INMUNOGLOBULINAS DEL HUEVO EN LA DIETA DE LECHONES DESTETADOS

Videofluoroscopy has been used for swallowing assessment since the 1980s (Logemann, 1998). Some have termed it gold-standard instrumentation for swallowing evaluation (Rugiu, 2007). A videofluoroscopic swallowing study is a “dynamic continuous radiological examination of the anatomy and function of the oral cavity, pharynx and UES opening” (Rommel & Hamdy, 2016, p. 49). Using videofluoroscopy, two-dimensional imaging of the oral, pharyngeal, and oesophageal stages of swallowing can be performed in lateral and anterior-posterior plane (Logemann, 1998; Steele, 2015). Videofluoroscopy provides temporal and spatial information about swallowing biomechanics. Further, observation of bolus flow during swallowing is possible by use of a radio-opaque bolus, such as barium (Logemann, 1998; Rugiu, 2007; Steele, 2015). Visualisation of the bolus allows for evaluation of bolus transit times and of the timing of individual biomechanical features in relation to bolus position. Additionally, bolus penetration and aspiration into the airway or bolus residue can be visualised (Logemann, 1998; Rugiu, 2007). The fluoroscopic images may be analysed frame-by-frame or in real-time after completion of the study (Logemann, 1998; Rugiu, 2007). Analysis of videofluoroscopic images may be qualitative or quantitative; the use of qualitative interpretation methods is more common in clinical practice, however qualitative methods are limited by subjectivity (Daniels & Huckabee, 2014; Rommel & Hamdy, 2016).

Assessment of UES Function

Qualitative and quantitative videofluoroscopic evaluation of UES function during swallowing may inform about extent, duration, and timing of UES opening (Kendall & Leonard, 2002; Y. Kim, Park, Oommen, & McCullough, 2015) and of hyolaryngeal displacement (Sia, Carvajal,

Carnaby-Mann, & Crary, 2012; Steele et al., 2011). Protocols used for qualitative interpretation may include binary or multilevel ratings of swallowing events such as UES opening and hyolaryngeal excursion. A binary rating for UES opening extent may include the categories “incomplete” or “complete” while a multilevel ratings for the timing of UES opening may comprise the categories “early”, “normal”, or “late” (Stoeckli, Huisman, Seifert, & Martin- Harris, 2003, p. 54). A protocol that aims for more objectivity by assigning numbers to qualitative ratings is the MBS-Imp measurement tool for swallow impairment (Martin-Harris et al., 2008). In contrast, objective measures are used for quantification of temporal and spatial aspects of UES opening (Kendall & Leonard, 2002; Y. Kim et al., 2015; Leonard et al., 2000), and of hyolaryngeal excursion (Leonard et al., 2000; Sia et al., 2012; Steele et al., 2011). A reported example of a timing measure of UES opening is “the time at which the pharyngo- esophageal sphincter has reached its widest opening” (Kendall et al., 2000, p. 75) while a spatial measure of UES opening is “maximal distention for bolus passage” (Leonard et al., 2000, p. 147) (Figure 7).

Figure 7. Videofluoroscopic lateral image of the head and neck. The white line represents upper oesophageal sphincter (UES) opening diameter at maximal distention (Leonard et al., 2000)9_.

9 _{From “Structural displacements in normal swallowing: A videofluoroscopic study” by Leonard et al. (2000),}

For quantitative measurements, image calibration is required to account for image magnification and distortion (Sia et al., 2012; Steele, 2015). Further, for measurement of hyoid excursion, the use of reference axes has been reported to account for head movements during swallowing (Y. Kim & McCullough, 2008; Logemann et al., 2000; Paik et al., 2008). Thus, when comparing data across studies, it is important to appreciate these important methodological distinctions (Sia et al., 2012).

The reliability of videofluoroscopy for evaluation of UES function may be limited, especially with regard to intra- and inter-rater reliability of perceptual, subjective ratings of UES opening and/or hyolaryngeal excursion (Bryant, Finnegan, & Berbaum, 2012; D. H. Kim et al., 2012; McCullough et al., 2001; Scott, Perry, & Bench, 1998; Stoeckli et al., 2003). For example, there is evidence for insufficient inter-rater reliability of measurements of UES and hyolaryngeal excursion (kappa = 0.03 - 0.42), even when raters could discuss the videofluoroscopic recordings with team members not involved in the study (Stoeckli et al., 2003). Of note, in this study, raters were not informed about the clinical history of the patients. However, in clinical practice, videofluoroscopic examination commonly follows clinical swallowing assessment and information is paired for interpretation. Thus, reliability was potentially decreased due to isolated information, but requires confirmation in future research. Martin-Harris and colleagues reported high intra- and inter-rater reliability for trained raters for videofluoroscopic analysis using the modified barium swallowing study evaluation tool that specifically targeted increased objectivity in qualitative ratings (Martin-Harris et al., 2008). While reliability may be problematic for subjective ratings, there is evidence to suggest good reliability for objective temporal and spatial measures of UES function (Leonard, 2018; R. Leonard, K. Kendall, & S. McKenzie, 2004a; Leonard et al., 2000; Martin-Harris et al., 2008; Nordin, Miles, & Allen, 2017). Good inter-rater reliability was reported for maximum hyoid displacement (r > 0.90), hyolaryngeal approximation (r = 0.75), maximal extent of UES opening (r > 0.90), and UES opening duration (r > 0.90) in healthy subjects (Leonard, 2018; Leonard et al., 2004a; Leonard et al., 2000). Further, good reliability of hyoid excursion and laryngeal displacement was documented for patients with dysphagia (intra-rater ICC > 0.92, inter-rater ICC = 0.77) (Sia et al., 2012). A study by Nordin and colleagues (2017) showed an association between increased reliability and increased experience with derivation of objective measures. This highlights the importance of rater training for optimised reliability.

Advantages and Limitations

Videofluoroscopic imaging provides numerous advantages in the assessment of UES function. It allows for evaluation of UES opening in the context of pharyngeal biomechanics, including hyolaryngeal excursion; this is of value as pharyngeal swallowing is a coordinated sequence of events (Rugiu, 2007). Information about bolus flow through the UES can be gained and rehabilitation or compensation strategies for UES dysfunction, such as effortful swallowing or head rotation can be trialled and evaluated during imaging (Rugiu, 2007). Despite the undisputed value of videofluoroscopic swallowing studies, there are limitations to consider. Videofluoroscopic imaging does not provide information about underlying aetiologies for UES dysfunction, such as failed intra-swallow UES relaxation versus impaired hyolaryngeal excursion; thus, its use for differential diagnostics of UES impairment is limited. Further, quantification of pharyngeal residue as a potential consequence of UES dysfunction is limited by the two-dimensional nature of videofluoroscopy (Pearson, Molfenter, Smith, & Steele, 2013). Videofluoroscopy exposes patients to radiation (Daniels & Easterling, 2017; Rommel & Hamdy, 2016); hence, its use for prolonged studies, repeated testing or for frequent application in vulnerable patient populations, such as children, is limited (Rugiu, 2007). Further, subjects with movement impairment or poor cooperation may not be eligible for this procedure (Daniels & Easterling, 2017; Rugiu, 2007). As videofluoroscopy is an instrument with limited mobility (Rugiu, 2007), bedside videofluoroscopic evaluation for patients who are critically ill is not possible. Further, access to a videofluoroscopy suite is potentially challenging for patients living in non-urban areas as this technology may be difficult to access (Rugiu, 2007).