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PEDIATRICS Vol. 108 No. 3 September 2001, pp. 617-623
From the Department of Neonatology, Utah Valley Regional
Medical Center, Provo, Utah.
Objective. In a previous multicenter
controlled clinical trial, we randomly assigned surfactant-treated
premature newborns with moderate to severe respiratory distress
syndrome to early treatment with high-frequency oscillatory ventilation
(HFOV) or to conventional ventilation (CV). Compared with control
infants who were treated with CV, neonates who were treated with HFOV
using a strategy designed to recruit and maintain lung volume and
minimize oxygen exposure had clinical evidence of improved pulmonary
outcome and less lung injury. We report a follow-up study designed to
determine whether clinical differences persisted between these study
groups.
Methods. Patients were recruited from 81 survivors at 1 center (Provo, Utah) and evaluated for sociodemographic and health
history, growth, mental development, motor proficiency, and pulmonary
function.
Results. Eighty-seven percent of the cohort who originally
were assigned to treatment with HFOV (n = 36) or CV
(n = 33) were seen in follow-up at a mean age of 77 months (6.4 years). There were no differences in the frequency of
hospitalization, pulmonary illness, asthma, or disabilities. Growth,
verbal IQ, and motor development were appropriate for age and not
different between groups. Patients who initially were randomized to
treatment with CV showed pulmonary function evidence of decreased peak
expiratory flow, increased residual lung volume, and maldistribution of
ventilation.
Conclusion. Neurodevelopmental childhood outcome after
early intervention HFOV was normal and not different compared with
patients who were treated with CV. Surfactant replacement combined with
early HFOV using a lung recruitment strategy ameliorates the acute lung injury in respiratory distress syndrome that predisposes some preterm
infants to develop chronic lung disease.
ABSTRACT
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Abstract
Methods
Results
Discussion
Conclusion
References
In 1996, the Provo multicenter early high-frequency
oscillatory ventilation (HFOV) trial group published findings that were consistent with improvement in both acute and chronic lung injury for
premature neonates who were administered surfactant and then ventilated
with HFOV using a lung recruitment strategy for treatment of
respiratory distress syndrome (RDS).1 Control infants were
treated with surfactant and ventilated with time-cycled
pressure-limited conventional ventilation (CV). Baseline
arterial-to-alveolar oxygen ratios of 0.21 to 0.25 at study entry were
representative of moderate to severe RDS. During the nursery
hospitalization, the early HFOV treatment group also showed improved
cardiovascular stability, decreased patient care acuity (cost), and no
increase in neonatal-associated morbidity, including intracranial
hemorrhage.
There is little published information pertaining to the childhood
outcome of respiratory treatment strategies for preterm infants who
require ventilatory assistance for RDS. Only 3 reports that evaluated
children after enrollment in comparison controlled trials have been
identified. Two studies followed up on subgroups of children who had
been enrolled in surfactant trials,2,3 and 1 study
evaluated childhood outcome for patients who were treated at a
participating site of a high-frequency ventilation trial.4
Only 1 report suggested improvement in childhood pulmonary outcome
attributable to the RDS treatment strategy that was tested in the
respective controlled neonatal trial.3 Although
improvements in neonatal survival and neonatal morbidity have been
associated with new RDS treatment strategies, advantages beyond the
second year of life have not been well demonstrated.
The purpose of the present study was to determine whether clinical
differences between the HFOV and CV treatment groups of the Provo trial
persisted into childhood. Presented are growth, standardized mental and
motor proficiency evaluations, and screening pulmonary testing data
comparing survivors of the 2 neonatal treatment groups.
IRB Approval
The follow-up study protocol and informed consent were reviewed
and approved by the medical center's institutional review board before
start of the study.
Patient Population
Although all original study sites were recruited to participate
in this follow-up project, 2 of the 3 centers were unsuccessful in
locating or recalling study patients. Of the 125 neonates in the
original trial, 83 had been enrolled at the Provo, Utah, site. Forty-two of these infants were randomized to HFOV, and 41 were randomized to CV. There was 1 neonatal death in the CV group reported in the original trial and 1 infant in the HFOV group who died of sudden
infant death syndrome, leaving 81 survivors. All families of survivors
were located, and parental informed consent was obtained. The parents
were asked to complete health history and sociodemographic questionnaires for the time period since neonatal intensive care discharge.
Growth
Stature and weight were measured as part of the pulmonary
function evaluation. Expected growth values (50th percentile for age)
were interpreted from standard growth charts.5 Age was not
adjusted for degree of prematurity.
Mental and Motor Proficiency Testing
Mental proficiency was evaluated using the verbal and
performance components of the revised Wechsler Preschool and Primary Scale of Intelligence, or the Wechsler Scale for Children, third edition, as appropriate for age. The Bruininks-Oseretsky test was
chosen for evaluation of motor proficiency because it best matched the
age group of the study infants. The Wechsler scales were administered
by a child psychologist (M.S.), and the motor performance tests were
administered by a developmental occupational therapist (A.M.), both of
whom were unaware of a patient's original study group assignment. We
report standardized scores for verbal IQ and gross, fine, and combined
motor performance.
Pulmonary Function Testing
Pulmonary function testing was conducted using a whole-body
plethysmograph (Model 6200; SensorMedics Critical Care, Yorba Linda,
CA). Spirometry was performed for measurement of forced expiratory
flows and volumes. Pressure plethysmography was used to measure lung
volumes. The single-breath technique for measurement of carbon monoxide
diffusion was used to determine lung diffusing capacity and alveolar
volume. The ratio of alveolar volume (VA) to total lung capacity (TLC)
was used as an index of maldistribution of inspired air.6
Respiratory impedance, response to bronchodilation challenge, and
functional residual capacity by nitrogen washout were not measured. The
pulmonary technician who administered the pulmonary function evaluation
was not aware of a patient's initial randomization status. When a
series of acceptable measurements for sample averaging could not be
obtained, values that corresponded to the child's best effort were
chosen as data points. For standardization, we primarily used
"invariant" reference values corrected for vital capacity or TLC
found in Wang et al,7 Polgar and Promadhat,8
Helliesen et al,9 and Zapletal et al.10 The
lung diffusing capacity for carbon monoxide
(DLCO) reference equations from Giammona and
Daly11 were used and body surface area was calculated
using the formula of DuBois and DuBois.12
Statistical Analysis
Values are expressed as mean ± standard deviation (SD). A
standard deviation score (SDS) was used to normalize study data to
reference values. The SDS is defined as
( Neonatal Outcomes
Demographic and neonatal outcome parameters were similar between
HFOV and CV groups, except that neonates who were assigned to HFOV less
often had chronic lung disease at 30 days and abnormal hearing
screening at discharge (Table 1). In this
cohort of HFOV-treated patients, there were trends to decreased
neonatal morbidity for oxygen exposure, necrotizing enterocolitis, and intracranial hemorrhage compared with those originally treated with CV.
These findings are similar to those previously published for the
multicenter trial.1
TABLE 1
METHODS
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Abstract
Methods
Results
Discussion
Conclusion
References
-µo)/
o, where is the observed value and µo and
o are the mean and SD, respectively, for the
reference population.13 The SDS distribution is normal
with a mean of 0 and an SD of 1. When average values are plotted with
an error bar representing the 95% confidence limits of the mean,
statistical significance is indicated by bars that do not cross the 0 axis. Any pulmonary function values in excess of 3 SD from the mean
were considered errant and not included in the calculations. Group
comparisons of parametric data were analyzed by unpaired t
test, and nonparametric data were analyzed by the Wilcoxon 2-sample
test. Fisher's exact test was used for tabular data. Multivariate
logistic regression models using backward selection were applied to
investigate the influence of neonatal and sociodemographic factors on
childhood outcomes that differed. P 
.05 was
considered significant for all statistical tests.
RESULTS
Top
Abstract
Methods
Results
Discussion
Conclusion
References
Neonatal Outcomes of the Provo Cohort Survivors Seen in Follow-up
Follow-up Participation
Families were interviewed from October to November 1999, and patients were seen for evaluation from January to March 2000 during a 3-hour clinic visit. After the initial telephone interview, 1 family withdrew from the study and 1 family was lost to contact. Fifty-eight children were seen locally, and arrangements were made for independent evaluation of 11 patients who lived out of region or out of state. Five local patients failed to keep appointments, and 5 out-of-state patients were not able to be scheduled. Thus 87% (69 of 79) of patients who were available for study were seen for evaluation. Of these, 36 were from the HFOV study group and 33 were from the CV study group, corresponding to 56% (69 of 123) of the total known surviving patients randomized in the original trial.
Health History and Sociodemographics
Five families declined to complete the health questionnaire, yielding an overall questionnaire completion rate of 93%. The percentage of positive responses for the HFOV and the CV groups, respectively, were seizure disorder, 0% versus 3%; hearing problem, 3% versus 3%; need for vision correction, 18% versus 7%; use of locomotion aid, 3% versus 7%; history of asthma symptoms or treatment, 12% versus 23%; household exposure to cigarette smoke, 20% versus 6%; hospitalized since discharge from the neonatal intensive care unit, 35% versus 33%; hospitalized for respiratory illness, 18% versus 17%; hospitalized for respiratory syncytial viral disease, 6% versus 10%; ongoing health problems, 15% versus 20%; participation in an infant development program, 59% versus 50%; enrollment in school grades K to 2, 88% versus 87%; and, enrollment in special school program(s), 23% versus 31%. There were no intergroup differences in the health questionnaire response frequencies.
Two families did not complete the sociodemographic questionnaire, yielding an overall completion rate of 97%. The majority of parents, 94%, were white, and 5% were Hispanic. Nine percent of children had single parents, although only half of these were living alone. Ninety-five percent of mothers completed high school and 23% completed college, whereas 94% of fathers completed high school and 41% completed college. More than half of the mothers reported having part- or full-time employment (53%), whereas 97% of fathers reported the same. All families indicated owning an automobile; 86% owned homes, and 9% rented housing. Median income of mothers who reported employment was $10 000 to $15 000, whereas the median income for fathers was more than $30 000. Combined family median income was in excess of $30 000.
Age and Growth
Cohort age at evaluation was 77 months (range: 61-97 months). For the HFOV and CV groups, age (months), stature (cm), and weight (kg) at follow-up were 77.0 ± 10.0 versus 77.1 ± 10.8, 117.5 ± 7.3 versus 117.7 ± 6.0, and 21.0 ± 3.8 versus 21.4 ± 3.5, respectively. Both study groups had stature and weight within normal limits, and no differences were noted between study group survivors (Fig 1).
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Mental and Motor Proficiency Testing
Verbal IQ scores were 101 ± 18 for HFOV-treated patients and 93 ± 23 for CV-treated patients (50th percentile score = 100). Gross, fine, and combined motor scores were 47 ± 15 versus 43 ± 22, 48 ± 13 versus 46 ± 15, and 47 ± 15 versus 43 ± 20 for HFOV versus CV groups, respectively (50th percentile score = 50). There were no differences between groups at follow-up in verbal IQ (Fig 1) or in any of the subtests for the Wechsler scales (data not shown). Average verbal IQ was within normal range for both study groups (Fig 1). Similarly, gross motor, fine motor, and combined motor performance were near the 50th percentile for both groups and were not different (Fig 1).
Pulmonary Function Testing
As a check on intrapatient consistency, the mean percentage difference between forced vital capacity (FVC; spirometry) and VC (plethysmography) was calculated as 4%, suggesting equivalency between methods. Forced expiratory volume in 1 second (FEV1)/FVC was lower than expected for the HFOV group, but there was no intergroup difference between CV and HFOV patients (Fig 2). Values for forced expiratory flow at 50% vital capacity (FEF50%)/TLC were normal and similar between groups, but peak expiratory flow (PEF)/TLC was lower than predicted in the CV group and CV group values were lower than those in the HFOV group. Also, VC/TLC was decreased in the CV group and lower than the normal values found in HFOV patients, whereas residual volume (RV)/TLC was increased in the CV group but not in the HFOV group (Fig 2). Although DLCO was slightly higher than normal in the HFOV group, there was no between-group difference in this measure. The index of inspired gas maldistribution, alveolar volume (VA)/TLC, was decreased in the CV group compared with the HFOV group (Fig 2). The intergroup difference suggested that approximately 20% of inspired gas during a single breath failed to equilibrate throughout the lung for patients in the CV group. Finally, the volume ratio relationships between TLC, VC, and RV indicated that TLC for the CV group was higher than normal and greater than values for the HFOV-treated patients (Fig 3). The TLC change in the CV group seemed to be due to an increase in RV that was not seen in the HFOV-treated patients (Fig 3).
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Neonatal Predictors of Childhood Outcome
To evaluate predictors of outcome, we built a multivariate logistic regression model using 1) neonatal factors listed in Table 1, 2) sociodemographic factors of combined parental education and combined parental income, and 3) study group assignment. The model was applied to evaluate whether any of these factors contributed in predicting an abnormal outcome for parameters for which between-group differences were noted, namely, the pulmonary function measures of RV/TLC, PEF/TLC, VC/TLC, and VA/TLC. Our estimate of abnormality was whether the outcome measure was contained within the worst 16% of SDS values. Of the 20 factors included in the model, only study group assignment to CV contributed in predicting abnormal values for RV/TLC (P = .004) and PEF/TLC (P = .001). Likewise for VA/TLC, there also was only a single significant prediction factor, which was the number of combined hours of catecholamine use (P = .028). No factors were significant at the P = .05 level in contributing to the prediction of abnormal VC/TLC.
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DISCUSSION |
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Abstract
Methods
Results
Discussion
Conclusion
References
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We report the first childhood follow-up evaluation for premature infants who were enrolled in a randomized controlled trial for the treatment of RDS and were given surfactant replacement and then treated with a lung recruitment strategy using HFOV. Although neonatal outcomes indicated that this treatment strategy provided pulmonary benefit with the initial nursery hospitalization,1 it was uncertain whether these clinical differences might persist after infant lung growth and maturation. The results presented here suggest long-term pulmonary benefit for the neonatal early HFOV treatment strategy as evidenced by the finding of pulmonary changes in the CV randomized patients that were not present or diminished at follow-up in the HFOV randomized patients.
Obstructive-type pulmonary disease is a known complication of neonatal pulmonary injury after CV treatment for RDS with or without surfactant replacement. Depending on the severity of bronchopulmonary dysplasia (BPD) and the degree of prematurity at birth, long-term pulmonary deficits can include increased RV, decreased expiratory flow, increased airway resistance, and, in severe cases, decreased vital capacity.14-16 Similar changes, including impairment in DLCO, have been noted in non-surfactant-treated conventionally ventilated neonates at 9 years of age who were not identified as having BPD during their neonatal course.17 Mansell et al18 found changes at 6 years of age in the lung function of nonventilated "healthy" preterm infants who did not receive mechanical ventilation. These authors speculated that factors associated with prematurity and not RDS respiratory treatment may determine long-term changes in pulmonary function. Gappa et al2 demonstrated pulmonary function changes, including decreased maximum expiratory flows at 25% and 50% of vital capacity and increased airway resistance, in a group of infants who were tested at 7 years of age and had been treated with surfactant and CV during a controlled surfactant trial. Conversely, Pelkonen et al3 identified normal FVC in prophylactic surfactant-treated preterm infants at 7 to 12 years of age who had been treated with CV, but FVC was reduced in rescue-treated or in placebo-treated groups. One third to two thirds of all preterm infants had findings of bronchial obstruction. In general, infants who were treated with surfactant had higher PEF and FVC than those who were not, suggesting long-term pulmonary benefit from surfactant treatment in these children. Recently, Pianosi and Fisk4 reported pulmonary function at 8 to 9 years of age on a subset of presurfactant era HFOV-ventilated infants who were enrolled in the HIFI trial.19 These authors found mild obstructive changes in preterm infants who were ventilated with either HFOV or CV. Like Mansell et al, they suggest that factors other than the mode of ventilation may have a stronger influence on pulmonary outcome.
In the current study, we noted that, compared with predicted, the HFOV group had decreased FEV1/FVC. These values, however, were not different from those of the CV-treated children. It is unclear whether these decreased values were due to treatment with HFOV or represent changes that may be related to preterm delivery4,18 or to other factors, such as poor effort or pulmonary testing inexperience. Differences between group values for RV/TLC, PEF/TLC, VC/TLC, and VA/TLC, however, are consistent with findings of significant pulmonary performance decrements in the CV group, including inspiratory gas maldistribution.
One explanation for the increased lung volumes in the CV group may be small airways disease as has been reported in neonatal survivors with BPD.14-17 Mansell et al18, however, suggested that prematurity may be associated with a reduction in diameter of major airways. Airway flow limitation as a result of smaller-than-expected airway diameter may be unavoidable and obligatory residua in surviving premature infants. Additional research into the cause of these changes may help determine whether pulmonary developmental abnormalities play a central role or other factors related to neonatal respiratory treatment are at issue.
The abnormalities in pulmonary function that were identified in the seemingly healthy children of the CV-treated group suggest a diagnosis of persistent lung disease. Similar pulmonary function changes are evident in pediatric patients with obstructive lung disease18 and in known BPD patients in whom the airway changes are a consequence of treatment for RDS.12-15 Identification of abnormal pulmonary function consistent with obstructive lung disease in this group of premature infants who could be classified as having uncomplicated RDS supports the findings of ongoing silent pulmonary disease reported by Coalson et al20 in long-term primate survivors of an experimental model of BPD. The significant decrease in alveolar number seen in this animal model and in postmortem examination of lungs from human infants who were treated with CV for RDS21 or who developed BPD21,22 suggests that arrest of alveolarization is an important component of this disease. Although DLCO values might be expected to decline with a decrease in lung surface area such as would occur with alveolar loss, we did not find impairment in diffusion capacity in either group in the present study. Low DLCO values, however, have been reported in children who were ventilated with CV for RDS and did or did not develop BPD.17 It is unclear how sensitive the DLCO measurement may be to changes in alveolar number and to what degree DLCO measurements can reflect reduced alveolarization. Such clinical correlation studies are not available. The ability of the HFOV-treated infants in this study to tolerate sub-sea-level ambient oxygen levels at hospital discharge1 suggests maintenance of alveolar surface area and thus alveolar number compared with infants who were treated with CV. Increased DLCO values as seen at childhood follow-up in the HFOV-treated patients could reflect an improvement in alveolar and pulmonary capillary development.
On the basis of the possibility of developmentally reduced airway diameters and a simplified alveolar structure, other explanations for the increase in RV/TLC seen in the CV-treated group can be postulated. Functional airflow impairment might occur as a result of a mismatch between airway diameter and an increase in gas volume within the simplified alveolar structures, not, therefore, as a result of airways disease but as a result of a disturbance in lung geometry. Another possible contributing factor to increased RV/TLC is an increase in end-expiratory resting volume necessitated by the structure of the simplified alveoli. Pulmonary studies more complex than those used in this analysis will be required to elucidate further these questions about alveolar structural changes in response to RDS respiratory treatment strategies.
That the early HFOV treatment strategy after surfactant seemed to ameliorate pulmonary changes found in childhood suggests that long-term outcome may be modifiable by the choice of RDS treatment strategy. There has been little human clinical experience that correlates to the prevention/reduction in lung injury afforded by HFOV over CV that has been shown in primate models of RDS.23,24 Our current findings along with the lack of differences between HFOV and CV groups in the 9-month pulmonary follow-up of the HIFI trial infants25 and the follow-on findings at 9 years by Pianosi and Fisk4 support the opinion of Bryan and Froese26 that unless high-frequency ventilation is used with a lung recruitment strategy, outcomes may be no different from with CV. Pianosi and Fisk4 offer the HIFI trial and the recent high-frequency jet ventilation trial of Keszler et al27 as such examples. In the current study, the combination of early HFOV using a lung recruitment strategy after surfactant replacement therapy seemed to prevent or reduce the development of chronic pulmonary changes noted in other studies in which infants were treated with CV alone,12-15 CV with surfactant,17 or low-lung-volume high-frequency ventilation.19,27 Childhood pulmonary function data that address the efficacy of newer patient-triggered modes of CV in their possible role as preventive injury treatments for RDS are not available.
In terms of the childhood growth and development of these HFOV and CV study patients, stature, weight, and mental skills essentially were normal at follow-up at 77 months of age. Motor proficiency and the frequency of severe disabilities were not different between the 2 groups. In a previous randomized controlled trial of early HFOV in Japan, there was no difference in the number of patients with developmental delays between HFOV- and CV-treated infants at 12 months of age.28 In another HFOV follow-up study in which neurodevelopment was assessed, the HIFI trial reported status at 16 to 24 months postterm age.29 The HIFI report noted fewer infants with Bayley index scores of >83 (84 is 1 SD below the mean) in the HFOV-treated infants (57% HFOV vs 66% CV; P = .06). The difference became significant (P = .0497) when the data were analyzed for Bayley score of >83 in patients who had no central nervous system injury. In the present study, a similar cutoff using infants who scored at or above 1 SD below the mean for the Wechsler scales yielded 80% HFOV versus 70% CV, which was not a statistically significant difference. The finding of normal childhood neurodevelopment in the present HFOV study group is reassuring in view of concerns over possible increased intracranial morbidity in preterm infants who are treated with high-frequency ventilation.26,28 There was no evidence in our initial trial or in the present study to suggest any adverse effect on central nervous system outcome with the use of early intervention HFOV.
Although the health histories were similar for the 2 groups, they
illustrate the higher health care and educational investment often
required for preterm infants. Of note was the 34% rehospitalization rate and the frequent use of developmental and educational special programs
55% and 23%, respectively. We did not identify significant associations between history of asthma, smoke exposure, or respiratory syncytial virus hospitalization with pulmonary outcome in this cohort
of children. With regard to neonatal and sociodemographic factors, only
study group assignment to neonatal treatment with CV predicted the
pulmonary function changes seen in childhood follow-up, except that
duration of catecholamine use in the neonatal intensive care unit
seemed to have a negative influence on the index of inspired
gas maldistribution. It is not known whether the latter is a direct
catecholamine effect or catecholamine use serves as a marker for other
factors, such as systemic inflammatory response that secondarily may
contribute to lung injury through mediator effects or acute lung injury
mediators that produce systemic effects, including cardiovascular
instability. These types of interactions are thought to occur in acute
RDS30 and probably play a role in neonatal lung injury.
Unquestionably, multiple factors are involved in the lung injury
process during the neonatal period, and choices of ventilatory strategy
and management may shift the contribution or importance of these
factors in determining outcome. Further long-term research in
controlled neonatal patient populations is indicated for understanding
the influence of disturbed postnatal development overlaid by neonatal
pulmonary treatment strategies that seek to minimize acute and chronic
lung injury processes.
The data presented here may be biased by several factors that should be taken into account in interpreting and applying the results of this follow-up study. Because all patients in the original study could not be seen in follow-up and not all follow-up patients could be tested in all evaluation areas because of their young age, various nonsystematic selection biases could influence the differences in outcome that were identified. Although the results could be biased by having a greater number of higher risk infants seen in the CV group than in the HFOV group, this did not seem to be the case. Using either the chronic lung disease score at 30 days or continuous oxygen use at discharge as neonatal risk indicators, 33% and 21%, respectively, of such patients were not seen in follow-up from the CV group, whereas all of these high-risk patients were seen from the HFOV group. This suggests a bias against the HFOV- and not the CV-treated patients at follow-up. Similarly, a bias also may be suggested by the larger percentage of infants in the HFOV group who were exposed to household smoking. Secondary exposure to cigarette smoke is known to exacerbate childhood pulmonary problems and could have contributed to poorer pulmonary function performance. The current results, however, do not suggest such an influence. Although having a larger number of follow-up study infants obviously is desirable, limitations in access, scheduling, and funding often define practical boundaries. The 100% contact rate and the 87% evaluation rate for the Provo cohort represent a reasonable effort and sample size for this follow-up study. Childhood and longer term follow-up of both high- and low-risk premature infants who have been constituents of controlled treatment trials should be a defined priority so that both the subtle and the obvious treatment effects can be evaluated in the context of postnatal development and maturation.
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CONCLUSION |
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Abstract
Methods
Results
Discussion
Conclusion
References
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We report 77-month (6.4-year) postdelivery neurodevelopmental and pulmonary function evaluations on 87% of the Provo cohort of patients from the Provo multicenter early HFOV treatment trial. At follow-up, the children exhibited equivalent growth, verbal IQ, and motor proficiency skills that were not different between the study groups. Preterm infants who originally were randomized to CV after surfactant treatment were found to have evidence of chronic lung disease manifesting as changes in residual lung volume, vital capacity, PEF, and maldistribution of ventilation. These findings were not noted in the children who were randomized to HFOV. We speculate that early HFOV when used with a lung recruitment strategy in combination with surfactant replacement may ameliorate acute neonatal lung injury that predisposes some preterm infants to develop chronic lung disease.
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FOOTNOTES |
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Received for publication Sep 18, 2000; accepted Jan 15, 2001.
Reprint requests to (D.R.G.) Department of Neonatology, 1034 North 500 West, Provo, UT 84604. E-mail: uvdgerst{at}ihc.com
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ABBREVIATIONS |
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HFOV, high-frequency oscillatory ventilation; RDS, respiratory distress syndrome; CV, time-cycled pressure-limited conventional ventilation; VA, alveolar volume; TLC, total lung capacity; DLCO, lung diffusing capacity for carbon monoxide; SD, standard deviation; SDS, standard deviation score; FVC, forced vital capacity; FEV1, forced expiratory volume in 1 second; FEF50%, forced expiratory flow at 50% vital capacity; PEF, peak expiratory flow; RV, residual volume; BPD, bronchopulmonary dysplasia.
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REFERENCES |
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This article has been cited by other articles:
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  P. Truffert, J. Paris-Llado, B. Escande, J.-F. Magny, G. Cambonie, E. Saliba, G. Thiriez, V. Zupan-Simunek, T. Blanc, J.-C. Roze, et al. Neuromotor Outcome at 2 Years of Very Preterm Infants Who Were Treated With High-Frequency Oscillatory Ventilation or Conventional Ventilation for Neonatal Respiratory Distress Syndrome Pediatrics, April 1, 2007; 119(4): e860 - e865. [Abstract] [Full Text] [PDF]
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 E C Eichenwald High frequency oscillatory ventilation: is equivalence with conventional mechanical ventilation enough? Arch. Dis. Child. Fetal Neonatal Ed., September 1, 2006; 91(5): F315 - F317. [Full Text] [PDF]
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N Marlow, A Greenough, J L Peacock, L Marston, E S Limb, A H Johnson, S A Calvert, and for the United Kingdom Oscillation Study Group Randomised trial of high frequency oscillatory ventilation or conventional ventilation in babies of gestational age 28 weeks or less: respiratory and neurological outcomes at 2 years Arch. Dis. Child. Fetal Neonatal Ed., September 1, 2006; 91(5): F320 - F326. [Abstract] [Full Text] [PDF]
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U H Thome, W A Carlo, and F Pohlandt Ventilation strategies and outcome in randomised trials of high frequency ventilation Arch. Dis. Child. Fetal Neonatal Ed., November 1, 2005; 90(6): F466 - F473. [Abstract] [Full Text] [PDF]
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M. R. Thomas, G. F. Rafferty, E. S. Limb, J. L. Peacock, S. A. Calvert, N. Marlow, A. D. Milner, and A. Greenough Pulmonary Function at Follow-up of Very Preterm Infants from the United Kingdom Oscillation Study Am. J. Respir. Crit. Care Med., April 1, 2004; 169(7): 868 - 872. [Abstract] [Full Text] [PDF]
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W. Hofhuis, M. W. A. Huysman, E. C. van der Wiel, W. P. J. Holland, W. C. J. Hop, G. Brinkhorst, J. C. de Jongste, and P. J. F. M. Merkus Worsening of V'maxFRC in Infants with Chronic Lung Disease in the First Year of Life: A More Favorable Outcome after High-Frequency Oscillation Ventilation Am. J. Respir. Crit. Care Med., December 15, 2002; 166(12): 1539 - 1543. [Abstract] [Full Text] [PDF]
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