Assisted cough and pulmonary compliance in patients with Duchenne muscular dystrophy

The aim of this study was to investigate the factors affecting cough ability, and to compare the assisted cough methods in patients with Duchenne muscular dystrophy (DMD). A total seventy-one male patients with DMD were included in the study. The vital capacity (VC) and maximum insufflation capacity (MIC) were measured. The unassisted peak cough flow (UPCF) and three different techniques of assisted peak cough flow were evaluated. UPCF measurements were possible for all 71 subjects. But when performing the three different assisted cough techniques, peak cough flows (PCFs) could be obtained from only 51 subjects. The mean value of MICs (1801 +/- 780 cc) was higher than that of VCs (1502 +/- 765 cc) (p< 0.01). All three assisted cough methods showed a significantly higher value than the unassisted method (F=80.92, p< 0.01). The manual assisted PCF under MIC (MPCFmic) significantly exceeded those produced by manual assisted PCF (MPCF) or PCF under MIC (PCFmic). The positive correlation between the MIC, VC difference (MIC-VC), and the difference between PCFmic and UPCF (PCFmic-UPCF) was seen (r=0.572, p< 0.01). The preservation of pulmonary compliance is important for the development of an effective cough as well as assisting the compression and expulsive phases. Thus, the clinical importance of the inspiratory phase and pulmonary compliance in assisting a cough should be emphasized.     

创伤性颈脊髓损伤患者咳嗽音一般特征及其与呼吸肌力量的相关性

目的分析创伤性颈脊髓损伤(TCSCI)患者咳嗽音的一般特征,并探讨其与呼吸肌力量的相关性。方法选取南部战区总医院收治的29例TCSCI患者作为TCSCI组,并随机选取同时段的26例非TCSCI患者作为对照组。分别收集患者咳嗽音信号、呼吸肌力量指标最大吸气压力(MIP)和最大呼气压力(MEP),同时记录2组患者年龄、身高、体质量以及基础疾病等基线资料,记录TCSCI组ASIA分级、损伤节段以及呼吸衰竭发生情况。分析比较2组咳嗽音差异及其与MIP、MEP的相关性,并探讨咳嗽音指标对呼吸衰竭的预测价值。结果2组患者基线资料比较,差异无统计学意义(P>0.05)。TCSCI组咳嗽音评分高于对照组(P<0.01),MIP、MEP、咳嗽峰值流量(CPF)、最大强度、平均强度、有效声压及声压级均低于对照组(P<0.01)。相关性分析显示,咳嗽音评分与MIP、MEP呈负相关(P<0.01),CPF、最大强度、平均强度、有效声压、声压级与MIP、MEP均呈正相关(P<0.01)。亚组分析显示,咳嗽音评分能很好预测TCSCI患者是否发生呼吸衰竭,曲线下面积(AUC)为0.745。结论TCSCI患者咳嗽音指标会发生显著改变且同呼吸肌力量存在相关性,可用于评估TCSCI患者呼吸功能;咳嗽音评分可作为预测TCSCI患者是否发生呼吸衰竭的指标。     

Cough determinants in patients with neuromuscular disease

Neuromuscular disease leads to cough impairment. Cough augmentation can be achieved by mechanical insufflation (MI) or manually assisted coughing (MAC). Many studies have compared these two methods, but few have evaluated them in combination. In 155 neuromuscular patients, we assessed determinants of peak cough flow (PCF) using stepwise correlation. Maximal inspiratory capacity contributed 44% of the variance (p<0.001), expiratory reserve volume 13%, and maximal expiratory pressure 2%. Thus, augmenting inspiration seems crucial. However, parameters dependent on expiratory muscles independently influence PCF. We measured vital capacity and PCF in 10 neuromuscular patients during cough augmentation by MI, MAC, or both. MI or MAC significantly improved VC and PCF (p<0.01) as compared to the basal condition and VC and PCF were higher during MI plus MAC than during MAC or MI alone (p<0.01). In conclusion, combining MAC and MI is useful for improving cough in neuromuscular patients.     

The kinanthropometric and pulmonary determinants of global respiratory muscle strength and endurance indices in an athletic population

The morphological determinants of respiratory muscle (RM) strength and endurance in non-athletic populations are well documented, but are lacking in athletic populations. The purpose of this study was to determine the kinanthropometric and pulmonary predictors of RM strength and endurance. 160 athletes (103 men) were recruited from eight different sports to participate in the study. All subjects underwent a series of kinanthropometric and RM function assessments during a single visit to the laboratory. RM function assessments included the flow-volume curve test to assess pulmonary function, maximum voluntary ventilation (MVV) to assess RM endurance and maximum inspiratory mouth pressure (MIP) and maximum expiratory mouth pressure (MEP) to assess RM strength. Multiple regression analyses revealed that gender, mesomorphy and exercise sessions per week predicted 35% (SEE = 26.6 cmH₂O) of the variance in inspiratory muscle strength (MIP). Gender and mesomorphy predicted 24% (SEE = 28.3 cmH₂O) of the variance in expiratory muscle strength (MEP), while gender, relative sitting height, forced expiratory volume in 1 s (FEV₁) and peak expiratory flow rate (PEFR) predicted 78% (SEE = 18.2 L min⁻¹) of the variance in RM endurance (MVV). Although the reference equations are still not adequate to predict MIP and MEP in an athletic population, they provide more suitable reference values than previously reported. The predicted values derived from the equation for MVV can be applied as adequate reference values for athletic populations.     

Serum skeletal troponin I following inspiratory threshold loading in healthy young and middle-aged men

The purpose of this study was to determine if serum levels of skeletal troponin I (sTnI, fast and slow isoforms) could provide a sensitive marker of respiratory muscle damage in healthy humans subjected to inspiratory loads. To accomplish this, we studied healthy, young (27?±?2?years, Mean?±?SEM, n?=?5) and middle-aged (55?±?5, n?=?5) men to (1) determine the magnitude, pattern, and time course of the presence of sTnI in the serum after a single 60?min bout of inspiratory threshold loading [ITL, ~70% of maximal inspiratory pressure (MIP)], (2) determine the distribution and magnitude of DOMS after loading, and (3) compare fast and slow sTnI levels, and their relationship to other markers/indices of muscle injury including delayed onset muscle soreness (DOMS), serum creatine kinase (CK) levels, and force generating capacity of the respiratory muscles [MIP and maximal expiratory pressure (MEP)]. There was a 24?±?4 and 27?±?3% increase in fast sTnI 1?hour (p?相似文献   

Mouth pressure twitches induced by cervical magnetic stimulation to assess inspiratory muscle fatigue

This study aimed at determining whether twitch mouth pressure (TwPmo) induced by cervical magnetic stimulation (CMS) was sensitive to inspiratory muscle fatigue produced by whole body exercise (WBE) in normal subjects. Twenty subjects performed one or two of the following protocols: (i). cycling at 85% V(O(2),max) until exhaustion; (ii). inspiratory resistive load (IRL) breathing at 62% of maximal inspiratory pressure until task failure. In eight subjects, oesophageal (TwPoes), gastric (TwPga) and transdiaphragmatic (TwPdi) pressures were recorded. The TwPmo was significantly reduced (P<0.05) 20 min after both WBE and IRL, from 17.5+/-4.4 to 15.9+/-3.9 cmH(2)O and from 19.4+/-4.9 to 17.7+/-4.5 cmH(2)O, respectively. Subsequently to IRL, the TwPdi decrease was associated with a reduction in TwPoes/TwPga ratio; not after WBE. Independently of the mode of ventilatory loading, inspiratory muscle fatigue was detected. Thus, inspiratory muscle fatigue after WBE can be assessed in normal subjects with a noninvasive technique.     

A Comparison of Cough Assistance Techniques in Patients with Respiratory Muscle Weakness

PurposeTo assess the ability of a mechanical in-exsufflator (MI-E), either alone or in combination with manual thrust, to augment cough in patients with neuromuscular disease (NMD) and respiratory muscle dysfunction.ResultsAll 40 enrolled participants (37 males, three females; average age, 20.9±7.2 years) completed the study. The mean (standard deviation) PCFs in the unassisted, manually assisted following an MIC maneuver, MI-E-assisted, and manual thrust plus MI-E-assisted conditions were 95.7 (40.5), 155.9 (53.1), 177.2 (33.9), and 202.4 (46.6) L/min, respectively. All three interventions significantly improved PCF. However, manual assistance following an MIC maneuver was significantly less effective than MI-E alone. Manual thrust plus MI-E was significantly more effective than both of these interventions.ConclusionIn patients with NMD and respiratory muscle dysfunction, MI-E alone was more effective than manual assistance following an MIC maneuver. However, MI-E used in conjunction with manual thrust improved PCF even further.     

Chest wall volume changes during inspiratory loaded breathing

We assessed the effect of inspiratory loaded breathing (ILB) on respiratory muscle strength and investigated the extent to which respiratory muscle fatigue is associated with chest wall volume changes during ILB. Twelve healthy subjects performed ILB at 76 ± 11% of maximal inspiratory mouth pressure (MIP) for 1h. MIP and breathing pattern during 3 min of normocapnic hyperpnea (NH) were measured before and after ILB. Breathing pattern and chest wall volume changes were assessed by optoelectronic plethysmography. After ILB, six subjects decreased MIP significantly (-16 ± 10%; p < 0.05), while the other six subjects did not (0 ± 7%, p = 0.916). Only subjects with decreased MIP after ILB lowered end-expiratory rib cage volume (volume at which inspiration is initiated) below resting values during ILB. During NH after ILB, tidal volume was smaller in subjects with decreased MIP (-19 ± 16%, p < 0.05), while it remained unchanged in the other group (-3 ± 11%, p = 0.463). These results suggest that respiratory muscle fatigue depends on the lung volume from which inspiratory efforts are made during ILB.     

124例健康成人吸气肌强度和耐力测定

本文测定了124例健康成人最大吸气压和最大持续吸气压,探讨吸气肌强度和耐力的分布及影响因素。发现最大吸气压和最大持续吸气压受年龄、体重和性别响影,吸气肌张力时间指数0.30可作为检测吸气肌疲劳的临界阈值。     

Evoked corticospinal output to the human scalene muscles is altered by lung volume

Increases in lung volume inhibit the inspiratory output from the medulla, but the effect of lung inflation on the voluntary control of breathing in humans is not known. We tested corticospinal excitability using transcranial magnetic stimulation (TMS) to evoke a response in the scalene muscles. TMS was delivered at rest at three different lung volumes between functional residual capacity (FRC) and total lung capacity (TLC) during incremental inspiratory and incremental expiratory manoeuvres. Motor evoked potentials (MEPs) in scalenes were ～50% larger at a high lung volume (FRC+～90% inspiratory capacity [IC]) compared to lower lung volumes (FRC and FRC+～40% IC) in both inspiratory and expiratory manoeuvres (p<0.001). The change in MEP size was not due to differences in pre-stimulus EMG amplitude (p=0.29). The results suggest a differential effect of lung inflation on the automatic and voluntary control of breathing in humans.     

Controlled twitch mouth pressure reliably predicts twitch esophageal pressure

The present study hypothesized that twitch mouth pressure (TwPmo) can reliably predict intrathoracic pressure swings reflected by twitch esophageal pressure (TwPes) using a controlled and automated trigger technique. TwPmo, TwPes, and transdiaphragmatic pressure (TwPdi) following bilateral anterior magnetic phrenic nerve stimulation were measured in 21 healthy subjects using an inspiratory pressure trigger (0.5kPa, experiment 1), an expiratory pressure trigger (0.5kPa, experiment 2), an inspiratory flow trigger (40ml/s, experiment 3), and no trigger at relaxed functional residual capacity (experiment 4). TwPmo and TwPes were correlated as follows: r=0.99, p<0.0001 (experiment 1); r=0.67, p=0.001 (experiment 2); r=0.96, p<0.0001 (experiment 3); no correlation (experiment 4). Bland and Altman analysis revealed most narrow limits of agreement for TwPmo and TwPes in experiment 1: bias (range) 0.15kPa (-0.03 to 0.32). TwPmo is an excellent predictor for TwPes when using a fully automated and controlled inspiratory pressure trigger. Thus, measurement of TwPmo could become a standard means assessing inspiratory muscle strength.     

Specially programmed respiratory muscle training for singers by using respiratory muscle training device (Ultrabreathe)

Respiratory muscle training is one of the major methods for enhancing the vocal function. Singers who must use their voice most frequently are well aware of the importance of respiration. However, most of them do not know precisely how to exercise their abdominal respiration. Using a respiratory training device, singers are expected to gain more efficiency in their vocal enhancement. The aim of the study was to examine the pulmonary function, the maximum inspiratory pressure (MIP) and the maximum expiratory pressure (MEP), and the maximum phonation time (MPT) in five female voice-majors students after undergoing specially programmed respiratory muscle training for 2 months. All the voice-majors had an average of 4.8 years of formal classical voice training. A respiratory muscle training device (Ultrabreathe), Tangent health Care Inc., England) was used to train the respiratory muscle. None of the pulmonary function test variables had changed after respiratory muscle training. However, the MIP, MEP, and MPT were significantly increased higher after the respiratory muscle training. This suggests that the specially programmed respiratory muscle training can improve the respiratory muscle strength and vocal function without increasing the pulmonary function.     

Respiratory response to inspiratory resistive load changes in patients with obstructive sleep apnea syndrome

Patients with OSA have many episodes of increased airway resistance because of repeated collapses of upper airways during night. The aim of this work was to evaluate respiratory response during chemical stimulation without and with added inspiratory resistive load (10 cmH2O/L/sec). The studies were performed during quiet breathing with air and during hypercapnic and hypoxic rebreathing tests without and with inspiratory resistive loading in 23 obese (BMI = 34.4 +/- 4.3 kg/m2) patients with OSA and in 10 healthy subjects with similar weight (BMI = 32.4 +/- 4.3 kg/m2). The measurements of respiratory responses (ventilation, mouth occlusion pressure) were performed with the use of computerized equipment. During quiet breathing in response to added load an increase of P0.1 in controls and in OSA patients was observed. During hypercapnic stimulation the ventilatory response with additional load decreased in patients as well as in controls. The slope of mouth occlusion pressure response increased significantly in controls (from 4.40 to 6.83 cmH2O/kPa, p < 0.001) and slightly weaker in OSA patients (from 4.21 to 5.43 cmH2O/kPa, p < 0.05). Although the difference between the slopes was not significant, we found that the absolute increase of P0.1 measured at point 8 kPa of PEtCO2 during loaded breathing was significantly smaller in OSA patients in comparison to controls. (2.1 vs. 10.3 cm H2O; p < 0.001). During hypoxic stimulation occlusion pressure responses were similar in both examined groups. In conclusion we postulate that OSA patients have impaired respiratory compensation of additional inspiratory load, what was demonstrated during hypercapnic rebreathing test.     

Diaphragm and intercostal surface EMG and muscle performance after acute inspiratory muscle loading

We examined the effect of an acute bout of submaximal non-fatiguing inspiratory loading (IL) on maximal inspiratory pressure (MIP), and on the activation of the diaphragm (DI) and intercostals (IC) using surface electromyography (sEMG). After baseline measurements, 12 healthy subjects performed two sets of 30 inspiratory efforts at a load equivalent to 40% of their initial MIP. MIP and maximal DI and IC sEMG activity were recorded after the first and second set of IL, and 15 min after task cessation. After IL, MIP reached (+/-S.E.M.) 111+/-4% (P=0.032) of baseline values, and during MIP, DI and IC root mean square (RMS) sEMG amplitude increased significantly above baseline (143+/-21%, P=0.039 and 137+/-33%, P=0.016, respectively). The significant increase in MIP and RMS amplitude after IL suggests that MIP efforts were initially submaximal, and that prior loading enabled full activation. The changes in DI and IC RMS amplitude may also reflect an improvement in the synergy between them during these maximal efforts.     

Inspiratory and expiratory lung pressure-volume curve in healthy males and females

Quasistatic lung inspiratory and expiratory pressure-volume curves were obtained in 58 healthy nonsmoking males (mean age +/- SD: 42.8 +/- 15.1 years; range 22.70) and 56 healthy nonsmoking females (mean age +/- SD: 41.4 +/- 15.6 years; range: 21-76). Inspiratory and expiratory lung recoil pressures were measured at fixed percentages of TLC (100, 95, 90, 80, 70, 60 and 50%). In both sexes, inspiratory as well as expiratory lung recoil pressures were found to decrease linearly with aging (p less than 0.01 for all r values). There was no significant difference between males and females. At and above the 70% TLC level, the slopes of the age-related decreases in lung recoil were similar for the inspiratory and expiratory curves. At the 60% TLC level, the decrease in expiratory lung recoil was significantly (p less than 0.01) faster than the decrease in inspiratory lung recoil, presumably reflecting the influence of airway opening on the inspiratory pressure in older subjects. The shape of the expiratory PV curve described by the K index of the exponential model was similar in both sexes and changed with aging, K increasing significantly (p less than 0.01). By contrast, the shape of the inspiratory limb of the PV curve did not vary with aging. Consequently, the shape of the inspiratory PV curve cannot be predicted from the expiratory one and has to be measured directly.     

Ventilatory responses to exercise training in obese adolescents

The aim of this study was to examine ventilatory responses to training in obese adolescents. We assessed body composition, pulmonary function and ventilatory responses (among which expiratory flow limitation and operational lung volumes) during progressive cycling exercise in 16 obese adolescents (OB) before and after 12 weeks of exercise training and in 16 normal-weight volunteers. As expected, obese adolescents' resting expiratory reserve volume was lower and inversely correlated with thoraco-abdominal fat mass (r=-0.74, p<0.0001). OB presented lower end expiratory (EELV) and end inspiratory lung volumes (EILV) at rest and during submaximal exercise, and modest expiratory flow limitation. After training, OB increased maximal aerobic performance (+19%) and maximal inspiratory pressure (93.7±31.4 vs 81.9±28.2cmH(2)O, +14%) despite lack of decrease in trunk fat and body weight. Furthermore, EELV and EILV were greater during submaximal exercise (+11% and +9% in EELV and EILV, respectively), expiratory flow limitation delayed but was not accompanied by increased V(T). However, submaximal exertional symptoms (dyspnea and leg discomfort) were significantly decreased (-71.3% and -70.7%, respectively). Our results suggest that exercise training can improve pulmonary function at rest (static inspiratory muscle strength) and exercise (greater operating lung volumes and delayed expiratory flow limitation) but these modifications did not entirely account for improved dyspnea and exercise performance in obese adolescents.     

Canine awake head-out plethysmography (HOP): characterization of external resistive loading and spontaneous laryngeal paralysis

We applied a novel head-out plethysmographic (HOP) method to study awake canine responses to external resistive loading and natural laryngeal paralysis. Measurements of inspiratory and expiratory specific airway resistance (sRaw(insp), sRaw(exp)) were obtained before and after uni- and bidirectional loading (R(add) = 5 cmH(2)O/L/s) in large-breed dogs (n = 9). Mean sRaw(insp) after inspiratory, and sRaw(exp) after expiratory loading were 31.4 and 33.3 cmH(2)Os, respectively. Bidirectional loads induced a significantly greater rise in both sRaw(insp) and sRaw(exp) (55.1 and 61.3 cmH(2)Os) compared to unidirectional loading (P < 0.001). Yet, type of loading did not affect flow-volume indices. The mean R(aw) of dogs was 4.81 cmH(2)O/L/s. Expiratory loading resulted in a significant 8.8% increase in functional-residual-capacity (FRC), compared to FRC(baseline) (76.7 ml/kg). Dogs (n = 5) with laryngeal paralysis demonstrated a significant increase in sR(aw) and R(aw) compared to controls without changes in FRC. In conclusion, HOP precisely characterized sR(aw) in response to external resistive loading. Hence, we could accurately quantify airway obstruction in awake dogs with laryngeal paralysis.     

A comparison of inspiratory muscle fatigue following maximal exercise in moderately trained males and females

Exercise-induced inspiratory muscle fatigue (IMF) has been reported in males but there are few reports of IMF in females. It is not known if a gender difference exists for inspiratory muscle strength following heavy exercise, as is reported in locomotor muscles. Therefore, the relationship between fatigue and subsequent recovery of maximal inspiratory pressure (MIP) following exercise to maximal oxygen consumption was examined in a group of moderately trained males and females. Eighteen males (23±3 years; mean ± SD) and 16 females (23±2 years) completed ten MIP and ten maximal handgrip (HG) strength maneuvers to establish baseline. Post-exercise MIP and HG were assessed successively immediately following a progressive intensity test on a cycle ergometer and at 1, 2, 3, 4, 5, 10, and 15 min. relative to fat-free mass was not statistically different between males (62±7 ml kg^–1 min^–1) and females (60±8 ml kg^–1 min^–1). Males had higher absolute MIP values than females at all time intervals (P<0.05). Immediately following exercise, MIP was significantly reduced in both genders (M=83±16%; F=78±15% of baseline) but HG values were not different than resting values. MIP values remained depressed for both males and females throughout the 15 min (P<0.05). Differences for MIP between males and females were not statistically significant at any measurement time (P>0.05). The findings in this study conclude that IMF, observed immediately following maximal exercise, demonstrated the same pattern of recovery for both genders.     

The effects of different inspiratory muscle training intensities on exercising heart rate and perceived exertion

This study investigated the relationship between the intensity of an inspiratory muscle training programme and its effect on respiratory muscle strength, exercising heart rate, and ratings of perceived exertion. A total of 66 subjects were randomly assigned to one of three groups. One group trained at 100% of maximum inspiratory pressure (MIP) for 6 weeks (MAX, n=22). A second group performed 6 weeks of inspiratory muscle training at 80% of MIP (SUB, n=21) and a third control group received no inspiratory training (CON, n=23). Both the MAX and SUB training groups improved MIP relative to the control group [32 (19) cmH₂O, P=0.01; 37 (25) cmH₂O, P=0.001, respectively]. A significant decrease in heart rate [–6 (9) beats min^–1, P=0.02] and rating of perceived exertion [–0.5 (1.4), P=0.04] was observed for the MAX group only. It is concluded that 6 weeks of both MAX and SUB training were sufficient to improve inspiratory muscle strength. However, exercising heart rate and perceived exertion decreased with MAX training only.