Surfactant therapy is a fundamental component of treating preterm infants, and it
has proven to be effective when administered as a preventative therapy in the delivery
room or as a rescue therapy for infants already suffering from respiratory distress
syndrome (RDS).[1] Implementing exogenous surfactant therapy in newborn medicine throughout the early
1990s led to a substantial decrease in infant mortality rates.[2] The role of exogenous surfactant therapy has recently been altered while critical
care for preterm newborns continues to advance and improve. Nasal continuous positive
airway pressure (nCPAP) is becoming more widely used as the main method of respiratory
support. Consequently, a significant number of premature infants experiencing respiratory
distress no longer necessitate intubation either immediately after birth or during
the early postnatal period.[3] This additionally entails the postponement or avoidance of surfactant usage. Nevertheless,
a significant proportion of newborns who initially received CPAP subsequently needed
intubation due to escalating oxygen needs and/or respiratory acidosis, which were
the most prevalent factors. RDS caused by a lack of surfactant is the most common
reason for CPAP failure in premature newborns.[4] The study conducted by Dargaville et al,[5] utilizing CPAP shortly after birth followed by selective surfactant administration
is seen as an alternative approach to the standard practice of intubation with prophylactic
or early surfactant treatment in premature neonates.[6] The utilization of the intubation, surfactant, and extubation (INSURE) method has
demonstrated a decrease in the requirement for mechanical ventilation (MV).[7] However, positive pressure ventilation (PPV) and tracheal tube placement are necessary
actions in the INSURE technique. This will be linked to a range of acute and chronic
morbidities, including bronchopulmonary dysplasia (BPD).[2]
Consequently, throughout the past 30 years, significant efforts have been made to
develop less intrusive alternative techniques for delivering surfactants. The primary
objective is to provide a sufficient dose of surfactant without requiring PPV or intubation.
Currently, there are various techniques for delivering surfactants. They can be more
precisely classified into two main types based on the level of invasiveness. The techniques
that require direct laryngoscopy but substitute the endotracheal tube (ETT) with a
thin catheter, such as a flexible feeding tube or a semirigid angiocath, are collectively
known as “SURE.” This acronym encompasses LISA (less invasive surfactant administration),
MIST (minimally invasive surfactant therapy), and Take Care.[8] This not only avoids intubation but also enables uninterrupted use of CPAP, which
maintains a stable functional residual capacity (FRC) in the lungs of premature infants.
LISA is gaining popularity in neonatal intensive care units (NICUs) worldwide because
it reduces the need for MV. LISA differs from other methods of surfactant delivery
by allowing the newborn to continue spontaneous breathing and use the physiological
function of the larynx.[9] The outcomes obtained from studies conducted in advanced economies on the efficiency
of the least-invasive surfactant therapy technique cannot be generalized to countries
with middle and low incomes. Thus, we conducted this randomized trial aiming to evaluate
the efficacy of LISA/MIST by comparing the INSURE approach to a thin catheter approach
for surfactant treatment in spontaneously breathing premature neonates with RDS.
Patients and Methods
Methodology
We conducted a randomized clinical trial (RCT) on preterm infants with gestational
ages (GAs) between 28 and 36 weeks, spontaneous breathing infants, and respiratory
distress necessitating surfactant therapy. Infants who had major birth abnormalities,
abnormal heart structure, or required intubation at birth were not included. People
who needed more than 30% fraction of inspired oxygen (FiO2) on CPAP (7 cm H2O) to keep their oxygen saturation between 90 and 94% in 6 hours after birth were
randomly given either the MIST or INSURE techniques to apply surfactant. Every infant
was closely observed until they were discharged from the NICU or until they reached
36 weeks of postmenstrual age, whichever came later. A 16-gauge angiocath or a 6-French
feeding tube, depending on individual preference and accessibility, was prepared.
In the NICU, two competent specialists performed the procedure. Prior to the procedure,
no sedation was given. A direct laryngoscopy took place, and the catheter was inserted
below the vocal cords with the CPAP prongs in position. Once the catheter had been
inserted, the laryngoscope was withdrawn. Either the surfactant, beractant (Survanta),
was administered at a dose of 100 mg/kg, requiring a volume of 4 mL/kg or alternatively,
based on availability, bovactant (Alveofact) was given at a dose of 50 mg/kg with
a volume of 1.2 mL/kg. A 5- to 10-mL syringe containing the surfactant was filled
up with an extra 1 mL of air to compensate for the dead volume of the catheter. The
tracheal catheter was promptly removed after the surfactant was administered in a
single bolus over a 60- to 90-second period. Infants who had a heart rate of 100 beats
per minute or less, oxygen saturation of 80% or less, or apnea that lasts more than
20 seconds had PPV. If the patient's need for oxygen concentration (FiO2) remained above 30% 6 hours after surfactant delivery, a second dose of surfactant
was delivered in a similar way. Intubation was indicated if there was respiratory
acidosis with a pH below 7.2 and/or partial pressure of carbon dioxide (PCO2) levels over 60 mm Hg. Additionally, recurrent apnea requires PPV despite the patient
receiving caffeine. The use of CPAP was discontinued if the infant did not exhibit
any signs of difficulty breathing and remained free from apnea for a minimum of 24 hours
while being treated with CPAP settings of 5 or less and FiO2 levels of 25% or below. During INSURE technique, sedation was optional; however,
analgesia and nonpharmacological pain management had been used, infants underwent
intubation using an ETT of suitable size and were administered a dosage of 100 mg/kg
of surfactant. After the delivery of surfactant, neonates are either ventilated using
bag valve masks or connected to a mechanical ventilator that provides gas volumes
with positive pressure for a short duration. The patient received nCPAP treatment
following extubation. If a FiO2 level more than 30% was necessary to maintain arterial oxygen saturation between
90 and 94% after 6 to 12 hours, they administered a second dosage of surfactant ([Fig. 1]).
Fig. 1 Flowchart of the administration of surfactant. CPAP, continuous positive airway pressure;
NICU, neonatal intensive care unit.
Randomization
Randomization is generated by a computer, which produces random and distinct sequences
of consecutive numbers. During the whole trial, from the intervention phase to the
evaluation of outcomes and analysis of collected data, there was no intervention with
the aim of ascertaining the undisclosed fundamental principle of the treatment being
administered.
Ethical Approval
The ethical committee of the Faculty of Medicine, Assiut University approved the study
(IRB: 04-2024-100255). Informed written consent was obtained from the parents of all
participant newborns before recruitment in the study after explaining the objectives
of the work.
Outcomes
The key finding was to detect the effect of MIST approach on the requirement for MV
within the first 72 hours of life. The secondary outcomes were repeat doses of surfactant
therapy, rates of hemodynamically significant patent ductus arteriosus (PDA), pneumothorax,
intraventricular hemorrhage (IVH; ≥grade 2; Papile classification), necrotizing enterocolitis
(NEC; modified Bell's stage ≥2),[10] BPD according to the 2018 National Institute of Child Health and Human Development's
definition,[11] early-onset sepsis (EOS), oxygen duration, hospital stay, apnea, bradycardia, or
desaturation during surfactant administration, and death.
Statistical Analysis
All statistical calculations were done using SPSS (statistical Package for the Social
Science; SPSS Inc., Chicago, Illinois, United States) version 22. Data were statistically
described in terms of mean ± standard deviation, or median and range when not normally
distributed, frequencies (number of cases), and relative frequencies (percentages)
when appropriate. Comparison of quantitative variables was done using Student's t-test for normally distributed data and Mann–Whitney's U test for nonnormally distributed data. For comparing categorical data, chi-square
(χ2) test was performed. Exact test was used instead when the expected frequency is less
than 5. A p-value is always two-tailed set significant at 0.05 level.
Results
Every baseline variable was comparable between the two groups, as shown in [Table 1]. There was no difference in both maternal and neonatal clinical characteristics.
There was a significant reduction in the need for MV in the MIST group (p < 0.001). Furthermore, the duration of MV and the duration of nCPAP, periventricular–intraventricular
hemorrhage (PIVH), and death were significantly less in the MIST group ([Table 2]). No difference was observed between the two groups in pneumothorax, EOS, PDA, NEC,
or the duration of supplemental oxygen ([Table 2]).
Table 1
Baseline characteristics of the studied patients
Variable name
|
MIST group (n = 45)
|
INSURE group (n = 45)
|
p-Value
|
Gestational age (wk)
|
Mean ± SD
|
30.27 ± 2.14
|
30.44 ± 1.93
|
0.679
|
Range
|
28–34
|
28–34
|
Birth weight (g)
|
Mean ± SD
|
1,144.80 ± 225.15
|
1,149.11 ± 192.59
|
0.922
|
Range
|
830–1,700
|
850–1,600
|
Gender, n (%)
|
Male
|
22 (48.9%)
|
16 (35.6%)
|
0.200
|
Female
|
23 (51.1%)
|
29 (64.4%)
|
Apgar score (first min)
|
4 (2–6)
|
4 (2–6)
|
0.630
|
Apgar score (fifth min)
|
7 (5–9)
|
8 (4–9)
|
0.379
|
IUGR, n (%)
|
AGA
|
27 (60.0%)
|
34 (75.6%)
|
0.175
|
SGA
|
17 (37.8%)
|
11 (24.4%)
|
LGA
|
1 (2.2%)
|
0 (0.0%)
|
Mode of delivery, n (%)
|
NVD
|
9 (20.0%)
|
9 (20.0%)
|
1
|
CS
|
36 (80.0%)
|
36 (80.0%)
|
Multiple births, n (%)
|
Single
|
37 (82.2%)
|
37 (82.2%)
|
1
|
Twin
|
8 (17.8%)
|
8 (17.8%)
|
PROM, n (%)
|
13 (28.9%)
|
14 (31.1%)
|
0.818
|
Antenatal steroid, n (%)
|
19 (42.2%)
|
17 (37.8%)
|
0.667
|
Duration of steroid, n (%)3
|
Full dose
|
13 (68.4%)
|
13 (76.5%)
|
0.717
|
Any doses
|
6 (31.6%)
|
4 (23.5%)
|
Maternal illness, n (%)
|
None
|
34 (75.6%)
|
37 (82.2%)
|
0.887
|
Diabetes
|
4 (8.9%)
|
2 (4.4%)
|
Hypertension
|
5 (11.1%)
|
4 (8.9%)
|
Chorioamnionitis
|
2 (4.4%)
|
2 (4.4%)
|
Downes score before surfactant
|
Median (range)
|
7 (5–8)
|
6 (5–8)
|
0.327
|
Serum glucose (mg/dL)
|
Mean ± SD
|
69.04 ± 13.28
|
71.87 ± 10.89
|
0.273
|
Range
|
40–90
|
49–89
|
Age at first-dose surfactant therapy (h)
|
Mean ± SD
|
2.42 ± 1.07
|
2.10 ± 1.03
|
0.156
|
Range
|
1–4.5
|
1–4
|
Number of surfactant doses, n (%)
|
One dose (100 mg/kg)
|
30 (66.7%)
|
31 (68.9%)
|
0.200
|
Two doses (200 mg/kg)
|
15 (33.3%)
|
14 (31.1%)
|
FiO2 before PS administration
|
Median (range)
|
0.5 (0.4–0.6)
|
0.5 (0.4–0.6)
|
0.696
|
Abbreviations: AGA, appropriate for gestational age; CS, cesarean section; FiO2, fraction of inspired oxygen; INSURE, intubation surfactant, and extubation; IUGR,
intrauterine growth retardation; LGA, large for gestational age; MIST, minimally invasive
surfactant therapy; NVD, normal vaginal delivery; PROM, premature rupture of membrane;
PS, pulmonary surfactant; SD, standard deviation; SGA, small for gestational age.
Note: Quantitative data are presented as mean ± SD and median (range), qualitative
data are presented as number (percentage), and significance is defined by p < 0.05.
Table 2
Outcome variables of the study group
Variable name
|
MIST group (n = 45)
|
INSURE group (n = 45)
|
p-Value
|
Duration of O2 therapy (d)
|
Mean ± SD
|
16.20 ± 6.45
|
16.71 ± 6.95
|
0.719
|
Range
|
6–30
|
6–32
|
Need for MV <72 h
|
11 (24.4%)
|
30 (66.7%)
|
< 0.001*
|
Duration of MV (d)
|
Mean ± SD
|
4.91 ± 1.30
|
7.13 ± 2.97
|
0.022*
|
Range
|
3–7
|
3–13
|
Duration of CPAP (d)
|
Mean ± SD
|
6.67 ± 3.55
|
8.36 ± 2.96
|
0.016*
|
Range
|
1–14
|
1–14
|
Death, n (%)
|
3 (6.7%)
|
11 (24.4%)
|
0.020*
|
BPD at 36 wk PMA, n (%)
|
6 (13.3%)
|
7 (15.6%)
|
0.764
|
IVH > grade II, n (%)
|
4 (8.9%)
|
11 (24.4%)
|
0.048*
|
Pneumothorax, n (%)
|
3 (6.7%)
|
6 (13.3%)
|
0.485
|
NEC > stage II, n (%)
|
3 (6.7%)
|
2 (4.4%)
|
1
|
Early-onset sepsis, n (%)
|
9 (20.0%)
|
17 (37.8)
|
0.063
|
PDA, n (%)
|
3 (6.7%)
|
7 (15.6%)
|
0.180
|
Pulmonary hemorrhage, n (%)
|
2 (4.4%)
|
4 (8.9%)
|
0.677
|
Duration of NICU stay, (d)
|
20 (7–36)
|
22 (7–38)
|
0.285
|
Abbreviations: BPD, bronchopulmonary dysplasia; CPAP, continuous positive airway pressure;
FiO2, fraction of inspired oxygen; INSURE, intubation surfactant, and extubation; IVH,
intraventricular hemorrhage; MIST, minimally invasive surfactant therapy; MV, mechanical
ventilation; NICU, neonatal intensive care unit; PDA, patent ductus arteriosus; PMA,
postmenstrual age; SD, standard deviation.
Note: Qualitative data are presented as numbers (percentage), and *significance is defined by p < 0.05.
Discussion
In attempts to determine the necessity of MV during the first 72 hours of life as
the primary outcome between both groups, the study found a statistically significant
difference. The LISA group also had much shorter MV and CPAP durations compared with
the INSURE group.
A new systematic review and meta-analysis of 16 RCTs that were released from 2012
to 2020 found that giving surfactant through the LISA technique cut down on the need
for MV in the first 72 hours of life, as well as BPD, PIVH, pneumothorax, and death
rates in infants born before 36 weeks of gestation compared with INSURE.[12] Meta-analysis of Bellos et al concluded that compared with INSURE, surfactant administration
via a thin catheter was associated with significantly lower rates of mortality, MV,
BPD, and periventricular leukomalacia.[2] In the first 72 hours, the MIST group required much less intubation, according to
the recently released OPTIMIST-A study by Dargaville et al.[13] A total of 350 infants with GA ≤ 34 weeks with RDS were studied by Jena et al, who
randomized the patients between LISA and INSURE. According to their research, the
LISA group required significantly less MV within the first 72 hours (p < 0.01).[14] Using the LISA significantly lowered the demand for MV in newborns in the Boskabadi
et al[15] trial (p = 0.02). Similar findings were noted in Kribs et al,[16] with the LISA group invasively ventilated for a shorter period (p = 0.001).
The difference between the two groups regarding MV is 75% in INSURE versus 33.3% in
MIST. Such a relatively big difference between the two groups could be due to the
optional use of sedatives with INSURE technique which could increase the incidence
and duration of MV. Anand et al,[17] the largest study reporting on this outcome, the duration of MV (respiratory support
with an ETT) in case of use of sedation versus placebo, found a significant difference
in time spent on the ventilator between opioid and control groups (p = 0.0338). In the case of elective intubations in the NICU, sedation with an opioid
and muscle relaxant results in greater intubation success on the first attempt.[18] However, the use of some analgesic premedications is associated with respiratory
depression that can delay extubation and lead to prolongation of the period of MV.[19] Therefore, some clinicians prefer to avoid the use of analgesic premedication during
the INSURE procedure to facilitate immediate extubation.[20]
[21] Further clinical trials are underway to assess the benefits and risks of sedation
for LISA.
Animal studies have shown that a few mechanical breaths are enough to cause lung harm
in the newborn period, which explains the pulmonary benefits of the MIST approach
in lowering the need for MV and the duration of CPAP.[7] Moreover, it permits the maintenance of CPAP, preserving FRC and reducing atelectotrauma
in the premature lung.[22] Furthermore, by allowing the infant to breathe on its own, the MIST technique distributes
surfactant throughout the premature lung quickly and completely. Moreover, it is expected
that PPV administered to a lung with nonhomogeneous time constants will cause nonuniform
distension, raising the possibility of lung injury.[23] Thin catheter approach produced more consistent lung aeration than intubation in
a small-scale study using electrical impedance tomography on preterm neonates delivered
at a mean GA of 29 weeks.[24]
Yet there was no statistically significant difference between the LISA and INSURE
groups in terms of needing MV during the first 72 hours of life, according to Gupta
et al.[23] Nonetheless, the primary respiratory support in this trial was nasal intermittent
positive pressure ventilation (NIPPV), which may have decreased the need for IMV in
both research groups because there is evidence in the literature that using NIPPV
as the primary respiratory support reduces the need for IMV.
Comparable rates of BPD were observed in both groups in this trial: 15.6% in the INSURE
group and 13.3% in the LISA group. The difference was insignificant. Lau et al[25] conducted a meta-analysis comparing individuals in the thin catheter group and the
INSURE group. They found that fewer infants developed BPD without statistical significance.[25] Kribs et al[16] and Han et al[26] conducted RCTs with BPD analysis as their primary objective. Han et al's[26] study showed a tendency toward a decline in the incidence of BPD, 19.2 versus 25.9%
(p = 0.17), despite the lack of evidence of an apparent benefit with LISA on the incidence
of BPD.
Kribs et al[16] randomized 211 newborns less than 27 weeks of gestation to the INSURE and LISA groups.
The 36-week survival without BPD was the principal objective, and no statistically
significant difference was observed. Isayama et al[27] randomized 298 neonates with RDS to the INSURE and LISA groups, and there was a
trend toward a reduction in the incidence of BPD.
On the other hand, both Kanmaz et al[28] and Bao et al[29] demonstrated that the BPD rate was significantly reduced in the thin catheter group
compared with INSURE group. The reason was that our study population had higher GA
and birth weight, which resulted in a lower incidence of BPD compared with extremely
preterm infants.
The current investigation demonstrated a statistically significant disparity in the
occurrence of IVH between the two groups. Consistent with our result, Kribs et al's
evaluation of PIVH grade 3 or 4, the LISA group also had noticeably less severe PIVH.
It has been observed that LISA contributes to favorable secondary outcomes related
to lifelong disabilities.[16]
Surfactant administration via a thin catheter was associated with a reduction in the
risk of severe PIVH and mortality among survivors during their initial hospitalization,
based on a Cochrane review of 10 RCTs comparing various methods of surfactant administration.[22]
A prospective cohort study was conducted to assess the occurrence of IVH in preterm
children with a GA less than 34 weeks who had LISA versus a historical cohort who
received surfactant via INSURE. The LISA group had a significant reduction in the
incidence of severe IVH as compared with the historical group.[30]
Previous research by multiple authors, including Klebermass-Schrehof et al[31] and Härtel et al,[32] as well as multicentric clinical trials conducted by Kribs et al[16] and systematic reviews by Isayama et al[27] have demonstrated the favorable outcome of the LISA technique on severe IVH.
Nevertheless, many systematic reviews still exhibit inconsistency; Aldana-Aguirre
et al[7] found no significant effect on severe IVH.
This effect could be attributed to a variety of factors; it is known that in small
preterm infants, particularly in the first day of life, arterioles' autoregulatory
response to the fluctuations in mean arterial blood pressure (MABP) and partial pressure
of blood gases is weak.[28]
[33] Cerebral blood flow (CBF) is highly reliant on MABP due to impaired autoregulation.[33] Furthermore, the immature blood vessels in the germinal matrix are very fragile,
combined with a deficiency in cerebral autoregulation, which renders it more susceptible
to changes in PCO2 and CBF than the fully developed brain of a full-term infant.
The fluctuations in blood pressure observed in the INSURE group during the procedure
have an impact on cerebral perfusion, ultimately leading to an increased risk of intracranial
hemorrhage. Throughout the administration process, the INSURE group consistently maintained
elevated levels of SpO2, which were directly correlated with the pressure of the operator's resuscitating
airbag. The LISA approach effectively sustains nCPAP while administering surfactant,
resulting in stabilized SpO2 levels and eliminating the operator's need for manual pressure on the lungs. This
led to a notable decrease in pulmonary barotrauma and severe IVH, improving treatment
outcomes.[34]
Thus, by maintaining a preterm newborn in spontaneous breathing with a recruited lung
by noninvasive ventilation, the cardiopulmonary interactions are reduced and a more
stable circulation is maintained. This helps minimize fluctuations in systemic blood
pressure and, consequently, CBF. This beneficial impact would also be amplified by
a more balanced and steadier CO2 level and by decreased use of atropine, sedatives, and inotropic medications, which
might contribute to keeping the CBF steadier.[35]
[36]
Within the scope of this study, there was a single occurrence of NEC stage 2 in the
MIST group, while the INSURE group had two instances. The prevalence of PDA was lower
in the MIST group, with an overall prevalence of 6.7%, compared with an overall prevalence
of 15.6% in the INSURE group. The disparity was negligible.
The duration of hospitalization was similarly reduced in the MIST group. Despite the
lack of statistical significance, the decrease in the duration of hospitalization
has had a considerable social and economic effect. Several variables influence early
discharge, including NICU-related challenges (sepsis and feeding issues), social elements,
and public health issues.[37]
Between the two groups, there was no statistically significant difference in the need
for a second dosage of surfactant. According to Aguar et al,[37] the MIST group required a significantly higher amount of surfactant for the second
treatment as compared with the INSURE group. The fact that the surfactant dose in
MIST was 100 mg/kg as opposed to 200 mg/kg in the INSURE group may have contributed
to this result. We used the same dose of surfactant in both groups in this trial,
and the results were consistent with previous studies showing that a dose of 100 mg/kg
produced satisfactory outcomes.[25]
[28]
Failure to require intubation and ventilation in preterm infants within 72 hours after
MIST is regarded as MIST success. The reported incidence of MIST failure, defined
as the necessity for intubation and mechanical breathing within 72 hours after the
procedure, is 24% in newborns. This rate is significantly lower compared with the
67% recorded with the INSURE approach.
Univariate logistic regression analysis for prediction of MIST failure among the studied
preterm neonates showed that lower GA, lower birth weight, history of PROM, not receiving
antenatal steroids, and IVH are significant predictors of MIST failure. The results
of the multivariate logistic regression analysis demonstrated that lower GA and a
lack of antenatal steroids remain important predictors of MIST failure. Thus, the
use of prenatal corticosteroids and postnatal surfactants in the prevention and treatment
of RDS has considerably improved neonatal outcomes by lowering respiratory morbidity
and mortality ([Table 3]).
Table 3
Univariate and multivariate logistic regression models of risk factors for MIST failure
(n = 45)
Variables
|
Univariate analysis
|
Multivariate analysis
|
OR
|
95% CI
|
p-Value
|
OR
|
95% CI
|
p-Value
|
Gestational age
|
0.213
|
0.068–0.672
|
0.008[a]
|
0.149
|
0.034–0.657
|
0.012[a]
|
Birth weight
|
0.986
|
0.977–0.996
|
0.007[a]
|
|
|
|
APGAR score at 1 min
|
0.431
|
0.200–0.929
|
0.032[a]
|
|
|
|
Multiple births
|
2.175
|
0.426–11.116
|
0.351
|
|
Cesarean section
|
0.302
|
0.064–1.425
|
0.130
|
|
|
|
PROM (yes vs. no)
|
8.167
|
1.800–37.048
|
0.006[a]
|
|
|
|
Antenatal steroid (yes vs. no)
|
11.250
|
1.293–97.856
|
0.028[a]
|
19.743
|
1.428–272.968
|
0.026[a]
|
Downes score before surfactant
|
1.538
|
0.733–3.231
|
0.255
|
|
|
|
Age of first-dose surfactant therapy
|
0.529
|
0.245–0.141
|
0.104
|
|
|
|
No. of surfactant (twice vs. once)
|
2.786
|
0.519–14.963
|
0.232
|
|
|
|
IVH > grade II (yes vs. no)
|
12.375
|
1.132–135.236
|
0.039[a]
|
|
|
|
Abbreviations: CI, confidence interval; IVH, intraventricular hemorrhage; MIST, minimally
invasive surfactant therapy; OR, odds ratio; PROM, premature rupture of membranes.
a
p-Value is significant.
The current study's key advantages are its acceptable sample size and resilient design.
However, our research had a significant constraint that should be noted in future
studies: it was a single-center study, and infants with gestations less than 28 weeks
were excluded. Furthermore, the types of surfactants used varied between the study
arms and were not standardized. Furthermore, we have no data on the research population's
long-term neurodevelopment outcomes.