BACKGROUND: It would be useful to have a clinical test that increases the suspicion of white coat hypertension (WCH) during the medical consultation. OBJECTIVE: To evaluate the Slow Breathing Test (SBT) when differentiating hypertension from WCH. METHODS: 101 hypertensive patients selected at triage had their medication withdrawn for 2-3 weeks. The blood pressure (BP) was measured before and after the SBT at two consultations at the office. The test consisted in breathing for 1 minute at the frequency of one respiratory cycle every 10 seconds. Two diagnostic criteria were compared: 1 - decrease in diastolic BP >10% in at least one visit or 2- decrease in BP to normal levels (<140/90 mm Hg) in at least one visit. The ambulatory blood pressure monitoring (ABPM) was performed while blinded to the clinical measurements. RESULTS: 71 women and 30 men, with a mean age of 51+10 years, with mean pre and post-test BP of 152+17/ 99+11 and 140+18/ 91+11 mm Hg were assessed. Nine patients had normal clinical and ambulatory measurements. Of the 92 patients, 28 (30%) were classified as having WCH; 15 had a positive test for Criterion 1 and 21 for the Criterion 2. Among 64 (70%) hypertensive individuals, 14 tested positive for Criterion 1 and 12 for Criterion 2. Sensitivity and specificity (95% CI): 0.54 (0.36-0.71) and 0.78 (0.67-0.87) for Criterion 1; 0.75 (0.57-0.87) and 0.81 (0.70-0.89) for Criterion 2. CONCLUSION: The SBT showed an increase in the clinical suspicion of WCH in two visits when using the BP normalization criterion. This finding suggests that the test can help in the optimization of ABPM requests for suspected cases.
Hypertension; respiratory function tests; blood pressure monitoring; ambulatory
