What BP device to use

Dr. Rolando Mendiola, a general practitioner in Caloocan City, is asking if the mercury sphygmomanometer should no longer be used.

Actually, the Department of Health already issued an administrative order (AO 21) two years ago mandating gradual phaseout of mercury-containing devices in all Philippine healthcare facilities and institutions. This is because of the potential risk of mercury poisoning just in case the sphygmomanometer’s tubing leaks or bursts. Such directive is actually part of a global policy to shift to nonmercury-containing medical devices, including thermometers and BP-measuring instruments.

The World Health Organization issued a policy paper around seven years ago raising concerns over the safety of mercury-containing devices. Hence, it called for “short-, medium- and long-term measures to substitute mercury-based medical devices with safer alternatives.” This was endorsed by a resolution from the World Medical Association passed in 2008.

The local medical organizations, including hypertension experts and heart specialists, are complying with this directive with reservations. In fact, I recall a consensus meeting, pooling experts from the Philippine Heart Association and Philippine Society of Hypertension, which was organized by Dr. Rey Neri and his PHA council on hypertension sometime in 2010 to come up with recommendations about a possible compromise on the DOH directive.

The consensus was that the mercury sphygmomanometer has been used since time immemorial to determine an individual’s BP, and no one can dispute that up to now, it remains the gold standard in measuring the BP. Before it could be phased out, a substitute gold standard must be in place first.

The experts also noted that mercury poisoning due to breakage of the sphygmomanometer consists only of a very small percentage of cases. One would likely get it more from breathing contaminated air, ingesting foods with high mercury residues during processing, exposure to mercury vapor from mercury amalgam used in dental procedures, or improper disposal of busted fluorescent lamps.

I share the consensus’ belief that in the order of urgency, all the above potential sources of mercury poisoning should be addressed first before phasing out completely mercury sphygmomanometers.

We support the phaseout and banning of mercury sphygmomanometers for home use, and we recommend the easy-to-use automated BP devices for self-monitoring of the BP at home; but for medical institutions, especially the emergency rooms, intensive care units and operating rooms, the mercury sphygmomanometer would still be more reliable.

Our group in the PSH found that these devices are accurate only with BP levels between 80/60 mm Hg and 180/110 mm Hg. Outside of these BP ranges, the accuracy wanes.

It’s true that most would have BP levels within this range, and that’s why we recommend these digital or automated devices for self-monitoring of the BP by hypertensive patients at home. But there are still quite a number with BPs either too low, as in patients in a state of shock, or too high as in patients with hypertensive urgency or emergency.

These are the cases wherein the doctor needs to be guided by an accurate device to measure the patient’s BP so he or she could be properly guided what medication or intervention to give or do to the patient.

Rather than order for a complete phasing out of the sphygmomanometer, we can just reeducate healthcare practitioners on how to check if their sphygmomanometer devices have leaks, and how to dispose of the mercury safely in the very rare event of a leak.

Going back to Dr. Mendiola’s question, I cannot give a clear-cut answer but we can offer a recommendation. We should start using for most patients in our clinics the automated or digital BP devices but still have a mercury sphygmomanometer at hand to recheck the patient’s BP when it’s either too high or too low. This may be a “hybrid compliance” with the DOH directive, but I’m sure we can never be blamed for thinking of the patient’s best interest.