Tests of respiratory muscle function

Respiratory muscle strength and endurance should be assessed when dyspnea, respiratory failure, or poor performance on routine pulmonary function tests are unexplained. Respiratory muscle strength can be measured non-invasively from maximal mouth pressures, but measurement of transdiaphragmatic pressure refines the assessment. The maximal voluntary ventilation test is the only simple index of ventilatory or respiratory muscle endurance. Other tests for endurance and fatigue are more difficult, but some newer techniques may be applicable to the clinical laboratory. Some patients who exhibit tachypnea, marked use of neck inspiratory muscles, and chest-abdomen asynchrony may be developing respiratory muscle fatigue.     

脊柱手术对患者呼吸功能和呼吸肌力的影响观察

目的考察脊柱手术患者术后呼吸功能和呼吸机力的变化,为患者术后治疗及护理提供数据支持。方法比较130例接受脊柱手术治疗患者术前及术后1d和2d时的肺活量、潮气量、最大呼气压、最大吸气压、呼气耐受时间和吸气耐受时间。并比较不同手术部位、手术时间患者呼吸功能和呼吸肌力变化差异。结果脊柱手术患者术后1d的呼吸功能及呼吸肌力显著降低(P0.01),术后2d呼吸功能及呼吸肌力与术后1d相比有些许回升但无统计学差异(P0.05)。胸椎手术患者术后呼吸功能及呼吸肌力下降比例显著高于颈椎和腰椎手术患者(P0.01),且颈椎手术患者高于腰椎手术患者(P0.05)。椎间盘突出患者术后呼吸功能及呼吸肌力降低水平显著低于肿瘤患者(P0.05)。结论脊柱手术患者术后呼吸功能及呼吸肌力显著降低,且胸椎手术和肿瘤手术对患者呼吸功能及呼吸肌力影响较大。     

The effect of aging on skeletal muscle capillarization in a murine model

Capillarization of skeletal muscle has been reported to be both maintained and reduced with advancing age. This conflict may represent methodological differences between biopsy studies. We have examined capillarization throughout two muscles, soleus and extensor digitorum longus (EDL), from a well-established colony of aging mice, and related this to fiber number (C/F ratio) and type. Labeling of muscle capillaries was performed with the biotinylated Griffonia (Bandeiraea) simplicifolia lectin (GSL 1) using immunochemistry. The results showed a significant increase in the C/F ratio in the aged mice when compared with the younger (6-month mice soleus = 1.296, 95% CI 1.226-1.366 vs 28-month mice soleus = 1.530, 95% CI 1.488-1.572, p <.001; 6-month mice EDL = 0.881, 95% CI 0.751-1.011 vs 28-month mice EDL = 1.124, 95% CI 1.028-1.220, p = .017). These differences could not be accounted for by changes in fiber type but may reflect loss of fibers. Alternatively, there may be increased angiogenic drive or a failure of downregulation of angiogenesis.     

The aging respiratory system

In this review article, the effects of old age on lung structure and function are discussed. Changes in lung morphology and biochemistry are correlated with changes in lung mechanics and gas exchange, as well as with the respiratory system's adaptability to the stresses of exercise and sleep. The effects of aging on the lungs' defense mechanisms are related to pulmonary diseases of the elderly.     

Effects of the menstrual cycle on respiratory muscle function

To investigate the effect of the menstrual cycle on respiratory muscle function, respiratory muscle and pulmonary functions were measured and compared in the midfollicular phase and in the midluteal phase of the menstrual cycle in 30 healthy adult women. Respiratory muscle strength was indicated by maximal static inspiratory and expiratory pressures. Inspiratory muscle endurance was determined by the product of pressure load and the sustained time, i.e., pressure-time index, while the subject breathed against an inspiratory pressure load on a modified Nickerson-Keens device. The results showed that the inspiratory muscle endurance was greater in the midluteal phase than in the follicular phase (815 +/- 43 versus 649 +/- 62 cmH2O.min, respectively), whereas the respiratory muscle strength and pulmonary function were unchanged. We conclude that inspiratory muscle endurance is affected by the menstrual cycle, i.e., higher in the midluteal phase and lower in the midfollicular phase.     

The effect of hyperinflation on respiratory muscle work in acute induced asthma

To examine the relationship between end-expiratory lung volume and respiratory muscle work during acute bronchoconstriction, we measured the work of breathing in nine asthmatic subjects, in whom bronchoconstriction was induced with histamine aerosol. When the forced expiratory volume in one second (FEV1) fell below 60% of the control value, work was measured at the spontaneously hyperinflated lung volume (VLS), at a volume equivalent to the control functional residual capacity (FRC) and at a volume 30% of vital capacity (VC) above the control FRC. Hyperinflation to VLS caused a 39% decrease in the total positive work per breath from 2.8 +/- 0.4 to 1.7 +/- 0.1 J, entirely due to a decrease in expiratory work per breath from 1.6 +/- 0.4 to 0.10 +/- 0.05 J. Inspiratory work did not change at any lung volume, because the increase in inspiratory elastic work due to hyperinflation was offset by the decrease in flow resistive work. Breathing above VLS did not alter the total positive muscle work, but did increase the negative work of the inspiratory muscles from 0.4 +/- 0.1 to 0.8 +/- 0.1 J.breath. We conclude that during induced asthma spontaneous hyperinflation minimizes the total respiratory muscle work and may constitute a mechanism for minimizing energy expenditure.     

The effect of aminophylline on respiratory and limb muscle contractility in man

The effect of oral aminophylline on respiratory muscle and quadriceps femoris strength was compared with placebo in five normal subjects. A double-blind randomized cross-over protocol, spanning 2-3 wks, was followed. Aminophylline was taken before both placebo and active drug periods to establish correct dosage, to allow tolerance to side-effects to develop, and to keep the two limbs of the study identical and double-blind. Maximal static inspiratory and expiratory mouth pressures at residual volume and total lung capacity, respectively, maximal sniff transdiaphragmatic pressure, maximal voluntary quadriceps femoris contraction force and theophylline levels were measured during placebo and active drug periods. For the group, there were no significant differences between respiratory or quadriceps muscle strength on aminophylline and on placebo although there was a tendency for greater values on aminophylline. Mean theophylline level was 14.6 mg.l-1 (range 8.4-25.0 mg.l-1). We conclude that aminophylline produces no enhancement of skeletal muscle strength, at therapeutic dosage in normal subjects.     

The biochemistry of aging muscle

Between the ages of 20 and 80, humans lose approximately 20-30% of their skeletal muscle mass. This age-related loss of muscle mass, sometimes described as 'sarcopenia of old age', is the consequence of complicated multifactorial processes and is commonly associated with osteopenia or osteoporosis. Consequences of the aging changes in muscle are declining physiological function and loss of muscle strength, typically associated with reduced physical activities. Consequently, falls and subsequent serious injuries are prevalent in the elderly. Thus, it is imperative to try and understand the processes, leading to age-related muscle loss, in order to develop means to retard this phenomenon leading to improved quality of life in the elderly. It is possible to divide the causes of muscle aging to intrinsic factors, involving changes at the molecular and cellular levels, and to extrinsic or environmental factors. The purpose of this review is to describe some of the biochemical processes and the possible mechanisms of muscle aging and to evaluate the importance of various extrinsic factors such as nutrition, exercise and limb immobilization. Changes in the aging skeletal muscle are reviewed with regard to: (a) enzyme activities, protein turnover and repair capacities (b) mitochondrial functioning and energy reserve systems (c) ion content and regulation (d) oxidative stress and free radicals (e) nutrition and caloric restriction (f) exercise and limb immobilization.     

Effects of loading and unloading the respiratory system on respiratory control and muscle function

To determine the effects of internal respiratory loading and unloading on respiratory neuromuscular function, ventilatory (Vi), occlusion pressure (P0.15), transdiaphragmatic pressure (Pdi) and diaphragmatic electromyogram (EMGdi) responses to CO2 rebreathing were assessed in 6 normal volunteers rebreathing gas mixtures denser (63% SF6, 30% O2, 7% CO2) and less dense (63% He, 30% O2, 7% CO2) than air (63% N2, 30% O2, 7% CO2). Loading with SF6 decreased the Vi response to CO2 rebreathing and increased P0.15 and Pdi for a given EMGdi, while the greater the increase in pressure response the less was the decrease in Vi. Unloading with He had the opposite effect. The pattern of breathing was altered with SF6, with Ti and Te increasing and frequency decreasing, while there was no change in timing with He. Internal loading of inspiration and expiration with SF6 elicits compensatory responses that depend on changes of respiratory timing and enhanced diaphragm efficiency. Adjustments to unloading are generally opposite to that observed with loading.     

The effect of aging on anaerobic and aerobic enzyme activities in human skeletal muscle

The effect of aging on metabolic enzyme activity remains controversial, possibly due to physical activity differences. We examined the effect of aging on the enzyme activity for anaerobic and aerobic pathways in nonweight-bearing human skeletal muscle from relatively sedentary males. The muscle obliquus internus abdominis was analyzed for anaerobic (creatine kinase, adenylate kinase, and lactate dehydrogenase) and aerobic (2-oxoglutarate dehydrogenase and carnitine palmitoyltransferase) enzyme activities in two groups: middle-aged (29-54 years) and older (61-74 years) adults. All enzyme activities were lower in older versus middle-aged adults when results were expressed as muscle wet weight (p <.05). When activity was expressed relative to the protein content, only lactate dehydrogenase remained significantly lower in older versus middle-aged adults (p <.001). In conclusion, some of the reduction in muscle performance in older adults may be due to lower activity of the anaerobic and aerobic enzymes as well as protein content, not solely due to a decrease in physical activity.     

Clinical and physiologic evaluation of respiratory muscle function

The ventilatory muscles are of primary importance in the maintenance of ventilation. This rather complex system of muscles centers around the diaphragm. As diaphragmatic function becomes compromised with the progression of different lung diseases, the participation of other muscles becomes necessary. This is clinically manifested by the recruitment of many of these muscles even during quiet breathing. The use of simple questions during a medical history, determination of the respiratory rate, assessment of the pattern of breathing, and observation of thoracoabdominal movements are helpful in the initial evaluation. Measurement of the FVC, lung volumes, and tidal breathing help direct attention to more specific investigation of the ventilatory muscles. Decreased respiratory muscle strength can be confirmed by measurement of PImax and PEmax. Decreased respiratory muscle endurance can be readily ascertained by measuring the MVV. Use of these simple techniques, available in most laboratories, is appropriate for initial evaluation and establishing a diagnosis. The additional measurements of esophageal and gastric pressures have added a new dimension to the study of the diaphragm; these techniques, however, remain a research tool.     

呼吸操在重度慢性阻塞性肺疾病患者呼吸肌力量训练中的作用研究

目的观察中医养生呼吸训练操结合氧疗方法对重度慢性阻塞性肺疾病（COPD）稳定期患者康复治疗的作用。方法重度COPD男性病人39例中20例为对照组,采用单纯鼻导管吸氧,另19例为实验组,鼻导管吸氧结合呼吸操训练,治疗前以及六个月治疗后分别检测运动能力、血气分析、肺功能和呼吸肌力指标。结果六个月治疗后,鼻导管吸氧结合呼吸操训练组的各项指标均优于对照组（P〈0．05）。结论鼻导管结合呼吸操训练可有效提高慢性阻塞性肺疾病患者的呼吸肌的强度和耐力,增加肺活量,促进有效气体交换。     

Effects of position on respiratory muscle function during CO2 rebreathing

The effects of changing from the sitting to supine position on respiratory muscle function was assessed during CO2 rebreathing. Gastric (Pg), pleural (Ppl) and transdiaphragmatic (Pdi) pressures and thoracoabdominal motion were monitored. Diaphragmatic EMG was measured by a bipolar esophageal electrode and quantitated as a moving time average (EMGdi). From sitting to supine, in only 2 of 7 subjects (group A) the diaphragm gained a mechanical advantage as evident by an increased slope of the Pdi versus EMGdi relationship not present in the other 5 subjects (group B). At high levels of ventilation while sitting, only group B increased expiratory abdominal muscle activity leading to a more favorable diaphragm length and a passive descent of the abdomen-diaphragm on inspiration. In the supine position functional residual capacity progressively increased in all subjects and the above abdominal pattern was not seen. We conclude that during upright CO2 rebreathing the recruitment of the expiratory abdominal muscles assists diaphragmatic function by placing the diaphragm in an advantageous pressure generating configuration.