Study design and population
Among 824 infants consecutively admitted for bronchiolitis to the Pediatric Emergency Department “Sapienza” University of Rome from 2012 to 2019, we have retrospectively reviewed clinical charts of the 130 infants who received oxygen by HFNC. Bronchiolitis was defined as the first acute lower respiratory tract infection characterized by respiratory distress with tachypnea, cough, retractions and diffuse crackles on auscultation, in full term babies less than 12 months of age [8]. Infants with prematurity, cardiopulmonary disorders, immunodeficiency or congenital anomalies were excluded. Demographical, clinical and laboratory data such as age, gender, breastfeeding, cigarette smoking exposure, body weight, gestational age, days of illness, length of hospital stay and low flow oxygen therapy before HFNC, were systematically collected from clinical charts. On hospital admission and just before starting HFNC, a clinical severity score (from 0 to 8) was assigned to each infant according to respiratory rate, oxygen saturation in room air, presence of retractions and ability to feed [9].
According to our internal protocol, patients underwent HFNC for the following clinical indications: presence of severe retractions and/or nasal flaring associated to respiratory rate higher than 70 breaths per minute and heart rate higher than 150 beats per minute and/or oxygen saturation lower than 92%. HFNC was started with a weight-based gas flow rate, starting with 1L/Kg/min. After 15 minutes, physicians performed a clinical evaluation and if necessary gas flow was titrated up to 2 L/Kg and FiO2 adjusted to target SaO2 (over 92%). A second clinical evaluation was performed after 60 minutes and then every 3 hours over the next 24 hours. In case of progressive respiratory distress and inability to keep SaO2 over 92% with a FiO2 60%, patients were admitted to PICU where mechanical ventilation was started.
The study protocol was approved by Policlinico Umberto I ethic committee (Rif. CE 2377/2012).