positive airway pressure (CPAP) is an important treatment modality for
respiratory distress syndrome (RDS) in neonates. It can be applied via a
face mask, nasopharyngeal tube, or nasal prongs, using a conventional
ventilator, bubble circuit or a CPAP driver.
Bubble CPAP (bCPAP) is one of the low cost nasal CPAP
delivering systems, with underwater seal. CPAP delivered by underwater
seal causes vibration of the chest due to gas flow under water; and these
vibrations simulate waveforms produced by high frequency ventilation. Lee,
et al.(1) demonstrated the superiority of bubble CPAP as
compared to ventilator derived CPAP in premature infants. Bubble CPAP is
also a less expensive method of respiratory support, most suitable to
neonatal units with limited resources in developing countries(2). We
evaluated the effectiveness of bubble CPAP as a simple and non-invasive
option in a developing country.
This prospective observational study was conducted at
Neonatal ICU, MS Ramaiah Medical College and Teaching Hospital. 50 babies
requiring respiratory support for RDS were included in this study.
Indication for CPAP included (i) FiO2
>0.4 to maintain PaO2
³60 mmHg associated with pH <7.25;
and (ii) PaCO2 >50 mmHg; and Downes score
Mechanical ventilation was considered for failure of CPAP i.e., in
babies with worsening clini-cal symptoms of RDS, or those with PaO2
<50mmHg or PaCO2 >60 mmHg with FiO2 >0.6 and MAP of 8.
Based on radiological findings, severity of RDS(4) was
graded as mild, moderate or severe. Babies with respiratory distress
secondary to asphyxia, meconium aspiration, sepsis, necrotising
enterocolitis and congenital anomalies, were excluded.
The Fisher and Paykel Bubble CPAP involves a source of
gas flow (6-8L/min), an air oxygen blender, humidifier, and respiratory
circuit. The expiratory end of which is inserted in a bottle of water.
CPAP level delivered is equivalent to the distance that the distal end of
expiratory tubing is underwater.
Data were analyzed using Chi-square test for comparison
of proportions and Student ‘t’ test to compare means between two
groups. P value <0.05 was considered as significant.
Bubble CPAP proved to be effective in 40 (80%) out of
total 50 babies; 10 babies required positive pressure ventilation. Their
details are summarized in Table I. The mean (SD) age at
admission was 3.6 (3.7) hours (range 1-28 h), and at initiation of
treatment was 5.5 (3.9) h. The mean duration of treatment in ‘success’
group was 30.8±8.6h (range, 18-70 h).
Patient Characteristics and Response to Bubble CPAP Therapy
Effectiveness of bubble CPAP was judged using Downes
score(5). Out of 16 babies who had Downes score 4 at initiation of BCPAP,
after 6 hour, 12 (75%) babies had a score of <4 and 4 (25%) babies had a
score of >6, which was found to be statistically significant. 31 babies
had a score of 5 before initiation of BCPAP and after 6 hrs 25 (80%) had
improved to a score of 4 or less and 6 (20%) had a score of more than 6 (P
<0.05). Three babies had a score of 6 initially, and all of them
improved by 6 hrs. Thus, there was a marked improvement in Downes score
following bubble CPAP therapy in newborns with RDS. FiO2
requirement also reduced significantly and there was an increase in PaO2
levels in babies who responded to bubble CPAP therapy. Surfactant was used
only in the neonates who failed bubble CPAP and required ventilation. A
total of 5 infants had PDA (2 in failure group and 3 in success group).
None of the babies developed pneumo-thorax. The success rate of BCPAP in
mild (n=6, 12%), moderate (n=29, 59%) and severe (n=15,
30%) RDS was 100%, 93.1% and 46.6% respectively.
Role of CPAP in preterm and low birthweight infants is
well documented(6-9). In our study, statistically significant success was
observed in preterms born between 32-34 weeks and in infants with
birthweight between 1000-1500g. Our observations were simi-lar to other
reports of effectiveness of nasal CPAP. In this study, outcome of bCPAP
did not vary between genders. Sandri, et al.(10) have shown higher
need for respiratory assistance in male
infants with RDS.
Bubble CPAP was effective in treating mild and moderate
grade RDS whereas, in a study conducted by Boo, et al.(3), moderate
RDS was one of the predictors of failure of CPAP. We also found
statistically significant improvement in Downes score after application of
Bubble CPAP. The success in our study in managing moderate RDS may be
related to early initiation of BCPAP at a Downes score of 4. Further
larger trials may help to confirm this observation.
Establishing a NICU with mechanical ventilation would
require high level of expertise and trained personnel, which is far from
reality in many of the peripheral and district hospitals in developing
countries. Lanieta, et al.(2) have successfully demonstrated
the usefulness of bCPAP in a developing country, and have also reported
the cost effectiveness with use of Bubble CPAP(2). Pieper, et al.(11)
have shown the importance of CPAP in the absence of neonatal intensive
care and also the improved outcome in neonates treated with CPAP prior to
transfer to a tertiary unit. Bubble CPAP, thus, may be considered as a
primary mode of respiratory support in resource poor settings.
Director Professor David Tudehope; Deputy Director Dr
Peter Gray, Andrew Shearman, Respiratory scientist, and the nursing staff
of Division of Neonatology, Mater Mothers Hospital, Brisbane Australia for
their guidance and technical support.
Contributors: PSU conceptionalised, designed,
analysed and is the guarantor for study. FK Collected and analysed data.
PSU and FK were involved in preparation of manuscript. PPM provided
suggestions for preparation of manuscript.
Competing interests: None stated.
What This Study Adds?
• Bubble CPAP is a simple and effective means of
primary respiratory support for management of mild and moderate
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