A framework for understanding shared substrates of airway protection

Validation of the Choking Risk Assessment and Pneumonia Risk Assessment for adults with Intellectual and Developmental Disability (IDD)

BACKGROUND

Risk assessments are needed to identify adults with intellectual and developmental disability (IDD) at high risk of choking and pneumonia.

AIM

To describe the development and validation of the Choking Risk Assessment (CRA) and the Pneumonia Risk Assessment (PRA) for adults with IDD.

METHODS

Test items were identified through literature review and focus groups. Five-year retrospective chart reviews identified a positive choking group (PCG), a negative choking group (NCG), a positive pneumonia group (PPG), and a negative pneumonia group (NPG). Participants were tested with the CRA and PRA by clinicians blind to these testing conditions.

RESULTS

The CRA and PRA differentiated the PCG (n=93) from the NCG (n=526) and the PPG (n=63) from the NPG (n=209) with high specificity (0.91 and 0.92 respectively) and moderate to average sensitivity (0.53 and 0.62 respectively). Further analyses revealed associations between clinical diagnoses of dysphagia and choking (p=0.043), and pneumonia (p<0.001).

CONCLUSIONS

The CRA and PRA are reliable, valid risk indicators for choking and pneumonia in adults with IDD. Precautions for mitigating choking and pneumonia risks can be applied selectively thus avoiding undue impacts on quality of life and unnecessary interventions for low risk individuals.

Reduced Maximum Pitch Elevation Predicts Silent Aspiration of Small Liquid Volumes in Stroke Patients

Background and purpose

Preliminary evidence has shown that reduced ability to maximally raise vocal pitch correlates with the occurrence of aspiration (i.e., airway invasion by food or liquid). However, it is unclear if this simple task can be used as a reliable predictor of aspiration in stroke patients. Our aim was to examine whether maximum vocal pitch elevation predicted airway invasion and dysphagia in stroke.

Methods

Forty-five consecutive stroke patients (<1 month poststroke) at a rehabilitation setting participated in a videofluoroscopic swallow study and two maximum vocal pitch elevation tasks. Maximum pitch was evaluated acoustically [maximum fundamental frequency (max F₀)] and perceptually. Swallowing safety was rated using the Penetration/Aspiration Scale and swallowing performance was assessed using components of the Modified Barium Swallow Impairment Profile (MBSImPTM©). Data were analyzed using simple regression and receiver operating characteristics curves to test the sensitivity and specificity of max F₀ in predicting aspiration. Correlations between max F₀ and MBSImP variables were also examined.

Results

Max F₀ predicted silent aspiration of small liquid volumes with 80% sensitivity and 65% specificity (p = 0.023; area under the curve: 0.815; cutoff value of 359.03 Hz). Max F₀ did not predict non-silent aspiration or penetration in this sample and did not significantly correlate with MBSImP variables. Furthermore, all participants who aspirated silently on small liquid volumes (11% of sample) had suffered cortical or subcortical lesions.

Conclusion

In stroke patients (<1 month poststroke), reduced maximum pitch elevation predicts silent aspiration of small liquid volumes with high sensitivity and moderate specificity. Future large-scale studies focusing on further validating this finding and exploring the value of this simple and non-invasive tool as part of a dysphagia screening are warranted.

Expiratory muscle strength training for radiation-associated aspiration after head and neck cancer: A case series

OBJECTIVE/HYPOTHESIS

Expiratory muscle strength training (EMST) is a simple, inexpensive, device-driven exercise therapy. Therapeutic potential of EMST was examined among head and neck cancer survivors with chronic radiation-associated aspiration.

STUDY DESIGN

Retrospective case series.

METHODS

Maximum expiratory pressures (MEPs) were examined among n = 64 radiation-associated aspirators (per penetration-aspiration scale score ≥ 6 on modified barium swallow). Pre-post EMST outcomes were examined in a nested subgroup of patients (n = 26) who enrolled in 8 weeks of EMST (25 repetitions, 5 days/week, 75% load). Nonparametric analyses examined effects of EMST on the primary endpoint MEPs. Secondary measures included swallowing safety (Dynamic Imaging Grade of Swallowing Toxicity [DIGEST]), perceived dysphagia (M.D. Anderson Dysphagia Inventory [MDADI]), and diet (performance status scale for head and neck cancer patients [PSSHN]).

RESULTS

Compared to sex-matched published normative data, MEPs were reduced in 91% (58 of 64) of aspirators (mean ± standard deviation: 89 ± 37). Twenty-six patients enrolled in EMST and three patients withdrew. MEPs improved on average 57% (87 ± 29 to 137 ± 44 cm H₂ O, P < 0.001) among 23 who completed EMST. Swallowing safety (per DIGEST) improved significantly (P = 0.03). Composite MDADI scores improved post-EMST (pre-EMST: 59.9 ± 17.1, post-EMST: 62.7 ± 13.9, P = 0.13). PSSHN diet scores did not significantly change.

CONCLUSION

MEPs were reduced in chronic radiation-associated aspirators relative to normative data, suggesting that expiratory strengthening could be a novel therapeutic target to improve airway protection in this population. Similar to findings in neurogenic populations, these data also suggest improved expiratory pressure-generating capabilities after EMST and translation to functional improvements in swallowing safety in chronic radiation-associated aspirators.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:1044-1051, 2018.

Voluntary upregulation of reflex cough is possible in healthy older adults and Parkinson's disease

Cough is an airway-protective mechanism that serves to detect and forcefully eject aspirate material. Existing research has identified the ability of healthy young adults to suppress or modify cough motor output based on external cueing. However, no study has evaluated the ability of people with Parkinson's disease (PD) and healthy older adults (HOAs) to upregulate cough motor output. The goal of this study was to evaluate the ability of people with PD and healthy age-matched controls (HOAs) to upregulate reflex and voluntary cough function volitionally with verbal instruction and visual biofeedback of airflow targets. Sixteen participants with PD and twenty-eight HOAs (56-83 yr old) were recruited for this study. Experimental procedures used spirometry to evaluate 1) baseline reflex cough (evoked with capsaicin) and voluntary sequential cough and 2) reflex and voluntary cough with upregulation biofeedback. Cough airflow was recorded and repeated-measures ANOVA was used to analyze differences in cough airflow parameters. Cough peak expiratory airflow rate and cough expired volume were significantly greater in the cueing condition for both induced reflex (P < 0.001) and voluntary cough (P < 0.001) compared with baseline measures. This is the first study to demonstrate the ability of people with PD and HOAs to upregulate induced reflex and voluntary cough motor output volitionally. These results support the development of studies targeting improved cough effectiveness in patients with airway-protective deficits.NEW & NOTEWORTHY Aspiration pneumonia is a leading cause of death in Parkinson's disease (PD) and results from concurrent dysphagia and dystussia (cough dysfunction). This is the first study to demonstrate that people with PD and healthy age-matched controls can volitionally upregulate induced reflex and voluntary cough effectiveness when presented with novel cueing strategies. Thus targeting upregulation of cough effectiveness via biofeedback may be a viable way to enhance airway protection in people with PD.

Expiratory muscle strength training evaluated with simultaneous high-resolution manometry and electromyography

OBJECTIVE

To examine feasibility of a simultaneous high-resolution pharyngeal manometry (HRM) and electromyography (EMG) experimental paradigm to detect swallowing-related patterns of palatal, laryngeal, and pharyngeal muscle activity during expiratory training.

STUDY DESIGN

Technical report.

METHODS

Simultaneous HRM, surface submental, and intramuscular EMG were acquired in two healthy participants during five tasks: 10-cc water swallow, maximum expiratory pressure (MEP) testing, and expiratory muscle strength training (EMST) at three pressure levels (sham, 50%, and 75% MEP).

RESULTS

Experimental conditions were feasible. Velopharyngeal closing pressure, palate EMG activity, and pharyngeal EMG activity increased as expiratory load increased. In contrast, thyroarytenoid EMG activity was low during the expiratory task, consistent with glottic opening during exhalation. Submental EMG patterns were more variable during expiratory tasks. Intraluminal air pressures recorded with HRM were correlated with measured expiratory pressures and target valve-opening pressures of the EMST device.

CONCLUSION

Results suggest that a simultaneous HRM/EMG/EMST paradigm may be used to detect previously unquantified swallowing-related muscle activity during EMST, particularly in the palate and pharynx. Our approach and initial findings will be helpful to guide future hypothesis-driven studies and may enable investigators to evaluate other muscle groups active during these tasks. Defining mechanisms of action is a critical next step toward refining therapeutic algorithms using EMST and other targeted treatments for populations with dysphagia and airway disorders.

LEVEL OF EVIDENCE

4. Laryngoscope, 127:797-804, 2017.

Preliminary Evidence of Reduced Urge to Cough and Cough Response in Four Individuals following Remote Traumatic Brain Injury with Tracheostomy

Cough and swallow protect the lungs and are frequently impaired following traumatic brain injury (TBI). This project examined cough response to inhaled capsaicin solution challenge in a cohort of four young adults with a history of TBI within the preceding five years. All participants had a history of tracheostomy with subsequent decannulation and dysphagia after their injuries (resolved for all but one participant). Urge to cough (UTC) and cough response were measured and compared to an existing database of normative cough response data obtained from 32 healthy controls (HCs). Participants displayed decreased UTC and cough responses compared to HCs. It is unknown if these preliminary results manifest as a consequence of disrupted sensory (afferent) projections, an inability to perceive or discriminate cough stimuli, disrupted motor (efferent) response, peripheral weakness, or any combination of these factors. Future work should attempt to clarify if the observed phenomena are borne out in a larger sample of individuals with TBI, determine the relative contributions of central versus peripheral nervous system structures to cough sensory perceptual changes following TBI (should they exist), and formulate recommendations for systematic screening and assessment of cough sensory perception in order to facilitate rehabilitative efforts. This project is identified with the National Clinical Trials NCT02240329.

To Cough or Not to Cough? Examining the Potential Utility of Cough Testing in the Clinical Evaluation of Swallowing

PURPOSE

The clinical swallowing evaluation (CSE) represents a critical component of a comprehensive assessment of deglutition. Although universally utilized across clinical settings, the CSE demonstrates limitations in its ability to accurately identify all individuals with dysphagia. There exists a need to improve assessment and screening techniques to improve health outcomes, treatment recommendations and ultimately mortality in individuals at risk for dysphagia. The following narrative review provides a summary of currently used validated CSE's and examines the potential role of cough testing and screening in the CSE.

RECENT FINDINGS

Recent evidence highlights a relationship between objective physiologic measurements of both voluntarily and reflexively induced cough and swallowing safety status across several patient populations. Although more research is needed across a wider range of patient populations to validate these findings; emerging data supports the consideration of inclusion of cough testing during the CSE as an index of airway defense mechanisms and capabilities in individuals at risk for aspiration.

SUMMARY

The sensorimotor processes of cough and swallowing share common neuroanatomical and functional substrates. Inclusion of voluntarily or reflexively induced cough testing in the CSE may aide in the identification of dysphagia and reduced airway protection capabilities.

Tailored deep brain stimulation optimization for improved airway protective outcomes in Parkinson's disease

There is no consensus regarding the effects of deep brain stimulation (DBS) surgery on swallowing outcomes in Parkinson's disease (PD). No prospective studies have compared airway protective outcomes following DBS to the subthalamic nucleus (STN) versus globus pallidus interna (GPi). A recent retrospective study described swallowing outcomes pre- and post-STN vs. GPi DBS in a cohort of 34 patients with PD. The results revealed that the patients who received GPi DBS maintained their swallowing function post-DBS, while those in the STN group significantly worsened in swallowing safety. As DBS surgery becomes a common management option in PD it is important to understand the impact of DBS on airway protective outcomes; especially given that aspiration pneumonia is the leading cause of death in this population. We present a case report in which optimizing DBS settings with the goal of improving laryngeal function resulted in immediate improvements to swallowing safety.

A novel excitatory network for the control of breathing

Breathing must be tightly coordinated with other behaviours such as vocalization, swallowing, and coughing. These behaviours occur after inspiration, during a respiratory phase termed postinspiration. Failure to coordinate postinspiration with inspiration can result in aspiration pneumonia, the leading cause of death in Alzheimer's disease, Parkinson's disease, dementia, and other neurodegenerative diseases. Here we describe an excitatory network that generates the neuronal correlate of postinspiratory activity in mice. Glutamatergic-cholinergic neurons form the basis of this network, and GABA (γ-aminobutyric acid)-mediated inhibition establishes the timing and coordination relative to inspiration. We refer to this network as the postinspiratory complex (PiCo). The PiCo has autonomous rhythm-generating properties and is necessary and sufficient for postinspiratory activity in vivo.The PiCo also shows distinct responses to neuromodulators when compared to other excitatory brainstem networks. On the basis of the discovery of the PiCo, we propose that each of the three phases of breathing is generated by a distinct excitatory network: the pre-Bötzinger complex, which has been linked to inspiration; the PiCo, as described here for the neuronal control of postinspiration; and the lateral parafacial region (pF(L)), which has been associated with active expiration, a respiratory phase that is recruited during high metabolic demand.

Analysis of Clinicians' Perceptual Cough Evaluation

This study examined the relationships between subjective descriptors and objective airflow measures of cough. We hypothesized that coughs with specific airflow characteristics would share common subjective perceptual descriptions. Thirty clinicians (speech-language pathologists, otolaryngologists, and neurologists) perceptually evaluated ten cough audio samples with specific airflow characteristics determined by peak expiratory flow rate, cough expired volume, cough duration, and number of coughs in the cough epoch. Participants rated coughs by strength, duration, quality, quantity, and overall potential effectiveness for airway protection. Perception of cough strength and effectiveness was determined by the combination of presence of pre-expulsive compression phase, short peak expiratory airflow rate rise time, high peak expiratory flow rates, and high cough volume acceleration. Perception of cough abnormality was defined predominantly by descriptors of breathiness and strain. Breathiness was characteristic for coughs with either absent compression phases and relatively high expiratory airflow rates or coughs with significantly low expired volumes and reduced peak flow rates. In contrast, excessive strain was associated with prolonged compression phases and low expiratory airflow rates or the absence of compression phase with high peak expiratory rates. The study participants reached greatest agreement in distinguishing between single and multiple coughs. Their assessment of cough strength and effectiveness was less consistent. Finally, the least agreement was shown in determining the quality categories. Modifications of cough airflow can influence perceptual cough evaluation outcomes. However, the inconsistency of cough ratings among our participants suggests that a uniform cough rating system is required.

Measurement of Voluntary Cough Production and Airway Protection in Parkinson Disease

OBJECTIVE

To examine relations between peak expiratory (cough) airflow rate and swallowing symptom severity in participants with Parkinson disease (PD).

DESIGN

Cross-sectional study.

SETTING

Outpatient radiology clinic at an acute care hospital.

PARTICIPANTS

Men and women with PD (N=68).

INTERVENTIONS

Participants were cued to cough into an analog peak flow meter then swallowed three 20-mL thin liquid barium boluses. Analyses were directed at detecting potential relations among disease severity, swallowing symptom severity, and peak expiratory (cough) airflow rate.

MAIN OUTCOME MEASURES

Peak expiratory (cough) airflow rate and swallow symptom severity.

RESULTS

Peak expiratory (cough) airflow rate varied significantly across swallowing severity classifications. Participants with more severe disease displayed a significant, linear decrease in peak expiratory (cough) airflow rate than those participants with earlier stage, less severe disease. Swallowing symptom severity varied significantly across groups when comparing participants with less severe PD with those with more severe PD. Participants with early stage PD demonstrated little to no swallowing symptoms and had the highest measures of peak expiratory (cough) airflow rate. In contrast, participants with the most severe swallowing symptoms also displayed the lowest measures of peak expiratory (cough) airflow rate.

CONCLUSIONS

Relations existed among PD severity, swallowing symptom severity, and peak expiratory (cough) airflow rate in participants with PD. Peak expiratory (cough) airflow rate may eventually stand as a noninvasive predictor of aspiration risk in those with PD, particularly those with later stage disease. Inclusion of peak expiratory (cough) airflow rates into existing clinical swallowing assessments may increase the sensitivity and predictive validity of these assessments.

Voluntary Cough Airflow Differentiates Safe Versus Unsafe Swallowing in Amyotrophic Lateral Sclerosis

Dysphagia and aspiration are prevalent in amyotrophic lateral sclerosis (ALS) and contribute to malnutrition, aspiration pneumonia, and death. Early detection of at risk individuals is critical to ensure maintenance of safe oral intake and optimal pulmonary function. We therefore aimed to determine the discriminant ability of voluntary cough airflow measures in detecting penetration/aspiration status in ALS patients. Seventy individuals with ALS (El-Escorial criteria) completed voluntary cough spirometry testing and underwent a standardized videofluoroscopic swallowing evaluation (VFSE). A rater blinded to aspiration status derived six objective measures of voluntary cough airflow and evaluated airway safety using the penetration-aspiration scale (PAS). A between groups ANOVA (safe vs. unsafe swallowers) was conducted and sensitivity, specificity, area under the curve (AUC) and likelihood ratios were calculated. VFSE analysis revealed 24 penetrator/aspirators (PAS ≥3) and 46 non-penetrator/aspirators (PAS ≤2). Cough volume acceleration (CVA), peak expiratory flow rise time (PEFRT), and peak expiratory flow rate (PEFR) were significantly different between airway safety groups (p < 0.05) and demonstrated significant discriminant ability to detect the presence of penetration/aspiration with AUC values of: 0.85, 0.81, and 0.78, respectively. CVA <45.28 L/s/s, PEFR <3.97 L/s, and PEFRT >76 ms had sensitivities of 91.3, 82.6, and 73.9 %, respectively, and specificities of 82.2, 73.9, and 78.3 % for identifying ALS penetrator/aspirators. Voluntary cough airflow measures identified ALS patients at risk for penetration/aspiration and may be a valuable screening tool with high clinical utility.

Central nervous system integration of sensorimotor signals in oral and pharyngeal structures: oropharyngeal kinematics response to recurrent laryngeal nerve lesion

Safe, efficient liquid feeding in infant mammals requires the central coordination of oropharyngeal structures innervated by multiple cranial and spinal nerves. The importance of laryngeal sensation and central sensorimotor integration in this system is poorly understood. Recurrent laryngeal nerve lesion (RLN) results in increased aspiration, though the mechanism for this is unclear. This study aimed to determine the effect of unilateral RLN lesion on the motor coordination of infant liquid feeding. We hypothesized that 1) RLN lesion results in modified swallow kinematics, 2) postlesion oropharyngeal kinematics of unsafe swallows differ from those of safe swallows, and 3) nonswallowing phases of the feeding cycle show changed kinematics postlesion. We implanted radio opaque markers in infant pigs and filmed them pre- and postlesion with high-speed videofluoroscopy. Markers locations were digitized, and swallows were assessed for airway protection. RLN lesion resulted in modified kinematics of the tongue relative to the epiglottis in safe swallows. In lesioned animals, safe swallow kinematics differed from unsafe swallows. Unsafe swallow postlesion kinematics resembled prelesion safe swallows. The movement of the tongue was reduced in oral transport postlesion. Between different regions of the tongue, response to lesion was similar, and relative timing within the tongue was unchanged. RLN lesion has a pervasive effect on infant feeding kinematics, related to the efficiency of airway protection. The timing of tongue and hyolaryngeal kinematics in swallows is a crucial locus for swallow disruption. Laryngeal sensation is essential for the central coordination in feeding of oropharyngeal structures receiving motor inputs from different cranial nerves.

Respiratory kinematic and airflow differences between reflex and voluntary cough in healthy young adults

Background: Cough is a defensive behavior that can be initiated in response to a stimulus in the airway (reflexively), or on command (voluntarily). There is evidence to suggest that physiological differences exist between reflex and voluntary cough; however, the output (mechanistic and airflow) differences between the cough types are not fully understood. Therefore, the aims of this study were to determine the lung volume, respiratory kinematic, and airflow differences between reflex and voluntary cough in healthy young adults.

Methods: Twenty-five participants (14 female; 18–29 years) were recruited for this study. Participants were evaluated using respiratory inductance plethysmography calibrated with spirometry. Experimental procedures included: (1) respiratory calibration, (2) three voluntary sequential cough trials, and (3) three reflex cough trials induced with 200 μM capsaicin.

Results: Lung volume initiation (LVI; p = 0.003) and lung volume excursion (LVE; p < 0.001) were significantly greater for voluntary cough compared to reflex cough. The rib cage and abdomen significantly influenced LVI for voluntary cough (p < 0.001); however, only the rib cage significantly impacted LVI for reflex cough (p < 0.001). LVI significantly influenced peak expiratory flow rate (PEFR) for voluntary cough (p = 0.029), but not reflex cough (p = 0.610).

Discussion: Production of a reflex cough results in significant mechanistic and airflow differences compared to voluntary cough. These findings suggest that detection of a tussigenic stimulus modifies motor aspects of the reflex cough behavior. Further understanding of the differences between reflex and voluntary cough in older adults and in persons with dystussia (cough dysfunction) will be essential to facilitate the development of successful cough treatment paradigms.

Comparison of voluntary and reflex cough effectiveness in Parkinson's disease

INTRODUCTION

Multiple airway protective mechanisms are impacted with Parkinson's disease (PD), including swallowing and cough. Cough serves to eject material from the lower airways, and can be produced voluntarily (on command) and reflexively in response to aspirate material or other airway irritants. Voluntary cough effectiveness is reduced in PD however it is not known whether reflex cough is affected as well. The goal of this study was to compare the effectiveness between voluntary and reflex cough in patients with idiopathic PD.

METHODS

Twenty patients with idiopathic PD participated. Cough airflow data were recorded via facemask in line with a pneumotachograph. A side delivery port connected the nebulizer for delivery of capsaicin, which was used to induce cough. Three voluntary coughs and three reflex coughs were analyzed from each participant. A two-way repeated measures analysis of variance was used to compare voluntary versus reflex cough airflow parameters.

RESULTS

Significant differences were found for peak expiratory flow rate (PEFR) and cough expired volume (CEV) between voluntary and reflex cough. Specifically, both PEFR and CEV were reduced for reflex as compared to voluntary cough.

CONCLUSION

Cough PEFR and CEV are indicative of cough effectiveness in terms of the ability to remove material from the lower airways. Differences between these two cough types likely reflect differences in the coordination of the respiratory and laryngeal subsystems. Clinicians should be aware that evaluation of cough function using voluntary cough tasks overestimates the PEFR and CEV that would be achieved during reflex cough in patients with PD.