Effect of isolated unilateral diaphragmatic paralysis on ventilation and exercise performance in rats

Aerobic exercise ameliorates particulate matter-induced lung injury in aging rats

Particulate matter 2.5 (PM_2.5) is an inflammatory-inducing factor that is considered to be related to many adverse respiratory problems, especially in the elderly. This study aimed to examine whether pre-exercise training could prevent pulmonary injury induced by urban PM_2.5 in aging rats and investigate its relationship with inflammatory pathways. Male Wistar rats (aged 16 months) were randomly divided into four groups: sedentary, exercise, sedentary + PM_2.5 exposure, and exercise + PM_2.5 exposure. All rats in exercise-related groups were treadmill-trained for 8 weeks (65%-75% VO_2max for 30 min every other day). Sedentary groups' rats lived freely in cages without exercise intervention. Rats in the PM-related groups were exposed to ambient PM_2.5 (4 h day^-1) for 2 weeks after an 8-week exercise intervention or sedentary treatment. Finally, all rats' pulmonary function, lung morphology, degree of inflammation, and relevant protein and mRNA transcript expression levels were examined. The results indicated that PM_2.5 exposure induced lung injury in the sedentary + PM_2.5 exposure group, as evidenced by the deterioration of pulmonary function, histopathological characteristics, and inflammatory changes. Aerobic exercise alleviated PM_2.5-induced airway obstruction, deterioration of pulmonary function, bronchial mucosal exfoliation, and inflammatory responses in aging rats. These effects in exercise groups were associated with the increased expression of intracellular 70 kDa heat shock protein (iHSP70) and the suppression of nuclear transcription factor-κB (NF-κB) activation, as confirmed by increased expression of inhibitor of NF-κB (IκBα) and a reduction in phospho-IKBα (p-IκBα), which is regulated by inhibiting kappa B kinase beta (IKKβ). Taken together, aerobic pre-exercise had protective effects on lung injury and reduced vulnerability to inflammation induced by PM_2.5 exposure, possibly through the toll-like receptor 4 (TLR4)/NF-κB signaling pathways mediated by the extracellular-to-intracellular HSP70 ratio. Pre-exercise training may be an effective way to protect against PM_2.5-induced lung toxicity in aging individuals.

Unilateral diaphragmatic paralysis: inspiratory muscles, breathlessness and exercise capacity

Background

Patients with unilateral diaphragmatic paralysis (UDP) may present with dyspnoea without specific cause and limited ability to exercise. We aimed to investigate the diaphragm contraction mechanisms and nondiaphragmatic inspiratory muscle activation during exercise in patients with UDP, compared with healthy individuals.

Methods

Pulmonary function, as well as volitional and nonvolitional inspiratory muscle strength were evaluated in 35 patients and in 20 healthy subjects. Respiratory pressures and electromyography of scalene and sternocleidomastoid muscles were continuously recorded during incremental maximal cardiopulmonary exercise testing until symptom limitation. Dyspnoea was assessed at rest, every 2 min during exercise and at the end of exercise with a modified Borg scale.

Main results

Inspiratory muscle strength measurements were significantly lower for patients in comparison to controls (all p<0.05). Patients achieved lower peak of exercise (lower oxygen consumption) compared to controls, with both gastric (−9.8±4.6 cmH₂O versus 8.9±6.0 cmH₂O) and transdiaphragmatic (6.5±5.5 cmH₂O versus 26.9±10.9 cmH₂O) pressures significantly lower, along with larger activation of both scalene (40±22% EMGmax versus 18±14% EMGmax) and sternocleidomastoid (34±22% EMGmax versus 14±8% EMGmax). In addition, the paralysis group presented significant differences in breathing pattern during exercise (lower tidal volume and higher respiratory rate) with more dyspnoea symptoms compared to the control group.

Conclusion

The paralysis group presented with exercise limitation accompanied by impairment in transdiaphragmatic pressure generation and larger accessory inspiratory muscles activation compared to controls, thereby contributing to a neuromechanical dissociation and increased dyspnoea perception.

The exercise capacity limitation in patients with unilateral diaphragmatic paralysis is characterised by an inefficient hemidiaphragm contraction. Consequently, there is a neuromechanical dissociation with an overload of inspiratory accessory muscles and higher breathlessness.https://bit.ly/2XxAR4K

Effect of aerobic exercise and different levels of fine particulate matter (PM2.5) on pulmonary response in Wistar rats

BACKGROUND

Exposure of particulate matter of <2.5 μm (PM_2.5) has been associated with adverse respiratory and the risk of inflammation. While regular physical activity (PA) reduces the risk of many adverse health effects. This study aimed to examine the protection of exercise on adverse pulmonary health induced by PM_2.5 exposures in rats.

METHODS

80 Wistar rats were randomly divided into 8 groups: Sedentary (S), Exercise (E), Sedentary+ Low concentration PM_2.5 exposures (S + LPM), Exercise+Low concentration PM2.5 exposures (E + LPM), Sedentary+Medium concentration PM_2.5 exposures (S + MPM), Exercise+ Medium concentration PM_2.5 exposures (E + MPM), Sedentary+High concentration PM_2.5 exposures (S + HPM), and Exercise+ High concentration PM_2.5 exposures (E + HPM). The rats in all E-related groups went through 8-week aerobic interval treadmill training (5 days/week, 1 h/day). The PM-related groups of rats were exposed to different concentration PM_2.5 exposure in Beijing. After one bout of PM exposure, the pulmonary function, structure of lung tissues and several pulmonary biomarkers were observed.

RESULTS

1) Compared with S group, following changes occurred in various S + PM_2.5 exposure groups: lung tissues were seriously damaged, local bleeding, pus exudation, and inflammatory cell infiltration, as well as the decline of the SOD, CAT and GSH while the incline of Penh, Ti, Te, MDA, TNF-α and IL-1β were observed. 2) Compared with the corresponding different concentration of S + PM_2.5 exposure groups, Penh, Ti, Te, MDA, TNF-α and IL-1β were decreased and CAT and GSH were increased in related E + PM groups respectively.

CONCLUSION

In summary, the results suggest that acute PM_2.5 with different concentrations can cause different degrees of adverse effects on lung, especially in medium and high concentrations. The aerobic interval training improved the pulmonary function and impeded the lesion progression, which is due to effective in impeding the oxidative stress and inflammation.

Exercise testing in patients with diaphragm paresis

PURPOSE

Diaphragm paresis (DP) is characterized by abnormalities of respiratory muscle function. However, the impact of DP on exercise capacity is not well known. This study was performed to assess exercise tolerance in patients with DP and to determine whether inspiratory muscle function was related to exercise capacity, ventilatory pattern and cardiovascular function during exercise.

METHODS

This retrospective study included patients with DP who underwent both diaphragmatic force measurements, and cardiopulmonary exercise testing (CPET).

RESULTS

Fourteen patients were included. Dyspnea was the main symptom limiting exertion (86%). Exercise capacity was slightly reduced (median VO2peak: 80% [74.5%-90.5%]), mostly due to ventilatory limitation. Diaphragm and overall inspiratory muscle function were correlated with exercise ventilation. Moreover, overall inspiratory muscle function was related with oxygen consumption (r=0.61) and maximal workload (r=0.68).

CONCLUSIONS

DP decreases aerobic capacity due to ventilatory limitation. Diaphragm function is correlated with exercise ventilation whereas overall inspiratory muscle function is correlated with both exercise capacity and ventilation suggesting the importance of the accessory inspiratory muscles during exercise for patients with DP. Further larger prospective studies are needed to confirm these results.