Can Bedside Assessment Detect Aspiration - Essay Example

Introduction Many studies have examined the effectiveness of bedside examination for detecting aspiration (Tohara et al., 2003). Tests like water-swallowing test, cervical auscultation and Repetitive Saliva Swallowing Test (RSST) are either not accurate or requires skilled examiners (Tohara et al., 2003). Fiberoptic endoscopic examination of swallowing (FEES) is highly sensitive for detecting aspiration but cannot provide all the details of swallow physiology. FEES also requires sophisticated instrumentation and a skilled examiner (Tohara et al., 2003). Videofluoroscopic swallowing examination (VFSE) has traditionally been the gold standard, because of its ability in assessing oral, pharyngeal, and cervical esophageal stages of swallowing. However, there are issues of transportation and radiation (Tohara et al., 2003). VFSE is also not a natural procedure since it examines swallowing in ideal circumstances, in an upright posture and using boluses that are not similar to normal food and liquid intake (Tohara et al., 2003). The procedure also requires coaching. Both FEES and VFSE are also expensive (Tohara et al., 2003). The aim of this essay is to evaluate if there are any bedside assessment techniques, which can detect aspiration, and are sufficiently specific and sensitive. The availability of such a technique can be cost effective and easily available, unlike the disadvantages of the traditional instrumental techniques. One of the two most commonly recommended bedside tests for detecting aspiration in tube-fed patients is adding dye to the formula and observing its appearance in tracheobronchial secretions. The dye, which is used, is blue food coloring or methylene blue. The other test involves using glucose oxidase reagent strips to test tracheobronchial secretions (Metheny & Clouse, 1997.) Several studies indicate that the dye method is far less sensitive than the glucose reagent method (Metheny & Clouse, 1997). There are also reports of the potential harm due to the dye (Metheny & Clouse, 1997). The specificity of the glucose reagent is also less, and the cost is also greater. In view of these limitations, the use of these tests are not justified (Metheny & Clouse, 1997.) Shaw et al (2004) performed a new multidisciplinary approach to bedside assessment, involving physiotherapists (PT) performing bronchial auscultation (BA) in combination with the speech and language therapists (SLT) clinical examination of dysphagia. Although the BA team proved unreliable in detecting the presence of aspiration in the group of patients identified by VF as aspirating, it was able to identify patients who were not aspirating. Specificity was found to be 88%, whereas sensitivity was 45%. From this, the study concluded that BA is a potentially useful clinical tool, but requires further research. Lim et al., (2001) aimed to determine the accuracy of bedside clinical methods compared with fiberoptic endoscopic examination of swallowing (FEES) in detecting aspiration in acute stroke patients. Fifty patients swallowed 50 ml of water with measurement of their oxygen saturation levels before and after swallowing 10 ml of water using a pulse oximeter. Later, an FEES assessment was made on all patients, with follow up for evidence of aspiration pneumonia. When both these tests were combined together into one test, called “bedside aspiration,” the sensitivity increased to 100% with a specificity of 70.8%. From this study, it was concluded that the oxygen desaturation test combined with the 50-ml water swallow test can be used as a screening test to identify all acute stroke patients at risk of aspiration. It has been shown that almost 40% of those patients who aspirate is missed by clinical bedside assessment, these patients are called the silent aspirators. Selina et al., 2001, compared the 50-ml water swallow test, the oxygen desaturation test, and the combination of the two defined as “bedside aspiration” with FEES examination. The results using the 50-ml water swallow test had a sensitivity of 84.6% and specificity of 75%. The study concluded that the combination of 50-ml water swallow test and oxygen desaturation on swallowing as a single test of clinical assessment of aspiration is a sensitive screening instrument for identifying acute stroke patients with clinically significant aspiration. The combined test allowed also helps to detect the silent aspirators. This could be a powerful and easily performed bedside dysphagia screening tool in patients with acute stroke (Selina et al., 2001.) The limitations of the study included: the use of different volumes of water in the 50-ml water swallow test and the oxygen desaturation test, which should ideally be the same; non-measurement of pulse oximetry during the 50-ml water swallow test, which could have allowed determining the test–retest reliability between the 50-ml water swallow test and oxygen desaturation test; and finally, the water swallow and oxygen desaturation tests were done before FEES and not simultaneously (Selina et al., 2001). Of the several clinical features associated with dysphagia, the presence a “wet” voice is also significant. This refers to as a gurgly voice being produced through moisture (Warms & Richards, 2000.) Warms & Richards, 2000, aimed to determine if wet phonation could predict penetration and/or aspiration of ingested material. The results suggested that there was no association between the presence of a wet voice and penetration or aspiration of prandial material after a swallow. Therefore, wet phonation by itself was not considered diagnostic in detecting prandial penetration/aspiration by the bedside, but it may identify those with dysphagia at a risk of penetrating/aspirating any type of material, not just prandial material. More research is indicated on wet phonation (Warms & Richards, 2000.) Many studies have shown a relation between arterial oxygen saturation (SpO2), measured by pulse oximetry, and aspiration. Sherman et al., 1999 explored whether bedside pulse oximetry can help in the assessment of pharyngeal phase dysphagia. Those patients who had aspiration or penetration without clearing had a significant decline in SpO2, whereas those patients who penetrated but cleared or had no penetration, showed no change in SpO2. This indicates that bedside pulse oximetry may be an efficient and cost-effective technique in the diagnosis and treatment of dysphagia. Some limiting factors of the study include the inability to generalize to younger patients. Also, data interpretation may be more complex in patients with concomitant illnesses affecting oxygen saturation. Leder, 2000, aimed to investigate any changes in arterial oxygen saturation (SpO2), heart rate, and blood pressure during simultaneous objective confirmation of aspiration with Fiberoptic Endoscopic Evaluation of Swallowing (FEES). However, there were no significant differences in SpO2, based on aspiration status or oxygen requirements. Therefore, it was concluded that changes in SpO2, heart rate, or blood pressure as indirect objective markers of aspiration are not useful (Leder, SB, 2000.) If a VFSS test is not possible, then a non-videofluorographic (non-VFG) clinical assessment of swallowing can be done. Tohara et al., 2003, studied three non-VFG tests for assessing risk of aspiration: the water swallowing test, the food test, and the X-ray test. The summed scores of all three non-VFG tests had a sensitivity of 90% for predicting aspiration and specificity of 71% for predicting its absence. The summed scores of the water and food tests (without X-ray) had a sensitivity of 90% and specificity of 56%. Only the water test, when taken alone, had high specificity (88%). Although these non-VFG tests have limitations, they may be useful when VFSS is not feasible, and may also be useful to identify which dysphagia patients need VFSS. Wu et al., 2004, used comparison with videofluoroscopic examination of swallowing (VFES) to examine the validity of a 100-ml water-swallowing test (WST) in assessing swallowing dysfunction. The sensitivity of swallowing speed in detecting the swallowing dysfunction in this test was found to be 85.5%, and the specificity was 50%. The conclusion of this study was that swallowing speed is a sensitive indicator for identifying patients at risk for swallowing dysfunction. In addition, choking in the test may be a potential indicator for follow-up aspiration. Sitoh et al., 2000, conducted a study to know the usefulness of a simple bedside swallowing test to detect previously undiagnosed dysphagia; to know if there was agreement between the doctors assessments with that of the speech therapist; to know the impact on subsequent feeding modality; and predicting the risk of subsequent pneumonia. The results indicated that the doctors assessment agreed with that of speech therapist. Both cough on swallowing and delayed swallowing were associated with an increased risk of developing pneumonia. Therefore, it was concluded that a bedside swallowing test is effective in detecting undiagnosed dysphagia but further investigation is required. However, another study by Smithard et al., 1998, found that bedside assessment of swallowing is not sensitive to be used for screening in acute stroke. Smith et al., 2000, assessed the value of pulse oximetry and bedside swallowing assessment in the detection of aspiration compared with videofluoroscopy (VF). They found that this combination gave a positive predictive value of 95%. They concluded that screening by saturation assessment followed immediately by bedside swallowing assessment would improve the detection of dysphagia while allowing oral intake in patients with stroke. Daniels et al., 2000, identified 6 clinical indicators to distinguish acute stroke patients at increased risk of aspiration on VSS from those at limited risk. These indicators are: abnormal volitional cough, abnormal gag reflex, dysphonia, dysarthria, voice change after swallow, and cough after swallow. Identification of two or more clinical features would distinguish patients at risk of prandial aspiration from those patients at minimal risk. However, larger group studies are required. Leder & Espinosa, 2002, compared the same 6 clinical indicators with FESS, and found that the clinical indicators underestimated the risk of aspiration in those at risk of aspiration and overestimated the risk of aspiration in those without a risk of aspiration. McCullough et al., 2001, in their study, identified two indicators, which were reliable, sensitive, specific, and have acceptable A0 and chi-square values for detecting aspiration. These are: the presence of a spontaneous cough during test swallows, and an overall estimate of the presence of aspiration. However, more such studies are required. Conclusion On analysis of all the bedside tests, the following conclusions were reached: the use of dye and glucose oxidase reagent strip is not justified. Measurement of changes in SpO2, heart rate, or blood pressure values, as indirect objective markers of aspiration is not useful. Bronchial auscultation is a potentially useful clinical tool, but requires further research. Wet phonation by itself is not diagnostic in detecting prandial penetration/aspiration by the bedside, but it may be helpful in identifying those with dysphagia at a risk of penetrating/aspirating any type of material. Bedside pulse oximetry may be an efficient and cost-effective technique. A combination of pulse oximetry and bedside swallowing assessment gives a positive predictive value of 95%. Non-VFG tests have limitations, but may be useful for assessing patients when VFSS is not feasible. In the 100-ml water-swallowing test, swallowing speed is a sensitive indicator for identifying patients at risk for swallowing dysfunction. In addition, choking in the test may be a potential specific indicator for follow-up aspiration. Bedside swallowing test is an effective screening tool to detect undiagnosed dysphagia but further investigation is required. Clinical indicators (abnormal volitional cough, abnormal gag reflex, dysphonia, dysarthria, voice change after swallow, and cough after swallow) may also be used. The identification of two or more clinical features would distinguish patients at risk of prandial aspiration from those patients at minimal risk. However, larger group studies are required. Two indicators, which were reliable, sensitive, specific, with acceptable A0 and chi-square values for detecting aspiration are the presence of a spontaneous cough during test swallows, and an overall estimate of the presence of aspiration. However, more such studies are required. The 50-ml water swallow test combined with oxygen desaturation test (bedside aspiration) has a sensitivity of 100% with a specificity of 70.8% From this it is clear that although there are numerous bedside assessment methods to detect aspiration, none of the currently available bedside tests are sufficiently sensitive and specific. In order to be clinically useful, a test should have high specificity (low false positive rate) and high sensitivity (low false negative rate). Most studies have some limitations and further research is needed to confirm their efficacy. References Daniels, S.K, Ballo, L.A, Mahoney, M.C, Foundas, A.L (2000). Clinical predictors of dysphagia and aspiration risk: outcome measures in acute stroke patients. Arch Phys Med Rehabil. 81:1030-3. Leder, S.B (2000). Use of arterial oxygen saturation, heart rate, and blood pressure as indirect objective physiologic markers to predict aspiration. Dysphagia. 15:201–205. Leder, S.B, Espinosa, J.F (2002). Aspiration Risk After Acute Stroke: Comparison of clinical examination and Fiberoptic Endoscopic Examination of Swallowing. Dysphagia 17:214-218. Lim, S.H, Lieu, P.K, Phua, S.Y, Seshadri, R, Venketasubramanian, N, Lee, S.H, Choo, P.W (2001). 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