Pulmonary function changes and clinical findings associated with chronic respiratory disease in calves

Thirteen field cases of chronic respiratory disease in crossbred calves aged between 1 and 8 months were subjected to a standardized examination in which clinical criteria were scored and weighted to allow quantification. Predicted values for pulmonary function variables were generated using regression equations previously established in normal calves which related measured pulmonary function variables to thoracic perimeter. Subsequent pulmonary function testing of each calf was undertaken and values obtained compared with predicted values and correlated with clinical scores. Diagnosis was confirmed at post-mortem examination. Calves with chronic respiratory disease had significantly reduced inspiratory and expiratory times, tidal volume, dynamic compliance and PaO2, significantly increased respiratory frequency, airway resistance and PaCO2 and more negative transpulmonary pressure values when compared to predicted pulmonary function values for the same calves. PaO2 and PaCO2 were the only variables correlated with clinical scores, suggesting their value in the assessment of severe cases of calf respiratory disease.