In conclusion, FEV 1 /FIV 1 index has a good correlation with ALSFRS-R (n = 20, r=-0.71, p < 0. 10.1136/thoraxjnl-2014-206260.341 Neural respiratory drive (NRD), measured using the parasternal intercostal muscle electromyogram (EMGpara), relates to lung disease severity as quantified by conventional methods in a range of diseases. Reference data from healthy populations are required for the technique to be used as an independent measure of lung disease severity. EMGpara has previously been expressed as a percentage of that obtained during a maximal inspiratory effort (EMGpara%max), restricting the use of the technique to subjects able to reliably perform such manoeuvres. The aim of this study was to investigate variability of both raw EMGpara (rEMGpara) and EMGpara%max in healthy adults.EMGpara was measured during tidal breathing in 43 healthy adult non-smokers (25 females, median (range) age 32 (19-79) years, mean (SD) BMI 23.4 (3.5) kg/m 2 ), using surface electrodes positioned bilaterally over the second interchondral space. Measurements were made with and without a mouthpiece/pneumotachograph in situ in 20 participants. Repeated measures were obtained within the same testing session in 27 subjects, and at least seven days later in 13 individuals. Spirometry, height, weight, BMI, fat free mass (FFM) via bioelectrical impedance and measures of regional fat distribution (waist/hip ratio and neck circumference) were also recorded.Mean (SD) EMGpara%max and rEMGpara were 5.88 (3.63)% and 5.06 (2.26)mV respectively. Significant relationships were observed between anthropometric measures and rEMGpara and EMGpara%max (Table 1). rEMGpara and EMGpara%max were unrelated to spirometry variables. Median (range) rEMGpara and EMGpara%max increased significantly with the pneumotachograph in place (4.86 (2.11-8.19)mV versus 5.62 (2.47-10.98) mV and 4.77(1.68-17.00)% versus 6.78 (2.35-20.94)%, both p < 0.0001).Analysis of variance by subject was used to assess within-subject variability. Measurement error was higher for EMGpara% max than rEMGpara (upper 95% confidence limit of difference between repeat measures of EMGpara%max 3.14%, versus 2.35 mV for rEMGpara; within-subject coefficient of variation EMGpara%max 30.8% versus rEMGpara 24.5%). rEMGpara appears to be a reproducible marker of NRD. Both rEMGpara and EMGpara%max are influenced by subjects' anthropometry. Further investigation is required to determine whether these influences are technical or physiological and must be considered when the technique is applied clinically or for research, or when developing reference values.

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Jerrard et al.: Exploring the relationship between the time until active rehabilitation and length of stay on an adult liver intensive care unit. Intensive Care Medicine Experimental 2015 3(Suppl 1):A559.

Introduction Exercise capacity in chronic obstructive pulmonary disease (COPD) is limited both by abnormal pulmonary mechanics, reported as breathlessness, and by leg muscle fatigue. To improve functional capacity it is important to understand the primary physiological constraint. Neural respiratory drive (NRD), measured using the diaphragm electromyogram expressed as a proportion of maximum (EMG di %max), quantifies the load on the respiratory muscles imposed by abnormal pulmonary mechanics, and relates closely to breathlessness. We hypothesised that end-exercise EMG di %max would be higher in patients stopping because of breathlessness than in those stopping because of leg fatigue. Methods EMG di , ventilation (V E ), oxygen consumption (VO 2 ) and ventilatory reserve (V E /MVV%) were measured in 23 COPD patients (median (IQR) FEV 1 39 (30.0 to 56.8)%predicted) during exhaustive cycle ergometry. Differences in physiological variables between groups of patients stopping because of breathlessness, leg fatigue or both were examined using 1-way ANOVA. Results EMG di %max was higher in patients stopping because of breathlessness (n = 12, EMG di %max 75.7 (69.5 to 77.1)%) than in those stopping because of leg fatigue (n = 8, EMG di % max 44.1 (39.4 to 63.3)%, p < 0.05). There were no significant differences in end-exercise V E or VO 2 . V E /MVV% tended to higher levels in the breathless group. Discussion These results suggest that patients limited by breathlessness due to ventilatory constraints can be identified as those reaching near-maximal levels of NRD during exercise. Measurement of EMG di %max during exercise could prove useful in identifying patients whose functional performance would be best optimised by improving pulmonary mechanics rather than interventions to train peripheral muscle groups. S54 NEURAL RESPIRATORY DRIVE MEASURED USING PARASTERNAL INTERCOSTAL MUSCLE ELECTROMYOGRAPHY IN PATIENTS WITH INTERSTITIAL LUNG DISEASEA Kaaba, C Jolley, v MacBean, C Reilly, S Birring, J Moxham, G Rafferty. King's College London, London, UK 10. 1136/thoraxjnl-2014-206260.60 Introduction Forced vital capacity (FVC) and gas transfer (TLCO) are often used to assess disease severity and monitor progression in patients with interstitial lung disease (ILD). Difficulty in performing the required manoeuvres, particularly in severe disease, and inherent measurement variability makes detection of clinically important changes difficult using these parameters. There is, therefore, a need for new biomarkers in this patient group. Neural respiratory drive (NRD) reflects the load on the respiratory system and the capacity of the respiratory muscles. Parasternal intercostal muscle electromyography (EMGpara) provides a non-invasive measure of NRD which relates to disease severity and breathlessness in obstructive lung diseases. Measurements of EMGpara in ILD could potentially quantify overall disease severity. Aim The aim of the study was to investigate the relationships between EMGpara, lung function, breathlessness, functional s...