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• How can one claim 'superiority' in a pilot study
  Tom Quinn
  Published on: 29 April 2016
• Re:Out-of- hospital non-invasive mechanical ventilation: discovering a new setting.
  Markus Soren Roessler
  Published on: 29 April 2016
• Out-of- hospital non-invasive mechanical ventilation: discovering a new setting.
  Antonio Esquinas
  Published on: 29 April 2016

• Published on: 29 April 2016

  How can one claim 'superiority' in a pilot study

  • Tom Quinn, Professor

  I enjoyed reading the paper by Markus S?ren Roessler and colleagues, but wondered how a claim for superiority could be made on the basis of a pilot study?

  Conflict of Interest:

  None declared

  Conflict of Interest:
  None declared.

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• Published on: 29 April 2016

  Re:Out-of- hospital non-invasive mechanical ventilation: discovering a new setting.

  • Markus Soren Roessler
  • Other Contributors:
    • Peter Michels, Oliver Schmid, Klaus Jung, J?rg St?ber, Peter Neumann, Michael Quintel, Onnen Moerer

  We thank Antonio Esquinas for his response to our article. Our rationale for NIV in the prehospital setting is based on the pathophysiology of acute respiratory failure. In acute hypoxic respiratory failure shunt is the primary underlying problem. While the application of Oxygen (+ specific medication, e.g. diuretics) may improve SpO2, the paO2/FiO2- Index will not improve, as there is no alveolar recruitment. NIV immedia...

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  We thank Antonio Esquinas for his response to our article. Our rationale for NIV in the prehospital setting is based on the pathophysiology of acute respiratory failure. In acute hypoxic respiratory failure shunt is the primary underlying problem. While the application of Oxygen (+ specific medication, e.g. diuretics) may improve SpO2, the paO2/FiO2- Index will not improve, as there is no alveolar recruitment. NIV immediately leads to alveolar recruitment and therefore improved oxygenation. In acute hypercapnic respiratory failure fatigue of the respiratory muscles causes hypercapnia. NIV (PEEP + pressure support) unloads respiratory muscles at least partially while a sufficient tidal volume is generated. The benefits of NIV are well documented [1]. Furthermore, since out-of-hospital intubation is associated with an increased risk for airway management problems, morbidity and mortality may already be reduced by avoiding endotracheal intubation [2]. In this study the number of patients with COPD (n=18, 11 SMT group + 7 NIV group) was lower and not higher than the number of patients with ACPE (n=25, 13 SMT group +12 NIV group). Only in those patients where ACPE respectively COPD has been the leading cause for ARF and has been combined with another respiratory affection, the number of patients with COPD was - statistically not significant - higher (COPD n= 11, ACPE n =6). We therefore think that it is hypothetical that this did influence the results of this study. According the methodology we understand the considerations of Esquinas. It is correct that we used patients comfort as one of the parameters to adapt the NIV settings and we are aware that this parameter does not allow quantification. But dyspnoe scores often also quantify only the subjective perception of the patient. We agree that tidal volume should be observed. But it must be recognized that this parameter may be incorrect if the mask seals not tightly and there is a leakage. Furthermore some systems - especially pure CPAP-systems - do not allow to measure tidal volume. In the methods section, we have listed the physiological parameters that defined the need for an ICU therapy in patients with ARF. We did not list all possible causes that my lead to an ICU admission. We could have excluded the patients mentioned. But they were treated in the prehospital phase either with SMT or with NIV due to ARF despite the fact that further diagnoses were found. Since the same number of patients has been affected in each group we do not think that this biased our results. Unfortunately we do not understand the final point adressed by Esquinas, that patients with oxygen therapy (we guess standard medical therapy [SMT] is meant) had a worse clinical course but were not admitted to ICU. Patients with SMT stayed longer in the hospital, were more often and longer in an ICU and had more ventilator days and hours. We agree that it would be worth to discuss and explain the different evolution. But the primary purpose of this study has been to evaluate whether OOH NIV is safe, feasible and more effective when compared with SMT. This question has been answered positively for NIV and we attribute the better in- hospital course to the more effective therapy of ARF with NIV. Adressing this issue as well would have busted both, intention and length of our publication.

  [1] Sch?nhofer B, Kuhlen R, Neumann P, Westhoff M, Berndt C, Sitter H. Non-invasive ventilation as treatment for acute respiratory insufficiency. Essentials from the new S3 guidelines. Anaesthesist 2008 Nov;57(11):1091-102.

  [2] Timmermann A, Russo SG, Eich C, Roessler M, Braun U, Rosenblatt WH, Quintel M. The out-of-hospital esophageal and endobronchial intubations performed by emergency physicians. Anesth Analg. 2007;104:619- 623.

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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• Published on: 29 April 2016

  Out-of- hospital non-invasive mechanical ventilation: discovering a new setting.

  • Antonio Esquinas, Dr.

  Title: Out-of- hospital non-invasive mechanical ventilation: discovering a new setting.

  Antonio M. Esquinas MD, PhD, FCCP International Fellow AARC Intensive Care Unit Hospital Morales Meseguer Avenida Marques de los velez s/n Murcia, 3008 Spain Phone:+34609321966 FAX:+34968232484 E-mail: antmesquinas@gmail.com

  Key words: non invasive mechanical ventilation; out-of-hospital.

  To editor:...

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  Title: Out-of- hospital non-invasive mechanical ventilation: discovering a new setting.

  Antonio M. Esquinas MD, PhD, FCCP International Fellow AARC Intensive Care Unit Hospital Morales Meseguer Avenida Marques de los velez s/n Murcia, 3008 Spain Phone:+34609321966 FAX:+34968232484 E-mail: antmesquinas@gmail.com

  Key words: non invasive mechanical ventilation; out-of-hospital.

  To editor:

  Non invasive mechanical ventilation (NIV) is a technique with increasing application in out-of-hospital settings for conditions such as acute cardiogenic pulmonary oedema (ACPO) 1. Rationale of this application appears to be based on the body of evidence from the emergency department (ED) setting, with the assumption that earlier administration in selected conditions could improve hospital outcome and avoid endotracheal intubation 2. These original prospective controlled trials by Roessler MS et al. explore the use of NIV in out-of- hospital settings 3. We felt obliged to comment on some of these results and methodology of NIV in prehospital application: First, COPD was prominent. Although not statistically significant, there were a greater number of patients with COPD and this condition could influence evolution 3. Secondly, some aspects of the methodology of prehospital NIV: a) authors use "comfort" as as an indicator to guide the application of the NIV protocol, but other parameters such as tidal volume should also be utilized; b) All the criteria for admission to the ICU of patients in both groups are not completed. One subgroup of patients who were finally admitted to ICU contained a patient with a pneumothorax, which (like pulmonary embolism) should be excluded from NIV. In these situations a delay in early diagnostic and NIV results are conflicting or limited recommendation; c) Patients receiving oxygen therapy had a worse clinical course but was not admitted to the ICU. The different evolution and proposed explanations are not evaluated or explained.

  For further studies, relevant data not examined in the study to be considered: a) the out-of-hospital transport time could affect the results with both strategies, NIV or implementing oxygen therapy; b) There is heterogeneity but no significant of diagnoses in patients receiving with NIV compared to oxygen, which could interfere with the final conclusions.

  References:

  1. Simpson PM, Bendall JC. Prehospital non-invasive ventilation for acute cardiogenic pulmonary oedema: an evidence-based review. Emerg Med J. 2011 Jul; 28 (7):609-12.

  2. Bolton R, Bleetman A. Non-invasive ventilation and continuous positive pressure ventilation in emergency departments: where are we now? Emerg Med J.2008 Apr; 25 (4):190-4.

  3. Roessler MS, Schmid DS, Michels P, Schmid O, Jung K, St?ber J, Neumann P,Quintel M, Moerer O. Early out-of-hospital non-invasive ventilation is superior to standard medical treatment in patients with acute respiratory failure: a pilot study. Emerg Med J. 2012 May;29 (5):409 -14.

  Abbreviations list:

  ACPO: acute cardiogenic pulmonary oedema COPD: chronic obstructive pulmonary disease. ED: emergency department ICU: intensive care unit NIV: non-invasive mechanical ventilation

  Conflict of Interest:

  None declared

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  Conflict of Interest:
  None declared.

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