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

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.

Clinical Application of Pulmonary Function Testing in Small Animals

Pulmonary function tests (PFTs) are important diagnostic tools that have wide clinical applications in human and veterinary medicine. Widespread use of PFTs in measuring lung volumes in veterinary medicine was historically limited by the need for specialized equipment to accurately perform and interpret these tests, and by lack of patient cooperation. However, recent advances and modifications have allowed PFTs to be safely performed in conscious veterinary patients with minimal stress. This article focuses on the most commonly used tests of pulmonary function including tests of pulmonary mechanics and of gas exchange in the lungs.