Total respiratory support with tidal flow extracorporeal circulation in adult sheep

A novel pressure gated tidal flow extracorporeal circulation (TF ECC) device was developed, and it was hypothesized that it could provide total respiratory support in apneic adult sheep without adverse hemodynamic or cardiac effects. The circuit consisted of a single lumen cannula, computer driven tubing occluders gated by circuit pressure, a nonocclusive peristaltic blood pump, a spiral coiled membrane lung, and a heat exchanger. Six paralyzed, anesthetized adult sheep were instrumented and TF ECC was instituted via cannulation of the right atrium. Total respiratory support was provided by the circuit during an apneic period of 6 hours. Echocardiography was performed with the animal instrumented (baseline) and after 2 hours of TF ECC. Circuit blood tidal volume was 172.6 +/- 18.0 cc, resulting in a TF ECC flow of 71.1 +/- 10.1 cc/kg/min. At the end of the study period, PaCO2 was 35.5 +/- 7.6 mmHg, paO2) was 91.2 +/- 30.6 mmHg, and pulmonary artery oxygen saturation (SPAO2) was 95 +/- 5%. Hemodynamic stability was maintained with no significant differences at baseline and after 6 hours in mean arterial pressure, mean pulmonary artery pressure, or heart rate noted. Echocardiographic evaluation showed preserved fractional shortening of the left ventricular (LV) septal-lateral dimension (baseline 32.4 +/- 11.4%; 2 hours 34.8 +/- 8.4%). This study demonstrates TF ECC provides total respiratory support without adverse hemodynamic effects, and preserved LV function.

Distribution of pulmonary blood flow and total lung water during partial liquid ventilation in acute lung injury

BACKGROUND

Gas exchange is improved during partial liquid ventilation (PLV) with perfluorocarbon in animal models of acute lung injury. The mechanisms are not fully defined. We hypothesize that redistribution of pulmonary blood flow (PBF) along with redistribution of, and decrease in, total lung water (TLW) during PLV may improve oxygenation.

METHODS

We characterized PBF and TLW in anesthetized adult dogs by using positron emission tomography with H2(15)O. Measurements of gas exchange, PBF, and TLW were made before and after acute lung injury was induced with intravenous oleic acid. The same measurements were made during PLV (with 30 ml/kg perfluorocarbon) and compared with gas ventilated (GV) controls.

RESULTS

Oxygenation was significantly improved during PLV. PBF redistributed from the dependent zone of the lung to the nondependent zones, thus potentially improving ventilation/perfusion relationships. However, a similar pattern of PBF redistribution was observed during GV such that there was no significant difference between groups. TLW redistributed in a similar pattern during PLV. By quantitative measurements, PLV ameliorated the continued accumulation of TLW compared with GV animals.

CONCLUSIONS

We conclude that PBF and TLW redistribution and attenuation of increases in TLW may contribute to the improvement in gas exchange during PLV in the setting of acute lung injury.

Prolonged extracorporeal life support (ECLS) for varicella pneumonia

OBJECTIVE

To review the institutional experience of a national tertiary referral center for extracorporeal life support (ECLS) in severe varicella pneumonia.

DATA SOURCES

Hospital records and ECLS flow sheets.

STUDY SELECTION

All pediatric (nonneonatal) and adult patients who were treated for varicella pneumonia with ECLS at the University of Michigan Medical Center between 1986 and 1995.

DATA EXTRACTION

Diagnosis of varicella pneumonia was made by history of recent exposure to chickenpox, progressive dyspnea, fever, a characteristic diffuse, vesicular rash, and a supporting chest roentgenogram. Indications for ECLS included a shunt fraction of > 30% or PaO2/FlO2 ratio of < 80 despite maximal conventional therapy, which included aggressive diuresis, blood transfusions to optimize oxygen-carrying capacity, pressure-controlled/inverse-ratio ventilation, and intermittent prone positioning.

DATA SYNTHESIS

Between 1986 and 1995, 191 patients were referred for ECLS. Among these patients, there were 51 (27%) cases of viral pneumonia, of which nine cases were due to acute varicella-zoster infection. Intravenous acyclovir was administered to eight of the nine patients. Of the nine patients, two patients improved using conventional ventilator management, and seven patients underwent ECLS. Overall survival on ECLS was 71% (5/7). The mean (+/-SD) alveolar-arterial oxygen gradient and PaO2/FlO2 ratio were 533 +/- 101 torr (71.3 +/- 13.5 kPa) and 67 +/- 24, respectively. The median duration of mechanical ventilation before ECLS and the subsequent duration of ECLS were 4 and 12.8 days, respectively. One of the deaths was from progressive right heart failure secondary to pulmonary hypertension and the other death was from overwhelming Pseudomonas sepsis.

CONCLUSIONS

Early recognition of imminent pulmonary failure and rapid institution of ECLS are critical in the successful management of severe, life-threatening varicella pneumonia.

Pulmonary pathology of patients treated with partial liquid ventilation

Initial trials of partial liquid ventilation (PLV), which is gas ventilation of perfluorocarbon-filled lungs, are underway in patients with severe respiratory failure. We report the first study of the effects of the perfluorocarbon, perflubron, on the lung. Necropsies were conducted in nine patients (seven adults and two neonates; mean adult age, 31 +/- 5 yr) managed with PLV (average number of doses, 4 +/- 1). All of the patients required extracorporeal life support. The patients had pneumonia with the acute respiratory distress syndrome (six patients), trauma/capillary leak syndrome (one patient), congenital diaphragmatic hernia (one patient), and primary pulmonary hypertension (one patient). Nine adult patients (mean age, 37 +/- 5 yr) with acute respiratory distress syndrome requiring extracorporeal life support served as a control. Pathologic findings were evaluated in both groups. Lung weights in the adult patients of both groups were elevated (mean weight of PLV-treated right lung, 1401 +/- 186 g; mean weight of PLV-treated left lung, 1131 +/- 177 g; mean weight of control right lung, 1018 +/- 91 g; mean weight of control left lung, 988 +/- 80 g). There was no significant difference between the two groups (right lung, P = .066; left lung, P = .436). Frequent gross findings included focal consolidation, patchy hemorrhage, and glassy cut surfaces. The histologic findings were similar in both groups. Diffuse alveolar damage (either proliferative phase or mixed proliferative and exudative phases) was seen in all nine of the study patients. Eight of the nine control patients had diffuse alveolar damage (five had proliferative phase only, one had mixed proliferative and exudative phases, and two had exudative phase only). One other patient had extensive parenchymal necrosis. Other frequent findings were intra-alveolar hemorrhage, numerous intra-alveolar macrophages, and organization of exudate. PLV with perflubron in patients with adult and neonatal respiratory distress syndromes is not associated with unique pathologic findings in the human lung.

Vesicoureteral reflux and ureteropelvic junction obstruction: association, treatment options and outcome

PURPOSE

We investigated the association, treatment options and outcomes of patients with ureteropelvic junction obstruction and concomitant vesicoureteral reflux.

MATERIALS AND METHODS

We analyzed 6,790 consecutive pediatric urology records at our university. Treatment options included observation, and primary pyeloplasty, ureteroneocystostomy and nephroureterectomy. Hydronephrosis, reflux and obstruction were judged as resolved, improved, unchanged or worse.

RESULTS

A total of 1,140 patients had vesicoureteral reflux, 224 had ureteropelvic junction obstruction and 41 had both conditions (39 ipsilateral and 6 contralateral kidneys). There was no increased risk of obstruction in patients with reflux when all grades of reflux were grouped (odds ratio 1.26, confidence interval 0.91 to 1.71). In contrast, subgroup analysis of patients with high grade reflux demonstrated a 5-fold increased risk of obstruction (odds ratio 5.0, confidence interval 2.4 to 10.8). One patient was lost to followup. Observation of 6 kidneys led to resolution of reflux in 3 (50%), resolution of obstruction in 3 (50%) and resolution or improvement of hydronephrosis in 4 (67%). Primary pyeloplasty was done on 29 kidneys with 10 (35%) requiring subsequent ureteroneocystostomy. At latest followup hydronephrosis resolved or improved in 24 patients (83%), vesicoureteral reflux resolved or improved in 19 (66%) and ureteropelvic junction obstruction resolved in all. Primary ureteroneocystostomy was performed on 5 kidneys, all of which required subsequent pyeloplasty. Hydronephrosis resolved in 3 patients (60%), and reflux and obstruction resolved in all. Two patients treated with primary nephroureterectomy, and 1 who underwent concomitant pyeloplasty and ureteroneocystostomy have had no subsequent urological problems. One patient awaits primary pyeloplasty.

CONCLUSIONS

High grade vesicoureteral reflux is associated with ureteropelvic junction obstruction. No association with low or intermediate grade reflux was demonstrated. While some patients may be monitored expectantly, in our series pyeloplasty or nephrectomy was required in 81% and ureteroneocystostomy was required in 36%. In no case did primary ureteroneocystostomy protect against the subsequent need for pyeloplasty.

Oxygen dynamics during partial liquid ventilation in a sheep model of severe respiratory failure

BACKGROUND

We evaluated the relationship of dose of perflubron and gas tidal volume to oxygen dynamics during partial liquid ventilation in the setting of respiratory failure.

METHODS

Lung injury was induced in 16 sheep by using right atrial injection of 0.15 ml/kg oleic acid. Animals were ventilated with 15 ml/kg gas tidal volume and stabilized. Animals were then divided into three groups: (1) gas ventilation with a tidal volume of 15 ml/kg (control, GV, n = 5); (2) partial liquid ventilation at a gas tidal volume of 15 ml/kg with 10 ml/kg incremental pulmonary dosage of perflubron from 10 to 50 ml/kg (best fill, BF, n = 6); (3) administration of 35 ml/kg perflubron pulmonary dose with 5 ml/kg incremental increase in gas tidal volume from 10 to 30 ml/kg (best tidal volume, BTV, n = 5).

RESULTS

Arterial oxygen saturation increased with increasing dose of perflubron and gas tidal volume (BF, p = 0.01; BTV, p = 0.001). A simultaneous trend toward a reduction in cardiac index was observed with increasing dose of perflubron (BF, p = 0.01). Maximal increase in mixed venous oxygen saturation was observed in the BF and BTV groups at a cumulative perflubron dose of 40 ml/kg and a gas tidal volume of 20 ml/kg, respectively.

CONCLUSIONS

In this sheep lung injury model oxygenation improves with incremental increases in perflubron dose or gas tidal volume, and the mixed venous oxygen saturation appears to be optimal at a cumulative perflubron dose of 40 ml/kg and a gas tidal volume of 20 ml/kg.

A comparison of the efficacy of pyloromyotomy and pyloroplasty in patients with gastroesophageal reflux and delayed gastric emptying

PURPOSE

Delayed gastric emptying (DGE) in children with gastroesophageal reflux (GER) is often treated with a gastric emptying procedure. Although pyloroplasty is the most common gastric emptying procedure performed, pyloromyotomy is easier to perform and is associated with less morbidity. The aim of this study was to compare the efficacy of pyloromyotomy and pyloroplasty in children with DGE and GER undergoing a fundoplication.

MATERIALS AND METHODS

We reviewed the charts of 54 patients with DGE who underwent pyloromyotomy (n = 29), or pyloroplasty (n = 25) along with a fundoplication. A technetium 99-labeled sulfur colloid liquid-phase gastric emptying study (GES) was performed in the pre- and early postoperative period (within 6 months after operation). Normal stomach emptying was defined as greater than 40% at 1 hour. Comparisons were made with regard to postoperative complication rate, incidence of redo fundoplication, length of postoperative hospital stay, and pre- and postoperative GES.

RESULTS

The pyloroplasty and pyloromyotomy group were comparable in terms of age, sex, operative indications, and neurological status. There was no significant difference in the GES between the two groups preoperatively. There was a trend toward a decreased incidence of early postoperative complications including gas bloat, wound infection, pneumonia, dysphagia, bowel obstruction and dumping syndrome in the pyloromyotomy (8, 28%) when compared with the pyloroplasty group (12, 48%, P = .10). The mean postoperative hospital stay was 10.6 +/- 1.4 days for the pyloroplasty group and 7.6 +/- 1.0 days for the pyloromyotomy group (P + .08). The incidence of a redo fundoplication was 8% in the pyloroplasty and 7% in the pyloromyotomy group. Postoperative gastric emptying increased significantly in both groups (pyloroplasty group, from 18.1 +/- 3.1 to 49.5 +/- 7.9%, P = .0005; pyloromyotomy group, from 19.3 +/- 2.1 to 41.2 +/- 3.7%, P = .0001). There was no significant difference in the postoperative GES between the two groups (P = .289).

CONCLUSION

Both pyloroplasty and pyloromyotomy performed in conjunction with a fundoplication resulted in a significant increase in early postoperative gastric emptying. There was no advantage of pyloroplasty over pyloromyotomy during this follow-up period. These data suggest that pyloromyotomy is an effective gastric emptying procedure in children with GER and DGE.

Prenatal ultrasonography frequently fails to diagnose congenital diaphragmatic hernia

Despite increased use of prenatal ultrasonography and well-defined guidelines to aid in the detection of congenital diaphragmatic hernia (CDH), approximately half of neonates born with CDH undergo a prenatal scan that does not diagnose the defect. The purpose of this study was to (1) examine the use of prenatal ultrasonography in neonates with CDH, (2) determine possible reasons that contributed to the failure to detect the abnormality, and (3) evaluate the clinical impact of a diagnostic versus a nondiagnostic study. From 1985 to 1995, 136 consecutive neonates with CDH symptomatic within 24 hours of birth were treated at the University of Michigan Medical Center. Medical records and a University of Michigan CDH database were reviewed for prenatal ultrasound status, side of herniation, site of birth, survival, and extracorporeal life support (ECLS) use. Sonograms that did not diagnose CDH were collected and reviewed by a radiologist for possible-reasons why the diagnosis was missed. Over the 10-year period, use of ultrasonography increased from 33% to 100%, but the false-negative rate remained approximatedly 55%. In reviewing 40 nondiagnostic studies in 25 patients, 25% had technical difficulties, 57% failed to follow established guidelines (localization of the stomach and visulization of the heart with all four chambers), and 33% missed findings (intrathoracic stomach and mediastinal shift) consistent with CDH. There was no significant difference in survival or use of ECLS between neonates with a diagnostic versus nondiagnostic study (53% v 77% survival, P = 0.09; 64% v 42% ECLS, P = .29) Careful attention to following established guidelines and an increased appreciation for the abnormalities would be expected to increase the sensitivity of ultrasonography in detecting CDH. Increased prenatal diagnosis will allow for thorough evaluation for associated malformations, detection of chromosomal abnormalities, and early referra with intrauterine transport to a tertiary care center before delivery.

Acute respiratory distress syndrome: CT findings during partial liquid ventilation

To describe the computed tomographic (CT) appearance of perflubron-filled lungs during partial liquid ventilation to treat acute respiratory distress syndrome, scans of the thorax were obtained in nine patients between June 1994 and December 1995. The distribution of perflubron was gravity dependent in four patients, with a mean interval of 6.25 days between scanning and perflubron administration; was patchy in four patients (mean interval, 16 days); and was homogeneous in one patient (interval, 3 days). Extraparenchymal perflubron was seen in intrathoracic lymph nodes (n = 4), supraclavicular nodes (n = 2), axillary nodes (n = 1), and both the retroperitoneum and the mediastinum (n = 2). In one patient, perflubron was seen in a pneumatocele and the pleural space. The distribution of perflubron in the lungs is typically gravity dependent.

Mortality is directly related to the duration of mechanical ventilation before the initiation of extracorporeal life support for severe respiratory failure

OBJECTIVE

To investigate the relationship between the period of mechanical ventilation before extracorporeal life support and survival in patients with respiratory failure.

DESIGN

Retrospective review.

SETTING

Surgical intensive care unit at a university medical center.

PATIENTS

Thirty-six consecutive adult patients with severe respiratory failure managed with extracorporeal life support.

INTERVENTIONS

Extracorporeal life support was utilized in 36 acute respiratory failure adult patients with a variety of diagnoses and an estimated mortality rate of > 90%. Management protocols were followed before and during extracorporeal life support. The 36 patients were physiologically similar before extracorporeal life support was initiated: shunt of 48 +/- 17%; F10(2) of 1.0 +/- 0.1; peak inspiratory pressure of 56 +/- 16 cm H2O; positive end-expiratory pressure of 14 +/- 6 cm H2O; and respiratory rate of 23 +/- 10 breaths/ min. Ventilation was utilized for 1 to 17 days before extracorporeal life support. Typical lung rest settings during extracorporeal life support were F10(2) of 0.40, peak inspiratory pressure of 30 cm H2O, positive end-expiratory pressure of 10 cm H2O, and respiratory rate of 6 breaths/min. Death was almost always secondary to end-stage pulmonary failure.

MEASUREMENTS AND MAIN RESULTS

Survival (hospital discharge) in these 36 patients was inversely associated with the number of days of preextracorporeal life support ventilation, with a 50% mortality rate predicted by logistic regression after 5 days of mechanical ventilation. The overall survival rate was 18 (50.0%) of 36 patients.

CONCLUSIONS

In severe acute respiratory failure treated with lung rest and extracorporeal life support, a predicted 50% mortality rate was associated with 5 days of preextracorporeal life support mechanical ventilation.

Innovative therapies in the management of newborns with congenital diaphragmatic hernia

A number of innovative approaches have been explored in the hope of improving the outcome in newborns with congenital diaphragmatic hernia (CDH) and respiratory insufficiency. Among these are the techniques of delayed approach to the repair of the diaphragmatic hernia; permissive hypercapnia; nitric oxide and surfactant administration; intratracheal pulmonary ventilation; liquid ventilation; perfluorocarbon-induced lung growth; and lung transplantation. Although early in their clinical evolution, these interventions are developing rapidly and hold promise for improving the outcome in patients with CDH.

Perfluorocarbon protects lung epithelial cells from neutrophil-mediated injury in an in vitro model of liquid ventilation therapy

Liquid ventilation with perfluorocarbon has been effective in improving gas exchange and pulmonary function in the setting of acute respiratory failure. How improvement is brought about remains unknown. In the present study, we examined perfluorocarbon for effects on neutrophil function and for effects on neutrophil-epithelial cell interactions that could underlie its in vivo activity. Exposure of neutrophils in vitro to perfluorocarbon followed by washing did not interfere with their ability to generate oxidants or release proteolytic enzymes upon subsequent stimulation. Likewise, such treatment did not interfere with subsequent adhesion of the neutrophils to monolayers of epithelial cells or with neutrophil-induced injury to these cells. In contrast, when perfluorocarbon was added to neutrophils and epithelial cells together and the neutrophils then stimulated, it reduced their adhesive interaction with the target cells and concomitantly reduced target cell injury. In companion studies, cells were obtained by bronchial lavage of perfluorocarbon-treated patients with acute respiratory distress syndrome (ARDS) and analyzed for oxidant production. Oxidant-generating capacity by the cells obtained from the bronchial lavage fluid was similar to that of peripheral blood neutrophils. These data are consistent with the suggestion that perfluorocarbon protects cells in vitro from neutrophil-mediated injury, at least in part, by acting as a mechanical barrier. These findings are consistent with a potential mechanism of action in vivo.

Effect of very delayed repair of congenital diaphragmatic hernia on survival and extracorporeal life support use

BACKGROUND

Since November 1992, operative repair in neonates with congenital diaphragmatic hernia (CDH) at this institution was delayed until respiratory insufficiency had resolved.

METHODS

A retrospective analysis was performed (n = 33) comparing delayed repair with our previously reported institutional experience with immediate repair from January 1988 to October 1992 (n = 66). Infants with severe genetic defects or moribund conditions or who were premature were not considered candidates for repair or extracorporeal life support (ECLS), but they were included in the survival analysis. Survival was defined as hospital discharge. Data were compared with an independent t test or Pearson chi-squared test.

RESULTS

Mean age at repair was 8.9 +/- 4.5 days (range, 3 to 20 days). Eleven infants in the study group were placed on ECLS (33% versus 68% in the comparison group; p = 0.001). Six of these infants survived (55% versus 58% in the comparison group; p = 0.846). Of these survivors, one patient was repaired while on ECLS, and the remainder underwent repair after decannulation from ECLS. All 20 of the remaining candidates for repair survived without need for ECLS. Overall survival was 79% versus 56% in the comparison group (p = 0.027).

CONCLUSIONS

Our current data suggest that very delayed repair of newborns with CDHs is associated with an increase in the overall survival and a decrease in the use of ECLS when compared with previous experience at this institution.

Extracorporeal life support for cardiovascular support in adults

The authors retrospectively reviewed their institution's experience with extracorporeal life support (ECLS) for adult cardiovascular failure to determine efficacy and further indications for its use. From 1985 to 1996, venoarterial ECLS was used in 27 adult patients. Indications for ECLS included post cardiotomy cardiac failure, primary myocardial failure, bridge to transplant, and emergency cardiopulmonary resuscitation. The average age was 38.7 +/- 2.7 years and duration of support was 164.0 +/- 26.8 hr. Overall cardiovascular recovery from ECLS was 44%, and hospital survival was 30%. Late deaths were due to multisystem organ failure. Best results were obtained in patients whose processes were reversible during a short duration of ECLS (< 91.6 +/- 33.3 hr. The worst results were obtained in post cardiotomy patients who underwent prolonged support with ECLS. Evaluation of physiologic parameters during the first 30-48 hr of support showed marked improvements from values before ECLS. Because of its relative ease of deployment and its rapid correction of acute physiologic derangements, ECLS can be used as a temporary means of support to determine extent and reversibility of organ dysfunction. Longer term support should include consideration of other mechanical assist devices. The authors no longer consider bridge to transplant an indication for ECLS due to relative donor unavailability.

The effect of pre-ECLS ventilation time on survival and respiratory morbidity in the neonatal population

Although mechanical ventilation for more than 7 to 10 days has been considered a contraindication to the application of extracorporeal life support (ECLS) in neonates, the outcome and respiratory morbidity for newborns placed on ECLS after more than 7 days of ventilation have not been well characterized. The purpose of this study was to determine the impact of pre-ECLS ventilation time on the rate of survival, the likelihood of the development of bronchopulmonary dysplasia (BPD), and the need for supplemental oxygen at the time of discharge. Examination of the Extracorporeal Life Support Organization (ELSO) Registry showed that 6,110 neonates were treated for respiratory failure with a pre-ECLS ventilation time of less than 14 days between January 1990 and May 1995. Gestational age (GA), birth weight (BW), indication for ECLS, and diagnosis were compared with the rate of survival, the discharge diagnosis of BPD, and the need for home oxygen. The GA and BW of neonates placed on ECLS during the first week of life (n = 5,888) did not differ significantly from those of neonates whose ECLS was begun in the second week of life (n = 222). The neonates were divided into two groups (early, ventilation time of 3 to 6 days; late, ventilation time of 7 to 10 days) to determine the odds ratios for survival, BPD, and home oxygen. Logistic regression analysis was used to develop a model to predict the rate of survival, the risk for the development of BPD, and the need for home oxygen given the length of pre-ECLS ventilation time. The late group was less likely to survive (odds ratio, 1.8; 95% confidence interval [CI], 1.21 to 2.68). The late group also had approximately twice the risk for the development of BPD (odds ratio, 1.9; 95% CI, 1.2 to 3.04) and a trend toward an increased incidence of home oxygen use (odds ratio, 1.55; 95% CI, 0.92 to 2.60). The authors conclude that (1) there is a greater risk of mortality and BPD and a trend toward an increased need for home oxygen with increased time on the ventilator before ECLS; (2) at 14 days the predicted probability of survival is still 53% (95% CI, 31% to 74%); (3) at 14 days the predicted probability of BPD is 54% (95% CI, 28% to 78%); and (4) based on these data, it is reasonable to consider application of ECLS to patients who have had mechanical ventilation for up to 14 days.

Partial liquid ventilation in a child on extracorporeal life support

A 14 month old child was referred for management of acute respiratory distress syndrome after aspiration of paraffin lamp oil. Initial management with conventional ventilation and subsequent management with high frequency oscillatory ventilation produced pulmonary air leaks, further compromising clinical management. After initiating extracorporeal life support and low pressure ventilation, pulmonary air leaks subsided. The patient was then successfully managed by a protocol including partial liquid ventilation with perfluorocarbon. This case report details the authors' experience with the first child with respiratory failure to be managed with partial liquid ventilation while on extracorporeal life support.

Efficacy of perfluorocarbon partial liquid ventilation in a large animal model of acute respiratory failure

OBJECTIVE

To demonstrate the efficacy of partial perfluorocarbon liquid ventilation in large animal model of acute respiratory failure.

DESIGN

Prospective, randomized, controlled trial.

SETTING

Animal laboratory at a university medical center.

SUBJECTS

Ten adult sheep, weighing 53.0 +/- 2.8 kg.

INTERVENTIONS

After assessment of baseline physiologic data, acute respiratory failure was induced by right atrial injection of oleic acid (0.2 mL/kg). Five animals (partial liquid ventilation group) underwent sequential intratracheal dosing of 10 mL/kg of perflubron at 30-min intervals to the following cumulative doses: 10, 20, 30, 40, and 50 mL/kg. The remaining five animals were gas ventilated (control group). Physiologic data were assessed at 30-min intervals in both groups for the 2.5-hr experimental period or until death.

MEASUREMENTS AND MAIN RESULTS

When compared with control animals, intratracheal perfluorocarbon instillation resulted in significant improvements in arterial oxygen saturation (arterial oxygen saturation after 50 mL/kg: partial liquid ventilation, 96 +/- 3%; control, 55 +/- 8%; p = .001) and physiologic shunt (physiologic shunt after 50 mL/kg dose: partial liquid ventilation, 2 +/- 8%; control, 64 +/- 5%; p = .004). Oxygen delivery improved with perfluorocarbon instillation, but this improvement was not significant. No significant difference in pulmonary compliance was observed during partial liquid ventilation when compared with controls (pulmonary compliance: partial liquid ventilation, 0.43 +/- 0.04 mL/ cm H2O/kg; control, 0.53 +/- 0.03 mL/cm H2O/kg; p = .102).

CONCLUSIONS

Partial liquid ventilation with perflubron provides effective improvement in gas exchange in an adult animal model of respiratory failure.

Neonates with congenital diaphragmatic hernia: radiographic findings during partial liquid ventilation

PURPOSE

To determine the serial radiographic appearance of the lungs of neonates who underwent partial liquid ventilation with perflubron because of congenital diaphragmatic hernia (CDH) or primary pulmonary hypertension.

MATERIALS AND METHODS

Bedside anteroposterior (AP) and lateral chest radiographs (n = 235) were scored for percentage of lung opacification by perflubron during partial liquid ventilation (PLV) and extracorporeal membrane oxygenation (ECMO). Five neonates participated in the study; four had CDH, and one had primary pulmonary hypertension.

RESULTS

The lungs were opacified nearly completely after each dose of perflubron. The degree of opacification was the same on 117 of 169 (69%) AP radiographs and within one point on another 40 (24%). A gravity-dependent distribution was shown on 58 of 66 (88%) lateral radiographs. A minimal amount of perflubron remained in the lungs after 5.2 days. A hypoplastic bronchus and ipsilateral lung were manifest in all four of the patients with CDH after the airway and lung were filled with radiopaque perflubron.

CONCLUSION

Lungs filled with perflubron were opacified to a similar degree in a gravity-dependent distribution. Evaporation of perflubron from the lungs of neonates is relatively rapid. The size of the ipsilateral bronchus and lung may be estimated by comparison of radiographs taken before and after the lungs were filled with perflubron.

Measuring functional residual capacity in normal and oleic acid-injured lungs

Functional residual capacity (FRC) is an important oxygen reserve that is often depleted in acute respiratory failure. Recent interest in the mechanisms of liquid ventilation and limited experience in measuring FRC in paralyzed, mechanically ventilated, normal and lung-injured animal models have mandated development of accurate laboratory techniques. Eight sheep, from 17 to 27 kg, were anesthetized and instrumented to provide a tracheostomy, a pulmonary artery catheter, and carotid arterial line. They were randomized to two groups, one of which received 0.07 ml/kg of intravenous oleic acid to induce lung injury. Gas ventilation of both groups was identical except for respiratory rate, which was adjusted to normalize PaCO2. FRC was measured in duplicate by both helium dilution (HD) and body plethysmography (BP). When measurements were completed, the animals were euthanized and their endotracheal tubes clamped at end expiration. The lungs were then removed and their water displacement (WD) FRC values were measured. FRC was the difference between WD and tissue weight assuming 1 ml = 1g. Pearson's correlation coefficient (R(2)) was calculated. During in vitro measurement of test lungs, HD had an R(2) value of 0.99 and BP had an R(2) value of 0.98. When compared to WD, in vivo measurement of FRC by HD had an R(2) value of 0.94 while the value for BP was 0.97. In conclusion, both HD and BP are accurate methods of determining FRC in an uninjured and injured lung model when compared to postmortem WD. Documenting changes in FRC will aid in elucidating the mechanisms of alternative ventilatory techniques.

Evaluation of gas exchange, pulmonary compliance, and lung injury during total and partial liquid ventilation in the acute respiratory distress syndrome

OBJECTIVE

To investigate whether pulmonary compliance and gas exchange will be sustained during "total" perfluorocarbon liquid ventilation followed by "partial" perfluorocarbon liquid ventilation when compared with gas ventilation in the setting of the acute respiratory distress syndrome (ARDS).

STUDY DESIGN

A prospective, controlled, laboratory study.

SETTING

A university research laboratory.

SUBJECTS

Ten sheep, weighing 12.7 to 25.0 kg.

INTERVENTIONS

Lung injury was induced in ten young sheep, utilizing a right atrial injection of 0.07 mL/kg of oleic acid followed by saline pulmonary lavage. Bijugular venovenous extracorporeal life support access, a pulmonary artery catheter, and a carotid artery catheter were placed. When the alveolar-arterial O2 gradient was >/= 600 torr and PaO2 </= 50 torr (</= 6.7 kPa) with an FIO2 of 1.0, extracorporeal life support was instituted. For the first 30 mins on extracorporeal life support, all animals were ventilated with gas. Animals were then ventilated with equal tidal volumes of 15 mL/kg during gas ventilation (n=5) over the ensuing 2.5 hrs, or with total liquid ventilation for 1 hr, followed by partial liquid ventilation for 1.5 hrs (total/partial liquid ventilation, n=5).

MEASUREMENTS AND MAIN RESULTS

An increase in physiologic shunt (gas ventilation = 69 +/- 11%, total/partial liquid ventilation = 71 +/- 3%) and a decrease in static total pulmonary compliance measured at 20 mL/kg inflation volume (gas ventilation = O.48 +/- 0.03 mL/cm H2O/kg, total/partial liquid ventilation = 0.50 +/- 0.17 mL/cm H2O/kg) were observed in both groups with induction of lung injury. Physiologic shunt was significantly reduced during total and partial liquid ventilation when compared with physiologic shunt observed in the gas ventilation animals (gas ventilation = 93 +/- 8%, total liquid ventilation = 45 +/- 11%, p<.001; gas ventilation = 95 +/- 3%, partial liquid ventilation = 61 +/- 12%, p<.001), while static compliance was significantly increased in the total, but not the partial liquid ventilated animals when compared with the gas ventilated group (gas ventilation = 0.43 +/- 0.03 mL/cm H2O/kg, total liquid ventilation = 1.13 +/- 18 mL/cm H2O/kg, p <.001; gas ventilation = 0.41 +/- 0.02 mL/cm H2O/kg, partial liquid ventilation = 0.47 +/- 0.08, p = .151). In addition, the extracorporeal life support flow rate required to maintain adequate oxygenation was significantly lower in the total/partial liquid ventilation group when compared with that of the gas ventilation group (gas ventilation = 89 +/- 7 mL/kg/min, total liquid ventilation = 22 +/- 10 mL/kg/min, p <.001; gas ventilation = 91 +/- 12 mL/kg/min, partial liquid ventilation = 41 +/- 11 mL/kg/min, p < .001). Lung biopsy light microscopy demonstrated a marked reduction in alveolar hemorrhage, lung fluid accumulation, and inflammatory infiltration in the total/partial liquid ventilation animals when compared with the gas ventilation animals.

CONCLUSIONS

In a model of severe ARDS, pulmonary gas exchange is improved during total followed by partial liquid ventilation. Pulmonary compliance is improved during total, but not during partial liquid ventilation. Total followed by partial liquid ventilation was associated with a reduction in alveolar hemorrhage, pulmonary edema, and lung inflammatory infiltration.

Partial liquid ventilation in newborn patients with congenital diaphragmatic hernia

The authors evaluated the safety and efficacy of liquid ventilation with perfluorocarbon in four newborns with congenital diaphragmatic hernia and severe respiratory failure, who were on extracorporeal life support (ECLS). After 2 to 5 days on the ECLS, perflubron was administered into the trachea until the dependent zone of the lung was filled. The first dose was 6 +/- 1 mL/kg (range, 5 to 8 mL/kg). Gas ventilation of the perflubron-filled lung was performed (partial liquid ventilation). The administration of perflubron was repeated daily for 5 to 6 days, with total cumulative doses of 36 +/- 8 mL/kg (range, 26 to 44 mL/kg). A significant increase in PaO(2) (P = .027 by repeated-measures analysis of variance [ANOVA]), a trend toward an increase in arterial oxygen content (P = .052 by repeated-measures ANOVA), and a significant increase in specific static total pulmonary compliance (P = .007 by repeated-measures ANOVA) were observed after administration of the daily dose of perflubron. PaCO(2) data showed a decreasing trend (P = .08 by repeated measures ANOVA). The authors conclude that perflubron can be safely administered into the lungs of newborn patients with congenital diaphragmatic hernia and severe respiratory failure, and it may be associated with improvement in gas exchange and pulmonary compliance.

Successful management of a chylothorax in infancy using a pleurectomy

The management of chylothorax is described in three infants. Because none of them had had a direct injury to the thoracic duct, it was suspected that the chylothoraces had a significant chance of recurrence after simple ligation of the duct. To avoid recurrence, formal stripping of the parietal pleura was performed using a technique not previously reported in the literature. The operation was simple to perform and resulted in resolution of the chylothorax in all infants. The three cases and details of the surgical procedure are described.