Cardiac aliasing--a possible cause for the misinterpretation of cardiorespirographic data in neonates.

Cardiac aliasing is a physiological phenomenon generating respiratory sinus arrhythmia in a frequency range lower than that of respiration if the mean respiration rate exceeds half of the mean heart rate. This was found in 8 out of 39 healthy fullterm newborns, 5 out of 33 fullterm and 3 out of 63 preterm newborns during intensive care. Quantification of cardiorespirographic data is considerably impaired in those cases when the mean respiration rate markedly exceeds half of the mean heart rate (two out of the 39 healthy full term newborns).