USE OF A MAGNIFIED CARDIAC AIR-FLOW OSCILLATION TO CLASSIFY NEONATAL APNEA

Currently the classification of neonatal apnea relies upon an inferenc e of airway closure based upon the presence of breathing efforts again st such an obstruction. In this study we evaluate a new method of clas sification which utilizes the presence or absence of cardiac airflow o scillation to detect airway closure. Specifically, this evaluation con sisted of an examination of the transmission characteristics of an art ificially produced airflow oscillation through discrete airway narrowi ng in a model system; a confirmation that voluntary upper airway occlu sion in adult volunteers uniformly induces complete loss of the oscill ation; and a comparison of the cardiac oscillation method with the tra ditional method of apnea classification in a cohort of 4,309 apneas in 32 infants. We determined that the amplitude of the oscillation is ne gatively correlated with resistance (r = 0.97) and positively with the radius (r = 0.98) of narrowing in a model system, and that voluntary airway obstruction in adult subjects uniformly results in loss of tran smitted cardiac oscillations. Moreover, although there was similarity in the frequency distribution of central, obstructive, and mixed apnea s in our infants, there were statistically significantly greater obstr uctive events detected by the cardiac oscillation method. In addition, the cardiac oscillation method had the additional advantage of provid ing information regarding the timing of airway obstruction during apne a.