential complication of anterior cervical spine surgery (ACSS). Recent findings on preventive measures suggest that certain intraoperative practices may minimize this complication. Methods: Fifty patients undergoing ACSS, arthroplasty, or fusion, completed routine lateral cervical preoperative plain films and questionnaires [Dysphagia Disability Index (DDI), BazazYoo Dysphagia Score (BYDS), and Short Form (36) Health Survey]. Patients were randomized into 2 groups: treatment group with ETTCP maintained at 15 mm Hg and control group with cuff pressure monitored without manipulation. Radiographs and questionnaires were obtained at 24 hours, 6 weeks, and 3 and 6 months postsurgery to assess soft tissue thickness and rates of dysphagia. Results: There were no significant differences between the groups in the soft tissue thickness or questionnaire scores at any timepoint (P > 0.05). Within-group analysis revealed treatment and control groups had a significantly higher 24-hour postoperative soft tissue thickness and questionnaire scores compared with follow-up measurements (P < 0.05). In the pooled group (n = 50), the 24-hour postoperative DDI, BYDS, and soft tissue thickness were significantly higher compared with all other Received for publication February 21, 2013; accepted October 1, 2013. From the *Department of Medical Biophysics; wCentre for Functional and Metabolic Mapping, Robarts Research Institute, Western University; zDepartment of Clinical Neurological Sciences; Neurosurgery, University Hospital, London Health Sciences Centre, London, ON, Canada; ySt. Luke’s Neurosurgical Associates, Bethlehem, PA; and 8Department of Anesthesiology, University Hospital, London Health Sciences Centre, London, ON, Canada. Supported by the AANS/CNS Section on Disorders of the Spine and Peripheral Nerves and Lawson Health Research Institute in support of this research. The authors declare no conflict of interest. Reprints: Neil Duggal, MD, MSc, FRCS(C), Division of Neurosurgery, University Hospital, LHSC, 339 Windermere Road, London, ON, Canada, N6A 5A5 (e-mail: [email protected]). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.

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Key Words: anterior cervical spine surgery, dysphagia, endotracheal tube cuff pressure, soft tissue swelling (J Spinal Disord Tech 2015;28:E552–E558)

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ysphagia is a common complaint after anterior cervical spine surgery (ACSS), with early postoperative incidence ranging from 30% to 70%.1–5 A number of recent interbody implants have been designed to provide a “zero profile,” avoiding a device footprint on the anterior surface of the vertebral body in the hope of avoiding postoperative dysphagia. Although growing anecdotal evidence highlights deglutition disorders as a significant postoperative complication, there is no clear definition or gold standard measurement to detect dysphagia. A recent systematic review of postoperative dysphagia described the inconsistencies in quantifying dysphagia as a potential source of variability in the reported incidence rates.5 Examples of measurement tools previously utilized include M.D. Anderson Dysphagia Inventory, Bazaz-Yoo Dysphagia Scale (BYDS), Dysphagia Disability Index (DDI), fiberoptic examination, and Modified Barium Swallow study.2–3,5–7 Bazaz et al1 prospectively analyzed dysphagia grading scores in 224 ACSS patients. Fifty percent, 17.7%, and 12.5% of patients noted swallowing difficulty, at 1 month, 6 months, and 12 months following surgery, respectively.1 Riley et al4 prospectively followed 454 anterior cervical discectomy patients using the Cervical Spine Outcomes Questionnaire, Short Form (36) Health Survey (SF-36), and Oswestry Neck Disability Scale. Dysphagia persisted in 21.5% and 21.3% of patients at 3 and 24 months, respectively. Patients reporting dysphagia 3 months postoperatively had lower physical health status and higher disability scores.4 Even with such variability in incidence, it is clear that dysphagia is a potential complication affecting a significant proportion of ACSS patients, which can be still evident at 2 years following surgery. J Spinal Disord Tech

Volume 28, Number 10, December 2015

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Findings on preventive measures for postoperative dysphagia suggest that endotracheal intubation may contribute to ischemic changes of the tracheal mucosa resulting in sore throat, hoarseness, and dysphagia.8–11 Sperry et al10 reported that in vivo cuff pressure increased from baseline of 15.2–43.2 mm Hg during anterior cervical discectomy and fusion (ACDF). Similarly, Apfelbaum et al11 observed that endotracheal tube cuff pressure (ETTCP) increased up to 52 mm Hg in 4 cadavers following anterior cervical retractor placement. This retrospective study also found that 6.8% of 250 patients undergoing ACSS without reduction of ETTCP experienced vocal cord paralysis.11 After introducing the simple procedure of deflating the ETTCP to 15 mm Hg, only 2% of patients experienced these palsies.11 Ratnaraj et al9 performed a randomized control trial on 51 patients where the intraoperative ETTCP was either actively adjusted to 20 mm Hg or unadjusted during ACSS. At 24 hours, longer retraction time correlated with development of dysphagia measured by a verbal analog scale.9 However, ETTCP did not correlate with the incidence of dysphagia.9 Although a small number of studies have examined the effect of increased ETTCP in causing dysphagia, no study has employed a randomized controlled trial with long-term follow-up using dysphagia-specific questionnaires (DDI, BYDS), an overall health survey (SF-36), and radiographic imaging (soft tissue swelling measurements). The purpose of this randomized control trial was to determine whether monitoring and adjustment of the ETTCP to 15 mm Hg during ACSS would alter the incidence of postoperative dysphagia.

METHODS Patients between 21 and 65 years of age requiring ACSS (ACDF or cervical arthroplasty) for management of radiculopathy and/or myelopathy were recruited. Exclusion criteria were: previous anterior neck surgery; anterior neck malignancy; tracheostomy; previous treatment for dysphagia; pregnancy, and medical comorbidities precluding surgery. A total of 50 consecutive single-level surgery patients consented to participate in the study, which was approved by the Health Sciences Research Ethics Board at The Western University. As part of preoperative workup, routine lateral cervical plain films were collected for each participant. Two trained research assistants, blinded to patient group assignment, measured the soft tissue at the index site. For preoperative images, measurement was from the junction between the anterior vertebral body and the posterior edge of any osteophytes present at the index site to the anterior edge of the tissue. Preoperative questionnaires including the DDI, BYDS, and SF-36 were collected. Subjective dysphagia scores were evaluated using the DDI. The responses were scored as “always” = 4, “sometimes” = 2, or “never” = 0 and summed for a total score. A DDI score Z10 was related to dysphagia.3 The BYDS is a widely used score and previously reported in prospective studies of 249 patients who underwent ACSS.1 The SF-36 provides estimates of functional health Copyright

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Reduced ETTCP to Assess Dysphagia After ACSS

and well-being scores as well as psychometrically based physical and mental health summary measures. The SF36 has been shown to be a valid and reliable measure of health status.12 Patients were randomized on the surgical day to the treatment or control group. All patients underwent identical anesthetic induction, maintenance, and reversal (Fig. 1). The surgical technique was standardized to a right-sided approach to the anterior cervical spine for all patients. The senior author performed all procedures and was blinded to the patient grouping. Intubation was always performed with a tube size of 8.5 for males and 7.5 for females. ETTCP was measured continuously in both groups following insertion of retractors below the longus colli muscles. The treatment group had the cuff pressure maintained at 15 mm Hg during the entire duration of the procedure. The control group had the cuff pressure monitored without manipulation. Following surgery, routine postoperative lateral cervical radiographs were obtained at 24 hours, 6 weeks, 3 months, and 6 months. Blinded research assistants measured the soft tissue swelling in ACDF patients from the anterior edge of the plate to the most anterior boundary of the tissue at the center of the previous disk space. In cervical arthroplasty patients, the measurement started at the anterior edge of the artificial disk to the most anterior boundary of the tissue. The interrater reliability was measured using the Pearson Product Moment Correlation Coefficient with a strong correlation of r = 0.95. Patients were asked to complete DDI, BYDS, and SF-36 questionnaires at 24 hours, 6 weeks, 3 months, and 6 months following surgery.

Statistical Analysis Descriptive statistics (age, sex, level of surgery, type of surgical management) were compared between groups. The primary outcome was the severity of dysphagia following surgery. Secondary outcomes included the overall health score and the change in anterior cervical soft tissue thickness on plain lateral radiographs. The percentage change in soft tissue thickness from preoperative films was calculated at each time interval using the following equation: % Change ¼ ðPostoperative soft tissue thicknessPreoperative soft tissue thicknessÞ 100 ðPreoperative soft tissue thicknessÞ

The Student t test was utilized to assess the significance of any between-group differences for the primary and secondary outcomes with an a level set at 0.05. Any within-group differences were compared using the analysis of variance (significance P < 0.05) followed by the Tukey post hoc analysis.

RESULTS Clinical Data The demographics for the treatment (47 ± 10 y; range, 34–71 y; 17 males) and control (46 ± 10 y; range, www.jspinaldisorders.com |


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FIGURE 1. Methodology flowchart.

29–65 y; 20 males) groups are listed in Table 1. The groups did not differ significantly in age, sex, type, or level of surgery and, therefore, subsequent analyses did not control for these factors. No surgery (including anesthetic time) lasted over 2 hours and the duration of intubation and length of surgery were considered controlled variables.


Primary Outcomes: DDI and BYDS The primary outcome was the severity of postoperative dysphagia measured by the DDI and BYDS. Higher DDI and BYDS scores suggest greater subjective dysphagia. Although the treatment group had higher DDI and BYDS scores postoperatively, there were no significant differences between the groups at any time-point. Copyright

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TABLE 1. Demographic Data for the Treatment and Control Groups Subject

Treatment Group Control Group

No. participants 25 Age (mean ± SD) 47 ± 10 Sex Male 17 Female 8 Type of surgery ACD and fusion 16 ACD with artificial disk 9 Level of surgery C3–C4 4 C4–C5 4 C5–C6 11 C6–C7 4 C7–T1 2 Bazaz-Yoo Disability Score (mean ± SD) Preoperative 0.84 ± 1.49 24 h 2.88 ± 2.73 6 wk 1.14 ± 1.78 3 mo 1.10 ± 1.48 6 mo 1.25 ± 1.84 Dysphagia Disability Index (mean ± SD) Preoperative 4.56 ± 5.65 24 h 15.28 ± 13.49 6 wk 7.45 ± 8.99 3 mo 4.19 ± 5.44 6 mo 5.13 ± 6.93 Soft tissue swelling (mean ± SD) Preoperative 1.4 ± 0.5 24 h 1.9 ± 0.4 6 wk 1.4 ± 0.4 3 mo 1.4 ± 0.4 6 mo 1.4 ± 0.4

25 46 ± 10

P 0.69 0.34

20 5 0.40 13 12 0.69 2 4 12 7 0 0.58 ± 1.14 3.84 ± 3.02 1.83 ± 2.35 1.18 ± 1.94 0.89 ± 1.28

0.36 0.28 0.56 0.79 0.36

4.00 ± 4.27 19.00 ± 19.04 10.00 ± 11.58 6.55 ± 8.64 4.45 ± 6.64

0.39 0.54 0.63 0.37 0.23

1.5 ± 0.5 1.9 ± 0.3 1.5 ± 0.4 1.4 ± 0.5 1.3 ± 0.5

0.47 0.72 0.47 0.90 0.44

ACD indicates anterior cervical discectomy.

Mean scores for the DDI and BYDS are presented in Figures 2 and 3, respectively. P-values are presented in Table 1. Within-group comparisons illustrated that the treatment and control groups had a significantly higher 24-hour postoperative DDI score compared with their own preoperative scores (P = 0.004 and 0.001, respectively). The treatment group presented a significantly higher 24-hour postoperative BYDS score compared with the preoperative (P = 0.007) and 3-month value (P = 0.001). Similarly, the control group had a significantly higher 24-hour postoperative BYDS score compared with all other visits (P < 0.01).

FIGURE 2. Line graph representing the mean scores for the Dysphagia Disability Index (DDI) in the treatment and control groups. Higher scores suggest greater subjective dysphagia. No significant differences were found.

Within-group comparisons demonstrated the treatment and control groups had a significantly higher 24-hour postoperative soft tissue thickness compared with the preoperative and all follow-up visits (P < 0.05).

Pooled Group Analysis (n = 50) The analysis of variance of the pooled data from the treatment and control groups demonstrated significant changes in dysphagia scores (P < 0.0001). Specifically, the 24-hour postoperative DDI and BYDS questionnaire and the soft tissue thickness measurements were significantly higher compared with the preoperative and all follow-up timepoints (P < 0.01). A DDI score Z10 was related to dysphagia.3 DDI scores were Z10 in 59% of patients at 24 hours, 35% at 6 weeks, 24% at 3 months, and 18% at 6 months.

DISCUSSION Our study incorporated subjective measures of swallowing function and objective radiographic examination of

Secondary Outcomes: SF-36 and Soft Tissue Thickness Secondary outcomes were the overall health score (SF-36) and the change in the anterior cervical soft tissue thickness on plain lateral radiographs. There were no significant differences between the treatment and control groups for any subsections of the SF-36 or the overall health score (P > 0.05). Similarly, no significant differences were observed in the measurements of the soft tissue thickness between the groups at any timepoint (P > 0.05) (Fig. 4). Copyright

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FIGURE 3. Line graph representing the mean scores for the Bazaz-Yoo Dysphagia Score (BYDS) in the treatment and control groups. Higher scores suggest greater subjective dysphagia. No significant differences were found. www.jspinaldisorders.com |


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FIGURE 4. The average soft tissue thickness measurements from the lateral radiographs in the treatment and control groups. No significant differences were found.

soft tissue swelling to compare the effect of ETTCP in the development of postoperative dysphagia for patients undergoing ACSS. The literature would suggest that a controlled decrease in ETTCP may translate into lower incidence of postoperative dysphagia. Specifically, for our study, an ETTCP value of 15 mm Hg was predetermined as a balance between maintaining the airway and preventing potential aspiration while adequately decreasing excess force transmitted to the tracheal wall from the cuff. Our prospective randomized results suggest that a decreased ETTCP maintained at 15 mm Hg does not significantly lower dysphagia rates or decrease soft tissue swelling compared with the control group. Subsequently, our pooled data demonstrated highest rates of dysphagia in the first 24 hours postsurgery with lasting dysphagia affecting 18% of patients at 6 months postoperatively. ACSS for patients with cervical radioculopathy and/or myelopathy is the preferred surgical technique because of its relative safety and its ability to completely access the disk space and bilateral exiting nerve roots without manipulating the spinal cord. However, this anterior approach still carries potential risks, in particular postoperative dysphagia. Reported dysphagia rates after anterior cervical discectomy, whether followed by arthroplasty or fusion (with an anterior cervical plate), range from 30% to 70%.1–5,13 Disparity of the reported rates is likely due to variations in study design and in the measurement of dysphagia.5 Although the incidence of dysphagia remains varied in the literature, it is clear that patients undergoing ACSS are significantly affected by this problem, with reported lower overall physical health status and higher disability scores.4 Although the pathophysiology of postoperative dysphagia has not yet been conclusively identified, it may be multifactorial with contributing effects including: direct surgical trauma, injury to nerves, prominence of anterior instrumentation, scar formation, and soft tissue swelling.2,14 Increased



incidence of postoperative dysphagia has previously been associated with longer duration of intubation, higher cuff pressure during retractor placement, operations on Z2 levels, and a thicker profile of anterior cervical plates.3–4,7–9,15 One possible etiology of dysphagia stems from previous research studies in the field of anesthesia that reported a possible link between endotracheal intubation and ischemic changes of the tracheal mucosa.8–11 Given that inflation of endotracheal cuff transmits force to the surrounding soft tissue structures, overinflation may lead to ischemia of the mucosal vessels, ciliary loss, and laryngotracheal injuries.16–18 Furthermore, patients undergoing ACSS may experience direct esophageal compression between the surgical retractors and the inflated cuff in the airway. This is supported by findings of Sperry et al10 who reported that in vivo cuff pressure increased from baseline of 15.2–43.2 mm Hg during ACDF. Our results showed no significant differences in the incidence of dysphagia between the treatment group with decreased ETTCP and the control group at any times points (P > 0.05). Ratnaraj et al9 found similar results in 24 patients after ACSS when lowering the ETTCP to 20 mm Hg did not lower the rates of dysphagia. Rihn et al19 suggested that the lack of significant difference between the treatment and control groups was largely the result of the ACSS itself rather than potential confounding factors such as increase in ETTCP. Smith-Hammond et al3 also suggested intubation alone is not a risk factor for postoperative dysphagia. In contrast, reports have suggested that elevated cuff pressures and prolonged intubation do in fact result in laryngeal nerve dysfunction and thus leads to development of hoarseness.20 Deflation of the ETT cuff after retractor placement with subsequent reinflation to just-seal pressure may be an important maneuver to prevent dysphagia.11 Jellish et al8 reported an association between prolonged retraction, increased ETTCP, and postoperative sore throat and hoarseness suggesting decreasing that the ETTCP during neck retraction decreased the risk of dysphagia. Although the proposed etiology of postoperative dysphagia remains uncertain, there is a consensus regarding the natural history of dysphagia, in particular the transient symptomatology and progressive resolution. We found that 59% of the pooled participants reported scores of dysphagia at 24 hours, 36% at 6 weeks, 24% at 3 months, and back to 18% at 6 months postoperatively. This trend is similar to the findings of a recent literature review, which highlighted that for most patients, postoperative dysphagia improves with time.5,13 Similarly, Sagi et al20 found, in a retrospective chart review of 311 anterior cervical procedures, a decrease in the rate of dysphagia from 60% in early postoperative period to approximately 12% in 6 months follow-up. Our dysphagia rates at 3 months are slightly lower than Riley et al4 who reported that 28% of 454 patients had dysphagia at their 3-month assessment. Another reported cause of postoperative dysphagia is soft tissue swelling.2,14 We reported significantly increased soft tissue thickness at the 24-hour postoperative Copyright

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timepoint in the pooled group compared with all followup visits. It is an indirect measure of the possible damage and ischemia in the early timepoints following ACSS.2,14 Sanfilippo et al21 reported similar results wherein soft tissue swelling was observed at 2 weeks postsurgery, which then normalized by 6 weeks. Similarly, Kepler et al22 found that the anterior soft tissue shadow width increased at all levels expect C1 at 2 weeks and C2 at 6 weeks following a 1- or 2-level ACDF. The groups were separated into: group 1 with no symptoms/mild dysphagia and group 2 with moderate/severe dysphagia. There were no significant differences in the soft tissue measurements between the groups.22 Furthermore, a study by Song et al23 linked higher prevertebral soft tissue swelling in patients who had undergone multilevel or high-level fusions. This is an important finding as it helps narrow down the possible mechanisms in dysphagia following ACSS and rule out reductions of ETTCP or soft tissue swelling. The current study possesses unique strengths in the study design compared with previous research. Firstly, our study is prospective and has a consistent protocol for data collection. Edwards et al24 showed postoperative dysphagia was underreported after ACSS by physicians in the medical chart. Furthermore, prospective studies uncovered a higher, and often underreported, incidence of dysphagia compared with retrospective reports suggesting postoperative dysphagia is a more common problem than previously thought.5,19 Only one previous study included control patients who were undergoing the same ACSS as the treatment group. SmithHammond et al3 compared ACSS to posterior cervical and posterior lumbar surgeries, whereas Rihn et al19 compared ACDF patients to posterior lumbar decompression. We attempted to accurately determine the effect of decreased ETTCP in ACSS by comparing the treatment group with controls undergoing the same surgery, with the exception of the reduced ETTCP. Although objective evaluation of dysphagia provides important information, patient-reported measures of dysphagia might be more clinically important. Medical records, compared with patient surveys, substantially underreport postoperative dysphagia, which aids in explaining the wide range of incidence in past research.24 We acquired not only subjective dysphagia scores but also plain radiographs to objectively measure soft tissue swelling along in the evaluation of swallowing difficulties. All procedures performed in our study were singlelevel anterior cervical arthroplasty or discectomy and fusion. There were no significant differences in dysphagia rates or soft tissue swelling in the arthroplasty or ACDF groups in the treatment or control group. In contrast, reports have shown lower rates of dysphagia in artificial disk patients compared with ACDF procedures.15,25 These conflicting results illustrate a major limitation of our current study with its small sample size. The total number of surgery patients may have been too small to observe an effect between subgroups within this population. Another limitation is the widely accepted outcome measures used to assess the incidence and severity of postoperative dysphagia.1,3 We elected to utilize DDI Copyright

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and BYDS to allow for meaningful comparisons of our results to prior studies.19 This study demonstrated that decreased ETTCP maintained at 15 mm Hg has no effect on the rates of dysphagia after single-level ACSS, whether arthroplasty or fusion. As expected, the incidence of dysphagia decreased over time and normalized by 6 months postsurgery. REFERENCES 1. Bazaz R, Lee MJ, Yoo JU. Incidence of dysphagia after anterior cervical spine surgery: a prospective study. Spine (Phila Pa 1976). 2002;27:2453–2458. 2. Frempong-Boadu A, Houten JK, Osborn B, et al. Swallowing and speech dysfunction in patients undergoing anterior cervical discectomy and fusion: a prospective, objective preoperative and postoperative assessment. J Spinal Disord Tech. 2002;15: 362–368. 3. Smith-Hammond CA, New KC, Pietrobon R, et al. Prospective analysis of incidence and risk factors of dysphagia in spine surgery patients: comparison of anterior cervical, posterior cervical, and lumbar procedures. Spine (Phila Pa 1976). 2004;29:1441–1446. 4. Riley LH III, Skolasky RL, Albert TJ, et al. Dysphagia after anterior cervical decompression and fusion: prevalence and risk factors from a longitudinal cohort study. Spine (Phila Pa 1976). 2005;30:2564–2569. 5. Riley LH III, Vaccaro AR, Dettori JR, et al. Postoperative dysphagia in anterior cervical spine surgery. Spine (Phila Pa 1976). 2010;35:S76–S85. 6. Mendoza-Lattes S, Clifford K, Bartlet R, et al. Dysphagia following anterior cervical arthrodesis is associated with continuous, strong retraction of the esophagus. J Bone Joint Surg Am. 2008;90:256–263. 7. Lee MJ, Bazaz R, Furey CG, et al. Risk factors for dysphagia after anterior cervical spine surgery: a two-year prospective cohort study. Spine J. 2007;7:141–147. 8. Jellish WS, Jensen RL, Anderson DE, et al. Intraoperative electromyographic assessment of recurrent laryngeal nerve stress and pharyngeal injury during anterior cervical spine surgery with caspar instrumentation. J Neurosurg. 1999;91:170–174. 9. Ratnaraj J, Todorov A, McHugh T, et al. Effects of decreasing endotracheal tube cuff pressures during neck retraction for anterior cervical spine surgery. J Neurosurg. 2002;97:176–179. 10. Sperry RJ, Johnson JO, Apfelbaum RI. Endotracheal tube cuff pressure increases significantly during anterior cervical fusion with the caspar instrumentation system. Anesth Analg. 1993;76: 1318–1321. 11. Apfelbaum RI, Kriskovich MD, Haller JR. On the incidence, cause, and prevention of recurrent laryngeal nerve palsies during anterior cervical spine surgery. Spine (Phila Pa 1976). 2000;25:2906–2912. 12. McHorney CA, Ware JE Jr, Raczek AE. The MOS 36-item shortform health survey (SF-36): II. psychometric and clinical tests of validity in measuring physical and mental health constructs. Med Care. 1993;31:247–263. 13. Kalb S, Reis MT, Cowperthwaite MC, et al. Dysphagia after anterior cervical spine surgery: incidence and risk factors. World Neurosurg. 2012;77:183–187. 14. Daniels AH, Riew KD, Yoo JU, et al. Adverse events associated with anterior cervical spine surgery. J Am Acad Orthop Surg. 2008;16:729–738. 15. McAfee PC, Cappuccino A, Cunningham BW, et al. Lower incidence of dysphagia with cervical arthroplasty compared with ACDF in a prospective randomized clinical trial. J Spinal Disord Tech. 2010;23:1–8. 16. Klainer AS, Turndorf H, Wu WH, et al. Surface alterations due to endotracheal intubation. Am J Med. 1975;58:674–683. 17. Berlauk JF. Prolonged endotracheal intubation vs. tracheostomy. Crit Care Med. 1986;14:742–745. 18. Braz JR, Volney A, Navarro LH, et al. Does sealing endotracheal tube cuff pressure diminish the frequency of postoperative

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22. Kepler CK, Rihn JA, Bennet JD, et al. Dysphagia and soft-tissue swelling after anterior cervical surgery: a radiographic analysis. Spine J. 2012;12:639–644. 23. Song KJ, Choi BW, Kim HY, et al. Efficacy of postoperative radiograph for evaluating the prevertebral soft tissue swelling after anterior cervical discectomy and fusion. Clin Orthop Surg. 2012;4:77–82. 24. Edwards CC II, Karpitskaya Y, Cha C, et al. Accurate identification of adverse outcomes after cervical spine surgery. J Bone Joint Surg Am. 2004;86:251–256. 25. Segebarth B, Datta JC, Darden B, et al. Incidence of dysphagia comparing cervical arthroplasty and ACDF. SAS J. 2010;4:3–8.

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Commentary: Dysphagia after anterior cervical spine surgery.

Oropharyngeal Dysphagia after anterior cervical spine surgery: a review.

[Dysphonia and dysphagia after anterior cervical spine surgery].

Dysphagia secondary to anterior cervical spine osteophytes.

[Endotracheal tube cuff pressure and manometry].

Risk factors for dysphagia after anterior cervical spine surgery: A meta-analysis.

Effect of perioperative steroids on dysphagia after anterior cervical spine surgery: A systematic review.

The association between psychiatric factors and the development of chronic dysphagia after anterior cervical spine surgery.

Dysphagia after anterior cervical spine surgery: a systematic review of potential preventative measures.

Dysphagia Secondary to Anterior Osteophytes of the Cervical Spine.

Endotracheal Tube Cuff Pressure Monitoring in Peripheral Hospitals.

Negative pressure pulmonary edema associated with anterior cervical spine surgery.

Delayed Esophagus Perforation after Anterior Cervical Spine Surgery.

Gelfoam-induced Swallowing Difficulty after Anterior Cervical Spine Surgery.

Handcrafted cuff manometers do not accurately measure endotracheal tube cuff pressure.

Endotracheal tube cuff failure due to valve damage.

Thyroid storm following anterior cervical spine surgery for Koch's spine.

Giant anterior cervical osteophyte leading to Dysphagia.

Reply to: Adjusting tracheal tube cuff pressure.

Tracheal palpation to assess endotracheal tube depth: an exploratory study.

Tracheal ultrasound to assess endotracheal tube depth: an exploratory study.

The effect of endotracheal tube cuff pressure change during gynecological laparoscopic surgery on postoperative sore throat: a control study.

Comparison of the endotracheal tube cuff pressure between a tapered- versus a cylindrical-shaped cuff after changing from the supine to the lateral flank position.

Endotracheal Tube Cuff Pressure Assessment: Education May Improve but not Guarantee the Safety of Palpation Technique.