Comparison of two methods of surfactant administration and the effect on dosing-associated hypoxemia.

OBJECTIVE: The purpose of our study was to test the hypothesis that surfactant dosing through a proximal sideport adapter on an endotracheal tube leads to more dosing-associated hypoxemia compared with a method of dosing that uses a double-lumen endotracheal tube. STUDY DESIGN: Using adequate sample size to compare significant changes in O2 saturation (power > 0.8, alpha < 0.05) we enrolled 36 infants with respiratory distress syndrome in this randomized trial. A 10% change in O2 saturation was considered clinically significant. Nineteen infants received 38 doses of surfactant through the sideport adapter. Seventeen infants received 31 doses of surfactant through the nonventilation lumen of a double-lumen endotracheal tube. Two main outcome measures were assessed: time-averaged O2 saturation values 30 minutes after dosing and the largest absolute fall in O2 saturation for each patient. RESULTS AND CONCLUSIONS: Time-averaged O2 saturation measures were higher in the proximal sideport group (p = 0.02), but the magnitude of difference was probably not clinically significant. No significant difference was detected between groups when we compared largest absolute drop in O2 saturation. Secondary analyses found no effect of birth weight or dose number (second vs third dose) on either outcome measure.

Flow-synchronized ventilation of preterm infants with respiratory distress syndrome.

Asynchrony of delivered and spontaneous breaths in mechanically ventilated infants may impair gas exchange and prolong the need for assisted ventilation. We conducted a randomized, controlled trial of a patient-triggered, flow-synchronized ventilator on 30 preterm infants with respiratory distress syndrome who weighed between 1100 and 1500 gm at birth. Entry criteria included radiographic evidence of respiratory distress syndrome and the need for mechanical ventilation and surfactant replacement therapy. Patients were assigned to either conventional time-cycled, pressure-limited ventilation or patient-triggered, flow-synchronized ventilation in an assist/control mode. Otherwise clinical management was identical. Time to extubation was the primary outcome measure. Patients treated with flow-synchronized ventilation were weaned more rapidly and had a significantly shorter mean time to extubation than those treated with time-cycled, pressure-limited ventilation, 119 versus 271 hours, p = 0.0152. In addition, there was no difference in the rate of complications between the two groups. There were, however, considerable reductions in patient charges of $4344 per patient in the flow-synchronized ventilation group.

Volume-controlled ventilation for severe neonatal respiratory failure.

Volume-controlled ventilation was utilized as a rescue modality in six newborn infants with severe respiratory failure. Infants were switched from time-cycled, pressure-limited ventilation to volume-controlled ventilation at 10-12 mL/kg using the VIP-Bird infant ventilator. All six displayed dramatic improvements in oxygenation with virtually no change in mean airway pressure and with subsequent resolution of the respiratory failure. Preliminary analysis of pulmonary function during volume-controlled ventilation suggests differences in the patterns of delivery of tidal volume and minute ventilation, which are more consistent. This may improve stabilization of lung volume and decrease ventilation-perfusion mismatch.

Tracheobronchial and pulmonary histopathology following conventional and high-frequency jet ventilation.

The advent of high-frequency jet ventilation (HFJV) as an alternative method of respiratory support for newborns has been implicated as a causative agent of necrotizing tracheobronchitis (NTB). We conducted a controlled trial of prolonged HFJV and conventional mechanical ventilation (CMV) in adult cats to determine effects on airway injury related to mode of ventilation and placement of the jet injector (proximal vs distal trachea). Fifteen cats were randomly assigned to either high-frequency positive pressure ventilation, proximal injection jet ventilation, or distal injection jet ventilation. The animals were ventilated for more than 33 hours. Post mortem, the trachea and respiratory tree were removed en bloc and fixed in formalin. A pathologist, unaware of the mode of ventilation, examined tracheobronchial histology and assigned scores using a technique previously described. Lung parenchymal tissue was also assessed using a similar grading system. Statistical analysis (Kruskal-Wallis analysis of variance) demonstrated no significant differences between tracheobronchial or lung parenchymal histopathology regardless of the mode of ventilation. We conclude that (1) the adult cat serves as a useful model for evaluating histopathologic effects of prolonged ventilation, (2) the etiology and pathogenesis of airway injury appears to be multifactorial, and the mode of ventilation is only one of many contributing variables, and (3) previously demonstrated differences between CMV and HFJV may be related to a much shorter duration of ventilation.

Adult respiratory distress syndrome in full-term newborns.

Since 1984, 11 newborns with severe respiratory distress have been treated whose clinical characteristics appear distinctive. Characteristics of these neonates were as follows: (1) they were full term by obstetric and neonatal criteria, (2) they had diffuse bilateral alveolar opacification on chest radiographs during the acute illness, (3) each had an acute perinatal triggering insult, (4) the neonates required continuous positive pressure ventilation for at least 48 hours with FiO2 greater than 0.50 for at least 12 hours, (5) they needed positive end-expiratory pressure of 6 cm of H2O or greater within three days of the triggering event, (6) there were no other known causes of these clinical conditions. Ten (91%) neonates had evidence of other organ dysfunction in addition to the lungs. Trials of hyperventilation in nine and tolazoline in five failed to improve oxygenation. Ten infants who underwent trials of increased positive end-expiratory pressure greater than or equal to 6 cm of H2O without other concurrent changes in ventilator settings responded with prompt increases in PaO2 (median increase 84 mm Hg, range 22 to 196 mm Hg). All 11 babies survived but required prolonged mechanical ventilation and supplemental oxygen. We suggest that adult respiratory distress syndrome can and does occur in newborns. A trial of positive end-expiratory pressure greater than or equal to 6 cm of H2O should be considered in full-term infants with severe respiratory distress in whom other causes can be excluded.

Lateral positioning of the stable ventilated very-low-birth-weight infant. Effect on transcutaneous oxygen and carbon dioxide.

Eighteen stable very-low-birth-weight (VLBW) mechanically ventilated infants with chronic lung disease were studied to examine the effects of right and left lateral positioning in contrast to supine positioning on transcutaneous (tc) oxygen (tcPO2) and carbon dioxide measurements (tcPCO2). The neonates were studied at a median postnatal age of 31 days (range, 17 to 57 days) and had median birth weights and gestational ages of 975 g (range, 570 to 1360 g) and 27.5 weeks (range, 24 to 30 weeks), respectively. Median fraction of inspiratory oxygen was 0.32 (range, 0.23 to 0.40). The sequence of study positions was randomly determined. Sleep state as well as tcPO2 and tcPCO2 were recorded every 30 s for five minutes. A significant difference in mean tcPO2 or tcPCO2 was not detected for any of the positions. Lateral positioning may facilitate the development of midline behavior in VLBW infants. Care givers are often reluctant to position infants in side lying, however, because of concerns that ventilation or oxygenation might be compromised. We conclude that placing the stable VLBW mechanically ventilated infant in a side-lying position has no deleterious effects on oxygenation and ventilation, as measured by tcPO2 and tcPCO2, and therefore should be encouraged.

A comparison of proximal and distal high-frequency jet ventilation in an experimental animal model.

High-frequency jet ventilation using either a proximal or a distal endotracheal injection site through a triple-lumen endotracheal tube was studied in 10 adult cats. The comparative effects on pulmonary gas exchange, tracheal pressure, heart rate, and blood pressure were examined for each injection site at both high (8-12 pounds per square inch [PSI] and low (5-8 PSI) jet-driving pressures in normal and lung-injured cats. Lung injury was created by modification of a surfactant washout technique previously demonstrated in rabbits. Alveolar ventilation (PaCO2) was found to be significantly better with distal than with proximal jet injection under all experimental conditions. At high jet-driving pressures, peak inspiratory pressure was higher in both normal (p = 0.03) and lung-injured cats (p = 0.002) with distal high-frequency jet ventilation. In addition, lung-injured animals were observed to have higher distal mean airway pressures at high jet-driving pressures (p less than 0.01). No differences in oxygenation were found in any circumstances. The results of this animal study suggest that distal high-frequency jet ventilation may be more effective in those situations in which improvement in alveolar ventilation is the major goal and that during proximal high-frequency jet ventilation airway pressures should be monitored as far distally as possible.

Proximal high-frequency jet ventilation of the newborn.

During a 14-month period 11 preterm infants were treated with high-frequency jet ventilation for severe respiratory failure that had been unresponsive to conventional mechanical ventilation. Primary indications included intractable air leaks (pulmonary interstitial emphysema, pneumothorax, or both), congenital diaphragmatic hernia, and progressive pneumonia. The Sechrist 990 HFV respirator, a solenoid-driven, pulse-generated high frequency jet ventilator, was used. This device delivers a volume of gas at a controlled pressure to a jet located in the patient connector proximal to a standard single lumen endotracheal tube. The ventilator was operated in tandem with a Sechrist IV-100B ventilator to provide a sigh effect and to improve humidification. Although only 3 of 11 patients survived, 9 displayed short-term benefits from HFJV with significant reduction in mean airway pressure and improvement in mean arterial blood pressure, and no concomitant adverse effects on oxygenation or ventilation. Preliminary results suggest short-term benefits of HFJV in infants who have severe respiratory failure that is unresponsive to conventional mechanical ventilation.