The cardiovascular implication for exercise intolerance and dyspnoea in electronic cigarettes smokers

Giles, Agata (2024) The cardiovascular implication for exercise intolerance and dyspnoea in electronic cigarettes smokers. Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

Background: Electronic cigarettes (EC) have been proposed as a safe alternative to tobacco smoking, however, several studies have shown adverse health effects of EC. The chronic implications of EC on cardiorespiratory response and exertional dyspnoea are unknown. Aim: To examine the chronic effects of EC and tobacco cigarettes (TC) on resting vascular function, inflammatory markers, cardiorespiratory responses during exercise and exertional dyspnoea. Methodology: Three groups of young adults (16 each) with normal spirometry (EC users, TC smokers, and never-smokers [NS]) consented to participate in this study following institutional ethics approval. Participants performed forced vital capacity, maximal voluntary ventilation, maximal inspiratory and expiratory pressures manoeuvres to assess lung functions. An incremental cardiopulmonary exercise test (CPET) 20W/2mins on an electronically braked cycle ergometer was performed. Oxygen consumption (V̇O2), heart rate (HR), and ventilation (V̇E) were measured continuously throughout CPET. Blood lactate, dyspnoea, and leg discomfort were recorded at the end of each exercise increment during the CPET. Flow-mediated dilation (FMD%) of the brachial artery was assessed using Doppler ultrasonography. Results: A one-way ANOVA with Tukey post hoc test was performed. EC and TC groups had a lower peak work rate (WR) compared to NS controls (183.75 ± 30.30; 185.0 ± 34.64 vs. 227.50 ± 43.74 W, respectively; p = 0.006 and p = 0.004). WR ranged from 180-340 W, 140-260 W, 140W-240W in NS, TC and EC respectively. During submaximal exercise, EC and TC groups displayed higher V̇E, higher ratings of dyspnoea and more intense leg fatigue compared to NS controls (e.g. at the highest equivalent submaximal WR of 140 W: V̇E: 62.16 ± 9.48, 64.43 ± 12.34 vs. 53.52 ± 6.88 L/min (p = 0.018; p = 0.011); dyspnoea: 5 ± 2, 6 ± 2 vs. 3 ± 2 Borg units (p =0.033; p <.001); Leg fatigue: 6 ± 2, 7 ± 2 vs. 5 ± 3 Borg units (p = 0.048; p = 0.014), respectively. The TC smokers group displayed lower ventilatory efficiency (higher V̇E/V̇CO2) and higher blood lactate compared to NS during submaximal exercise (e.g. 140 W, V̇E/V̇CO2: 31.58 ± 5.75 vs. 28.40 ± 2.33, p = 0.036; Blood lactate: 6.54 ± 2.42 vs. 4.29 ± 2.45 mmol/L, p = 0.03, respectively). At peak exercise, breathing frequency (Fb) was lower in EC compared to NS (39.94 ± 7.81 vs. 47.50 ± 9.49 breaths/min, p = 0.037). Fb ranged from (32.26-63.68 breaths/min, 33.69-60.74 breaths/min, and 32.28-61.67 breaths/min) in NS, TC and EC respectively. FMD% was significantly lower in EC and TC groups compared with NS controls (4.85 ± 2.55, 5.26 ± 3.09 vs. 8.14 ± 3.46 %; p = 0.017, p = 0.040; respectively). FMD ranged from (1.85-15.32 %, 0.76-11.01 % and 1.3-9.56 %) in NS, TC and EC respectively. Conclusion: This study reported impaired vascular and cardiorespiratory responses to exercise and exertional dyspnoea in TC and EC groups in this cohort of young adults with normal spirometry. This suggests that e-cigarettes may impose cardiovascular risks similarly to tobacco smoking.