Awakenings change results of nighttime ambulatory blood pressure monitoring.
OBJECTIVE
Investigate the effect of distinguishing nighttime and sleep on nocturnal blood pressure results in ambulatory blood pressure monitoring.


METHODS
We recruited 36 patients, 29 men, with suspected obstructive sleep apnea/hypopnea syndrome attending a sleep clinic for diagnostic polysomnography and who agreed to wear a Spacelabs 90207 ambulatory blood pressure monitor during polysomnography. Their mean age was 45+/-11 years; body mass index (BMI), 30.8+/-5.4 kg/m; apnea-hypopnea index, 35+/-29 AH/h; 13 had a history of hypertension. A microphone attached to the ambulatory blood pressure monitor recorded its sounds in the polygraph and allowed us to classify each ambulatory blood pressure monitoring measurement as being made in electrographically-determined wake (e-wake) or sleep state (e-sleep).


RESULTS
Patients were asleep during (mean+/-SD) 61+/-24% (range 0-100%) of the 14+/-1 nighttime blood pressure measurements. Systolic and diastolic ambulatory blood pressure monitoring readings were significantly higher during e-wake (121+/-12/73+/-9 mmHg) than during total nighttime (119+/-11/70+/-8 mmHg) and e-sleep (116+/-13/68+/-9 mmHg). On the basis of nighttime measurements, 22 patients (61%) had nocturnal hypertension. On the basis of measurements made during e-sleep, nocturnal hypertension was diagnosed in 12 patients (33%; chi2=5.54; P=0.018). A multiple linear regression model showed that the percentage of measurements made in e-sleep was the only variable that significantly explained the difference between nighttime and e-sleep blood pressure figures, when controlling for sex, age, BMI, apnea-hypopnea index, and lowest SaO2.


CONCLUSIONS
During ambulatory blood pressure monitoring, nighttime blood pressure readings are higher than during e-sleep and this changes dipping and nocturnal hypertension classification.
Lenz
Maria C S
MC
Sleep Clinic and Cardiology Unit, Hospital de Clinicas, UFRGS, Porto Alegre, Brazil.
Martinez
Denis
D
D000328:Adult; D000368:Aged; D001143:Arousal / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory / Q000592:standards; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012890:Sleep / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*