Correspondence
High-Frequency Ventilation
N Engl J Med 2003; 348:1181-1182March 20, 2003
- Article
To the Editor:
In the studies of high-frequency ventilation reported in the August 29 issue by Johnson et al.1 and Courtney et al.,2 there were important differences in the application of conventional ventilation in the control groups, which may explain why these trials had conflicting results. The trial by Johnson et al. required conventional ventilation to be started at a rate of 60 breaths per minute, in accordance with previous studies of optimal mechanical ventilation.3,4 Courtney et al., however, set 60 breaths per minute as the maximal rate, which made it likely that lower rates and therefore higher tidal volumes were used in most of their patients. This was aggravated by the universal use of flow sensors, because the additional 1 ml of dead space must be compensated for by higher tidal volumes in order to maintain the desired partial pressure of carbon dioxide. Thus, higher-than-necessary tidal volumes put the control group at a disadvantage. Strictly speaking, the trial by Courtney et al. shows only that high-frequency ventilation is superior to synchronized ventilation with a flow sensor and rates of less than 60 breaths per minute.
We have demonstrated that conventional ventilation, with the ventilatory pattern optimized to achieve minimal peak inspiratory pressure by starting with at least 60 breaths per minute, can match high-frequency ventilation in terms of the outcome (a 69 percent rate of survival without chronic lung disease with each approach).5 These results are confirmed by Johnson et al.1
5 ReferencesUlrich H. Thome, M.D.
Frank Pohlandt, M.D.
University Children's Hospital, 89070 Ulm, Germany
uhthome@web.de 1
Johnson AH ,Peacock JL ,Greenough A , et al. High-frequency oscillatory ventilation for the prevention of chronic lung disease of prematurity. N Engl J Med 2002;347:633-642
Full Text | Web of Science | Medline2
Courtney SE ,Durand DJ ,Asselin JM ,Hudak ML ,Aschner JL ,Shoemaker CT . High-frequency oscillatory ventilation versus conventional mechanical ventilation for very-low-birth-weight infants. N Engl J Med 2002;347:643-652
Full Text | Web of Science | Medline3
Oxford Region Controlled Trial of Artificial Ventilation OCTAVE Study Group
CrossRef | Web of Science | Medline4
Pohlandt F ,Saule H ,Schroder H , et al. Decreased incidence of extra-alveolar air leakage or death prior to air leakage in high versus low rate positive pressure ventilation: results of a randomised seven-centre trial in preterm infants. Eur J Pediatr 1992;151:904-909
CrossRef | Web of Science | Medline5
Thome U ,Kossel H ,Lipowsky G , et al. Randomized comparison of high-frequency ventilation with high-rate intermittent positive pressure ventilation in preterm infants with respiratory failure. J Pediatr 1999;135:39-46
CrossRef | Web of Science | Medline
To the Editor:
Courtney et al. report that infants assigned to high-frequency oscillatory ventilation were successfully extubated earlier than infants assigned to conventional ventilation. The proportion of infants who were alive without chronic lung disease was 56 percent in the group treated with high-frequency oscillatory ventilation, as compared with 47 percent in the group treated with synchronized intermittent mandatory ventilation. The authors state that the study protocol required extubation in the group treated with synchronized intermittent mandatory ventilation “when infants' condition had been stable for 6 to 12 hours while they were receiving minimal ventilatory support . . . the FiO2 [fraction of inspired oxygen] was no more than 0.25 and mean airway pressure no more than 5 cm of water.” The criterion for the mean airway pressure appears to be too conservative in comparison with current practices in tertiary neonatal intensive care units, where infants are generally extubated at a higher mean airway pressure than in this study. The finding that the infants treated with high-frequency oscillatory ventilation were successfully extubated earlier than those treated with synchronized intermittent mandatory ventilation — a significant difference — might be attributable to this.
Furthermore, there was a small but significant drop in the incidence of chronic lung disease in the group treated with high-frequency oscillatory ventilation. It will be interesting to see whether the investigators follow these infants further and report the neurodevelopmental outcome at one or two years of age. Such data would show whether a drop in the incidence of chronic lung disease reflects an improved long-term neurodevelopmental outcome in infants treated with high-frequency oscillatory ventilation. To answer the question of whether high-frequency oscillatory ventilation is truly a better ventilation strategy, future studies should use the long-term neurodevelopmental outcome as the primary outcome measure.
Nandkishor S. Kabra, M.D., D.M.
McMaster University, Hamilton, ON L8N 3Z5, Canada
nskabra@netscape.net Author/Editor Response
As Drs. Thome and Pohlandt point out, there were significant differences between the conventional ventilation strategies that we used and that Johnson et al. used. Our choice of a synchronized mode with tidal-volume monitoring was based on several factors. It is well known that ventilator-induced lung injury may result from volutrauma.1 We therefore chose a form of conventional ventilation that provided tidal-volume monitoring and made careful adjustment of tidal volumes a key part of our ventilation strategy. Flow-triggered systems with monitoring at the endotracheal tube have been shown to deliver more consistent tidal volumes than intermittent mandatory ventilation or impedance triggering, resulting in reduced fluctuations in blood pressure, improved gas exchange, and decreased asynchrony.2 We agree with Drs. Thome and Pohlandt that the increase in dead space may result in slightly higher values for the partial pressure of carbon dioxide.
We agree that our study showed that high-frequency oscillatory ventilation was superior to synchronized ventilation with tidal-volume monitoring; it is difficult to extrapolate this finding to include high-rate nonsynchronized ventilation. However, it should be pointed out that the rate of survival without chronic lung disease was lower in both groups in the trial reported by Johnson et al. (33 percent) than in either group in our trial (the group treated with synchronized intermittent mandatory ventilation, 47 percent; the group treated with high-frequency oscillatory ventilation, 56 percent).
There were also key differences in the management of high-frequency ventilation between our trial and both the trial of Johnson et al. and that of Thome et al.3 In our trial, high-frequency oscillatory ventilation was provided only with the SensorMedics 3100A, a device that functions differently from the Infant Star (used in the trial by Thome et al.) and the other high-frequency ventilation devices used in the trial of Johnson et al. In addition, our trial was designed so that infants randomly assigned to high-frequency oscillatory ventilation continued to receive it until they were extubated; they were not crossed over to conventional ventilation.
Dr. Kabra's observation that we extubated infants at settings lower than those currently used in many intensive care nurseries is probably correct. There has been a gradual shift toward earlier extubation over the past five years. However, there is no reason to believe that this was a systematic bias in our study. We agree that assessment of the long-term developmental outcome is extremely important.
3 ReferencesSherry E. Courtney, M.D.
Schneider Children's Hospital, New Hyde Park, NY 11040David J. Durand, M.D.
Jeanette M. Asselin, R.R.T., M.S.
Children's Hospital and Research Center, Oakland, CA 94609
scourtne@lij.edu 1
Clark RH ,Slutsky AS ,Gerstmann DR . Lung protective strategies of ventilation in the neonate: what are they? Pediatrics 2000;105:112-114
CrossRef | Web of Science | Medline2
Hummler HD ,Gerhardt T ,Gonzalez A , et al. Patient-triggered ventilation in neonates: comparison of a flow- and an impedance-triggered system. Am J Respir Crit Care Med 1996;154:1049-1054
Web of Science | Medline3
Thome U ,Kossel H ,Lipowsky G , et al. Randomized comparison of high-frequency ventilation with high-rate intermittent positive pressure ventilation in preterm infants with respiratory failure. J Pediatr 1999;135:39-46
CrossRef | Web of Science | Medline
- Citing Articles (1)
Citing Articles
1
Anton H. van Kaam, Peter C. Rimensberger, Dorine Borensztajn, Anne P. De Jaegere. (2010) Ventilation Practices in the Neonatal Intensive Care Unit: A Cross-Sectional Study. The Journal of Pediatrics 157:5, 767-771.e3
CrossRef
