Early Assessments of Dysphagia and Aspiration Risk in Acute Stroke Patients

Bedside Assessment of Swallow

Several forms of bedside swallow assessment are used to evaluate patients with an acute or recent cerebrovascular event. Some studies have involved patients with other neurological impairments, but the most common subgroup remains stroke disease.

Linden and Siebens¹² looked for clinical factors correlating with aspiration on VF. They performed a sensorimotor examination, observed swallowing and related movements, and found a high incidence of impaired pharyngeal gag and dysphonia in patients exhibiting laryngeal penetration. Splaingard et al¹³ monitored swallowing of various volumes and consistencies of food while watching for respiratory distress and compared the results with VF findings.

Horner and colleagues^11,14 used similar methods in a small sample of patients and found that a weak cough and dysphonia correlated with aspiration on VF.¹¹ Regression analysis on a larger sample showed that abnormal voluntary cough and absent gag were independently associated with aspiration.¹⁴ Stanners et al¹⁵ also studied voluntary cough, gag reflex, and dysphonia but found an association only between weak voluntary cough and aspiration. These studies are limited by small patient numbers, variable times between stroke onset and assessment, and limited statistical analyses.

DePippo et al¹⁶ compared a 3-oz water swallow test with VF, showing that patients who coughed during or after swallowing or developed a wet or hoarse voice were at risk of aspiration. They proposed the Burke Dysphagia Screening Test,¹⁷ which also considered features such as stroke site and difficulty with meals. Timed tests of swallow capacity have noted the time and number of swallows required to swallow 150 mL water and have shown that delayed swallowing, coughing, or dysphonia indicated swallowing problems.⁷

Linden et al¹⁸ used a clinical “Dysarthria/Dysphagia Battery”—a clinical battery of questions about respiration, anatomy, drooling, and parenteral feeding. Factors predictive of subglottic penetration on VF included recumbent posture, abnormal phonation, abnormal laryngeal elevation, abnormal palatal gag, wet spontaneous cough, and impaired swallowing of secretions, although these predicted only two thirds of cases of subglottic penetration in a discriminant analysis.

Daniels and colleagues¹⁹ performed an oropharyngeal examination and a clinical swallowing assessment using different volumes of water while monitoring laryngeal elevation, voice quality, and coughing. The presence of ≥2 of 6 features (dysphonia, dysarthria, abnormal volitional cough, cough after swallow, abnormal gag reflex, and voice change after swallow) predicted greater dysphagia severity on VF. Logistic regression identified abnormal volitional cough and cough with swallow as independent predictors of aspiration.³ McCullough et al²⁰ used a similar assessment and found 2 reliable items for detection of aspiration: cough during swallowing and clinical estimate of the presence of aspiration.

Many researchers have assessed difficulty in drinking small volumes of water.^1,6,21 Smithard and colleagues⁴ used 5-mL aliquots and then a larger volume (60 mL), looking for dribbling, laryngeal movement, cough, dysphonia, and the time taken to finish the drink. Logistic regression identified impaired consciousness level and weak voluntary cough as independent predictors for aspiration.

Addington et al²² used a reflex cough test that evaluated the laryngeal cough reflex with nebulized tartaric acid; a weak or absent cough was regarded as predictive of aspiration risk. Teramoto and Fukuchi²³ studied patients with aspiration pneumonia and a nonrecent stroke. They developed a 2-step swallowing provocation test that involved injecting boluses (0.4 and 2 mL) of water into the suprapharynx of a supine patient and noting the latent time for swallowing. The test identified patients with aspiration pneumonia, but sample sizes were small.

Videofluoroscopy

VF (or modified barium swallow) is often regarded as the assessment of choice in testing swallowing ability.³² The patient stands or sits at 45° to 90° and consumes foods or liquids of different consistencies impregnated with barium while their swallow is imaged in lateral and anteroposterior projections. VF provides a dynamic study in which the therapist or radiologist can examine the anatomic structures and the function of the oral and pharyngeal phases of swallowing, as well as testing potential compensatory techniques.

Although VF has been proposed as the gold standard for swallow testing,^11,32 this view is not accepted universally. It cannot be undertaken in patients unable to sit upright without the use of a specialized chair, which does not replicate physiological conditions. VF protocols vary, with some workers using a standardized protocol for all patients and others performing more functional, tailor-made studies.³² The radiation exposure for VF, although regarded as acceptable,³² makes frequent test repetition inappropriate. The limited procedure duration underestimates the time required for some patients to eat and makes patient fatigue less obvious. Test-test variability has been found within normal subjects undergoing VF³³; the differences were nonsignificant, but repeated trials of each food consistency are advised.

VF is a relatively complex task to interpret, and interjudge agreement can be very variable. Smithard et al⁴ calculated percentage agreement between 2 radiologists for VF assessments as 76% (κ=0.48; 95% CI, 0.2 to 0.76), whereas Wilcox and colleagues³⁴ found only limited agreement on VF features among 10 speech and language pathologists, possibly reflecting their variable experience. Mann et al²⁹ looked at agreement between a speech pathologist and a radiologist and obtained statistics of κ=0.75±0.09 for VF diagnosis of dysphagia and κ=0.41±0.09 for aspiration.

McCullough et al³⁵ examined common VF measures and found that statistics for interjudge reliability ranged from κ=0 to 0.478; percentage agreement (calculated when κ was not possible) reached 92% on some variables. Intrajudge reliability has been greater in some studies but not in others.^35,36 Reliability ratios in 1 study were highest for aspiration, particularly for solids, and lowest for functional swallowing components.³⁶ Levels of agreement in ratings correlate with assessor experience³⁷ and improve with group discussion among assessors³⁸; similar methods of training to criteria may form a way to improve reliability.³⁵

Pulse Oximetry

Pulse oximetry provides a noninvasive method of bedside swallow testing. Most studies have found a good correlation between oxygen saturations and arterial blood samples in higher saturation ranges, with correlation coefficients quoted at 0.82 to 0.99.³⁹ The manufacturer’s accuracy for the monitors is ≈2% within the 50% to 100% saturation range. It has been suggested that aspiration causes reflex bronchoconstriction and therefore ventilation-perfusion imbalance, leading to hypoxia and desaturation.⁴⁰ Others have suggested that abnormal swallowing leads to poor breathing and ventilation-perfusion mismatching because of reduced inspiratory volumes.⁴¹

Initial reports of hypoxemia during oral feeding in neurologically disabled individuals noted associations with certain food textures, postulated to be secondary to aspiration of those foods.^42,43 Zaidi et al⁴⁰ subsequently found greater desaturation after swallowing water in acute stroke patients than in matched control subjects, and the degree of desaturation correlated with clinical assessment of aspiration risk, although statistical criticisms have been leveled at their analyses.⁴⁴ Sherman et al⁴⁵ performed pulse oximetry during VF and demonstrated significant desaturation in patients who suffered aspiration of material or penetration without clearing compared with those in whom penetration occurred with clearing or not at all, but patient numbers were small and age was very variable. Some studies have found no clear relationship between desaturation and aspiration,^44,46 but 1 study demonstrated persistently lower saturations in aspirators than nonaspirators.⁴⁴

Other workers have found that desaturation of >2% from baseline predicted aspiration on VF.^28,47 Sensitivity values ranged from 73% to 87%, and specificity values ranged from 39% to 87% (Table 2) with poor positive predictive values and possibly lower values in older subjects and those with lung disease.⁴⁷ Using an end point of penetration or aspiration rather than aspiration alone gave higher specificity and positive predictive values.²⁸ Another study compared oxygen saturation predictions with aspiration detected by fiberoptic endoscopy rather than VF and obtained better specificities and predictive values.⁴⁸ Two studies combined predictions from bedside testing and saturation monitoring and achieved good sensitivity and specificity values, particularly with aspiration or penetration as end points.^28,48

Fiberoptic Endoscopy

Fiberoptic endoscopic evaluation of swallowing (FEES) can give information on anatomy, the swallow process, pharyngeal motility, and sensory deficits.^26,49 Although aspiration cannot be seen directly, it can be inferred from residue left after swallowing or ejection of material out of the trachea after coughing.

On comparison with VF in a small sample of dysphagic patients, FEES gave sensitivity values of ≥0.88 for 3 of 4 parameters⁴⁹: specificity ranged from 0.50 to 0.92, positive predictive values were 0.69 to 0.88, and negative predictive values ranged from 0.63 to 1.00. One study found fewer aspiration pneumonias after a negative FEES result than a negative VF result although this was not statistically significant.⁵⁰ The assessment can be conducted at bedside, can be videotaped if required, and is safe and well tolerated.⁵¹ It is, however, dependent on a skilled operator and specialized equipment, and limited information is available about the oral and esophageal stages.

Other Methods

Cervical auscultation of the mechanical and/or respiratory components of swallowing, combined with bedside testing, has been compared with VF⁵² and revealed significant agreement for detection of aspiration. It can be performed at bedside, but research into sound patterns is ongoing and technique reliability is unclear.

Lateral cervical soft tissue radiographs have been used after swallowing contrast,⁵³ but poor head posture causes problems, and reporting is difficult for the inexperienced. Ultrasonography is safe and moderately portable, but most ultrasound probes are too small to visualize the whole swallow⁵⁴ and are limited to nonbony areas.

Pharyngeal or esophageal manometry can provide useful information, particularly when combined with VF,⁵⁵ and other methods tried include scintigraphy⁵⁶ and electromyography.⁵⁷ These techniques cannot be used at bedside, are invasive, and require specialized staff and equipment, so they have principally remained research tools.