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Editor,—We read with interest the excellent review article by Anthony Cross1 on the subject of non-invasive ventilation (NIV) in the emergency department but would like to make the following comments.
There is little evidence to support the conclusion that NIV is “extremely useful in an emergency department setting in the first line treatment of acute respiratory distress”. As Cross points out, most of the trials in this area have been performed in an intensive care or high dependency setting where the patients were been selected by virtue that other treatments had failed. Many patients presenting to accident and emergency (A&E) with acute respiratory distress will get better after initiation of other treatments such as bronchodilators and controlled oxygen therapy (in the case of chronic obstructive airway disease (COAD)) or oxygen, nitrates and diuretics (in the case of acute pulmonary oedema). In a study of 954 COAD patients presenting to A&E in Leeds, only 25% were acidotic on arrival and of these 25% had completely corrected their pH by the time they arrived on the ward.2 Similarly, in an audit of 104 patients presenting to A&E in Leeds with acute pulmonary oedema, who were all acidotic on arrival (pH <7.35), 89% improved both clinically and in terms of arterial pH before leaving A&E (unpublished data).
Cross points out that NIV has been shown to “decrease the need for endotracheal intubation”. However, these data are derived from trials in which the intubation rate for the controls is usually very high (up to 74% in studies of COAD patients3 and up to 60% in those with patients presenting with acute pulmonary oedema4). It is almost inevitable that NIV will reduce the intubation rate when the rate is already so high in the controls. In our audit in A&E departments in Leeds, only 11% of severe acute pulmonary oedema patients (respiratory rate >23/min and pH <7.35) were intubated after the usual therapy for this condition. It is much less likely that NIV, in the A&E department, would reduce this low intubation rate significantly.
Cross also suggests that “early intervention [with NIV] may avoid the risks and complications of endotracheal intubation”. There is no doubt that the complication rate has been shown to be reduced by NIV in published studies,3 but in others a non-significant trend towards increased mortality in those treated with NIV has been shown and attributed to delays in intubation.5 It is important, therefore, to point out that NIV is not a substitute for intubation but may delay or prevent it becoming necessary in a carefully selected group of patients.
Two other points not discussed in the review are also important. Firstly, like everything else in A&E practice, there are training issues to consider when new or unfamiliar techniques, such as NIV, are used. Both doctors and nurses need to know when and how to use particular equipment and, perhaps more importantly, when not to. In particular they need to be fully trained in all the possible complications of NIV. A&E staff may not use the technique regularly and so skills will decay without proper training schemes in place.
Secondly, many of the NIV machines currently on the market do not come with a battery pack, and this may present difficulties when transfer to the ward or intensive care is required by a patient who has been started on NIV in the A&E department. Some patients (particularly those with COAD) will have a prolonged requirement for NIV and it is, therefore, important to consider investing in an NIV machine that can run from a battery.
In summary, most patients presenting to A&E with respiratory distress do not need ventilatory support. For those that do, endotracheal intubation and mechanical ventilation remains the gold standard. For a small group of patients with chronic lung disease needing urgent ventilatory support, NIV may be first line treatment. Chronic positive airway pressure undoubtedly has a role in patients with acute pulmonary oedema.
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