Asthma is associated with reductions in the airway lumen and breathing difficulties that are attributed to airway smooth muscles (ASM) hyperconstriction. Pharmaceutical bronchodilators such as salbutamol and isoproterenol are normally used to alleviate this constriction. Deep inspirations and tidal oscillations (TO) have also been reported to relax ASM in healthy airways with less response in asthmatics. Little information is available on the effect of other forms of oscillation on asthmatic airways. This study investigates the effect of length oscillations (LO), with amplitude 1 and 1.5% in the frequency range 5-20 Hz superimposed on breathing equivalent LO, on contracted ASM dissected from sensitized mice. These mice are believed to show some symptoms such as airway hyperreactivity similar to those associated with asthma in humans. In the frequency range used in this work, this study shows an increase in ASM relaxation of an average of 10% for 1.5% amplitude when compared with TO, ISO, or the combination of both. No similar finding is observed with 1% amplitude. This suggests that superimposed length oscillation acting over the interaction of myosin and actin during contraction may lead to temporal rearrangement and disturbance of the cross-bridge process in asthmatic airways.
An asthmatic attack is instigated by hyperconstriction of airway smooth muscle (ASM). This can be relieved with bronchodilator medication such as Isoproterenol (ISO). This paper hypothesizes that mechanical oscillations may improve drugs therapy when combined with ISO. Preliminary results indicate that combining ISO with breathing equivalent mechanical oscillations trends to increase the relaxation response as compared with the use of ISO alone. The effect of superposed oscillations in the range of 10–30 Hz of frequency applied over breathing equivalent mechanical oscillations was also assessed in the study.
In asthma treatment β-agonists such as isoproterenol are used for their ability to relax airway smooth muscle (ASM) through stimulation of cAMP production. In vitro experiments conducted on ASM tissues suggest that length oscillations applied to contracted muscle result in a reduction in the contractile ability of the tissue. Conducting experiments on tissues from two different species leads to a fact that length oscillation enhances ASM relaxation induced by β-agonists agent independent of the species.
The main driving mechanism during an asthma attack is the hyperconstriction of airway smooth muscle (ASM), which reduces the airway lumen and makes normal breathing difficult. The contraction can be relieved by using bronchodilator drugs such as Isoproterenol (ISO). This paper hypothesizes that superimposed length oscillations (SILO) may improve drug therapy when combined with ISO or used alone in asthmatic subjects. The aim of this study is to assess SILO patterns directly onto the airways of healthy and asthmatic subjects (mice), while they are under anaesthesia breathing spontaneously and pre-constricted (mimicking and asthmatic attack), and compared the response with the relaxation observed just with ISO.
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