Silent Aspiration Risk is Volume-dependent

Abstract

Clinical swallow protocols cannot detect silent aspiration due to absence of overt behavioral signs, but screening with a much larger bolus volume, i.e., 90 cc vs. 1-10 cc, may elicit a reflexive cough in individuals who might otherwise exhibit silent aspiration. A swallow screen that maintains high sensitivity to identify aspiration risk while simultaneously reducing the false-negative rate for silent aspiration would be beneficial. The purpose of this study was to investigate whether silent aspiration risk was volume-dependent by using a 3-oz. (90-cc) water swallow challenge to elicit a reflexive cough when silent aspiration occurred on smaller bolus volumes. A prospective, consecutive, referral-based sample of 4102 inpatients from the acute-care setting of a large urban tertiary-care teaching hospital participated. Silent aspiration was determined first by fiberoptic endoscopy and then each participant was instructed to drink 3 oz. of water completely and without interruption. Criteria for challenge failure were inability to drink the entire amount, stopping and starting, or coughing and choking during or immediately after completion. Improved identification of aspiration risk status occurred for 58% of participants who exhibited silent aspiration on smaller volumes, i.e., an additional 48% of liquid silent aspirators and 65.6% of puree silent aspirators coughed when attempting the 3-oz. water swallow challenge. A low false-negative rate was observed for the entire population sample, i.e., ≤2.0%. A combined false-negative rate for participants who silently aspirated was 6.9%, i.e., 7.8% if silently aspirated liquid and 6.1% if silently aspirated puree consistency. Determination of silent aspiration risk was shown to be volume-dependent, with a larger volume eliciting a reflexive cough in individuals who previously silently aspirated on smaller volumes. A 3-oz. water swallow challenge's previously reported high sensitivity for identification of aspiration risk combined with the newly reported low false-negative rate mitigates the issue of silent aspiration risk during clinical swallow screening.

Screening Accuracy for Aspiration Using Bedside Water Swallow Tests

“…6,63 We were surprised by the omission of silent aspiration data as an outcome of the reference test related to the WST in the peer-reviewed studies included in this review, especially when this clear limitation of WSTs may result in false negatives leading to aspiration pneumonia. Although silent aspiration risk may be dependent on the volume of water presented to the patient, 64 more research is needed to validate this theory. Adverse events and outcomes from missing silent aspiration on screenings are beginning to emerge.…”

Videoendoscopic Evaluation of Saliva Aspiration in a Municipal Hospital

“…In the present study, cases in which food, regardless of the amount, passed the vocal cords and entered the trachea with no coughing were considered to be silent aspiration. However, Leder et al reported that silent aspiration is affected by the amount of aspiration [16]. There are also patients in whom coughing is considerably delayed, so a definition of silent aspiration that includes the time from aspiration until coughing is needed.…”

Silent Aspiration Risk is Volume-Dependent: Reply to Letter to the Editor

“…Further research incorporated a basic cognitive assessment [5] and oral mechanism evaluation resulting in a 3-ounce water swallow challenge protocol that has the additional advantages of reliably and safely identifying patients with aspiration risk and successfully recommending specific oral diets for different patient populations, i.e., trauma patients [6], general acute care inpatients [7], and patients with acute stroke [8]. The protocol's strengths include prospective, consecutive, and referral-based population samples that span the age range [9].We are grateful for this opportunity to clarify the misunderstanding that patients were excluded from the 3-ounce water swallow challenge due to safety issues [1]and we take umbrage at the suggestion that patients were excluded in the initial study [2] but not reported.All patients were tested with 3 ounces of water regardless of fiberoptic endoscopic evaluation of swallowing (FEES) results [2,3]. Only during FEES were 313 participants deemed unsafe to be given thin liquid and 110 participants were deemed unsafe to be given puree but all still participated in the 3-ounce water swallow challenge.…”

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Daniels[1] has raised a number of issues relevant to our 3-ounce water swallow challenge study [2] and specifically to silent aspiration risk is volume-dependent [3]. We welcome the opportunity to clarify the issues.

We were not the first to report on the utility of the 3-ounce water swallow test [4].

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