448 - Do infants exhale through their CPAP system?

Poster Number: 448
Publication Number: 448.228

Kolbrun Gunnarsdottir, Karolinska Institutet, Sundbyberg, Stockholms Lan, Sweden; Markus Falk, Karolinska Institutet, Frösön, Jamtlands Lan, Sweden; Sonja Baldursdottir, Karolinska Institutet, Stockholm, Stockholms Lan, Sweden; Snorri Donaldsson, Karolinska/University Hospital of Iceland, Garðabær, Hofuoborgarsvaoio, Iceland; Thomas Drevhammar, Karolinska Institutet, Stockholm, Stockholms Lan, Sweden; Baldvin Jonsson, Karolinska Institutet, Stockholm, Stockholms Lan, Sweden

Background: During nasal Continous Positive Airway Pressure (nCPAP) treatment, leakage at the interface level is almost inevitable and can lead to reduced distending pressure in the lungs of the infant. Current practice measures neither leakage nor expiratory flow making it difficult to know if expiration is through the device or entirely through leakage.

Objective: To examine if infants treated with continuous positive airway pressure (CPAP) expire through the CPAP system.

Design/Methods: Secondary data analyses from the ToNIL trial on leakage during nasal CPAP treatment. We retrospectively examined respiratory curves for 50 infants, each measured with two different nasal interfaces. Measurements were done for at least 30 seconds during calm breathing. Exhalation through the CPAP system was not specified as an outcome in the ToNIL trial. 50 infants were studied, mean GA (gestational age) at birth 34 weeks, median birth weight of 1948 g (IQR 1517-3442), and mean age at measurement 6.5 days. Patients were recruited from two hospitals (Karolinska University Hospital and Östersund Hospital). Inclusion criteria were CPAP treatment and a PMA (postmenstrual age) of 28-42 weeks. Informed parental consent was obtained prior to inclusion.

Results: Exhalation of at least half of the breaths through the CPAP system was seen in 32/50 (64%) infants in one or both recordings, 18/50 did not exhale through the system. There were no significant differences in GA, weight, or CPAP level between the neonates who exhaled through the CPAP system and those who did not.Conclusion(s): Exhalation through the CPAP system was common and variation of leakage was large.This emphasizes the importance of expiratory resistance when designing new systems. To our knowledge, this has not previously been described.