Electronic Supplementary Material
Fig.1 Multimodal bedside approach to suspected diaphragm palsy causing respiratory failure after spinal cord injury. Diaphragm palsy can be suspected according to topographical distribution of spinal cord lesion documented at Magnetic Resonance Imaging (MRI) from C2 to T1 performed on day 1 (T2 weighted sequence, Panel A). On day 7, Chest X ray(Panel B) showed retrocardiac consolidation and Electrical Impedance Tomography showed lung lower left severe hypoventilation (Panel C). Lung ventilation abnormality was associated to left diaphragm dysfunction, as highlighted by the reduction of left hemidiaphragm thickness and fractional thickening at ultrasonography (US, Panel D). Finally, the absence of electrical activity from left hemidiaphragm at Surface Electromyography (sEMG, Panel E) provides the diagnosis of functional denervation.
Methods of Surface Electromyography of respiratory Muscles (sEMG) recording.
Patient was studied during Continuous Positive Airway Pressure (CPAP) performed thought a full-face mask. An air-filled pressure transducers were connected to the airway opening for simultaneous airway pressure recording. sEMG signals were collected through four pairs of surface electrodes (Kendall, Tyco Healthcare, NL) positioned according the following scheme (Fig. 2):
1. Lower costal margin, bilaterally on the midclavicular line, for right and left diaphragm.
2. Second intercostal space, bilaterally on the parasternal line, for right and left parasternal external intercostal muscles.
sEMG electrodes were connected to the physiological amplifier device Dipha 16 (Inbiolab, Groningen, NL) which amplified (gain 20), prefiltered between 0 and 200 Hz, sampled at 500 Hz and then wirelessly transmitted sEMG signals to a dedicated acquisition system. After amplification and analogic filtering (first order low pass with 5 kHz cut-off frequency) the physiological amplifier internally sampled with 25 kHz per channel, performing 50 times oversampling, to finally reach a sampling frequency of 500 Hz with very low noise level. Data were continuously recorded during the study and stored on a hard drive for off-line analysis by a dedicated device and software (Draeger Medical, Luebeck, Germany). Raw sEMG signals were post-processed by freeing them from ECG artefacts (QRS complexes) using a gating procedure. After that the signals were weighted root-mean-squared (RMS) over a 250 milliseconds period. Traces were off-line analysed using LabChart (ADInstruments, New Zeeland).
Fig.2 Surface Electromyography electrodes scheme and corresponding processed traces for bilateral emidiaphragms and intercostal muscles.