Yi-Ming Hua

Comparison between Bubble CPAP and Ventilator-derived CPAP in Rabbits

BACKGROUND Continuous positive airway pressure (CPAP) is used in infants with respiratory distress and apnea. Bubble CPAP (B-CPAP) and ventilator-derived CPAP (V-CPAP) are two of the most popular CPAP modes, and use different pressure sources. However, few studies have been performed to compare their differences and effectiveness. This study was to determine whether B-CPAP and V-CPAP would have different effects on vital signs and arterial blood gas analysis. METHODS We performed a randomized crossover study to measure vital signs, including mean blood pressure (MBP), heart rate (HR), and respiratory rate (RR), in 12 ketamine-anesthetized healthy rabbits receiving endotracheal intubation by tracheostomy with B-CPAP or V-CPAP. Arterial blood was also sampled and analyzed for PaO2, PaCO2, HCO3 and pH. RESULTS We observed statistically significant decreases in RR, pH and PaO2 with corresponding incrases in PaCO2 and HCO3 during the V-CPAP; however, no significant changes from baseline were observed for B-CPAP. Neither modality resulted in statistically significant changes in MBP or HR. Both forms of CPAP altered vital signs and arterial blood gases in a similar manner. There was a trend towards a lower percentage of change from baseline in all variables in B-CPAP compared with V-CPAP. CONCLUSIONS Our results suggest that B-CPAP seems to be superior to V-CPAP in terms of its effect on arterial blood gases and vital signs. We speculate that B-CPAP could have certain protective effects that better preserve both arterial blood gases and vital signs when compared to V-CPAP. However, the results of this study still need to be tested by clinical study.

Endogenous nitric oxide in the nasal airways of healthy term newborn infants in Taiwan.

BACKGROUND Nitric oxide (NO) in the respiratory tract is an important regulator of pulmonary homeostasis during the perinatal transition. In humans, much of the nitric oxide is derived from the upper airways, and autoinhalation of nasal NO has been suggested to influence pulmonary function. No standard methods for measuring nasal NO in neonates currently exist, and previous studies have reported varying levels of nasal nitric oxide in infants, due to the different measuring methods used. The use of nasal olives with a central lumen placed securely in the nares was recommended as a standardized procedure for the measurement of nasal NO in adults and children in 1999. We attempted to establish a safe, convenient and practical method for measuring nasal NO in healthy newborn infants, and investigated possible correlations between nasal NO and gender, postnatal age, gestational age, birth weight, and the differences between the right and left nostrils. METHODS Nasal NO was studied in healthy newborn infants within the first 3 postnatal days. Gas was sampled from the nostril, and NO concentrations were determined using a fast response chemiluminescence analyzer. Each newborn infant underwent NO measurements on the first, second and the third postnatal days. Ninety-one newborn infants completed the study. RESULTS Peak nasal NO in 91 newborn infants was 42.52 +/- 16.82 (mean +/- SD) parts per billion (ppb) (right nostril) and 40.86 +/- 16.08 ppb (left nostril) on the first postnatal day, 48.75 +/- 17.64 ppb (right nostril) and 49.47 +/- 17.26 ppb (left nostril) on the second postnatal day, and 59.65 +/- 19.72 ppb (right nostril) and 59.29 +/- 20.09 ppb (left nostril) on the third postnatal day. Nasal NO increased significantly with postnatal age (p < 0.001). There were no significant differences in nasal nitric oxide between sexes, or in relation to gestational age or birth weight, or between left or right nostrils. CONCLUSION We conclude that nasal NO increased significantly in the first 3 days of life.

Nasal nitric oxide in infants before and after extubation.

The endogenous production of nitric oxide (NO) in the upper airways is known to be high, but reports of the exact level vary, especially in newborn infants. Currently there is still no standard methodology for nasal NO measurements in neonates. In this study, we compared the levels of NO from the nasal cavity, and from the lower respiratory tracts in intubated infants together with the differences in nasal NO before and after extubation. A total of 35 intubated infants were enrolled in the study. The sampling was conducted with a fast-response chemoluminescence analyzer using the on-line tidal breathing techniques. The levels of NO in the nasal cavity were sampled using two different methods, namely nasal catheterization (Group 1), and nasal occlusion (Group 2). In both groups, the NO levels in the nasal cavity were found to be significantly higher than in the lower airway (P < 0.001). After extubation, the concentration of nasal NO in Group 1 was found to be significantly lower than before extubation (P < 0.05). There was no difference found between the levels of nasal NO in Group 2 before and after extubation (P = 0.95). Generally speaking, the concentrations of nasal NO in Group 2 were significantly higher than in Group 1 after extubation (P < 0.05). For the sample that used nasal occlusion, the nasal NO levels were more stable before and after extubation and the concentration was not affected by the breathing pattern or crying. The infants were more comfortable as well. We therefore conclude that nasal occlusion is a better method for measuring the levels of nasal NO in infants and neonates.

A decremental PEEP trial for determining open-lung PEEP in a rabbit model of acute lung injury†

A positive end‐expiratory pressure (PEEP) above the lower inflection point (LIP) of the pressure–volume curve has been thought necessary to maintain recruited lung volume in acute lung injury (ALI). We used a strategy to identify the level of open‐lung PEEP (OLP) by detecting the maximum tidal compliance during a decremental PEEP trial (DPT). We performed a randomized controlled study to compare the effect of the OLP to PEEP above LIP and zero PEEP on pulmonary mechanics, gas exchange, hemodynamic change, and lung injury in 26 rabbits with ALI. After recruitment maneuver, the lavage‐injured rabbits received DPTs to identify the OLP. Animals were randomized to receive volume controlled ventilation with either: (a) PEEP = 0 cm H2O (ZEEP); (b) PEEP = 2 cm H2O above OLP (OLP + 2); or (c) PEEP = 2 cm H2O above LIP (LIP + 2). Peak inspiratory pressure and mean airway pressure were recorded and arterial blood gases were analyzed every 30 min. Mean blood pressure and heart rate were monitored continuously. Lung injury severity was assessed by lung wet/dry weight ratio. Animals in OLP + 2 group had less lung injury as well as relatively better compliance, more stable pH, and less hypercapnia compared to the LIP + 2 and ZEEP groups. We concluded that setting PEEP according to the OLP identified by DPTs is an effective method to attenuate lung injury. This strategy could be used as an indicator for optimal PEEP. The approach is simple and noninvasive and may be of clinical interest. Pediatr Pulmonol. 2008; 43:371–380.

Influence of Changing the Diameter of the Bubble Generator Bottle and Expiratory Limb on Bubble CPAP: An in vitro Study

BACKGROUND The noisy component of bubble continuous positive airway pressure (CPAP) is thought to contribute to breathing efficiency and lung volume recruitment, mainly because of stochastic resonance. The magnitude and frequency of the superimposed noise are vital to this process. We wanted to evaluate the in vitro effect of changing various parameters of the bubble CPAP circuit regarding the magnitude and frequency of pressure oscillations transmitted to the lung model. METHODS In a bubble CPAP lung model, we immersed different sizes (3.0∼12.5 mm) of the expiratory limb of the CPAP circuit into different depths under water (2.0∼10.0 cm) and used various diameters (2.9∼9.0 cm) of bubble generator bottles. We also varied the compliance of the model lung. We measured the changes in mean, magnitude, and frequency of pressure oscillations transmitted to the lung model at three different flow rates (namely 4, 8, and 12L/minute). RESULTS Increasing the size and submergence depth of the expiratory limb of a CPAP circuit and decreasing the diameter of the bubble generator bottle intensified the magnitude but diminished the frequency of noise transmitted to the lung model. Decreasing compliance of the lung model intensified both the magnitude and frequency content of pressure oscillations in the model lung. CONCLUSION The size and submergence depth of an expiratory limb of a CPAP circuit, the diameter of the bubble generator bottle, and the compliance of the model lung all influence the magnitude and frequency of the transmitted pressure waveform. Therefore, these factors may affect lung volume recruitment and breathing efficiency in bubble CPAP.

The occurrence rate and correlation factors of thumb-in-palm posture in newborns

Bilateral fisting of hands, including adduction and infolding of the thumbs (cortical thumbs), is an expected finding in term infants. Clinically, the cortical thumb position is a transient and normal, but not general, hand posture in newborns. The aim of this study was to analyze the rate of occurrence and the factors possibly affecting the cortical thumb (thumb-in-palm) posture in term newborns. We enrolled 197 low-risk term newborns and observed the posture of their hands once daily from the day of birth for 3 consecutive days. The occurrence rates of the thumb-in-palm posture of the right hand on the first, second, and third days were 62.8%, 60.9%, and 50%, respectively, and those of the left hand were 60.3%, 55.8% and 53.2%, respectively. There was a significant reduction on a day-to-day basis in the right hand and an insignificant reduction in that of the left hand. Factors including sex, gestation age, birth weight, method of delivery, and alertness were analyzed, and no relationship was evident between these factors and the occurrence rates of the cortical thumb posture. Our observations suggest that the cortical thumb posture is indeed a predominant hand posture in our hospital, yet it is not a general phenomenon in all term newborns.

Reevaluating reference ranges of oxygen saturation for healthy full-term neonates using pulse oximetry.

BACKGROUND We compared our clinical experience with currently available reference oxygen saturation level (SpO(2)) values from the American Academy of Pediatrics/American Heart Association (AAP/AHA) neonatal resuscitation program guidelines. METHODS We enrolled 145 healthy full-term neonates; infants showing respiratory distress and those with serious congenital anomalies were excluded. SpO(2) values at every 1 minute until 10 minutes after birth were measured and recorded. Infants were classified into the cesarean section (CS) and normal spontaneous delivery (NSD) groups for evaluating differences. The 10(th) percentiles of SpO(2) at each minute were used as the lower limits of normal oxygen saturation, and these were compared with the lowest target values recommended in the AAP/AHA guidelines. RESULTS Overall, 130 vigorous full-term neonates (median gestational age: 38 5/7 weeks; body weight at birth: 2405-3960 g) were analyzed. The median SpO(2) were 67% and 89% at the 1(st) and 4(th) minute, respectively. On average, SpO(2) values reached >90% at the 5(th) minute. No statistical differences were noted in the SpO(2) values between the CS and NSD groups after 5 minutes; however, a trend of higher SpO(2) was observed in the NSD group. We noted a gradually increasing trend for SpO(2) values over time, similar to that noted in the AAP/AHA guidelines. However, SpO(2) values at the 10(th) percentiles of each minute within the first 5 minutes in our study were equal to or significantly lower than those in the AAP/AHA guidelines; moreover, at the 10(th) minute, SpO(2) values at the 10(th) percentiles were significantly higher than those in the guidelines. CONCLUSION The delivery modes did not affect the SpO(2) values of full-term healthy neonates. Discrepancies in SpO(2) changes in full-term neonates not requiring resuscitation between this study and the AAP/AHA guidelines were significant. SpO(2) ranges for each time point within the first 10 minutes after birth should therefore be reevaluated locally.

Influence of ventilatory settings on exhaled nitric oxide during high frequency oscillatory ventilation

Nitric oxide (NO), which is produced in the lower airways, diffuses from cells into the air space and can be measured in exhaled air. The influence of high frequency oscillatory ventilation on the production of exhaled NO (eNO) has not been thoroughly studied. The objectives of this study are to establish an animal model for evaluation of lower airway NO and to evaluate settings in terms of frequency, mean airway pressure (MAP), amplitude pressure (amplitude), and inspiratory time ratio (tI/tE) during high frequency oscillatory ventilation on the production of eNO. An observational animal study was performed on 12 female New Zealand White rabbits, which were anesthetized, tracheotomized and ventilated using a SensorMedics 3100A HFOV ventilator (SM3100A). The concentration of NO in exhaled gas was measured by chemiluminescence continuously from the nose and the side hole of the adaptor of endotracheal tube. The individual effects of the respiratory settings were evaluated. The results were analyzed by paired t‐test or by the generalized estimating equation method. We found that the lower airway was the main source of the eNO, that amplitude, MAP, and tI/tE were positively correlated with the level of eNO and that frequency was negatively correlated with the level of eNO. These findings fit the stretch theory for the production of endogenous NO. Monitoring of eNO during HFOV may provide insights into lung mechanics and ventilation efficiency and be used in the future as a guide during clinical practice. Pediatr Pulmonol. 2009; 44:800–805.

Renal abscess : Report of two cases

Renal abscess, a very uncommon renal disease in the pediatric patient is often complicated by irrelevant antibiotics treated urinary tract infection or due to other unknown reasons. In this paper, two cases of renal abscess were reported though they had been treated with antibiotics. The diagnosis had been made soon by sonography and computed tomography (CT). In addition, during the period of treatment, a series of sonography were performed to monitor resolution of abscess. In one, the lesion was resolved by antibiotics alone for 2 months duration, the other nearly disappeared 3 weeks later after antibiotics treatment combined with tube-drainage. These imaging techniques permit a prompt diagnosis as well as percutaneous drainage performed if antibiotic treatment dose not lead to resolution of the abscess.