Martel et al 7
for artifactual BP increases related to anxiety and/or
excitement caused by the measurement condition. To
manage this risk of bias, the ACVIM consensus panel
defined a standardised measurement process.
The second source of error is related to the method
used for BP measurement in the clinical environment.
While the methods recognised as the most accurate and
reliable are direct invasive measurements using an intraarterial catheter,18
the invasiveness and technical difficulty
of these methods has limited their clinical acceptance, and
indirect BP measurement methods are widely preferred.
In this study, we used as a reference method implanted
telemetry, which is a direct and invasive BP measurement method applicable for long-term measurement
in
non-sedated animals. This method was subjected to
numerous validation studies in various species, including rats,19
dogs,20 monkeys21-23 and cats,24 and which is
recognised as a gold standard. Therefore, we compared
HDO measurements under measurement conditions
matching with the ACVIM consensus panel's recommendation by comparing data achieved with the gold
standard method for BP measurement in non-sedated
animals. Moreover, in order to cover various clinical
states, measurements were not focused on normal BP
values only, but included high and low BP pressure levels similar to BP
levels expected in case of hypertension
or hypotension, respectively.
With this approach, HDO displayed a good agreement level, meeting the AAMI3
requirement defined for
BP measurement in humans, ie, 5 ± 8 mmHg of the
measurements obtained with the reference method.
However, less than 95% of the HDO data lay within 10
mmHg of the reference telemetry measurements, as
required for AAMI validation. Nevertheless, if we consider the updated criteria defined by the ACVIM
consensus panel,2
which take into account specific
challenges when measuring BP in conscious animals,
these data indicate that HDO provides a faithful measurement
of SBP in conscious cats. To our knowledge,
this is the first study in which an indirect BP technique,
here HDO, has met the validation criteria of the ACVIM
consensus panel.
In healthy humans25,26 or rodents,27 owing to the
mechanical properties of the vasculature along the arterial tree,
SBP is higher at peripheral sites, the brachial or
tail artery compared with a central site such as the thoracic aorta. Direct
SBP measurements in cats were performed in the distal abdominal aorta, whereas
HDO
measurements were performed at the level of the coccygeal artery.
The absence of significant difference between
the two methods in measuring SBP suggests that the
measurement sites chosen were close enough to enable
this comparison. When simultaneous SBP measurements
were obtained at low BP levels, ie, <110 mmHg, HDO
overestimated SBP by about 10 mmHg. The reduced
number of observations available for analyses when
data were allocated in SBP level sub-groups likely contributed to this finding, but these results
are in
Table 2 Agreement between systolic blood pressure (SBP) and diastolic blood pressure (DBP) values measured with
high-definition oscillomtery and telemetry
Paramete Pressure
group
Bias
(mmHg)
Limits of agreement
(mmHg)
% of paired
measurement
within ± 10 mmHg
% of paired
measurement
within ± 20 mmHg
SBP Low -10.8 ± 11.3 12.1 ± 4.1 100 ± 0 100 ± 0
Normal -3.4 ± 3.8 17.6 ± 1.8 94 ± 6 98 ± 3
High 2.9 ± 1.3 20.6 ± 8.0 77 ± 13 92 ± 9
Overall -2.2 ± 1.1 21.6 ± 2.6 88 ± 3 96 ± 2
DBP Low 14.6 ± 5.5 14.3 ± 4.9 27 ± 25 67 ± 29
Normal 24.6 ± 2.0 15.7 ± 4.1 3 ± 4 20 ± 15
High 36.0 ± 6.3 22.3 ± 9.4 7 ± 10 13 ± 13
Overall 22.3 ± 1.6 22.6 ± 1.9 13 ± 4 38 ± 7
Mean (± SD) data calculated from individual data achieved in six animals
Table 3 Agreement between diastolic blood pressure (DBP) values measured with telemetry (Tel) and mean blood
pressure (MPB) measured with high-definition oscillometry (HDO)
Parameter Bias
(mmHg)
Limits of agreement
(mmHg)
% of paired
measurement
within ± 10 mmHg
% of paired
measurement
within ± 20 mmHg
DBP Tel/MBP HDO 1.7 ± 0.7 14.9 ± 2.3 93 ± 5 99 ± 2
Mean (± SD) data calculated from individual data achieved in six animals