S81 Use of the diaphragm electromyogram to investigate the effect of healthy ageing on neural respiratory drive. (12th November 2019)

• Record Type: Journal Article
• Authors: Wong, V; Shah, R; Zhang, W; Mohindra, A; Fletcher, HV; Rafferty, GF; Moxham, J; Harridge, SDR; Lazarus, NR; Jolley, CJ
• Is Part Of: Thorax. Volume 74(2019)Supplement 2
• Page Start: A53
• Page End: A53
• Publication Date: 2019-11-12
• Subjects: Chest -- Diseases -- Periodicals; Thorax; Chest -- Diseases; Periodicals; Periodicals; 617.54
• DOI: 10.1136/thorax-2019-BTSabstracts2019.87
• Languages: English
• ISSNs: 0040-6376

Abstract

Abstract : Introduction and objectives: Ageing is typically associated with progressive deleterious changes in respiratory mechanics which increase the work of breathing and neural respiratory drive (NRD). The relationship between age-related changes in lung function and NRD in healthy ageing remains incompletely understood, in part due to a failure of previous research to control for negative effects of physical inactivity. This study aimed to compare neural respiratory drive (NRD) between highly active older adults (HAOA) and recreationally active younger adults (YA). We hypothesized that NRD, quantified as diaphragm electromyogram activity (EMGdi) as a percentage of volitional maximum (EMGdi%max), would be higher in HAOA than in YA and that EMGdi%max would be associated with a decline in lung function and respiratory muscle strength. Methods: 23 YA (median (IQR) age 24 (22 to 29) years) and 20 HAOA (median (IQR) age 60 (52 to 66.50), all male were studied. Participants were instrumented with a multipair oesophageal recording electrode for the measurement of EMGdi, and a dual oesophageal/gastric pressure transducer for the measurement of transdiaphragmatic pressure (Pdi = Poes – Pgas). Mean root mean square (RMS) EMGdi per breath was calculated over a 3-minute period of resting breathing, and normalised to peak RMS EMGdi recorded during maximal inspiratory manoeuvres (EMGdi%max). Sniff nasal inspiratory pressure (Sniff Pnasal), sniff oesophageal pressure, sniff transdiaphragmatic pressure and twitch transdiaphragmatic pressure following bilateral anterolateral magnetic phrenic nerve stimulation (TwPdi) were also recorded and compared between YA and HAOA groups. Relationships between recorded variables were assessed by correlation analysis. Results: Resting EMGdi%max was significantly higher in HAOA compared to YA (median (IQR) EMGdi%max HAOA 12.5 (6.0 to 15.8)%max vs YA 5.9 (5.1 to 8.7)%max, p=0.0073 (table 1). EMGdi%max correlated significantly with age (r=0.4309, p=0.0039), residual volume (r=0.4677, p=0.0035), RV%TLC (r=0.4518, p=0.0050), and bilateral TwPdi (r=-0.4905, p=0.0028). Conclusions: These data collected in a highly-active group of older individuals confirm that healthy ageing is associated with increased NRD. Increases in NRD were associated with age-related increases in gas trapping and reduced diaphragm contractility.