Effects of cadmium chloride inhalation on airflow limitation to histamine, carbachol and adenosine 5'-monophosphate assessed by barometric whole body plethysmography in healthy dogs

Evaluation of barometric whole-body plethysmography for therapy monitoring in cats with feline lower airway disease

OBJECTIVES

Feline lower airway disease (FLAD) is a common respiratory condition in cats. Traditionally, response to therapy is monitored only by evaluation of clinical signs and radiographic examination of the lungs. Barometric whole-body plethysmography (BWBP) is considered a non-invasive, well-tolerated form of measuring airway reactivity in cats. The aim of the study was to assess pulmonary function testing by BWBP for non-invasive evaluation of response to therapy in cats with FLAD and to investigate whether BWBP parameters correlate with clinical severity.

MATERIAL AND METHODS

The prospective study included 25 client-owned cats, diagnosed with FLAD on the basis of their medical history, clinical signs, radiographic findings, and bronchoalveolar lavage fluid (BALF) examination. At three time points (day 0, 14, and 60), a standardised owner questionnaire, a clinical examination and BWBP measurements were carried out. Results of the questionnaire and the clinical examination were evaluated using a clinical 12-point score. Individual therapy was administered to all patients after diagnosis, based on the severity of disease and compliance of the cat.

RESULTS

The total clinical score significantly improved over the entire study period (p<0.001). Significant improvement was detected for the frequency of coughing (p = 0.009), respiratory distress (p = 0.001), lung auscultation findings (p = 0.002), and general condition and appetite (p = 0.045). The BWBP parameter Penh, an indicator of bronchoconstriction, improved significantly under initial therapy between day 0 and 14 (p = 0.009). A significant correlation between Penh and the severity of auscultation findings was seen on day 0 (r = 0.40; p = 0.013).

CONCLUSION

The study supports the role of Penh as a non-invasive parameter for monitoring initial treatment response in cats with FLAD. Further studies are needed to address whether other BWBP parameters might be suitable for non-invasive therapy monitoring of FLAD. Clinical evaluation is always essential in cats with FLAD to evaluate treatment response.

[Pulmonary function testing in the cat - an overview]

This article provides an overview of currently available pulmonary function tests in cats, divided into invasive and non-invasive methods. Invasive techniques comprise arterial blood gas analysis and measurement of pulmonary mechanics. Non-invasive techniques include pulse oximetry and capnography, as well as methods not yet integrated into everyday practice such as tidal breathing airflow-volume loops, whole-body barometric plethysmography and thorax compression. In this article, the background, execution, interpretation, and limitations of each test are discussed. Proper performance and assessment of pulmonary function measurements may aid in understanding the pathophysiology of feline respiratory disease and in increasing objectivity when assessing the existing disease and treatment efficacy.

Structure-Activity Relationship Analysis of Psychedelics in a Rat Model of Asthma Reveals the Anti-Inflammatory Pharmacophore

Psychedelic drugs can exert potent anti-inflammatory effects. However, anti-inflammatory effects do not appear to correlate with behavioral activity, suggesting different underlying mechanisms. We hypothesized that the distinct structural features of psychedelics underlie functionally selective mechanisms at the target 5-HT2A receptor to elicit maximal anti-inflammatory effects. In order to test this hypothesis, we developed a new rat-based screening platform for allergic asthma. Next, we investigated 21 agonists at the 5-HT2A receptor from the three primary chemotypes (phenylalkylamine, ergoline, and tryptamine) for their ability to prevent airways hyperresponsiveness as a measure of pulmonary inflammation. Furthermore, we assessed each drug for in vitro activation of the canonical signaling pathway, calcium mobilization, from the 5-HT2A receptor. We find that the drug 2,5-dimethoxyphenethylamine (2C-H) represents the pharmacophore for anti-inflammatory activity and identify structural modifications that are either permissive or detrimental to anti-inflammatory activity. Additionally, there is no correlation between the ability of a particular psychedelic to activate intracellular calcium mobilization and to prevent the symptoms of asthma or with behavioral potencies. Our results support the notions that specific structural features mediate functional selectivity underlying anti-inflammatory activity and that relevant receptor activated pathways necessary for anti-inflammatory activity are different from canonical signaling pathways. Our results inform on the nature of interactions between ligands at the 5-HT2A receptor as they relate to anti-inflammatory activity and are crucial for the development of new 5-HT2A receptor agonists for anti-inflammatory therapeutics in the clinic that may be devoid of behavioral activity.

Whole-Body Barometric Plethysmography Characterizes Upper Airway Obstruction in 3 Brachycephalic Breeds of Dogs

BACKGROUND

A novel test using whole-body barometric plethysmography (WBBP) was developed recently to diagnose brachycephalic obstructive airway syndrome (BOAS) in unsedated French bulldogs.

HYPOTHESIS/OBJECTIVES

The hypotheses of this study were: (1) respiratory characteristics are different between healthy nonbrachycephalic dogs and brachycephalic dogs; and among pugs, French bulldogs, and bulldogs; and (2) obesity and stenotic nares are risk factors for BOAS. The main objective was to establish a diagnostic test for BOAS in these 3 breeds.

ANIMALS

A total of 266 brachycephalic dogs (100 pugs, 100 French bulldogs, and 66 bulldogs) and 28 nonbrachycephalic dogs.

METHODS

Prospective study. Exercise tolerance tests with respiratory functional grading, and WBBP were performed on all dogs. Data from WBBP were associated with functional grades to train quadratic discriminant analysis tools to assign dogs to BOAS+ and BOAS- groups. A BOAS index (0-100%) was calculated for each dog. Receiver operating characteristic (ROC) curves were used to evaluate classification ability.

RESULTS

Minute volume was decreased significantly in asymptomatic pugs (P = .009), French bulldogs (P = .026), and bulldogs (P < .0001) when compared to nonbrachycephalic controls. Respiratory characteristics were different among breeds and affected dogs had a significant increase in trace variation. The BOAS index predicted BOAS status for each breed with 94-97% (95% confidence interval [CI], 88.9-100%) accuracy (area under the ROC curve). Both obesity (P = .04) and stenotic nares (P = .004) were significantly associated with BOAS.

CONCLUSIONS AND CLINICAL IMPORTANCE

The WBBP can be used as a clinical tool to diagnose BOAS noninvasively and objectively.

Characterisation of Brachycephalic Obstructive Airway Syndrome in French Bulldogs Using Whole-Body Barometric Plethysmography

Brachycephalic obstructive airway syndrome (BOAS) is an important health and welfare problem in several popular dog breeds. Whole-body barometric plethysmography (WBBP) is a non-invasive method that allows safe and repeated quantitative measurements of respiratory cycles on unsedated dogs. Here respiratory flow traces in French bulldogs from the pet population were characterised using WBBP, and a computational application was developed to recognise affected animals. Eighty-nine French bulldogs and twenty non-brachycephalic controls underwent WBBP testing. A respiratory functional grading system was used on each dog based on respiratory signs (i.e. respiratory noise, effort, etc.) before and after exercise. For development of an objective BOAS classifier, functional Grades 0 and I were considered to have insignificant clinical signs (termed here BOAS-) and Grades II and III to have significant signs (termed here BOAS+). A comparison between owner-perception of BOAS and functional grading revealed that 60 % of owners failed to recognise BOAS in dogs that graded BOAS+ in this study.WBBP flow traces were found to be significantly different between non-brachycephalic controls and Grade 0 French bulldogs; BOAS- and BOAS+ French bulldogs. A classifier was developed using quadratic discriminant analysis of the respiratory parameters to distinguish BOAS- and BOAS + French bulldogs, and a BOAS Index was calculated for each dog. A cut-off value of the BOAS Index was selected based on a receiver operating characteristic (ROC) curve. Sensitivity, specificity, positive predictive value, and negative predictive value of the classifier on the training group (n=69) were 0.97, 0.93, 0.95, and 0.97, respectively. The classifier was validated using a test group of French bulldogs (n=20) with an accuracy of 0.95. WBBP offers objective screening for the diagnosis of BOAS in French Bulldogs. The technique may be applied to other brachycephalic breeds affected by BOAS, and possibly to other respiratory disease in dogs.

Analysis of tidal breathing flow volume loop in dogs with tracheal masses

OBJECTIVES

To investigate whether there are any changes in the tidal breathing flow volume loop (TBFVL) in calm, non-dyspnoeic dogs with intratracheal masses.

METHODS

We compared 4 dogs with intratracheal masses (group 1) with 10 healthy dogs (group 2). Routine clinical and laboratory examinations of the dogs were unremarkable, except for episodic upper respiratory obstructive signs in the dogs in group 1. Lateral radiography of the neck and thorax showed that group 1 dogs had masses that appeared to protrude into the tracheal lumen. Tracheoscopy and surgery or necropsy was performed to confirm the presence of the mass. Arterial blood gas and TBFVL analysis was carried out in all dogs to assess respiratory status.

RESULTS

The shape of the TBFVL for dogs in group 1 was narrower and ovoid compared with that for the group 2 dogs. Tidal volume and expiratory and inspiratory times were significantly reduced, whereas the respiratory rate was increased for dogs in group 1 compared with dogs in group 2. Arterial blood gas analysis was unremarkable for all dogs.

CONCLUSIONS

TBFVL is a non-invasive technique that is easy to perform and well tolerated by dogs. In the absence of abnormalities detected by routine diagnostic evaluations and arterial blood gas analysis in dogs with intratracheal masses, the TBFVL contributes to the definition of the physiologic status of the airways at the time of testing, and results suggests that these dogs breathe quite normally when they are calm and non-dyspnoeic.

Airway hyperresponsiveness to adenosine 5'-monophosphate in feline chronic inflammatory lower airway disease

Airway hyperresponsiveness is a key feature of human asthma and chronic bronchitis and response to the indirectly acting agonist adenosine 5'-monophosphate (AMP) is thought to reflect underlying airway inflammation. To examine whether airway responsiveness testing (ART) with AMP may be used to differentiate healthy cats from those with asthma (FA) and chronic bronchitis (CB), 24 cats (9 FA, 6 CB, 9 controls) underwent ART with AMP at concentrations of 0.1, 1, 10, 100 and 500mg/mL using barometric whole body plethysmography. The defined endpoint of ART, an increase in enhanced pause (Penh) exceeding 300% of the post-saline value (baseline), was reached in 9/15 patients (7 FA, 2 CB), but in none of the controls. Mean Penh (±SD) at baseline (BL) was 0.49±0.16 for cases, and 0.54±0.16 for controls, and was significantly increased after AMP challenge in clinical cases (2.62±2.20), but not in controls (0.63±0.30, P<0.05). After separating responder (R) and non-responder (NR) cases, a more pronounced difference after challenge was found (R: 3.96±1.84, NR: 0.6±0.21, P<0.001). The provocative concentration of the agonist that increased Penh to 300% of BL (PC Penh 300) in R cases was 52.98±48.04mg/mL AMP. Age had no influence on the responder status or PC Penh 300. It was concluded that AMP challenge may offer a new method for the identification of cats with lower inflammatory airway disease, and possibly for monitoring disease progression or response to therapy.

Description of original endoscopic findings and respiratory functional assessment using barometric whole-body plethysmography in dogs suffering from brachycephalic airway obstruction syndrome

The clinical features of brachycephalic airway obstructive disease in 11 brachycephalic dogs are described in this study. The respiratory strategy was assessed before (n=11) and after (n=6) surgery using barometric whole-body plethysmography (BWBP), with the relationship between BWBP variables and the severity of the clinical signs assessed by the use of a respiratory score based on clinical, radiographic and endoscopic findings. Partial collapse of the left main bronchus was a common finding not previously described as part of the brachycephalic airway obstructive disease syndrome. Epiglottic cysts, laryngeal granulomas and nasopharyngeal turbinates in English Bulldogs were other previously unreported findings. No significant correlation between the respiratory score and any of the BWBP variables was detected. Compared to healthy dogs, brachycephalic dogs had a significantly lower Te/Ti ratio (expiratory time over inspiratory time), peak inspiratory flow (PIF) per kg bodyweight (BW), significantly higher peak expiratory flow (PEF) per kgBW, PEF/PIF, and enhanced pause. These variations are compatible with upper airway obstructions primarily in the extrathoracic airways. Following surgery, a significant decrease in PEF/PIF was detected. The study showed that BWBP could be used to characterise the respiratory strategy in brachycephalic dogs before and after surgery.

Comparison of barometric whole body plethysmography and its derived parameter enhanced pause (PENH) with conventional respiratory mechanics in healthy Beagle dogs

The purpose of the study was to compare barometric whole body plethysmography (BWBP) and its derived parameter, enhanced pause (PENH), with conventional respiratory mechanics measurements. Resistance (RL), dynamic compliance (Cdyn) and pleural pressure changes were measured in six healthy anaesthetised Beagle dogs using a pneumotachograph and oesophageal balloon technique consecutive to BWBP-derived variables. Upper airway airflow limitation was established (1) by a filter or (2) by insertion of a narrow endotracheal tube. Bronchoconstriction was induced by nebulisation of carbachol at increasing concentrations until PENH exceeded 300% baseline. Upper airway narrowing significantly increased resistance (baseline RL 2.0+/-0.3, RL filter 11.8+/-3.2, RL luminal narrowing 21.1+/-2.3cm H(2)O/L/s; P <0.03), whereas PENH did not change significantly (baseline PENH 0.55+/-0.17, PENH filter 0.49+/-0.10; PENH luminal narrowing 0.50+/-0.18; P >0.05). Carbachol-induced bronchoconstriction caused a significant increase in PENH (baseline PENH 0.43+/-0.14, PENH carbachol 2.62+/-2.14; P <0.02) and resistance (baseline RL 2.1+/-0.3, RL carbachol 28.8+/-13.0 cm H2O/L/s; P <0.01), and a pronounced drop in compliance (baseline Cdyn 163.3+/-73.9, Cdyn carbachol 9.7+/-2.9mL/cmH2O; P <0.02). It was concluded that BWBP detects airflow limitation due to bronchoconstriction but not due to upper airway obstruction in healthy dogs. BWBP represents a valid, although not very sensitive screening tool for respiratory function testing.

Characterisation of the acute and reversible airway inflammation induced by cadmium chloride inhalation in healthy dogs and evaluation of the effects of salbutamol and prednisolone

The aims of this study were firstly to characterise a model of subclinical and reversible bronchial inflammation induced by cadmium chloride inhalation in healthy dogs and then to examine the effect of prednisolone or salbutamol treatment on the resulting bronchitis. The model characterisation and the effects of treatment were studied using clinical symptoms, haematology, thoracic radiography, bronchoscopy and bronchoalveolar lavage, barometric whole-body plethysmography and histamine broncho-provocation tests. In addition, the activity of matrix metalloproteinases (MMP)-2 and -9 were determined in serum and bronchoalveolar lavage fluid (BALF). Cadmium inhalation induced: (1) a transient bronchial inflammation, dominated by neutrophils; (2) a neutrophilia of the blood that persisted for up to 4 weeks; (3) a transient increased bronchial reactivity, and (4) a significant increase in MMP-9 activity in the BALF. Prednisolone treatment reduced the influx of inflammatory cells into the BALF, but not significantly, had no effect on pulmonary function, and did not reduce of airway hypersensitivity. Salbutamol had almost no effect on any of the parameters investigated.

Adenosine receptor modulation: potential implications in veterinary medicine

Adenosine is a purine nucleoside whose concentration increases during inflammation and hypoxia and the many roles of this molecule are becoming better understood. Increased reactivity to adenosine of the airways of asthmatic but not of normal subjects underlines the role of adenosine in airway inflammation. The identification and pharmacological characterisation of different adenosine receptors have stimulated the search for subtype-specific ligands able to modulate the effects of this molecule in a directed way. Several compounds of different chemical classes have been identified as having potential drawbacks, including side effects resulting from the broad distribution of the receptors across the organism, have prevented clinical application. In this article, the effects of adenosine's different receptors and the intracellular signalling pathways are reviewed. The potential of adenosine receptor modulation as a therapeutic target for chronic airway inflammation is considered, taking equine recurrent airway disease and feline asthma as examples of naturally occurring airway obstructive diseases. Other potential applications for adenosine receptor modulation are also discussed. As the intrinsic molecular events of adenosine's mechanism of action become uncovered, new concrete therapeutic approaches will become available for the treatment of various conditions in veterinary medicine.