Dead space analysis at different levels of positive end-expiratory pressure in acute respiratory distress syndrome patients

Gogniat, Emiliano; Ducrey, Marcela; Dianti, José; Madorno, Matías; Roux, N.; Midley, Alejandro; Raffo, Júlio; Giannasi, Sergio; Román, Eduardo San; Suárez-Sipmann, Fernando; Tusman, Gerardo

doi:10.1016/j.jcrc.2018.01.005

Cited by 17 publications

(17 citation statements)

References 20 publications

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“…The effect of PEEP on dead space is diverse and complicated in ARDS patients. On the one hand, the size of dead space had been used to detect lung collapse and optimize PEEP level after recruitment [29,30], which was consistent with our [32]. Both studies shared the same drawback that no regional dead space could be evaluated.…”

Section: Discussionsupporting

confidence: 82%

Influence of overdistension/recruitment induced by high positive end-expiratory pressure on ventilation–perfusion matching assessed by electrical impedance tomography with saline bolus

Chi

Long

et al. 2020

Crit Care

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Background High positive end-expiratory pressures (PEEP) may induce overdistension/recruitment and affect ventilation–perfusion matching (VQMatch) in mechanically ventilated patients. This study aimed to investigate the association between PEEP-induced lung overdistension/recruitment and VQMatch by electrical impedance tomography (EIT). Methods The study was conducted prospectively on 30 adult mechanically ventilated patients: 18/30 with ARDS and 12/30 with high risk for ARDS. EIT measurements were performed at zero end-expiratory pressures (ZEEP) and subsequently at high (12–15 cmH2O) PEEP. The number of overdistended pixels over the number of recruited pixels (O/R ratio) was calculated, and the patients were divided into low O/R (O/R ratio < 15%) and high O/R groups (O/R ratio ≥ 15%). The global inhomogeneity (GI) index was calculated to evaluate the ventilation distribution. Lung perfusion image was calculated from the EIT impedance–time curves caused by 10 ml 10% NaCl injection during a respiratory pause (> 8 s). DeadSpace%, Shunt%, and VQMatch% were calculated based on lung EIT perfusion and ventilation images. Results Increasing PEEP resulted in recruitment mainly in dorsal regions and overdistension mainly in ventral regions. ΔVQMatch% (VQMatch% at high PEEP minus that at ZEEP) was significantly correlated with recruited pixels (r = 0.468, P = 0.009), overdistended pixels (r = − 0.666, P < 0.001), O/R ratio (r = − 0.686, P < 0.001), and ΔSpO2 (r = 0.440, P = 0.015). Patients in the low O/R ratio group (14/30) had significantly higher Shunt% and lower VQMatch% than those in the high O/R ratio group (16/30) at ZEEP but not at high PEEP. Comparable DeadSpace% was found in both groups. A high PEEP caused a significant improvement of VQMatch%, DeadSpace%, Shunt%, and GI in the low O/R ratio group, but not in the high O/R ratio group. Using O/R ratio of 15% resulted in a sensitivity of 81% and a specificity of 100% for an increase of VQMatch% > 20% in response to high PEEP. Conclusions Change of ventilation–perfusion matching was associated with regional overdistention and recruitment induced by PEEP. A low O/R ratio induced by high PEEP might indicate a more homogeneous ventilation and improvement of VQMatch. Trial registration ClinicalTrials.gov, NCT04081155. Registered on 9 September 2019—retrospectively registered.

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Section: Discussionsupporting

confidence: 82%

Influence of overdistension/recruitment induced by high positive end-expiratory pressure on ventilation–perfusion matching assessed by electrical impedance tomography with saline bolus

Chi

Long

et al. 2020

Crit Care

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“…As a marker of gas exchange, V D /V T can be affected by changes in either alveolar ventilation or perfusion. Gogniat et al 26 reported that DP was only correlated to V D /V T when C RS decreased after an increase in PEEP, suggesting that a reduction in ventilation secondary to overdistention plays an important role in the relationship between V D /V T and lung mechanics. As such, an improvement in V D /V T measured using the Enghoff approach in response to increased PEEP might represent either an improvement in lung mechanics or a reduction in shunt.…”

Section: Discussionmentioning

confidence: 99%

Validity of Empirical Estimates of the Ratio of Dead Space to Tidal Volume in ARDS

2020

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BACKGROUND: The ratio of dead space to tidal volume (V D /V T) is a clinically relevant parameter in ARDS; it has been shown to predict mortality, and it determines the extent to which extracorporeal CO 2 removal reduces tidal volume (V T) and driving pressure (DP). V D /V T can be estimated with volumetric capnography, but empirical formulas using demographic and physiological information have been proposed to estimate V D /V T without the need of additional equipment. It is unknown whether estimated and measured V D /V T produce similar estimates of the predicted effect of extracorporeal CO 2 removal on DP. METHODS: We performed a secondary analysis of data from a previous clinical trial including subjects with ARDS in whom V D /V T and CO 2 production (_ V CO 2) were measured with volumetric capnography. The estimated ratio of dead space to tidal volume (V D,est /V T) was calculated using standard empiric formulas. Agreement between measured and estimated values was evaluated with Bland-Altman analysis. Agreement between the predicted change in DP with extracorporeal CO 2 removal as computed using the measured ratio of alveolar dead space to tidal volume (V Dalv /V T) or estimated V Dalv /V T (V Dalv,est /V T) was also evaluated. RESULTS: V D,est /V T was higher than measured V D /V T , and agreement between them was low (bias 0.05, limits of agreement-0.21 to 0.31). Differences between measured and estimated _ V CO 2 accounted for 57% of the error in V D,est /V T. The predicted reduction in DP with extracorporeal CO 2 removal computed using V Dalv,est /V T was in reasonable agreement with the expected reduction using V Dalv /V T (bias-0.7 cm H 2 O, limits of agreement-1.87 to 0.47 cm H 2 O). In multivariable regression, measured V D /V T was associated with mortality (odds ratio 1.9, 95% CI 1.2-3.1, P 5 .01), but V D,est /V T was not (odds ratio 1.2, 95% CI 0.8-1.8, P 5 .3

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“…Animal model studies have shown that mechanical ventilation causes airway dilation [7, 8]. Moreover, clinically, V d,an increasesin response to PEEP [1]. Although PEEP remained unchanged between the two study phases, the airway aeration before the alveoli at birth can cause airway dilation [9].…”

Section: Discussionmentioning

confidence: 99%

“…V T comprises anatomical dead space (V d,an , volume of the airway), alveolar V T (V A , volume of the alveoli), and apparatus dead space (V d,app , volume of devices). Dead space increases in acute respiratory distress syndrome and changes with the disease course and in response to positive end-expiratory pressure (PEEP) [1]. High dead space lowers V A and causes hypercapnia if ventilator settings are not changed.…”

Section: Introductionmentioning

confidence: 99%

Ventilated Infants Have Increased Dead Space and Lower Alveolar Tidal Volumes during the Early versus Recovery Phase of Respiratory Distress

et al. 2019

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Background: Few studies have reported the measurement of anatomical dead space (V d,an) and alveolar tidal volume (V A) in ventilated neonates with respiratory distress. Objective: The aim of this study was to determine the differences in V d,an and V A in ventilated infants between the early and recovery phases of respiratory distress using volumetric capnography (V cap) based on ventilator graphics and capnograms. Methods: This study enrolled twenty-five ventilated infants (mean birth weight, 2,220 ± 635 g; mean gestational age, 34.7 ± 3.3 weeks). We adjusted respiratory settings to maintain appropriate oxygenation and tidal volume (V T), and performed V cap based on waveforms of ventilator graphics and capnograms. V d,an and V A were measured in infants with respiratory disorders, immediately after intubation (early phase) and subsequently when they were clinically stable (recovery phase). Results: The early phase, with lower dynamic lung compliance, required a higher level of ventilator support, not positive end-expiratory pressure, than the recovery phase. There were significant differences between the early and recovery phases for V d,an

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Dead space analysis at different levels of positive end-expiratory pressure in acute respiratory distress syndrome patients

Cited by 17 publications

References 20 publications

Influence of overdistension/recruitment induced by high positive end-expiratory pressure on ventilation–perfusion matching assessed by electrical impedance tomography with saline bolus

Influence of overdistension/recruitment induced by high positive end-expiratory pressure on ventilation–perfusion matching assessed by electrical impedance tomography with saline bolus

Validity of Empirical Estimates of the Ratio of Dead Space to Tidal Volume in ARDS

Ventilated Infants Have Increased Dead Space and Lower Alveolar Tidal Volumes during the Early versus Recovery Phase of Respiratory Distress

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