The prognosis of infants with neonatal respiratory inhibition syndrome.

OBJECTIVE: The goal of this study was to investigate the prognosis of infants with neonatal respiratory inhibition syndrome (NRIS).

METHODS: Infants with a gestational age of at least 36 weeks and a birth weight of at least 2000 g who were born at Nara Prefecture General Medical Center, in Nara, Japan, between March 2013 and June 2016 were screened for NRIS using our established method. NRIS was defined as severe hypoxemia caused by respiratory inhibition immediately after crying (RIAC) or gastroesophageal reflux (RIGER) or as a respiratory pause during feeding (feeding hypoxemia), accompanied clinically by central cyanosis and a decrease in SpO2 to less than 70%. All infants were monitored using pulse oximetry immediately after birth. Diagnosis of RIAC, feeding hypoxemia, and RIGER are based on observation by both parents and medical staff as well as on on-screen computer analysis using specific software. All infants were examined at a one-month check-up. Parents of the infants who experienced one or more episodes of NRIS accompanied by a decrease in SpO2 to less than 70% for more than approximately 60 s received a questionnaire by mail about their child's development. We conducted a logistic regression analysis with developmental problems as the dependent variable.

RESULTS: NRIS was observed in 362 (28.5%) infants; 216 (17.0%) infants showed RIAC, 254 (20.0%) infants showed feeding hypoxemia, and 54 (4.2%) infants showed RIGER. Although all infants were monitored in the maternity ward nursery, 184 (85.2%) infants with RIAC and 111 (43.7%) infants with feeding hypoxemia were overlooked. All infants with NRIS were found to have successfully recovered at one month after birth. Sixty-two cases were examined in the follow-up study by the mailed questionnaire. The median age of the subjects at time of study was 22 months. Fourteen cases (22.6%) exhibited developmental problems including delayed speech development, stereotyped interests and behaviors, sensory disturbance, hyperactivity, delayed motor development, and short stature. Developmental problems tended to relate to shorter gestational age (odds ratio, 0.622; p = .068; 95% CI, 0.373-1.036), smaller birth weight (odds ratio, 0.998; p = .069; 95% CI, 0.997-1.000), and maximum duration of SpO2 to less than 70% by RIAC (odds ratio, 1.009; p = .086; 95% CI, 0.999-1.020). All cases had experienced severe hypoxemia accompanied by a decrease in SpO2 to less than 60%. Seven cases had experienced prolonged hypoxemia accompanied by a decrease in SpO2 to less than 70% for at least 2 min. Among the subjects, 19 infants were examined closely, and their natural course of NRIS was observed in the neonatal intensive care unit. No cases demonstrated abnormal findings with blood examinations, chest-abdominal X-ray, echocardiogram, laryngoendoscopy, hearing loss screening, or mass screening. Only one case had a small intracranial hemorrhage as evidenced in a magnetic resonance imaging of the head.

CONCLUSIONS: The infants with severe NRIS tended to have developmental problems. Spreading knowledge about NRIS worldwide is thought to be very important.