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.