In vivo characteristics of respiratory neuromuscular responses with balloon catheters and skin surface EMG versus a micro transducer catheter integrated with EMG electrodes

In vivo characteristics of respiratory neuromuscular responses with balloon catheters and skin surface EMG versus a micro transducer catheter integrated with EMG electrodes

Classically, transdiaphragmatic pressure (Pdi) is measured using oesophageal and gastric balloon catheters (BC) connected to pressure transducers, while skin surface electrodes measure respiratory muscle electromyography (EMG). We compared these measurements to those from a micro-transducer catheter (MC) containing two transducers and nine electromyography electrodes (MCEMG). Eight participants twice attended the laboratory. In visit one testing was conducted with the MC followed by the BC; this order was reversed in visit two. EMG electrodes were placed on the 6–8th intercostal spaces. BC and MC were positioned identically in the oesophagus and stomach. EMG, MCEMG and Pdi were evaluated in response to maximal cervical magnetic stimulation (Pdi,tw). Pdi, tw responses were quicker (P<0.05) for MC than BC for latency (26.7±3.2 vs. 42.4±2.8 ms), 10-90% rise time (47.2±8.0 vs. 68.6±7.6 ms), maximal rate of pressure development (17.3±2 vs. 12.6±1 % gain / 10 ms), half relaxation time (69.7±16.7 vs 108.3±13.8 ms) and maximal relaxation rate (8.9±2 vs. 5.6±0.7 % loss / 10 ms). Pdi, tw was higher (P<0.05) for MC than BC (32.1±8.3 vs. 24.2±5.0 cmH2O). Within day CV for Pdi, tw for MC and BC was 6.2 vs. 6.6 %, whilst between-day CV was 11.3 vs. 9.8 %. MCEMG recorded similar latencies (6.4±2.0 vs. 6.2±2.0 ms; P=0.4) and higher amplitudes (8.1±1.3 vs. 2.5±1.4 mV; P<0.05) than EMG. Within day amplitude CV for MCEMG and BCEMG was 11.2 vs. 5.6%, whilst between-day CV was 10.9 vs. 5.6 %. These results show that MC is more responsive to changes in pressure than BC while also providing a comparable diaphragm EMG signal.