RESUMEN
OBJECTIVES: (1) To evaluate the Graseby capsule (GC) as a respiratory detection device when compared to respiratory inductance plethysmography (RIP); (2) to evaluate the response to the Graseby signal of a commercially available bi-level nasal CPAP device (BNCPAP) designed for use with the GC; and (3) to assess the performance of the GC/BNCPAP device when fitted on preterm infants. STUDY DESIGN: The study consisted of four parts: (1) The response characteristics of the GC/BNCPAP were assessed without connection to an infant; (2) the respiratory detection of both GC and RIP were compared in six preterm infants (mean 1,242 g, range 900-1,530 g); (3) the GC/BNCPAP was connected in six preterm infants (mean 1,568 g, range 1,040-1,835 g), isolating the BNCPAP and the infant interaction by substituting an artificial "nose" for the infant and assessing performance using inspiratory times (Ti) of 0.1 through 0.5 sec with pressure levels of both 10/6 and 8/5 cmH2 O; and (4) the GC/BNCPAP was employed as a respiratory support device in six preterm infants (mean 1,189 g, range 785-1,795 g) using clinically required pressures and evaluating performance using Ti of 0.3, 0.4 and 0.5 sec. RESULTS: (1) Within 26 ms of stimulation of the GC, the BNCPAP initiated air flow; however, the time to reach peak pressure was much longer; (2) the GC, when placed in the subxiphoid position, tracked the RIP signal nearly identically and occurred sooner; (3) a Ti of at least 0.3 sec was required to reach the desired high pressure setting; and (4) synchrony of the GC/BNCPAP occurred in 72-74% of infant breaths. CONCLUSIONS: The GC is a sensitive respiratory detection device; however, the GC/BNCPAP interface requires a minimum Ti of 0.3 sec and an adequate respiratory effort to achieve the desired pressure and to synchronously trigger the BNCPAP.