Apnea Monitors
Apnea monitors are part of the patient monitoring systems in the PICU and NICU
(Neuman, 1988a). Some stand-alone apnea-monitoring systems are frequently used in
the home for infants who have had apneic episodes in the hospital or who are at risk of
apnea. (See Figure 93-7.) These incorporate heart rate monitoring as well as respiratory
monitoring. Monitoring of breaths is typically done by transthoracic impedance monitoring.
The same electrodes that are used to detect the ECG for heart rate monitoring are
used to conduct a low-level, high-frequency (20-100 kHz) current through the infant.
Breathing motions change the impedance, thus resulting in a voltage change detected by
the monitor. When the monitor senses that breathing motions have ceased, it alarms after
a delay of typically 20 seconds. The alarm alerts the care-giver to intervene. In many