Noninvasive detection of expiratory flow limitation in COPD patients during nasal CPAP.

The difference between mean inspiratory and expiratory respiratory reactance (delta(rs)) measured with forced oscillation technique (FOT) at 5 Hz allows the detection of expiratory flow limitation (EFL) in chronic obstructive pulmonary disease (COPD) patients breathing spontaneously. This aim of this study was to evaluate whether this approach can be applied to COPD patients during noninvasive pressure support. Delta(rs) was measured in seven COPD patients subjected to nasal continuous positive airway pressure (CPAP) at 0, 4, 8 and 12 cmH2O in sitting and supine positions. Simultaneous recording of oesophageal pressure and the Mead and Whittenberger (M-W) method provided a reference for scoring each breath as flow-limited (FL), non-flow-limited (NFL) or indeterminate (I). For each patient, six consecutive breaths were analysed for each posture and CPAP level. According to M-W scoring, 47 breaths were FL, 166 NFL and 51 I. EFL scoring using FOT coincided with M-W in 94.8% of the breaths. In the four patients who were FL in at least one condition, delta(rs) was reduced with increasing CPAP. These data suggest that the forced oscillation technique may be useful in chronic obstructive pulmonary disease patients on nasal pressure support by identifying continuous positive airway pressure levels that support breathing without increasing lung volume, which in turn increase the work of breathing and reduce muscle effectiveness and efficiency.     

应用强迫振荡技术优化慢性阻塞性肺疾病患者经鼻罩无创通气压力水平的探讨

目的 探讨利用强迫振荡阻抗和电抗方法优化COPD患者经鼻罩无创通气压力水平的合理性.方法 研究对象为2007年6月至2008年2月在广州呼吸疾病研究所住院的8例COPD合并2型呼吸衰竭患者,分别给予不同压力水平的双水平气道正压通气和连续气道正压通气(CPAP),采用5 Hz强迫振荡信号检测各呼吸周期的吸气相阻抗,以食道测压法测定的吸气相肺阻力为参照,比较两者的一致性和相关性;计算CPAP分别为4、8和12 cm H2O(1 cm H2O=0.098 kPa)时各呼吸周期的呼气相与吸气相电抗之差(△Xrs),分析各呼吸周期的跨肺压与流量的关系,将上述各呼吸周期划分为有或无呼气流速受限(EFL),比较CPAP水平、△Xrs值和显示为EFL的呼吸周期数之间的数量关系,计算检测EFL呼吸周期敏感度和特异度均最高的△Xrs阈值.正态分布资料均数的比较采用配对t检验,非正态分布资料采用非参数检验,相关分析采用直线相关分析方法.结果 8例COPD患者的吸气相阻抗和吸气相肺阻力的均值分别为(6.5±1.6)cm H2O·s-1·L-1和(9±5)cm H2O·s-1·L-1(相关系数为0.64,P<0.01),两者差值的中位数为-2.7(-5.7～0.7)cm H2O·s-1·L-1,一致性范围在(-10.6～4.9)cm H2O·s-1·L-1,吸气相肺阻力=-1.62+1.69吸气相阻抗(F=109.6,P<0.01).CPAP水平增高,△Xrs显著降低,显示为EFL的呼吸周期数显著减少,区分呼吸周期有或无EFL的△Xrs阈值为1.83 cm H2O·s-1·L-1,敏感度为94%,特异度为97%.结论 5 Hz强迫振荡吸气相阻抗可用于预测吸气相肺阻力,参照吸气相肺阻力设置无创通气的吸气相止压水平,能有效克服增高的肺阻力;△Xrs反映EFL程度,逐步增高CPAP或呼气末正压的水平,使△Xrs≤1.83 cm H2O·s-1·L-1,可消除绝大部分呼吸周期的EFL.     

Expiratory flow limitation detected by forced oscillation and negative expiratory pressure.

The within-breath change in reactance (Delta(rs)) measured by forced oscillation technique (FOT) at 5 Hz reliably detects expiratory flow limitation in chronic obstructive pulmonary disease (COPD). The present study compared this approach to the standard negative expiratory pressure (NEP) method. In total, 21 COPD patients were studied by applying both techniques to the same breath and in 15 patients the measurements were repeated after bronchodilator. For each patient and condition five NEP tests were performed and independently scored by three operators unaware of the FOT results. In 180 tests, FOT classified 53.3% as flow limited. On average, the operators scored 27.6% of tests flow limited and 47.6% non-flow limited, but could not score 24.8%. The methods disagreed in 7.9% of cases; in 78% of these the NEP scores differed between operators. Bronchodilation reduced NEP and DeltaX(rs) scores, with only the latter achieving significance. Averaging the operators' NEP scores, a threshold between 24.6-30.8% of tidal volume being flow limited by NEP produced 94% agreement between methods. In conclusion, when negative expiratory pressure and forced oscillation technique were both available they showed good agreement. As forced oscillation technique is automatic and can measure multiple breaths over long periods, it is suitable for monitoring expiratory flow limitation continuously and identifying patients' breathing close to the onset of expiratory flow limitation, where intermittent sampling may be unrepresentative.     

Expiratory resistive loading in patients with severe chronic air-flow limitation. An evaluation of ventilatory mechanics and compensatory responses

In order to estimate the extent of dynamic compression in patients with COPD who were flow-limited at rest, we measured tidal expiratory flows before and after application of small expiratory resistive loads (ERL). We sought also to evaluate the compensatory strategies available to such patients during ERL by measuring steady-state ventilatory responses. Nine patients with severe COPD (FEV1 +/- SE, 27 +/- 3% predicted) completed the study. Mean tidal flow-volume plots representing all breaths analyzed during 4 min of ERL (resistance, 8 cm H2O/L/s) and unloaded control (4 min) were compared at isoabsolute volume in each individual subject. In 6 subjects, ERL resulted in appreciable reduction of expiratory flows throughout the tidal volume (VT) when compared with volume-matched flows during control. In the remaining subjects, expiratory flows during loading and control coincided during part of the VT. In the group as a whole at 50, 30, and 10% of VT during ERL, when mouth pressure was increased by 3, 2.5, and 2 cm H2O, respectively, flow rates were significantly lower than volume-matched flows during control (delta V, = 0.10, 0.09 and 0.06 L/s, respectively). Minute ventilation was reduced significantly by ERL, but only small insignificant changes in breathing pattern parameters occurred. End-expiratory volume increased by 0.1 L +/- 0.02 (p less than 0.005). We conclude that the majority of patients with chronic air-flow limitation do not sustain significant dynamic compression at rest, and loading response to ERL in patients with COPD are attenuated when compared with those in normal subjects.     

Extrathoracic expiratory flow limitation in obesity and obstructive and restrictive disorders: effects of increasing negative expiratory pressure

BACKGROUND: The negative expiratory pressure (NEP) technique is used to detect intrathoracic expiratory flow limitation (EFL) in patients with respiratory disorders. Application of NEP may result in a sustained decrease of flow below control as a result of upper airway collapse, which may invalidate interpretation of the test. This response to NEP is common in patients with obstructive sleep apnea syndrome (OSAS). The prevalence of this phenomenon, however, has not been studied in healthy subjects and patients with obstructive and restrictive disorders without OSAS. PURPOSE: The purpose of this study was as follows: (1) to assess the effects of increasing NEP levels on upper airway patency, and (2) to determine the factors that predispose to intrathoracic flow limitation or upper airway collapse during NEP application in different postures in healthy nonobese and obese subjects, and in patients with obstructive and restrictive respiratory disorders. SUBJECTS: Fifty-six patients with obstructive airway disease (21 patients with COPD, 16 patients with simple chronic bronchitis, and 19 patients with asthma) were compared with 47 patients with restrictive respiratory disorders, 20 nonobese and healthy subjects, and 9 obese subjects (body mass index > 30) without a history of snoring or OSAS. METHODS: NEP at levels of 5 cm H(2)O, 10 cm H(2)O, and 15 cm H(2)O were applied at the mouth immediately after the onset of tidal expiration while seated and supine. Intrathoracic EFL was defined as no change in expiratory flow over any portion of the immediately preceding control breath. Upper airway collapse or narrowing was detected when flows decreased below those of the control breath. RESULTS: Ten patients (18%) with obstructive airway disease (7 patients with COPD) exhibited EFL at NEP of 5 cm H(2)O (4 patients were supine only, and 6 patients were both supine and sitting). No patient with restrictive disorders or healthy obese and nonobese subjects presented EFL at NEP of 5 cm H(2)O. In almost all subgroups, both seated and supine, subjects exhibited a transient decrease of flow below control immediately after the application of NEP in occasional breaths. As NEP increased, the number of subjects who exhibited this response in occasional breaths declined, while the number of subjects who displayed this pattern in all breaths increased. Conversely, there were very few subjects in each subgroup who exhibited a sustained decrease in flow below control in occasional breaths at NEP at 5 cm H(2)O, and only one healthy obese subject who displayed this response in all breaths in supine position only. CONCLUSIONS: In general, an increase in NEP resulted in only rare instances of sustained decrease in flow below control in all breaths. While transient decreases in flow exhibited immediately after the onset of NEP in all breaths are common and become more prevalent as NEP is increased beyond 5 cm H(2)O, there are only rare instances of sustained decrease in flow below control throughout expiration at all levels of NEP tested, indicating an appropriate upper airway dilator response that maintains patency. Thus, in subjects without OSAS, assessment of intrathoracic EFL with NEP is valid in almost all instances.     

Does expiratory flow limitation predict chronic dyspnoea in adults with cystic fibrosis?

Tidal expiratory flow limitation (EFL) may promote dynamic hyperinflation and contribute to chronic dyspnoea. The purpose of this study was to assess the contribution of EFL to chronic dyspnoea in adults with cystic fibrosis (CF). The presence of EFL was determined in 102 adults with stable CF (forced expiratory volume in one second (FEV1) 17.3-91.5% predicted) and 20 age-matched control subjects using the negative expiratory pressure technique. Measurements of inspiratory capacity (IC) and spirometry were performed, and chronic dyspnoea was evaluated using the modified Medical Research Council scale. EFL was present in 34 subjects (33%), with 18 subjects flow limited in the sitting position and 16 subjects flow limited only in the supine position. Flow limitation in the sitting position was associated with older age and lower FEV1 compared with flow-limited supine position and non-flow-limited subjects. A significant reduction in IC accompanied EFL in both the sitting and supine positions. Flow limitation in the sitting position was associated with significantly higher levels of chronic dyspnoea. Ordinal regression analysis indicated that EFL was the best predictor of chronic dyspnoea in a model that included FEV1 % pred. Expiratory flow limitation in cystic fibrosis is associated with reduced forced expiratory volume in one second, older age and dynamic hyperinflation. Expiratory flow limitation significantly contributes to chronic dyspnoea in cystic fibrosis.     

Colored 3-Dimensional Analyses of Respiratory Resistance and Reactance in COPD and Asthma

Background: The forced oscillation technique (FOT) is a noninvasive method with which to measure respiratory system resistance (Rrs) and reactance (Xrs) at a wide range of frequencies during breathing at rest in a short time. The purpose of this study was to assess the differences in Rrs and Xrs between patients with chronic obstructive pulmonary disease (COPD) and asthma using a new method of FOT with colored 3-dimensional visualization. Methods: Fifty-one patients with stable COPD and 49 patients with controlled or partly controlled asthma were enrolled. Whole-breath or within-breath changes of Rrs and Xrs were measured and compared between the diseases. Results: The colored 3-dimensional images clarified the complex oscillatory properties of the respiratory system. Whole-breath resistance (the difference in Rrs at 5 and 20 Hz) and reactance (Xrs at 5 Hz and resonant frequency), and within-breath changes in reactance (Xrs at 5 Hz and resonant frequency) discriminated between patients with COPD and asthma. In multivariate regression analyses, inspiratory-expiratory differences in Xrs at 5 Hz contributed significantly to the differentiation between COPD and asthma, independent of age, gender, body weight, and pulmonary function. Conclusion: This new method of FOT is useful in the differential diagnosis of COPD and asthma.     

Effect of heliox breathing on dynamic hyperinflation in COPD patients

BACKGROUND: and objective: Patients with COPD exhibit increased inspiratory work and dyspnea due to dynamic hyperinflation caused by expiratory flow limitation. Helium-oxygen mixtures (ie, heliox) have been used in treating these patients on the assumption that, by lowering airway resistance, they might be beneficial. METHODS: In 22 patients with COPD, the presence of expiratory flow limitation was assessed with patients in the sitting and supine positions using the negative expiratory pressure technique, and the effects of heliox (80% He, 20% O2) on breathing pattern, expiratory flow limitation, and dynamic hyperinflation, evaluated from the change in inspiratory capacity (IC), were measured at rest and were compared with those due to inhaled salbutamol. RESULTS: During air breathing, 13 patients experienced flow limitation while in the sitting position and 18 experienced flow limitation while in the supine position. Neither heliox nor salbutamol therapy changed the breathing pattern in any of the patients, regardless of posture and the presence or absence of expiratory flow limitation. However, in both positions IC increased significantly in most flow-limited patients after bronchodilator administration, but not after heliox administration. CONCLUSIONS: Since heliox had no effect on dynamic hyperinflation, the use of this gas mixture, which is costly and cumbersome, does not appear to be beneficial in stable patients with COPD breathing at rest.     

Effects of biphasic positive airway pressure in patients with chronic obstructive pulmonary disease.

Biphasic positive airway pressure (BiPAP) is a ventilatory mode in which two pressure levels (higher (Phigh) and lower (Plow)) acting as continuous positive airway pressure (CPAP) alternate at preset time intervals. BiPAP combines pressure-controlled ventilation with unrestricted spontaneous breathing. BiPAP has not yet been evaluated in patients with chronic obstructive pulmonary disease (COPD). Therefore, the effects of BiPAP (15 cmH2O Phigh and 5 cmH2O Plow) pressure support (PS; 15 cmH2O and positive end-expiratory pressure (PEEP) 5 cmH2O) and CPAP (5 cmH2O) on respiratory mechanics in COPD patients were compared. Twenty-one COPD patients were supported in randomized order with BiPAP, PS and CPAP. Pressure-time product (PTP), work of breathing (WOB), change in oesophageal pressure (deltaPoes), mouth occlusion pressure (P0.1), intrinsic PEEP (PEEPi), tension time index (TTI), respiratory frequency, and tidal volume (VT) were measured. During BiPAP, the COPD patients showed a significantly higher PTP, WOB, deltaPoes, P0.1, TTI and PEEPi than during PS. Comparing the Plow phases of BiPAP and CPAP, the breaths during the Plow phases of BiPAP had a lower VT and a greater WOB and PTP due to a higher PEEPi than on CPAP alone. In conclusion, biphasic positive airway pressure carries the risk of increased work of breathing in spontaneously breathing chronic obstructive pulmonary disease patients. Pressure support is superior for reducing their respiratory muscle effort.     

Dynamic hyperinflation and flow limitation during methacholine-induced bronchoconstriction in asthma.

Although persistent activation of the inspiratory muscles and narrowing of the glottic aperture during expiration have been indicated as relevant mechanisms leading to dynamic hyperinflation in acute asthma, expiratory flow limitation (EFL) has recently been proposed as a possible triggering factor for increasing endexpiratory lung volume (EELV). To establish whether the attainment of maximal flow rate during tidal expiration could elicit dynamic elevation of EELV, breathing pattern, change in EELV by measuring inspiratory capacity (IC) and occurrence of EFL by the negative expiratory pressure (NEP) method were monitored in 10 stable asthmatic subjects during methacholine-induced, progressive bronchoconstriction in seated position. Change in dyspnoea was scored using the Borg scale. At maximum response forced expiratory volume in one second (FEV1) fell on average by 45+/-2% (p<0.001 versus control), while IC decreased 29+/-2%, (by 0.89+/-0.07 L, (p<0.01 versus control)). Only 2 subjects exhibited EFL at the end of methacholine challenge. In 7 subjects EELV started to increase before the occurrence of EFL. Dyspnoea, which increased from 0.2+/-0.1 to 5.5+/-1.0 (Borg scale) at maximum response (p<0.001), was significantly related to the level of bronchoconstriction as assessed by change in (delta)FEV1 (r=0.72; p<0.001) and to dynamic hyperinflation as measured by deltaIC (r=0.50; p<0.001). However, for both deltaFEV1 and deltaIC the slope of the relationship with increasing dyspnoea was highly variable among the subjects. It is concluded that in acute methacholine-induced bronchoconstriction, dynamic hyperinflation may occur in the absence of expiratory flow limitation and that expiratory flow limitation does not represent the triggering factor to generate dynamic hyperinflation. In these circumstances, dyspnoea appears to be related to the increase in end-expiratory lung volume and not to the onset of expiratory flow limitation.     

Exercise-induced flow limitation, dynamic hyperinflation and exercise capacity in patients with bronchial asthma.

It is known that, in stable asthmatics at rest, tidal expiratory flow limitation (EFL) and dynamic hyperinflation (DH) are seldom present. This study investigated whether stable asthmatics develop tidal EFL and DH during exercise with concurrent limitation of maximal exercise work rate (WRmax). A total of 20 asthmatics in a stable condition and aged 32+/-13 yrs (mean+/-SD) with a forced expiratory volume in one second (FEV1) of 101+/-21% of the predicted value were studied. Only three patients exhibited an FEV1 below the normal limits. On a first visit, patients performed a symptom-limited incremental (20 W.min(-1)) bicycle exercise test. On the second visit, the occurrence of EFL (using the negative expiratory pressure technique) and DH (via reduction in inspiratory capacity) were assessed at rest and when cycling at 33, 66 and 90% of their predetermined WRmax. FEV1 was measured to detect exercise-induced asthma, 5 and 15 min after stopping exercise at 90% WRmax. Only one patient showed EFL at rest, whereas 13 showed EFL and DH during exercise. In these 13 asthmatics, exercise capacity was significantly reduced (WRmax 75+/-9% pred) compared to the seven non-EFL patients (WRmax 95+/-13% pred). Moreover, a significant correlation of WRmax (% pred) to the change in inspiratory capacity (percentage of resting value) from rest to 90% WRmax was found. Tidal EFL during exercise was not associated with exercise-induced asthma, which was detected in only three patients. In conclusion, tidal expiratory flow limitation and dynamic hyperinflation during exercise are common in stable asthmatics with normal spirometric results and without exercise-induced asthma, and may contribute to reduction in exercise capacity.     

呼气相气道内负压法检测呼气流速受限在慢性阻塞性肺疾病中的应用

目的探讨慢性阻塞性肺疾病(COPD)患者呼气流速受限(EFL)与呼吸困难严重程度的相关性,并观察吸入支气管扩张剂对 COPD 患者 EFL 的影响。方法采用呼气相气道内负压法(NEP)检测33例 COPD 患者支气管扩张试验前、后(吸入沙丁胺醇400μg)EFL 情况,其中男31例,女2例,年龄46～78岁,平均年龄(63±8)岁。结果 33例 COPD 患者中23例(70%)出现 EFL,其中11例(33%)仅仰卧位出现 EFL,12例(36%)仰卧位及坐位均出现 EFL。无 EFL 患者与 EFL 患者第一秒用力呼气容积占预计值百分比(FEV_1占预计值%)分别为(66±16)%和(31±10)%,差异有统计学意义(t=7.601、P<0.01),仰卧位及坐位均出现 EFL 患者的 FEV_1占预计值%最低[(24±7)%]。3分法和5分法 EFL 均与 FEV_1呈显著负相关(r=-0.836和-0.818,P 均<0.01)。3分法和5分法 EFL 均与医学研究委员会(MRC)推荐的呼吸困难严重程度分级评分标准(简称 MRC 呼吸困难评分)呈显著正相关(r=0.903和0.912,P均<0.01)。多元回归分析结果显示,5分法 EFL 和FEV_1对 MRC 呼吸困难评分的预测性均有统计学意义(标准化偏回归系数分别为0.679、-0.265,P分别为<0.01、0.029),但5分法 EFL 比 FEV_1对 MRC 呼吸困难评分的预测性更强。23例吸入沙丁胺醇前存在 EFL 患者,吸入后全部患者 EFL 仍然存在。结论与 FEV_1比较,EFL 对 COPD 患者呼吸困难严重程度预测性更强,可作为评价 COPD 患者呼吸困难严重程度更可靠的客观指标。COPD 患者的 EFL 不能被吸入支气管扩张剂逆转,即表现为 EFL 的不可逆性。     

A new method of negative expiratory pressure test analysis detecting upper airway flow limitation to reveal obstructive sleep apnea

BACKGROUND: Expiratory flow limitation (EFL) by negative expiratory pressure (NEP) testing, quantified as the expiratory flow-limited part of the flow-volume curve, may be influenced by airway obstruction of intrathoracic and extrathoracic origins. NEP application during tidal expiration immediately determines a rise in expiratory flow (V) followed by a short-lasting V drop (deltaV), reflecting upper airway collapsibility. PURPOSES: This study investigated if a new NEP test analysis on the transient expiratory DeltaV after NEP application for detection of upper airway V limitation is able to identify obstructive sleep apnea (OSA) subjects and its severity. METHODS: Thirty-seven male subjects (mean +/- SD age, 46 +/- 11 years; mean body mass index [BMI], 34 +/- 7 kg/m2) with suspected OSA and with normal spirometric values underwent nocturnal polysomnography and diurnal NEP testing at - 5 cm H2O and - 10 cm H2O in sitting and supine positions. RESULTS: deltaV (percentage of the peak V [%Vpeak]) was better correlated to apnea-hypopnea index (AHI) than the EFL measured as V, during NEP application, equal or inferior to the corresponding V during control (EFL), and expressed as percentage of control tidal volume (%Vt). AHI values were always high (> 44 events/h) in subjects with BMI > 35 kg/m2, while they were very scattered (range, 0.5 to 103.5 events/h) in subjects with BMI < 35 kg/m2. In these subjects, AHI still correlated to deltaV (%Vpeak) in both sitting and supine positions at both NEP pressures. CONCLUSIONS: OSA severity is better related to deltaV (%Vpeak) than EFL (%Vt) in subjects referred to sleep centers. DeltaV (%Vpeak) can be a marker of OSA, and it is particularly useful in nonseverely obese subjects.     

Differences in spontaneous breathing pattern and mechanics in patients with severe COPD recovering from acute exacerbation.

The aims of this study were to assess spontaneous breathing patterns in patients with chronic obstructive pulmonary disease (COPD) recovering from acute exacerbation and to assess the relationship between different breathing patterns and clinical and functional parameters of respiratory impairment. Thirty-four COPD patients underwent assessment of lung function tests, arterial blood gases, haemodynamics, breathing pattern (respiratory frequency (fR), tidal volume (VT), inspiratory and expiratory time (tI and tE), duty cycle (tI/ttot), VT/tI) and mechanics (oesophageal pressure (Poes), work of breathing (WOB), pressure-time product and index, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn)). According to the presence (group 1) or absence (group 2) of Poes swings during the expiratory phase (premature inspiration), 20 (59%) patients were included in group 1 and 14 (41%) in group 2. Premature inspirations were observed 4.5+/-6.4 times x min(-1) (range 1-31), i.e. 20+/-21% (3.7-100%) of total fR calculated from VT tracings. In group 1 the coefficient of variation in VT, tE, tI/ttot, PEEPi,dyn, Poes and WOB of the eight consecutive breaths immediately preceding the premature inspiration was greater than that of eight consecutive breaths in group 2. There were no significant differences in the assessed parameters between the two groups in the overall population, whereas patients with chronic hypoxaemia in group 1 showed a more severe impairment in clinical conditions, mechanics and lung function than hypoxaemic patients in group 2. In spontaneously breathing patients with chronic obstructive pulmonary disease recovering from an acute exacerbation, detectable activity of inspiratory muscles during expiration was found in more than half of the cases. This phenomenon was not associated with any significant differences in anthropometric, demographic, physiological or clinical characteristics.     

Comparison of respiratory system impedance in asthma and COPD: A prospective observational study

Background and objective

A single assessment of within‐breath variations of respiratory system reactance (Xrs) at 5 Hz (ΔX5) measured by the forced oscillation technique (FOT) has been reported to be useful for the detection of pathophysiological changes in chronic obstructive pulmonary disease (COPD) and asthma. We examined longitudinal changes in respiratory system resistance (Rrs) and Xrs during tidal breathing between stable asthma and COPD patients in order to clarify the features of changes of respiratory system impedance and airflow limitation for these conditions.

Methods

Between April 2013 and September 2013, outpatients with a COPD or asthma diagnosis were recruited. We examined forced expiratory volume in 1 s (FEV₁) and FOT every 6 months until September 2015. Annual changes were estimated from the linear regression curve slope.

Results

We included 57 and 93 subjects with COPD and asthma, respectively. The median follow‐up period was 26 months (range: 24–29 months). Within‐breath analysis showed that the difference between mean Rrs at 5 Hz and 20 Hz was significantly lower, and ΔX5 more negative, in COPD than in asthma patients. With regard to annual changes, only ΔX5 was significantly different, more negative, in COPD than in asthma patients. Comparing between COPD subjects of Global Initiative Chronic Obstructive Lung Disease (GOLD) stage I/II and those with asthma, there were no significant differences in respiratory system impedance at enrolment, while annual change in ΔX5 was significantly more negative in mild COPD than in asthma patients.

Conclusion

ΔX5 may be useful for long‐term assessment of airflow limitation in COPD.

     

Does negative expiratory pressure (NEP) during spontaneous breathing predict respiratory impairment in elderly?

OBJECTIVE: The purpose of this study is to assess whether expiratory flow limitation (FL), as measured by applying a negative pressure at the mouth during tidal expiration, can evaluate the respiratory impairment in elderly patients. METHODS: The study was carried out in 67 consecutive elderly inpatients (24 men and 43 women). Negative expiratory pressure (NEP) of -5 (NEP 5) and -10 (NEP 10) cm H2O were applied during spontaneous tidal expiration. According to the results of the NEP technique, the patients were stratified in two categories: not flow limited and flow limited. We realized then classic forced expiratory manoeuvres (FEV1, FVC) and clinical evaluation of dyspnea (NYHA). According to the values of the lung function data, elderly patients were then divided in 3 groups (normal, obstructive, restrictive). RESULTS: The sensitivity, the specificity, the positive and negative predictive values for the diagnosis of obstructive syndrome by the presence of flow limitation during NEP 5 were 53, 74, 45, 79% respectively and 58, 83, 58, 83% respectively during NEP 10. These findings show that the correlation between FL obtained by the NEP technique during spontaneous breathing and spirometry is not very good despite the fact that both were well correlated with dyspnea score. CONCLUSIONS: In clinical practice, faced with an elderly dyspneic patient unable to perform maximal expiratory manoeuvres, the evaluation of flow limitation by NEP technique seems nor to be reliable to predict an obstructive functional impairment nor to be able to explain the origin of his dyspnea.     

A portable forced oscillation device for respiratory home monitoring.

The increase in the prevalence of chronic respiratory diseases has resulted in a rise in health services provided at home. The forced oscillation technique (FOT) proves to be a useful tool when it is desired to assess lung function noninvasively, and particularly for patients in whom spirometry cannot be applied. As no portable FOT device is currently available, the aim of this study was to design and test a portable FOT system for ambulatory and home care applications. The system devised is based on a microprocessor, which allows online computation of respiratory resistance (Rrs) and reactance (Xrs) and reliability indices. The portable device was compared with a conventional FOT system by using signals from 14 patients with chronic respiratory disease. This device has the same computation capabilities and flexibility as conventional FOT systems and meets the requirements for home application. Rrs (14.2 +/- 6.0 cmH2O x s x L(-1), mean +/- SD) and Xrs (-5.3 +/- 2.7 cmH2O x s x L(-1)) measured at 5 Hz by the portable system virtually coincided with those computed with the reference conventional FOT system: mean differences +/-SD were 0.074 +/- 0.025 and 0.005 +/- 0.009 cmH2O x s x L(-1), respectively. This portable forced oscillation technique device could be a useful tool for monitoring respiratory mechanics in ambulatory and home care applications.     

Does mechanical injury of the peripheral airways play a role in the genesis of COPD in smokers?

In the present account it is proposed that in smokers the transition from peripheral airway disease to COPD is characterized by three sequential stages: Stage I, during which the closing volume eventually exceeds the functional residual capacity; Stage II, during which tidal expiratory flow limitation (EFL) is eventually exhibited; and Stage III, during which dynamic hyperinflation progressively increases leading to dyspnea and exercise limitation, which may be considered as markers of overt disease. Presence of airway closure (Stage I) and EFL (Stage II) in the tidal volume range may promote peripheral airway injury and accelerate the abnormalities of lung function. It is such injury that may determine which smoker is destined to develop COPD.     

不同指标对老年严重慢性阻塞性肺疾病患者吸入支气管舒张剂疗效的评价

目的 对评价严重慢性阻塞性肺疾病(COPD)患者吸入支气管舒张剂疗效的3种指标进行比较. 方法 吸人复方异丙托溴胺溶液前后对18例稳定期严重COPD患者行肺通气功能和肺容量测定,并采用呼气负压技术同步检测呼气流速受限(EFL). 结果 与安慰剂比较,吸入支气管舒张剂后COPD患者第1秒用力呼气容积占预计值(FEV1)百分比、用力肺活量占预计值(FVC)百分比、深吸气量占预计值(IC)百分比显著改善,残气量占预计值(RV)百分比和功能残气量占预计值(FRC)百分比显著降低,肺总量占预计值(TLC)百分比无显著改变;Borg呼吸困难评分显著降低;5分法EFL评分无显著改变,呼吸方式无显著改变.IC、FEV,和5分法EFL评分的平均改善率分别是(20.42±15.02)%、(10.98±7.28)%和(5.15±11.24).△IC与ABorg呈负相关(r=0.732,P<0.05),AFEVl与ABorg相关关系无统计学意义(r=0.343,P>0.05).应用受试者工作特征曲线方法分析3种不同指标诊断呼吸困难的价值,结果表明,IC、FEV1和5分法EFL评分的曲线下面积分别为0.868、0.681和0.557. 结论 与FEV1相比,IC评价严莺COPD患者支气管舒张剂疗效更为灵敏和准确,5分法EFL评分不宜作为评价严重COPD患者吸人支气管舒张剂疗效的指标.     

Negative expiratory pressure test: a new, simple method to identify patients at risk for obstructive sleep apnea

The objective of this article was to describe a new method for assessing expiratory flow limitation during spontaneous breathing, using the negative expiratory pressure test to identify patients at risk for obstructive sleep apnea. Upper airway collapsibility is evaluated by measuring decreases in flow and in expired volume in the first 0.2 seconds after negative expiratory pressure application at 10 cmH?O. The negative expiratory pressure test is easily applied and could be adopted for the evaluation of expiratory flow limitation caused by upper airway obstruction in patients with obstructive sleep apnea.