Enhanced breathing effort in pulmonary function tests by CO2/O2 gas mixture and barometric whole-body plethysmography in healthy and feline lower airway disease cats.

Objective: Enhancing ventilatory effort during pulmonary function testing can help reveal flow limitations not evident in normal tidal breathing. This study aimed to assess the efficacy and tolerability of using a CO2/O2 gas mixture to enhance tidal breathing with a barometric whole-body plethysmography system in both healthy cats and those with feline lower airway disease (FLAD).

Methods: This prospective study included healthy cats and those with FLAD, which underwent pulmonary function testing and were exposed to a 10% CO2/90% O2 gas mixture in a barometric whole-body plethysmography chamber, with CO2 concentrations maintained within the target range of 5% to 10%.

Results: A total of 10 healthy cats and 15 FLAD cats were included. In healthy cats, tidal volume, minute volume, peak inspiratory flow, and peak expiratory flow per kilogram body weight increased significantly by medians of 4.3-, 3.5-, 3.1-, and 4.0-fold, respectively (P = .005). Cats with FLAD showed similar results, with 4.1-, 3.2-, 2.8-, and 3.7-fold increases (P < .001). Respiratory rate decreased in both healthy (52 to 40 breaths/min; P = .005) and FLAD cats (57 to 45 breaths/min; P = .04) after CO2 enhancement. All cats tolerated the CO2/O2 gas mixture well, with recovery within 60 to 120 seconds after returning to room air.

Conclusions: A CO2/O2 gas mixture successfully enhanced ventilatory variables in tidal breathing analysis and showed good tolerability in both healthy and FLAD cats.

Clinical relevance: This approach provides a practical option for short-term breathing effort enhancement in cats for clinical settings.