Childhood Adenotonsillectomy Trial

3.3 Maintenance of Blood Pressure Equipment

The condition of the instruments for BP measurement is too often neglected in common practice and should be a special responsibility of a designated staff member. This person should be sure to check the calibration of the manometers every 6 months or sooner if the arrow does not exactly point to the zero mark. This should be recorded on a calibration log. For the cuffs and stethoscope, their cleanliness and general working order can usually be determined by simple inspection. Those inspections should include a check of zero level, ability to accurately calibrate against a mercury meter, and the conditions of all tubings and fittings. If the aneroid gauge does not calibrate to zero against the mercury meter it must be replaced and should not be used for any purpose.

3.3.1 Checking Sphygmomanometer for Accuracy

Checking the sphygmomanometer used to record manual, resting blood pressure readings is accomplished by checking them for accuracy against a mercurial sphygmomanometer.

3.3.2 Calibration Procedures

1. Connect a two-way value onto the Mercurial unit
2. Apply a “Y” connector to that value. (“Y” connector and straight hose is taken from a double-headed stethoscope used for training purposes). The straight piece of hosing is then connected to the “Y” and onto the hose is connected the hand held sphygmomanometer to be compared to the mercurial unit.
3. Wrap a standard adult blood pressure cuff snuggly around either a calibration spirometer tube (if available) or other rigid cylinder approximately 8 inches in diameter.
4. Attach the hose that once held a sphygmomanometer to the other end of the “Y” connector.
5. Turn on the mercurial sphygmomanometer switch to release the mercury. By pumping up the blood pressure cuff the hand held unit and mercury unit should both increase at the same rate.
6. Take both units up to 230 then slowly release at a rate of 2mm per second while comparing the numbers. The reading should match on both units. It is possible to stop the airflow and again check both units for matching numbers.
7. Continue this all the way down to zero.
8. Turn off the mercury switch at the bottom of the unit. Record the serial number and date checked on the calibration log.

This procedure checks the aneroid sphygmomanometer against the mercurial unit for accuracy. If the unit is out of sync it must replaced and it should not be used.

Label calibrated unit (s) “CHAT” to ensure accuracy and consistency in data collection.