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Comparison between pulseoximetry and transthoracic impedance alarm traces during home monitoring


Objective: To compare transthoracic impedance (TTI/ECG) and pulse oxymetry (Po) alarm traces detected during home monitoring in infants at risk of apnoea, bradycardia and hypoxemia.

Study design: A retrospective evaluation of the monitor downloads of 67 infants who had undergone either TTI/ECG or Po home monitoring using a device that allows for detecting both parameters.

Patients and Methods: The patients belonged to the following diagnostic categories: Apparent Life-Threatening Events (ALTE, n=39), Preterms (Pt, n=21) and Miscellaneous (Mi, n=7). TTI/ECG and Po alarm traces were downloaded and inspected in order to score as either true or false alarms. Classification criteria were based on the visual analysis of the impedance and plethysmographic waveforms which were captured by the memory monitor every time the alarm thresholds were violated.

Results: Over a total period of 3,452 days of monitoring, 5,242 alarms occurred; 4,562 (87%) were false and 680 (13%) true. The mean duration of monitoring was 51 days (range 5-220 days). Overall TTI/ECG false alarms were 2,982 accounting for 65% of the total, while there were 1,580 Po false alarms (35%), (p=.0042). Among the 680 true alarms, 507 (74%) were desaturations not attributable to central apnoeas, while the true TTI/ECG alarms accounted for 173 (26%) (p=.0013).

Conclusions: The comparison between PO and TTI/ECG alarm traces has shown that true events were mostly attributable to desaturations, while false alarms were mainly provoked by TTI/ECG. The total number of the false alarms is lower than that reported in other studies adopting TTI/ECG only, thus indicating that monitoring using both Po and TTI/ECG is suitable for home use. When the combination of both techniques is not feasible or not required, we recommend the use of motion resistant pulseoxymetry alone.

  • home monitoring
  • pulse oximetry
  • transthoracic impedance

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