Cheryl D. Lew

Childhood sequelae of infant lung disease: Exercise and pulmonary function abnormalities after bronchopulmonary dysplasia

To determine the long-term pulmonary sequelae and effect on exercise tolerance of bronchopulmonary dysplasia (BPD), we studied 10 children at a mean age of 10.4 years, who had been born prematurely, survived respiratory distress syndrome, and subsequently developed BPD, and compared them with eight age-matched normal children born at term. Pulmonary function tests and graded exercise stress tests were performed. Residual volume, the ratio between residual volume and total lung capacity, vital capacity, forced expiratory volume in 1 second, forced expiratory flow between 25% and 75% of vital capacity, and maximal expiratory flows at 80%, 70%, and 60% of total lung capacity were all abnormal (P less than 0.02) in the children with BPD, compared with control values. Pre-exercise transcutaneous CO2 tension was higher (P less than 0.05) in the BPD group than in the control group. At maximal workload, tcPCO2 remained high in patients with BPD compared with control values (P less than 0.05). Arterial oxygen saturation at maximal workload fell below pre-exercise levels in the BPD group (P less than 0.05) but not in control children. There were no differences in maximal oxygen consumption between the BPD group and control children. Exercise-induced bronchospasm occurred in 50% of the BPD group, but not in the control group. We conclude that long-term survivors of BPD have evidence of airway obstruction, hyperinflation, and airway hyperreactivity, compared with a control group. Aerobic fitness was not significantly different in the BPD and control groups, but was achieved in the BPD group at the expense of a fall in SaO2 and a rise in tcPCO2.

The impact of extracorporeal membrane support in the treatment of congenital diaphragmatic hernia

Neonates with congenital diaphragmatic hernia (CDH) treated by immediate surgical intervention and conventional ventilatory support have an overall poor survival. The potential of extracorporeal membrane oxygenation (ECMO) therapy to improve survival of infants with CDH remains controversial. Comparison was made in a single institutions pre-ECMO and post-ECMO survival statistics to establish efficacy of extracorporeal support for persistent pulmonary hypertension (PPH). This study was accomplished by stratifying patients by an oxygen index (OI). Sixty-eight patients were treated for CDH from 1977 to 1986 without ECMO. Fifty-eight patients underwent repair of CDH within the first 24 hours of life. Data could be retrieved for calculation of the OI in 46 patients. Nineteen patients developed an OI of 40 or greater; one survived (5%). Three of 27 patients with an OI less than 40 died (OIs = 34, 38, and 38). Thirty-one patients were treated from 1987 to 1989 and none were excluded from ECMO based on a minimum PO2. Fifteen had an OI less than 40 (range, 1 to 38), were treated conventionally, and 13 survived (87%). Sixteen patients had an OI greater than 40 and 13 qualified for ECMO. Nine of 13 survived (69%). Comparing pre-ECMO and post-ECMO survival for infants with an OI of 40 or greater (5% v 69%), there is a significant improvement in survival when ECMO is used (P less than .001). ECMO support offers a strong adjunct in management of neonates with CDH who develop PPH.

Intratracheal pulmonary ventilation versus conventional mechanical ventilation in a rabbit model of surfactant deficiency.

ABSTRACT: Intratracheal pulmonary ventilation (ITPV) enhances the clearance of CO2 from dead space and lungs by a bias flow of gas administered in the distal trachea. ITPV flow is continuously administered through a separate catheter placed within an endotracheal tube (ETT). After exiting from catheters tip in the distal trachea, the flow of gas is redirected outward away from the lungs. We hypothesized that, compared with conventional mechanical ventilation (CMV), ITPV may increase minute CO2 clearance (Vco2), reduce the partial pressure of CO2 dioxide in arterial gas (Paco2), and reduce distal tracheal peak inspiratory pressure (dPIP). We induced surfactant deficiency in 15 adult rabbits by lung lavage with 10 mL/kg normal saline. Animals were ventilated through a double-lumen 4.0 ETT, inserted through a tracheotomy incision. dPIP, distal positive end expiratory pressure, and distal mean airway pressure were monitored, and the mean exhaled CO2 concentration was measured. For ventilator rates (respiratory rate) of 30, 45, and 70 breaths/min, the study included two phases: phase I compared CO2 clearance and Paco2 between ITPV and CMV using similar ventilatory pressures; phase II evaluated the effectiveness of ITPV in reducing dPIP and tidal volume (Vt), compared with CMV, while maintaining eucapnea. When comparing ITPV and CMV, the following results (mean ± SD) were achieved at respiratory rate of 30, 45, and 70 breaths/min, respectively. Phase I ITPV resulted in mean percent reduction of Paco2 by 31.4 ± 10%, 37.1 ± 9.7% and 38.3 ± 9%; mean percent increase in Vco2 by 61.3 ± 29%, 56 ± 23%, and 98 ± 40%, compared with CMV. Phase II ITPV resulted in mean percent reduction of dPIP by 35.5 ± 14%, 38 ± 10.8%, and 37.2 ± 13.7%, and mean percent reduction in Vt by 34.7 ± 12.9%, 36.4 ± 15%, and 52.7 ± 10.7%, compared with CMV. The changes in Paco2, Vco2 (phase I), and dPIP and Vt (phase II) were all significantly more than 25% (p < 0.05). Oxygenation and pH were not significantly different between ITPV and CMV. We conclude that, in a surfactant deficiency rabbit model, ITPV is an efficient mode of assisted ventilation that increases CO2 clearance and reduces ventilator pressures required for adequate ventilation. We speculate that ITPV can minimize lung barotrauma associated with mechanical ventilation.

Primary Hyperinsulinemia Reduces Surface Active Material Flux in Tracheal Fluid of Fetal Lambs

Summary: We sought to test the hypothesis that hyperinsulinemia per se alters the flux of surface active material (SAM) into tracheal fluid by continuously infusing insulin (0.24 ± 0.04 units/kg/hr, mean ± S.E.) from 112 through 135 days gestation into five chronically catheterised fetal lambs, from which tracheal fluid could be collected.Serum insulin levels in these fetuses (95 ± 10 μU/ml) were greater than in five chronically catheterised control fetuses of the same gestational age (10 ± 1 μU/ml, P < 0.001) and in the mothers (38 ± 6 μU/ml, P < 0.001). Serum glucose levels in the insulin-treated fetuses (10 ± 1 mg/dl) were lower than in the control fetuses (19 ± 1 mg/dl, P < 0.001) and in the mothers (60 ± 3 mg/dl, P < 0.001). Arterial blood gases (pH 7.37 ± 0.01, PO2 23.3 ± 0.05 mm Hg, PCO2 41.5 ± 0.9 mm Hg) and hematocrit (33 + 1% at 127 days gestation and 31 ± 1% at 135 days gestation) in the insulin treated fetuses were not different from the controls.SAM flux into the tracheal fluid of the insulin-treated fetuses was 1 μg/kg/hr, coefficient of variation 373%. This was lower than SAM flux in the control fetuses (26 μg/kg/hr, coefficient of variation 28%, P < 0.01). Moreover, among the control fetuses, SAM began to appear in tracheal fluid at 119 days gestation and was present in all five fetuses by 125 days gestation, whereas SAM did not begin to appear in the insulin-treated fetuses until 127 days gestation and did not appear at all in three of them.Speculation: Chronic hyperinsulinemia reduces surface active material flux into tracheal fluid of fetal lambs. This effect may be partially mediated by reduced substrate (glucose) availability for surface active material phospholipid synthesis, storage, and/or secretion.

Drug 'administration' via breast milk.

In the current popularity of breast-feeding, certain pitfalls for the infant tend to be overlooked. Physicians should be particularly aware with respect to which drugs and toxins can be transmitted by the lactating mother, and which cannot. In aid of such awareness, the authors tabulate the excretion characteristics and compatibility with breast-feeding of more than 200 common drugs and substances.

Review of Intensive Care Unit Admissions for Asthma

A review of ICU admissions for asthma to the Childrens Hospital of Los Angeles was conducted for the period January 1969 through July 1977. The admission rate remained relatively constant during this period. Patients requiring ICU admission tended to be young, intractable severe asthmatics whose asthma started at a very young age. There were three patients who had no previous history of asthma. The incidence of pneumomitis/atelectasis was somewhat greater than has been reported for patients hospitalized for status asthmaticus. A significant number of children received neither intravenous corticosteroids, sympathomimetics nor oxygen therapy while hospitalized prior to transfer to the ICU. Those children receiving mechanical ventilation or intravenous isoproterenol tended to be somewhat younger and had a higher incidence of pneumonitis/atelectasis and more abnormal blood gas determina tions than their counterparts who were not similarly treated. Mechanical ventilation was administered to 15 patients and 19 patients received intra venous isoproterenol. Intravenous isoproterenol resulted in prompt improve ment in most patients; except for one patient who experienced cardiac arrhyth mia (reversed when the dosage was decreased), this medication was well-tolerated.

The Potential Value of the U.N. Convention on the Rights of the Child in Pediatric Bioethics Settings

This article provides support for the use of a particular international human rights law document, the U.N. Convention on the Rights of the Child (CRC), in contemporary pediatric bioethics practice without relying on the legally binding force of the document. It first demonstrates that the CRC’s core commitments and values substantially overlap with the core commitments and values of mainstream bioethics and with the laws of many domestic jurisdictions where mainstream bioethics are currently practiced. It then explores some implications of this overlap. For instance, the substantial international human rights law scholarship on how to understand these commitments and values can be helpful in suggesting ways to operationalize them in domestic bioethics practice and can offer insightful, internationally generated ethical perspectives that may not have been considered. The article also argues that the CRC can help health-care organizations develop policies consistent with the best interests of children and that the CRC can serve as a common language of values for transnational health-care collaborations. However, as a final case discussion demonstrates, whatever the merits of the CRC, one may face practical difficulties in trying to use it.

Actions Speak Louder Than Words: The U.N. Convention on the Rights of the Child and U.S. Pediatric Bioethicists

In exploring the relationship between “child rights” and “pediatric bioethics” and how these disciplines might provide mutual support in advancing the health and wellness of children around the world, our article responds to the questions of whether the U.N. Convention on the Rights of the Child (CRC) could be of any benefit in the United States, the only country that has not yet ratified this international treaty, and whether the CRC has any value for addressing clinical pediatric bioethics’ questions. We describe the considerable influence that the United States had in developing significant components of the CRC, and we argue that the CRC may be useful for U.S. pediatric bioethicists as a tool to advance children’s health policy. We note that ratification of the CRC does not equate with compliance or success. Lastly, we identify a distinction between the use of the term “best interests” by child rights advocates and its use by clinical pediatric bioethicists.

What Is a Parent to Do?: The Case of Baby G.

Born at 24 weeks gestation, Baby G now lies in a neonatal intensive care unit two months post-birth. He has pulmonary hypoplasia, congenital scoliosis, and swallowing issues that will require placement of a feeding tube, and bowel dystonia that interferes with his ability to absorb feedings. Shortly after birth, he experienced a cardiopulmonary arrest and now has obvious neurological impairments. As a result of incomplete development of his lungs and severe chronic lung disease, he cannot breathe on his own. Because of his chronic respiratory failure, tracheostomy and long-term assisted ventilation was offered as an option that would allow him to be discharged from the acute care setting. However, his congenital scoliosis and severe neurocognitive impairments mean that he has little potential for eventual weaning from assisted ventilation. While there are surgeries available to correct his scoliosis, the outcome of such surgeries is uncertain; they could not be performed before two to three years of age, and the risks are increased due to his pulmonary co-morbidities.

Reduction of respiratory system resistance of rabbits with surfactant deficiency using a novel ultra thin walled endotracheal tube

&NA; The ultra thin walled, two‐stage endotracheal tube (UTW‐TS‐ETT) is very flexible, nonkinking, and has a widened extralaryngeal portion. The UTW‐TS‐ETT has a greater ID/OD (internal diameter/outer diameter) ratio than a comparable standard endotracheal tube (ST‐ETT) because of its thinner wall: 0.2‐0.25 mm in UTW‐TS‐ETT, compared to 0.55‐0.8 mm in ST‐ETT. The authors hypothesized that in an animal model of lung disease, significant reductions in respiratory system resistance (Rrs) of 30‐40% would be achieved using the UTW‐TS‐ETT, compared to Rrs achieved with the comparable ST‐ETT. This study compared the pulmonary mechanics of rabbits (N = 17, body weight 3.4‐4.7 kg) before and after induction of surfactant deficiency, using either ST‐ETT (OD 4.9 mm, ID 3.5 mm) or UTW‐TS‐ETT (OD 5.0 mm, ID 4.6 mm). Animals were sedated, paralyzed, and ventilated by an ETT placed through a tracheotomy incision. Surfactant deficiency was induced by lavaging the lungs with normal saline (10 ml/kg). Pulmonary mechanics were measured on identical ventilator settings for each ETT used at baseline and at 45 min after lavage. Compared to ST‐ETT, UTW‐TS‐ETT reduced Rrs by 50.6 ± 8.7% in normal lungs (significantly more than 40%; p < 0.01), and by 41.47 ± 16.2% in surfactant deficient lungs (significantly more than 30%; p < 0.05). Tidal volume increased with UTW‐TS‐ETT in all animals but did not achieve statistical significance. The UTW‐TS‐ETT did not induce significant changes in respiratory system compliance, PaO2, PaCO2, or pH. It is concluded that UTW‐TS‐ETT significantly reduces Rrs in rabbits with either normal lungs or with surfactant deficient lungs. This novel ETT may be beneficial for ventilated patients with increased Rrs, by effecting a decrease in Rrs and thus reducing the work of breathing and improving ventilation efficiency. ASAIO Journal 1996;42:1000‐1005.