The American Heart Association (AHA) has issued a science advisory regarding hospital telemetry systems used to monitor patient heart rhythms, hemodynamic parameters, and oxygen saturation. A delay between the real-time status of a patient and the electrocardiographic (ECG) information shown on the patient monitor may occur with some wireless systems, potentially compromising the safety of patients whose treatment must be based on real-time rather than on "near-time" displays of rhythm disturbances.

The problem stems from wireless networked systems, which unlike older hard-wired systems, don't directly transmit data from the patient's ECG leads. Instead, the patient's data are sent to a central network server, where they're processed and then sent back to the monitor at the patient's bedside. Delays of up to five seconds in supposedly continuous ECG data have been reported, and delays of eight seconds have been reported in pulse oximetry waveforms. The duration of the delay varies with the amount of wireless interference, network load, and server processing time. Such delays can occur in any commercial wireless monitoring system and network.

Delayed displays of ECG data can lead to inappropriate treatment. For example, in one documented incident a physician attempting cardioversion observed continuing atrial flutter on a wireless telemetry screen after delivering a synchronized shock. Because the first shock appeared to have been ineffective, the physician prepared to deliver a second shock. Fortunately, after a five-second delay, the bedside telemetry monitor did show that the first shock had produced sinus rhythm and no harm was done.

The AHA report recommends that wireless telemetry systems not be used for pacemaker or defibrillator testing, insertion of temporary pacing electrodes, cardiac resuscitation, or acute treatment of hemodynamically significant or unstable arrhythmias. Patients needing such treatment should be hardwired to a bedside monitor that's within view of the care providers to prevent inappropriate therapies or adverse outcomes that could result from delayed rhythm data. In cardioversion or defibrillation, separate monitoring leads should be connected directly to the monitor of the external defibrillator to ensure instantaneous readings.

"Nursing supervisors and nurses on telemetry floors should check with their hospital bioengineering group or telemetry manufacturer to determine whether their systems are affected," lead author Mintu P. Turakhia told AJN. If they are, providers should take steps to ensure that wireless telemetry isn't used in situations in which instantaneous monitoring is required.-Carol Potera

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