Data analysis and calculations
Equivalence between NIBP and invasive measurements in the FA, TFA, MT and Ao was assessed with a linear mixed-effects model using commercially available statistics software (Prism 10 for MacOS, v.10.0.2, GraphPad Software).17 Pre-established equivalence criteria were based on guidelines from the American Association for the Advancement of Instrumentation in humans and as used in previous studies in horses.11,18 Measurements were deemed equivalent if the mean difference and their 95% confidence intervals between NIBP and invasive measurements for a specific location fell within ± 5 mmHg and if the results were not statistically significantly different (p> 0.05). Sensitivity, specificity, 95% confidence intervals,19 false positives (percentage of instances where NIBP indicated hypotension when MAP in the FA was ≥ 70 mmHg), and false negatives (percentage of instances where NIBP indicated normotension when MAP in the FA was < 70 mmHg) of the NIBP technique based on an intention to treat hypotension (MAP < 70 mmHg) measured in the FA were calculated (Microsoft Excel for MAC, Version 16.78.3), and an optimum cut-off for treatment of hypotension when using the oscillometric technique was determined. The variability of MAP measurements at the peripheral invasive sites relative to the Ao was determined by calculating the coefficient of variation of the differences between each peripheral location and the measurement obtained centrally in the Ao.