Stage Transition Duration I n Patients Poststroke

The purpose of this study was to investigate the relationship between prolonged stage transition duration (STD) and aspiration. STDs and aspiration ratings were made from videofluoroscopic examinations previously obtained for other studies. Three groups of subjects were examined: (1) 20 stroke patients who aspirated, (2) 31 stroke patients who did not aspirate, and (3) 15 normal subjects. Aspirators poststroke had the longest STD of the three groups. Furthermore, results indicated that STD correctly predicted the presence of aspiration 75% of the time and correctly predicted the absence of aspiration in stroke patients 93% of the time. Nonaspirating stroke participants had similar patterns to the normal subjects. Implications for these findings are discussed. Youngsun Kim & Gary H. McCullough (2007) "Stage Transition Duration In Patients Poststroke" Dysphagia #22 pp.299-305 Version of Record Available At www.springer.com [DOI: 10.1007/s00455-007-9085-4] The primary purpose of swallowing is to safely transport food from the mouth to the stomach. Safe and proper ingestion of food and liquid is critical to survival. While nutritional status can often be maintained by nonoral means, quality of life may be tragically diminished by such mechanical alimentation. Swallowing can be divided into three physiologic stages: oral, pharyngeal, and esophageal [1]. As a bolus is propelled from the oral cavity into the pharyngeal cavity, the pharyngeal stage of the swallow should be triggered. Triggering of the pharyngeal swallow means that the following physiologic events should occur: (1) velopharyngeal apposition to the posterior pharyngeal wall to seal the nasopharynx and prevent food or liquid from entering the nasopharynx; (2) elevation and anterior movement of hyoid bone and thyroid cartilage which contribute to epiglottic closure and the opening of the upper esophageal sphincter (UES); (3) the closure of true and false vocal folds and anterior tilt of the arytenoids to protect the airway from penetration or aspiration of the bolus; and (4) opening of the cricopharyngeal sphincter to allow passage of the bolus into the esophagus [2]. Meanwhile, the bolus is propelled downward by initial oral and tongue base force in conjunction with pharyngeal constrictors. The bolus passage from the oropharynx into the hyopharynx can be referred to as ‘‘the stage transition’’ [3]. This is not to suggest that it is the only transition that occurs between stages of swallowing; the transition between the pharyngeal stage and the esophageal stage is important and time-dependent as well. Still, in this case the stage transition refers specifically to the transition of the oral stage into the pharyngeal stage. The end of the oral stage has been defined radiographically in this study as the time when any barium passes the ramus of the mandible [3]. It has been reported previously that this is the area that most closely correlates with the anatomical point of reference targeted, the anterior faucial pillars [1]. The initiation of the pharyngeal phase, as defined in association with STD [3], is defined as the time when the hyoid begins its anterior excursion. Thus, stage transition duration (STD) is the time from first barium passing the ramus of the mandible until the beginning of maximum anterior hyoid excursion. Any lag in time between the bolus passing the ramus of the mandible and the initiation of anterior hyoid excursion then can be referred to as ‘‘stage transition Introduction duration.’’ If the stage transition is zero seconds, then hyoid excursion began simultaneously with the bolus entering the pharynx. If the stage transition is a negative number, this means hyoid excursion began before the bolus ever reached the pharynx. Robbins et al. [3] reported that in normal, young adults, STDs of 0 or negative were the norm. In other words, the initiation of hyoid excursion began before or when the bolus passed the ramus of the mandible. For older participants, however, this was not the case. Rather, hyoid excursion began after the bolus had entered the pharynx, resulting in a positive number for STD. The participants in the Robbins et al. study were tested with 2-ml boluses, limiting comparisons of results. Still, STD for older normals was greater than 0 and approached 0.3–0.4 s, similar to our data [5]. The delay in hyoid excursion leaves the airway unprotected for a prolonged period of time, which increases the risk of aspiration; but it must be clarified that aspiration did not typically occur as a result of normal aging processes which slowed the stage transition. Many stroke patients with dysphagia also exhibit prolonged transitions between the oral and pharyngeal stages. Robbins and Levine [4] reported that those who suffered a right cerebral vascular accident (CVA) have been observed to have more problems with the timing of pharyngeal stage components and subsequent penetration/aspiration than those with a left CVA. Patients with other types of cerebrovascular disease such as lateral medullary syndrome may also exhibit severe delays in the triggering of pharyngeal swallow. With bilateral damage they may have no swallow response at all. Other patients at risk for delays in transition between the oral and pharyngeal stages include those with disorders such as traumatic brain injury (TBI), Parkinson's disease, multiple sclerosis, bulbar palsy, and head and neck cancer [1]. Adult dysphagic patients with these problems showed a prolonged transition between the end of the oral stage and the beginning of the pharyngeal stage, or the initiation of the pharyngeal swallow, which have been linked to aspiration. In addition, the presence of a delayed initiation of the pharyngeal stage may be linked to negative health outcomes from aspiration. At this point it seems prudent to emphasize that aspiration can occur for many reasons, of which prolonged STD is only one. Reduced hyolaryngeal excursion, weak tongue-base propulsion, weak pharyngeal wall propulsion, or early, late, or reduced opening of the UES can all lead to aspiration. However, thin-liquid aspiration before or during the swallow does result in aspiration in a high percentage of stroke patients; this is the focus of this article. While normative data have been collected for STD in normal populations [3, 5], to our knowledge no studies have compared stroke patients with and without aspiration. The purpose of this study was to evaluate the oropharyngeal stage transition duration in three groups of subjects. The three groups were as follows: (1) 20 stroke patients who aspirated (aspirators), (2) 31 stroke patients who did not aspirate (nonaspirators), and (3) 15 normal subjects within the appropriate age range for stroke patients. Normal subjects were between 60 and 80 years of age (mean = 76.93), which was the age range for 90% of the sample of stroke patients who aspirated (mean = 69.80) and who did not aspirate (65.64). Because X-ray swallow studies are necessarily short, best and worst case scenarios for oral ingestion are not always visible. We sit them upright, feed them by spoon or cup, and ask them to swallow—several times if necessary. Thus, it is entirely probable that patients exist who do not aspirate in the fluoroscopy suite but do aspirate under normal circumstances, where posture is more reclined and swallowing is not attempted on verbal cue. It is, therefore, essential to collect as much information on specific physiologic aspects of the swallow as possible to determine how much of a risk there is for aspiration or other symptoms related to dysphagia. If age-based duration measures of swallowing, like STD, can help the clinician define a range in which aspiration is more or less likely to occur for specific populations such as those who suffer a stroke, then we begin to expand our knowledge base using videofluoroscopy and, thus, feel more confident in what we may not clearly see in the fluoroscopy suite. Therefore, means and ranges of STDs that lead to aspiration versus no aspiration in patients poststroke may enhance our overall evaluation and improve our treatment recommendations. Comparisons with normal subjects may help define whether differences also exist between stroke patients and normals outside the occurrence of aspiration. If nonaspirating stroke patients are similar to normals in STD, then our distinction for prolonged and normal STDs is strengthened. Then again, perhaps a graded prolongation of STD exists from normal to nonaspirating stroke to aspirating stroke. Moreover, means and ranges of STDs, if truly different for these groups, can allow us to begin to look not only at symptoms of dysphagia, such as aspiration, but also at outcomes of health status and nutrition. Thus, quantification of STD could be an important marker that defines who is at risk for aspiration. It may also provide insight into how much prolongation is too long and when treatment or compensation should be initiated. Also, STD data will help the clinician to decide whom he/she should monitor more closely at bedside and followup. Again, this is not to suggest that STD is the only cause of Table 1. The mean and standard deviation (SD) of age (years) of the three subject groups Groups N Mean SD Range aspiration, but it is one cause and the most likely cause for aspiration before and during the swallow for patients poststroke.