Effect of Maxillomandibular Advancement Surgery on Blood Pressure in Patients with Obstructive Sleep Apnea

There is an increased prevalence of hypertension and obesity among patients with obstructive sleep apnea (OSA). Although there is evidence that treatment of OSA with continuous positive airway pressure (CPAP) improves blood pressure in patients with hypertension, this evidence is lacking in the use of maxillomandibular advancement (MMA) surgery to treat OSA. Obesity is a well-established cardiac risk factor and can contribute to hypertension. The objective of this prospective study is to determine the effect of MMA surgery for treatment of OSA on blood pressure (mean arterial pressure (MAP)) and body mass index (BMI).

Ethics approval was obtained from the local research ethics board. As of August 2009, all patients at the QEII Health Sciences Centre undergoing MMA surgery for treatment of OSA, diagnosed by polysomnography, were asked to participate in the study. Informed consent was obtained from all willing subjects. Using a Tiba Ambulo 2400 ambulatory blood pressure monitor, blood pressure was recorded every 30 minutes during the day and every 60 minutes at night for a 24 hour period prior to, and at three and six months following MMA surgery. BMI was also recorded for each patient preoperatively and three and six months postoperatively.

Of 45 potential subjects, fourteen patients are currently enrolled in this ongoing study. Nine patients have a complete data set. This group is comprised of two females and seven males with an average age of 48.4yrs and a mean preoperative BMI of 30.7kg/m². Four of these patients had a diagnosis of hypertension preoperatively of which one patient was on antihypertensive medications.

Using a repeated measures ANOVA test, The BMI was found to decrease on average from 30.7kg/m² to 29.0kg/m² at the 6 month follow up (p <0.01). The most significant drop was noted in the first three months following surgery.  The group average mean 24 hour MAP and mean awake MAP decreased slightly at three months, but then increased to near preoperative values by six months. The group average mean sleep MAP decreased from 83.7mmHg to 82.3mmHg at six months. None of these changes demonstrated statistical significance (ANOVA). At six months, a decrease in mean 24 hour MAP was noted in four patients, whereas mean awake and sleep MAP decreased in five patients. Using a Pearson correlation test, changes in blood pressure were not found to be correlated with changes in BMI.

Although the literature infers that treatment of OSA with CPAP may improve blood pressure, many of these studies are short term (less than three months), and are not based on data obtained by the use of a 24 hour ambulatory blood pressure monitoring device.

In conclusion, an improvement in BMI was noted in almost all patients with an overall decrease from a BMI in the obese category (30.7kg/m²) to a BMI in the overweight category (29.0kg/m²). In this patient population, MMA surgery for treatment of OSA demonstrated no significant effect on blood pressure. There was no correlation between changes in BMI and changes in blood pressure in these nine patients. A study focusing exclusively on OSA patients with hypertension preoperatively is may demonstrate a more significant change in blood pressure postoperatively.

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