Alterations in tidal volume over recording time during pulmonary function testing by barometric whole-body plethysmography in client-owned cats: a multicenter retrospective investigation.

Background: Pulmonary function assessment in small animal clinical patients typically relies on tidal breathing analysis, such as placing cats in a barometric whole-body plethysmography (BWBP) chamber. Despite its wide application in various clinical scenarios, the recording time for BWBP has not been standardized. Variability in resting tidal volume (TV) during natural breathing is significant, impacting the detection of airflow limitation in obstructive airway disease. This multicenter investigation aimed to examine the consistency of TV alterations over the BWBP recording period across different regions, identify influential factors associated with signalment or emotion of the cat, and determine whether the recording time for BWBP in clinical cats could be shorter than in previous studies.

Results: This is a multicenter retrospective study. A total of 131 BWBP recordings from clinical cats across four sites in different countries were enrolled. Ventilatory parameters calculated from short sections using 5 and 20 breaths at the first site showed no significant difference (P > 0.05). Among all sites, TV of the initial period (TV-initial, median 32.5 mL, range 4.9-162.9) was significantly greater than TV of the middle (TV-mid, 29.9 mL, range 6.7-144.6) (P < 0.001) and the late (TV-late, 27.5 mL, range 5.1-144.8) (P < 0.001) period of the recording, while TV-mid and TV-late were not significantly different (P = 0.19). The trend of alterations in TV was not affected by site, emotional status, health status, age, or gender. Forest plots with 95% confidence intervals of TV generated from short sections, alongside conventional data averaging breaths over a 5-minute period (TV-All), showed acceptable margins of error at all sites. TV-mid and TV-late were closest to TV-All, whereas TV-initial was larger than TV-mid, TV-late, and TV-All.

Conclusions: TV in clinical cats within the BWBP chamber tends to decrease with recording time. When a shorter section of breaths is desired for clinical evaluation, selecting 5 or 20 breaths from the beginning period of recording would have a higher TV, which might be advantageous for investigating obstructive airway problems. Alternatively, breaths selected from the middle or later stages of recording would be more representative of relaxed breathing over a longer period of time.