Heliox in long-term mechanically ventilated very low birth weight
infants: still a premature treatment?
Pierantonio Santuz. MD
Paolo Biban, MD
Neonatal and Paediatric Intensive Care Unit
Division of Paediatrics
Major City Hospital
Azienda Ospedaliera Verona
Verona, Italy.
e-mail: pierantonio.santuz@azosp.vr.it
To the Editor.-
We read with great interest the article by Migliori and coll. on the use
of heliox in very low birth weight (VLBW) infants.1 Despite the paper
offers several original information, few aspects deserve a further
discussion.
The authors reported an improved gas exchange with heliox in ten long
-term ventilated VLBW infants. While the clinical relevance of 3-4 mmHg
improvement of TcpO2 and TcpCO2 remains questionable, it appears unlikely
that heliox may have been the responsible for such effect, as a
substantial physiologic background to support this thesis is still
lacking. More simply, the marked increase of minute ventilation could have
accounted for the observed blood gas changes. Actually, after three hours
of non-invasive ventilation with heliox, gas exchange slightly worsened,
with a reduction of TcpO2 despite a correspondent increase of FiO2. Yet,
this could have been due to the different level of ventilatory support
provided (invasive versus non-invasive mode).
Nonetheless, the paper raises a very intriguing issue: why such a
marked augmentation of minute ventilation occurred in these patients while
ventilated with heliox (about 44% increase)? Is this remarkable effect
directly ensuing from heliox? This is a central question, because the
reduction of energy expenditure due to lower resistive work of breathing
could be offset by this relative hyperventilation (RR increased from 45.9
to 55.6 before and after 60 minutes of heliox, respectively). By the way,
with such relatively high RR variation one might expect an even greater
effect on CO2 (TcpCO2 decreased just from 52.3 to 49.1 mmHg).
Another interesting observation concerns the sustained improvement of
respiratory function, allowing seven out of eight patients to remain
extubated after a brief period of non-invasive heliox ventilation. Given
heliox has apparently no curative effects, it is unclear the mechanism by
which these VLBW patients may have benefited from such treatment. The lack
of a control group obviously precludes any further comment on this point.
In conclusion, we believe that good physiologic results must be
distinguished from true benefits for the patient.2 The presented data do
not demonstrate a clear effectiveness of heliox in reducing the need of
ventilatory support and improving gas exchange in preterms infants.
Migliori and coll. must be certainly congratulated for conducting an
interesting study in a small but quite complex group of patients. However,
further research is still needed to better define the clinical role of
heliox, if any, in ventilated VLBW infants.
REFERENCES
1. Migliori C, Gancia P, Garzoli E, Spinoni V, Chirico G. The effects
of helium/oxygen mixture (heliox) before and after extubation in long-term
mechanically ventilated very low birth weight infants. Pediatrics 2009
Jun;123:1524-1528.
2. Kavanagh BP, Meyer LJ. Normalizing physiological variables in
acute illness: five reasons for caution. Intensive Care Med. 2005; 31:1161
-1167.
Conflict of Interest:
None declared
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