Respiratory function during simulated wet dives

This presentation focuses on the effects of static lung loading (SLL) on diver performance. It is noted that SLL may arise from depth differences between the diver's chest and his breathing gear. Studies are reviewed in which subjects undergoing wet, simulated dives in a pressure chamber were exposed to SLL ranging from 14.7 to -14.7 mmHg (+20 to -20 cmH2O) while breathing air at depths down to 58 m (190 ft). The subjects, assuming a prone or an upright position, performed leg exercise on an underwater bicycle ergometer. Various measurements of respiratory function were made. By applying a scoring scale for dyspnea it was found that in addition to being more pronounced as exercise and depth (gas density) increased, the dyspnea was most pronounced with negative SLL. Positive SLL alleviated the dyspnea. The dyspnea also tended to be more pronounced in the prone than in the upright posture. It was speculated that this may have been partly due to more of a compression effect on the extra thoracic airways by water pressure in the former than in the latter posture. There were no marked differences in gas exchange and end-tidal gas concentrations with different static lung loads, and it was hypothesized that differences in respiratory muscular strain may have accounted for the differences in dyspnea with different SLLs. That the dyspnea was inspiratory in nature would agree with the observation that positive SLL aiding inspiration would be perceived as beneficial. A breathing apparatus design that counteracts undesirable SLL is reviewed.     

Effects of immersion and static lung loading on submerged exercise at depth

The effects of static lung loading in the range +20 cmH2O to -20 cmH2O was investigated in 3 male subjects breathing air during submerged exercise in the prone position at pressures ranging from 1.45 ATA to 6.76 ATA. Both maximal and submaximal exercise was performed and dry controls were done at 1.45 ATA. A low-resistance bag-in-a-box breathing apparatus (less than 1.25 cmH2O/liter/s at 8 g/liter density) was used. Static lung loading had little effect on maximal or submaximal VO2, VCO2, VE, heart rate, or end-tidal PCO2, while increased breathing gas density did affect these parameters to a larger extent. Imersion per se reduced the VE at a given level of VO2 and increased both the VT and VA at a given VE. Increasingly positive static lung load increased VC and ERV both during rest and exercise. Exercise-induced dyspnea was experienced and scored. At submaximal VO2 levels up to 2.5 liter/min this dyspnea did not limit exercise at any depth, but during maximal exertion at 6.76 ATA (VO2 from 3.45--3.77 liter/min), dyspnea became work limiting in several cases. Static load had a marked effect on dyspnea and a load of +10 cmH2O produced the least dyspnea, enabling all subjects to perform maximal exertions for 5 min at 6.76 ATA. The 15-s MVV was performed at all depths and static loads and neither it nor the VE/MVV ratio correlated with the degree of dyspnea.     

Characteristics of tidal expiratory flow pattern in healthy people and patient with chronic obstructive pulmonary disease

According to data reported in literature tidal breathing parameters and especially tidal expiratory flow pattern parameters can be useful in distinguishing airflow obstruction. The purpose of the present study was to investigate the parameters of the tidal breathing in healthy people and patients with chronic obstructive pulmonary disease. The study sample included 158 patients with COPD in clinically stable condition and different degree of functional disturbances (FEV1% pred. = 42% +/- 15%; ATS dyspnea scale = 2.5 +/- 0.9; mean +/- SD). The control group of healthy subjects consisted of 43 men and 37 women. The obtained results show that TPTEF/TE (the time necessary to reach the peak expiratory flow in tidal breathing over the total expiratory time) and VPTEF/VE (the volume necessary to reach the peak expiratory flow in tidal breathing over the total expiratory volume) are an independent aspect of tidal breathing. In healthy people these parameters show weak negative correlation with age and high variability. In COPD they are statistically significantly lower than those of healthy people but, since they are highly variable, they cannot be used for an individual assessment. The increase of the mean inspiratory flow (TV/Tin) and the shortening of VPTEF/VE, TPTEF/TE and Tin/Ttot, are indicative of the lung mechanics changes which have a bearing on dyspnea, too. According to factor analysis the parameters of tidal breathing are four separate dimensions: 1. Breathing frequency and respiratory times; 2. Relationship between the respiratory times; 3. Minute ventilation, mean expiratory flow, mean inspiratory flow and tidal volume; 4. Parameters of the expiratory flow VPTEF/VE and TPTEF/TE. The parameters of forced expiration and those of tidal breathing are separate dimensions of the functional profile of patients with COPD.     

超重/肥胖对反复喘息婴幼儿潮气肺功能的影响

目的 分析超重/肥胖对反复喘息婴幼儿潮气肺功能的影响,为哮喘的预防和管理奠定基础。方法 选择在广东省妇幼保健院儿童呼吸科就诊的100例0～3岁反复喘息的急性发作期患儿为研究对象,按体重指数(BMI)分为喘息非超重组70例、喘息超重/肥胖组30例;选择80例0～3岁无呼吸系统疾病婴幼儿为对照组,其中非超重组50例,超重/肥胖组30例。测定各组受试患儿潮气呼吸流量-容积曲线(TBFV),记录各参数并进行比较。结果 喘息非超重组与对照非超重组比较,达峰时间比(TPTEF/TE)、达峰容积比(VPTEF/VE)、吸呼比(TI∶TE)、呼出75%潮气量时的呼气流速/呼气峰流速(25/PF)均明显下降 (t＝8.518、7.767、3.142、7.860,P＜0.05);呼气峰流速(PTEF)、呼出25%潮气量时的呼气流量(TEF75)显著增加(t=6.728、8.540,P＜0.05)。分别在对照组、喘息组中,与非超重儿童肺功能参数相比,超重/肥胖儿童仅潮气量(VT/kg)显著下降(t=2.872、3.048,P＜0.05)。结论 超重/肥胖影响婴幼儿肺功能潮气量(VT/kg),但不影响气道阻塞的指标。     

Effects of breathing-gas pressure on pulmonary function and work capacity during immersion

Upright immersion induces respiratory mechanical changes that may impair pulmonary function during hyperbaric exercise. To evaluate this, 10 divers performed an incremental cycling protocol while immersed upright at 1.02 and 6.05 atmospheres absolute (atm abs). Air was supplied at each of two hydrostatic pressures: mouth pressure (Pm: to stimulate a mouth-held demand regulator) and lung centroid pressure (PLC). Subjects perceived air delivery at PLC to be more comfortable at each level of exercise at both absolute pressures (P less than 0.05). At 6.05 atm abs subjects perceived narcosis to be greater for Pm than for PLC air delivery. Hypoventilation was encountered at 6.05 atm abs with PLC air delivery and was further exacerbated when air was delivered at Pm (P less than 0.05). It was concluded that hypoventilation and narcosis are reduced whereas respiratory comfort is increased when air is delivered at PLC. This change is possibly due to improved pulmonary mechanics accompanying PLC air supply pressure.     

Respiratory function in the upright, working diver at 6.8 ATA (190 fsw)

The influence of static lung loading on a number of respiratory parameters was investigated in subjects performing graded leg exercise in an upright posture while submerged and breathing air at ambient pressures up to 6.76 ATA. In comparison with a previous investigation of the prone posture, a lesser tendency to dyspnea was observed. Neutral and moderately positive static lung loads were associated with less dyspnea than were negative loads. Several indices of respiratory function remained relatively normal during exercise and exposure to varying static lung loads. However, there was a tendency for hypoventilation and CO2 accumulation during heavy exercise at 190 fsw; this was not strictly correlated with dyspnea or static lung load. We conclude that, if a full face mask is used, breathing gear for divers should provide a static lung load of approximately 0 to +10 cmH2O regardless of the diver's orientation in the water. When possible, divers should assume an upright posture while engaged in strenuous work.     

Effects of pressure-demand respirator wear on physiological and perceptual variables during progressive exercise to maximal levels

Current regulations governing the certification of respiratory protective devices are based on data published in the early 1950s. The limited data base of this early work and documented increases in the average height of the population underscore the need for additional information concerning the parameters of certification. In the present study, a protocol using an inclined treadmill (0.5% grade every 12 sec) was used to test a heterogeneous population (n = 38). Through submaximal up to and including maximal exercise levels with and without respirator wear, maximal oxygen uptake (VO2max) was significantly greater (p less than 0.01) with the respirator (44.11 +/- 1.3 mL/kg.min) than without the respirator (42.18 +/- 1.4 mL/kg.min) while maximal ventilation volumes (VEmax) were not significantly different (with = 118.7 +/- 4 L/min; without 119.6 +/- 5 L/min). While peak inspired flows (PFI) with the respirator (268 +/- 7 L/min) were less than without the respirator (281 +/- 9 L/min), p greater than 0.05, the lower peak expired flow (PFE) with the respirator (289 +/- 12 L/min) than without the respirator (324 +/- 13 L/min), p less than 0.01, indicated a significant blunting effect of the respiratory flows by the expired resistance during exercise to maximal levels. Peak inspired pressures (PPi) with and without the respirator were not significantly different (p greater than 0.05). The negative values obtained within the facepiece of the respirator (-7.65 +/- 0.8 cmH2O), however, indicate that the positive pressure within the facepiece was lost, and respiratory protection may be compromised. Peak expired pressure with the respirator (13.05 +/- 0.7 cmH2O) was significantly greater than without the respirator (10.7 +/- 0.5 cmH2O) indicating that, despite a lower PFE, greater force was required to overcome the resistances of the respirator on expiration. The dyspnea index, an index of physiological effort; suggests that the subjects were working at a higher percentage of their respiratory reserve with the respirator (p less than 0.05) than without. Perceptually, subjects also felt that breathing with the respirator was more difficult (p less than 0.05). The maximum heart rate and the ratings of perceived exertion were not significantly different between the two tests at maximal exercise levels. Maximum oxygen uptake was considered reached when subjects attained a respiratory exchange ratio of at least 1.15, when a heart rate response at or greater than age-predicted maximum was achieved, when ratings of perceived exertion indicated exhaustion, and/or when the measure of VO2 had plateaued during the final minute of exercise.(ABSTRACT TRUNCATED AT 400 WORDS)     

潮气呼吸肺功能支气管舒张试验在5岁以内儿童喘息性疾病诊断中的作用

目的 探讨潮气呼吸肺功能检测在5岁以内儿童喘息性疾病中的临床意义.方法 选取2015年1月至2016年11月西安交通大学第一附属医院儿科门诊及住院部5岁以内(包括5岁)喘息患儿159例作为观察组,根据所患疾病将观察组分为肺炎组(支气管肺炎94例)、喘支组(喘息性支气管炎12例)、哮喘组(哮喘53例),另选取健康体检儿童64例作为对照组,进行潮气呼吸肺功能检测,观察喘息性疾病患儿支气管舒张试验前后肺功能指标及改善率的变化.结果 观察组患儿潮气呼吸流量-容积曲线环形态以阻塞性改变为主(83.02％).用药前,各组之间每公斤潮气量(Vt)、呼吸频率(RR)、吸气时间(Ti)、呼气时间(Te)、达峰时间比(TPTEF/TE)、达峰容积比(VPrEF/VE)差异具有统计学意义(F值分别为13.21、4.91、3.08、2.74、36.50、40.00,均P＜0.05).肺炎组吸入支气管舒张剂后的TPTEF/TE、VPTEF/VE与用药前比较差异有统计学意义(t值分别为2.86、3.14,均P＜0.05).哮喘组用药前后TPTEF/TE、VPTEF/VE差异无统计学意义(t值分别为1.36、1.18,均P＞0.05).各观察组用药前后,TtTEF/TE、VPTEF/VE改善率比较差异无统计学意义(x2值分别为o.02、o.91,均P＞0.05).以TPTEF/TE、VPTEF/VE任意一个改善率≥15％作为支气管舒张试验的阳性标准,灵敏度为20.75％,特异度为73.58％.结论 5岁以内喘息患儿肺功能损害以阻塞性通气障碍为主;潮气呼吸支气管舒张试验可在一定程度上反映哮喘气道可逆性特征,在5岁以内儿童中以潮气呼吸支气管舒张试验诊断哮喘的敏感性不高.     

Lung centroid pressure in immersed man

Upright immersion imposes a pressure imbalance between alveolar and mean external thoracic pressure. Lung centroid pressure (PLC) is defined as the breathing pressure required to remove this imbalance. Static transrespiratory pressure-volume relationships were determined in subjects immersed in upright (n = 17) and prone (n = 13) postures. Compliances measured during immersion (1.87 +/- 0.15 liter.kPa-1 upright, 1.87 +/- 0.17 liter.kPa-1) prone) were compared with compliances, obtained over the same volume range, while upright in air (1.84 +/- 0.17 liter.kPa-1). PLC was determined by the horizontal (pressure) displacement of immersed compliance curves. PLC was calculated to be +1.33 +/- 0.11 kPa (+13.6 cmH2O) relative to the sternal notch when upright and -0.69 +/- 0.12 kPa (-7.0 cmH2O) relative to the sternal plane when prone (mean +/- SEM). Upright PLC did not support the widely used value of +19 cmH2O (Jarrett AS. J Appl Physiol 1965;20:1261-1266). Analysis shows that when data from earlier investigations were adjusted for differences in reference pressure, the collective PLC supports the present results.     

Measurement of static and dynamic pulmonary work during pressure breathing

Various environments alter static and flow-resistive pulmonary mechanics. Of interest to diving physiologists is the negative pressure breathing induced during upright immersions without appropriate modification of air supply pressure. This paper outlines methodologic considerations for determining static and flow-resistive pulmonary work under such exposures. Ten males performed inspiratory pressure-volume relaxation maneuvers and spontaneous breathing in air, and during upright immersion with mouth pressure air supply. The immersed lung centroid pressure (PLC) was +1.19 kPa relative to the hydrostatic pressure at the sternal notch. Immersion elevated inspiratory static work from 0.36 to 1.74 J.liter-1 (P less than 0.05). Pulmonary flow-resistive work was elevated from 0.20 to 0.75 J.liter-1 (P less than 0.05), whereas pulmonary resistance, determined at 0.5 liter.sec-1, increased from 0.18 to 0.44 kPa.liter-1.sec (P less than 0.05). No significant changes in the iso-volume compliance of the lung tissue, chest wall, or total respiratory system were observed (P greater than 0.05). Results indicate that increases in the work of breathing are due to a combination of hydrostatic pressure imbalance, increased pulmonary resistance, and reduced end-expiratory total respiratory compliance.     

Physiologically and subjectively acceptable breathing resistance in divers' breathing gear.

To determine acceptable levels of breathing resistance in divers' gear, 6 subjects were exposed to varying levels of breathing resistance under demanding and realistic conditions. The immersed air-breathing subjects exercised in the prone position at 60% of their maximum oxygen uptake for 25 min in a hyperbaric chamber at 1.45 and 6.8 atm abs (145 and 690 kPa, 4.5 and 57 msw, 15 and 190 fsw). The breathing resistance ranged from minimal to 8-12 cmH2O (0.8-1.2 kPa).liter-1.s at flow rates of 2-3 liter/s. The higher resistance levels interfered with the respiration in terms of end-tidal PCO2 and dyspnea scores. There were considerable individual differences, and changes in one parameter were typically not paralleled by changes in the other. None of maximal voluntary ventilation, forced expiratory volume, expiratory reserve volume, vital capacities, or oxygen uptake was influenced by resistance. We set the maximum allowable end-tidal PCO2 at 60 mmHg and maximum dyspnea score at 1.0 on a scale from 0 (none) to 3 (severe). Based on these criteria we concluded that the external work of breathing should not exceed 1.5-2.0 J/liter in the ventilation range 30 to 75 liter/min BTPS.     

Pulmonary atelectasis formation during diving with closed-circuit oxygen breathing apparatus

The physiological effects of diving with two types of closed-circuit oxygen breathing apparatus were investigated in 4 divers. In one apparatus the breathing bag was mounted on the dorsum and in the other on the chest, inducing -2 kPa and +1 to +2 kPa static lung load in the prone position, respectively. The back-mounted bag caused an unfavorable swimming position, with increased heart rate, breathing rate, and rating of perceived exertion (RPE) for work load. The greater internal and external work of breathing (the latter judged from the higher RPE for breathing resistance) probably contributed to a higher RPE for discomfort with the back-mounted bag. Three divers showed great reduction in vital capacity (VC) (0.8 to 1.9 liters) and developed coughing attacks after dives with this apparatus; these results were interpreted as possible indications of atelectasis formation. The 4th diver showed slight reduction in VC with both types of bag, possibly because the changes in static lung loads did not influence the airway closure in this man.     

盐酸氨溴索气道湿化对婴幼儿重症肺炎机械通气时呼吸力学的影响

目的 观察机械通气时用盐酸氨溴索气道湿化对婴幼儿重症肺炎呼吸力学的影响.方法 选取符合婴幼儿重症肺炎诊断标准并需机械通气治疗的65例婴幼儿,按随机数字表法分为试验组33例和对照组32例.试验组用盐酸氨溴索气道湿化,对照组用0.9％氯化钠,每次2 ml气管内滴入,然后接球囊加压给氧30 s,再接呼吸机通气,湿化后5 min彻底吸痰,24 h后观察治疗前后呼吸力学指标的变化：平均气道阻力、肺顺应性、呼吸功、气道平台压.比较两组治疗前后呼吸力学指标改变.结果 机械通气治疗24 h后,试验组呼吸力学指标较对照组明显改善[平均气道阻力分别为（0.68±0.04） cmH2O/（L·s）和（0.57±0.05） cmH2O/（L·s）,1 cmH2O=0.098 kPa,肺顺应性分别为（3.17±0.81） ml/kPa和（2.56±0.69）ml/kPa,呼吸功分别为（0.54±0.08） J/L和（0.41±0.06） J/L,气道平台压分别为（2.23±0.58） cmH2O和（2.12±0.63） cmH2O],差异有统计学意义（P＜0.05）;试验组较对照组机械通气时间明显缩短,分别为（64.08±13.92）h和（79.57±19.64）h,差异有统计学意义（P＜0.05）.结论 机械通气时给予盐酸氨溴索气道湿化,能够改善婴幼儿重症肺炎呼吸力学指标,有效治疗重症肺炎,减少气道阻力,改善肺泡通气,缩短机械通气时间.     

Effects of Sarcopenia on Ventilatory Behavior and the Multidimensional Nature of Dyspnea in Patients With Chronic Obstructive Pulmonary Disease

ObjectivesThis study tested the hypothesis that sarcopenia, a common extrapulmonary feature of chronic obstructive pulmonary disease (COPD), can affect ventilatory behavior, and worsen the multidimensional nature of dyspnea in patients with COPD.DesignCross-sectional survey study.Settingand Participants: Stable outpatients with COPD encountered in general practice and respiratory clinic.MethodSarcopenia was diagnosed according to an appendicular skeletal muscle mass index based on measurements of electrical impedance and handgrip strength. Exertional dyspnea was tested using a 3-minute Step Test and a 6-minute Walk Test. The dimensions of dyspnea were assessed by a multidimensional dyspnea profile.ResultsOf 60 stable patients with COPD, 16 met the criteria for sarcopenia. During the 3-minute Step Test, minute ventilation as a proportion of exercise time, tidal volume as a proportion of inspiratory capacity, the change in inspiratory capacity, and ventilation as a proportion of maximal voluntary ventilation did not differ between patients with and without sarcopenia. Patients with sarcopenia exhibited lower evolution of tidal volume, higher evolution of respiratory frequency versus ventilation and breathing discomfort on the 3-minute Step Test, as well as increased physical breathing effort on the 6-minute Walk Test, compared with those without sarcopenia. In a multivariable model adjusted using inverse probability weighting, sarcopenia was independently associated with breathing discomfort during the 3-minute Step Test and physical breathing effort during the 6-minute Walk Test.Conclusions and ImplicationsSarcopenia may be associated with shallow breathing and diverse sensory and affective components of exertional dyspnea in patients with COPD. The study indicates that improvement of the rapid breathing pattern may offer unique ways to alleviate dyspnea in older patients with COPD and sarcopenia.     

Effects of grain dust exposure and smoking on respiratory symptoms and lung function

In four groups of individually-matched subjects (nonsmoking grain workers, smoking grain workers, nonsmoking community controls, and smoking community controls) we measured pulmonary function variables from the spirogram, from the maximal expiratory flow-volume curve breathing air and helium, and from the single breath nitrogen test as well as symptom prevalences from a questionnaire in order to assess the relative effects of smoking and occupational exposure to grain dust in Saskatchewan country grain elevators. There were similar increased prevalences of respiratory symptoms and reductions in pulmonary function associated with either grain dust exposure or smoking, but the effects of smoking were slightly more pronounced. The combined effects of grain dust and smoking on lung function appeared to be additive except in the least exposed workers (five years or less) where a synergistic effect was observed in tests of peripheral airways dysfunction.     

Study of respirator effect on nasal-oral flow partition

Factors affecting worker tolerance of respiratory personal protective devices are inadequately understood. This study evaluates whether respirator-type loads affected the switch from nasal to oral breathing. Eleven healthy subjects were studied under progressive exercise conditions, using a respirator full-face mask with inspiratory resistance (I), pressure breathing (P) (10 cm H₂O end-expiratory pressure), or no load (N). A rapid-response thermistor was used to determine whether flow was predominantly oral or nasal. Both P and I increased the percentage of time that breathing was predominantly oral. The effect was most pronounced at higher exercise levels. The percentage of mouth breathing appeared to be closely related to the expiratory time. This study suggests that nasal-oral flow partitioning should be considered as a possible determinant of respirator tolerance. Am. J. Ind. Med. 32:408–412, 1997. © 1997 Wiley-Liss, Inc.     

改良斜卧截石位在微刨经皮肾镜碎石患者手术中的应用

目的探讨斜卧截石位对微创经皮肾镜碎石取石术（PCNL）患者的影响。方法将60例微创经皮肾镜碎石手术患者．分为俯卧位、侧卧位、斜卧截石位组,每组各20例。观察3种体位安置前后患者心率、血压的变化;记录手术时间,患者术后的舒适度。结果3种体位均能顺利完成手术,斜卧截石位体位安置后血压、心率较前两种体位更稳定,手术时间明显缩短,与侧卧位比较舒适度明显提高。结论PCNL患者采用斜卧截石位,既保证患者的舒适度,又方便手术操作、稳定呼吸循环功能,能提高工作效率。     

两种肺保护通气模式在重症创伤性湿肺通气策略中的比较

目的 比较两种肺保护通气模式在重症创伤性湿肺时施行肺保护通气策略中的临床意义.方法 将92例重症创伤性湿肺患者按随机数字表法分为适应性支持通气（ASV）组和压力型同步间歇指令通气（P-SIMV）＋压力支持通气（PSV）组,每组46例,比较两组患者机械通气后30 min的心率、平均动脉压（MAP）、pH值、动脉血氧分压（PaO2）、动脉血二氧化碳分压（PaC O2）、每分钟通气量、潮气量、总呼吸频率、气道峰压、平均气道压、气道闭合内压、肺顺应性.结果 机械通气后30 min,两组患者心率、MAP、pH值、PaO2、PaCO2、平均气道压、气道峰压、气道闭合内压比较差异均无统计学意义（P＞0.05）,但ASV组潮气量、每分钟通气量、总呼吸频率、肺顺应性均较P-SIMV＋PSV组明显改善[（692.6±38.6） ml比（558.5±25.6） ml、（8.9±1.7）L比（7.8±1.6）L、（16.3±3.3）次/min比（21.3±3.2）次/min、（42.15±5.28） ml/cmH2O（1 cmH2O=0.098 kPa）比（39.15±5.47） ml/cmH2O],差异均有统计学意义（P＜0.01或＜0.05）.结论 对于重症创伤性湿肺患者在施行肺保护通气策略时,ASV可根据患者的呼吸力学状况自动调整吸气压力支持水平,提高潮气量、增加肺顺应性、降低呼吸频率,而对血流动力学和生命体征无明显影响.     

Discomfort and exertion associated with prolonged wear of respiratory protection in a health care setting

The nature of discomfort and level of exertion associated with wearing respiratory protection in the health care workplace are not well understood. Although a few studies have assessed these topics in a laboratory setting, little is known about the magnitude of discomfort and the level of exertion experienced by workers while they deliver health care to patients for prolonged periods. The purpose of this study was to determine the magnitude of discomfort and level of exertion experienced by health care workers while wearing respiratory protection for periods up to 8 hr when performing their typical occupational duties. This project was a multiple cross-over field trial of 27 health care workers, aged 24-65, performing their typical, hospital-based occupational duties. Each participant served as his/her own control and wore one of seven respirators or a medical mask for 8 hr (or as long as tolerable) with interposed doffing periods every 2 hr. Self-perceived discomfort and exertion were quantified before each doffing: self-perceived level of discomfort using a visual analog scale, and self-perceived level of exertion using a Borg scale. Overall, and as would be expected, discomfort increased over time with continual respirator use over an 8-hr period. Interestingly, exertion increased only marginally over the same time period. The relatively low level of exertion associated with eight respiratory protective devices, including models commonly used in the U.S. health care workplace, is not likely to substantially influence workers' tolerability or occupational productivity. However, the magnitude of discomfort does appear to increase significantly over time with prolonged wear. These results suggest that respirator-related discomfort, but not exertion, negatively influences respirator tolerance over prolonged periods. Discomfort may also interfere with the occupational duties of workers.     

吸气肌训练改善肥胖大学生吸气肌力量和运动能力效果分析

  目的  观察8周吸气肌训练对肥胖大学生肺功能、呼吸肌力量、运动能力、身体成分以及脂质代谢的影响,为肥胖患者优化康复方案提供依据。  方法  于2019年8—10月招募58名肥胖大学生随机分为实验组(28名)和对照组(30名)。实验组进行每周3次强度为50%最大吸气压(P_Imax)、共8周的吸气肌训练,对照组接受的训练除强度设定为5%P_Imax外,其他参数与实验组相同。干预前后分别测定肺功能、呼吸肌力量、运动能力、身体成分和血脂等指标。  结果  实验组和对照组训练计划完成率(依从性)分别为98.0%和99.2%。干预过程中无严重不良事件发生。干预后,实验组P_Imax和6 min步行试验(6MWT)距离较干预前增加(t值分别为-7.44,-4.11,P值均 < 0.05),6MWT后的自我疲劳感觉(RPE)和心率下降(t值分别为2.13,2.63,P值均 < 0.05),而肺功能、身体成分和血脂水平的变化无统计学意义(P值均>0.05);对照组上述各指标的变化均无统计学意义(P值均>0.05)。  结论  8周吸气肌训练能够有效改善肥胖大学生吸气肌力量和运动能力,但对呼气肌力量、肺功能、身体成分和血脂水平并无影响。