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Methods for Assessing Expiratory Flow Limitation during Tidal Breathing in COPD Patients  [PDF]
Nickolaos G. Koulouris,Georgios Kaltsakas,Anastasios F. Palamidas,Sofia-Antiopi Gennimata
Pulmonary Medicine , 2012, DOI: 10.1155/2012/234145
Abstract: Patients with severe COPD often exhale along the same flow-volume curve during quite breathing as during forced expiratory vital capacity manoeuvre, and this has been taken as indicating expiratory flow limitation at rest ( E F L T ). Therefore, E F L T , namely, attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. E F L T leads to small airway injury and promotes dynamic pulmonary hyperinflation with concurrent dyspnoea and exercise limitation. In fact, E F L T occurs commonly in COPD patients (mainly in GOLD III and IV stage) in whom the latter symptoms are common. The existing up-to-date physiological methods for assessing expiratory flow limitation ( E F L T ) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure (NEP) has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, non invasive, most practical, and accurate new technique. 1. Introduction Some experts use the term chronic airflow limitation as a synonym for chronic obstructive pulmonary disease (COPD) to indicate the reduction in maximum expiratory flow that occurs in this disease (and indeed in other pulmonary diseases). Patients with severe COPD often exhale along the same flow-volume curve during quite breathing as during forced expiratory vital capacity manoeuvre, and this has been taken as indicating flow limitation at rest ( E F L T ). Consequently, the term tidal expiratory flow limitation ( E F L T ) is used to indicate that maximal expiratory flow is achieved during tidal breathing at rest or during exercise. This is characteristic of intrathoracic flow obstruction. The former term does not imply that E F L T actually occurs during tidal breathing [1]. The location of expiratory flow limitation is considered to be in the central airways (4th–7th generation) and move to the periphery during forced expiratory manoeuvres. It is located beyond the 7th (i.e., from the 8th onwards) generation during tidal breathing [2–4]. Tidal expiratory flow limitation ( E F L T ) [5–8] plays a central role according to a recent hypothesis [5] on the transition from small airways disease (SAD) to overt COPD in smokers. E F L T implies inhomogeneity of ventilation distribution with concurrent impairment of gas exchange and unevenly distributed stress and strain within the lung, which is amplified by tissue interdependence [6, 7] and may lead to small airway injury [5–8]. Initially, the latter is
Expiratory Flow Limitation Definition, Mechanisms, Methods, and Significance  [PDF]
Claudio Tantucci
Pulmonary Medicine , 2013, DOI: 10.1155/2013/749860
Abstract: When expiratory flow is maximal during tidal breathing and cannot be increased unless operative lung volumes move towards total lung capacity, tidal expiratory flow limitation (EFL) is said to occur. EFL represents a severe mechanical constraint caused by different mechanisms and observed in different conditions, but it is more relevant in terms of prevalence and negative consequences in obstructive lung diseases and particularly in chronic obstructive pulmonary disease (COPD). Although in COPD patients EFL more commonly develops during exercise, in more advanced disorder it can be present at rest, before in supine position, and then in seated-sitting position. In any circumstances EFL predisposes to pulmonary dynamic hyperinflation and its unfavorable effects such as increased elastic work of breathing, inspiratory muscles dysfunction, and progressive neuroventilatory dissociation, leading to reduced exercise tolerance, marked breathlessness during effort, and severe chronic dyspnea. 1. Definition Expiratory (air) flow limitation (EFL) during tidal breathing is a well-defined, mechanical pathophysiological condition occurring, either during physical exercise or at rest, before in supine and later on in sitting-standing position, when expiratory flow cannot be further increased by increasing expiratory muscles effort (i.e., by increasing pleural and alveolar pressure) because it is maximum at that tidal volume [1]. In other words, under the prevailing conditions, the respiratory system is globally limited as flow generator even during tidal expiration, and greater expiratory flow rates may be achieved just by increasing operating lung volumes, (i.e., moving progressively the end-expiratory lung volume (EELV) towards total lung capacity). In fact, the volume-related decrease of airway resistance and increase of elastic recoil are the only effective mechanisms to obtain higher expiratory flows in case of EFL [2]. As a consequence, the term airflow limitation widely used to indicate the abnormal decrease of maximal expiratory flow rates at a given lung volume, as compared to predicted (i.e., airflow reduction or airflow obstruction), is inappropriate and should not be adopted unless the condition previously described is present (Figure 1). Figure 1: Maximal and tidal flow-volume curve in two representative COPD patients: one with airflow reduction and tidal expiratory flow limitation (EFL) at rest (a), the other only with airflow reduction at rest and potential EFL during exercise (b). The NEP application at rest does not increase expiratory flow in the
Physiological techniques for detecting expiratory flow limitation during tidal breathing  [cached]
N.G. Koulouris,G. Hardavella
European Respiratory Review , 2011,
Abstract: Patients with severe chronic obstructive pulmonary disease (COPD) often exhale along the same flow–volume curve during quiet breathing as they do during the forced expiratory vital capacity manoeuvre, and this has been taken as an indicator of expiratory flow limitation at rest (EFLT). Therefore, EFLT, namely attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow. EFLT leads to small airway injury and promotes dynamic pulmonary hyperinflation, with concurrent dyspnoea and exercise limitation. In fact, EFLT occurs commonly in COPD patients (mainly in Global Initiative for Chronic Obstructive Lung Disease III and IV stage), in whom the latter symptoms are common, but is not exclusive to COPD, since it can also be detected in other pulmonary and nonpulmonary diseases like asthma, acute respiratory distress syndrome, heart failure and obesity, etc. The existing up to date physiological techniques of assessing EFLT are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, noninvasive, practical and accurate new technique.
Total inspiratory and expiratory impedance in patients with severe chronic obstructive pulmonary disease
Silva, Karla Kristine Dames;Lopes, Agnaldo José;Jansen, José Manoel;Melo, Pedro Lopes de;
Clinics , 2011, DOI: 10.1590/S1807-59322011001200014
Abstract: objectives: several studies have confirmed the high potential of the forced oscillation technique for the assessment of respiratory modifications related to chronic obstructive pulmonary disease. however, most of these studies did not employ within-breath analyses of the respiratory system. the aim of this study is to analyze respiratory impedance alterations in different phases of the respiratory cycle of chronic obstructive pulmonary disease patients and to evaluate their clinical use. methods: 39 individuals were evaluated, including 20 controls and 19 individuals with chronic obstructive pulmonary disease who experienced severe airway obstruction.weevaluated the mean respiratory impedance (zm) as well as values for inspiration (zi) and expiration cycles (ze), at the beginning of inspiration (zbi) and expiration (zbe). the peak-to-peak impedance (zpp), and the impedance change (dzrs) were also analyzed. the clinical usefulness was evaluated by investigating the sensibility, specificity and the area under the receiver operating characteristic curve. results: the respiratory impedance increased in individuals with chronic obstructive pulmonary disease in all of the studied parameters (zm, zi, ze, zbi, zbe, dzrs and zpp). these changes were inversely associated with spirometric parameters. higher impedanceswere observed in the expiratory phase of individualswith chronic obstructive pulmonary disease. all of the studied parameters, except for dzrs (area under the receiver operating characteristic ,0.8), exhibited high accuracy for clinical use (area under the receiver operating characteristic .0.90; sensibility $ 0.85; sp $ 0.85). conclusions: the respiratory alterations in severe chronic obstructive pulmonary disease may be identified by the increase in respiratory system impedance, which is more evident in the expiratory phase. these results confirm the potential of within-breath analysis of respiratory impedance for the assessment of respiratory modifications rela
Expiratory time constant for determinations of plateau pressure, respiratory system compliance, and total resistance
Nawar Al-Rawas, Michael J Banner, Neil R Euliano, Carl G Tams, Jeff Brown, A Daniel Martin, Andrea Gabrielli
Critical Care , 2013, DOI: 10.1186/cc12500
Abstract: Adults (n = 92) with acute respiratory failure were categorized into four groups depending on the mode of ventilatory support ordered by attending physicians, i. e., volume controlled - continuous mandatory ventilation (VC-CMV), volume controlled - synchronized intermittent mandatory ventilation (VC-SIMV), volume control plus (VC+), and pressure support ventilation (PSV). Positive end expiratory pressure as ordered was combined with all aforementioned modes. Pplt, determined by the traditional end inspiratory pause (EIP) method, was combined in equations to determine Crs and Rtot. Following that, the tauE method was employed, tauE was estimated from point-by-point measurements of exhaled tidal volume and flow rate, it was then combined in equations to determine Pplt, Crs, and Rtot. Both methods were compared using regression analysis.tauE, ranging from mean values of 0.54 sec to 0.66 sec, was not significantly different among ventilatory modes. The tauE method was an excellent predictor of Pplt, Crs, and Rtot for various ventilatory modes; r2 values for the relationships of E and EIP methods ranged from 0.94 to 0.99 for Pplt, 0.90 to 0.99 for Crs, and 0.88 to 0.94 for Rtot (p < 0.001). Bias and precision values were negligible.We found the tauE method was just as good as the EIP method for determining Pplt, Crs, and Rtot for various modes of ventilatory support for patients with acute respiratory failure. It is unclear if the tauE method can be generalized to patients with chronic obstructive lung disease. tauE is determined during passive deflation of the lungs without the need for changing the ventilatory mode and disrupting a patient's breathing. The tauE method obviates the need to apply an EIP, allows for continuous and automatic surveillance of inspiratory Pplt so it can be maintained [less than or equal to] 30 cm H2O for lung protection and patient safety, and permits real time assessments of pulmonary mechanics.
Effects of breathing maneuver and sitting posture on muscle activity in inspiratory accessory muscles in patients with chronic obstructive pulmonary disease
Ki-song Kim, Min-kwang Byun, Won-hwee Lee, Heon-seock Cynn, Oh-yun Kwon, Chung-hwi Yi
Multidisciplinary Respiratory Medicine , 2012, DOI: 10.1186/2049-6958-7-9
Abstract: Twelve men with COPD participated in the study. Inductive respiratory plethysmography and surface electromyography were used to simultaneously measure TV, RR, and muscle activity of the inspiratory accessory muscles [the scalenus (SM), sternocleidomastoid (SCM), and pectoralis major (PM) muscles] during quiet natural breathing (QB) and pursed-lips breathing (PLB) in three sitting postures: neutral position (NP), with armm support (WAS), and with arm and head support (WAHS).Two-way repeated-measures analysis of variance was employed. In a comparison of breathing patterns, PLB significantly increased TV and decreased RR compared to QB. Muscle activity in the SM and SCM increased significantly in PLB compared to QB. In a comparison of sitting postures, the muscle activity of the SM, SCM, and PM increased in the forward-leaning position.The results suggest that in COPD, PLB induced a favorable breathing pattern (increased TV and reduced RR) compared to QB. Additionally, WAS and WAHS positions increased muscle activity of the inspiratory accessory muscles during inspiration versus NP. Differential involvement of accessory respiratory muscles can be readily studied in COPD patients, allowing monitoring of respiratory load during pulmonary rehabilitation.
Systemic inflammation after inspiratory loading in chronic obstructive pulmonary disease  [cached]
Antonia Fuster,Jaume Sauleda,Ernest Sala,Bernardí Barceló
International Journal of COPD , 2008,
Abstract: Antonia Fuster, Jaume Sauleda, Ernest Sala, Bernardí Barceló1, Jaume Pons2, Miguel Carrera, Aina Noguera1, Bernat Togores, Alvar GN AgustíServeis de Pneumologia, 1Analisis Clinics, and 2Inmunología, Hospital Universitari Son Dureta, Fundación Caubet-Cimera and CIBER Enfermedades Respiratorias, Mallorca, SpainObjective: Patients with chronic obstructive pulmonary disease (COPD) present systemic inflammation. Strenuous resistive breathing induces systemic inflammation in healthy subjects. We hypothesized that the increased respiratory load that characterizes COPD can contribute to systemic inflammation in these patients.Patients and methods: To test this hypothesis, we compared leukocyte numbers and levels of circulating cytokines (tumor necrosis factor alpha [TNFα], interleukin-1β [IL-1β], IL-6, IL-8, and IL-10), before and 1 hour after maximal incremental inspiratory loading in 13 patients with stable COPD (forced expiratory volume in one second [FEV1] 29 ± 2.5% ref) and in 8 healthy sedentary subjects (FEV1 98 ± 5% ref).Results: We found that: (1) at baseline, patients with COPD showed higher leukocyte counts and IL-8 levels than controls (p < 0.01); and, (2) one hour after maximal inspiratory loading these values were unchanged, except for IL-10, which increased in controls (p < 0.05) but not in patients with COPD.Conclusions: This study confirms the presence of systemic inflammation in COPD, shows that maximal inspiratory loading does not increase the levels of pro-inflammatory cytokines (IL-1β, IL-8) in COPD patients or controls, but suggests that the former may be unable to mount an appropriate systemic anti-inflammatory response to exercise.Keywords: COPD, endurance, exercise, IL-10, respiratory muscles, systemic inflammation
Virtual respiratory system in investigation of CPAP influence on optimal breathing frequency in obstructive lungs disease  [cached]
Golczewski Tomasz,Darowski Marek
Nonlinear Biomedical Physics , 2007, DOI: 10.1186/1753-4631-1-6
Abstract: Background Continuous Positive Airway Pressure (CPAP) is a commonly accepted method of spontaneous breathing support in obstructive lung disease. Previous work suggested that the cause of the CPAP efficacy in the obstructive lung disease localized in bronchi of middle order (OLDMO) is not as obvious as, for example, in the obstructive sleep apnea. Since CPAP reduces obstruction and the optimal breathing frequency (BF) depends on the obstruction level, it seems to be important to analyze the dependence of the optimal BF on CPAP. Aim To analyze the support efficacy cause in OLDMO, esp. the relationship between the CPAP value and optimal BF. Method Investigations utilized previously built virtual respiratory system. Its most important factors: nonlinear lungs compliance and changeability of nonlinear airway resistance (Raw). Influence of BF and the CPAP value on the tidal volume and minute ventilation was analyzed for four exemplary virtual patients: healthy ("standard") and suffering from moderate, severe, and the very severe OLDMO (the other parameters, esp. respiratory muscles effort, were unchanged). Minute inspiratory work as a criterion of the BF optimization. Results CPAP decreased Raw making breathing easier, however, it shifted the working point of the respiratory system towards the smaller lungs compliance making breathing harder. The final result depended on the Raw value: CPAP improved breathing of patients with the serious OLDMO while it worsened healthy person breathing. The optimal CPAP value depended on the Raw value. If a virtual patient suffering from the serious OLDMO was not supported with CPAP, he had to breathe with low frequency because minute ventilation did not rise with BF increase. The optimal BF depended on the CPAP value (the greater the value, the greater the frequency). Conclusion The CPAP efficacy depends on the level of OLDMO. CPAP is efficient in the severe OLDMO because it increases the optimal BF, which makes possible less energy-consuming breathing with frequency close to the normal one (greater BF means smaller tidal volume and thus smaller work against lungs compliance).
Differences in tidal breathing between infants with chronic lung diseases and healthy controls
G Schmalisch, S Wilitzki, RR Wauer
BMC Pediatrics , 2005, DOI: 10.1186/1471-2431-5-36
Abstract: In the age of 36–42 postconceptional weeks TB measurements were performed in 48 healthy newborns (median age and weight 7d, 3100 g) and 48 infants with CLD (80d, 2465 g)) using the deadspace-free flow-through technique. Once the infants had adapted to the mask and were sleeping quietly and breathing regularly, 20–60 breathing cycles were evaluated. Beside the shape of the tidal breathing flow-volume loop (TBFVL) 18 TB parameters were analyzed using ANOVA with Bonferroni correction. Receiver-operator characteristic (ROC) curves were calculated to investigate the discriminative ability of TB parameters.The incidence of concave expiratory limbs in CLD infants was 31% and significantly higher compared to controls (2%) (p < 0.001). Significant differences between CLD infants and controls were found in 11/18 TB parameters. The largest differences were seen in the mean (SD) inspiratory time 0.45(0.11)s vs. 0.65(0.14)s (p < 0.0001) and respiratory rate (RR) 55.4(14.2)/min vs. 39.2(8.6)/min (p < 0.0001) without statistically significant difference in the discriminative power between both time parameters. Most flow parameters were strongly correlated with RR so that there is no additional diagnostic value. No significant differences were found in the tidal volume and commonly used TB parameters describing the expiratory flow profile.The breathing pattern of CLD infants differs significantly from that of healthy controls. Concave TBFVL and an increased RR measured during quiet sleep and under standardized conditions may indicate diminished respiratory functions in CLD infants whereas most of the commonly used TB parameters are poorly predictive.With increasing numbers of infants born preterm, respiratory diseases associated with immature lungs and the need for mechanical ventilation or supplemental oxygen is becoming very common [1]. However, in the post surfactant era the "classic" or severe form of chronic lung disease (CLD) has been replaced by less severe forms ("mild" CLD
Separate determination of inspiratory and expiratory dynamic lung mechanics using expiratory flow control
C Stahl, K M?ller, S Schumann, J Brugger, J Guttmann
Critical Care , 2006, DOI: 10.1186/cc4365
Abstract: Different flow profiles were applied in two mechanical lung models. These profiles included standard ventilator and EFC modes. The volume dependency of dynamic respiratory mechanics was calculated using the SLICE method [1]. The algorithm was extended for a separate analysis of the inspiration and expiration phase. We validated the efficacy of EFC in six sheep using a modified standard ventilator (Evita 4; Draeger Medical, Lübeck, Germany) with EFC in the pressure-control mode.It is mainly the passive expiration with the linear dependency of flow, volume and pressure that inhibits the separate inspiratory and expiratory analysis of respiratory mechanics. Figure 1 shows the effect of EFC on the breathing pattern in a healthy animal. At early expiration with EFC, flow is drastically reduced as compared with passive expiration (grey line). With EFC (solid line), the change in flow is independent of the change in volume, allowing the determination of R and C. Figure 2 displays the analysis of compliance in a lung model (C = 24) during constant flow ventilation without EFC. Without EFC, expiratory compliance is indeterminable (solid line). With EFC (Fig. 3) excellent agreement of inspiratory and expiratory compliance with the reference compliance was found. In six healthy sheep compliance determined during EFC was computed in inspiration and expiration. Dependent on the extent of EFC, we found a high agreement of inspiratory and expiratory compliances compared with mixed (inspiratory and expiratory) data.The control of expiratory flow allows the application of volume-dependent multiple linear regression analysis during inspiration respectively expiration alone. With EFC, the separate mechanical analysis reveals accurate results in well-controlled mechanical lung models and in experimental animals.
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