The four-channel pneumogram in infants with recurring apneas and bradycardias

The two-channel pneumocardiogram (PCG) is frequently used for evaluating infants at risk for infantile apnea. In this study, the two-channel PCG failed to identify a significant number of symptomatic infants that were diagnosed by a four-channel pneumocardiogram. Nine infants suffering from either apparent life-threatening events (ALTE) or persistent apnea of prematurity were evaluated with two- and four-channel PCGs. The four-channel PCGs consisted of the standard two-channel evaluations, ECG and impedance pneumography, expanded by the addition of pulse oximetry and nasal thermistry. The PCGs were evaluated in a blinded manner by three trained observers. Each PCG was evaluated in both the two- and four-channel mode. A PCG was considered abnormal when any of the following was present: (1) a heart rate deceleration greater than one third of the baseline and lasting more than 8 seconds, (2) an apneic pause, either by impedance or by airflow, of greater than 20 seconds, (3) evidence of obstructive apnea less than 20 seconds but associated with cardiac deceleration, and (4) evidence of oxygen desaturation below 85% and lasting more than 8 seconds. All nine of the infants studied had recurrent apneic episodes at home. The four-channel PCGs were abnormal in all of the infants studied, whereas only four of the two-channel PCGs were abnormal (P less than .02). In this population, over 50% of the infants were incorrectly evaluated by the standard two-channel PCG and correctly identified by the four-channel PCG.