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This review article seeks to define and describe aerodigestive disease in dogs, and review current and emerging methods of diagnostic evaluation. Aspiration of gastric contents into the respiratory tract is associated with the development and progression of numerous respiratory diseases in humans. In veterinary medicine the term “aspiration” is considered synonymous with “aspiration pneumonia” which, while frequently encountered, does not accurately reflect the breadth of aspiration associated respiratory syndromes (AARS). In the clinical veterinary literature, the effect of alimentary dysfunction on respiratory disease and vice versa (aerodigestive disease) is rarely investigated despite evidence in the human literature, animal models, and some studies and case reports linking alimentary and respiratory disease in small animals. Current methods of investigating aerodigestive diseases in veterinary patients are limited by inadeqate  sensitivity or specificity, potential for bias, cost, and availability. This necessitates investigations into advanced diagnostics to identify potentially underrecognized animals with AARS. Additionally, similarities in anatomy, physiology, and several disorders between dogs and humans, make experimental and naturally occurring canine models of AARS integral to translational research. Thus, evaluating dogs with aerodigestive disease might represent an area of substantial clinical relevance in human as well as veterinary medicine.

Advances in the field of metagenomics using culture-independent methods of microbial identification have allowed characterization of rich and diverse communities of bacteria in the lungs of healthy humans, mice, dogs, sheep and pigs. These data challenge the long held belief that the lungs are sterile and microbial colonization is synonymous with pathology. Studies in humans and animals demonstrate differences in the composition of airway microbiota in health versus disease suggesting respiratory dysbiosis occurs. Using 16S rRNA amplicon sequencing of DNA extracted from rectal and oropharyngeal (OP) swabs, bronchoalveolar lavage fluid (BALF), and blood, our objective was to characterize the fecal, OP, blood, and lower airway microbiota over time in healthy cats. This work in healthy cats, a species in which a respiratory microbiota has not yet been characterized, sets the stage for future studies in feline asthma in which cats serve as a comparative and translational model for humans. Fecal, OP and BALF samples were collected from six healthy research cats at day 0, week 2, and week 10; blood was collected at week 10. DNA was extracted, amplified via PCR, and sequenced using the Illumina MiSeq platform. Representative operational taxonomic units (OTUs) were identified and microbial richness and diversity were assessed. Principal component analysis (PCA) was used to visualize relatedness of samples and PERMANOVA was used to test for significant differences in microbial community composition. Fecal and OP swabs provided abundant DNA yielding a mean±SEM of 65,653±6,145 and 20,6323±4,360 sequences per sample, respectively while BALF and blood samples had lower coverage (1,489±430 and 269±18 sequences per sample, respectively). Oropharyngeal and fecal swabs were significantly richer than BALF (mean number OTUs 93, 88 and 36, respectively; p < 0.001) with no significant difference (p = 0.180) in richness between time points. PCA revealed site-specific microbial communities in the feces, and upper and lower airways. In comparison, blood had an apparent compositional similarity with BALF with regard to a few dominant taxa, but shared more OTUs with feces. Samples clustered more by time than by individual, with OP swabs having subjectively greater variation than other samples. In summary, healthy cats have a rich and distinct lower airway microbiome with dynamic bacterial populations. The microbiome is likely to be altered by factors such as age, environmental influences, and disease states. Further data are necessary to determine how the distinct feline microbiomes from the upper and lower airways, feces and blood are established and evolve. These data are relevant for comparisons between healthy cats and cats with respiratory disease.

The upper and lower airways of healthy humans are reported to harbor stable and consistent bacterial populations, and the composition of these communities is altered in individuals affected with several respiratory diseases. Data regarding the presence of airway microbiota in other animals are scant and a better understanding of the composition and metabolic function of such bacterial populations is essential for the development of novel therapeutic and diagnostic modalities for use in both veterinary and human medicine. Based on targeted next-generation sequencing of feces and samples collected at multiple levels of the airways from 16 healthy female dogs, we demonstrate that canine airways harbor a topographically continuous microbiota with increasing relative abundance of proteobacterial species from the upper to lower airways. The lung-associated microbiota, as assessed via bronchoalveolar lavage fluid (BALF), was the most consistent between dogs and was dominated by three distinct taxa, two of which were resolved to the species level and one to the level of family. The gene content of the nasal, oropharyngeal, and lung-associated microbiota, predicted using the Phylogenetic Investigations into Communities by Reconstruction of Unobserved States (PICRUSt) software, provided information regarding the glyoxylate and citrate cycle metabolic pathways utilized by these bacterial populations to colonize such nutrient-poor, low-throughput environments. These data generated in healthy subjects provide context for future analysis of diseased canine airways. Moreover, as dogs have similar respiratory anatomy, physiology, and immune systems as humans, are exposed to many of the same environmental stimuli, and spontaneously develop similar respiratory diseases, these data support the use of dogs as a model species for prospective studies of the airway microbiota, with findings translatable to the human condition.

Brachycephalic obstructive airway syndrome (BOAS) is associated with significant morbidity and mortality. Routine clinical evaluation fails to detect physiologic consequences of BOAS including airflow limitation, exercise intolerance, and impaired thermoregulation. A six-minute walk test (6MWT) with infrared thermography (IRT) may aid detection and clinical management by assessing the physiologic consequences of BOAS. IRT has been used in dogs to assess thermoregulation and in people with obstructive sleep apnea. Our objectives were to compare 6MWT and IRT parameters between healthy mesaticephalic (Mesa) and brachycephalic (Brachy) dogs, and dogs with BOAS. 6MWT parameters include normalized distance walked (ND), rectal temperature, pulse, respiratory rate, and pulse oximetry (SPO2). Mean (T mean ) and maximum (T max ) IRT temperatures at 3 regions of interest (ROI) were evaluated. Evaluation timepoints were pre-6MWT, immediately post-6MWT (T 0 ) and 5 (T 5 ) and 15min post-6MWT (T 15 ). No significant difference in ND, SPO2, or temperature were found between groups (p>.05). BOAS dogs had higher dorsal and rostral T max and T mean temperatures compared to Mesa dogs at all timepoints (p < .05). BOAS dogs had higher T mean temperatures compared to Brachy dogs at baseline and T 15 and T 5 and T 15 for dorsal and rostral ROIs respectively (p < .001). ROC analysis showed significant discrimination between BOAS and non-BOAS (Brachy and Mesa) dogs with areas under the curve between 0.79–0.96. Significant moderate correlations were found between IRT temperatures, ND and rectal temperature. This pilot study demonstrates the potential in pairing the 6MWT and IRT with evaluation of clinical signs as screening tool to identify dogs with BOAS.

Background Aerodigestive diseases (AeroD), hybrid disorders between the respiratory and gastrointestinal (GI) tracts, may present without GI signs. Sliding hiatal hernia (sHH) is an important AeroD in brachycephalic dogs linked to respiratory pathology. The spectrum of other AeroD and respiratory clinical signs (CS) in brachycephalic and nonbrachycephalic dogs with sHH is unknown. Objectives Characterize CS of AeroD in dogs with sHH, compare CS between brachycephalic and nonbrachycephalic dogs, and compare thoracic radiographs and videofluoroscopic swallow study (VFSS) for diagnosing sHH. Animals Sixty‐seven client‐owned dogs with sHH. Methods Medical records of dogs with sHH presented to the veterinary teaching hospitals at Auburn University and the University of Missouri between 1 January 2009 and 31 December 2020 were retrospectively reviewed. Between group, comparisons were made using Mann‐Whitney test, Chi‐square analysis, and Spearman correlation (P < .05). Results Dogs with sHH presented with exclusively GI signs (28/67), mixed respiratory and GI signs (22/67), or with exclusively respiratory signs (17/67). Wheras brachycephalic dogs were not significantly more likely to present with respiratory CS (P = .145), they were younger (P < .001), and more likely to present in respiratory distress (P = .02), and with radiographic evidence of aspiration pneumonia (P < .001) compared to nonbrachycephalic dogs. Six of 12 dogs with normal thoracic radiographs having sHH presented with respiratory CS. For detection of sHH, VFSS was superior to radiographs (P < .001). Conclusions and Clinical Importance Dogs with sHH may present with exclusively respiratory signs. Respiratory signs may be more severe in brachycephalic compared to nonbrachycephalic dogs. Videofluoroscopic swallow study was superior to thoracic radiographs for detection of sHH in dogs.

The lungs of people and companion animals are now recognized to harbor diverse, low biomass bacterial communities. While these communities are difficult to characterize using culture-based approaches, targeted molecular methods such as 16S rRNA amplicon sequencing can do so using DNA extracted from samples such as bronchoalveolar lavage fluid (BALF). Previous studies identified a surprisingly uniform composition of the microbiota in the lungs of healthy research dogs living in a controlled environment, however there are no reports of the lung microbiota of client-owned dogs. Moreover, compositional changes in the lung microbiota depending on disease status have been reported in people, suggesting that similar events may occur in dogs, a species subject to several respiratory disease mechanisms analogous to those seen in people. To address these knowledge gaps, BALF samples from client-owned dogs presenting to the University of Missouri Veterinary Health Center for respiratory signs between 2014 and 2017 were processed for and subjected to 16S rRNA sequencing. Based on specific diagnostic criteria, dogs were categorized as Chronic Bronchitis (CB, n = 53) or non-CB (n = 11). Community structure was compared between groups, as well as to historical data from healthy research dogs (n = 16) of a uniform breed and environment. The lung microbiota detected in all client-owned dogs was markedly different in composition from that previously detected in research dogs and contained increased relative abundance of multiple canine fecal and environmental bacteria, likely due to aspiration associated with their clinical signs. While inter-sample diversity differed significantly between samples from CB and non-CB dogs, the variability within both groups made it difficult to discern reproducible bacterial classifiers of disease. During subsequent analyses to identify other sources of variability within the data however, population-wide temporal dynamics in community structure were observed, with substantial changes occurring in late 2015 and again in early 2017. A review of regional climate data indicated that the first change occurred during a historically warm and wet period, suggesting that changes in environmental conditions may be associated with changes in the respiratory microbiota in the context of respiratory disease. As the lung microbiota in humans and other animals is believed to result from repetitive micro-aspirations during health and in certain disease states associated with dyspnea and laryngeal dysfunction, these data support the increased colonization of the lower airways during compromised airway function, and the potential for temporal effects due to putative factors such as climate.

Background Reflux and aspiration in people are associated with respiratory disease, whereas approximately 50% of healthy adults microaspirate without apparent consequence. In dogs, analogous information is lacking. Hypothesis Healthy dogs commonly have gastroesophageal reflux and a proportion of these dogs will have laryngopharyngeal reflux with silent aspiration. Animals Twelve healthy, client‐owned dogs. Methods Prospective study: Dogs were free‐fed a meal containing (111 MBq) colloidal 99m‐technetium phytate. Dynamic‐scans were performed 5 and 30 minutes postingestion. Time‐activity curves, reflux margination, volume, frequency, and duration were evaluated over 7 regions of interest in dorsal ± left‐lateral recumbency. Static scans (dorsal recumbency) were performed 2 and 18 hours postfeeding to detect aspiration. Reflux and aspiration were defined as counts ≥200% background activity ± decreased gastric counts. Between‐group comparisons were performed by Wilcoxon rank‐sum test or one‐way ANOVA on ranks with significance of P < .05. Results In this study, reflux of variable magnitude was detected in 12/12 dogs. No significant differences in outcome parameters were detected with recumbency (P > .05). Margination to the pharynx and proximal, middle, and distal esophagus was identified in 5/12, 2/12, 3/12, and 2/12 dogs, respectively. Median (IQR) reflux frequency and duration were 2 events/5 minutes (1‐3.3 events/5 minutes) and 6 seconds (4‐9 seconds) respectively. No dog had detectable aspiration. Conclusions and Clinical Importance Nuclear scintigraphy can document reflux in dogs. Reflux, but not aspiration, is common in healthy dogs and must be considered when interpreting results in clinically affected dogs.

Blood lactate and glucose are recognized as prognostic markers in various diseases in human and animals, yet studies evaluating their prognostic utility in canine and feline pyothorax are limited. This study aimed to investigate the prognostic utility of point-of-care (POC) lactate and glucose measurements, and identify clinical factors associated with survival in dogs and cats with pyothorax. A database search identified canine and feline pyothorax cases presenting to Auburn University between 2013 and 2023. Forty-three dogs and eight cats diagnosed with pyothorax were retrospectively enrolled. Baseline characteristics, clinicopathological data, and diagnostic findings were obtained from the medical records. POC blood glucose and lactate, recorded on admission and the following morning were documented, and lactate delta and clearance were calculated. Data on treatment was also collected. Additional outcome measures included survival and duration of hospitalization. In dogs, non-survivors had significantly higher POC lactate concentrations on admission compared to survivors (3.4 mmol/L vs. 2.0 mmol/L,  = 0.023). Band neutrophil count was associated with in-hospital mortality at a univariable level (  = 0.03, OR 1.4). Stepwise Cox regression showed total solids and lactate concentration on admission as independent predictors of outcome. The area under the curve (AUC; 95% CI) for predicting in-hospital mortality based on lactate was 0.724 (0.568-0.879). In dogs with pyothorax, admission POC blood lactate concentration may serve as valuable prognostic tool to guide clinical management decisions, and an increased band neutrophil count is associated with poorer outcomes. Further large-scale studies are needed to confirm these findings.

Background Videofluoroscopic swallow studies (VFSS) utilizing penetration‐aspiration (P‐A) scoring assesses airway protection in people. On VFSS, penetration (ingesta or secretions immediately cranial to the vocal folds) and aspiration (material caudal to the vocal folds) are associated with increased risk of lung injury in people. Penetration‐aspiration (P‐A) scoring has been validated in animal models, but the incidence of P‐A, clinical signs (CS), and dysphagic disorders associated with P‐A in dogs are unknown. Objectives Using VFSS, identify the incidence of P‐A, compare CS between dogs with and without P‐A, and identify predisposing dysphagic abnormalities for P‐A. Animals One hundred client‐owned dogs. Methods Sequential VFSS and associated medical records from dogs presenting to the veterinary teaching hospitals at Auburn University (n = 53) and the University of Missouri (n = 47) were retrospectively reviewed. Statistical comparisons were made using Mann‐Whitney tests, one‐way analysis of variance (ANOVA) on ranks, multiple linear regression, and Spearman rank order correlation (P < .05). Results On VFSS, the incidence of pathologic P‐A was 39%. No significant differences in CS were found between dogs with or without P‐A (P > .05), with 14/39 dogs with P‐A presenting without respiratory CS. Pharyngeal (P < .001) and esophageal (P = .009), but not oral‐preparatory (P = .2) dysphagia was more common with P‐A. Pharyngeal weakness (P < .001) and esophago‐oropharyngeal reflux (EOR; P = .05) were independent predictors of P‐A and were moderately and weakly positively correlated with P‐A score respectively (P < .001, r = 0.489; P = .04, r = 0.201). Conclusions Penetration‐aspiration occurs in dogs in the absence of respiratory CS (i.e., occult P‐A). Dogs with pharyngeal weakness and EOR should be considered at risk for P‐A.

Background Aerophagia (ingestion of air), is a functional aerodigestive disorder in people. Criteria for diagnosis of aerophagia in dogs are >1/3 of bolus volume containing air or ingested air resulting in gastric distention (>1/3 of end gastric volume). Aerophagia is highlighted during eating and drinking. Videofluoroscopic swallow studies (VFSS) document aerophagia in dogs, but the incidence, clinical signs (CS), and associated disorders are unknown. Objectives Identify the incidence of aerophagia, compare CS between dogs with and without aerophagia, and identify associated and predisposing disorders using VFSS. Animals A total of 120 client‐owned dogs. Methods Sequential VFSS and associated medical records from dogs presenting to veterinary teaching hospitals at Auburn University and the University of Missouri were retrospectively reviewed. Statistical comparisons were made using Mann‐Whitney and chi‐squared tests, odds ratios (OR), and multiple logistic regression (P < .05). Results The incidence (95% confidence interval [CI]) of aerophagia was 40% (31.7‐48.9). Dogs with mixed CS (gastrointestinal [GI] and respiratory; P < .001, 58.3%) were more likely to have aerophagia than dogs with exclusively respiratory CS (25%). Aerophagia was significantly more common in brachycephalic dogs (P = .01; 45.8% vs 13.8%), dogs with nonbrachycephalic upper airway obstruction (P < .001; 33.3% vs 4.1%), pathologic penetration and aspiration (P‐A) scores (P = .04; 41.6% vs 23.6%), and gagging (P < .001; 25% vs 11.7%). Mixed CS (P = .01), brachycephaly (P < .001), and upper airway obstruction (P < .001) were independent predictors of aerophagia. Conclusions and Clinical Importance Aerophagia was common, particularly in dogs with mixed CS. Brachycephalic dogs and dogs with upper airway obstruction are predisposed. Aspiration risk was high, emphasizing overlapping upper aerodigestive pathways.