Comparison of lingual oscillometric and invasive blood pressure measurement in dogs under general anaesthesia

OBJECTIVES: The objective of the study was to evaluate agreement between tongue-based oscillometric and invasive arterial blood pressure in anaesthetised dogs, assess performance against American College of Veterinary Internal Medicine and Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization validation criteria and examine proportional bias overall and by body size and phenotype. MATERIALS AND METHODS: Prospective observational study of 89 client-owned dogs undergoing general anaesthesia. Simultaneous tongue-based oscillometric and invasive arterial systolic, mean and diastolic pressures were recorded at 5-minute intervals (1780 paired observations). Agreement was assessed using Bland-Altman analysis and performance judged against American College of Veterinary Internal Medicine and Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization criteria. Proportional bias (difference vs. mean pressure) was evaluated with linear mixed-effects models with dogs as a random effect, with body size (≤10 kg vs. >10 kg) and phenotype (chondrodystrophic vs. non-chondrodystrophic) as interaction terms. RESULTS: American College of Veterinary Internal Medicine criteria were met for mean and diastolic but not systolic pressure; no measure met Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization thresholds. Limits of agreement for mean and diastolic pressures were wide. Systolic pressure showed magnitude-dependent underestimation, whereas mean and diastolic pressures did not. Underestimation increased with systolic pressure in dogs >10 kg and in non-chondrodystrophic dogs, whereas no clear pressure-dependent trend was seen in dogs ≤10 kg or in chondrodystrophic dogs. Transient tongue swelling occurred in one dog; no other tongue-related adverse events were recorded. CLINICAL SIGNIFICANCE: Tongue-based oscillometry achieved acceptable agreement for mean and diastolic arterial pressures according to American College of Veterinary Internal Medicine criteria but did not meet Association for the Advancement of Medical Instrumentation/European Society of Hypertension/International Organization for Standardization validation standards. However, limits of agreement remained wide, and tongue-based oscillometric blood pressure should be interpreted cautiously and in conjunction with clinical context, rather than as a direct substitute for invasive blood pressure measurements. When invasive monitoring is unavailable, it remains useful for following trends in mean and diastolic pressure. Systolic values should be interpreted cautiously, particularly at higher pressures in dogs >10 kg or non-chondrodystrophic dogs.