Determination of functional residual capacity by oxygen washin-washout: a validation study

Maisch, Stefan; Boehm, Stephan H.; Weismann, D.; Reißmann, H.; Beckmann, Marcus; Fuellekrug, Bernd; Meyer, Andreas; Esch, Jochen Schulte am

doi:10.1007/s00134-007-0578-2

Cited by 28 publications

(29 citation statements)

References 14 publications

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“…Their calculations were based on the breath‐by‐breath measurements of oxygen and not calculations of nitrogen, thus called the ‘oxygen wash‐out technique.’ Weismann et al 66 further simplified and improved the technique using a physical/mathematical model that calculates the flow‐dependent delay time of the side‐stream O 2 analyzer. Clinically acceptable accuracy has been shown with this technique during spontaneous breathing in volunteers and patients 72,73 and during controlled and assisted mechanical ventilation 74 . Similar to the technique proposed by Olegard et al, 70 a step change of FiO 2 of only 0.1 does not negatively influence repeatability 75 .…”

Section: Physiologysupporting

confidence: 56%

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Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applications

Heinze

Eichler

2009

Acta Anaesthesiol Scand

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Direct measurement of lung volume, i.e. functional residual capacity (FRC) has been recommended for monitoring during mechanical ventilation. Mostly due to technical reasons, FRC measurements have not become a routine monitoring tool, but promising techniques have been presented. We performed a literature search of studies with the key words 'functional residual capacity' or 'end expiratory lung volume' and summarize the physiology and patho-physiology of FRC measurements in ventilated patients, describe the existing techniques for bedside measurement, and provide an overview of the clinical questions that can be addressed using an FRC assessment. The wash-in or wash-out of a tracer gas in a multiple breath maneuver seems to be best applicable at bedside, and promising techniques for nitrogen or oxygen wash-in/wash-out with reasonable accuracy and repeatability have been presented. Studies in ventilated patients demonstrate that FRC can easily be measured at bedside during various clinical settings, including positive end-expiratory pressure optimization, endotracheal suctioning, prone position, and the weaning from mechanical ventilation. Alveolar derecruitment can easily be monitored and improvements of FRC without changes of the ventilatory setting could indicate alveolar recruitment. FRC seems to be insensitive to over-inflation of already inflated alveoli. Growing evidence suggests that FRC measurements, in combination with other parameters such as arterial oxygenation and respiratory compliance, could provide important information on the pulmonary situation in critically ill patients. Further studies are needed to define the exact role of FRC in monitoring and perhaps guiding mechanical ventilation.

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Section: Physiologysupporting

confidence: 56%

“…Despite numerous studies dealing with the methodological and technical aspects of FRC measurements in ventilated adult patients, 10,36,56,58,66–68,70–75,83–85 only a few studies have used FRC measurements during the treatment of patients.…”

Section: Clinical Applicationsmentioning

confidence: 99%

Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applications

Heinze

Eichler

2009

Acta Anaesthesiol Scand

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“…This is of interest insofar as current tidal volume setting guidelines are based on predicted body weight (PBW) and as such are relatively insensitive to the severity of lung injury. PBW scales with the size of the normal lung, but not with that of the injured lung [80,81]. Consequently, Chiumello et al .…”

Section: Effects Of Mechanical Ventilation On the Topographical Distrmentioning

confidence: 99%

The physical basis of ventilator-induced lung injury

Plataki

Hubmayr

2010

Expert Review of Respiratory Medicine

102

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Although mechanical ventilation (MV) is a life-saving intervention for patients with acute respiratory distress syndrome (ARDS), it can aggravate or cause lung injury, known as ventilator-induced lung injury (VILI). The biophysical characteristics of heterogeneously injured ARDS lungs increase the parenchymal stress associated with breathing, which is further aggravated by MV. Cells, in particular those lining the capillaries, airways and alveoli, transform this strain into chemical signals (mechanotransduction). The interaction of reparative and injurious mechanotransductive pathways leads to VILI. Several attempts have been made to identify clinical surrogate measures of lung stress/ strain (e.g., density changes in chest computed tomography, lower and upper inflection points of the pressure-volume curve, plateau pressure and inflammatory cytokine levels) that could be used to titrate MV. However, uncertainty about the topographical distribution of stress relative to that of the susceptibility of the cells and tissues to injury makes the existence of a single 'global' stress/strain injury threshold doubtful. Keywordsacute lung injury; acute respiratory distress syndrome; esophageal pressure; lung strain; lung stress; mechanical ventilation; mechanotransduction; plateau pressure; ventilator-induced lung injury Acute respiratory distress syndrome (ARDS), as defined by the American-European Consensus Conference Committee, is a syndrome of inflammation and increased permeability associated with acute onset of hypoxemia (partial arterial oxygen pressure/fractional inspired oxygen [PaO 2 /FiO 2 ] ≤200 mmHg) accompanied by bilateral infiltrates on chest radiograph that cannot be explained by, but may coexist with, left atrial or pulmonary capillary hypertension (pulmonary artery occlusion pressure ≤18 mmHg) [1]. The term acute lung injury (ALI) implies a milder degree of hypoxemia (PaO 2 /FiO 2 ≤300 mmHg) [1]. It was first described by Ashbaugh et al. in 1967 in 12 patients, seven (58%) of whom died [2]. Mechanical ventilation (MV) is an integral part of ARDS therapy, but like all treatments, inappropriate application can lead to side effects, namely ventilator-induced lung injury (VILI). To date, limiting VILI through lower tidal volumes is the only intervention proven to reduce mortality in ARDS [3]. Patients randomized to a lower tidal volume (6 ml/kg) ventilation strategy had a 22% relative reduction in mortality compared with patients receiving 12 ml/kg [3]. Although mortality in patients with ALI/ ARDS in large randomized controlled trials in the last decade

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“…Repeated CT scans and gas-dilution techniques are two validated methods of lung-volume measurement but are so complex that their use has been confined to research settings. Recently, washout/washin techniques using oxygen [6,7] or nitrogen [8,9] have been made available in ICU ventilators, allowing bedside EELV measurement. A comparison of the nitrogen washout/washin EELV measurement with helium dilution or CT scan had shown good correlations in stable patients ventilated with low-PEEP levels [8].…”

Section: Introductionmentioning

confidence: 99%

Accuracy and precision of end-expiratory lung-volume measurements by automated nitrogen washout/washin technique in patients with acute respiratory distress syndrome

et al. 2011

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IntroductionEnd-expiratory lung volume (EELV) is decreased in acute respiratory distress syndrome (ARDS), and bedside EELV measurement may help to set positive end-expiratory pressure (PEEP). Nitrogen washout/washin for EELV measurement is available at the bedside, but assessments of accuracy and precision in real-life conditions are scant. Our purpose was to (a) assess EELV measurement precision in ARDS patients at two PEEP levels (three pairs of measurements), and (b) compare the changes (Δ) induced by PEEP for total EELV with the PEEP-induced changes in lung volume above functional residual capacity measured with passive spirometry (ΔPEEP-volume). The minimal predicted increase in lung volume was calculated from compliance at low PEEP and ΔPEEP to ensure the validity of lung-volume changes.MethodsThirty-four patients with ARDS were prospectively included in five university-hospital intensive care units. ΔEELV and ΔPEEP volumes were compared between 6 and 15 cm H2O of PEEP.ResultsAfter exclusion of three patients, variability of the nitrogen technique was less than 4%, and the largest difference between measurements was 81 ± 64 ml. ΔEELV and ΔPEEP-volume were only weakly correlated (r2 = 0.47); 95% confidence interval limits, -414 to 608 ml). In four patients with the highest PEEP (≥ 16 cm H2O), ΔEELV was lower than the minimal predicted increase in lung volume, suggesting flawed measurements, possibly due to leaks. Excluding those from the analysis markedly strengthened the correlation between ΔEELV and ΔPEEP volume (r2 = 0.80).ConclusionsIn most patients, the EELV technique has good reproducibility and accuracy, even at high PEEP. At high pressures, its accuracy may be limited in case of leaks. The minimal predicted increase in lung volume may help to check for accuracy.

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Determination of functional residual capacity by oxygen washin-washout: a validation study

Cited by 28 publications

References 14 publications

Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applications

Measurements of functional residual capacity during intensive care treatment: the technical aspects and its possible clinical applications

The physical basis of ventilator-induced lung injury

Accuracy and precision of end-expiratory lung-volume measurements by automated nitrogen washout/washin technique in patients with acute respiratory distress syndrome

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