家庭无创正压机械通气联合康复锻炼对慢性阻塞性肺疾病患者呼吸肌肌力的影响

目的评估家庭无创正压机械通气联合康复锻炼对稳定期重度慢性阻塞性肺疾病（COPD）患者呼吸肌肌力的影响。方法将56例经住院治疗处于稳定期的重度COPD患者分为无创呼吸机＋呼吸操组（治疗组,n=26）和无创呼吸机组（对照组,n=30）。分别观察治疗前、治疗后2年两组患者的最大吸气压（MIP）、跨膈压（Pdi）、最大跨膈压（Pdimax）及Pdi/Pdimax、CO_2分压（PaCO_2）、肺功能、6min行走距离（6MWD）、病死率及再住院率等指标。结果两组年龄、性别、COPD病程、体质量指数、PaCO_2、PaO_2、MIP、Pdi、Pdimax及Pdi/Pdimax、第一秒用力呼气容积实测值与预计值的比值（FEV_1%）、第一秒用力呼气容积占用力肺活量比值（FEV_1/FVC%）、6MWD和每年住院次数均具有可比性（均P〉0.05）。2的年后治疗组MIP,Pdi,Pdimax及Pdi/Pdimax,6MWD,每年住院次数分别为（76±6）cmH_2O,（48±5）cmH_2O,（126±11）cmH_2O,（0.38±0.01）,（263±33）m和（2.1±0.9）次/年,与对照组[（72±5）cmH_2O,（45±4）cmH_2O,（116±8）cmH_2O,（0.39±0.02）,（244±26）m,（2.6±0.9）次/年]比较均具有统计学意义（均P〈0.05）。治疗组死亡1例（1/26）,对照组2例（2/30）,两组比较差异无统计学意义（χ~2=0.02,P〉0.05）。结论长期家庭无创正压机械通气联合呼吸操康复锻炼治疗可以有效提高稳定期重度COPD患者呼吸肌肌力及呼吸肌耐力,改善运动功能,从而达到更好的长期治疗效果。     

俯卧位呼吸时悬空腹部对呼吸动力学的影响

目的 :探讨稳定期慢性阻塞性肺疾病(COPD)患者和健康志愿者在俯卧位状态下是否悬空腹部对呼吸和循环动力学的影响。方法:12例稳定期COPD患者和9名健康志愿者采取仰卧位、俯卧位悬空腹部、俯卧位3种不同体位,通过NICO和BioZ无创心肺功能监测仪连续测定患者的呼吸和循环动力学指标,通过呼吸功能检测电极测定膈肌肌电、跨膈压(Pdi)等指标,每个体位均观察10 min。结果:1呼吸动力学:健康志愿者俯卧位的Pdi与俯卧位悬空腹部和仰卧位比较显著升高[(13.5±1.6)比(11.5±2.2)、(10.1±1.7)cmH_2O(1 cmH_2O=0.098 kPa),P<0.05],稳定期COPD患者俯卧位的Pdi与俯卧位悬空腹部和仰卧位比较明显升高[(22.6±2.5)比(15.6±2.6)、(18.2±3.2)cmH_2O,均P     

控制性机械通气对大鼠膈肌功能的影响

目的 探讨控制性机械通气(CMV)对大鼠膈肌功能的影响,了解不适当控制性机械通气与膈肌功能不全和脱机困难的关系.方法 将24只雄性SD大鼠按随机数字表法分为3组:正常对照组、18 h CMV组和24 h CMV组.后两组分别给予18 h和24 h CMV,并测定膈肌跨膈压(Pdi)、最大跨膈压(Pdimax)、膈肌肌电图(EMGdi)等指标和膈肌肌球蛋白重链(MHC)表型的改变.两样本组间均数比较用t检验,多组间均数差异性比较采用单因素方差分析.结果 与对照组比较,18、24 Hcmv组Pdimax分别为[(8.98±0.55、6.12±0.53、14.92±0.16)cm H2O,1 cm H2O=0.098 kPa],实验组均低于对照组,差异有统计学意义(F=82.35,P<0.01);实验组EMGdi的中心频率和高低频比值均低于对照组;在最大刺激频率(100 Hz)下18、24 h CMV组的膈肌肌张力[(84.11±0.43、52.65±0.64)N]较对照组[(98.13±0.50)N]低,差异有统计学意义(F=15.02,P<0.01);同时MHC2A比例下降;24 h CMV组大鼠膈肌肌纤维的电镜下病理改变为:膈肌出现肌原纤维排列疏松、脂肪滴和空泡增多,个别出现线粒体肿胀、空化,嵴减少.结论 短期CMV即可导致膈肌功能失调和形态改变;机械通气,特别是CMV诱导的膈肌功能障碍可能是引起临床上一些患者脱机困难的重要原因之一.     

口腔压或气道内压与食管内压和跨膈压的关系

目的探讨口腔压(Pmo)或气道内压(Ptr)与食管内压(Pes)和跨膈压(Pd i)的关系。方法对17例因腹部手术需要全身麻醉(简称全麻)的患者,观察全麻前的最大吸气压(M IP)、最大食管内压(Pesm ax)、最大跨膈压(Pd im ax)、颤搐性口腔压(TwPmo)、颤搐性食管内压(TwPes)和颤搐性跨膈压(TwPd i)以及全麻期间的颤搐性气道内压(TwPtrnar)、颤搐性食管内压(TwPesnar)和颤搐性跨膈压(TwPd inar),以了解它们的变异性和相互关系。结果(1)M IP与Pd im ax、TwPmo与TwPd i、TwPtrnar与TwPd inar、M IP与Pesm ax、TwPmo与TwPes和TwPtrnar与TwPesnar的线性相关系数(r)分别为0.976±0.030、0.816±0.155、0.923±0.446、0.981±0.185、0.829±0.168和0.955±0.292。(2)M IP、Pesm ax、Pd im ax、TwPmo、TwPes和TwPd i的变异系数(CV)分别为(14.2±4.7)%、(15.2±4.3)%、(15.5±4.1)%、(30.4±15.9)%、(10.8±5.1)%和(9.9±4.0)%,其中TwPmo最高(与其他观测指标比较P均<0.05),TwPes和TwPd i最低(与其他观测指标比较P均<0.05),而M IP、Pesm ax和Pd im ax间比较差异均无统计学意义(P均>0.05)。(3)TwPtrnar与TwPd inar、TwPesnar间动态变化的r值分别为0.839、0.894(P均=0.000)。结论M IP和TwPmo均可能低估膈肌功能,需重复测定,取其最高值,TwPtrnar能客观评价膈肌功能的动态变化。     

跨膈压测量方法及临床意义

本文介绍了测量人体跨膈压所需的设备、具体操作方法,以及国外部分作者的测量结果,并结合临床讨论了跨膈压测量的实用价值和应用前景.此法可作为评定膈肌功能的一项指标。     

慢性阻塞性肺疾病模型大鼠膈肌功能的实验研究

目的 以慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)模型大鼠为研究对象,探讨膈肌功能及短期控制性机械通气对膈肌功能的影响.方法 应用气管内滴注脂多糖联合被动吸烟的方法 复制大鼠COPD模型,比较正常大鼠与COPD大鼠跨膈压及膈肌肌电图频谱变化;对COPD模型组大鼠行短期控制机械通气,观察其膈肌功能的变化.结果 COPD模型组大鼠肺功能与正常对照组比较FEV0.3/FVC[(88.05±5.87)%vs(69.41±11.50)%]显著下降(P<0.05).COPD模型组大鼠跨膈压与正常对照组相比[(4.28±1.03)cm H2Ovs(5.36±0.94)cm H20]显著下降(P<0.05),说明COPD模型组大鼠呼吸肌力较正常对照组下降.COPD模型组大鼠较正常对照组大鼠的膈肌肌电高低频比值(%)(4.99±2.36 vs 3.12±1.10)下降显著(P<0.05),低频部分显著增加(P<0.05).COPD模型组大鼠机械通气(6 h)前后跨膈压及肌电图频谱分析结果 差异无统计学意义.结论 COPD模型组大鼠跨膈压较对照组减小,膈肌肌电图频谱分析高低频比值下降.说明其膈肌功能下降.短期(6 h)控制机械通气对COPD大鼠膈肌功能无显著影响.     

同步悬空俯卧位对稳定期慢性阻塞性肺疾病患者膈肌功能影响的探讨

目的 探讨同步悬空俯卧位对稳定期慢性阻塞性肺疾病(chronic obstractive pulmonary disease,COPD)患者膈肌功能情况的影响.方法 5例稳定期COPD患者,在"人工呼吸床"上随机四种不同体位:①仰卧位;②悬空俯卧位;③托平俯卧位;④同步悬空俯卧位.每个体位观察10 min,通过呼吸功能检测电极监测膈肌肌电、食道压和胃压等指标.结果 四种体位对心率、氧饱和度、呼气末二氧化碳无明显的影响(P>0.05),其中同步悬空俯卧的呼吸频率在四种体位中是最慢的(16±2.7)次/min,由慢至快呈现:同步悬空俯卧→仰卧→托平俯卧→悬空俯卧的趋势;同步悬空俯卧位的潮气量在四种体位中是最大的(600.7±122.5)ml;同步悬空俯卧位的跨膈压是(14.6±2.6)cm H2O,是四种体位中最小的,与托平俯卧位(22.6±2.5)cm H2O比较差异有统计学意义(P<0.05),同步悬空俯卧位的膈肌肌电是(76.4±38.9)μV,是四种体位中最高的,但与其他体位比较差异无统计学意义(P>0.05).结论 "人工呼吸床"上同步悬空俯卧位与其他两种俯卧呼吸体位一样,对COPD患者经短时间观察是安全稳定的;同步悬空俯卧位以最低的跨膈压,不但降低患者的呼吸频率,增加潮气量,在不增加呼吸做功的情况下,改善膈肌的运动能力.     

膈肌超声评估与跨膈压对慢性阻塞性肺疾病急性加重期患者接受无创通气结局的预测价值研究

目的 探讨慢性阻塞性肺疾病急性加重期(AECOPD)进行无创通气的患者采用超声评估膈肌功能障碍的临床应用效果,分析膈肌超声评估(DUS)和跨膈压(Pdi)的相关性及其对预后的评估价值。方法 选择 2018 年 2 月至2019年9月,锦州医科大学附属第三医院73例AECOPD无创机械通气治疗患者,根据无创通气上机结局分为上机成功组(54例)和上机失败组(19例),比较两组患者接受无创通气后2 h、24 h、48 h膈肌增厚分数(ΔTdi)、Pdi_max与血清白蛋白(Alb)的变化趋势,分析 ΔTdi 与 Pdi_max的相关性,并比较 2 h 后 ΔTdi、Pdi_max与 pH<7.25 对无创通气结局的预测价值。结果 成功组ΔTdi、Pdi_max24 h、48 h与2 h相比,显著上升,差异均有统计学意义(均P<0.05),失败组ΔTdi、Pdi_max呈现显著下降趋势(均P<0.05);上机2 h、24 h和48 h两组Alb比较,差异无统计学意义(均P>...     

左心声学造影对二尖瓣狭窄跨瓣压的测量价值

目的　经静脉注射东冠注射液声学造影剂进行左心室声学造影 ,探讨其对二尖瓣狭窄跨瓣压的测量价值。方法　对 10例二尖瓣狭窄患者注射声学造影剂 0 .0 8ml/kg ,测量造影前后二尖瓣狭窄跨瓣压差并与心导管资料对比。结果　造影前后跨瓣压分别为 ( 13 .7± 4.6)mmHg及( 15 .5± 4.4)mmHg ,两者比较差异有显著性 (P <0 .0 5 ) ;造影后跨瓣压与心导管所测跨瓣压的相关系数为 0 .90 ,两者比较差异有非常显著性 (P <0 .0 0 1)。结论　声学造影可增加超声仪检查二尖瓣狭窄血流频谱的准确性。     

慢性阻塞性肺疾病急性发作期患者对比例辅助通气的生理反应

目的　探讨比例辅助通气 (PAV)不同辅助水平对慢性阻塞性肺疾病 (COPD)急性发作期患者生理反应的影响。方法　 9例COPD急性发作期患者接受三个不同比例辅助水平的PAV通气 ,观察患者吸气肌肉用力情况和呼吸方式的变化。结果　 (1)与自主呼吸 (SB)相比 ,PAV各辅助水平时的潮气量 (VT)、分钟通气量 (V·E)和呼吸频率 (RR)均稍增高 (P >0 0 5 )。各比例辅助水平之间的VT、V·E 和RR比较差异无显著性 (P >0 0 5 )。 (2 )与SB相比 ,各比例辅助水平时的跨膈压 (Pdi)、压力时间乘积 (PTP)和患者呼吸做功均明显减少 (P >0 0 1) ,Pdi、PTP和患者呼吸做功分别平均减少 8 36cmH2 O、11 4 9cmH2 O·s-1·L-1和 0 5 3J/L。随比例辅助水平的升高 ,Pdi、PTP和患者呼吸功无明显变化(P >0 0 5 )。 (3)PAV可减轻患者呼吸困难 (P <0 0 5 )。结论　本试验证实了无创PAV在COPD急性发作期患者中应用的可行性。患者感觉最舒适的PAV辅助比例水平是 (5 7± 11) %。根据患者感觉舒适情况而设定比例辅助水平的无创PAV可减轻患者的呼吸肌肉负担 ,最舒适水平时呼吸功减少5 7% ,Pdi减少 72 % ,PTP减少 6 5 % ;并改善患者的呼吸方式和呼吸困难     

Transdiaphragmatic pressure in young adult Singaporean subjects - normal values and a comparison between different respiratory manoeuvres

Background: Most published normal values for transdiaphragmatic pressure (Pdi) have been from Caucasian subjects and there is no universal agreement regarding the most appropriate manoeuvre for assessing Pdi. Aims: The aims of our study were to obtain normal values and to compare the different manoeuvres used to assess Pdi in normal young Singaporean adults. Methods: Twenty-four normal subjects (23 Chinese, one Indian) were studied by measuring Pdi during maximal sniffs from functional residual capacity (sniff Pdi), maximal inspiration to total lung capacity (Pdi TLC) and maximal static inspiratory efforts from residual volume (Pdi PImax). Results: Mean values±SD for sniff Pdi, Pdi TLC and Pdi PImax were 101.8±31.7, 46.8±26.4 and 83.5±35.5 cm H₂0 respectively. Sniff Pdi was significantly higher than Pdi TLC (p<0.001) and Pdi PImax (p=0.005). Pdi PImax was significantly higher than Pdi TLC (p<0.001). Males had significantly higher values for sniff Pdi (p=0.026) and Pdi PImax (p=0.022) than females. There was a significant correlation between the different methods of recording Pdi. Sniff Pdi had the highest values, least between- and within-subject variation and most consistent pattern of respiratory muscle recruitment with the lowest proportion of negative gastric pressure (Pg) values (p<0.001). Conclusions: Therefore, sniff Pdi may be better than Pdi TLC and Pdi PImax in assessing diaphragm function. Also, our subjects seemed to have lower sniff Pdi and Pdi PImax, and higher Pdi TLC compared with Caucasian subjects.     

Sniff and Muller manoeuvres to measure diaphragmatic muscle strength

We hypothesized that peak values of oesophageal (Poes) and transdiaphragmatic pressure (Pdi) swings during a maximal sniff manoeuvre and a maximal static inspiratory manoeuvre (Muller manoeuvre) are comparable or give complementary information for assessing diaphragmatic and global inspiratory muscle strength. We studied 98 patients with suspected diaphragmatic dysfunction. Poes and Pdi swings were measured during maximal sniff manoeuvres (sniff), maximal Muller manoeuvres (max), and cervical magnetic phrenic nerve stimulation (cervical Tw). Eighty eight patients were able to perform both volitional manoeuvres. Among them, mean Poes sniff was significantly higher than mean Poes max (48.7+/-28.7 cm H(2)O vs. 42.9+/-27.4 cm H(2)O, p<0.05) and mean Pdi sniff was higher than mean Pdi max (49.2+/-35.1cm H(2)O vs. 42.9+/-33.3 cm H(2)O, respectively, p=0.05). Cervical Pdi Tw correlated better with Pdi sniff (p<0.0001, r=0.62) than with Pdi max (p<0.0001, r=0.44). Poes and Pdi swings were greatest during the sniff manoeuvre in 42 patients (48%) and during the Muller manoeuvre in 29 patients (33%). Among the 17 remaining patients, nine had the greatest Poes swing during a maximal sniff manoeuvre and the greatest Pdi swing during a maximal static inspiratory manoeuvre; the opposite occurred in the other eight patients. The combination of Muller manoeuvre and sniff manoeuvre increased the diagnosis of normal diaphragmatic strength from 18 patients (20%) to 21 patients (24%), and the additional analysis of cervical Pdi Tw further increased the diagnosis of normal diaphragmatic strength to 27 patients (31%). In conclusion, though sniff manoeuvre gave significantly higher values than Muller manoeuvre, both volitional manoeuvres and cervical Pdi Tw are complementary and should be used in combination to evaluate diaphragmatic muscle strength.     

The value of sniff esophageal pressures in the assessment of global inspiratory muscle strength

Esophageal pressure generated during a maximal sniff (sniff Pes) was compared with mouth pressure generated during a maximal inspiration against a closed airway (Pimax) as a measure of global inspiratory muscle strength in 61 patients referred for investigation of respiratory muscle function. Transdiaphragmatic pressure (Pdi) was also measured during both maneuvers to compare maximal diaphragmatic strength. Sniff Pes (males, 68 +/- 27 cm H2O; normal greater than 53; females, 66 +/- 21; normal greater than 48) was greater than Pimax (males, 45 +/- 24 cm H2O; normal greater than 42; females, 42 +/- 24; normal greater than 17) in 55 of the 61 patients, both in absolute values and as a percentage of normal. In 36 patients Pimax and sniff Pes were both normal (mean +/- 2 SD), whereas in 13 patients they were both low. In 11 patients, Pimax was low, but sniff Pes was normal. One patient had a reduced sniff Pes but a Pimax at the lower limit of normal. In the 36 patients in whom both Pimax and sniff Pes were normal, Pdi was also normal or only moderately reduced, and in the 13 patients in whom both Pimax and sniff Pes were reduced, Pdi was very low. However, in the group of 11 patients with a low Pimax but a normal sniff Pes, Pdi was normal or only moderately reduced, suggesting that Pimax was falsely low, perhaps because of difficulties with the technique. Conversely, in the single patient with a low sniff Pes but a Pimax just within the normal range, Pdi was very low. We conclude that measurement of esophageal pressure during a maximal sniff is a useful test of inspiratory muscle strength and overcomes the difficulty some patients have in carrying out the Pimax maneuver.     

Respiratory response during arm elevation in isolated diaphragm weakness.

Upper extremity exercise is associated with a significant metabolic and ventilatory cost that is particularly evident in patients with severe chronic airflow obstruction. In these patients abnormal ventilatory muscle recruitment has been hypothesized to relate to impaired diaphragm function resulting from hyperinflation. Similar data have never been reported in patients with isolated diaphragm weakness but without airflow obstruction or hyperinflation, a group that would ideally define the role of diaphragm function during arm elevation (AE). We prospectively studied 15 patients with isolated diaphragm weakness of varying severity (Pdi(sniff), 31.74 +/- 3.75 cm H(2)O) as contrasted with eight normal subjects (Pdi(sniff), 111. 77 +/- 13.35 cm H(2)O) of similar age. Patients with diaphragm weakness demonstrated significant lung volume restriction with normal DL(CO)/VA. There was no difference in resting oxygen consumption (V O(2)), carbon dioxide production (V CO(2)), minute ventilation (V E), and tidal volume (VT) between the two groups; however, a borderline difference in resting breathing frequency (f(b)) (p = 0.056) was evident. Both groups demonstrated a rise in V O(2), V CO(2), and V E during 2 min of AE anteriorly. Normal subjects demonstrated a statistically significant rise in VT but a statistically insignificant rise in f(b) during AE. In contrast, patients with diaphragm weakness demonstrated a statistically significant rise in f(b) during AE but a statistically insignificant rise in VT. In patients the observed rise in VT directly correlated with baseline Pdi(sniff) (r = 0.59, p = 0.02) and Pdi(max) (r = 0.81, p = 0.002). Both groups demonstrated a rise in Pdi during AE. The rise in Pdi during AE directly correlated to Pdi(sniff) in the patients (r = 0.69, p = 0.004). Observed end-expiratory Ppl rose during arm elevation in both the patient group and in the normal control group, but no evidence of a differential response to AE was found. In those patients with greater diaphragm weakness (Pdi(sniff) < 30 cm H(2)O), abnormal respiratory muscle function (lesser rise in Pdi) and a lesser increase in VT during AE were more evident. These data highlight the importance of diaphragm function in determining the metabolic and respiratory muscle response to arm elevation.     

Respiratory pressure partitioning during quiet inspiration in unilateral and bilateral diaphragmatic weakness

To compensate for diaphragmatic weakness, intercostal/accessory muscles may be recruited in inspiration and/or abdominal muscles in expiration with relaxation during subsequent inspiration. As a consequence, for a given decrease in pleural pressure (Ppl) during quiet inspiration (qi), abdominal pressure (Pab) should either undergo a smaller increase than normal or, in severe cases, decrease. If so, the ratio of change in Pab to Ppl during qi (delta Pab/delta Ppl(qi], which is normally less than -1 when upright, should increase, approaching +1 in profound diaphragmatic weakness. To examine the relationship between degree of diaphragmatic weakness and delta Pab/delta Ppl(qi), we measured (erect and supine) anteroposterior rib cage and abdominal motion, Pab, Ppl, and transdiaphragmatic pressure (Pdi) during qi, maximal inspiration (Pdi(max)mi) and maximal inspiratory effort at FRC (Pdi(max)FRC) in 10 patients with bilateral and 8 with unilateral diaphragmatic weakness. Pdi(max)mi and Pdi(max)FRC were low in all patients. delta Pab/delta Ppl(qi) (erect) was increased in all patients (0.28 +/- 0.7; mean +/- SD) and correlated closely with both Pdi(max)mi (r = -0.89, p less than 0.001) and Pdi(max)FRC (r = -0.76, p less than 0.001). There was extensive overlap in the data between unilateral and bilateral diaphragmatic weakness. The ratio of delta Pdi during qi to Pdi(max)FRC was less than 0.31 in all patients. The results suggest that delta Pab/delta Ppl(qi) is a useful index of the degree of diaphragmatic weakness and that the functional consequences of unilateral and bilateral weakness are not rigidly separable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diaphragmatic fatigue and its role in the development of respiratory insufficiency and cor pulmonale in COPD

Diaphragmatic function test was performed at rest and during maximal incremental exercise in six male normal non-smokers (Group A), sixteen male patients with COPD (58 +/- 8 yrs), including 4 with only small airway disorder (B) 6 with mild (C) and 6 with moderate airway obstruction (D) and eight patients with cor pulmonale complicated severe airway obstruction and chronic respiratory failure (E). Maximal transdiaphragmatic pressure (Pdi max) at rest in Group A, B, C, D, E were 13.6 +/- 2.9 kPa, 10.8 +/- 3.1 kPa, 9.9 +/- 3.4 kPa, 6.8 +/- 3.3 kPa and 5.3 +/- 2.5 kPa respectively, the latter two (D and E) being significantly lower than that of the normal control (D, P less than 0.05, E, P less than 0.01). Breathing pattern of the diaphragm at rest was similar to the normal control in all groups except that half of the patients in Group E (4/8) showed diaphragmatic paradoxical motion during inspiration. Ergometer test with incremental workload was performed in all groups except for Group E. During exercise, patients with COPD revealed some extent of diaphragmatic fatigue. All in group D(6/6) and most in group C(4/6) eventually developed inspiratory paradoxical motion of diaphragm before the ventilatory reserve was exhausted.     

慢性阻塞性肺疾病患者营养状态对运动心肺功能的影响

目的：探讨营养状态对慢性阻塞性肺疾病（COPD）患运动心肺功能的影响。方法：43例COPD患分为营养不良组（15例），营养正常组（28例）和健康志愿（20名）进行负荷连续递增的运动心肺功能试验。运动行营养评价和常规肺功能检查，结果：（1）COPD营养不良组最大氧耗量（VO2max）、最大运动负荷（Wmax）、最大氧脉搏（O2pulsemax)和无氧阈（AT）低于营养正常组，两组比较差异有显性（P＜0．05）。通气氧耗（VO2／W／VE)和最大运动时的气急指数（DImax)与营养正常组比较，差异有显性（P＜0．05）。（2）COPD患理想体重百分比（IBW％）与VO2max占预计值百分比、Wmax占预计值百分比、O2pulsemax占预计值百分比，AT呈正相关（r=0.696,0.432,0.717,0.822,P均＜0．01）、与DImax,VO2/W/VE呈负相关（r=-0.450,-0.640,P均＜0．01）。结论：营养不良可以导致COPD患肌肉有氧代谢能力和运动耐力降低。     

Dyspnea and diaphragmatic fatigue in patients with chronic obstructive pulmonary disease. Responses to theophylline

This study sought answers to 2 questions: (1) Is severe dyspnea to the point of exhaustion regularly accompanied by diaphragmatic fatigue in patients with moderately severe chronic obstructive pulmonary disease (COPD)? (2) When diaphragmatic fatigue occurs in such patients, does theophylline prevent or delay its onset? Eight eucapnic patients with moderately severe COPD were subjected to 2 different stresses to the point of severe dyspnea requiring cessation of the stress. The stresses were cycle exercise and inspiratory resistive breathing, the latter requiring a tidal Pdi equal to 60% of Pdimax. Despite incapacitating dyspnea, objective evidence of diaphragmatic fatigue was not encountered during cycle exercise. During inspiratory resistive breathing, diaphragmatic fatigue was encountered in all patients as defined by consistent inability to attain a target Pdi during final moments of the resistance run. Patients were uniformly extremely dyspneic at this point. In neither stressful maneuver did oral sustained-release theophylline show a convincing or significant advantage over placebo when administered in a randomized double-blind crossover protocol. These results suggest that the diaphragmatic fatigue encountered in this sort of COPD patient may be of predominantly central rather than peripheral (myogenic) origin and that theophylline may not be effective in this type of fatigue.     

Respiratory muscle function in myasthenia gravis

Global respiratory muscle function and diaphragmatic strength were assessed and compared with quadriceps femoris muscle strength in 17 patients with generalized mild-to-moderate myasthenia gravis and breathlessness. Initial measurements, made 10 h after the last dose of oral anticholinesterase therapy, demonstrated reduced maximal static expiratory (52.4 +/- 26.8% predicted) and inspiratory (54.0 +/- 23.5% predicted) mouth pressures in 16 patients, and reduced quadriceps femoris muscle strength in all cases. Vital capacity (VC) (70.9 +/- 19.0% predicted) was abnormal in 12 patients. Transdiaphragmatic pressure recorded during maximal sniffs (sniff Pdl) was reduced in eight patients, whereas pressure recorded during bilateral phrenic nerve stimulation at 1 Hz (twitch Pdi) was reduced in only three. There was no relationship between the grade of myasthenia or the severity of dyspnea and any of the measurements of respiratory muscle strength. After the administration of edrophonium hydrochloride (Tensilon), there was a significant increase in maximal static expiratory and inspiratory mouth pressures in quadriceps muscle strength and in sniff Pdi. The small increase in VC was not significant, and twitch Pdi increased in only one patient. Phrenic nerve conduction time was normal before and after Tensilon. Two patients with severe long-standing myasthenia showed no improvement in any measurement after Tensilon. We conclude that expiratory and inspiratory muscle weakness was not uncommon in patients with myasthenia gravis. Respiratory muscle strength improved after Tensilon. Vital capacity was a less sensitive measure of respiratory muscle strength than were respiratory mouth pressures and sniff Pdi. Diaphragmatic involvement was not detected by twitch Pdi unless the weakness was severe.(ABSTRACT TRUNCATED AT 250 WORDS)