To breathe or not to breathe: the respiratory muscles and COPD

Pre-operative respiratory optimisation: an expert review

Postoperative pulmonary complications are common and cause increased mortality and hospital stay. Smoking and respiratory diseases including asthma, chronic obstructive pulmonary disease and obstructive sleep apnoea are associated with developing postoperative pulmonary complications. Independent risk factors for such complications also include low pre-operative oxygen saturation, or a recent respiratory infection. Postponing surgery in patients who have respiratory infections or inadequately treated respiratory disease, until these can be fully treated, should, therefore, reduce postoperative pulmonary complications. There is evidence from several studies that pre-operative smoking cessation reduces such complications, with no agreed duration at which the benefits become significant; the longer the abstinence, the greater the benefit. Intensive smoking cessation programmes are more effective, and there are long-term benefits, as many patients become permanent non-smokers following their surgery. Supervised exercise programmes normally last 6-8 weeks, and although they reduce overall complications, the evidence of benefit for postoperative pulmonary complications is mixed. High-intensity interval training can improve fitness in just 2 weeks, and so may be more useful for surgical patients. Specific respiratory pre-operative interventions, such as deep breathing exercises and incentive spirometry, can help when used as components of a package of respiratory care. Pre-operative inspiratory muscle training programmes that involve inspiration against a predetermined respiratory load may also reduce some postoperative pulmonary complications. Pre-operative exercise programmes are recommended for patients having major surgery, or in those where pre-operative testing has shown low levels of cardiorespiratory fitness; interval training or respiratory interventions are more feasible as these reduce complications after a shorter pre-operative intervention.

Size and Proportions of Slow-Twitch and Fast-Twitch Muscle Fibers in Human Costal Diaphragm

Smaller diaphragmatic motor unit potentials (MUPs) compared to MUPs of limb muscles lead to the hypothesis that diaphragmatic muscle fibers, being the generators of MUPs, might be also smaller. We compared autopsy samples of costal diaphragm and vastus lateralis of healthy men with respect to fibers' size and expression of slow myosin heavy chain isoform (MyHC-1) and fast 2A isoform (MyHC-2A). Diaphragmatic fibers were smaller than fibers in vastus lateralis with regard to the mean minimal fiber diameter of slow-twitch (46.8 versus 72.2 μm, p < 0.001), fast-twitch (45.1 versus 62.4 μm, p < 0.001), and hybrid fibers (47.3 versus 65.0 μm, p < 0.01) as well as to the mean fiber cross-sectional areas of slow-twitch (2376.0 versus 5455.9 μm², p < 0.001), fast-twitch (2258.7 versus 4189.7 μm², p < 0.001), and hybrid fibers (2404.4 versus 4776.3 μm², p < 0.01). The numerical proportion of slow-twitch fibers was higher (50.2 versus 36.3%, p < 0.01) in costal diaphragm and the numerical proportion of fast-twitch fibers (47.2 versus 58.7%, p < 0.01) was lower. The numerical proportion of hybrid fibers did not differ. Muscle fibers of costal diaphragm have specific characteristics which support increased resistance of diaphragm to fatigue.

An internet-based system for home monitoring of respiratory muscle disorders

Home telemonitoring is of great interest in respiratory medicine where large numbers of people have long term conditions. We developed a telemedicine instrument for home monitoring of patients with disturbed respiratory muscles. The instrument measures the maximum inspiratory pressure (Pimax), the inspiratory time constant (τ(i)) and connects to the Internet through TCP/IP protocol. The instrument was evaluated by means of a comparative analysis in 18 normal individuals and 15 COPD patients. In close agreement with the pathophysiology, a reduction in Pimax (p < 0.0001) and an increase in τ(i) (p < 0.001) was observed in COPD patients. We concluded that the developed system could be a useful tool for the evaluation of inspiratory muscle and for the implementation of telemedicine services, contributing to reduce the costs of the assistance offered to patients with respiratory diseases.