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Indian Pediatr 2011;48: 467-470 |
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Rescue High Frequency Oscillation in Neonates
with Acute Respiratory Failure |
Preetham Kumar Poddutoor , Dinesh Kumar Chirla, Kapil Sachane, Farhan A R
Shaik and Alla Venkatlakshmi
From Rainbow Children’s Hospital and Perinatal Centre,
Banjara Hills, Hyderabad, India.
Correspondence to: Dr Preetham Kumar, Rainbow Children’s
Hospital, Hyderabad 500 034, India.
Email: [email protected]
Received: June 6, 2010;
Initial review: July 14, 2010;
Accepted: October 28, 2010.
Published online: 2011 February, 28.
PII: S09747559INPE1000019-2
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Abstract
The aim was to study the efficacy of rescue High
Frequency Oscillatory Ventilation (HFOV) in improving the oxygenation
and ventilation in neonates with acute respiratory failure after failing
Conventional Mechanical Ventilation (CMV). Primary outcome was short
term oxygenation, lung recruitment, and ventilation and secondary
outcome studied was survival. 675 babies were ventilated and 97 of them
received HFOV. HFOV significantly improved oxygenation index,
alveolar-arterial oxygen gradient, pH, PCO2, PO2 and caused better lung
recruitment within 2 hours. Fifty seven babies (58.77%) survived and the
mortality was more in <28 weeks, babies with pulmonary hemorrhage,
sepsis and CDH.
Key words: Failed CMV, High Frequency Oscillatory Ventilation,
Rescue ventilation.
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Pulmonary disease is a major cause of mortality and morbidity in term and
near term infants. Conventional mechanical ventilation (CMV) has been used
for many years but may lead to lung injury, require the subsequent use of
more invasive treatment such as extracorporeal membrane oxygenation (ECMO),
or result in death [1]. High frequency oscillatory ventilation (HFOV) is a
new mode of ventilation using lung protective strategy [2] and the safer
use of mean airway pressure that is higher than that generally used during
CMV [3]. Studies suggest that HFOV is a better rescue therapy and also
decreases the requirement of ECMO [4,5].
HFOV is being used in our unit for the past five years
for various neonates with respiratory failure. As there are very few
rescue studies reported, we intended to see the efficacy of HFOV in
improving oxygenation and ventilation in babies who failed CMV.
Methods
The study was a prospective observational study
conducted from January 2006 to June 2009 at Rainbow Children’s Hospital,
Hyderabad, a 40 bedded tertiary level NICU. During the study period, 675
babies were ventilated, out of which 97 babies who required oscillation as
per the unit protocol were included in the study.
Each baby with impending respiratory failure was
ventilated conventionally and if the baby did not improve or deteriorated
the following measures were done. Recruitment of the lung was prioritized
by increasing the PEEP to a higher level of 7, followed by arterial blood
gas (ABG) and a chest X-ray. If the X-ray showed
under-inflation, then PEEP was increased to higher levels. Surfactant was
given wherever necessary. On HFOV these babies were started on a MAP of 2
cm higher than the MAP on conventional ventilator and MAP was increased
until a saturation of >95% was achieved (after which priority was given to
wean off FiO2). The amplitude was
adjusted based on the chest wriggle; frequency was started at 12Hz for the
preterm babies and at 10 Hz for term babies and adjusted later based on
ABG analysis. Recruitment of the lung was emphasized upon and
reconfirmation of recruitment was done after 1-2 hours with chest
radiograph (by two independent physicians). The baby was kept on the
available oscillator Sensormedix 3100 A, SLE 5000 and Drager Babylog 8000
plus and rest of the treatment was given as per the standard unit
protocols.
Criteria for starting HFOV: The criteria for
starting HFOV were high pressures on CMV, inadequate oxygenation,
ventilation, inadequate recruitment inspite of high PEEP, deterioration on
CMV inspite of high pressures, and severe PPHN. Neonates who were referred
from other hospitals after failing CMV and/or were unstable on CMV were
directly put on HFOV.
Outcome measures: The ventilatory settings, ABG
analysis (done as soon as possible after HFOV but in few instances took
upto 2 hours), Oxygenation index (OI), Alveolar-arterial Oxygen Gradient
(AaDO2), duration of ventilation,
and complications of ventilation were recorded during CMV and subsequently
when shifted over to HFOV. Primary outcome was short term oxygenation,
lung recruitment, and ventilation, and secondary outcome studied was
survival.
Definitions: Adequate oxygenation PaO2
50-80 mmHg; Appropriate ventilation: PcO2 levels of 35-55 mmHg in preterm
babies <7 days, in term babies and, preterm babies >1 week 40-60 mmHg;
High pressures: PIP >25 mmHg in all babies or MAP >10 in preterm babies
with FiO2 requirement >0.5; Severe PPHN: OI >25 or Echocardiographic
evidence of Suprasystemic pulmonary pressures; Appropriate recruitment:
Lung volumes on X-rays >7 ribs; and, Over inflation: Flattened
diaphragms, >than 9 ribs on chest X ray.
Institutional ethics committee approved the study and
informed consent was taken before starting HFOV. Baseline characteristics
for survivors and non-survivors were compared using student’s ‘t’
test, and odds ratios were calculated using Chi square test. The
significance level for all tests is set at P<0.05.
Results
Ninety seven neonates were treated with HFOV after
failing CMV during the study period. Prematurity and HMD constituted the
majority of babies who received HFOV (Table I and II).
Median Age of presentation was 1 day (1-23 days). 73 babies were shifted
to HFO at a MAP of 12- 15mmHg, four were shifted at MAP 10 -12mmHg (airleaks)
and twenty at MAP of >16mmHg. The PIP values ranged from 22-36 (mean 28)
and low PIP levels were seen in ELBW babies. The mean PEEP was 6.1mmHg
(3-9), babies were shifted to HFO at lower PEEP in air-leaks, CDH and in
idiopathic PPHN. Mean age at initiation of rescue HFOV was 2.61 days
(range 1-29 days) and mean duration of ventilation was 62.02 hours (range
6-209 hours).
TABLE I
Baseline Variables of Oscillated Babies
Gestation |
Total |
Ventilated |
HFOV* |
Antenatal steroids† |
Survival in |
(weeks) |
Admitted |
|
|
|
|
|
oscillated |
|
Babies |
|
|
0 |
1 |
2 |
babies (%) |
Up to 26 |
46 |
41 |
11 |
1 |
2 |
8 |
4 (36.4) |
27 – 28 |
82 |
64 |
6 |
1 |
3 |
2 |
2 (33.3) |
29 – 30 |
256 |
90 |
8 |
0 |
3 |
5 |
4 (50) |
31 – 32 |
312 |
85 |
6 |
2 |
1 |
3 |
4 (66.7) |
33 – 34 |
388 |
113 |
10 |
6 |
2 |
2 |
6 (60) |
35 – 36 |
385 |
98 |
8 |
7 |
1 |
0 |
7 (87.5) |
37 and above |
767 |
184 |
48 |
0 |
0 |
0 |
30 (62.5) |
Total |
2236 |
675 (30.2%) |
97 |
17 |
12 |
20 |
57 (58.8) |
* High-frequency oscillatory ventilation; †No. of times antenatal
steroids used in babies on HFOV. |
TABLE II
Disease Specific Survival
Cause of respiratory |
Survival |
Odds Ratio |
distress in babies |
(%) |
for death |
who were oscillated (n) |
|
( C I) |
HMD (n=45) |
30 (66.66) |
0.54 (0.23-1.23) |
PPHN (n= 37) |
24 (64.86) |
0.66 (0.28-1.54) |
Pulmonary hemorrhage (n=15) |
8 (53.33) |
1.29 (0.42- 3.92) |
Sepsis (n=20)* |
9 (45) |
2.02 (0.74-5.46) |
MAS (n=22) |
17 (77.27) |
0.33 (0.11-1) |
NEC (n=2) |
0 |
– |
CDH (n=12) |
4 (33.33) |
3.31 (1.01-11.88) |
CHD (n=3) |
1 (33.33) |
2.94 (0.25-33.66) |
* 7/20 babies had fungal sepsis, 2 survived; HMD: Hyaline membrane disease,
PPHN: Persistant pulmonary hypertension of Newborn, MAS: Meconium
aspiration syndrome; NEC: Necrotizing enterocolitis;
CDHR: Congenital diaphragmatic hernia; CHD: Congenital heart disease.
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Of 97 neonates who were oscillated 57 (58.77%) improved
and survived with comparable survivals across each gestations. OI <15 was
seen in a total of 52 babies in the first two hours of oscillation, of
which 41 survived, and OI <10 was seen in 32 babies, of which 24 survived.
Decrease in OI, p/f ratio, AaDO2 and
improvement in pH, PCO2, PO2 with good lung recruitment was seen within 2
hours in all the babies (Table III).
TABLE III
Primary Outcome Measures Studied
Parameter |
CMV |
2 hrs after |
P value |
|
mean(SD) |
rescue HFOV |
|
|
|
mean (SD) |
|
AaDO2 |
518.42 (124.8) |
477.51 (144.3) |
0.048 |
FiO2 % |
0.905 (16) |
0.881 (17.6) |
0.348 |
pH |
7.23 (0.14) |
7.37 (0.14) |
<0.001 |
PaCO2 |
55.02 (17.7) |
35.60 (8.2) |
<0.0001 |
PaO2 |
58.28 (27.2) |
106.08 (72.5) |
<0.001 |
P/f ratio |
69.36 (44.2) |
121.9 (86.3) |
<0.001 |
Oxygen index |
27.41 (21.2) |
20.84 (17.2) |
0.028 |
Lung recruitment
(ribs) |
6.67(0.6) |
7.92 (0.87) |
0.001 |
AaDO2 : Arterial-alveolar oxygen difference; FiO2
; Fractional concentration of Oxygen in inspired air; P/f ratio. |
Discussion
HFOV is a safe and effective rescue technique in the
treatment of neonates with respiratory failure in whom CMV fails [6]. The
results of our study show that rescue HFOV improved oxygenation,
ventilation, lung recruitment and better oxygenation indices and there was
no increased incidence of IVH or airleaks. The HIFO trial [7] found that
in the first 24 hours after randomization, infants on HFOV required lower
FiO2 and had lower PaCO2 when
compared with infants on CMV. Provos study [8] found improved oxygenation
after the baby was oscillated and better p/f ratios with decrease in FiO2
requirement. Jaballah, et al. [6] in neonates treated for acute
respiratory failure found significant decrease in MAP, FiO2, OI, and AaDO2
after starting HFOV, PaCO2 decreased significantly after one hour of HFOV.
Similar results were reported by Sarnaik, et al. [9] in 31
children, 6 hours after institution of HFOV.
Survival rates in our study were 58.8% as compared to
75% reported previously but the population studied was much older and they
had excluded four patients who died few hours after shifting from HFOV
[10]. In our study, babies with CDH (OR of death 3.3), sepsis (OR 2) and
babies with pulmonary hemorrhage (OR 1.29) had high mortality and affected
the overall survival rates. The response to HFOV in babies who avoided
ECMO in a study by Carter, et al. [5]
was 46% and babies who failed HFOV were treated with ECMO. However, we had
to continue HFOV in the babies who failed because of absence of ECMO at
our center.
The absence of a control group in our study precludes
firm conclusions about potential benefits of rescue HFOV. The efficacy
could only be demonstrated by changes in the oxygenation, pH and
ventilation, which improved significantly after HFOV. FiO2
were still high in the HFOV group as the oxygen requirements in most of
the babies who died were very high, inspite of HFOV and recruitment of the
lungs. Hypocarbia should be monitored closely in babies who are on HFOV
and has been associated with PVL in preterm babies [11], as two babies had
PCO2 of 18 mm Hg in the first blood gas on the oscillator (both term
babies with PPHN) and six babies had PCO2 between 20 to 30 mm Hg. There is
a need for further randomized controlled trials for rescue HFOV,
especially in countries where facilities for ECMO are not available.
Contributors: CDK conceived and designed the study,
and would act as the guarantor; PPK was responsible for analysis of the
data and drafting the paper; KS and VL was responsible for collection of
data; AVL and FS participated in protocol development and helped in
drafting the paper. The final manuscript was approved by all the authors.
Funding: None.
Competing interests: None stated.
What this Study Adds?
• High frequency oscillatory ventilation was found to improve
short term oxygenation and ventilation in neonates who failed CMV,
and was not associated with increased risk of PVL or IVH. |
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