Assessing breathing effort by barometric whole-body plethysmography and its relationship with prognosis in client-owned cats with respiratory distress

BACKGROUND

Cats in respiratory distress have limited tolerance for manipulation, hindering clinical monitoring. Minute volume (MV) can be utilized to rate dyspnea in humans, but its relationship with respiratory distress in cats remains poorly investigated.

HYPOTHESIS

Cats with respiratory distress will show higher MV per kg body weight (MV/BW) than normal cats, and the MV/BW increase will correlate with survival.

ANIMALS

Fifty-two cats with respiratory distress from lung parenchymal disease, pleural space disease, lower airway obstruction (LAO), or upper airway obstruction were recruited since 2014.

METHODS

This is a prospective observational study. Study cats were placed in a transparent chamber, allowing clinicians to easily observe their breathing status and record ventilation using barometric whole-body plethysmography (BWBP). Ventilatory variables of the 52 cats were compared with those of 14 historic control cats. Follow-up data, including disease category, clinical outcomes, and survival, were prospectively collected.

RESULTS

Cats in respiratory distress demonstrated significantly higher MV/BW (397 mL/kg; range, 158-1240) than normal cats (269 mL/kg; range, 168-389; P < .001). Among the etiologies, cats with LAO, parenchymal, and pleural space disease exhibited higher-than-normal MV/BW trends. A cutoff value of 373 mL/kg (1.4-fold increase) indicated abnormally increased breathing efforts (sensitivity, 67%; specificity, 93%). MV/BW was independently associated with increased cardiorespiratory mortality in cats with respiratory distress (adjusted hazard ratio 1.17, 95% confidence interval [CI] 1.02-1.35; P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

Breathing efforts in cats can be noninvasively quantified using BWBP. Measurement of MV/BW could serve as a prognostic index for monitoring cats experiencing respiratory distress.

Influence of acclimatization time on parameters of barometric whole-body plethysmography in healthy adult cats

BACKGROUND

Pulmonary function testing by barometric whole-body plethysmography (BWBP) is a long-established and well-accepted, non-invasive investigative procedure in cats.

HYPOTHESIS/OBJECTIVES

To evaluate, if different acclimatization times influence the measurement parameters of BWBP in healthy adult cats.

ANIMALS

48 healthy adult cats.

METHODS

In the prospective observational study, healthy cats were placed in a measuring chamber and BWBP was performed over 30 minutes. Parameters obtained during the three measurement units of 10 minutes each (T1, T2 and T3) were compared.

RESULTS

All measurement parameters except for tidal volume per body weight changed significantly (p<0.05) over the three time periods. From T1-T2, the parameters minute volume per body weight (p<0.001), peak inspiratory flow per body weight (p<0.001), peak expiratory flow per body weight (p = 0.002), pause (p = 0.03), enhanced pause (p = 0.03) and quotient of peak expiratory flow divided by expiratory flow at end expiratory volume plus 50% tidal volume (p = 0.03) changed significantly. From the time interval T2-T3, only respiratory rate (p = 0.02), inspiratory time (p = 0.02), expiratory time (p = 0.04), and relaxation time (p = 0.01) changed significantly. All measurement parameters except for tidal volume per body weight changed significantly (p<0.05) between T1 and T3. Age had a significant influence on all parameters except for peak expiratory flow per body weight and peak inspiratory flow per body weight. The parameters were not influenced by sex.

CONCLUSION AND CLINICAL IMPORTANCE

All measurement parameters except tidal volume per body weight were significantly affected by acclimatization time. Controlling for age and sex, there was still a significant influence of acclimatization time on all parameters except for tidal volume per body weight. Standardization of the acclimatization time for future studies would be appropriate in order to maintain comparability.

Correlation of clinical and radiographic variables in cats with lower airway disease

BACKGROUND

Feline lower airway disease (FLAD) is frequently associated with radiographic abnormalities.

OBJECTIVES

To evaluate whether radiographic changes in cats with naturally occurring FLAD improve with treatment and if radiographic changes correlate with clinical signs.

ANIMALS

Twenty-four client-owned cats newly diagnosed with FLAD, based on medical history, typical clinical signs, radiographic findings, and examination of bronchoalveolar lavage fluid, were included in the prospective study.

METHODS

At 2 examination time points (days 0 and 60), an owner questionnaire, clinical examination, and thoracic radiography were carried out. Information from the questionnaire and clinical examination were evaluated on the basis of a 12-point clinical score. Radiographs were assessed using a 10-point radiographic score. Individual treatment was given to all cats over the study period, based on severity of the disease and compliance of the cat. Clinical and radiographic scores were compared statistically for both examination time points and evaluated for correlation.

RESULTS

All cats showed radiographic abnormalities at initial presentation. In addition to significant improvement in clinical variables, the total radiographic score improved significantly (P = .01) during the study period, with significant improvement in the severity of bronchial (P = .01) and interstitial lung pattern (P = .04). Improvement of the clinical and radiographic score was not correlated.

CONCLUSION AND CLINICAL IMPORTANCE

In addition to clinical signs, repeated radiographic examination can be used as a diagnostic tool to evaluate treatment response in cats with FLAD.

[Evaluierung der Langzeittherapie bei Katzen mit felinem Asthma und chronischer Bronchitis]

GEGENSTAND UND ZIEL

Felines Asthma (FA) und chronische Bronchitis (CB) sind häufige entzündliche Erkrankungen der Atemwege der Katze. Obwohl beide Krankheitsbilder durch eine Infiltration mit unterschiedlichen Entzündungszelltypen gekennzeichnet sind, sind die therapeutischen Maßnahmen oft ähnlich. Über mögliche Unterschiede im therapeutischen Management dieser beiden Atemwegserkrankungen ist wenig bekannt. Ziel der Studie war es daher, bei Katzen mit FA und CB die Erst- und Langzeitbehandlung, Therapieerfolg, Nebenwirkungen und Besitzerzufriedenheit zu vergleichen.

MATERIAL UND METHODEN

35 Katzen mit FA und 11 Katzen mit CB wurden in die retrospektive Querschnittstudie eingeschlossen. Einschlusskriterien waren kompatible klinische und radiologische Befunde sowie der zytologische Nachweis einer eosinophilen Entzündung (FA) oder einer sterilen neutrophilen Entzündung (CB) in der bronchoalveolären Lavage-Flüssigkeit (BALF). Katzen mit CB wurden ausgeschlossen, wenn Hinweise auf pathologische Bakterien vorlagen. Besitzer wurden gebeten einen standardisierten Fragebogen zum therapeutischen Management und Ansprechen auf die Behandlung auszufüllen.

ERGEBNISSE

Im Gruppenvergleich wurden keine statistisch signifikanten Unterschiede der Therapie festgestellt. Die meisten Katzen wurden anfänglich mit Kortikosteroiden mittels einer oralen (FA 63%/CB 64%, p=1), inhalativen (FA 34%/CB 55%, p=0,296) oder injizierbaren Applikationsform (FA 20%/CB 0%, p=0,171) behandelt. Zusätzlich wurden in einigen Fällen orale Bronchodilatatoren (FA 43%/CB 45%, p=1) und Antibiotika (FA 20%/CB 27%, p=0,682) verabreicht. In der Langzeittherapie erhielten 43% der Katzen mit FA und 36% der Katzen mit CB inhalative Kortikosteroide (p=1), orale Kortikosteroide (FA 17%/CB 36%, p=0,220) und orale Bronchodilatatoren (FA 6%/CB 27%, p=0,084) sowie phasenweise Antibiotika (FA 6%/CB 18%, p=0,238). Behandlungsbedingte Nebenwirkungen (Polyurie/Polydipsie, Pilzinfektion im Gesicht und Diabetes mellitus) wurden bei 4 Katzen mit FA und 2 Katzen mit CB registriert. Die Mehrheit der Besitzer gab an, mit dem Ansprechen auf die Behandlung äußerst oder sehr zufrieden zu sein (FA 57%/CB 64%, p=1).

SCHLUSSFOLGERUNG

Signifikante Unterschiede hinsichtlich des Managements und des Therapieansprechens konnten bei beiden Erkrankungen laut Besitzerbefragung nicht festgestellt werden.

KLINISCHE RELEVANZ

Laut Besitzerumfrage können chronische Bronchialerkrankungen der Katze wie Asthma und chronische Bronchitis können mit einer ähnlichen Behandlungsstrategie erfolgreich therapiert werden.

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.

Comparison of signalment, clinical, laboratory and radiographic parameters in cats with feline asthma and chronic bronchitis

OBJECTIVES

Feline asthma (FA) and feline chronic bronchitis (CB) are common respiratory conditions in cats, frequently referred to as 'feline lower airway disease'. However, the aetiologies of both inflammatory airway diseases are probably different. Little is known about the differences in signalment, clinical signs, laboratory abnormalities and radiographic features between cats with these two airway diseases. The aim of the study was to investigate whether certain parameters can help in differentiating between both diseases, as distinguished by airway cytology.

METHODS

Seventy-three cats with FA and 24 cats with CB were included in the retrospective study. Inclusion criteria were compatible clinical signs and a cytological evaluation of bronchoalveolar lavage fluid indicating either FA (eosinophilic inflammation) or CB (neutrophilic inflammation) without cytological or microbiological evidence of bacterial infection. Parameters of signalment, physical examination, haematology and thoracic radiographs of both disease groups were compared statistically (P <0.05).

RESULTS

The median age of cats with FA was 6 years, and was 7.5 years in cats with CB (P = 0.640). The most commonly reported clinical signs in both groups were a cough (95% FA/96% CB; P = 1.000), pathological pulmonary auscultatory sounds (82% FA/79% CB; P = 0.766) and dyspnoea (73% FA/79% CB; P = 0.601). Abnormal radiographic lung patterns were detected in 94% of cats with FA and 91% with CB (P = 0.629), respectively. Blood eosinophilia was significantly more common in cats with FA (40%) compared with CB (27%) (P = 0.026).

CONCLUSIONS AND RELEVANCE

The study indicates that a differentiation of FA and CB by means of signalment, a single clinical sign, and haematological and radiographic findings is not possible.

Clinical features and radiographic findings in cats with eosinophilic, neutrophilic, and mixed airway inflammation (2011-2018)

Background

Idiopathic inflammatory airway disease (IAD) in cats often is described as asthmatic (eosinophilic) or bronchitic (neutrophilic), but this designation requires collection of airway fluid and it fails to consider cats with mixed airway inflammation.

Objective

To identify clinical features that would differentiate inflammatory disease types.

Animals

Forty‐nine cats with nonspecific airway inflammation identified by bronchoscopic bronchoalveolar lavage (BAL) between 2011 and 2018 were evaluated.

Methods

This is a retrospective study. Cats were categorized by BAL differential cytology as having eosinophilic (eosinophils >20% with neutrophils <14%, or eosinophils >50%), mixed (eosinophils 20%‐50% and neutrophils >14% or discordant inflammation from 2 BAL sites), or neutrophilic (neutrophils >14% and eosinophils <20%) inflammation. Type and duration of presenting complaints, signalment, body condition score, respiratory rate, CBC results, bronchoscopy, BAL results (% recovery, total nucleated cell count, differential cell count), and radiographic findings were compared among groups.

Results

Idiopathic IAD was diagnosed in 49 cats, with BAL eosinophilic inflammation in 23, mixed inflammation in 14, and neutrophilic inflammation in 12. Cough was the predominant presenting complaint with no difference in duration of signs among groups (median, 5.5 months). Respiratory rate and effort also did not differ. Cats with eosinophilic inflammation were significantly younger (4.4 ± 3.3 years) than those with neutrophilic (8.0 ±5.6 years) or mixed inflammation (7.5 ± 4.0 years; P = .03). Results of CBC and interpretation of radiographic findings did not differ among groups.

Conclusions and Clinical Importance

Substantial overlap exists in clinical and radiographic findings in cats with various forms of idiopathic airway inflammation.

Feline Asthma: Diagnostic and Treatment Update

Asthma is an important allergic lower-airway disease in cats affecting approximately 1% to 5% of the pet cat population. New diagnostics are being developed to help better differentiate asthma from other lower-airway diseases and improve monitoring. In addition, new treatments are being developed to help in refractory cases or in those cases in which traditional therapeutics are contraindicated. This article discusses potential pitfalls in the diagnosis of asthma. In addition, current literature investigating new diagnostic tests and therapies for feline asthma is reviewed.

Simultaneous visual inspection for barometric whole-body plethysmography waveforms during pulmonary function testing in client-owned cats

OBJECTIVES

For the purpose of applying a barometric whole-body plethysmography (BWBP) device as a routine clinical tool in client-owned cats, the objective of this study was to evaluate the methodological importance of simultaneous visual inspection (SVI) of graphic tracing.

METHODS

To investigate the effect of SVI on the results obtained, 50 client-owned cats were included. Breath-by-breath analysis was conducted with BWBP software, and a commonly used rejection setting was chosen for automatic elimination (AE) of non-breath artefactual waveforms, according to tidal volume (TV), inspiratory and expiratory time, and the difference between inspiratory and expiratory volumes. During 10 mins of data recording, SVI for BWBP waveforms was performed to record manually time periods that were free of any artefacts. The two datasets derived from AE alone (AEA method) and AE plus SVI (SVI-AE method) were compared. The inter-observer effect on the process of SVI was evaluated on six cats.

RESULTS

There were statistically significant differences (P <0.001) between the AEA and SVI-AE datasets for most BWBP parameters. Bland-Altman analysis of the parameter-enhanced pause (Penh) showed heterogeneous variances, indicating less agreement when the Penh values were large. Intra-individual coefficients of variation of Penh were significantly higher with the AEA method than with the SVI-AE method (61.1% vs 34.7%, respectively; P <0.001). Inter-observer agreement on the SVI process was excellent, and no statistically significant differences between the two observers were found for any BWBP parameters obtained by the SVI-AE method (P >0.05).

CONCLUSIONS AND RELEVANCE

Visual inspection for BWBP waveforms in real time can reliably identify stable breathing signals in client-owned cats. The obtained results were significantly different when the SVI method was used in addition to AE. In the interpretation of BWBP parameters or comparison of measurements among studies, whether an SVI methodology was applied should be considered.

Lung function changes in mice sensitized to ammonium hexachloroplatinate

Occupational exposure to halogenated platinum salts can trigger the development of asthma. The risk to the general population that may result from the use of platinum in catalytic converters and its emerging use as a diesel fuel additive is unclear. To investigate pulmonary responses to platinum, we developed a mouse model of platinum hypersensitivity. Mice were sensitized through application of ammonium hexachloroplatinate (AHCP) to the shaved back on days 0, 5 and 19, and to each ear on days 10, 11 and 12. On days 24 and 29, mice were challenged by oropharyngeal aspiration with AHCP in saline. Before and immediately after challenge, pulmonary responses were assessed using whole body plethysmography (WBP). A dose-dependent increase in immediate responses was observed in AHCP-sensitized and challenged mice. On days 26 and 31, changes in ventilatory responses to methacholine (Mch) aerosol were assessed by WBP; dose-dependent increases in Mch responsiveness occurred in sensitized mice. Lymph node cell counts indicate a proliferative response in lymph nodes draining the sites of application. Bronchoalveolar lavage fluid harvested from sensitized mice contained an average of 5% eosinophils compared to less than 0.5% in non-sensitized mice (p < 0.05); significant increases in total serum immunoglobulin E were observed for all sensitized mice. Although a second airway challenge on day 29 affected some results, only one airway challenge was needed to observe changes in lung function.

Functional phenotype and its correlation with therapeutic response and inflammatory type of bronchoalveolar lavage fluid in feline lower airway disease

Background

Currently, functional assessment to monitor therapeutic response in feline lower airway disease (FLAD) has limited application.

Objectives

To evaluate if expiratory indices derived from pseudo‐tidal breathing flow‐volume loop (pTBFVL) representing lower airway obstruction would decrease after clinical improvement and to investigate the correlation between functional phenotype and inflammatory cell type in bronchoalveolar lavage (BAL) fluid.

Animals

Nineteen client‐owned cats with FLAD.

Methods

Prospective observational study. Functional assessment with pTBFVL indices (eg, peak to mid‐expiratory flow; PEF/EF50) and conventional barometric whole body plethysmography (BWBP) parameters (eg, enhanced pause) was carried out before receiving treatment. BAL was performed to analyze inflammatory cell types. Signs were assessed by scoring. The cats were treated with glucocorticoids daily and functional testing was repeated.

Results

Loop indices PEF/EF50 and PEF/EF25 were significantly decreased after treatment (P < .001). Conventional BWBP parameters were not significantly different before and after treatment. Cats with PEF/EF50 > 1.51 before treatment had a significantly higher granulocyte (eosinophil plus neutrophil) percentage in BAL fluid (P = .014). Granulocyte percentage in BAL fluid was strongly correlated with PEF/EF25 (P = .001, r_s = 0.74) and moderately correlated with PEF/EF50 (P = .022, r_s = 0.57), whereas eosinophil or neutrophil percentage alone had no significant correlation with functional parameters.

Conclusions and Clinical Importance

Functional parameters including PEF/EF50 and PEF/EF25 can be used for monitoring therapeutic response. The presence of airflow limitation during mid‐ to late expiration is affected by the overall extent of granulocyte infiltration.

Functional assessment of expiratory flow pattern in feline lower airway disease

Feline lower airway disease (FLAD) is a chronic respiratory disease of which there is a lack of information on functional assessment in current veterinary medicine. The purposes of this study were to investigate expiratory pattern and evaluate the diagnostic utility of functional parameters in cats with FLAD. Thirty-three client-owned cats (23 FLAD cats and 10 control cats) were studied. Under quiet tidal breathing, pseudo-tidal breathing flow-volume loop (pTBFVL) was obtained from a barometric whole body plethysmography (BWBP) device. There were significant differences in the shapes of expiratory, but not inspiratory, curves between FLAD and control cats. The incidence of the presence of concave expiratory curve indicating lower airway obstruction was 74% in FLAD cats. To assess the diagnostic utility of pTBFVL indices in cats with FLAD, area under the receiver-operator curve was 0.86 for PEF/EF50 (peak expiratory flow divided by expiratory flow at end expiratory volume plus 50% tidal volume); a cuff-off value of PEF/EF50 >1.51 distinguished normal from FLAD (73.9% sensitivity, 100% specificity). There were no significant differences in traditionally measured BWBP parameters (ie, enhanced pause) between cats with and without FLAD in the present study. In conclusion, underlying change on expiratory flow pattern during natural tidal breathing existed in FLAD cats, and selected pTBFVL indices were useful in discriminating FLAD from normal cats. Tidal breathing pattern depicted by pseudoflow-pseudovolume loops from a BWBP system could be a non-invasive tool for functional assessment in client-owned cats.

Update on feline asthma

This article provides an overview of recent advances in the diagnosis and treatment of feline asthma. The authors discuss the potential pitfalls in the diagnosis of feline asthma. In addition, current literature investigating new therapies for the treatment of feline asthma is reviewed.