Université Catholique de Louvain
Correspondence to: Dominique Vanpee, MD, Services Des Urgences, Cliniques De Mont-Godinne, B-5530 Yvoir, Belgium
To the Editor:
Poponick et al (CHEST; July 1999)1
propose in the clinical implications that if the patient’s condition
fails to improve within 30 min after the initiation of noninvasive
ventilation, intubation and mechanical ventilation are indicated.
We agree with them that the success of treatment with noninvasive
bilevel pressure ventilation is difficult to predict using data such as
age, gender, Glasgow coma scale, acute physiology and chronic health
evaluation II, pH, and Paco2 obtained
initially before treatment in the emergency department. We agree also
that the improvement of blood gas tension is probably an important
factor for predicting the successful use of bilevel pressure
ventilation. In 1991, Meduri et al2 showed that
improvement of Paco2 (> 16%
decrease) and arterial pH (from < 7.30 to > 7.30) after the first
hour of noninvasive ventilation accurately identified those patients
who were successfully treated by this modality.
It seems that this new work cannot propose the most favorable time for
performing intubation in patients with an acute exacerbation of COPD.
For example, what were the blood gases after 10 min or after 1 h?
In this retrospective study, how can be it possible to be sure that
blood gas measurements were done exactly 30 min after the starting of
the treatment? Perhaps, for the patient without improvement after 30
min, increasing the inspiratory pressure level to 20 cm
H2O would be more favorable. Presently, there is
no consensus in the literature of the most favorable moment for
intubation in patient with an acute exacerbation of COPD. Criteria for
intubation like that proposed by Brochard et al3 could be
used in clinical practice in the emergency department.
The aim of noninvasive ventilation includes not only the correction of
hypoventilation but also the unloading of inspiratory muscles. It seems
important to consider the evolution of the respiratory work during
noninvasive ventilation. We think that the inspiratory behavior during
noninvasive ventilation is different for each patient, and that an
improvement of the blood gas tension could be obtained for some
patients at the cost of an increased inspiratory work. The control of
blood gases after 30 min is probably not sufficient to indicate
intubation at that time.
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