Examination of changes in the breathing intolerance index to determine the respiratory support needs of very low birth weight infants.

BACKGROUND: The breathing intolerance index (BITI) is used to evaluate respiratory muscle tolerance. The higher the ratio of the inspiratory time to the total breathing time and the ratio of the tidal volume to the vital capacity, the more easily the respiratory muscles become fatigued. The BITI is high with chronic respiratory failure, and values of 0.15 or more indicate the need for assisted ventilation. OBJECTIVE: This study aimed to examine the changes in the BITI of very low birth weight infants (VLBWIs) and determine whether it is possible to use the BITI as an objective indicator of the timing of noninvasive respiratory support (NRS) withdrawal. METHODS: VLBWIs admitted to our neonatal intensive care unit between July 2020 and July 2022 under NRS at 36 weeks' postmenstrual age (PMA). If the BITI was less than 0.15, then we attempted to determine whether NRS could be withdrawn. RESULTS: Sixteen infants with a median gestational age and birth weight of 30.9 weeks and 1249 g, respectively, were eligible. The median PMA at the time of the first examination was 36.6 weeks. The BITI of two VLBWIs was less than 0.15. For 11 of the other VLBWIs, the BITI decreased over time to less than 0.15 at 39 weeks' PMA. After confirming that the BITI was less than 0.15, weaning from NRS was attempted. Weaning from NRS was possible except one VLBWI. CONCLUSION: The BITI can help evaluate respiratory tolerance and could be an objective indicator of the timing of NRS withdrawal.

Surfactant therapy using a bronchofiberscope in respiratory distress syndrome.

BACKGROUND: Avoiding endotracheal intubation and using nasal continuous positive airway pressure as the initial treatment is recommended in infants with respiratory distress syndrome (RDS), and modes of lesser invasive surfactant administration have recently been reported. We report a pilot study assessing the feasibility of surfactant therapy using a bronchofiberscope (STUB) in RDS. METHODS: Surfactant was administered to 31 preterm infants (gestational age range of 28 weeks 0 days to 36 weeks 6 days) diagnosed with RDS, through the working channel of the bronchofiberscope or endotracheal tubes. Patient characteristics, outcomes, adverse events, and comorbidities were assessed in the two groups. RESULTS: Twelve infants received STUB. Two of the 12 infants (17%) needed subsequent intubation and additional surfactant administration. Nineteen infants received surfactant through endotracheal tubes. Four of the 19 infants (21%) required additional surfactants. There was no significant difference in the number of infants that needed additional surfactant (p = 1.00). Gestational age, birthweight, length of hospitalization, adverse events, such as desaturations and bradycardias, and comorbidities were similar between the two groups. Days of invasive ventilation were significantly shorter in the STUB group (p = 0.0002). CONCLUSION: STUB was feasible in this small cohort and reduced the need for intubation to 17%, leading to fewer days of invasive ventilation, without increasing comorbidities and adverse events. To the best of our knowledge, this is the first study to administer surfactants using bronchofiberscopes.

Pharyngomalacia diagnosed by laryngo-tracheo-bronchoscopy in the neonatal intensive care unit.

BACKGROUND: Flexible fiber-optic laryngo-tracheo-bronchoscopy has become widely performed in infants and neonates since the introduction of thin flexible fiberscopes. Laryngomalacia is the most common airway disease in infants causing stridor. Pharyngomalacia, termed pharyngeal occlusion during inspiration, was the second most common airway disease found in our hospital in patients that underwent laryngo-tracheo-bronchoscopy, but the incidence, patient characteristics, and natural course have not been reported in large numbers in Japan. METHODS: A retrospective review was performed of medical records on patients admitted to our neonatal intensive care unit during the neonatal period diagnosed with pharyngomalacia between April 2009 and November 2018. Patient characteristics, concurrent airway diseases, comorbidities, and treatment were reviewed. RESULTS: Forty-eight patients were diagnosed with pharyngomalacia. The median gestational age was 37.1 weeks, and the median birthweight was 2,552 g. Patients were diagnosed at a median age of 29 days, and cure was achieved at a median age of 4 months. Twenty-eight patients had concurrent airway diseases, laryngomalacia being the most common. Continuous positive airway pressure or high flow nasal cannula was used in 34 patients. CONCLUSIONS: In patients with pharyngomalacia, half were born preterm, and more than half had concurrent airway diseases. The onset and diagnosis were made within the first month of life in more than half of the patients, and resolution was seen mostly within the first 6 months of life. Whenever a patient is suspected of having an airway disease, the pharyngeal space should be carefully observed to diagnose pharyngomalacia.

Videoendoscopic evaluation of swallowing using normal saline in NICU infants.

BACKGROUND: Videoendoscopic evaluation (VE) of swallowing involves inserting a small flexible endoscope transnasally to allow direct observation of pharyngeal and laryngeal structures and swallowing functions. In our neonatal intensive care unit (NICU) VE is performed in infants suspected of severe swallowing dysfunction, using normal saline (NS) with the aim of minimizing the detrimental effect of aspiration on respiration caused by VE. This retrospective study was conducted to evaluate the usefulness of VE using NS in NICU infants. METHODS: We enrolled 28 infants who demonstrated clinical signs of swallowing dysfunction or who were ready to start oral feeding. Swallowing evaluations were completed using flexible fiberoptic laryngobronchoscopy (FLB). While observing the pharyngeal and laryngeal cavity with FLB, NS was gradually increased by 1 mL and injected up to a maximum of 3 mL, and the swallowing reflex, tracheal aspiration, and pharyngeal residue were observed. RESULTS: Median gestational age was 37 weeks 6 days, median birthweight 2,539 g, and median age at first examination was 107.5 days. Abnormalities in VE were observed in 20 cases, most of which were upper airway lesions. Most of these upper airway abnormalities were pharyngeal lesions. In two pharyngeal lesion cases, swallowing function improved using positive airway pressure. CONCLUSIONS: Infants with pharyngeal lesions demonstrated abnormal VE findings. Furthermore, positive airway pressure improved swallowing in some cases, suggesting that narrowing of the pharyngeal cavity may affect swallowing function. In addition, results suggest that VE using NS is a safe and useful method for evaluating swallowing function and determining countermeasures in NICU infants.

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.

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.