Lung recruitment assessed by total respiratory system input reactance

Dellacà, Raffaele L.; Olerud, Marie Andersson; Zannin, Emanuela; Kostic, Peter; Pompilio, Pasquale; Hedenstierna, Göran; Pedotti, A.; Frykholm, Peter

doi:10.1007/s00134-009-1673-3

Cited by 68 publications

(85 citation statements)

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“…X RS was determined from the P AO and flow signals during the oscillatory cycles at t 0min and t 2min by spectral analysis using the cross-spectrum method (38). The difference between X RS at t 0min and t 2min was used to evaluate the dynamics of recruitment, with a decrease in X RS from t 0min to t 2min taken to indicate derecruitment (17). Alterations in V L between t 0min and t 2min were categorized similarly.…”

Section: Discussionmentioning

confidence: 99%

“…FOT was assessed at 5 Hz because the use of X RS at 5 Hz has been validated for the assessment of V L recruitment (17), lung tissue distension, and P AW titration (19). However, infants usually receive HFOV at higher frequencies.…”

Section: Optimizing Hfov By Lung Mechanicsmentioning

confidence: 99%

“…Z RS is commonly expressed in terms of resistance of the expiratory system (R RS ) and reactance of the respiratory system (X RS ), which in turn represents the elastic and inertive properties of the system. Recent studies, using broad-band stimulating signals including very-low-frequency components (low frequency forced oscillation technique (LFOT)), showed that the frequency dependence of R RS is a sensitive indicator of mechanical heterogeneities in the lungs and that low-frequency dynamic elastance can be used to assess V L recruitment and distention during ventilation (16)(17)(18)(19)(20). Moreover, if proper mathematical interpretative models are applied to LFOT data, it is possible to discriminate between the mechanical properties of airways and lung tissue.…”

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confidence: 99%

“…Unfortunately, clinical application of LFOT for continuous bedside monitoring is limited by its high sensitivity to leaks and, importantly, by the interference of spontaneous breathing on the low-frequency components of the forcing signal. Recently, single-frequency FOT has been applied during conventional mechanical ventilation both in animal models (17,20,22,23) and in ventilated preterm newborns (11). In particular, X RS at 5 Hz (X RS ) identified the lowest positive endexpiratory pressure level able to keep the lung fully recruited (22,23), minimizing lung injury (23).…”

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Optimal mean airway pressure during high-frequency oscillatory ventilation determined by measurement of respiratory system reactance

et al. 2013

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Background:The aims of the present study were (i) to characterize the relationship between mean airway pressure (P AW ) and reactance measured at 5 Hz (reactance of the respiratory system (X RS ) , forced oscillation technique) and (ii) to compare optimal P AW (P opt ) defined by X RS , oxygenation, lung volume (V L ), and tidal volume (V T ) in preterm lambs receiving high-frequency oscillatory ventilation (HFOV). Methods: Nine 132-d gestation lambs were commenced on HFOV at P AW of 14 cmH 2 O (P start ). P AW was increased stepwise to a maximum pressure (P max ) and subsequently sequentially decreased to the closing pressure (P cl , oxygenation deteriorated) or a minimum of 6 cmH 2 O, using an oxygenation-based recruitment maneuver. X RS , regional V L (electrical impedance tomography), and V T were measured immediately after (t 0min ) and 2 min after (t 2min ) each P AW decrement. P opt defined by oxygenation, X RS , V L , and V T were determined. results: The P AW -X RS and P AW -V T relationships were dome shaped with a maximum at P cl +6 cmH 2 O, the same point as P opt defined by V L . Below P cl +6 cmH 2 O, X RS became unstable between t 0min and t 2min and was associated with derecruitment in the dependent lung. P opt , as defined by oxygenation, was lower than the P opt defined by X RS , V L , or V T . conclusion: X RS has the potential as a bedside tool for optimizing P AW during HFOV. h igh-frequency oscillatory ventilation (HFOV) is used to treat severe neonatal lung disease and has the potential to reduce ventilator-induced lung injury when applied optimally (1,2). HFOV optimally applied aims to recruit the lung and subsequently reduce mean airway pressure (P AW ) to an optimal pressure (P opt ) that achieves optimal lung recruitment at the lowest distending pressure (open lung strategy) (3,4). However, identification and maintenance of P opt remains challenging, particularly in the newly born, whose lungs are in a highly dynamic state because of fluid reabsorption and establishment of functional residual capacity (5). The lack of appropriate tools for the bedside assessment and continuous monitoring of lung function in infants makes targeting of P opt even more difficult.Oxygenation, evaluated by monitoring oxygen saturation (Sp O2 ), is most commonly used for targeting P opt during HFOV in clinical practice (6). However, Sp O2 is an imperfect guide for P AW titration as it is relatively uniform over a wide range of airway pressures and volumes (7). Beginning with the observations of Suter et al. (8), the notion that lung mechanics can guide pressure settings during mechanical ventilation has been examined carefully. For conventional ventilation, a relationship between end-expiratory lung volume (V L ), recruitment, and tidal breath mechanics has been demonstrated repeatedly (9,10). During HFOV, the same theoretical considerations apply (3), but the best means of assessing the mechanics of the oscillated lung remains unclear.A promising approach to noninvasive bedside assessment of lung mechanics ...

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Section: Discussionmentioning

confidence: 99%

Section: Optimizing Hfov By Lung Mechanicsmentioning

confidence: 99%

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Optimal mean airway pressure during high-frequency oscillatory ventilation determined by measurement of respiratory system reactance

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“…Forced oscillation technique (FOT) is based on the application of very small lung volume changes with a very short time period (i.e., 0.2 s for a forcing frequency of 5 Hz) in order to measure the oscillatory respiratory system compliance [14]. FOT may offer several potential advantages over traditional methods: (1) it applies very small volume displacement, and minimizes artifacts resulting from non-linearity of the respiratory system; (2) it does not require deep sedation and muscle paralysis; and (3) it can be integrated into currently available ventilator circuits at bedside.…”

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Forced oscillation technique: an alternative tool to define the optimal PEEP?

2011

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Oscillation Mechanics of the Respiratory System

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Irvin

Farré

et al. 2011

Comprehensive Physiology

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The mechanical impedance of the respiratory system defines the pressure profile required to drive a unit of oscillatory flow into the lungs. Impedance is a function of oscillation frequency, and is measured using the forced oscillation technique. Digital signal processing methods, most notably the Fourier transform, are used to calculate impedance from measured oscillatory pressures and flows. Impedance is a complex function of frequency, having both real and imaginary parts that vary with frequency in ways that can be used empirically to distinguish normal lung function from a variety of different pathologies. The most useful diagnostic information is gained when anatomically based mathematical models are fit to measurements of impedance. The simplest such model consists of a single flow-resistive conduit connecting to a single elastic compartment. Models of greater complexity may have two or more compartments, and provide more accurate fits to impedance measurements over a variety of different frequency ranges. The model that currently enjoys the widest application in studies of animal models of lung disease consists of a single airway serving an alveolar compartment comprising tissue with a constant-phase impedance. This model has been shown to fit very accurately to a wide range of impedance data, yet contains only four free parameters, and as such is highly parsimonious. The measurement of impedance in human patients is also now rapidly gaining acceptance, and promises to provide a more comprehensible assessment of lung function than parameters derived from conventional spirometry.

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Lung recruitment assessed by total respiratory system input reactance

Abstract: These results suggest that FOT and the measurement of C (X5) could be a useful tool for the non-invasive measurement of lung volume recruitment/derecruitment.

Cited by 68 publications

References 28 publications

Optimal mean airway pressure during high-frequency oscillatory ventilation determined by measurement of respiratory system reactance

Optimal mean airway pressure during high-frequency oscillatory ventilation determined by measurement of respiratory system reactance

Forced oscillation technique: an alternative tool to define the optimal PEEP?

Oscillation Mechanics of the Respiratory System

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