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ARTICLE IN PRESS Neuromuscular Disorders xx (2003) xxx–xxx www.elsevier.com/locate/nmd Workshop report 117th ENMC Workshop: Ventilatory Support in Congenital Neuromuscular Disorders — Congenital Myopathies, Congenital Muscular Dystrophies, Congenital Myotonic Dystrophy and SMA (II) 4–6 April 2003, Naarden, The Netherlands Carina Wallgren-Petterssona,*, Kate Bushbyb, Uwe Melliesc, Anita Simondsd aThe Folkha¨lsan Department of Medical Genetics, University of Helsinki, P.O. Box 211, Topeliuksenkatu 20, FIN-00251 Helsinki, Finland bInstitute of Human Genetics, University of Newcastle upon Tyne, Newcastle upon Tyne, UK cDepartment of Pediatrics and Pediatric Neurology, University of Essen, Essen, Germany dRoyal Brompton & Harefield NHS Trust, London, UK Received 19 August 2003 Eighteen participants from Australia, Austria, Denmark, function in order to generate recommendations for assess- Finland, France, Germany, The Netherlands, the UK, and ment of respiratory function in children with NMD the USA met in Naarden, representing a variety of (Appendix A). disciplines with experience in the respiratory management of patients with neuromuscular disorders (NMD). The aims 1.1. Lung and respiratory muscle function of the workshop were to agree upon and report minimum recommendations for the investigation and treatment of The literature on the assessment of lung function and respiratory involvement in congenital muscular disorders, respiratory muscle function was reviewed by Dr Laier- and to identify areas where further research is needed. The Groeneveld (Erfurt, Germany). Routine measurements of workshop specifically excluded patients with Duchenne respiratory function include static lung volumes, flows and muscular dystrophy where evidence for the need for and indices of gas exchange. If respiratory muscle weakness is efficacy of the treatment of respiratory failure is better suspected because of the underlying disease or abnormalities established. All participants contributed to the review and in the initial investigation, measurements may be completed assessment of published evidence in the field, and current by direct tests of the respiratory muscle function. In children practice amongst the group was also compared. Despite the with NMD monitoring of respiratory status is particularly individual rarity of the conditions under consideration in important because respiratory malfunction is often progress- this workshop, the accumulated experience of the group ive and a major cause of morbidity and mortality. represented the care of more than 545 patients with these However, data on the natural history of lung and disorders, of whom around one-third were receiving respiratory muscle function in children with congenital mechanical ventilation. NMD are scarce and some of the techniques to assess respiratory muscle function lack validation and normal values. 1. Session 1—Assessment methodologies in childhood Apart from the well-validated measurement of vital respiratory impairment capacity (VC) and blood gas tensions the following non- invasive techniques are available to assess the respiratory The first session addressed the rationale for commonly muscles in children. Based on their feasibility they are of performed measurements of various aspects of respiratory different importance in routine clinical use: * Corresponding author. Tel.: þ358-9-315-5521; fax: þ358-9-315-5106. † Maximum inspiratory pressure ðPImaxÞ and maximum E-mail address: carina.wallgren@helsinki.fi (C. Wallgren-Pettersson). expiratory pressure ðPEmaxÞ measured at the mouth can be 0960-8966/$ - see front matter q 2003 Published by Elsevier B.V. doi:10.1016/j.nmd.2003.09.003 ARTICLE IN PRESS 2 C. Wallgren-Pettersson et al. / Neuromuscular Disorders xx (2003) xxx–xxx obtained at approximately 6–7 years of age. Pressures 1.2. Sleep-disordered breathing increase with age and are higher in boys than in girls [1, 2]. The variability of normal values and the dependence Dr Mellies (Essen, Germany) reviewed the techniques on cooperation by the child makes the assessment of the available for the detection and assessment of sleep- individual child difficult and requires some practice and disordered breathing (SDB) and its significance in NMD. experience with the technique. SDB is common in NMD [12,13]. The principal cause is † Nasal sniff pressures ðPsnÞ is an established test of disease-related loss of respiratory muscle function, which in inspiratory muscle strength in adults and has been the setting of sleep-induced reduction of respiratory muscle applied to children. It is a simple and non-invasive tone and drop of central drive results in limited capacity to measure, particularly of the diaphragm, and normal compensate for sleep-related drop of alveolar ventilation. values for children are available [3,4]. SDB is particularly prevalent in REM sleep [14–16],a † Mouth occlusion pressure ðP0:1Þ is measuring the period of maximal muscle atonia, and in the presence of pressure generated by the inspiratory muscles during diaphragm dysfunction [6]. It can manifest in different tidal breathing and allows estimation of the respiratory ways, depending on the relative contribution of upper = drive and the ratio P0:1 PImax is representing the load of airway or diaphragm dysfunction. Hypopneas with desa- respiratory muscles. It has been shown that these turations in REM sleep are most common, particularly in the measures are closely correlated with angle of scoliosis, early stages. As the disorder progresses, hypercapnic VC and gas exchange and may indicate respiratory alveolar hypoventilation, first in REM, then in non-REM muscle fatigue [5–8]. The technique requires specifically sleep prevails as the predominant marker of decreasing trained personnel and special equipment; it may play a respiratory muscle force. For adults with myopathies and role in scientific questions. Normal values for children children with various NMD it has been shown that the are available [2,9]. degree of ventilatory restriction impacts directly on pattern and severity of SDB and that SDB-onset, nocturnal There are further, more invasive or sophisticated hypoventilation and respiratory failure can be reliably techniques, e.g. phrenic nerve stimulation, measurement predicted from simple spirometry [7,17]. of oesophageal pressure, electromyography to assess the Because nocturnal hypoventilation is likely to advance to respiratory muscle function. However, their applications the development of cor pulmonale and daytime respiratory may be restricted to the research setting and have not been failure and may impact unfavourably on survival, timely described in children with NMD. recognition is important [18–21]. On the basis of data obtained from adults with various Unfortunately, SDB is rarely apparent on daytime conditions including NMD the ATS/ERS Statement on presentation. Symptoms may be subtle and non-specific respiratory muscle testing [10] concluded among others and recently it has been shown that a structured symptom that: questionnaire failed to predict SDB in children with advanced NMD [16]. A high index of suspicion is required † Respiratory muscle weakness reduces VC. and if diagnosis cannot be confirmed by simple tests such as † Expiratory muscle weakness can increase residual overnight pulse oximetry additional polysomnographic capacity. evaluation may be indicated [22]. † Reduction of chest wall and lung compliance, as a consequence of muscle weakness, reduces lung volumes, 1.3. Conclusions notably VC. † A fall in VC in the supine position, compared with when The guidelines developed through discussion upright, suggests severe diaphragm weakness or (Appendix A) were agreed as the minimum necessary to be paralysis. able to predict safely the development of respiratory failure. † Reduced maximal flows in NMD may reflect poor The recommendations focus on detecting change in respira- respiratory muscle coordination. tory muscle strength, ability to cough, overnight oximetry † PaO2 and PaCO2 are affected by muscle weakness. and the presence of subtle symptoms of SDB. VC is a key † Respiratory muscle weakness may cause desaturations investigation which should be performed regularly in all of and hypercapnia during REM sleep. these patients as VC below 60% expected is a good predictor of the onset of SDB and VC below 40% is a good predictor of The ability to cough depends on VC, expiratory muscle nocturnal hypoventilation. strength and bulbar muscle function. Therefore peak cough PCF less than 160–200 l/min may be also ineffective in flows (PCF) are an indirect indicator of lung and children and patients are at risk for recurrent chest respiratory muscle function; PCF can be measured with a infections and respiratory failure. Absence or presence simple asthma peak flow meter and in adults a minimum and severity of nocturnal desaturations reflect respiratory PCF above 200 l/min can usually clear airway secretions reserve and can be detected with overnight oximetry in adequately [11]. most cases. Deterioration in these key parameters should ARTICLE IN PRESS C. Wallgren-Pettersson et al. / Neuromuscular Disorders xx (2003) xxx–xxx 3 be the indication for further more specialised investigations insufficiency. Patients who have a cough peak flow rate including polysomnography and arterial or capillary blood (PFR) above 4.5 l/s can usually clear bronchial secretions gas estimation. adequately and are not at risk of developing respiratory decompensation during upper respiratory tract infections. Once cough PFR falls below this

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