Susan G. Butler, Andrew Stuart, L. Xiaoyan Leng, Catherine Rees, Jeff Williamson, Stephen B. Kritchevsky
5 min
Flexible endoscopic evaluation of swallowing (FEES) is a standard clinical tool for assessing swallowing safety. However, clinical protocols for FEES—such as the type of liquid used, the volume of the bolus, and the method of delivery—are not standardized. This study aimed to determine how these variables influence swallowing outcomes in healthy older adults, providing a baseline for what constitutes normal versus abnormal swallowing in this population.
Researchers conducted a prospective study with 76 healthy volunteers aged 61 to 90. Participants underwent FEES while consuming various liquids (water, skim milk, 2% milk, and whole milk) at different volumes (5, 10, 15, and 20 mL) using both cup and straw delivery methods. Swallowing performance was measured using the 8-point Penetration Aspiration Scale (PAS), where higher scores indicate more severe penetration (material entering the airway above the vocal cords) or aspiration (material passing below the vocal cords).
These findings suggest that clinicians should use a variety of liquid types and bolus volumes during FEES to ensure an accurate assessment. Relying solely on water may underestimate a patient's risk, while testing only with thicker liquids might lead to overly restrictive diet recommendations. The study highlights that isolated aspiration events in older adults should be interpreted carefully, as they may not always indicate pathological dysphagia.
OBJECTIVES/HYPOTHESIS: Although flexible endoscopic evaluation of swallowing (FEES) is an established diagnostic tool, little data exist on the effects of varying liquid types on the swallowing outcomes in healthy older adults. STUDY DESIGN: Prospective. METHODS: Seventy-six healthy older adult volunteers participated (i.e., 18, 28, and 30 volunteers in the 7th, 8th, and 9th decades of life, respectively). The effects of age, sex, liquid type (i.e., water, skim, 2% milk, or whole milk), delivery method (i.e., cup or straw), and volume (i.e., 5, 10, 15, or 20 mL) on Penetration Aspiration Scale (PAS) scores were assessed during FEES. RESULTS: Penetration and silent aspiration were observed in 83% and 28% of the participants, respectively. This represented 19% and 3% of participants' 2,432 swallows, respectively. Liquid type (P = .0001), bolus volume (P = .02), and delivery method (P = .04) significantly affected PAS scores. PAS scores were significantly (P < .05) greater for milk versus water swallows, whole- versus skim-milk swallows, 10- and 20-mL versus 5-mL volumes, and straw versus cup delivery. The risk for aspiration increased by approximately two-, three-, and seven-fold with maximal increases in bolus volume, fat content of liquids, and age, respectively. CONCLUSIONS: Occasional aspiration may be an underappreciated phenomenon during FEES in healthy older adults. In addition, milk yielded a higher likelihood of aspiration than water. Accordingly, different liquid types, bolus volumes, and delivery methods should be used to ensure an accurate assessment of aspiration status in healthy older adults.
Alex: So a clinician testing with five milliliters of water from a cup is essentially running the easiest possible scenario.
Sam: Best-case scenario, yes. And if that's the only condition tested, you can miss a patient who would struggle significantly with a more viscous, larger-volume bolus in everyday life. That's a meaningful diagnostic blind spot.
Alex: But here's what I keep coming back to—if 28% of healthy adults are aspirating under these conditions, how do we interpret that clinically? Is this a red flag, or just a feature of aging?
Sam: That's the load-bearing limitation of the paper. There are no longitudinal clinical outcomes. We know these healthy adults aspirate under stress conditions, but we don't know whether that correlates with increased pneumonia incidence, or whether the airway clearance mechanisms in otherwise healthy people handle it without consequence.
Alex: So we have a tool sensitive enough to detect aspiration, but we can't yet say whether detecting it in this population actually changes what we should do clinically.
Sam: Exactly—and that ambiguity has real stakes. If every instance of silent aspiration is treated as pathology, you risk imposing overly restrictive diets that reduce quality of life without a clear health benefit. The paper doesn't resolve that tension; it surfaces it.
Alex: Which is why the authors aren't saying "water is wrong"—they're saying the protocol needs to be wider. Test across a range of viscosities and volumes to get a calibrated picture of where a patient's actual threshold sits.
Sam: That's the practical upshot. A multi-bolus protocol gives you a profile rather than a pass-fail. You can see whether someone handles water fine but struggles with milk, or whether volume matters more than viscosity for that individual. That's a much more actionable clinical picture than a single-condition screen.
Alex: And the broader methodological point is that "gold standard" in geriatric swallowing assessment may have been optimized for sensitivity to obvious pathology, not for the subtler functional decline that comes with healthy aging.
Sam: Precisely. The evidence here suggests that for geriatric populations, the diagnostic protocol needs to be as dynamic as the swallow itself. Bolus rheology isn't a nuisance variable—it's part of what you're actually measuring. Until we have outcome data linking these FEES findings to clinical events, the conservative interpretation is: broaden the test, and hold the clinical conclusions carefully.
Alex: A well-placed reminder that a negative screen is only as good as the conditions you tested. Thanks for walking through this one, Sam—and thanks to everyone listening to ResearchPod.