Yoshiko Takei

Acoustic characteristics of voluntary expiratory sounds after swallow for detecting dysphagia

This research was designed to investigate the acoustic characteristics of voluntary expiratory sounds after swallow for detecting dysphagia. Forty-nine patients with complaints of swallow difficulty received a videofluorographic (VF) examination. They were divided into three groups: nine who did not have any apparent disease (Group N), 22 patients with head and neck cancer (Group H&N) and 18 patients with other diseases including cerebrovascular disease (Group OD). After liquid barium swallows, they exhaled voluntarily without voicing. Videofluorographic findings were classified into four groups: normal (Normal), acceptable swallow (Acceptable), swallow with residue (Resid) and swallows with penetration or aspiration (Pen/Asp). The duration of expiratory sounds was measured on the time waveform. Frequency characteristics of expiratory sounds were obtained using one-third octave band analysis ranging from 62·5 to 2000·0 Hz of central frequency. The averaged level of the 1000·0-Hz band was chosen as the reference band level (RB level). The revised averaged level of each band was obtained by subtracting the RB level from the averaged level of each band. Zero decibel of the revised magnitude of the 125·0-Hz band was set as the critical value to differentiate dysphagia (Resid or Pen/Asp) from no dysphagia (Normal or Acceptable). Comparison of this assessment with VF findings showed a significant percentage agreement (85·4%). These results suggest that frequency characteristics of post-swallow expiratory sounds can differentiate dysphagia from no dysphagia among multiple dysphagic patient groups.

Accuracy of cervical auscultation in detecting the presence of material in the airway

Several studies have investigated the accuracy of cervical auscultation (CA). However, both the sensitivities and the specificities of CA in detecting dysphagic conditions varied widely among these studies. These wide variations of the accuracy of CA might be caused by differences of the targeted sounds, such as the expiratory sound (ES) and/or swallowing sound (SS). Forty‐six dysphagic patients were served as subjects. Patients who had unoccluded tracheostoma and patients who could not follow the instructions were excluded. During the videofluorographic swallowing study (VFSS), the subjects swallowed 3 ml of yogurt containing barium sulfate. The VFSS images were recorded with acoustic signals including both the swallowing and respiratory sounds detected by our method. Classification of the VFSS images was decided by consensus of the three dentists using a penetration‐aspiration scale (PAS). Recorded VFSS images were classified into the following 2 groups based on PAS: “no or minimum risk group”: PAS1–2; and “possible risk group”: PAS3–8. As a result of the classification of VFSS findings, 30 samples were evaluated as no or minimum risk group and 16 as possible risk group. Twelve observers including 10 dentists other than 3 dentists who evaluated VFSS images and 2 speech pathologists auditorily diagnosed “negative” and “positive.” Sensitivity, specificity, and intra‐rater reliability was calculated for the 3 types of acoustic samples. The sensitivity of the intra‐rater reliability was 60.3% for ES, 76.6% for SS, and 89.9% for ES + SS. The sensitivity of intra‐rater reliability of ES + SS samples was significantly higher than that of ES (p < .01) and SS (p < .05). The sensitivity of intra‐rater reliability of SS was significantly higher than that of ES (p < .01). The specificity of the intra‐rater reliability was 53.7% for ES, 50.3% for SS, and 44.5% for ES + SS. ES + SS might be most useful for detecting the presence of material in the airway.

Clinical inter-rater reliability of postural control techniques

Effectiveness of postural control techniques to compensate for oropharyngeal dysphagia have been recommended and used by several clinicians. However, the inter‐rater reliability of these techniques is not well understood. The purpose of this study was to clarify the ambiguity of postural control techniques using statistical analyses. A total of 50 clinicians involved in dysphagia treatment participated in this study, where a healthy male served as the simulated patient. The following clinically used postures were measured by two investigators on two separate days: chin down, right/left incline, and right/left rotation. Postural angles were measured twice by two investigators on each day. Data obtained for the angle of each posture were visually displayed. Data from both investigators were assessed for each posture using the Youden plot, which analyzes data variability for systematic errors and accidental errors separately. The correlation coefficient for examining the measurement error between investigators was calculated. The results showed considerable variation between clinicians regarding the postures used, and significant differences were noted each day. The correlation coefficient for a total of four measurements was more often lower on Day 2 than that on Day 1. The details of the instructions provided by clinicians were not fixed, and the same specified posture was not reproduced even when instructions were provided to the same subject. These findings suggest poor inter‐rater reliability because of the variability of selected postures when using statistical analyses. Therefore, standardized postures need to be developed that can be easily measured and reproduced.