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 shape of the volumetric capnogram is modified by airway obstruction, an d the evaluation of this deformation could allow an indirect measurement of bronchial patency. The study included 35 horses; five horses without evide nce of pulmonary disease (group I) and 30 horses suffering from different d egrees of chronic obstructive pulmonary disease (COPD) (groups II-IV). Data of recorded CO2 and volume curves were off-line plotted and statistically analysed using regression analysis. Analyses were preformed separately for fractions 25-95% (VTE25-95), 25-50% (VTE25-50) and 50-95% (VTE50-95) of exp iratory tidal volume. For VTE25-95 estimates of linear and quadratic regres sion parameters were significantly different between groups. For VTE25-50 l inear terms were significant in all clinical groups and decreased considera bly from group I to group IV. Linear and quadratic terms for VTE50-95 were significant in all clinical groups and increased with the severity of COPD. The difference of total expiratory CO2 volume was significant between all groups. Statistical analysis of the volumetric capnogram is a precise metho d for description of shape deformities of the single breath diagram for CO2 (SBD-CO2) are helpful in the detection of pulmonary function impairment. H owever, although the model of the statistical shape analysis of the SBD-CO2 is precise, it may not necessarily be a useful test to discriminate horses with minor, moderate and severe COPD for clinical use.