Design of a new variable-ventilation method optimized for lung recruitment in mice

Thammanomai, Apiradee; Hueser, Lauren E.; Majumdar, Arnab; Bartolák‐Suki, Erzsébet; Suki, Bélâ

doi:10.1152/japplphysiol.01002.2007

Cited by 43 publications

(67 citation statements)

References 56 publications

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“…5 In animal models of ARDS, variable ventilation strategies are superior to conventional control mode mechanical ventilation (CMV) or CMV with recruitment maneuvers with respect to lung mechanics, gas exchange, surfactant content, and inflammatory mediators with an overall decrease in distending stress. [5][6][7][8][9][10][11][12] In a recent computed tomography (CT) imaging study, we confirmed BVV induced recruitment of both poorly and non-aerated lung regions. 13 In this study, we hypothesized that the recruitment benefit and periodic low V T breaths seen with BVV could result in enhanced resolution of edema fluid in ARDS.…”

supporting

confidence: 76%

Resolution of pulmonary edema with variable mechanical ventilation in a porcine model of acute lung injury

Graham

Gulati

Kha

et al. 2011

Can J Anesth/J Can Anesth

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Objective Resolution of the acute respiratory distress syndrome (ARDS) requires clearance of pulmonary edema. Biologically variable ventilation (BVV) strategies that improve gas exchange, lung mechanics, and inflammatory mediators in ARDS may be beneficial in this regard. We used quantitative computed tomography (CT), a single indicator thermodilution system (PiCCOÒ) to determine extravascular lung water (EVLW), and the change in edema protein concentration over time to compare edema clearance with BVV vs conventional mechanical ventilation (CMV) in a porcine ARDS model. Methods Sixteen pigs with oleic acid lung injury were randomized to four hours of ventilation with either CMV (n = 8) or BVV (n = 8) at identical low tidal volume and minute ventilation over time. Hemodynamic variables, gas exchange, lung mechanics, and PiCCO derived EVLW were determined hourly. Computed tomography images and edema fluid samples were obtained at baseline lung injury and after four hours of ventilation. Wet and dry lung weights were determined postmortem.Results At four hours with BVV, peak airway pressure was decreased significantly and lung compliance improved compared with CMV (P = 0.003; P \ 0.001, respectively). Hemodynamic variables and gas exchange were not different between groups. Also at four hours, computed tomography revealed an increase in total gas volume (P = 0.001) and a decrease in total lung weight and global lung density (P = 0.005; P = 0.04 respectively) with BVV. These findings were associated with a significant increase in the gas volume of normally aerated lung regions (P \ 0.001) and a decrease in the poorly and non-aerated lung regions (P = 0.001). No change in any CT parameter occurred with CMV. The lung weights derived from computed tomography correlated well with postmortem wet weights (R 2 = 0.79; P \ 0.01). The decrease in PiCCO derived EVLW from injury to four hours did not differ significantly between BVV and CMV. Extravascular lung water showed no correlation with postmortem wet weights and significantly underestimated lung water. Average alveolar fluid clearance rates were positive (1.4%Áhr -1 (3%)) with BVV and negative with CMV (-2.0%Áhr -1 (4%)). Conclusions In a comparison between BVV and CMV, computed tomography evidence suggests that BVV facilitates enhanced clearance and/or redistribution of edema fluid with improved recruitment of atelectatic and poorly aerated lung regions; no such evidence was seen with either single thermodilution measurement of EVLW or edema clearance rates. The results of computed tomography provide further evidence of the benefit of BVV over conventional ventilation in ARDS. RésuméObjectif La re´solution d'un syndrome de de´tresse respiratoire aigue¨(SDRA) ne´cessite l'e´limination de

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supporting

confidence: 76%

Resolution of pulmonary edema with variable mechanical ventilation in a porcine model of acute lung injury

Graham

Gulati

Kha

et al. 2011

Can J Anesth/J Can Anesth

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“…Because bubble CPAP is compared with conventional ventilator CPAP, 12-15 the therapy's merits have been attributed to the oscillatory component and its ability to exploit nonlinear properties of the lung, inducing phenomena such as stochastic resonance that requires a nonlinear dynamic system (the lung), weak biological signal (CPAP), and superimposed noise (pressure oscillations). 5 The connection was made by Suki and colleagues [16][17][18] while studying variable ventilation in computer simulations and rodent models of acute lung injury. The noise in the pressure signal produced by the bubbling takes advantage of the nonlinearity of atelectatic regions of the lung by exploring higher volume values while mean pressure remains the same; these increases in volume are indicative of additional recruitment.…”

Section: Discussionmentioning

confidence: 99%

“…5,10,18,20 A major limitation is that an in vitro model does not allow reliable correlations to patients due to its simplicity. Furthermore, our study did not have a leak in the system, so the oscillations will attenuate more than anticipated from the results in a realistic setting.…”

Section: Limitationsmentioning

confidence: 99%

Volume Oscillations Delivered to a Lung Model Using 4 Different Bubble CPAP Systems

2014

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The major finding of this study is that bubble CPAP can provide measureable ventilation effects in an infant lung model. We speculate that the differences noted in ⌬V between the different devices are a combination of the circuit/nasal prong configuration, bubbler configuration, and frequency of oscillations. Additional testing is needed in spontaneously breathing infants to determine whether a physiologic benefit exists when using the different bubble CPAP systems.

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“…For variable ventilation, the FlexiVent was preprogrammed to deliver a range of V T . The V T distribution used an algorithm that was developed previously to optimize alveolar recruitment in mice (26). Briefly, the distribution of V T above the most frequently applied V T was followed by a power law decay up to the maximum V T .…”

Section: Ventilation Protocolmentioning

confidence: 99%

Variable ventilation enhances ventilation without exacerbating injury in preterm lambs with respiratory distress syndrome

et al. 2012

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Background: as compared with constant respiratory rate (RR) and tidal volume (V T ) during controlled conventional mechanical ventilation (cV), variable ventilation (VV) using the same breath-to-breath minute volume but variable V T and RRs enhances ventilation efficiency in preterm lambs. We hypothesized that if V T was adjusted to target permissive hypercarbia, VV would result in more efficient gas exchange without increasing inflammatory and injurious responses in the lung. Methods: Preterm lambs at 129 d gestation were anesthetized, tracheotomized, and randomized to either cV (n = 8) or VV (n = 8) using the same initial average V T and RR. Lung mechanics and gas exchange were measured intermittently, and average V T was adjusted to target partial pressure of arterial carbon dioxide (PacO 2 ) of 40-50 mm hg for 3 h. Lung injury and inflammation were assessed from bronchoalveolar lavage fluid, lung tissue, and peripheral blood. results: VV achieved permissive hypercarbia using a lower average V T , peak inspiratory pressure, and elastance (increased compliance) as compared with cV. Oxygenation and markers of lung tissue inflammation or injury were not different apart from a lower wet:dry tissue ratio in the VV lungs. conclusions: VV improves ventilation efficiency and in vivo lung compliance in the ovine preterm lung without increasing lung inflammation or lung injury. Variability is an inherent property of many biological systems. Variable breathing is especially evident in newborn infants (1), particularly those born premature for whom sigh breaths with tidal volume (V T ) more than twice the average breath volume are critical to the maintenance of resting lung volume (2). Current ventilatory strategies advocated for the preterm infant focus on tightly regulating the size of each breath using volume guarantee or volume targeting of ventilator assisted/controlled breaths. An alternative approach, variable ventilation (VV), maintains a constant breath-to-breath minute volume throughout the study but distributes delivered V T and respiratory rate (RR) such that the lung may receive V T less than or greater than the average V T . In adult animal models, VV improves oxygenation and enhances gas exchange as compared with controlled conventional mechanical ventilation (CV) (3)(4)(5). Recently, we showed that VV enhanced both respiratory mechanics and gas exchange in preterm lambs as compared with CV that tightly regulated both breath size and rate (6), similar to findings of studies in adult animal models. However, unlike the adult animal studies, VV did not improve oxygenation in the preterm lambs, most likely due to shunting across fetal channels.Given previous evidence that serial repeated large V T at the initiation of ventilation in the preterm lung increases markers of inflammation and injury suggestive of volutrauma (7,8), successful clinical translation of VV in the preterm infant requires evidence that intermittent distributed sigh breaths are not injurious to the immature lung. Although there was no evide...

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Design of a new variable-ventilation method optimized for lung recruitment in mice

Cited by 43 publications

References 56 publications

Resolution of pulmonary edema with variable mechanical ventilation in a porcine model of acute lung injury

Resolution of pulmonary edema with variable mechanical ventilation in a porcine model of acute lung injury

Volume Oscillations Delivered to a Lung Model Using 4 Different Bubble CPAP Systems

Variable ventilation enhances ventilation without exacerbating injury in preterm lambs with respiratory distress syndrome

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