Cross-System Integration of Respiration and Deglutition: Function, Treatment, and Future Directions

The Respiratory-Swallow Coordination may be Related to Aspiration in Infratentorial Stroke Patients

To investigate the characteristics of respiratory-swallow coordination (RSC) in poststroke dysphagia (PSD) patients following infratentorial stroke (IS) and further explore their association with aspiration. PSD patients after IS and age-matched healthy controls were recruited. Nasal airflow and sound signals were recorded using a nasal cannula-type flow sensor and contact microphone, which were synchronized with videofluoroscopic swallowing studies (VFSS). For healthy controls, only nasal airflow and sound signals recordings were conducted. A 5 ml thickened liquid was utilized during these assessments. The penetration-aspiration scale (PAS) score was determined through VFSS. Various parameters, including swallowing apnoea duration (SAD), swallowing duration (SD), swallowing latency duration (SLD), number of swallows (NS), and RSC patterns, were analysed to assess RSC. A total of 37 patients with PSD following IS-comprising 25 non-aspirators and 12 aspirators-and 31 age-matched healthy controls were included. The PSD patient group exhibited a shorter SAD (p = 0.016), a longer SD (p = 0.000), and fewer NS (p = 0.000) compared to the healthy control group. Among the PSD patients, those who aspirated exhibited a notably shorter SAD (p = 0.018) and longer SD (p = 0.028) compared to non-aspirators. The prevalence of the swallow-inspiration pattern was higher in PSD patients (p = 0.006), particularly among those who aspirated (p = 0.010). Logistic regression analysis and the area under the receiver operating characteristic curve (AUC) indicated that both SAD (AUC = 0.825, p = 0.002) and SD (AUC = 0.757, p = 0.020) were significant predictors of aspiration. The optimal cut-off values for SAD and SD were determined to be 0.19s and 1.93s, respectively. The RSC characteristics in patients with PSD following IS differed from those observed in healthy controls, particularly among patients who experienced aspiration. In these patients, a shorter SAD and longer SD may contribute to an increased risk of aspiration.

The effects of noninvasive respiratory support on swallowing physiology, airway protection, and respiratory-swallow pattern in adults: A systematic review

PURPOSE

The use of noninvasive respiratory support- namely high flow of oxygen delivered via nasal cannula (HFNC), continuous positive airway pressure (CPAP), and noninvasive ventilation (NIV) - has been expanding in recent years. The physiologic mechanisms underlying each of these forms of support are generally well understood. In contrast, the effects on the sensorimotor mechanisms of swallowing movements, and of breathing and swallowing coordination ─ critical elements of airway protection and bolus clearance ─ remain unclear. The purpose of this systematic review is to assess the existing evidence about the impact of noninvasive respiratory support on swallowing mechanics, airway protection, and respiratory-swallowing patterns in adults.

METHODS

Six databases (PubMed, EMBASE, Web of Science, Scopus, CINAHL and ProQuest Dissertations & Theses) were searched using predetermined terms. Inclusion criteria were: 1) adult humans 2) use of noninvasive respiratory support, and 3) assessment of swallowing.

RESULTS

We identified 8727 articles for screening; 15 met the inclusion criteria. Six studies assessed noninvasive respiratory support in healthy adults, and 9 assessed participants with heterogenous respiratory diagnoses including chronic obstructive pulmonary disease (COPD), obstructive sleep apnea (OSA), acute respiratory failure, and chronic respiratory failure due to neuromuscular disease. Risk of bias was assessed using a modified NIH Quality Assessment Tool. In healthy adults, results demonstrated mixed effects of HFNC and CPAP on measures of swallowing function, airway protection, and respiratory swallowing patterns. Negative effects on respiratory-swallowing patterns were reported with NIV. In adults with heterogeneous respiratory diagnoses, six studies reported that HFNC, CPAP, or nasal NIV improved measures of swallowing and respiratory-swallowing patterns. HFNC has mixed effects on swallowing measures in ICU patients. NIV increased atypical respiratory-swallowing patterns in patients with stable COPD.

CONCLUSIONS

Due to small sample sizes and the wide variation in study designs, the impact of noninvasive respiratory support on swallowing, airway protection, and respiratory-swallowing patterns cannot be confidently assessed based on the current evidence. Future studies using standardized, validated, and reproducible methods to assess the impact of noninvasive respiratory support on swallowing physiology and airway protection are warranted.

Respiratory-swallow patterning and oropharyngeal swallowing impairment in patients undergoing evaluation for lung transplant

BACKGROUND

Although swallowing impairment is prevalent following lung transplantation, baseline respiratory and swallowing characteristics are often overlooked. Respiratory disease processes may predispose lung transplant candidates to altered respiratory-swallow patterning and swallowing impairment.

METHODS

This cross-sectional study included patients referred for a Modified Barium Swallow Study during lung transplant evaluation. Swallowing impairment was measured using the Modified Barium Swallow Impairment Profile and Penetration-Aspiration Scale. Respiratory plethysmographic signals synchronized with videofluoroscopy were analyzed to determine phase patterning, pause duration, and rate. Mixed-effects logistic regression was used to identify linkages between respiratory and swallowing measures.

KEY RESULTS

Fifty patients were included and demonstrated delayed swallow initiation (49/50), oral residue (37/50), incomplete pharyngoesophageal segment opening (35/50), and esophageal retention (43/50). Airway invasion occurred infrequently (10/50). Atypical respiratory patterning was significantly associated with impairment in pharyngeal swallow initiation (OR [95% CI] = 1.76 [1.16, 2.68], p = 0.009), laryngeal elevation (OR [95% CI] = 1.45 [1.01, 2.07], p = 0.044), and laryngeal vestibular closure (OR [95% CI] = 2.57 [1.48, 4.46], p < 0.001). Increased pause duration was associated with impaired initiation (OR [95% CI] = 2.24 [1.20, 4.16], p = 0.011), laryngeal elevation (OR [95% CI] = 1.18 [1.03, 1.36], p = 0.018), laryngeal closure (OR [95% CI] = 1.28 [1.9, 1.50], p = 0.003), and tongue base retraction (OR [95% CI] = 1.33 [1.13, 1.56], p < 0.001).

CONCLUSIONS & INFERENCES

Patients undergoing evaluation for lung transplant demonstrated impaired swallowing and phase patterning. Preliminary findings implicate the need for further evaluation of respiratory-swallow coordination and its potential role in swallowing impairment before and after lung transplantation.

Measurement of respiratory-swallowing coordination using an oronasal facemask in healthy individuals

Respiratory-swallowing coordination (RSC) is well established as an essential airway-protective mechanism. Previous studies have used nasal airflow and/or kinematic rib cage and abdominal measures to assess respiration surrounding swallowing, meaning that the direct influence of oral respiration on RSC remains unknown. This study used a partitioned oronasal facemask to compare respiratory phase patterns measured using isolated nasal airflow with those measured using combined oronasal airflow during non-ingestive and ingestive swallowing tasks. Twenty-four healthy individuals with no respiratory or swallowing disorders were assessed at rest and during cued dry, 10 mL water, continuous drinking and cracker swallowing tasks. Respiratory phase patterns were determined for discrete swallows using the nasal and combined oronasal channels separately. There was variable agreement between respiratory phase patterns according to the nasal and oronasal channels across swallowing conditions. The frequency of exhale-swallow-exhale, inhale-swallow-exhale and exhale-swallow-inhale patterns increased by 2%-3% each with the addition of oral flow data to nasal data, whereas the prevalence of inhale-swallow-inhale and ambiguous patterns decreased. This suggests that estimates of respiratory phase patterns are altered minimally by inclusion of oral respiratory estimates in a healthy sample. There were several additional findings of note, including lower within-participant, within-session trial consistency (test-retest reliability) than expected, suggesting high variability in respiratory phase patterns across trials. Additionally, data showed evidence of swallowing non-respiratory flow at the beginning and end of the respiratory-swallowing pause, moving in both inward and outward directions, potentially expanding current understanding of swallowing non-respiratory flow. Further in-depth physiological investigations are required to improve understanding of these findings.

Risk factors and impact of swallowing impairment and aspiration after lung transplantation

Background

Oropharyngeal swallowing impairment frequently occurs following lung transplantation, placing patients at risk of aspiration-related complications and mortality. The primary objectives of this study were to characterize swallowing impairment and explore potential risk factors for aspiration after lung transplantation.

Methods

A retrospective review of lung transplant recipients treated between January 2018 and December 2022 that received an instrumental swallow study was conducted. Clinical characteristics, post-operative outcomes, and results of swallow studies were evaluated. Airway invasion was classified using the Penetration-Aspiration Scale (PAS). Swallowing physiology was characterized using the Modified Barium Swallow Impairment Profile. Chi-squared, Wilcoxon signed-rank, Kaplan-Meier, Student's t-tests, and regression analyses were conducted.

Results

One hundred eighteen patients underwent lung transplantation and had an instrumental swallow study. Fifty-nine percent (70/118) demonstrated airway invasion. Delayed swallow initiation occurred in all patients that had videofluoroscopy (39/118). Body mass index (BMI) and body surface area (BSA) were significantly lower in patients with airway invasion (24.7±4.5 vs. 26.8±4.6 kg/m2, P=0.02; 1.8±0.2 vs. 1.9±0.2 m2, P=0.02, respectively), and were associated with airway invasion [odds ratio (OR): 0.91, P=0.02; OR: 0.13, P=0.02]. Intra- and post-operative outcomes and long-term survival did not differ significantly in our cohort.

Conclusions

Oropharyngeal swallowing impairment and airway invasion occurred with high frequency, and linkages to low BMI or frailty were found. Although the true prevalence of aspiration after lung transplantation might be underestimated by referral patterns in this cohort, the negative impact of aspiration after lung transplantation may be mitigated by appropriate recognition and intervention.

Effects of high-flow nasal therapy on swallowing function: a scoping review

Background

High-flow nasal therapy is widely used in patients with respiratory failure in different clinical settings, but the effect of high-flow nasal therapy on respiratory-swallow coordination is unknown. Understanding this relationship is crucial, considering the necessity for patients to maintain adequate nutrition during daytime high-flow nasal therapy. This scoping review aims to synthesise available data on the effects of high-flow nasal therapy flow rates on swallowing function and the possible risk of aspiration during treatment, focusing on knowledge and evidence gaps.

Methods

PubMed, Scopus, Web of Science and Google Scholar databases were searched from inception to 30 May 2023 for studies reporting data on swallowing assessment in healthy adults or patients with acute or chronic respiratory failure receiving high-flow nasal therapy. Data on study design, patients' characteristics and quality outcomes were extracted.

Results

Eight studies were included, four including cohorts of healthy volunteers (n=148) and four including patients with acute or chronic respiratory failure (n=151). Study designs, patient populations and quality outcome measures were heterogeneous. Two studies indicated improvement while four articles showed impairment in swallowing function during high-flow nasal therapy; two studies showed that patients' overall clinical picture and underlying medical conditions influenced swallowing-breathing coordination rather than high-flow nasal therapy per se.

Conclusion

This scoping review found limited and controversial evidence on the impact of high-flow nasal therapy on swallowing function. Remarkably, methods for swallowing function assessment were quite heterogeneous. Additional research is required to test the effect of high-flow nasal therapy on respiratory-swallowing coordination.

Assessing the oral and suprahyoid muscles in healthy adults using muscle ultrasound to inform the swallowing process: a proof-of-concept study

The oral and suprahyoid muscles are responsible for movements of swallowing. Our study aimed to determine the reproducibility of static and dynamic measurements of these muscles using bedside ultrasound equipment. Forty healthy participants were recruited prospectively. Primary outcomes were evaluation of mass measurements of the anterior bellies of the digastric, mylohyoid, geniohyoid and tongue in B-mode ultrasound. Secondary outcomes were evaluation of geniohyoid muscle layer thickness and function using M-mode. Muscle mass measurements demonstrated little within-participant variability. Coefficient of Variance (CoV) across muscles were: anterior belly digastric (5.0%), mylohyoid (8.7%), geniohyoid (5.0%) and tongue (3.2%). A relationship between sex (r2 = 0.131 p = 0.022) was demonstrated for the geniohyoid muscle, with males having higher transverse Cross Sectional Area (CSA) (14.3 ± 3.6 mm vs. 11.9 ± 2.5 mm, p = 0.002). Tongue size was correlated with weight (r2 = 0.356, p = 0.001), height (r2 = 0.156, p = 0.012) and sex (r2 = 0.196, p = 0.004). Resting thickness of the geniohyoid muscle layer changed with increasing bolus sizes (f = 3.898, p = 0.026). Velocity increased with bolus size (p =  < 0.001, F = 8.974). However swallow time and slope distance did not, potentially influenced by higher coefficients of variation. Oral and suprahyoid muscle mass are easily assessed using bedside ultrasound. Ultrasound may provide new information about muscle mass and function during swallowing.

Study on predictive models for swallowing risk in patients with AECOPD

BACKGROUND

Dysphagia is considered a complication in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). However, AECOPD may have risk factors for dysphagia.

METHODS

Through a cross-sectional study, which included 100 patients with AECOPD. General information, Pulmonary function, COPD assessment test (CAT) and modified Medical Research Council (mMRC) were collected by questionnaire. The questionnaires were administered by uniform-trained investigators using standard and neutral language, and swallowing risk was assessed by using a water swallow test (WST) on the day of patient admission.

RESULTS

Among the 100 included patients, 50(50%) were at risk of swallowing. Multivariate analysis using logistic regression analysis showed that age ≥ 74 years old, mMRC ≥ level 2, hospitalization days ≥ 7 days and the use of BIPAP assisted ventilation were important influencing factors for swallowing risk in patients with AECOPD.

CONCLUSION

Patients with AECOPD are at risk for dysphagia, assessing age, mMRC, hospitalization days and the use of BIPAP assisted ventilation can be used to screen for swallowing risk, thus contributing to the implementation of early prevention measures.

Characterizing Swallowing Impairment in a Post-Lung Transplant Population

BACKGROUND

Lung transplant recipients carry significant pre- and post-lung transplant dysphagia risk factors related to altered respiratory-swallow coordination as well as acute injury and decompensation resulting in the acute post-lung transplant recovery period. However, we are only beginning to understand the potential physiological contributors to altered swallowing in this population.

METHOD

A retrospective, cross-sectional, cohort study of post-lung transplant patients was performed. All participants received a modified barium swallow study (MBSS) as part of standard care during their acute hospitalization using the Modified Barium Swallow Impairment Profile (MBSImP) protocol and scoring metric. A combination of MBSImP scores, Penetration-Aspiration Scale (PAS) scores, Functional Oral Intake Scale (FOIS) scores, International Dysphagia Diet Standardization Initiative (IDDSI) scale levels, and the time from lung transplant to MBSS was collected, as well as measures of swallowing impairment and swallowing-related outcomes. Differences in swallowing physiology and swallowing-related outcomes between participants with typical versus atypical PAS were explored.

RESULTS

Forty-two participants met our prespecified inclusion criteria. We identified atypical laryngeal penetration and/or aspiration in 52.4% of our post-lung transplant cohort. Silent aspiration occurred in 75% of those patients who aspirated. Comparing typical versus atypical PAS scores, we found statistically significant associations with laryngeal elevation (Component 8), p < .0001; anterior hyoid excursion (Component 9), p = .0046; epiglottic movement (Component 10), p = .0031; laryngeal vestibule closure (Component 11), p < .0001; pharyngeal stripping (Component 12), p = .0058; pharyngeal total scores, p = .0001; FOIS scores, p = .00264; and IDDSI liquid levels, p = .0009.

CONCLUSIONS

Swallowing impairment resulting in abnormal bolus invasion is prevalent in post-lung transplant patients. Airway invasion in this cohort was related to pharyngeal swallow impairment and resulted in modified oral intake. Our findings help expand upon prior literature, which only reported the incidence of aspiration and pathological laryngeal penetration. Our results suggest that the potential for aerodigestive system impairment and negative sequela should not be underestimated in the post-lung transplant population.

Respiratory-Swallow Coordination in Individuals with Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Swallowing impairment, including altered physiology and aspiration, occur across the progression of Parkinson's disease (PD). The phase of respiration during which a swallow is initiated has been linked to swallowing impairment and aspiration in cohorts with dysphagia following stroke and head and neck cancer treatment, but has been understudied in PD. If similar findings are shown in individuals with PD, the implications for swallowing assessment and treatment are significant.

OBJECTIVE

The aim of this systematic review and meta-analysis of literature was to examine respiratory-swallow coordination measures and potential implications on swallowing physiology in individuals with PD.

METHODS

An extensive search of 7 databases (PubMed, EMBASE, Central, Web of Science, ProQuest Dissertations & Theses, Scopus, and CINAHL) with predetermined search terms was conducted. Inclusion criteria were individuals with PD and the use of objective evaluations of respiratory-swallow coordination.

RESULTS

Of the 13,760 articles identified, 11 met the inclusion criteria. This review supports the presence of atypical respiratory swallow patterning, respiratory pause duration and lung volume at swallow initiation in individuals with PD. The meta-analysis estimated an occurrence of 60% of non-expiration-expiration and 40% of expiration-expiration respiratory phase patterns surrounding swallowing.

CONCLUSION

Although this systematic review supports the occurrence of atypical respiratory-swallow coordination in individuals with PD, the evidence is limited by the variability in the methods of data acquisition, analysis, and reporting. Future research examining the impact of respiratory swallow coordination on swallowing impairment and airway protection using consistent, comparable, and reproducible methods and metrics in individuals with PD is warranted.