Detection of Tidal Recruitment/Overdistension in Lung-Healthy Mechanically Ventilated Patients Under General Anesthesia

Carvalho, Alysson R.; Pacheco, Sergio A.; Rocha, Patricia Vieira de Souza; Bergamini, Bruno Curty; Paula, Luís Felipe; Jandre, Frederico C.; Giannella-Neto, Antonio

doi:10.1213/ane.0b013e318254230b

Cited by 27 publications

(23 citation statements)

References 33 publications

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“…Equation (7) assumes that the relationship between tracheal pressure and volume is best characterized by a cubic polynomial [28]. Based on estimates of these elastance coefficients, we determined an extended version of a nonlinear volume-dependent elastance index [4, 9, 29]:

% E_{3} = \frac{E_{2} V_{T} + E_{3} V_{T}^{2}}{E_{1} + E_{2} V_{T} + E_{3} V_{T}^{2}} \times 100 %

where % E 3 denotes the percentage of nonlinear elastic recoil.…”

Section: Methodsmentioning

confidence: 99%

“…Such assessments may include the concavity of the airway pressure vs. time tracing [3, 4], so-called ‘best’ compliance [5–7], or nonlinear distortions of elastance [8, 9]. More recent studies have adjusted PEEP or V T based on measurements of esophageal pressure to estimate transpulmonary pressure, rather than transrespiratory pressure [10].…”

Section: Introductionmentioning

confidence: 99%

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Intratidal Overdistention and Derecruitment in the Injured Lung: A Simulation Study

Amini

Herrmann

Kaczka

2017

IEEE Trans. Biomed. Eng.

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Goal Ventilated patients with the Acute Respiratory Distress Syndrome (ARDS) are predisposed to cyclic parenchymal overdistention and derecruitment, which may worsen existing injury. We hypothesized that intratidal variations in global mechanics, as assessed at the airway opening, would reflect such distributed processes. Methods We developed a computational lung model for determining local instantaneous pressure distributions and mechanical impedances continuously during a breath. Based on these distributions and previous literature, we simulated the within-breath variability of airway segment dimensions, parenchymal viscoelasticity, and acinar recruitment in an injured canine lung for tidal volumes (VT) of 10, 15, and 20 mL kg−1 and positive end-expiratory pressures (PEEP) of 5, 10, and 15 cm H2O. Acini were allowed to transition between recruited and derecruited states when exposed to stochastically-determined critical opening and closing pressures, respectively. Results For conditions of low VT and low PEEP, we observed small intratidal variations in global resistance and elastance, with a small number of cyclically recruited acini. However with higher VT and PEEP, larger variations in resistance and elastance were observed, and the majority of acini remained open throughout the breath. Changes in intratidal resistance, elastance, and impedance followed well-defined parabolic trajectories with tracheal pressure, achieving minima near 12 to 16 cm H2O. Conclusion Intratidal variations in lung mechanics may allow for optimization of ventilator settings in patients with ARDS, by balancing lung recruitment against parenchymal overdistention. Significance Titration of airway pressures based on variations in intratidal mechanics may mitigate processes associated with injurious ventilation.

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% E_{3} = \frac{E_{2} V_{T} + E_{3} V_{T}^{2}}{E_{1} + E_{2} V_{T} + E_{3} V_{T}^{2}} \times 100 %

where % E 3 denotes the percentage of nonlinear elastic recoil.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Intratidal Overdistention and Derecruitment in the Injured Lung: A Simulation Study

Amini

Herrmann

Kaczka

2017

IEEE Trans. Biomed. Eng.

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“…Respiratory system elastance (E, RS ) and resistance (R, RS ) were calculated based on the equation of motion (Uhlig et al, 2014):

P_{a w} (t) = R_{R S} • \overset{V}{overset} (t) + E_{R S} • V (t) + P_{0}

, where t is time, V is volume, and P 0 is P aw at end-expiration. Volume-independent elastance (E1, RS ) and volume-dependent elastance (E2, RS ) as well as the E, RS non-linearity index (%E2) were calculated cycle-by-cycle as described elsewhere (Carvalho et al, 2013b). …”

Section: Methodsmentioning

confidence: 99%

Variable Ventilation Improved Respiratory System Mechanics and Ameliorated Pulmonary Damage in a Rat Model of Lung Ischemia-Reperfusion

et al. 2017

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Lung ischemia-reperfusion injury remains a major complication after lung transplantation. Variable ventilation (VV) has been shown to improve respiratory function and reduce pulmonary histological damage compared to protective volume-controlled ventilation (VCV) in different models of lung injury induced by endotoxin, surfactant depletion by saline lavage, and hydrochloric acid. However, no study has compared the biological impact of VV vs. VCV in lung ischemia-reperfusion injury, which has a complex pathophysiology different from that of other experimental models. Thirty-six animals were randomly assigned to one of two groups: (1) ischemia-reperfusion (IR), in which the left pulmonary hilum was completely occluded and released after 30 min; and (2) Sham, in which animals underwent the same surgical manipulation but without hilar clamping. Immediately after surgery, the left (IR-injured) and right (contralateral) lungs from 6 animals per group were removed, and served as non-ventilated group (NV) for molecular biology analysis. IR and Sham groups were further randomized to one of two ventilation strategies: VCV (n = 6/group) [tidal volume (VT) = 6 mL/kg, positive end-expiratory pressure (PEEP) = 2 cmH2O, fraction of inspired oxygen (FiO2) = 0.4]; or VV, which was applied on a breath-to-breath basis as a sequence of randomly generated VT values (n = 1200; mean VT = 6 mL/kg), with a 30% coefficient of variation. After 5 min of ventilation and at the end of a 2-h period (Final), respiratory system mechanics and arterial blood gases were measured. At Final, lungs were removed for histological and molecular biology analyses. Respiratory system elastance and alveolar collapse were lower in VCV than VV (mean ± SD, VCV 3.6 ± 1.3 cmH20/ml and 2.0 ± 0.8 cmH20/ml, p = 0.005; median [interquartile range], VCV 20.4% [7.9–33.1] and VV 5.4% [3.1–8.8], p = 0.04, respectively). In left lungs of IR animals, VCV increased the expression of interleukin-6 and intercellular adhesion molecule-1 compared to NV, with no significant differences between VV and NV. Compared to VCV, VV increased the expression of surfactant protein-D, suggesting protection from type II epithelial cell damage. In conclusion, in this experimental lung ischemia-reperfusion model, VV improved respiratory system elastance and reduced lung damage compared to VCV.

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“…Several studies investigated the effects of different ventilator settings upon recruitment or derecruitment measured by static changes in airway pressure or total lung volume (typically during a breath hold) (7,8). However, these studies did not consider the dynamics of cyclic recruitment and derecruitment (c-R/D) and the consequent differences between end-inspiratory and end-expiratory pauses versus these same end-inspiratory and expiratory pressures during dynamic breathing.…”

Section: Influence Of Inspiration To Expirationmentioning

confidence: 99%

Influence of Inspiration to Expiration Ratio on Cyclic Recruitment and Derecruitment of Atelectasis in a Saline Lavage Model of Acute Respiratory Distress Syndrome*

Boehme

Bentley

Hartmann

et al. 2015

Critical Care Medicine

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e65Objective: Cyclic recruitment and derecruitment of atelectasis can occur during mechanical ventilation, especially in injured lungs. Experimentally, cyclic recruitment and derecruitment can be quantified by respiration-dependent changes in Pao 2 (ΔPao 2 ), reflecting the varying intrapulmonary shunt fraction within the respiratory cycle. This study investigated the effect of inspiration to expiration ratio upon ΔPao 2 and Horowitz index. Design: Prospective randomized study.Setting: Laboratory investigation. Subjects: Piglets, average weight 30 ± 2 kg. Interventions: At respiratory rate 6 breaths/min, end-inspiratory pressure (P endinsp ) 40 cm H 2 O, positive end-expiratory pressure 5 cm H 2 O, and Fio 2 1.0, measurements were performed at randomly set inspiration to expiration ratios during baseline healthy and mild surfactant depletion injury. Lung damage was titrated by repetitive surfactant washout to induce maximal cyclic recruitment and derecruitment as measured by multifrequency phase fluorimetry. Regional ventilation distribution was evaluated by electrical impedance tomography.Step changes in airway pressure from 5 to 40 cm H 2 O and vice versa were performed after lavage to calculate Po 2 -based recruitment and derecruitment time constants (TAU). Measurements and Main Results: In baseline healthy, cyclic recruitment and derecruitment could not be provoked, whereas in model acute respiratory distress syndrome, the highest ΔPao 2 were routinely detected at an inspiration to expiration ratio of 1:4 (range, 52-277 torr [6.9-36.9 kPa]). Shorter expiration time reduced cyclic recruitment and derecruitment significantly (158 ± 85 torr [21.1 ± 11.3 kPa] [inspiration to expiration ratio, 1:4]; 25 ± 12 torr [3.3 ± 1.6 kPa] [inspiration to expiration ratio, 4:1]; p < 0.0001), whereas the Pao 2 /Fio 2 ratio increased (267 ± 50 [inspiration to expiration ratio, 1:4]; 424 ± 53 [inspiration to expiration ratio, 4:1]; p < 0.0001). Correspondingly, regional ventilation redistributed toward dependent lung regions (p < 0.0001). Recruitment was much faster (TAU: fast 1.6 s [78%]; slow 9.2 s) than derecruitment (TAU: fast 3.1 s [87%]; slow 17.7 s) (p = 0.0078). Conclusions: Inverse ratio ventilation minimizes cyclic recruitment and derecruitment of atelectasis in an experimental model of surfactant-depleted pigs. Time constants for recruitment and derecruitment, and regional ventilation distribution, reflect these findings and highlight the time dependency of cyclic recruitment and derecruitment. (Crit Care Med 2015; 43:e65-e74)

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Detection of Tidal Recruitment/Overdistension in Lung-Healthy Mechanically Ventilated Patients Under General Anesthesia

Abstract: The distension index %E(2), derived from the VDSCM considering flow-dependencies, seems able to identify tidal recruitment/overdistension induced by Vt and PEEP independent of flow waveform in healthy lung-anesthetized patients.

Cited by 27 publications

References 33 publications

Intratidal Overdistention and Derecruitment in the Injured Lung: A Simulation Study

Intratidal Overdistention and Derecruitment in the Injured Lung: A Simulation Study

Variable Ventilation Improved Respiratory System Mechanics and Ameliorated Pulmonary Damage in a Rat Model of Lung Ischemia-Reperfusion

Influence of Inspiration to Expiration Ratio on Cyclic Recruitment and Derecruitment of Atelectasis in a Saline Lavage Model of Acute Respiratory Distress Syndrome*

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