Evidence-based or arrogance-based medicine?

We thank Drs. Herrero and Bach for their communication regarding our study looking at the efficacy of the breath-stacking technique vs. mechanical inexsufflator (MI-E) in patients with amyotrophic lateral sclerosis (ALS) (1). The authors have criticised our paper on two counts: 1) Our justification for the need of a randomised controlled trial; and 2) How non-invasive ventilation and MI-E were administered in our study. We will respond in the same order. First, we would like to draw the authors’ attention to the American Academy of Neurology practice parameters for the care of patients with ALS (2). These have indicated that although MI-E may be used in acute chest infections, the evidence to support its clinical efficacy is considered to be weak. Also, a recent Cochrane systematic review on the use of MI-E in neuromuscular disorders concluded that no good quality evidence exists to recommend the domiciliary use of MI-E in this group of patients (3). The need for a randomised controlled trial was highlighted by the authors. Recently, the UK National Institute of Health research (NIHR) called for research proposal to evaluate the clinical efficacy of MI-E in a randomised controlled trial, because of the lack of a robust evidence base to support its routine use. With regard to the way we administered NIV and MI-E, offering pulse oximetry to patients is a good approach, but our approach is to routinely assess patients in the clinic every 2–3 months for symptoms of respiratory insufficiency and monitor transcutaneous carbon dioxide levels. Where indicated we also carry out overnight oximetry/capnometry and adjust the ventilator settings as necessary to ensure adequate night-time ventilation. This approach was also used in the reported trial. As the primary aim of the trial was to assess the day-to-day domiciliary use of assisted cough techniques as a prophylactic measure, patients were instructed to use their respective devices at least twice a day and this instruction is in accordance with the manufacturer’s recommendations. Patients were encouraged to increase the use as required, especially during chest infections. Most of the patients in the study who were able to comply well with cough assist techniques used their respective devices several times a day and used MI-E at the highest possible pressure of 60 cmH2O. Similarly, patients were also encouraged to increase their use of NIV during the day-time, as their disease progressed. We have noted that Herrero and Bach are suggesting using MI-E ‘every 15 min round the clock’, which sounds impractical. In the cited paper, patients using the ‘protocol’ were instructed to use MI-E as required with no mention of using MI-E ‘every 15 min round the clock’ (4). It is also worth mentioning that, unlike some other neuromuscular conditions, ALS is a relentlessly progressive disorder and respiratory death is inevitable despite the optimal use of non-invasive respiratory support devices. We assert that in our trial NIV and MI-E were correctly prescribed and survival figures in both arms of the study were comparable or better than other studies reported in the existing literature. Our trial was not powered to detect a statistically significant difference between the treatment arms and therefore conclusions regarding the effectiveness of each device cannot yet be made. However, the study has provided valuable information to inform the design of a future larger-scale randomised study to answer these questions. We have also observed from the experience of this trial that breath-stacking can be done effectively (achieving maximal lung expansion) by many ALS