Non-invasive ventilation: how far away from the ICU?
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- Demoule, A. Intensive Care Med (2009) 35: 192. doi:10.1007/s00134-008-1351-x
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In less than 15 years, non-invasive mechanical ventilation (NIV) has become a major therapy of acute respiratory failure. The benefit of NIV is very well established in ventilatory failure resulting from acute exacerbations of chronic obstructive pulmonary disease (COPD) [1, 2] as well as in acute cardiogenic pulmonary edema . Although the benefit of NIV in “de novo” acute respiratory failure is less clear , it is well demonstrated that NIV is an effective treatment of hypoxemic respiratory failure in immunocompromised patients  . Indications for NIV are still increasing, especially in ventilator weaning  and in the post-operative setting . Consequently, growing evidence of the benefits of NIV in multiple indications has led to a major increase in NIV use [9, 10].
For safety reasons, as well as to improve the chances of success, NIV requires an appropriate environment. Elliott et al.  have defined this environment as follows: the presence of staff with training and expertise in NIV, and in adequate numbers for 24/24 cover, facilities for monitoring, and rapid access to endotracheal intubation and invasive ventilation. Obviously, the ICU setting fits all these criteria. Unfortunately, there is clearly an imbalance between ICU beds and the number of patients that need NIV. According to forecasts, this imbalance should increase in the future. Indeed, the number of patients requiring mechanical ventilation will grow continuously , while work force shortage currently forces ICU bed closure. The strong pressure on ICU beds combined with their high cost have both made NIV outside the ICU an attractive option.
What is meant by outside the ICU? The model of hospital care differs from country to country and the type of treatment undertaken in a given department differs from hospital to hospital. It is thus difficult to make close comparisons. The benefit of NIV in the emergency department has been demonstrated in acute cardiogenic pulmonary edema  but remains disputed in acute exacerbations of COPD . Achieving safe and successful NIV in the ward is another challenge. However, the study by Plant et al. suggested that, with adequate staff training, NIV can be applied with benefit in the general respiratory ward with the usual ward staff . The proximity of a respiratory ICU obviously facilitates the feasibility of NIV in the ward . Furthermore, recent North-American surveys have shown that NIV outside the ICU was becoming a widespread practice [17, 18, 19]. This observation raises the issues of staffing and training in a general ward where nurse to patient ratio is commonly modest.
The study by Cabrini et al. published in this issue of Intensive Care Medicine  provides new interesting data on the management of NIV outside the ICU by a medical emergency team (MET). A MET is the efferent arm of a rapid response system . Their role is to identify and treat hospitalized patients with physiological instability and, therefore, prevent further adverse events. Although acute respiratory failure is one of the situations prompting a MET call, application of NIV by a MET had never been described previously. The objective of the observational study by Cabrini et al. was to describe organizational aspects, safety and short-term outcome of patients treated with NIV for acute respiratory failure outside the ICU . Patients received NIV (43% CPAP) if ventilatory support was indicated but tracheal intubation was not appropriated or immediately needed. NIV was instituted in a large variety of departments, mostly in the emergency department and in the general medicine ward, but also in various medical and surgical wards.
Their results are quite encouraging since 77% of patients avoided intubation, which is close to or better than rates reported in studies of NIV in ICUs . Obviously, the observational design of the study does not allow for confirmation that all patients who received NIV really needed NIV. Unfortunately, PaO2/FiO2 ratios are not provided which does not permit the evaluation of the severity of hypoxemia. However, patients ventilated for hypercapnic respiratory failure including acute cardiogenic pulmonary edema exhibited a high level of hypercapnia and subsequent acidosis, which suggest a deep level of hypoventilation. Unsurprisingly, NIV success rate was high in acute exacerbation of COPD and pulmonary edema, and low in pneumonia and in patients with hematological diseases.
Apart from the success rate, safety, a crucial issue for such a study, must be considered. In that respect, Cabrini et al. report very few adverse events. The 16 patients who died had all been judged as “do not attempt resuscitation”. No patient was transferred to the ICU for better monitoring and care (which, of note, might also suggest that patients were not so severe). Eventually, complications were limited to failure to accomplished the NIV program or complications related to the mask.
The study presented herein has some limitations that need to be underlined. First of all, the MET had been introduced 18 years ago in the hospital where the study was conducted. Moreover, the MET had 10 years experience in NIV outside of the ICU. Therefore, the quite encouraging results of Cabrini et al. are the fruit of a very long process. Adoption of this strategy cannot be recommended without a strong educational program. As Cabrini et al. wrote very clearly “what is effective in a hospital, can even be dangerous elsewhere”. The results of this single center study conducted by highly experienced investigators cannot be translated elsewhere without caution. The workload is another issue of this study. Indeed, the workload related to NIV has not been precisely evaluated. It is obvious that managing NIV in various wards is highly time consuming, and one would like to know more about this workload before implementing such strategy in a given hospital. The observational design of the study is a limitation that has been discussed previously. This issue might be addressed by future trials with inclusion criteria that ascertain the need for NIV. The occurrence of complications of NIV also needs to be evaluated more rigorously.
In conclusion, this pilot observational study provides valuable new data regarding the efficiency and safety of NIV management outside the ICU by a MET. Nevertheless, such strategy needs training and expertise and is not easy to translate quickly to another hospital. In a period of high pressure on ICU beds, initiation and continuation of NIV outside the ICU under the supervision of a MET is an interesting alternative. Until the benefit of this strategy has been evidenced by randomized controlled trials, we should not forget that ICU, high dependency or intermediate care units remain the best places to administer NIV. Subsequently, our duty will also be to insist on obtaining the resources required to provide the best care for our patients.