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.     

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.     

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.     

Tidal Expiratory Flow Limitation at Rest as a Functional Marker of Pulmonary Emphysema in Moderate-to-Severe COPD

Background: Tidal expiratory flow limitation (EFL) is a step of paramount importance in the functional decline in COPD. Among mechanisms contributing to EFL, loss of airway-parenchymal interdependence could mostly be involved. Aim: To assess if EFL is a functional marker more frequently linked to prevalent pulmonary emphysema rather than to prevalent chronic bronchiolitis in COPD patients with moderate-to-severe airflow obstruction. Methods: Forty consecutive stable COPD patients with FEV₁ between 59 and 30% of predicted were functionally evaluated by measuring spirometry, maximal flow-volume curve and lung diffusion capacity (DL_CO) and coefficient of diffusion (K_CO). EFL was assessed by the negative expiratory pressure (NEP) method both in sitting and supine position. Chronic dyspnea was also scored by modified Medical Research Council (mMRC) scale. Results: In sitting position 13 patients (33%) were flow limited (FL) and 27 were non-flow limited (NFL). Only FEV₁/FVC, FEV₁ and MEF_25–75% were different between FL and NFL patients (p < 0.01). In supine position, however, among NFL patients in sitting position those who developed EFL, had significantly lower values of DL_CO and K_CO (p < 0.05) and higher mMRC score (p < 0.01), but similar values of FEV₁ as compared to those who did not have EFL. Conclusions: In COPD EFL in sitting position is highly dependent by the severity of airflow obstruction. In contrast, the occurrence of EFL in supine position is associated with worse DL_CO and K_CO and greater chronic dyspnea, reflecting a prevalent emphysematous phenotype in moderate-to-severe COPD patients.     

Orthopnea and tidal expiratory flow limitation in patients with stable COPD

BACKGROUND: Orthopnea is a common feature in COPD patients, although its nature is poorly understood. OBJECTIVE: To study the role of tidal expiratory flow limitation (FL) in the genesis of orthopnea in patients with stable COPD. MEASUREMENTS: Tidal FL was assessed in 117 ambulatory COPD patients in sitting and supine positions using the negative expiratory pressure method. The presence or absence of orthopnea was also noted. RESULTS AND CONCLUSIONS: In patients with stable COPD with tidal expiratory FL in seated and/or supine position, there is a high prevalence of orthopnea, which probably results in part from increased inspiratory efforts due to dynamic pulmonary hyperinflation and the concomitant increase in inspiratory threshold load due to intrinsic positive end-expiratory pressure. Increased airway resistance in supine position due to lower end-expiratory lung volume probably also plays a role in the genesis of orthopnea.     

Negative Expiratory Pressure (NEP) Parameters Can Predict Obstructive Sleep Apnea Syndrome in Snoring Patients

The objective of this study was to assess whether parameters of the negative expiratory pressure (NEP) technique are able to detect obstructive sleep apnea syndrome (OSAS) in snoring patients. A cross-sectional study included 42 OSAS patients diagnosed by polysomnography (PSG), 34 simple snorers, and 32 healthy subjects. Lung function was measured by using a plethysmograph and the NEP technique was performed with the patient in the seated and supine positions in a random order. The depression was fixed to 5 cmH(2)O. All patients had normal forced expiratory flow/volume loops. Apneic patients had lower Dflow in both positions with a number of oscillations on the expiratory curve obtained with NEP and an expiratory flow limitation (EFL) in the supine position higher than that of other groups (p < 0.05). Changing from the sitting to the supine position raised the EFL of the three groups, with a significant decrease in Dflow and an increase in the number of oscillations in snoring and OSAS patients (p < 0.05). The analysis of variance showed that only the number of oscillations was significantly different between apneic and snoring patients. NEP constitutes a simple and useful tool for the screening OSAS by EFL, especially the number of oscillations obtained with NEP.     

呼吸疾病研究所呼气相气道内负压法检测呼气流速受限在支气管哮喘患者中的应用

目的 探讨支气管哮喘(简称哮喘)患者呼气流速受限(EFL)与呼吸困难严重程度的相关性,观察吸入支气管扩张剂对哮喘患者EFL的影响.方法 采用呼气相气道内负压法(NEP)检测65例哮喘患者支气管扩张试验前、后(吸入沙丁胺醇400 μg)EFL情况.结果 65例哮喘患者中有26例(40%)出现EFL,其中11 例仅仰卧位时出现,15例仰卧位及坐位均出现.EFL和无EFL者(N-EFL)第一秒用力呼气容积占预计值百分比(FEV1占预计值%)分别为(52±15)%、( 77±18)%,两组比较差异有统计学意义(t＝5.822,P＜0.01).仅仰卧位有EFL(S-EFL)者和仰卧位、坐位均有EFL(SS-EFL)者FEV1占预计值%分别为(64±10)%、(43±12)%,两组比较差异有统计学意义(t值分别为2.283、6.694,P分别＜0.01、＜0.05).3分法和5分法EFL均与FEV1占预计值%呈负相关(r值分别为-0.637、-0.630,P均＜0.01).第一秒用力呼气容积(FEV1)与加拿大医学研究委员会推荐的呼吸困难严重程度分级标准(MRC评分)呈负相关(r=-0.501,P＜0.01),3分法和5分法EFL均与MRC评分呈正相关(r值分别为0.627、0.636,P均＜0.01).17例FEV1占预计值%＜70%并存在EFL的患者吸入沙丁胺醇后,9例EFL完全消失,5例从SS-EFL变为S-EFL,吸入沙丁胺醇后3分法和5分法EFL评分均较吸入前差异有统计学意义(t值分别为6.769、6.010,P均＜0.01).结论 与FEV1比较,EFL与哮喘患者呼吸困难严重程度相关性更强,可作为评价患者呼吸困难严重程度更可靠的客观指标.哮喘患者EFL可被吸入支气管扩张剂逆转,即表现为可逆性EFL.     

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。     

Expiratory flow limitation and intrinsic positive end-expiratory pressure at zero positive end-expiratory pressure in patients with adult respiratory distress syndrome

It has been suggested that in patients with adult respiratory distress syndrome (ARDS), intrinsic positive end-expiratory pressure (PEEPi) is generated by a disproportionate increase in expiratory flow resistance. Using the negative expiratory pressure (NEP) technique, we assessed whether expiratory flow limitation (EFL) and PEEPi were present at zero PEEP in 10 semirecumbent, mechanically ventilated ARDS patients. Because bronchodilators may decrease airway resistance, we also investigated the effect of nebulized salbutamol on EFL, PEEPi, and respiratory mechanics in these patients, and in seven patients we measured the latter variables in the supine position as well. In the semirecumbent position, eight of the 10 ARDS patients exhibited tidal EFL, ranging from 5 to 37% of the control tidal volume (VT), whereas PEEPi was present in all 10 subjects, ranging from 0.4 cm H(2)O to 7.7 cm H(2)O. The onset of EFL was heralded by a distinct inflection point on the expiratory flow-volume curve, which probably reflected small-airway closure. Administration of salbutamol had no statistically significant effect on PEEPi, EFL (as %VT), or respiratory mechanics. EFL (%VT) and PEEPi were significantly higher in the supine position than in the semirecumbent position, whereas the other respiratory variables did not change. Our results suggest that in the absence of externally applied PEEP, most ARDS patients exhibit EFL associated with small-airway closure and a concomitant PEEPi.     

对比呼气负压与传统方法检测慢性阻塞性肺疾病患者呼气气流受限

目的 对比呼气负压(NEP)与传统方法 检测慢性阻塞性肺疾病(COPD)患者呼气气流受限(EFL).方法 应用NEP与传统方法 (层流型流最计)检测72例COPD缓解期患者EFL;对20例不能完成传统测试的患者应用NEP检测其EFL;对比两种方法 的检测结果 .结果 72例COPD患者应用NEP 54例(75%)检测到EFL.第1秒用力呼气容积(FEV_1)占预计值百分比EFL评分2分者为(46.92±12.74)%,3分者为(33.35±8.96)%,显著低于EFL评分1分者[(63.60±16.65)%].ROC曲线分析NEP曲线下面积(AUC)为0.903,层流型流量计AUC为0.761.20例不能完成传统测试的患者均能耐受NEP测试,19例检测到EFL.结论 应用NEP检测COPD患者EFL,比应用传统方法 检测更能准确反映COPD患者呼吸困难的严重程度;NEP操作简单、无需患者主动配合,可在不能完成传统测试的患者中应用.     

Orthopnea and tidal expiratory flow limitation in chronic heart failure

BACKGROUND: Tidal expiratory flow limitation (FL) is common in patients with acute left heart failure and contributes significantly to orthopnea. Whether tidal FL exists in patients with chronic heart failure (CHF) remains to be determined. PURPOSES: To measure tidal FL and respiratory function in CHF patients and their relationships to orthopnea. METHODS: In 20 CHF patients (mean [+/- SD] ejection fraction, 23 +/- 8%; mean systolic pulmonary artery pressure [sPAP], 46 +/- 18 mm Hg; mean age, 59 +/- 11 years) and 20 control subjects who were matched for age and gender, we assessed FL, Borg score, spirometry, maximal inspiratory pressure (Pimax), mouth occlusion pressure 100 ms after the onset of inspiratory effort (P(0.1)), and breathing pattern in both the sitting and supine positions. The Medical Research Council score and orthopnea score were also determined. RESULTS: In the sitting position, tidal FL was absent in all patients and healthy subjects. In CHF patients, Pimax was reduced, and ventilation and P(0.1)/Pimax ratio was increased relative to those of control subjects. In the supine position, 12 CHF patients had FL and 18 CHF patients claimed orthopnea with a mean Borg score increasing from 0.5 +/- 0.7 in the sitting position to 2.7 +/- 1.5 in the supine position in CHF patients. In contrast, orthopnea was absent in all control subjects. The FL patients were older than the non-FL patients (mean age, 63 +/- 8 vs 53 +/- 12 years, respectively; p < 0.03). In shifting from the seated to the supine position, the P(0.1)/Pimax ratio and the effective inspiratory impedance increased more in CHF patients than in control subjects. The best predictors of orthopnea in CHF patients were sPAP, supine Pimax, and the percentage change in inspiratory capacity (IC) from the seated to the supine position (r(2) = 0.64; p < 0.001). CONCLUSIONS: In sitting CHF patients, tidal FL is absent but is common supine. Supine FL, together with increased respiratory impedance and decreased inspiratory muscle force, can elicit orthopnea, whom independent indicators are sPAP, supine Pimax and change in IC percentage.     

Expiratory flow limitation and orthopnea in massively obese subjects

BACKGROUND: Morbidly obese subjects, who often complain about breathlessness when lying down, breathe at low lung volume with a reduced expiratory reserve volume (ERV). Therefore, during tidal breathing the expiratory flow reserve is decreased, promoting expiratory flow limitation (EFL), which is more likely to occur in the supine position, when the relaxation volume of the respiratory system, and hence the functional residual capacity (FRC), decrease because of the gravitational effect of the abdominal contents. PURPOSE: The aim of the study was to assess EFL and orthopnea in massively obese subjects and to evaluate whether orthopnea was associated with the development of supine EFL. METHODS: In 46 healthy obese subjects (18 men) with a mean (+/- SD) age of 44 +/- 11 years and a mean body mass index (BMI) of 51 +/- 9 kg/m(2), we assessed EFL in both the seated and the supine positions by the negative expiratory pressure method and assessed postural changes in FRC by measuring the variations in the inspiratory capacity (IC) with recumbency. Simultaneously, dyspnea was evaluated in either position using the Borg scale dyspnea index (BSDI) to determine the presence of orthopnea, which was defined as any increase of the BSDI in the supine position. RESULTS: Partial EFL was detected in 22% and 59%, respectively, of the overall population in seated and supine position. The mean increase in the supine IC amounted to 120 +/- 200 mL (4.1 +/- 6.4%), indicating a limited decrease in FRC with recumbency in these subjects. Orthopnea, although mild (mean BSDI, 1.7 +/- 1.3), was claimed by 20 subjects, and in 15 of them EFL occurred or worsened in the supine position. Orthopnea was associated with lower values of seated ERV (p < 0.05) and was marginally related to supine EFL values (p = 0.07). No significant effect of age, BMI, obstructive sleep apnea-hypopnea syndrome, FEV(1), and forced expiratory flow at 75% of vital capacity was found on either orthopnea or EFL. CONCLUSION: In morbidly obese subjects, EFL and dyspnea frequently occur with the subject in the supine position, and both supine EFL and low-seated ERV values are related to orthopnea, suggesting that dynamic pulmonary hyperinflation and intrinsic positive end-expiratory pressure may be partly responsible for orthopnea in massively obese subjects.     

Changes in lung function and tidal airflow patterns after increasing extrathoracic airway resistance

OBJECTIVE: The aim of this study was to determine what changes occur in previously described tidal expiratory flow patterns when extrathoracic resistance is added. METHODOLOGY: A total of 16 subjects with normal lung function and 15 patients with chronic COPD, were studied. The following measurements were made before and after the addition of an extrathoracic expiratory resistance (EER; 0.89 kPa/L s at a flow of 0.5 L/s) during uncoached tidal breathing: expiratory time (tE), frequency (f), expiratory time to maximum flow/total expiratory time (tPTEF/tE), tidal maximum expiratory flow (PEF(TIDAL)), and time constant of the respiratory system calculated from the passive portion of tidal expiration (trs(TIDAL)). Post peak profiles were categorized as convex, linear or concave and time for flow to fall to 80% and 20% of maximum (t80 and t20) were measured. RESULTS: Tidal indices tE, f and PEF(TIDAL), were similar in the two groups, but tPTEF/tE was greater and trs(TIDAL) was less in the normal subjects than in the COPD patients. Addition of EER in both groups caused PEF(TIDAL) to decrease and trs(TIDAL), t80 and the percentage of convex profiles to increase. tPTEF/tE increased in the COPD patients but was unchanged in the control group. CONCLUSION: After addition of EER during tidal breathing, expiratory flow in COPD patients resembled that seen in normal subjects.     

Expiratory flow limitation in awake sleep-disordered breathing subjects.

Increased upper airways (UA) collapsibility has been implicated in the pathogeny of sleep-disordered breathing (SDB). An increased UA instability during expiration has recently been shown in healthy subjects. The present study assessed UA collapsibility in SDB patients by applying negative pressure during expiration. Full-night polysomnography was performed in 16 subjects (all snorers) with a wide range of SDB, and in six healthy control subjects. Physical examination, spirometry, and maximal inspiratory and expiratory flow rates were within normal limits for all 22 subjects. Negative expiratory pressure (NEP) (-5 cmH2O) was applied during quiet breathing in seated and supine position. Flow limitation (FL) during NEP was expressed as the percentage of tidal volume during which expiratory flow was less than or equal to the flow recorded during quiet breathing (%FL). The mean desaturation index (DI) of the 16 subjects was 27.3+/-26.4 (+/-sD) and the average FL in supine position was 38.4+/-37.9%. A close correlation between %FL supine during wakefulness and DI during sleep (r=0.84, p<0.001) was found. All obstructive sleep apnoea subjects had >30%FL supine. There was no FL in the six control subjects. In conclusion, negative expiratory pressure application during expiration appears to be a useful, noninvasive method for the evaluation of subjects with sleep-disordered breathing. Present results suggest that upper airway collapsibility can be detected in these subjects during wakefulness.     

Detection of expiratory flow limitation by manual compression of the abdominal wall

We have assessed a new method, manual compression of the abdominal wall (MCA) during expiration, in the detection of expiratory flow limitation. Twelve stable patients with chronic obstructive pulmonary disease (COPD) and five normal subjects were studied during spontaneous breathing in the supine and seated posture. MCA was performed during expiration with one hand at the umbilical level and we measured flow, volume, pleural (Ppl) and gastric (Pga) pressures and abdominal anteroposterior (AP) diameter at the umbilical level with magnetometers. No increase in expiratory flow during MCA relative to the preceding breath despite associated increases in pressures was considered as indicating expiratory flow limitation. In seven additional patients with increased upper airway collapsibility (obstructive sleep apnea syndrome [OSAS]), MCA was compared with negative expiratory pressure (NEP). In normal seated subjects, MCA was associated with a decrease in abdominal AP dimension (mean +/- SD: -27 +/- 6%), an increase in Pga (14.7 +/- 7.4 cm H(2)O) and Ppl (6.2 +/- 2.2 cm H(2)O), and an increase in expiratory flow. MCA caused similar changes in abdominal AP dimension and pressures in seated patients with COPD but six of them (50%), including four patients with FEV(1) less than 1 L, had no increase in expiratory flow. In the supine posture, MCA always increased expiratory flow in normal subjects but four additional patients with COPD showed evidence of flow limitation. MCA invariably increased expiratory flow in patients with OSAS whereas the NEP method suggested flow limitation in some cases. We conclude that MCA is a very simple method that allows detection of flow limitation in different positions.     

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.     

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.     

Tidal expiratory flow limitation, dyspnoea and exercise capacity in patients with bilateral bronchiectasis.

In this study the authors investigated whether expiratory flow limitation (FL) is present during tidal breathing in patients with bilateral bronchiectasis (BB) and whether it is related to the severity of chronic dyspnoea (Medical Research Council (MRC) dyspnoea scale), exercise capacity (maximal mechanical power output (WRmax)) and severity of the disease, as assessed by high-resolution computed tomography (HRCT) scoring. Lung function, MRC dyspnoea, HRCT score, WRmax and FL were assessed in 23 stable caucasian patients (six males) aged 56 +/- 17 yrs. FL was assessed at rest both in seated and supine positions. To detect FL, the negative expiratory pressure (NEP) technique was used. The degree of FL was rated using a five-point FL score. WRmax was measured using a cyclo-ergometer. According to the NEP technique, five patients were FL during resting breathing when supine but not seated, four were FL both seated and supine, and 14 were NFL both seated and supine. Furthermore, it was shown that: 1) in stable BB patients FL during resting breathing is common, especially in the supine position; 2) the degree of MRC dyspnoea is closely related to the five-point FL score; 3) WRmax (% pred) is more closely correlated with the MRC dyspnoea score than with the five-point FL score; and 4) HRCT score is closely related to forced expiratory volume in one second % pred but not five-point FL score. In conclusion, flow limitation is common at rest in sitting and supine positions in patients with bilateral bronchiectasis. Flow limitation and reduced exercise capacity are both associated with more severe dyspnoea. Finally, high-resolution computed tomography scoring correlates best with forced expiratory volume in one second.     

Detection of expiratory flow limitation in COPD using the forced oscillation technique.

Expiratory flow limitation (EFL) during tidal breathing is a major determinant of dynamic hyperinflation and exercise limitation in chronic obstructive pulmonary disease (COPD). Current methods of detecting this are either invasive or unsuited to following changes breath-by-breath. It was hypothesised that tidal flow limitation would substantially reduce the total respiratory system reactance (Xrs) during expiration, and that this reduction could be used to reliably detect if EFL was present. To test this, 5-Hz forced oscillations were applied at the mouth in seven healthy subjects and 15 COPD patients (mean +/- sD forced expiratory volume in one second was 36.8 +/- 11.5% predicted) during quiet breathing. COPD breaths were analysed (n=206) and classified as flow-limited if flow decreased as alveolar pressure increased, indeterminate if flow decreased at constant alveolar pressure, or nonflow-limited. Of these, 85 breaths were flow-limited, 80 were not and 41 were indeterminate. Among other indices, mean inspiratory minus mean expiratory Xrs (deltaXrs) and minimum expiratory Xrs (Xexp,min) identified flow-limited breaths with 100% specificity and sensitivity using a threshold between 2.53-3.12 cmH2O x s x L(-1) (deltaXrs) and -7.38- -6.76 cmH2O x s x L(-1) (Xexp,min) representing 6.0% and 3.9% of the total range of values respectively. No flow-limited breaths were seen in the normal subjects by either method. Within-breath respiratory system reactance provides an accurate, reliable and noninvasive technique to detect expiratory flow limitation in patients with chronic obstructive pulmonary disease.     

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.