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Eur J Cardiothorac Surg 2006;30:416-417
© 2006 Elsevier Science NL

Letter to the Editor

Reply to Schädler et al.

Holger Hendrix^a,_*, Michael E. Kaiser^a, Roger D. Yusen^b,, Johannes Merk^a

^a Division of Cardiothoracic Surgery, University Hospital of Regensburg, Germany
^b Divisions of Pulmonary and Critical Care Medicine and General Medical Sciences, Washington University School of Medicine, Barnes-Jewish Hospital, St. Louis, MO, USA

Received 6 May 2006; accepted 9 May 2006.

^_* Corresponding author. Address: Justizvollzugskrankenhaus NRW, Abteilung für Chirurgie, Hirschberg 9, 58730 Fröndenberg, Germany. Tel.: +49 2373 7580; fax: +49 2373 758368. (Email: holger_hendrix{at}hotmail.com).

Key Words: Automode ventilation • Closed-loop control of ventilation • Coronary artery bypass surgery

We read with interest the letter to the editor by Schädler et al. [1] with their comments on our recent article of automated weaning patients from mechanical ventilation using the Siemens 300 A ventilator [2]. We would like to respond on these comments.

First of all, we want to comment on the major statement by Schädler et al. [1] that the results of our study are outdated and do not correspond to the modern guidelines for weaning. We do not share this opinion. The criticism that automode only enables ventilation with either mandatory ventilation or assisted spontaneous ventilation [1] is not correct, instead automode ventilation is a dynamic process. Mechanical ventilation mode automatically changes modes back and forth between mandatory mechanical ventilation and spontaneous ventilation, depending on the patients’ alertness [2]. Comparing the cited literature [3,4] as well as the references we presented, the statements of all these studies, including the statement of our study, are similar. More automated weaning decreases the work of breathing and keeps the patient in a zone of respiratory comfort that finally leads to a decreased weaning time.

The data presented in our study of course demonstrated a marked trend to a benefit for patients automatically ventilated. Patients of the automode group had a significant higher cardiac index after extubation than patients of the conventional group indicating an influence of weaning from mechanical ventilation on the cardiovascular system. Such an increase of the cardiac index, caused by weaning, in patients after cardiac surgery was also shown by De Backer et al. [5]. Furthermore, despite of group differences, the time from tracheal intubation until extubation was 2 h shorter for patients in the automode group compared with patients in the conventional group and although this was not statistically significant it was a clear difference especially because the patients in the automode group had a longer duration of the operation and thus got higher cumulative doses of fentanyl which influences the time to extubation. Therefore, in our opinion, the time from tracheal intubation until extubation chosen as a variable to determine the effectiveness of automated weaning was adequate.

In contrast to what Schädler et al. said, we think that all the information on the ventilator settings which were necessary with respect on the weaning time as a primary end-point of the study as well as on the influence of the weaning mode on the cardiovascular system, like peak airway pressure, cardiac index, tidal volume etc., were presented [2]. The other ventilator settings mentioned by Schädler et al. [1] would not have had any influence on the results or statements of our study with its protocol-guided study design [2].

Finally, we conclude that the results of our study are current and comparable to newer studies even to those cited by Schädler et al. [3,4] and do well correspond to the modern guidelines for weaning. Larger studies are indicated and could prove our statement that automode ventilator weaning leads to more rapid extubation and to a better performance of the cardiovascular system.

Footnotes

Dr. Yusen is supported, in part, by the National Heart, Lung and Blood Institute of the National Institutes of Health, grant number: 5K23HL04236-02.

References

1. Schädler D, Schmitz G, Frerichs I, Weiler N. Automatic weaning from mechanical ventilation-no progress in the last 10 years? Eur J Cardiothorac Surg 2006;30(2):415-6..
2. Hendrix H, Kaiser ME, Yusen RD, Merk J. A randomized trial of automated versus conventional protocol-driven weaning from mechanical ventilation following coronary artery bypass surgery. Eur J Cardiothorac Surg 2006;29:957-963.[Abstract/Free Full Text]
3. Lellouche F, Mancebo J, Roesler J, Jolliet P, Schortgen F, Cabello M, Bouadma L, Rodriguez P, Maggiore S, Qader S, Taille S, Brochard L. Computer-driven ventilation reduces duration of weaning: a mulitcenter randomized controlled study. Intensive Care Med 2004;30:S69.
4. Sulzer CF, Chiolero R, Chassot PG, Mueller XM, Revelly JP. Adaptive support ventilation for fast tracheal extubation after cardiac surgery: a randomized controlled study. Anaesthesiology 2001;95:1339-1345.[CrossRef][Medline]
5. De Backer D, El Haddad P, Preiser JC, Vincent JL. Hemodynamic responses to successful weaning from mechanical ventilation after cardiovascular surgery. Intensive Care Med 2000;26(9):1201-1206.[CrossRef][Medline]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Holger Hendrix Johannes Merk Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hendrix, H. Articles by Merk, J. Search for Related Content PubMed Articles by Hendrix, H. Articles by Merk, J. Related Collections Anesthesia Lung - other Coronary disease