A comparison of indirect blood pressure monitoring techniques in the anesthetized cat.

OBJECTIVE: To determine the accuracy of three indirect blood pressure monitoring techniques (oscillometric technique [OS], Doppler [DOP], and optical plethysmography [OP] [blood pressure determined with a pulse oximeter waveform]) when compared with direct arterial pressure measurement in cats. STUDY
DESIGN: Prospective study. ANIMAL POPULATION: Eight healthy (five female, three male), domestic short-hair cats weighing 3.5 +/- 0.8 kg
METHODS: Cats were anesthetized with isoflurane. The inspired concentration of isoflurane was adjusted to produce mild hypotension (80 to 100 mm Hg direct systolic), moderate hypotension (60 to 80 mm Hg direct systolic), and severe hypotension (< 60 mm Hg direct systolic). Indirect pressure measurements were obtained from the thoracic limb and compared with concurrent direct measurement using regression analysis and a modification of Bland and Altman's technique.
RESULTS: All three techniques underestimated systolic pressure. OS produced the best prediction of systolic pressure with a bias +/- precision of -15.9 +/- 8.1 mm Hg. DOP and OP were relatively inaccurate with a bias +/- precision of -25 +/- 7.4 mm Hg and -25 +/- 7.5 mm Hg. All three techniques correlated well with direct pressure with r values of 0.81, 0.88, and 0.88 for OS, DOP, and OP. DOP and OP provided an accurate prediction of direct mean arterial pressure with a bias +/- precision of -0.8 +/- 6 mm Hg and 0.6 +/- 5.5 mm Hg. Correlation was good between DOP and mean arterial pressure with r = 0.89. Correlation was also good between OP and mean arterial pressure with r = 0.90.
CONCLUSIONS: OS provided the most accurate prediction of direct systolic pressure. DOP and OP provided a good prediction of mean arterial pressure in the cat. CLINICAL RELEVANCE: All three of these techniques are useful for detecting trends. Direct monitoring of blood pressure should be considered if accurate blood pressure measurement is required.