Aspiration pneumonia (pneumonia caused by swallowed solids or liquids entering the lungs) is a leading cause of morbidity and mortality in the world, especially among the elderly and those with neurologic disorders. It is most often caused by the presence of a swallowing disorder (dysphagia), which is itself usually only discovered after the fact when a patient presents with an episode of aspiration pneumonia and then undergoes testing. Selected high-risk patients (e.g., stroke victims) are also routinely sent for testing for the presence of dysphagia. At present, the two most common methods for testing are the modified barium swallow (MBS) and fiberoptic endoscopic evaluation of swallowing (FEES). MBS requires radiation exposure and can only be performed in hospital or mobile radiology facilities. FEES is an invasive procedure that can be uncomfortable and requires specially trained personnel.
The possibility of detecting the presence of dysphagia by listening to the sounds produced during a swallow has been discussed in the medical literature for decades. However, it has not been used due to technical challenges (the lack of a good “stethoscope-like” device to listen with) as well as the lack of an understanding of how to interpret the sounds that are obtained.
This study was undertaken to determine whether it was worthwhile pursuing further research into swallow sounds and dysphagia. The study had several goals. First, assess how feasible it is to actually capture swallow sounds in a clinical setting and what the technical requirements for a good recording are. Second, see if the recorded sounds can be correctly synched to the video of a simultaneously performed modified barium study (MBS) and what it takes technically to accomplish the synching. Third, see what additional information about the swallow event can be obtained by MDPS processing. Lastly, using the synched audio-video, begin to learn what each component of the recorded swallow sounds means by correlating the swallow sounds to the physiologic swallow events captured on the MBS video.
A total of four volunteers were studied. The results showed that BMHT’s novel swallow sound capture device could successfully make high quality recordings of swallow events in a technically feasible manner; the sounds can be accurately correlated to the MBS video; and that MDPS processing adds considerable value to the analysis of the sounds. Perhaps most important, it was shown that specific, easily identifiable acoustic events correlated well with the physiologic swallow events taking place in this group of normal subjects.
These results indicated that it would be worthwhile to continue with a larger study, including abnormals (i.e., patients with dysphagia), with the ultimate goal of eventually defining criteria with high sensitivity and specificity for the presence or absence of dysphagia based upon a bedside acoustic swallow examination.