Author(s): HALL, L., SHARPE, G., WILLIAMS, N., JOHNSON, M., Institution: NOTTINGHAM TRENT UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 2109

INTRODUCTION:
Biological sex has been shown to influence perceptions of ‘dyspnoea’ in individuals with asthma and COPD, and in healthy individuals performing submaximal exercise [1]. However, whether biological sex affects air hunger (AH), which is the most aversive form of dyspnoea, remains unknown and was therefore the focus of this study.
METHODS:
40 healthy, non-smoking adults (20 female) aged 18-45 years visited the laboratory on two occasions separated by ≥24h. Visit 1 comprised baseline measures. Visit 2 comprised a CO2 rebreathing task to induce AH, which included: (1) a 6-min room air breathing phase, and (2) a CO2 rebreathing phase, whereby a hypercapnic-hyperoxic gas mixture (5% CO2, 95% O2) was breathed from two 6 L anaesthesia bags. Participants wore a nose clip and breathed through a flanged mouthpiece and provided subjective ratings of AH intensity (AH-I) and unpleasantness (AH-U) every 30-s using a modified Borg Scale [0 (‘none’) to 10 (‘maximal’)]. The task was concluded if participants stopped of their own volition, rated maximum perception (i.e., 10), and/or reached an end-tidal carbon dioxide partial pressure (PETCO2) of 70 mmHg. Subsequently, the Multidimensional Dyspnoea Profile (MDP) was administered with a focus on the ’final moments of the task’.
RESULTS:
Area under the curve (determined using the trapezoid rule) for AH intensity (AUC-I) and unpleasantness (AUC-U) were higher in females than males (AUC-I: 1422 ± 752 vs 1006 ± 349 AU P = 0.017; AUC-U: 1310 ± 714 vs 836 ± 374 AU, P = 0.007). On the MDP females felt more anxious (5 ± 3 vs 3 ± 3, P = 0.049) and afraid (4 ± 3 vs 2 ± 3, P = 0.043) than males. Furthermore, females perceived a higher magnitude of ‘tight/constricted lungs’ (6 ± 3 vs 2 ± 2, P < 0.001) and ‘mental effort/concentration’ (7 ± 3 vs 4 ± 3, P < 0.001) than males. PETCO2 slope was higher in males than females (4.75 ± 0.75 vs 3.88 ± 0.65 mmHg/min, P < 0.001). Baseline values for PETCO2, minute ventilation (VE) and tidal volume (VT) were higher in males compared to females (PETCO2: 38.9 ± 2.4 vs 37.1 ± 2.0 mmHg, P = 0.006; VE: 16 ± 2 vs 14 ± 3 L/min, P = 0.021; VT: 1215 ± 306 vs 906 ± 138 mL, P < 0.001). End-task values for PETCO2, VE and VT were higher in males compared to females (PETCO2: 68.3 ± 2.7 vs 61.8 ± 5.0 mmHg, P < 0.001; VE: 79 ± 22 vs 58 ± 23 L/min, P = 0.002; VT: 2442 ± 624 vs 1801 ± 545 mL, P < 0.001).
CONCLUSION:
Compared to males, females report greater subjective perceptions of AH-I and AH-U during a CO2 rebreathing task, along with a greater negative emotional response. These findings therefore suggest that sex differences in the perceptions of dyspnoea extend beyond conditions of exercise (exertional) and respiratory disease.

References
1. Archiza, B., Leahy, M. G., Kipp, S., & Sheel, A. W. An integrative approach to the pulmonary physiology of exercise: when does biological sex matter? European Journal of Applied Physiology, 2021. 121(9): p.2377-2391.