• dogs;
  • pulmonary function tests;
  • reference values


Reference values for dogs regarding tidal breathing flow volume loop (TBFVL) parameters are scarce in the veterinary literature, so each new study requires a healthy reference population to be studied simultaneously with the diseased one.


To establish reference values for TBFVL parameters in healthy dogs, to detect any potential variability in loop shape and in various TBFVL parameters and to propose clinically useful parameters for TBFVL analysis.


Cross-sectional, prospective study.


Twenty-one healthy, unsedated, untrained, young adult, male Beagle dogs, with minimum variability in body weight and somatometry were used. Their good health status was confirmed by physical examination, complete blood count, serum biochemistry, urinalysis, serology and parasitology for Dirofilaria immitis, faecal examination, arterial blood gas analysis, electrocardiography, and radiographic and endoscopic examinations of the respiratory tract. The shape of the TBFVLs was assessed initially. Volume, time and flow parameters, as well as their ratios, were calculated; in total 44 parameters were evaluated. Statistical indices, including Cronbach's α, discrimination index, coefficient of variation (CV) and 95% confidence intervals were estimated for each parameter.


One consistently reproducible type of TBFVL shape was identified that had a similar appearance to the letter D. Statistical analysis showed that only two parameters were found to have Cronbach's α lower than 0.80. The CV for the TBFVL parameters ranged from 1.5% to 49%, but the vast majority had values lower than 20%. Eight parameters had very low CV, indicating increased homogeneity.


A large number of clinically applicable TBFVL parameters were identified. Parameters related to flow and time were considered to correlate more objectively to the functional capacity of the respiratory system of healthy, unsedated dogs.