Evaluating Swallowing Dysfunction Using a 100-ml Water Swallowing Test

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1 Dysphagia 19:43 47 (2004) DOI: /s x Evaluating Swallowing Dysfunction Using a 100-ml Water Swallowing Test Meng-Chun Wu, MD, 1 Yeun-Chung Chang, MD, 2 Tyng-Guey Wang, MD, 1 and Li-Chan Lin 3 1 Department of PhysicalMedicine and Rehabilitation, and 2 Department of MedicalImaging, NationalTaiwan University Hospital, National 1 Taiwan University College of Medicine; and 3 Institute of Clinical Nursing, NationalYang-Ming University, Taipei, Taiwan Abstract. This study used comparison with videofluoroscopic examination of swallowing (VFES) to examine the validity of a 100-ml water swallowing test (WST) in assessing swallowing dysfunction. Fifty-nine consecutive outpatients (15 females, 44 males) with clinically suspected dysphagia were enrolled in this study. Each subject underwent a 100-mlWST followed by VFES. Data was obtained on swallowing speed and signs of choking (coughing and a wethoarse voice). The analytical results revealed that 49 subjects had abnormal swallowing speeds (<10 ml/s) in the 100-mlWST, and 47 of them were identified as having dysphagia by VFES. Among the ten participants with normal swallowing speed (>10 ml/s), eight were diagnosed with dysphagia by VFES. Notably, 14 participants choked in the 100-mlWST, 11 of whom exhibited aspiration or penetration in VFES. Among the 45 participants without choking in WST, 12 displayed aspiration or penetration in VFES. The sensitivity of swallowing speed in detecting the swallowing dysfunction was 85.5%, and the specificity was 50%. Moreover, the sensitivity of using choking or wet-horse voice in the 100-mlWST as the sole factor for predicting the presence of aspiration was 47.8%, while the specificity was 91.7%. Therefore, this study concluded that swallowing speed is a sensitive indicator for identifying patients at risk for swallowing dysfunction. Moreover, choking in the 100-ml WST may be a potentialspecific indicator for followup aspiration. Correspondence to: Tyng-Guey Wang, M.D., Department of PhysicalMedicine & Rehabilitation, NationalTaiwan University Hospital, 7 Chung-Shan South Road, Taipei 100, Taiwan, ROC. Telephone: , ext. 7588; tgw@ha.mc.ntu. edu.tw. Key words: Water test Videofluoroscopy Dysphagia Aspiration Deglutition Deglutition disorders. Dysphagia, a symptom of swallowing dysfunction, can be evoked by numerous disorders, including both neurological and non-neurological ones. Dysphagia not only deprives people of the pleasure from eating but also endangers patient health by creating a risk of aspiration pneumonia and malnutrition [1]. Accurately assessing swallowing dysfunction, especially aspiration risk, thus is extremely important to clinicians in providing crucial information to prevent morbidity and mortality from swallowing disorders. Videofluoroscopic examination of swallowing (VFES) has been widely recommended as a gold standard in identifying swallowing dysfunction [2]. However, VFES has radiation exposure and is relatively costly and time consuming; thus, its use is not practicalfor every patient suspected of having dysphagia. Consequently, designing effective screening methods to identify patients for VFES referralis the most clinically feasible approach. Severalmethods have been developed for identifying subjects suitable for VFES referral. One method with significant potentialis observing water swallowing. Ninety- to 150-ml water swallowing test (WST) have been used to evaluate swallowing disorders but the efficiency and accuracy of these methods remains uncertain. For example, DePippo et al. [2] reported that choking on a 3-oz. WST was a sensitive indicator for identifying patients requiring referralfor VFES. Moreover, Horner and Massey [3] reported that aspirating subjects differed

2 44 M.-C. Wu et al.: Water Test in Swallow from nonaspirating subjects in having a low prevalence of subjective complaints of swallowing difficulties and a higher prevalence of weak cough reflex and dysphonia. Linden and Siebens [4] noted that wet-hoarse voice quality and impaired pharyngeal gag reflex were correlated with the presence of aspiration on VFES examination in nine of a total sample of 11 patients. Scales et al. [5] identified seven clinical signs displayed by aspirating patients and applied these clinical parameters to identify up to 42% of subjects with aspiration on VFES examination. However, bedside swallowing tests have long been criticized for lack of objectiveness in identifying aspirating patients. Nathadwarawala et al. [6] first used objective swallowing speed to assess swallowing function and found that swallowing speed was significantly reduced in subjects with swallowing problems. They further proposed that reduced swallowing speed in chronic neurological diseases is one of the compensatory or adaptive mechanisms used by many patients before an overt clinical problem develops. However, none of the above investigations used VFES to present further evidence of swallowing dysfunction. To address these issues, this study designed a 100-mlWST. The primary purpose of this study was to determine the role of a 100-ml WST in evaluating swallowing dysfunction. By observing both swallowing speed and signs of choking, as well as correlating these parameters with findings on VFES, this work attempted to estimate the sensitivity and specificity of a 100-ml WST in detecting swallowing dysfunction. Methods Participants Fifty-nine individuals, consecutively referred to videofluoroscopic examination for clinical suspected swallowing disorders, were recruited in this study. All participants preserved the ability to eat orally at the time of referral and were fully cooperative. The mean age of the sample group was 71.7 ± 11.4 years (range years); the group consisted of 44 males and 15 females. Stroke was the main reason for dysphagia in the subjects; 51 subjects had a previous history of stroke, while the remaining 8 individuals had no definite neurological disorders. Nineteen subjects had right-hemisphere strokes, 18 patients had left-hemisphere strokes, 10 patients had bilateral hemisphere strokes, and 4 had brain stem and other strokes. All stroke patients had suffered their attacks at least six months previously and had stable neurological status on referral. The study procedures were fully explained, and consent forms were obtained from all participants. 100-ml Water Swallowing Test Twenty-four hours before VFES, a 100-mlWST was performed for each participant as follows. First, the participants were seated upright and asked to place a glass of 100 ml of distilled water to their lips. On receiving a go signal, they drank the water in the glass as quickly as possible. Hand dexterity of the subjects was confirmed to be acceptable by neurological examination. A stopwatch with a readability of 1 ms was used to measure the swallowing time, measured from the go signal to the end of WST. Notably, for those who successfully finished the glass of the water, the end of WST was defined as the completion of the last swallow, indicated visually by the return of the thyroid cartilage to its resting position. Signs of choking, defined as coughing from the beginning of WST to 1 min after the end WST, or a wet-hoarse voice after testing, were recorded. Participants who choked during swallowing were asked to stop drinking immediately regardless of whether they had finished the water. In such cases, the stopwatch was stopped as soon as choking occurred. The amount of water drunk was determined by subtracting the residualwater from 100 ml, using a minimum scale of 1 ml. Swallowing speed (ml/s), defined as the amount of drunken water divided by elapsed time on the stopwatch, was also calculated. Notably, an abnormal swallowing speed was defined as swallowing speed below 10 ml/s in accordance with the definition used in the literature [7]. Videofluoroscopic Examination of Swallowing Standardized VFES was conducted at our institution using a fluoroscope with a remote control(kox-850, Toshiba Corp., Tokyo, Japan; RSZ-2000, Shimadzu Corp., Kyoto, Japan) and a high-resolution Super-VHS recorder (BR 1200, JVC, Japan). The videotape recorder offered a frame rate of 33 frames per second and could display real-time dynamic images and frame-by-frame static images. Participants were instructed to sit on a specially designed chair (VESS chair, Vess Chairs Inc., Milwaukee, WI, USA) for both lateral and frontal anterior posterior views. Each participant swallowed three standardized formulas (5 ml each of thin, thick, and paste medium) of barium sulfate (E-Z-HD, E-Z-EM, Inc., Westbury, NY, USA) sequentially [8,9]. Notably, thin barium sulfate (suspension of 340 g E-Z-HD and 65 ml of water) is a standard for routine gastrointestinalexaminations. Thick barium was prepared by adding an extra 7.5 mlof E-Z-HD powder in a 15- mlstandard thin barium preparation, while paste barium was prepared with adding extra 12 mlof E-Z-HD powder in a 15-ml standard thin barium preparation. By viewing the VEFS videotapes, an experienced radiologist timed the oral transit time, pharyngealtransit time, and trigger time for each formula. Oraltransit time was defined as the time elapsed from placing the formula at the anterior dorsal tongue to the formula completely leaving the valleculae. Pharyngeal transit time was determined by the time from the formula leaving the valleculae to completely leaving the pharynx. Swallowing trigger time was defined as the interval between the formula head arriving at the valleculae and the contraction of the upper pharyngealconstrictor muscle. The presence of oral stasis, pharyngeal stasis, pyriform stasis, vallecular stasis, and penetration as well as aspiration was also recorded. Swallowing dysfunction was defined as the presence of at least one of the following five determinants in VFES: (1) oral transit time exceeding 2 s, (2) pharyngealtransit time exceeding 1 s, (3) trigger time exceeding 1 s, (4) laryngeal penetration, (5) aspiration, and (6) stasis at more than two sites of valleculae and pyriform sinuses.

3 M.-C. Wu et al.: Water Test in Swallow 45 Table 1. Videofluoroscopic characteristics of patients Findings on VFES Normal2 Oraltransit time more than 2 s 15 Pharyngealtransit time more than 1 s 21 Trigger time more than 1 s 17 Occurrence of laryngeal penetration 12 Aspiration 11 Stasis more than 2 sites stated above 25 Number of patients Table 2. Relationship between water swallowing speed and VFES VFES Swallowing speed Abnormal Normal Abnormal(<10 ml/s) 47 2 Normal( 10 ml/s) 8 2 Table 3. Relationship between choking on 100-ml WST and aspiration or penetration on VFES Aspiration or penetration on VFES Choking on 100-mlWST Yes No Yes 11 3 No Table 4. Relationship between choking on 100-ml WST and aspiration on VFES Aspiration on VFES Choking on 100-mlWST Yes No Yes 4 10 No 7 33 Aspiration was defined as the penetration of food or liquid below the vocalfolds. Laryngealpenetration was defined as the entry of food or liquid into the laryngeal vestibule and above the vocal folds. Stasis was defined as the barium accumulation. Statistics The data were analyzed by comparing the results of the 100-ml WST with those of the VFES using the chi-squared statistic method. The sensitivity and specificity of the 100-mlWST as an indicator of choking or penetration on VFES were then determined. Results Of the 59 subjects, VFES identified 55 as having swallowing dysfunction by VFES. Specifically, 23 subjects were denoted as having aspiration or penetration in VFES, while only two of them had concomitant coughing response. Table 1 summarizes the VFES results. Table 2 presents the relationship between abnormal swallowing speed and swallowing dysfunction. Forty-nine subjects had abnormal swallowing speeds in the 100-mlWST. Among these, 47 subjects simultaneously exhibited swallowing dysfunction in VFES. In addition, 8 of the remaining 10 subjects with normal swallowing speed were identified as having swallowing dysfunction by VFES. Accordingly, the sensitivity and specificity of detecting swallowing dysfunction by employing swallowing speed in the 100-mlWST was 85.5% and 50%, respectively. Table 3 lists the correlation among choking and both aspiration and penetration on VFES. Choking was noted in 14 participants during the 100- mlwst. Notably, 11 of these subjects had concomitant penetration or aspiration in VFES. In contrast, among the 45 subjects who did not choke during the 100-mlWST, only 12 had coinstantaneous aspiration or penetration in VFES. The VFES findings for these 12 participants included 5 cases of silent aspiration, 5 cases of penetration alone, and 2 cases of obvious coughing during aspiration. Consequently, the sensitivity and specificity of using the presence of choking during the 100-mlWST to predict penetration or aspiration in VFES was 47.8% and 91.7%, respectively. Since aspiration in VFES is more clinically serious than penetration, this study further correlated aspiration with choking during the 100-mlWST. As listed in Table 4, among the 14 participants who choked during the 100-mlWST, 4 were found to aspirate on VFES. In comparison, 7 of the 45 participants who did not choke during the 100-mlWST aspirated during VFES. Moreover, 5 of the 7 participants displayed silent aspiration and 2 exhibited coughing during aspiration. Consequently, the sensitivity and specificity of using choking during the 100-mlWST to detect aspiration in VFES was 36.4% and 20.8%, respectively. Discussion The study successfully assessed the significance of detecting swallowing dysfunction using the 100-ml

4 46 M.-C. Wu et al.: Water Test in Swallow WST. Correlated with abnormal findings presented in VFES, swallowing speed and signs of choking in WST had sensitivity and specificity of up to 85.5% and 91.7%, respectively. Thus this study concludes that for dysphagic individuals capable of eating orally, estimating swallowing speed for 100 ml of water provides an effective toolfor screening for VFES referral, while measuring choking in the 100- mlwst can be used to monitor the progress of swallowing dysfunction. Although VFES has been widely accepted as an accurate method of assessing swallowing dysfunction, it is not practicalto utilize it for allsubjects suspected of swallowing dysfunction. Hence, numerous clinical bedside approaches, such as neurological examination [10,11], WST [2,12], swallowing provocation test [13], and cough reflex [14], have been used to identify or predict swallowing dysfunction. Correlated with VFES, the sensitivities of these approaches for predicting swallowing dysfunction varied from 42% to 80%. This work employed the WST because of its simplicity, high efficiency, and objectivity in assessing swallowing dysfunction. Specifically, swallowing speed and evidence of choking were selected as indicators for VFES referral. Swallowing speed has been demonstrated to slow markedly in individuals that display abnormal symptoms or signs during swallowing [6]. Furthermore, a swallowing speed of below 10 ml/s was proposed as the cutoff point for defining swallowing dysfunction [7]. This phenomenon probably results from the compensated or adapted mechanics for disordered swallowing [6]. Additionally, individuals with swallowing dysfunction may reduce the size of the swallowed bolus to reduce the risk of aspiration, thus slowing their swallowing speed [15]. This study successfully validated the accuracy of swallowing speed for detecting swallowing dysfunction, revealing a sensitivity of 85.5%, which exceeded that reported in the previous literature [2]. In our study, selection bias primarily accounted for the relatively low specificity by using swallowing speed to determine swallowing dysfunction. Since all study participants had perceived symptoms or signs of swallowing disorder, a lower specificity was inevitable, and it is acceptable that only four of the subjects displayed normal VFES results. Besides neurological impairment, factors related to gender and age may also contribute to altered swallowing speed. For instance, the study defined a swallowing speed below 10 ml/s as abnormal, following the definition used by Nathadwarawala et al. [6,7], whose study included subjects below 70 years old. However, the mean age of the subjects in our study was 71.7 years old (range years). Since aging is normally associated with decreasing swallowing speed [16], using a swallowing speed of 10 ml/s as a reference is likely to underestimate the swallowing abilities of our participants, biasing the findings. Furthermore, swallowing speed is normally slower in females than in males [11]. In the present study, females comprised 25.4% of the samples, and their swallowing abilities were probably also underestimated by using the same speed of 10 ml/s as a reference. Although the statistical results in the present study were not corrected for age and gender, they were consistent with the reports in the literature [2,6,7,12]. Future works will focus more carefully on the above issues. Another centralfeature of this study was to determine the sensitivity of using choking, including coughing and a wet-hoarse voice, to detect penetration and aspiration. The sensitivity found by this study was 47.8%, relatively low compared with other studies [2,5,11,17 19]. This finding thus implies that choking is a poor indicator of aspiration and penetration and is probably attributed partly to the presence of silent aspiration in choking-free cases. Similarly, in contrast with the statement of DePippo et al. [2], recent studies also recommend against using choking as an indicator of aspiration or as an alternative to VFES [12,13]. Moreover, the sensitivity and specificity of applying choking to predict aspiration in VFES was further decreased in this study, implying that choking is related not only to aspiration but also to penetration. Although less reliable in predicting the occurrence of aspiration because of its low sensitivity, choking in the 100-mlWST had a specificity of up to 91.7% for predicting aspiration. Accordingly, choking in the 100-ml WST is an excellent monitor for following up individuals who were already identified as having aspiration. For these cases, frequent estimates of the progress of aspiration are essentialto improved treatment strategy. Despite gold standard status in assessing aspiration, repeated VFES within a short intervalis not acceptable because of the danger of excessive radiation exposure. Instead, choking in the 100- mlwst can be used as an alternative approach to followup on the aspiration status. This study recommends applying choking in the 100-ml WST to clinical followup rather than initial screening of aspiration. In conclusion, this study explicitly measured the validity of using a 100-ml WST for screening VFES referral. Based on its high sensitivity and simplicity, estimating swallowing speed in the 100-ml WST appears to a usefulbedside toolfor the early detection of swallowing dysfunction. Furthermore, the presence of choking in the 100-mlWST may be a

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