Expiratory Gas Concentration Curves for Examination of Uneven Distribution of Ventilation and Perfusion in the Lung

Rj, van Meerten

doi:10.1159/000192709

Cited by 14 publications

(4 citation statements)

References 4 publications

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“…Theoretical calculations on simplified lung models have shown that the width of the transitional phase II of the capnogram is due to the sequential arrival of the alveolar CO 2 fronts from different lung compartments. 13 The phase III slope is caused by sequential emptying of the lung, with better ventilated compartments contributing relatively more to the early part of the expirate and slowly ventilated compartments more to the latter part of the expirate. This has been demonstrated by separate bronchospirometry and capnography of the two lungs in a patient with occlusion of Results are given as mean ± SD.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Ventilation inhomogeneity assessed by nitrogen washout and ventilation-perfusion mismatch by capnography in stable and induced airway obstruction

Strömberg

Gustafsson

2000

Pediatr. Pulmonol.

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Section: Discussionmentioning

confidence: 99%

“…[6][7][8] Among the mechanisms resulting in a positive phase III slope in the capnogram 9-12 is the sequential emptying of lung units with different CO 2 concentrations and, hence, different VЈ A /Q ratios. 13,14 Lung units with a high CO 2 concentration contribute more to the latter part of the expirate than better ventilated units.…”

Section: Introductionmentioning

confidence: 99%

Ventilation inhomogeneity assessed by nitrogen washout and ventilation-perfusion mismatch by capnography in stable and induced airway obstruction

Strömberg

Gustafsson

2000

Pediatr. Pulmonol.

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“…2): phase I, the absolute dead space; phase II, the bronchial (or transitional) phase; phase III, the alveolar phase; and phase IV, the start of which is marked by an upward deflection in N 2 concentration (or downward deflection in SF 6 /He concentration). The bronchial phase is produced by the sequential arrival of alveolar gas fronts from different lung gas exchange units [28]. The phase III slope of the classical SBW reflects the VI over a range of lung volumes.…”

Section: Sbw Techniquementioning

confidence: 99%

Inert Gas Washout: Theoretical Background and Clinical Utility in Respiratory Disease

Robinson

Goldman²,

Gustafsson³

2009

Respiration

213

211

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Inert gas washout was first described more than 60 years ago and 2 principal tests have been developed from it: the single breath and multiple breath washout (MBW) techniques. The invention of fast responding gas analysers almost 60 years ago and small computers 30 years later have facilitated breath-by-breath analysis and the development of sophisticated analysis techniques. It is now possible to detect not only the degree of pulmonary ventilation inhomogeneity, but also to gain important insight into the location of the underlying disease process. While single breath washout requires a full vital capacity effort, tidal breathing during the multiple breath test requires minimal co-operation and co-ordination, and is feasible in subjects of all ages. Available MBW normative data from parameters, such as the lung clearance index, appears to vary minimally with age, making MBW particularly useful to follow children longitudinally. Multiple breath inert gas washout has demonstrated improved sensitivity, in comparison to spirometry, in the early detection of a number of important disease processes, including cystic fibrosis. Despite this, these important techniques remain under-utilised in the clinical setting and there is a lack of commercially available devices currently available. The recent resurgence of research in this area has produced a large number of important studies and a pronounced international interest has developed in these techniques. This review article will provide an overview of the theoretical background of inert gas washout and analysis indices, review important physiological and clinical insights gained from research to date (as well as from our own experience) to illustrate its utility, and outline the challenges that lie ahead in incorporating these techniques into the mainstream clinical setting.

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“…This structure leads to gas compartments containing variable CO 2 concentrations and also results in different local expiratory flows [11]. These phenomena contribute to the sequential emptying of the lung periphery in time, which then increases the time domain and volumetric S III values [3-5,10,24]. Since Raw reflects mainly the flow resistance of the central conducting airways [19,23,25], this parameter is not able to detect such alterations in the presence of emphysematous changes [26].…”

Section: Discussionmentioning

confidence: 99%

Effects of respiratory mechanics on the capnogram phases: importance of dynamic compliance of the respiratory system

et al. 2012

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IntroductionThe slope of phase III of the capnogram (SIII) relates to progressive emptying of the alveoli, a ventilation/perfusion mismatch, and ventilation inhomogeneity. SIII depends not only on the airway geometry, but also on the dynamic respiratory compliance (Crs); this latter effect has not been evaluated. Accordingly, we established the value of SIII for monitoring airway resistance during mechanical ventilation.MethodsSidestream capnography was performed during mechanical ventilation in patients undergoing elective cardiac surgery (n = 144). The airway resistance (Raw), total respiratory resistance and Crs displayed by the ventilator, the partial pressure of arterial oxygen (PaO2) and SIII were measured in time domain (ST-III) and in a smaller cohort (n = 68) by volumetry (SV-III) with and without normalization to the average CO2 phase III concentration. Measurements were performed at positive end-expiratory pressure (PEEP) levels of 3, 6 and 9 cmH2O in patients with healthy lungs (Group HL), and in patients with respiratory symptoms involving low (Group LC), medium (Group MC) or high Crs (Group HC).ResultsST-III and SV-III exhibited similar PEEP dependencies and distribution between the protocol groups formed on the basis of Crs. A wide interindividual scatter was observed in the overall Raw-ST-III relationship, which was primarily affected by Crs. Decreases in Raw with increasing PEEP were reflected in sharp falls in SIII in Group HC, and in moderate decreases in SIII in Group MC, whereas ST-III was insensitive to changes in airway caliber in Groups LC and HL.ConclusionsSIII assessed in the time domain and by volumetry provide meaningful information about alterations in airway caliber, but only within an individual patient. Although ST-III may be of value for bedside monitoring of the airway properties, its sensitivity depends on Crs. Thus, assessment of the capnogram shape should always be coupled with Crs when the airway resistance or oxygenation are evaluated.

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Expiratory Gas Concentration Curves for Examination of Uneven Distribution of Ventilation and Perfusion in the Lung

Cited by 14 publications

References 4 publications

Ventilation inhomogeneity assessed by nitrogen washout and ventilation-perfusion mismatch by capnography in stable and induced airway obstruction

Ventilation inhomogeneity assessed by nitrogen washout and ventilation-perfusion mismatch by capnography in stable and induced airway obstruction

Inert Gas Washout: Theoretical Background and Clinical Utility in Respiratory Disease

Effects of respiratory mechanics on the capnogram phases: importance of dynamic compliance of the respiratory system

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