Ventilatory response to CO2 with Read's rebreathing method in normal infants.

BACKGROUND: Methods of evaluating the ventilatory response to CO2 (VRCO2 ) of the respiratory center include the steady-state and the rebreathing method. Although the rebreathing method can evaluate the ventilatory response continuously to gradually increasing CO2 , the rebreathing method has been rarely performed in infants. The aim of this study was to investigate whether we could perform the VRCO2 with the rebreathing method in normal infants. METHODS: The subjects were 80 normal infants. The gestational age was 39.9 (39.3-40.3) weeks, and the birth body weight was 3142 (2851-3451) grams. We performed the VRCO2 with Read's rebreathing method, measuring the increase in minute volume (MV) in response to the increase in EtCO2 by rebreathing a closed circuit. The value of VRCO2 was calculated as follow: VRCO2 (ml/min/mmHg/kg) = ΔMV/ΔEtCO2 /body weight. RESULTS: We performed the examination without adverse events. The age in days at examination was 3 (2-4), and the examination time was 150 ± 38 s. The maximum EtCO2 was 51.1 (50.5-51.9) mmHg. The value of VRCO2 was 34.6 (29.3-42.8). The intraclass correlation coefficient of the VRCO2 of cases with multiple measurements was 0.79. CONCLUSION: This study suggests that the rebreathing method can evaluate the ventilatory response to high blood CO2 in a short examination time. We conclude that the rebreathing method is useful even in infants. In the future, we plan to measure the VRCO2 of preterm infants, and evaluate the respiratory center of infants in more detail.

Evaluation of respiratory center function in congenital central hypoventilation syndrome by monitoring electrical activity of the diaphragm.

BACKGROUND: A definitive diagnosis of congenital central hypoventilation syndrome (CCHS) is made by genetic testing. However, there are only a few examinations that warrant genetic testing. Electrical activity of the diaphragm (Edi) reflects neural respiratory drive from respiratory center to diaphragm. We evaluated the function of the respiratory center in CCHS by Edi monitoring. METHODS: Monitoring of Edi was performed in six CCHS cases without mechanical ventilation. The monitoring time was 30 consecutive minutes from wakefulness to sleep. The TcPCO2 or EtCO2 and SpO2 were recorded simultaneously. RESULTS: The Edi peak during wakefulness was 14.0 (10.3-21.0) µV and the Edi peak during sleep was 6.7 (3.8-8.0) µV. The Edi peak during sleep was significantly lower than the Edi peak during wakefulness, and patients were in a state of hypoventilation. Although TcPCO2 or EtCO2 increased due to hypoventilation, an increase in the Edi peak that reflects central respiratory drive was not observed. ΔEdi/ΔCO2 was -0.06µV/mmHg. Maximum EtCO2 or TcPco2 was 51 mmHg, and the average SpO2 was 91.5% during monitoring. CONCLUSIONS: We confirmed that Edi monitoring could evaluate the function of the respiratory center and reproduce the hypoventilation of CCHS. The present study suggested that Edi monitoring is a useful examination in deciding whether to perform genetic testing or not and it may lead to an early diagnosis of CCHS.

Is the neonatal creatine phosphokinase level a reliable marker for fetal hypoxia?

AIM: The creatine phosphokinase (CPK) level is believed to increase in neonatal peripheral blood after tissue damage, including damage from perinatal hypoxia. However, it is not clear whether it is truly a reliable marker for fetal hypoxia. We investigated the chronological changes in neonatal CPK and the reliability of CPK as a marker for fetal hypoxia. METHODS: Sixty term neonates admitted to the neonatal intensive care unit at Tokyo Women's Medical University Medical Center East from April 2009 to April 2010 were enrolled in this study. We evaluated whether asphyxia and fetal heart rate (FHR) abnormality could predict the neonatal CPK level by using receiver-operator curve analysis. We also compared umbilical cord blood pH levels with neonatal CPK levels. In addition, we investigated factors that influence neonatal CPK in non-asphyxia cases. RESULTS: The median value of CPK peaked on day 1. There were no significant differences in CPK levels regardless of the presence of asphyxia or FHR abnormality. Non-asphyxiated neonates with older gestational ages and amniotic fluid abnormalities had significantly higher levels of CPK. CONCLUSION: Our results indicate that the neonatal CPK level is not an appropriate marker for retrospectively predicting either asphyxia or FHR abnormality. There are influencing factors other than asphyxia that increase neonatal CPK. Therefore, one should be careful when making a diagnosis of perinatal hypoxia based solely on increased levels of neonatal CPK after birth.

A case of cervical esophageal duplication cyst in a newborn infant.

Esophageal duplication cyst is a rare congenital anomaly resulting from a foregut budding error during the fourth to sixth week of embryonic development. Cervical esophageal duplication cysts are very rare and may cause respiratory distress in infancy. A full-term newborn girl who was born by normal delivery was transferred to our hospital because of swelling of the right anterior neck since birth. Cervical ultrasonography showed a 40 × 24 × 33 mm simple cyst on the right neck. Tracheal intubation was required at 2 weeks of age because of worsening external compression of the trachea. Fine-needle aspiration cytology revealed the existence of ciliated epithelium. At 1 month of age, exploration was performed through a transverse neck incision. The cyst had a layer of muscle connected to the lateral wall of the esophagus. Histopathological diagnosis was a cervical esophageal duplication cyst. We describe the clinical features of infantile cervical esophageal duplication cysts based on our experience of this rare disease in a neonate, along with a review of 19 cases previously reported in literature.

Tracheoplasty using the thymus against tracheo-esophageal fistula due to necrotizing tracheobronchitis in a very low birth weight infant.

We report a case of a very low birth weight infant treated successfully with tracheoplasty using the thymus against tracheo-esophageal fistula due to necrotizing tracheobronchitis. A baby boy was born at 31 weeks gestation with a birth body weight of 1,230 g. Suddenly on Day 19, his respiration deteriorated, and a flexible bronchofiberscopy showed tracheostenosis, tracheomalacia, and tracheal diverticula. On Day 21, his abdomen became significantly distended, and a flexible bronchofiberscopy showed a tracheo-esophageal fistula due to a rupture of the diverticula. On Day 105, during surgery, we confirmed necrosis of the trachea. Because the lesion was widespread, we used the thymus for tracheoplasty and closure of the tracheo-esophageal fistula. His post-operative course went well, and was discharged at 1 year 9 months of age. Now, 8 years after the operation, although he still needs a T-tube airway management through tracheostomy, he has achieved speech, normal growth and development, and takes regular classes at school. Tracheoplasty using the thymus is thought to be a treatment worth considering when there are no other effective alternative treatments for tracheo-esophageal fistula due to necrotizing tracheobronchitis.

Breathing intolerance index in healthy infants.

BACKGROUND: The breathing intolerance index (BITI) is used to justify ventilator use in adult patients with pulmonary or chest wall disease. BITI in ventilated patients is mostly ≥0.15. The mean BITI of healthy adults in the upright sitting position and the supine position is 0.050 ± 0.009 and 0.057 ± 0.016, respectively. The aim of this study was to establish a normal BITI in infants. METHODS: Thirty healthy infants were examined in the supine position. BITI was defined as BITI = (Ti/Ttot) × (TV/VC), where Ti is inspiratory time, Ttot is total breath cycle duration, TV is tidal volume, and VC is vital capacity. TV and Ti/Ttot were obtained from tidal breathing at rest and VC was obtained spirometrically. BITI was calculated using customized software. RESULTS: The mean ± SD BITI of 30 healthy infants in the supine position was 0.120 ± 0.013. The BITI of infants was significantly higher than that of adults. CONCLUSIONS: BITI was measured in healthy infants. Further evaluation is needed to determine the significance and usefulness of BITI.