ABNORMALITIES IN CONTROL OF VENTILATION IN NEWBORN-INFANTS WITH MYELOMENINGOCELE

Objective: The objective of this study was to assess respiratory respo nses of newborn infants with myelomeningocele through pneumograms and carbon dioxide challenge, and to evaluate the possibility of predictin g which patients with myelomeningocele acquired respiratory symptoms r elated to the Arnold-Chiari deformity and brain-stem dysfunction. Meth ods: All surviving infants with spina bifida who were born at the Univ ersity of lowa Hospitals and Clinics (UIHC) or were transferred there on the first day of life between January 1987 and January 1991 were as sessed with a pneumogram and CO2 challenge once they were medically st able, and were followed for a mean of 30 months (10 to 53 months). Res ults: Thirty patients met the inclusion criteria for this study; four died before being studied. Of the 26 remaining patients, 12 were born at the UIHC and 14 were transferred to the UIHC on the first day of li fe. Of the 26 infants studied, 12 (46%) had abnormalities on the pneum ogram including 2 with significant periodic breathing and 10 with epis odes of desaturation below 87%. Of the 26 infants studied, 4 had no de tectable response to an increasing fraction of CO2 in inspired air on the CO2 challenge and 12 had an increase in exhaled minute ventilation per increase in the alveolar fraction of CO2 in exhaled air more than 2 SD below the mean. Only 10 patients (38.5%) had normal ventilatory responses to the increasing fraction of CO2 in inspired air. On follow -up, only one study patient had symptoms related to Arnold-Chiari defo rmity and brain-stem dysfunction (bilateral vocal cord paralysis). His neonatal CO2 challenge results and his pneumogram were normal. Conclu sion: We conclude that these two tests are not useful in predicting wh ich patients wilt have symptoms related to Arnold-Chiari deformity, Sp ecificity for the pneumogram and the CO2 challenge was 0.52 and 0.36, respectively. Sensitivity was zero for both tests, although this resul t is limited by the low incidence of symptomatic Arnold-Chiari deformi ty in this sample. As previous investigators have found, a significant number of patients with meningomyelocele had abnormal ventilatory pat terns. These ventilatory abnormalities indicate that even in the absen ce of severe symptoms, the control of the ventilatory response is some what impaired in many patients with meningomyelocele. This alteration in ventilatory control is probably related to abnormalities in the dev elopment of the brain stem.