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In their recently published paper Simondset al 1 importantly emphasised the desirability of using non-invasive intermittent positive pressure ventilation (IPPV) rather than tracheostomy for optimising quality of life in patients with hypercapnic Duchenne muscular dystrophy, and suggested that the use of nocturnal nasal IPPV can help to prolong survival. They also noted that five of the 23 patients treated in this manner died from respiratory failure two years after beginning nocturnal nasal IPPV, and that most subsequent “admissions were for treatment of chest infections”. In reality, nocturnal nasal IPPV is only likely to prolong the lives of those patients who would otherwise develop hypercapnic coma as they get weaker and weaker. This is uncommon in Duchenne muscular dystrophy. In fact, 90% of episodes of respiratory failure and death in these patients occur during treatment of intercurrent chest colds2 and result from the inability to cough out secretions.3 During these episodes non-invasive IPPV often needs to be provided 24 hours a day for ventilation and for air stacking maximal breaths to assist coughing. Also, with the use of non-invasive expiratory aids such as the combination of manually assisted coughing and mechanical insufflation-exsufflation, episodes of respiratory failure and death due to respiratory failure can be virtually eliminated in patients with Duchenne muscular dystrophy. This paper, like others before it,4 ,5 misses the point that just providing nocturnal nasal IPPV is insignificant compared with supporting both the inspiratory and expiratory muscles (non-invasively) during intercurrent chest colds.
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author’s reply There is no question that support of the inspiratory and expiratory muscles is helpful in patients with Duchenne muscular dystrophy and this is stressed in the discussion in our paper. Contrary to Ishikawa and Bach’s series, over 50% of our patients presented with symptomatic diurnal hypercapnic respiratory failure without evidence of an acute chest infection. The suggestion that nocturnal nasal intermittent positive pressure ventilation (NIPPV) “misses the point” or is “insignificant” in this group is ludicrous, and a more balanced approach is required. All our patients with Duchenne muscular dystrophy are taught to carry out regular physiotherapy with assisted coughing while receiving NIPPV, as described in the methods section of the paper. NIPPV combined with physiotherapy is therefore used to support the inspiratory and expiratory muscles. There is no firm evidence as yet that any one method of assisting cough is superior. Of the five patients who died, two had elected to receive palliative care only and so were not avoidable deaths, as is implied.
Notwithstanding the above arguments, the Emerson cough insufflator-exsufflator is not currently available for purchase by hospitals in the UK/Europe as it does not have the CE mark (personal communication, J H Emerson Co). Alternatives therefore need to be explored. Although the methods described by Ishikawa and Bach clearly may be effective, it is notable that they do not give their one year and five year survival data either in the publications cited or elsewhere.