The Collaborative Home Infant Monitoring and Evaluation (CHIME) Study 

 The CHIME Study, now complete, was a multicenter, cooperative study of home monitoring of high-risk infants. Almost 1,200 infants were enrolled in the following subject groups: healthy term infants; preterm infants weighing less than 1,750 grams; and siblings babies who died of SIDS or experienced an idiopathic apparent life-threatening event. The objectives of the study were to:

• Determine whether home apnea monitors that employed event recordings were effective in identifying episodes dangerous to infant health
• Determine the conditions that optimized the use of apnea monitors in high-risk infants
• Correlate physiological markers, health status, and behavior with the propensity for lifethreatening events
• Provide important information on the maturation of heart and respiratory functions in sleeping infants

The PPB, CHIME investigators, and industry collaborated in the development of a new monitoring technology, which was being tested for its potential to detect and record life-threatening cardiorespiratory episodes. The technology incorporated new, advanced computer capabilities, inductance plethysmography, electrocardiogram (ECG), pulse oximetry, and an accelerometer to detect motion and infant position. In addition to event recording, which captured the physiology for a period before, during, and post-event, monitors were programmed to store continuous R-R intervals from the ECG, continuous breath-breath intervals, and normative three-minute epochs at hourly intervals.

One analysis of these data showed that 80 percent of the apneas that the CHIME monitor identified as obstructed were supported by either nasal end-tidal carbon dioxide measurements, or nasal/oral thermistor measurements (American Journal of Respiratory and Critical Care Medicine 2000; 162:471-480). Therefore, with the new home-monitoring technology to measure obstructed breaths, the longitudinal monitoring records collected during sleep periods in the CHIME study provide an opportunity to analyze physiological events not previously recorded in the home.

A major analysis of CHIME data showed that cardiorespiratory events (i.e., apnea and bradycardia) that met conventional alarm thresholds were quite common, even in healthy term infants (JAMA 2001; 285:2199-2207). More severe events were common only in preterm infants, and their timing suggested that they were not likely immediate precursors to SIDS. In addition, the data suggested that conventional monitoring techniques would likely miss most of the cardiorespiratory events detected in the study subjects because the events had a high frequency of obstructed breathing. The AAP Committee on Fetus and Newborn used this information in drafting its policy statement, Apnea, Sudden Infant Death Syndrome, and Home Monitoring (Pediatrics 2003; 111:914-917). In addition, analyses of the CHIME Study data have been used to develop scoring algorithms for cardiorespiratory recordings and polysomnograms. An Atlas of Infant Polysomnography was published by CHIME Study investigators and is a valuable resource for researchers and clinicians.

The CHIME database, which includes all raw physiological records and study forms was recently transferred to CD-ROM; in January 2004, the entire database became accessible to researchers at http://dccwww.bumc.bu.edu/ChimeNisp/.

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