Aeration strategy at birth influences the physiological response to surfactant in preterm lambs

BACKGROUND

The influence of pressure strategies to promote lung aeration at birth on the subsequent physiological response to exogenous surfactant therapy has not been investigated.

OBJECTIVES

To compare the effect of sustained inflation (SI) and a dynamic positive end-expiratory pressure (PEEP) manoeuvre at birth on the subsequent physiological response to exogenous surfactant therapy in preterm lambs.

METHODS

Steroid-exposed preterm lambs (124-127 days' gestation; n=71) were randomly assigned from birth to either (1) positive-pressure ventilation (PPV) with no recruitment manoeuvre; (2) SI until stable aeration; or (3) 3 min dynamic stepwise PEEP strategy (maximum 14-20 cmH₂O; dynamic PEEP (DynPEEP)), followed by PPV for 60 min using a standardised protocol. Surfactant (200 mg/kg poractant alfa) was administered at 10 min. Dynamic compliance, gas exchange and regional ventilation and aeration characteristics (electrical impedance tomography) were measured throughout and compared between groups, and with a historical group (n=38) managed using the same strategies without surfactant.

RESULTS

Compliance increased after surfactant only in the DynPEEP group (p<0.0001, repeated measures analysis of variance), being 0.17 (0.10, 0.23) mL/kg/cmH₂O higher at 60 min than the SI group. An SI resulted in the least uniform aeration, and unlike the no-recruitment and DynPEEP groups, the distribution of aeration and tidal ventilation did not improve with surfactant. All groups had similar improvements in oxygenation post-surfactant compared with the corresponding groups not treated with surfactant.

CONCLUSIONS

A DynPEEP strategy at birth may improve the response to early surfactant therapy, whereas rapid lung inflation with SI creates non-uniform aeration that appears to inhibit surfactant efficacy.

Lung volume and cardiorespiratory changes during open and closed endotracheal suction in ventilated newborn infants

OBJECTIVES

To compare change in lung volume (DeltaV(L)), using respiratory inductive plethysmography, time to recover pre-suction lung volume (t(rec)) and the cardiorespiratory disturbances associated with open suction (OS) and closed suction (CS) in ventilated infants.

DESIGN

Randomised blinded crossover trial.

SETTING

Neonatal intensive care unit.

PATIENTS

Thirty neonates, 20 receiving synchronised intermittent mandatory ventilation (SIMV) and 10 high-frequency oscillatory ventilation (HFOV, four receiving muscle relaxant).

INTERVENTIONS

OS and CS were performed, in random order, on each infant using a 6FG catheter at -19 kPa for 6 seconds and repeated after 1 minute.

OUTCOME MEASURES

DeltaV(L), oxygen saturation (Spo(2)) and heart rate were continuously recorded from 2 minutes before until 5 minutes after suction. Lowest values were identified during the 60 seconds after suction.

RESULTS

Variations in all measures were seen during CS and OS. During SIMV no differences were found between OS and CS for maximum DeltaV(L) or t(rec); mean (95% CI) difference of 3.5 ml/kg (-2.8 to 9.7) and 4 seconds (-5 to 13), respectively. During HFOV t(rec) was longer during OS by 13 seconds (0 to 27) but there was no difference in the maximum DeltaV(L) of 0.1 mV (-0.02 to 0.22). A small reduction in SpO(2) with CS in the SIMV group mean difference 6% (2.1 to 9.8) was the only significant difference in physiological measurements.

CONCLUSIONS

Both OS and CS produced transient variable reductions in heart rate and Spo(2). During SIMV there was no difference between OS and CS in DeltaV(L) or t(rec). During HFOV there was no difference in DeltaV(L) but a slightly longer t(rec) after OS.

Neonatal volume guarantee ventilation: effects of spontaneous breathing, triggered and untriggered inflations

BACKGROUND

During volume guarantee (VG) ventilation the peak inflating pressure (PIP) for each ventilator inflation is adjusted to ensure the expired tidal volume (V(Te)) is close to the set V(Te). Differences in the PIP between inflations triggered by the infant's inspirations and untriggered inflations are seen.

AIM

To investigate the effects of triggered and untriggered inflations on PIP and V(Te).

METHODS

Neonates were ventilated with the Dräger Babylog 8000 using assist control (synchronous intermittent positive pressure ventilation) and VG modes. Continuous recordings of ventilator pressures and tidal volumes were made at 200 Hz for 10 minutes.

RESULTS

In 10 infants, 6540 inflations were analysed, of which 4052 (62%) were triggered. Triggered inflations had a significantly lower mean (SD) PIP than untriggered inflations: 12.9 (4.9) vs 17.0 (3.3) cm H2O, (p<0.001). Despite this, there was no significant difference in the V(Te) of each type of inflation (103% and 101% of the set V(Te), respectively). When a triggered inflation was immediately preceded or followed by an untriggered inflation the PIP changed by about 5 cm H2O. Between adjacent inflations of the same type, the change in PIP was less than 3 cm H2O: for triggered inflations it was 0.11 (1.50) cm H2O and for untriggered inflations 0.06 (1.53) cm H2O.

CONCLUSION

During VG ventilation with the Dräger Babylog 8000 the PIP was 4 cm H2O lower during triggered inflations than untriggered inflations, although the expired tidal volumes were similar.

Effects of open endotracheal suction on lung volume in infants receiving HFOV

OBJECTIVE

To describe the pattern and magnitude of lung volume change during open endotracheal tube (ETT) suction in infants receiving high-frequency oscillatory ventilation (HFOV).

DESIGN

Prospective observational clinical study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS AND PARTICIPANTS

Seven intubated and muscle-relaxed newborn infants receiving HFOV.

INTERVENTIONS

Open ETT suction was performed for 6 s at -100 mmHg using a 6-F catheter passed to the ETT tip after disconnection from HFOV. The HFOV was then recommenced at the same settings as prior to ETT suction.

MEASUREMENTS AND RESULTS

Change in lung volume (DeltaV (L)) referenced to baseline lung volume before suction was measured with a calibrated respiratory inductive plethysmography recording from 30 s before until 60 s after ETT suction. In all infants ETT suction resulted in significant loss of lung volume. The mean DeltaV (L) during suctioning was -13 ml/kg (SD 4 ml/kg) (p<0.0001 vs. baseline, repeated-measures ANOVA), with a mean 76.5% (SD 14.1%) of this volume loss being related to circuit disconnection. After recommencing HFOV lung volume was rapidly regained with mean DeltaV (L) at 60 s being 1 ml/kg (SD 4 ml/kg) below baseline (p>0.05, Tukey post-test).

CONCLUSIONS

Open ETT suction caused a significant but transient loss of lung volume in muscle-relaxed newborn infants receiving HFOV.

Death in the neonatal intensive care unit: changing patterns of end of life care over two decades

BACKGROUND

Death remains a common event in the neonatal intensive care unit, and often involves limitation or withdrawal of life sustaining treatment.

OBJECTIVE

To document changes in the causes of death and its management over the last two decades.

METHODS

An audit of infants dying in the neonatal intensive care unit was performed during two epochs (1985-1987 and 1999-2001). The principal diagnoses of infants who died were recorded, as well as their apparent prognoses, and any decisions to limit or withdraw medical treatment.

RESULTS

In epoch 1, 132 infants died out of 1362 admissions (9.7%), and in epoch 2 there were 111 deaths out of 1776 admissions (6.2%; p<0.001). Approximately three quarters of infants died after withdrawal of life sustaining treatment in both epochs. There was a significant reduction in the proportion of deaths from chromosomal abnormalities, and from neural tube defects in epoch 2.

CONCLUSIONS

There have been substantial changes in the illnesses leading to death in the neonatal intensive care unit. These may reflect the combined effects of prenatal diagnosis and changing community and medical attitudes.

Hemodynamic disturbances associated with endovascular embolization in newborn infants with vein of Galen malformation

OBJECTIVE

To examine hemodynamic changes following endovascular embolization in newborn infants with vein of Galen malformation and severe cardiac failure in the first week of life.

STUDY DESIGN

Over a recent 5-year period, nine such infants were identified. In seven of these infants, changes in arterial blood pressure were analyzed in relation to the timing of embolization procedures.

RESULTS

A significant increase in arterial blood pressure was noted after most embolizations. In two infants, this systemic hypertension was severe and treated using intravenous antihypertensive drugs. Both infants subsequently developed complete infarction of both cerebral hemispheres with sparing of the brainstem and cerebellum. Mortality in the nine infants was 33%, and 83% of the survivors were neurologically normal or near normal at follow-up.

CONCLUSION

The systemic hypertension observed following endovascular embolizations may provide a protective mechanism to maintain cerebral blood flow after reperfusion injury. Lowering blood pressure in this situation may therefore be detrimental.

Neonatal resuscitation 2: an evaluation of manual ventilation devices and face masks

BACKGROUND

The key to successful neonatal resuscitation is effective ventilation. Little evidence exists to guide clinicians in their choice of manual ventilation device or face mask. The expiratory tidal volume measured at the mask (V(TE(mask))) is a good estimate of the tidal volume delivered during simulated neonatal resuscitation.

AIM

To compare the efficacy of (a) the Laerdal infant resuscitator and the Neopuff infant resuscitator, used with (b) round and anatomically shaped masks in a model of neonatal resuscitation.

METHODS

Thirty four participants gave positive pressure ventilation to a mannequin at specified pressures with each of the four device-mask combinations. Flow, inspiratory tidal volume at the face mask (V(TI(mask))), V(TE(mask)), and airway pressure were recorded. Leakage from the mask was calculated from V(TI(mask)) and V(TE(mask)).

RESULTS

A total of 10,780 inflations were recorded and analysed. Peak inspiratory pressure targets were achieved equally with the Laerdal and Neopuff resuscitators. Positive end expiratory pressure was delivered with the Neopuff but not the Laerdal device. Despite similar peak pressures, V(TE(mask)) varied widely. Mask leakage was large for each combination of device and mask. There were no differences between the masks.

CONCLUSION

During face mask ventilation of a neonatal resuscitation mannequin, there are large leaks around the face mask. Airway pressure is a poor proxy for volume delivered during positive pressure ventilation through a mask.

Neonatal resuscitation 3: manometer use in a model of face mask ventilation

BACKGROUND

Adequate ventilation is the key to successful neonatal resuscitation. Positive pressure ventilation (PPV) is initiated with manual ventilation devices via face masks. These devices may be used with a manometer to measure airway pressures delivered. The expiratory tidal volume measured at the mask (V(TE(mask))) is a good estimate of the tidal volume delivered during simulated neonatal resuscitation.

AIM

To assess the effect of viewing a manometer on the peak inspiratory pressures used, the volume delivered, and leakage from the face mask during PPV with two manual ventilation devices in a model of neonatal resuscitation.

METHODS

Participants gave PPV to a modified resuscitation mannequin using a Laerdal infant resuscitator and a Neopuff infant resuscitator at specified pressures ensuring adequate chest wall excursion. Each participant gave PPV to the mannequin with each device twice, viewing the manometer on one occasion and unable to see the manometer on the other. Data from participants were averaged for each device used with the manometer and without the manometer separately.

RESULTS

A total of 7767 inflations delivered by the 18 participants were recorded and analysed. Peak inspiratory pressures delivered were lower with the Laerdal device. There were no differences in leakage from the face mask or volumes delivered. Whether or not the manometer was visible made no difference to any measured variable.

CONCLUSIONS

Viewing a manometer during PPV in this model of neonatal resuscitation does not affect the airway pressure or tidal volumes delivered or the degree of leakage from the face mask.

Volume guarantee ventilation, interrupted expiration, and expiratory braking

BACKGROUND

In volume guarantee ventilation with the Dräger Babylog 8000 ventilator, inspiratory and expiratory flows are monitored and the expiratory tidal volume calculated following each inflation. The pressure for the next inflation is modified to ensure the expired tidal volume is close to the set value.

AIM

To investigate interrupted expiration observed during volume guarantee ventilation of spontaneously breathing, ventilated infants.

METHODS

Spontaneously breathing infants, ventilated with volume guarantee, had recordings of gas flow, ventilator pressures, tidal volume waveforms, oximetry, heart rate, and transcutaneous oxygen and carbon dioxide during 10 minute recordings.

RESULTS

A total of 6540 inflations were analysed from 10 infants; 62% were triggered. Two different patterns were found: (1) Normal volume guarantee pattern with 97% of triggered and 91% untriggered inflations. It had a normal expiratory curve and a mean expired tidal volume within 3% of the set volume, but a large variation due to the babies' breathing. (2) A pattern of interrupted expiratory flow after approximately 3% of inflations due to a small inspiration (approximately 1.3 ml/kg) during expiration. This led the ventilator to calculate an inappropriate total expired tidal volume for that inflation and an increase in the pressure for the next inflation.

CONCLUSIONS

After about 3% of inflations, with volume guarantee ventilation, interruption of the expiration causes an increased pressure for the next inflation of approximately 4.9 cm H2O, compared with normal volume guarantee inflation. The interrupted expiration is most likely to be due to diaphragmatic braking.

Clinical course and medical management of neonates with severe cardiac failure related to vein of Galen malformation

BACKGROUND

Neonatal presentation of vein of Galen aneurysmal malformations (VGAMs) with intractable cardiac failure is considered a poor prognostic sign. Interventional neuroradiology with embolisation has been shown to control cardiac failure, but there is a perception that neurological outcome in survivors is poor.

OBJECTIVE

To determine if aggressive intensive care and anaesthetic management of cardiac failure before urgent embolisation can influence morbidity and mortality.

PATIENTS

Nine newborns (four boys, five girls) were diagnosed with symptomatic vein of Galen malformations in the neonatal period during the period 1996-2001. Eight developed intractable high output cardiac failure requiring initial endovascular treatment in the first week of life.

RESULTS

The immediate outcome after a series of endovascular procedures was control of cardiac failure and normal neurological function in six (66%) patients, one death from intractable cardiac failure in the neonatal period, and two late deaths with severe hypoxic-ischaemic neurological injury (33% mortality). Clinical review at 6 months to 4 years of age showed five infants with no evidence of neurological abnormality or cardiac failure and one child with mild developmental delay (11%).

CONCLUSIONS

Aggressive medical treatment of cardiac failure and early neurointervention combined with modern neuroanaesthetic care results in good survival rates with low morbidity even in cases of high risk VGAM presenting in the immediate perinatal period with cardiac failure. Systemic arterial vasodilators improve outcome in neonates with cardiac failure secondary to VGAM. Excessive beta adrenergic stimulation induced by conventional inotropic agents may exacerbate systemic hypoperfusion.

Left-lung-collapse bronchial deformation in giant omphalocele

Five infants with giant omphalocele had persistent collapse of the left lung and required prolonged respiratory support. Narrowing of the left main bronchus, reversible with positive end-expiratory pressure, was identified radiographically in 3 infants, and we postulate that this relates to distortion of the bronchus within the constraints of the elongated, narrow thoracic cavity characteristic of these patients. The lung collapse may be precipitated by manipulation (reduction or attempted reduction) of the omphalocele. J Pediatr Surg 36:846-850.

Upper cervical spinal cord injury in neonates: the use of magnetic resonance imaging

Neonatal upper cervical spinal cord injury is associated with rotational forceps delivery and presents with quadriparesis and diaphragmatic paralysis. The underlying pathology determines neurologic outcome but is difficult to assess clinically or with simple radiographic techniques. We report 4 cases in which early magnetic resonance imaging demonstrated the extent and severity of the injury and guided management.

Surfactant and surfactant inhibitors in meconium aspiration syndrome

Surfactant indices and inhibitors were measured in lung lavage fluid from 8 infants with meconium aspiration syndrome (MAS) who were receiving mechanical ventilation and 11 healthy control subjects. Surfactant phospholipid and surfactant protein A content in MAS was not different from that of control subjects, but concentrations of total protein, albumin, and membrane-derived phospholipid were elevated. All infants with MAS had hemorrhagic pulmonary edema. These findings reinforce the notion of MAS as a toxic pneumonitis with epithelial disruption and proteinaceous exudation.

Overcoming surfactant inhibition with polymers

Inhibition of the function of pulmonary surfactant in the alveolar space is an important element of the pathophysiology of many lung diseases, including meconium aspiration syndrome, pneumonia and acute respiratory distress syndrome. The known mechanisms by which surfactant dysfunction occurs are (a) competitive inhibition of phospholipid entry into the surface monolayer (e.g. by plasma proteins), and (b) infiltration and destabilization of the surface film by extraneous lipids (e.g. meconium-derived free fatty acids). Recent data suggest that addition of non-ionic polymers such as dextran and polyethylene glycol to surfactant mixtures may significantly improve resistance to inhibition. Polymers have been found to neutralize the effects of several different inhibitors, and can produce near-complete restoration of surfactant function. The anti-inhibitory properties of polymers, and their possible role as an adjunct to surfactant therapy, deserve further exploration.

Validity of markers of dilution in small volume lung lavage

Definitive analysis of solute concentrations in lung lavage fluid involves the use of a marker of dilution to correct for variable recovery of epithelial lining fluid (ELF), but the question of the most appropriate dilutional marker remains unresolved. In lavage fluid collected from infants with lung disease and healthy control subjects, we examined ELF concentration of protein, albumin, sphingomyelin (SM), and IgA secretory component (SC), and critically appraised the relative validity of SC and urea as dilutional markers in the context of lung infection and lung injury. Protein, albumin, and SM were found not to be valid dilutional markers, as their ELF concentration varied significantly between the diseased, recovering, and normal lung. Differences in concentration were noted in both tracheal aspirate samples (TA, 4 x 0.5 ml) and nonbronchoscopic bronchoalveolar lavage fluid (NB-BAL, 3 x 1 ml/kg), but were not uniform (e.g., TA-disease versus control: albumin 2.8 versus 0.68 mg/ml, SM 45 versus 16 microgram/ml, both p < 0.05; NB-BAL-disease versus recovery: protein 8.1 versus 4.8 mg/ml, albumin 2.9 versus 1. 4 mg/ml, both p < 0.05). Overall, SC concentrations in ELF were not different between the diseased and normal lung, but in the NB-BAL samples, significantly higher SC concentration was noted in viral bronchiolitis and pneumonia than in noninfective lung diseases. No clear evidence of additional influx of urea into lavage fluid in association with epithelial disruption was found in the diseased lung. Comparative analysis of SC and urea revealed no difference in TA samples, but in NB-BAL specimens, urea best standardized the lavage concentration of surfactant indices to correspond to the degree of lung dysfunction as indicated by oxygenation index. We conclude that SC and urea, but not protein, albumin, or SM, are valid dilutional markers with which to estimate ELF recovery during small volume lung lavage. Urea appears a more appropriate choice in return fluid derived from the distal tracheobronchial tree, and SC should not be used in the context of lung infection.

Comparison of two methods of diagnostic lung lavage in ventilated infants with lung disease

The methods of nonbronchoscopic lung lavage used for collection of samples of epithelial lining fluid (ELF) in intubated patients are poorly standardized and incompletely validated. In infants with lung disease requiring ventilatory support, we evaluated two techniques of small volume saline lavage for the collection of a specimen suitable for pulmonary surfactant analysis. We aimed to compare apparent origin of the return fluid obtained by each method, equivalence and agreement of the estimates of measured pulmonary surfactant concentration, and the relative strength of association between surfactant indices and lung dysfunction. Fifty-three contemporaneous paired samples of lung lavage fluid suitable for surfactant analysis were collected from 31 infants using tracheal aspirate (TA, 4 x 0.5 ml saline), and then nonbronchoscopic bronchoalveolar lavage (NB-BAL, 3 x 1 ml/kg). Return fluid from TA had higher mean ELF concentration of total protein and IgA secretory component (SC), and a lower surfactant protein A (SP-A) concentration than NB-BAL, indicating that the TA lavage was sampling ELF more proximally in the tracheobronchial tree (protein: TA 7.7 versus NB-BAL 4.7 mg/ml; SC: 21 versus 1.8 microgram/ml; SP-A: 9.8 versus 19 microgram/ml; all p < 0.01). Mean concentration of surfactant indices in ELF differed only for SP-A, but for all indices, paired values showed poor agreement on Bland-Altman analysis, highlighting the potential imprecision associated with small volume lung lavage. TA return fluid yielded estimates of surfactant indices which were at least equivalent to NB-BAL in prediction of the severity of lung dysfunction. We conclude that NB-BAL return fluid has more distal origin, but analysis of TA fluid may have equal validity in the estimation of indices of pulmonary surfactant. The results of individual estimates of ELF constituents in a single sample of lavage fluid should be interpreted with caution, even when standardized sampling techniques are employed.

Functional and compositional changes in pulmonary surfactant in response to exercise

Pulmonary surfactant from bronchoalveolar lavages was obtained from 2 groups of horses. A control group consisting of 6 healthy racehorses that were paddock-rested and lavaged weekly for 6 consecutive weeks were compared with an experimental group of 10 healthy racehorses, lavaged weekly the same period, consisting of a 5 week incremental-intensity treadmill training programme and one week post training paddock rest. Phospholipid content of lavage fluid was determined indirectly by phosphorus assay, and surfactant functional activity was determined by bubble surfactometry. Total cell counts and differential cell percentages of lavage fluid were adjusted to reflect the dilution of alveolar epithelial lining fluid (ELF) using the lavage/serum urea ratio, and data were analysed per volume of ELF. There was no change in phospholipid content for either group, but some horses had consistently greater amounts than did others, ranging from 17.2-64.4 micrograms/microliter. From the exercised group ELF had both increased nucleated cell numbers due to increased macrophage numbers, and increased numbers of erythrocytes. Surface tension increased significantly over the exercise protocol, but not in controls. Functional activity of surfactant varied between horses, independent of phospholipid content, with average values for individuals ranging 10.5-29.5 mN/m. We conclude that exercise of sufficient intensity to induce intrapulmonary haemorrhage also leads to functional decrease in surfactant activity, without affecting phospholipid content. This study also indicates that functional differences in surfactant exist between horses and may be a risk factor for development of exercise-induced pulmonary haemorrhage.

Overdose of ergometrine in the newborn infant: acute symptomatology and long-term outcome

OBJECTIVE

To document the short- and long-term effects of accidental administration of ergometrine in adult dosage to the newborn infant.

METHODS

The case records of all infants admitted to the Royal Children's Hospital (RCH) since 1970 with a diagnosis of acute ergometrine overdose were reviewed, and details of the acute symptomatology, management, and the neurodevelopmental outcome at follow-up were noted. Similar information was obtained, where available, from previous case reports, and from two major drug information services. Additionally, data relating to administration of uterotonic agents and vitamin K were collected from tertiary perinatal centres around Australia.

RESULTS

Seven cases of neonatal ergometrine overdose were identified at RCH. The major features of the acute toxicity syndrome were: encephalopathy (100% RCH cases, 79% combined cases); seizures (100%, 70%); peripheral vascular disturbances (100%, 83%); and oliguria (43%, 34%). Other important symptoms were hypoxaemia, hypertension and feed intolerance. 86% of RCH cases (72% overall) required ventilatory support. Virtually all symptoms resolved within 4 days, and 86% of RCH infants (86% all cases) were neurologically intact at the time of discharge. Long-term neurodevelopmental outcome was normal in 100% of RCH infants (n=6). All the perinatal centres surveyed give vitamin K in the labour ward soon after delivery, and 7 of 18 (39%) reported using Syntometrine (ergometrine 0.5 mg, Syntocinon 5 IU) routinely during the third stage of labour. Thus the circumstances in which ergometrine overdose can occur still exist in many labour wards around the country.

CONCLUSIONS

Despite the catastrophic initial presentation, the long-term prognosis after neonatal ergometrine overdose appears to be favourable. To prevent further cases of this life-threatening drug error, we recommend that administration of vitamin K be deferred until just prior to, or shortly after, transfer of the newborn infant to the postnatal ward.

Pulmonary surfactant concentration during transition from high frequency oscillation to conventional mechanical ventilation

OBJECTIVE

To test the hypothesis that conventional mechanical ventilation (CV) provides a greater stimulus to secretion of pulmonary surfactant than high frequency oscillatory ventilation (HFO).

METHODOLOGY

Sequential examination of surfactant indices in lung lavage fluid in a group of six infants with severe lung disease (group 1), ventilated with HFO and then converted back to CV as their lung disease recovered. A similar group of 10 infants (group 2) ventilated conventionally throughout the course of their illness were studied for comparison. In groups 1 and 2, two sequential tracheal aspirate samples were taken, the first once lung disease was noted to be improving, and the second 48-72 h later. Group 1 infants had converted from HFO to CV during this time.

RESULTS

A marked increase in concentration of total surfactant phospholipid (PL) and disaturated phosphatidylcholine (DSPC) was seen in group 1 after transition from HFO to CV; the magnitude of this increase was significantly greater than that sequentially observed in group II (total PL: 9.4-fold increase in group 1 vs 1.8-fold in group 2, P = 0.006; DSPC: group 1 6.4-fold increase vs. group 2 1.7-fold, P = 0.02).

CONCLUSION

These findings suggest that intermittent lung inflation during CV produces more secretion of surfactant phospholipid than continuous alveolar distension on HFO, and raise the possibility that conservation and additional maturation of surfactant elements may occur when the injured lung is ventilated with HFO.

Surfactant abnormalities in infants with severe viral bronchiolitis

To determine whether abnormalities of pulmonary surfactant occur in infants with acute viral bronchiolitis, surfactant indices were measured in lung lavage fluid from 12 infants with severe bronchiolitis and eight infants without lung disease. Compared with controls, the bronchiolitis group showed deficiency of surfactant protein A (1.02 v 14.4 micrograms/ml) and disaturated phosphatidylcholine (35 v 1060 micrograms/ml) which resolved as the disease improved. Surfactant functional activity was also impaired (minimum surface tension 22 v 17 mN/m). These findings indicate that surfactant abnormalities occur in bronchiolitis, and may represent one of the pathophysiological mechanisms causing airway obstruction.