Kim Chi Bui

A prospective randomized trial of delayed versus immediate repair of congenital diaphragmatic hernia

From March 1990 to January 1993, a randomized prospective study was performed to determine the optimal timing of surgery for infants with high-risk congenital diaphragmatic hernia (CDH). Thirty-two CDH patients who presented with respiratory distress within 12 hours after birth were randomly divided into two groups: Group A had early repair (within 6 hours), and group B had delayed repair (at 96+ hours). Extracorporeal membrane oxygenation (ECMO) was initiated in both groups as necessary. Fourteen patients were assigned to group A, and 18 were assigned to group B. Two patients initially assigned to group A had acute deterioration, and their operations had to be postponed. Data were collected, but these patients were eliminated from the study. The two groups were comparable based on gestational age, birth weight, Bohns criteria, and oxygenation and ventilatory index. Nine of 12 group A patients (75%) survived, and 13 of 18 group B patients (72%) survived (P > .05, not significant). The ECMO requirements for the two groups were not significantly different (8 of 12 (67%) v 16 of 18 (89%); P > .05). Surgical intervention for bleeding complications related to ECMO was required in three of eight (38%) with immediate repair and seven of 16 (44%) with delayed repair (P > .05). There was no difference in survival nor incidence of ECMO between the two groups. This is the first prospective study of timing of hernia repair that supports the conclusions of earlier reports of retrospective studies.

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.

Comparability of antimüllerian hormone levels among commercially available immunoassays

OBJECTIVE To compare antimüllerian hormone (AMH) levels among three commercially available AMH immunoassays: AMH Gen II (Beckman Coulter), Ultrasensitive AMH (Ansh Labs), and picoAMH (Ansh Labs). DESIGN Cross-sectional. SETTING Academic reproductive endocrinology program. PATIENT(S) 90 newly diagnosed breast cancer patients before cancer treatment. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Proportion of detectable AMH levels by immunoassay, and comparability among assays. RESULT(S) At a mean age of 38.1 years, the median (interquartile range) AMH level for the cohort was 0.92 [1.35] ng/mL for the Gen II assay, 1.68 [2.30] ng/mL for the Ultrasensitive assay, and 1.52 [2.41] ng/mL for the picoAMH assay. Significantly higher proportions of detectable AMH levels were observed with the picoAMH kit (97%) compared with both the Gen II (84%) and Ultrasensitive (92%) assays. Although the AMH results were highly correlated among the assays (r = 0.92-0.99), the Gen II AMH levels were consistently lower than both Ultrasensitive and picoAMH levels. Moreover, as AMH levels increased, the magnitude of difference grew larger between Gen II and each of the other two assays. CONCLUSION(S) Measurement of AMH levels with the picoAMH kit maximized detection at very low levels, particularly in contrast with the Gen II kit. Conversion of AMH levels from different immunoassays using regression equations is potentially highly inaccurate.

Phospholipid and surfactant protein A concentrations in tracheal aspirates from infants requiring extracorporeal membrane oxygenation

To test the hypothesis that infants with severe respiratory failure and the need for extracorporeal membrane oxygenation (ECMO) are surfactant deficient, we measured the amount of surfactant phospholipids, disaturated phosphatidylcholine, surfactant protein A, and protein in tracheal aspirates from 22 infants, who received ECMO therapy for respiratory failure with meconium aspiration syndrome (n = 18) or pneumonia (n = 4). Tracheal suction material was obtained in a standardized way every 4 hours during the period of ECMO treatment and pooled for 24-hour periods. During ECMO, mean total phospholipid, disaturated phosphatidylcholine, and surfactant protein A values in tracheal aspirates increased and protein values decreased significantly, predominantly during the 72-hour period before infants were weaned from ECMO. Of the 22 infants, 14 had an increase in tracheal aspirate phospholipid values of more than 200% and were found to need a shorter period of ECMO support (p less than 0.005) and post-ECMO ventilatory support (p less than 0.025) than did the eight infants with stationary or only moderate increases in tracheal aspirate phospholipid values, three of whom had pneumonia. We conclude that infants with respiratory failure who require ECMO treatment often have surfactant deficiency. We speculate that surfactant treatment might decrease the need for or the duration of ECMO support.

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.

Comparison of intratracheal pulmonary ventilation and hybrid intratracheal pulmonary ventilation with conventional mechanical ventilation in a rabbit model of acute respiratory distress syndrome by saline lavage

Objectives: To study changes in PaCO2 and PaO2 during intratracheal pulmonary ventilation (ITPV) and hybrid intratracheal pulmonary ventilation (h‐ITPV) compared with conventional mechanical ventilation (CMV) in a rabbit model of respiratory failure, and to define the technique of h‐ITPV that combines conventional mechanical ventilation and ITPV. Design: Prospective, interventional study. Subjects: Twelve adult New Zealand White rabbits. Interventions: Surfactant deficiency was induced by saline lavage, and rabbits were randomized to either ITPV or h‐ITPV. The study consisted of four phases: phase 0, CMV after saline lavage, ventilator rate 30 breaths/min; phase I, ITPV or h‐ITPV initiated at the same pressure and rate as in phase 0; phase II, ITPV or 1.0 L/min h‐ITPV bias flow, with peak inspiratory pressure (PIP) decreased and ventilator rate increased to achieve the lowest tidal volume while maintaining adequate gas exchange; and phase III, animals returned to CMV. Measurements and Main Results: In phase I, no difference in PaCO2 was observed between ITPV, h‐ITPV, or CMV. There was a decrease in PaO2 when switching from CMV to ITPV but not to h‐ITPV. In phase II, it was possible to decrease PIP (average of 37% for ITPV and 36% for h‐ITPV) and tidal volume (average of 64% for ITPV and 53% for h‐ITPV) without compromising gas exchange (p < .05). Oxygenation tended to improve from phase 0 to the end of phase II. In phase III, PaCO2 increased (average of 71% for ITPV and 79% for h‐ITPV) and pH decreased (p < .05). Normocapnia was achieved using significantly higher PIP and tidal volume, compared with phase 0 (p < .05). Conclusions: ITPV and h‐ITPV can effectively ventilate and oxygenate rabbits with surfactant‐deficient lungs at tidal volumes and therefore pressures lower than required with CMV. Maximum benefit appears to occur at high ventilator rates. These findings suggest that both modes of ventilation may represent powerful new tools in the management of patients with acute respiratory failure.

Comparison of intratracheal pulmonary ventilation with hybrid intratracheal pulmonary ventilation in a rabbit model of acute respiratory distress syndrome by saline lavage.

We compared different hybrid mode ITPV (h-ITPV) flow rates, and h-ITPV with intratracheal pulmonary ventilation (ITPV) with respect to CO2 clearance and oxygenation. Surfactant deficiency was induced in six adult rabbits with saline lavage. The study consisted of three phases. Phase 0: Stabilization on conventional mechanical ventilation (CMV). Phase I: Bias flow initiated at same pressure and respiratory rate as Phase 0. Flow rates of 25%, 50%, 75% h-ITPV, and ITPV were initiated. Animals were transitioned from CMV to 25% h-ITPV proceeding sequentially to ITPV or vice versa. Phase II: Animals were returned to CMV. Statistical analysis included the two-way analysis of variance (ANOVA) and repeated measures ANOVA with Tuckeys test. No difference in PaCO2 was observed among all h-ITPV flow rates or between h-ITPV and ITPV. After bias flow was introduced (transition from Phase 0 to Phase I), PaCO2 decreased by 37%. PaCO2 increased by 119% during Phase II. Oxygenation improved in all animals, particularly in those transitioned to 25% h-ITPV and proceeding to ITPV. No difference in CO2 clearance between ITPV and h-ITPV was observed. Even at low bias flows, excellent CO2 clearance was achieved. Oxygenation was superior when animals were transitioned from CMV to h-ITPV. Hybrid-ITPV offers some advantages over ITPV and may represent a powerful tool in the management of acute respiratory distress syndrome (ARDS).

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.

Predictors of neonatal mortality in 1,500-1,999 g premature infants with respiratory failure. Basis for ECMO Therapeutic Trial.

Despite the introduction of new ventilation techniques and surfactant therapy, some premature infants still experience severe respiratory failure and either die or survive with severe bronchopulmonary dysplasia. Extracorporeal membrane oxygenation is currently not offered for preterm infants with a birth weight less than 2,000 g, mainly because of the potential high risk for intracranial hemorrhage. The aim of this study was to determine risk predictors for mortality alone and for mortality or major lung morbidity in 1,500–1,999 g premature infants with respiratory failure. We reviewed the medical records of all preterm infants (n = 459) with respiratory failure and a birth weight of 1,500–1,999 g treated at five medical centers from 1989 to 1991. Of those infants, 23 (5%) had severe respiratory failure, defined as a requirement for ventilatory support with the fraction of inspired oxygen ≥ 0.8 or peak inspiratory pressure ≥ 30 cmH2O for ≥ 3 hr in the 1st week of life. A mortality of ≥ 75% was associated with a single arterial/alveolar oxygen ratio ≤ 0.04; pulmonary air leak alone or pulmonary air leak with a mean airway pressure ≥ 12 cmH2O; and arterial oxygen tension ≤ 50 mmHg. These risk predictors may provide a basis for the selection of patients for future clinical trials of extracorporeal membrane oxygenation in this high-risk group of 1,500–1,999 g premature infants with severe respiratory failure.