Statistical shape analysis of volumetric capnograms: evaluation of a new approach for the assessment of pulmonary function in horses with chronic obstructive pulmonary disease.

The research conducted statistical shape analyses of volumetric capnograms in order to assess pulmonary function in horses with chronic obstructive pulmonary disease (COPD), revealing distinctions between groups of varying disease progression but suggesting limited clinical utility for distinguish between minor, moderate, and severe COPD.

Study Design and Participants

• The research involved 35 horses divided into two main groups: one group of five horses without any known pulmonary disease (Group I) and another group of 30 horses that were suffering from varying degrees of COPD (Groups II-IV).
• The disease severity of the horses in the latter group determined their placement within Groups II-IV.

Methodology

• Data collected from the horses included recorded CO2 and volume curves. This data was analysed offline using regression analysis.
• The analysis specifically examined three fractions of expiratory tidal volume: 25-95% (VTE 25-95), 25-50% (VTE 25-50) and 50-95% (VTE 50-95).
• The shape of the volumetric capnogram could indirectly indicate the patency of the bronchi, potentially indicating airway obstruction.

Results

• Significant differences were found in linear and quadratic regression parameters among groups for VTE 25-95 estimates.
• In all clinical groups, linear terms were significant for VTE 25-50 and decreased substantially from Group I to Group IV.
• Linear and quadratic terms for VTE 50-95 were seen to be significant across all clinical groups, showing an increase in line with COPD severity.
• A notable difference was observed between all groups in terms of total expiratory CO2 volume.

Conclusions

• The statistical analysis of volumetric capnogram data is a highly accurate method for determining the shape deformities present in the single breath diagram for CO2 (SBD-CO2) in horses suffering from COPD.
• Comprehensive models that include Phase II and III of the SBD-CO2 can assist in identifying impairments to pulmonary function.
• Despite the precision of the statistical shape analysis of the SBD-CO2 model, it might not be a useful tool for accurately identifying horses with minor, moderate, or severe COPD for clinical applications.