Objectives/hypothesis

Contrast agent (CA) aspiration is an established complication of upper gastrointestinal and videofluoroscopic swallow studies. The underlying molecular biological mechanisms of acute response to CA aspiration in the respiratory organs remain unclear. The aims of this study were to elucidate the histological and biological influences of three kinds of CAs on the lung and to clarify the differences in acute responses.

Study design

Animal model.

Methods

Eight-week-old male Sprague Dawley rats were divided into five groups (n = 6 in each group). Three groups underwent tracheal instillation of one of three different CAs: barium (Ba) sulfate, nonionic contrast agents (NICAs), and ionic contrast agents (ICAs). A control group was instilled with saline and a sham group was instilled with air. All animals were euthanized on day 2 after treatment and histological and gene analysis was performed.

Results

No animal died after CA or control/sham aspiration. Ba caused severe histopathologic changes and more prominent inflammatory cell infiltration in the lungs compared with the two other iodinated contrast agents. Increases in expressions of inflammatory cytokines (tumor necrosis factor [Tnf], interleukin-1β [Il1b], and interferon-γ [Ifng]) were observed in Ba aspiration rats, and upregulation of Il1b was seen in ICA aspiration rats. NICA did not cause obvious histologic changes or expressions of inflammatory cytokines and fibrosis-related genes in the lungs.

Conclusions

Ba caused significantly more acute lung inflammation in a rodent model than did ioinic and nonionic iodinated CAs. Nonionic contrast did not cause any discernible inflammatory response in the lungs, suggesting that it may be the safest contrast for videofluoroscopic swallow studies.

Level of evidence

NA Laryngoscope, 129:1533-1538, 2019.

Objectives

Contrast agents (CAs) are essential for upper gastrointestinal and videofluoroscopic swallow studies (VFSSs). Recently, we reported that small amounts of Ba aspiration caused severe acute lung inflammation in a rodent model. However, the underlying molecular biological mechanisms of chronic response to CA aspiration remain unclear. The aims of this study were to explore the underlying molecular biological mechanisms of the chronic response to three kinds of CA aspiration on the lung.

Study design

Animal model.

Methods

Eight-week-old male Sprague Dawley rats were divided into five groups (n = 6, each group). Three groups underwent tracheal instillation of one of three CAs: barium sulfate (Ba), ionic iodinated contrast agent (ICA), and nonionic iodinated contrast agent (NICA). A sham group was instilled with air and a control group was instilled with saline. All animals were euthanized 30 days after treatment and histological and gene analyses were performed.

Results

No animal died after CA or sham/control aspiration. Ba particles remained after 30 days and caused histopathologic changes and inflammatory cell infiltration. Iodinated ICA and NICA did not result in perceptible histologic change. Expression of Tnf, an inflammatory cytokine was increased in only Ba aspirated rats (P = .0076). Other inflammatory cytokines and fibrosis-related genes did not alter between groups.

Conclusion

Aspirated Ba particles did not clear from the lung within a month and caused mild chronic pulmonary inflammation. ICA and NICA did not cause any inflammatory responses in the lungs, suggesting that ICA and NICA may be safer CAs for VFSS than Ba.

Level of evidence

NA.

Introduction: Multiple system atrophy (MSA) has detrimental effects on swallowing function. The swallowing function of patients with MSA has not been systematically characterized and the underlying pathophysiological mechanisms of dysphagia remain poorly understood. Objectives: To investigate the characteristics of swallow function in MSA using high-resolution manofluorography (HRMF). Methods: We conducted a retrospective review of twenty-five MSA patients who underwent HRMF from 2016 to 2017. HRMF was utilized on patients with only oral diet (Functional Oral Intake Scale (FOIS) >3). Pharyngoesophageal and proximal esophageal pressure profiles were evaluated and compared to established normative data. The frequency and characteristics of upper esophageal sphincter (UES) and proximal esophageal abnormalities during rest and swallow were calculated. Results: The ages of patient cohort in our study ranged from 48-81 years (median 65 years) with male predominance (68%). We observed a distinct abnormal deglutitive proximal esophageal contraction (ADPEC) in 14 (56% of patients), which appears to reflect a discoordinated response of the striated muscle esophagus. Deficient UES relaxation duration, impaired UES relaxation, hypertensive resting UES pressure and hypotensive resting UES pressure were detected in 8 patients (32%), 3 patients (12%), 1 patient (4%), and 11 patients (44%) respectively. Conclusions: In patients with MSA, abnormal UES resting pressure is common. A discoordinated proximal esophageal pressure response was identified and may be a pathognomonic manometry finding for MSA. These findings may serve as indications of early stage swallowing dysfunction in patients with MSA.