Effect of chin tuck against resistance exercise on patients with dysphagia following stroke: A randomized pilot study

Abstract

BACKGROUND:

Recently, chin tuck against resistance exercise (CTAR) has been reported as a remedial treatment for pharyngeal dysphagia. However, the clinical evidence of the effect is still lacking.

OBJECTIVE:

This study investigated the effect of CTAR on the swallowing function in patients with dysphagia following subacute stroke.

METHODS:

The patients were randomly assigned to an experimental (n = 11) or a control group (n = 11). The experimental group performed CTAR using the CTAR device. The control group received only conventional dysphagia treatment. Both groups received training on five days a week, for four weeks. The swallowing function was measured using functional dysphagia scale (FDS) and penetration-aspiration scale (PAS), based on a videofluoroscopic swallowing study (VFSS).

RESULTS:

The experimental group showed more improvements in the oral cavity, laryngeal elevation/epiglottic closure, residue in valleculae, and residue in pyriform sinuses of FDS and PAS compared to the control group (p < 0.05, all).

CONCLUSIONS:

This study demonstrated that CTAR is effective in improving the pharyngeal swallowing function in patients with dysphagia after stroke. Therefore, we recommend CTAR as a new remedial training alternative to HLE.

Keywords

Aspiration chin tuck against resistance dysphagia stroke rehabilitation

1 Introduction

Rehabilitative treatment is important to improve function in the oropharyngeal phase of swallowing in patients with dysphagia, as this phase is directly related to aspiration, which can cause pneumonia and even death (Bahia, Mourao, & Chun, 2016; Lim, Lee, Yoo, & Kwon, 2014). The pharyngeal phase begins with the swallowing reflex and contraction of the suprahyoid muscles (SHM) in the anterior region of the neck (Kim, Choi, Yoo, Chang, Lee, & Park, 2017). The SHM connect the jaw to the hyoid bone, and comprise of the mylohyoid, geniohyoid, and digastric muscles (Pearson, Langmore, Yu, & Zumwalt, 2012). The contractions of these muscles contribute to the normal swallowing mechanism by pulling the hyoid bone antero-superiorly, then closing the epiglottis and relaxing the upper esophageal sphincter (Kendall & Leonard, 2011; Matsuo & Palmer, 2008). In other words, SHM play an important role in safe swallowing in the pharyngeal phase.

However, neurological diseases such as stroke can weaken the SHM, which may result in decreased hyoid bone movement, vallecular/pyriform sinus residue, and aspiration or penetration (Cook et al., 1989). Therefore, an intervention to strengthen the SHM in the pharyngeal phase is important as a remedial method.

Various therapeutic methods for enhancing SHM activity in the pharyngeal phase have been reported. These include electrical stimulation, effortful swallowing, tongue resistance exercise, and expiratory muscle strength training. The head lift exercise (HLE) is commonly used in clinical practice because it can enhance SHM activity and is noninvasive, inexpensive, and safe. The HLE involves lifting the head against the pull of gravity and head weight, from a supine position. This exercise has been known to be effective in improving the pharyngeal phase with less risk of aspiration, better clearance of the pharyngeal residue, and improved relaxation of the upper esophageal sphincter, by promoting activation of the SHM in those vulnerable to swallowing disorders, such as elderly individuals and patients with a variety of diseases (Park, Hwang, Oh, & Chang, 2017; Shaker et al., 1997). However, according to previous studies, HLE has several limitations. First, it has to be performed in a supine position. Therefore, the elderly or patients with neurological disorders, who need space and cannot easily adjust posture, may find it difficult to perform. Second, HLE has a high dropout rate, as it requires excessive effort. Third, HLE has an aspect of inefficiency due to excessive efforts on the SCM and abdominal muscles (Easterling, Grande, Kern, Sears, & Shaker, 2005). These problems can affect treatment compliance and effectiveness. Therefore, an alternative approach is needed.

Recently, several studies have reported a modified method to compensate for the limitations of the existing HLEs (Hughes & Watts, 2016; Watts, 2013; Yoon, Khoo, & Rickard Liow, 2014). A method of training the SHM by placing an elastic rubber ball with resistance on the chin and sternum, and then tucking the chin against the resistance has been proposed (Yoon, Khoo, & Rickard Liow, 2014). The results of performing CTAR in normal adults demonstrate increased activation of the SHM; the activation was comparable with that achieved by the HLE. On the other hand, subjects reported subjective feedback that CTAR was less strict than HLE. In other words, CTAR has been shown to induce a more or similar degree of activation of SHM in a more comfortable way than HLE. Gao and colleagues also compared CTAR using an inflatable rubber ball with HLE in patients with dysphagia after stroke (Gao & Zhang, 2016). CTAR had a positive effect on psychological status and depression and reduced aspiration/penetration in stroke patients with dysphagia. Previous studies, however, had some limitations. First, most studies measured only the immediate activation of SHM in normal adults. Second, the studies did not evaluate the detailed function of the oropharyngeal phase in patients with dysphagia after stroke. Therefore, the effect of CTAR on dysphagic patients is still unclear and lacks evidence. This study investigates the effect of CTAR on the swallowing function in patients with dysphagia after stroke, based on previous studies.

2 Methods

2.1 Study design

This study was designed as a single blind, randomized trial.

2.2 Participants

Patients with dysphagia undergoing rehabilitation were recruited for this study as subjects (n = 25), according to the following inclusion criteria: 1) dysphagia following stroke was confirmed by a videofluoroscopic swallowing study (VFSS), 2) the onset duration was <12 months, 3) the patients were able to swallow voluntarily, 4) the Mini-Mental State Examination score was ≥20, 5) ability to sit without assistance, and 6) ability to perform chin tuck using the CTAR device. The exclusion criteria were as follows: 1) secondary stroke; 2) severe communication disorders, such as severe aphasia, dementia, etc.; 3) pain in the neck region; 4) unstable medical conditions; and 5) head and neck cancer. We explained the objective and requirements of our study to all participants, and they voluntarily signed informed consent forms. Ethical approval was obtained from the Inje University Institutional Review Board before conducting the experiment.

2.3 Procedures

The participants were randomly allocated to an experimental group (n = 13) or a control group (n = 12) by blocked randomization to ensure an equal number in both groups. The experimental group performed CTAR using a CTAR device (ISO-CTAR Device, Alternative Speech and Swallowing Solutions) in a sitting position on a chair.

The CTAR method was applied similar to the existing HLE method and isometric and isotonic exercises were performed separately (Park et al., 2017). In isometric CTAR, the patients are asked to chin tuck against device 3 times for 60 s with no repetition. In isotonic CTAR, the patient performs 30 consecutive repetitions by strongly pressing against the resistance of the device and releasing it again (Fig. 1).

Fig.1

Chin tuck against resistance training.

To perform the CTAR correctly, the therapist explained and demonstrated the exercise methods to all patients before the intervention. We especially emphasized on the correct chin tuck posture, so that the patients do not flex their heads against the devices. We also instructed them to press as strongly as possible for greater activation of the SHM.

Both groups received the same conventional dysphagia treatment (CDT) such as orofacial muscle exercises, thermal tactile stimulation, and therapeutic or compensatory maneuvers. An experienced occupational therapist performed the CDT in allparticipants for 30 min/day, five days a week, for 4 weeks. All interventions were performed by an occupational therapist with 7 years of clinical experience in treating dysphagia. A flowchart of this study is shown in Fig. 2.

Fig.2

Flowchart of this study.

2.4 Outcome measures

The oropharyngeal swallowing function was measured by the functional dysphagia scale (FDS) and the penetration-aspiration scale (PAS) based on a videofluoroscopic swallowing study. VFSS was performed by experienced radiologists and rehabilitation physicians.

The FDS is a functional evaluation scale that comprehensively reflects the overall oropharyngeal swallowing function in stroke patients based on the VFSS findings (Han, Paik, & Park, 2001). The FDS consists of 11 items with weighted values representing 4 oral (lip closure, bolus formation, residue in oral cavity, oral transit time) and 7 pharyngeal (triggering of pharyngeal swallow, laryngeal elevation and epiglottic closure, nasal penetration, residue in valleculae, residue in pyriform sinuses, coating of pharyngeal wall after swallow, pharyngeal transit time) functions that can be observed by VFSS.

The PAS is a standard tool that reflects laryngeal penetration and aspiration. The scale is broken down into eight different levels based on the depth of material penetration into the airway and whether the material entering the airway is expelled; higher levels indicate higher aspiration severity (Rosenbek, Robbins, Roecker, Coyle, & Wood, 1996). FDS and PAS scores were interpreted by one rehabilitation physician.

2.5 Data analysis

Participants’ characteristics were analysed using IBM SPSS Statistics version 20 (IBM Corp., Armonk, NY, USA). Descriptive statistics are presented as means with standard deviations. The Wilcoxon signed-rank test was used to compare the differences in outcome measurement before and after intervention. The Mann–Whitney U-test was used to compare pre- and post-intervention data between groups. The significance level was set at p < 0.05. In addition, the effect sizes (Cohen d) calculated by dividing the standardized mean difference between the two groups by using the pooled standard deviation. Effect size of 0.2, 0.5 and 0.8 represent a small, moderate or large effect respectively.

3 Results

3.1 Participants

In total, 22 participants completed this study. Three participants dropped out prior to the follow-up because of discharge. A summary of the clinical and demographic features of the subjects (n = 22) is shown in Table 1. The table also shows that no significant differences in the baseline characteristics were observed between the two groups (p > 0.05).

Table 1
Characteristics of participants

Characteristics Experimental group (n = 11) Control group (n = 11)

Age (year), mean±SD (range) 62.16±17.27 (43–81) 58.43±12.51 (46–79)

Gender(n)

Men 6 4

Women 5 7

Type of stroke (n)

Hemorrhage 4 5

Infarction 7 6

Site of stroke lesion (n)

Middle cerebral artery 7 9

Internal capsule 2 1

Basal ganglia 2 1

Paretic side (n)

Right 6 4

Left 5 7

Time after stroke (weeks) 37.24±8.54 (27–56) 32.14±14.38 (21–63)

Feeding type (n)

Oral feeding 4 5

Tube feeding 7 6

Other deficit (n)

Dysarthria 1 0

Facial palsy 2 2

Characteristics	Experimental group (n = 11)	Control group (n = 11)
Age (year), mean±SD (range)	62.16±17.27 (43–81)	58.43±12.51 (46–79)
Gender(n)
Men	6	4
Women	5	7
Type of stroke (n)
Hemorrhage	4	5
Infarction	7	6
Site of stroke lesion (n)
Middle cerebral artery	7	9
Internal capsule	2	1
Basal ganglia	2	1
Paretic side (n)
Right	6	4
Left	5	7
Time after stroke (weeks)	37.24±8.54 (27–56)	32.14±14.38 (21–63)
Feeding type (n)
Oral feeding	4	5
Tube feeding	7	6
Other deficit (n)
Dysarthria	1	0
Facial palsy	2	2

SD: standard deviation.

3.2 FDS assessment

The experimental group showed more improvement in the residue in oral cavity, laryngeal elevation/epiglottic closure, residue in valleculae, and residue in pyriform sinuses of FDS assessment, when compared with the control group (p = 0.044, 0.039, 0.037, 0.047, respectively) (Table 2). In a comparison of the amount of change in the groups, both groups showed significant differences in oral cavity, laryngeal elevation/epiglottic closure, residue in valleculae, and residue in pyriform sinuses of FDS (p = 0.011, 0.024, 0.015, 0.005, respectively) (Table 3).

Table 2
Changes in parameters before and after the treatment

Experimental group Control group Between groups P-value Effect size

Before treatment After treatment P-value Before treatment After treatment P-value

FDS

LC 2.73±2.61 1.82±2.52 0.157 2.27±2.61 2.27±2.61 1 0.672 0.35

BF 2.09±1.76 1.27±1.85 0.083 1.82±1.83 1.36±1.57 0.45 0.82 0.21

ROC 2.18±1.66 0.45±0.82 0.010^* 1.82±1.66 1.64±1.5 0.564 0.044^† 1.44

OTT 3.27±3.13 2.18±2.71 0.102 2.73±2.83 1.82±2.27 0.109 0.772 0.07

TPS 3.18±4.05 1.82±2.52 0.083 2.73±4.67 1.82±3.37 0.157 0.778 0.15

LEEC 8.55±5.52 3.1±2.73 0.011^* 7.09±5.09 5.5±3.24 0.045^* 0.039^† 1.21

NP 3.27±3 2.55±3.24 0.157 2.73±2.57 2.18±1.89 0.257 0.943 0.05

RV 5.45±2.02 2.18±1.89 0.01^* 4.73±1.62 4±1.55 0.102 0.037^† 1.48

RPS 4.73±2.41 1.64±1.96 0.007^* 4±2.53 3.64±2.34 0.414 0.047^† 1.3

CPW 2.28±4.1 1.36±3.23 0.157 1.36±3.23 0.91±2.02 0.317 0.922 0.17

PTT 1.82±2.09 1.09±1.87 0.157 1.64±1.96 1.45±2.02 0.317 0.655 0.28

Total 38.64±18.41 22.36±11.57 0.003^* 33.18±16.23 27.18±14.21 0.028^* 0.45 0.79

PAS 5.73±1.19 3.55±1.29 0.012^* 5.18±1.6 4.73±1.27 0.347 0.043^† 1.3

	Experimental group	Control group	Between groups P-value	Effect size
FDS
LC	2.73±2.61	1.82±2.52	0.157	2.27±2.61	2.27±2.61	1	0.672	0.35
BF	2.09±1.76	1.27±1.85	0.083	1.82±1.83	1.36±1.57	0.45	0.82	0.21
ROC	2.18±1.66	0.45±0.82	0.010^*	1.82±1.66	1.64±1.5	0.564	0.044^†	1.44
OTT	3.27±3.13	2.18±2.71	0.102	2.73±2.83	1.82±2.27	0.109	0.772	0.07
TPS	3.18±4.05	1.82±2.52	0.083	2.73±4.67	1.82±3.37	0.157	0.778	0.15
LEEC	8.55±5.52	3.1±2.73	0.011^*	7.09±5.09	5.5±3.24	0.045^*	0.039^†	1.21
NP	3.27±3	2.55±3.24	0.157	2.73±2.57	2.18±1.89	0.257	0.943	0.05
RV	5.45±2.02	2.18±1.89	0.01^*	4.73±1.62	4±1.55	0.102	0.037^†	1.48
RPS	4.73±2.41	1.64±1.96	0.007^*	4±2.53	3.64±2.34	0.414	0.047^†	1.3
CPW	2.28±4.1	1.36±3.23	0.157	1.36±3.23	0.91±2.02	0.317	0.922	0.17
PTT	1.82±2.09	1.09±1.87	0.157	1.64±1.96	1.45±2.02	0.317	0.655	0.28
Total	38.64±18.41	22.36±11.57	0.003^*	33.18±16.23	27.18±14.21	0.028^*	0.45	0.79
PAS	5.73±1.19	3.55±1.29	0.012^*	5.18±1.6	4.73±1.27	0.347	0.043^†	1.3

SD: standard deviation. ^*p < 0.05 by Wilcoxon test, ^†p < 0.05 by Mann-Whitney U test. FDS: Functional dysphagia scale, LC: Lip closure, BF: Bolus formation, ROC: Residue in oral cavity, OTT: Oral transit time, TPS: Triggering of pharyngeal swallow, LEEC: Laryngeal elevation and epiglottic closure, NP: Nasal penetration, RV: Residue in valleculae, RPS: Residue in pyriform sinuses, CPW: Coating of pharyngeal wall after swallow, PTT: Pharyngeal transit time, PAS: Penetration-aspiration scale.

3.3 PAS assessment

The experimental group showed more improvement in the PAS, when compared to the control group (p = 0.043) (Table 2). In a comparison of the amount of change in the groups, both groups showed significant differences in PAS assessment (p = 0.032) (Table 3).

Table 3
Comparison of FDS, PAS in both of groups after intervention

Experimental group (Mean±SD) Control group (Mean±SD) Between group p-value

FDS

LC 0.91±2.02 0±2.23 0.328

BF 0.82±1.4 0.45±1.69 0.66

ROC 1.9.±1.42 0.18±1.08 0.011^†

OTT 1.09±2.02 0.91±1.92 0.933

TPS 1.36±2.34 0.9±2.02 0.619

LEEC 5.72±4.31 2.09±2.91 0.024^†

NP 0.73±1.62 0.55±1.57 0.933

RV 3.27±2.57 0.73±1.35 0.015^†

RPS 3.09±2.07 0.36±1.5 0.005^†

CPW 0.91±2.02 0.45±1.51 0.544

PTT 0.73±1.62 0.18±0.6 0.474

Total 16.27±9.79 6±7.14 0.016^†

PAS 2.18±1.83 0.45±1.63 0.032^†

	Experimental group (Mean±SD)	Control group (Mean±SD)	Between group p-value
FDS
LC	0.91±2.02	0±2.23	0.328
BF	0.82±1.4	0.45±1.69	0.66
ROC	1.9.±1.42	0.18±1.08	0.011^†
OTT	1.09±2.02	0.91±1.92	0.933
TPS	1.36±2.34	0.9±2.02	0.619
LEEC	5.72±4.31	2.09±2.91	0.024^†
NP	0.73±1.62	0.55±1.57	0.933
RV	3.27±2.57	0.73±1.35	0.015^†
RPS	3.09±2.07	0.36±1.5	0.005^†
CPW	0.91±2.02	0.45±1.51	0.544
PTT	0.73±1.62	0.18±0.6	0.474
Total	16.27±9.79	6±7.14	0.016^†
PAS	2.18±1.83	0.45±1.63	0.032^†

SD: standard deviation. ^†p < 0.05 by Mann-Whitney U test. FDS: Functional dysphagia scale, LC: Lip closure, BF: Bolus formation, ROC: Residue in oral cavity, OTT: Oral transit time, TPS: Triggering of pharyngeal swallow, LEEC: Laryngeal elevation and epiglottic closure, NP: Nasal penetration, RV: Residue in valleculae, RPS: Residue in pyriform sinuses, CPW: Coating of pharyngeal wall after swallow, PTT: Pharyngeal transit time, PAS: Penetration-aspiration scale.

4 Discussion

This study investigated the effect of CTAR on the swallowing function in patients with dysphagia after stroke. Both groups (experiment and control) showed significant improvements in the swallowing function; however, on comparing the two groups after the intervention, it was found that the CTAR-treated group showed more improvement in swallowing, compared to the CDT-only control group. Therefore, this study demonstrated the efficacy of CTAR. The results of this study can be explained with several reasons.

First, the basic principle of CTAR is resistance exercise. We used the CTAR device to apply the resistance. Resistance exercises provide more loading on the target muscle than other types of exercise, which activate the muscle. Several previous studies have demonstrated that CTAR causes similar or greater activation of the SHM than HLE (Hughes & Watts, 2016; Watts, 2013; Yoon, Khoo, & Rickard Liow, 2014). Greater muscle activation means that a large number of motor units are recruited, resulting in greater muscle contraction (Park, Oh, Chang, & Kim, 2016). CTAR induces greater muscle activation, which can be expected to result in muscular hypertrophy and greater muscle strength, when performed repeatedly. Therefore, CTAR in this study may have affected the SHM strength in stroke patients.

Second, activation of the SHM and improvement in muscle strength through resistance training contribute to normal swallowing. The mechanism of normal swallowing is shifted from the oral cavity to the pharynx through chewing, conditioning, and formation of bolus. At this time, contraction of the SHM occurs with swallowing reflex (Park, Oh, Hwang, & Lee, 2016). The contraction of the SHM pulls the hyoid and larynx upwards, causing rotation of the epiglottis and helping in airway closure (Ertekin & Aydogdu, 2003; Lang, 2009). Therefore, we believed that resistance training through CTAR helps improve pharyngeal dysphagia, and the results of this study are similar to those of previous HLE.

The effect of resistance training of the skeletal muscles depends on the training period. Previous studies have reported that resistance training in patients with stroke requires a minimum of 4 weeks to induce physiological changes in the muscles (Moritani & deVries, 1979). Park and colleagues also demonstrated improvements in the swallowing function by HLE performed for 4 weeks as a part of strength training in patients with dysphagia (Park et al., 2017). Robbins and colleagues demonstrated an increase in the tongue volume and muscle strength in patients with dysphagia after stroke for 4 weeks (Robbins et al., 2007). Therefore, this study also suggests that the 4-week CTAR training may have affected the increase in the strength of the SHM.

This study attempted to maximize the effect of CTAR as follows. The SHM group is a small group of muscles located between the mandibular and hyoid bones. Therefore, neck flexion should be avoided in order to stimulate them selectively; neck flexion against resistance makes it difficult to contract the SHM. Thus, the therapist continuously monitored the patients while they were performing CTAR, and incorrect postures were not counted in the number of training sessions. Previous studies have also reported that caution is needed when performing isotonic training with CTAR (Yoon, Khoo, & Rickard Liow, 2014). Isotonic training is a method of repeating chin tuck against resistance. It is divided into concentric and eccentric exercise, and both are important factors for muscular strengthening through the resistance exercise. Concentric exercise involves a chin tuck posture against resistance, and the loading is sufficient for the SHM. In contrast, returning to the original position from the chin tuck posture, i.e., eccentric contraction of the SHM involves little or no loading of the SHM. This happens as the elastic nature of the rubber ball or CTAR device enables it to return to its original shape. Therefore, this study indicated that when performing eccentric contraction of isotonic training, it should be turned back to its original posture against resistance with slow, controlled movements.

This study, however, has some limitations. First, it is difficult to generalize the results of this study because the sample size was very small, as it was a pilot study. Second, the CTAR device used in this study cannot adjust the intensity of resistance, making it difficult to conduct systematic resistance training. Third, the long-term effect is unknown because only the pre- and post-intervention evaluations were performed. Finally, this study did not compare CTAR and HLE; thus, we could not judge which treatment is more effective.

5 Conclusion

This study demonstrated that CTAR is effective in improving the swallowing function in patients with dysphagia after stroke. Therefore, CTAR can be recommended as an alternative to HLE.

Conflict of interest

None to report.

Funding

This work was supported by the 2016 Inje University research grant.

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