Aanem Monograph Noninvasive Respiratory Management and Diaphragm and Electrophrenic Pacing in Neuromuscular Disease and Spinal Cord Injury

The purpose of this monograph is to describe noninvasive management of respiratory muscle weakness/paralysis for patients with neuromuscular disease (NMD) and spinal cord injury (SCI). Noninvasive ventilation (NIV) assists and supports inspiratory muscles, whereas mechanically assisted coughing (MAC) simulates an effective cough. Long-term outcomes will be reviewed as well as the use of NIV, MAC, and electrophrenic pacing (EPP) and diaphragm pacing (DP) to facilitate extubation and decannulation. Although EPP and DP can facilitate decannulation and maintain alveolar ventilation for high-level SCI patients when they cannot use NIV because of lack of access to oral interfaces, there is no evidence that they have any place in the management of NMD. Muscle Nerve 47: 297–305, 2013 RESPIRATORY EVALUATION AND MANAGEMENT PARADIGMS Respiratory impairment can result from either lung or airways disease, in which case pulmonary function testing (PFT) and supplemental oxygen may be appropriate. This approach is inappropriate, however, for patients with primarily ventilatory impairment. The former is characterized by hypoxia in the presence of eucapnia or hypocapnia until hypercapnia signals end-stage respiratory failure. The latter is characterized by hypoventilationinduced hypercapnia and hypoxia with risk of intercurrent episodes of acute respiratory failure (ARF) due principally to an ineffective cough. Unless the latter is distinguished from the former, unnecessary morbidity, airway cannulation, electrophrenic pacing (EPP) or diaphragm pacing (DP), and tracheotomy will result. There are 3 respiratory muscle groups: inspiratory muscles; expiratory (predominantly abdominal and chest wall) muscles, mainly for coughing; and the bulbar-innervated muscles. Although the inspiratory and expiratory muscles can be completely supported noninvasively, there are no effective noninvasive measures to counter aspiration from bulbar dysfunction. Thus, the only indication for tracheotomy in an alert neuromuscular disease (NMD) or spinal cord injury (SCI) patient is when aspiration results in persistent oxyhemoglobin saturation (SpO2) of <95% despite noninvasive ventilation (NIV) and mechanically assisted coughing (MAC). Fortunately, other than for advanced bulbar amyotrophic lateral sclerosis (ALS) patients, those with most other NMDs and SCI rarely have bulbar dysfunction to the extent that speech, deglutition, and adequate airway protection are lost, and therefore they can be managed noninvasively. Intact phrenic nerves, their anterior horn cells, and diaphragm are required for effective EPP/DP. Although EPP/DP can ventilate the lungs of patients with intact anterior horn cells, peripheral nerves, and diaphragms, as in many high-level SCI patients, EPP/DP is not indicated for ALS or other NMDs. RESPIRATORY MUSCLE AIDS Inspiratory and expiratory muscle aids include NIV and MAC for NMDs, and NIV, MAC, and EPP/DP for SCI patients. These are techniques that involve the manual or mechanical application of forces to the body, intermittent pressure changes to the airways, or electric current to the phrenic nerves or diaphragm to assist in or substitute for respiratory muscle function. Inspiratory Muscle Aids. Inspiration can be supported by negative pressure ventilation or positive pressure ventilation. The former includes negative pressure body ventilators like the iron lung, cuirass, pneumosuit, pneumowrap, pancho, and other Abbreviations: ABG, arterial blood gas measurement; ARF, acute respiratory failure; CPAP, continuous positive airway pressure; CPF, cough peak flows; DMD, Duchenne muscular dystrophy; DP, diaphragm pacing; EtCO2, end-tidal carbon dioxide; EPP, electrophrenic pacing; GBP, glossopharyngeal breathing (‘‘frog breathing’’); IAPV, intermittent abdominal pressure ventilator; MAC, mechanically assisted coughing; MIC, maximum insufflation capacity; NIF, nasal inflation pressure; NIV, noninvasive positive pressure ventilation; NMD, neuromuscular disease; PAP, positive airway pressure; PFT, pulmonary function testing; SCI, spinal cord injury; SIMV, synchronized intermittent mandatory ventilation; SpO2, oxyhemoglobin saturation (by pulse oximeter); TcCO2, transcutaneous carbon dioxide; VC, vital capacity; VFBA, ventilator/electrophrenic or diaphragm pacer, free breathing ability Correspondence to: J. R. Bach; e-mail: [email protected] VC 2012 Wiley Periodicals, Inc. Published online 28 August 2012 in Wiley Online Library (wileyonlinelibrary. com). DOI 10.1002/mus.23646