Definition and clinical evaluation of a recruiting airway pressure based on the specific lung elastance in anesthetized dogs

Araos, Joaquín; Lacitignola, Luca; Acquafredda, Claudia; Bella, Caterina Di; Stabile, Marzia; Guacci, Erica; Gleed, Robin D.; Grasso, Salvatore; Crovace, Antonio; Staffieri, Francesco

doi:10.1016/j.vaa.2021.03.005

Cited by 7 publications

(8 citation statements)

References 25 publications

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“…Interestingly, the percentage of hypoaeration increases linearly with the percentage of body fat. Second, global lung strain and P awO are significantly higher during VTc, whereas global lung strain with VTi is similar to that described for lean dogs (19), suggesting a more physiologic tidal inflation during the latter. Third, although P plat is higher during VTc, elastances are not significantly different compared with VTi.…”

Section: Discussionsupporting

confidence: 71%

“…In humans, the accumulation of adipose tissue in the abdomen results in compression of the thorax with ensuing reductions in FRC (2). In the present study, the different elastances normalized to IBW where higher than those previously reported in populations of lean adult anesthetized dogs (19,25). In ventilated human patients, obesity is associated with increased E RS , explained mostly by an increase in the E L , and to a lesser extent by the E CW .…”

Section: Discussioncontrasting

confidence: 55%

“…In the present study, global volumetric lung strains were significantly lower during VTi compared with VTc. In fact, strains during VTi were comparable to a cohort of lean dogs (19), suggesting that in obese dogs, a protocol using VTi is more physiologic than VTc. The evaluation of regional lung strains in one dog revealed a wide range of values, suggesting that the determination of lung strain using global estimations can over, and more importantly, under estimate local strain values in this population.…”

Section: Discussionmentioning

confidence: 77%

“…The static mechanical properties were determined by applying 4-s end-inspiratory and end-expiratory airway occlusions at the time of end-inspiratory and end-expiratory CT imaging, respectively (19). Total end-expiratory pressure of the respiratory system (PEEP RS ) and of the chest wall (PEEP CW ) were measured as the plateau pressure in P aw and P ES , respectively, at the end of the expiratory pause.…”

Section: Respiratory System Mechanicsmentioning

confidence: 99%

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Evaluation of Lung Aeration and Respiratory System Mechanics in Obese Dogs Ventilated With Tidal Volumes Based on Ideal vs. Current Body Weight

et al. 2021

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We describe the respiratory mechanics and lung aeration in anesthetized obese dogs ventilated with tidal volumes (VT) based on ideal (VTi) vs. current (VTc) body weight. Six dogs with body condition scores ≥ 8/9 were included. End-expiratory respiratory mechanics and end-expiratory CT-scan were obtained at baseline for each dog. Thereafter, dogs were ventilated with VT 15 ml kg−1 based on VTi and VTc, applied randomly. Respiratory mechanics and CT-scan were repeated at end-inspiration during VTi and VTc. Data analyzed with linear mixed models and reported as mean ± SD or median [range]. Statistical significance p < 0.05. The elastance of the lung, chest wall and respiratory system indexed by ideal body weight (IBW) were positively correlated with body fat percentage, whereas the functional residual capacity indexed by IBW was negatively correlated with body fat percentage. At end-expiration, aeration (%) was: hyperaeration 0.03 [0.00–3.35], normoaeration 69.7 [44.6–82.2], hypoaeration 29.3 [13.6–49.4] and nonaeration (1.06% [0.37–6.02]). Next to the diaphragm, normoaeration dropped to 12 ± 11% and hypoaeration increased to 90 ± 8%. No differences in aeration between groups were found at end-inspiration. Airway driving pressure (cm H2O) was higher (p = 0.002) during VTc (9.8 ± 0.7) compared with VTi (7.6 ± 0.4). Lung strain was higher (p = 0.014) during VTc (55 ± 21%) than VTi (38 ± 10%). The stress index was higher (p = 0.012) during VTc (SI = 1.07 [0.14]) compared with VTi (SI = 0.93 [0.18]). This study indicates that body fat percentage influences the magnitude of lung, chest wall, and total respiratory system elastance and resistance, as well as functional residual capacity. Further, these results indicate that obese dogs have extensive areas of hypoaerated lungs, especially in caudodorsal regions. Finally, lung strain and airway driving pressure, surrogates of lung deformation, are higher during VTc than during VTi, suggesting that in obese anesthetized dogs, ventilation protocols based on IBW may be advantageous.

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Section: Discussionsupporting

confidence: 71%

Section: Discussioncontrasting

confidence: 55%

Section: Discussionmentioning

confidence: 77%

Section: Respiratory System Mechanicsmentioning

confidence: 99%

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Evaluation of Lung Aeration and Respiratory System Mechanics in Obese Dogs Ventilated With Tidal Volumes Based on Ideal vs. Current Body Weight

et al. 2021

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“…Moreover, global LS DYNAMIC was 24% on average and regional strains ranged lower than during ZEEP, from 6 to 40%. A recent study in obese dogs ventilated with similar V T and ZEEP showed that while global LS DYNAMIC was 38% in one dog, some regions developed local TS DYNAMIC levels in excess of 150% (34).…”

Section: Discussionmentioning

confidence: 94%

Distribution and Magnitude of Regional Volumetric Lung Strain and Its Modification by PEEP in Healthy Anesthetized and Mechanically Ventilated Dogs

et al. 2022

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The present study describes the magnitude and spatial distribution of lung strain in healthy anesthetized, mechanically ventilated dogs with and without positive end-expiratory pressure (PEEP). Total lung strain (LSTOTAL) has a dynamic (LSDYNAMIC) and a static (LSSTATIC) component. Due to lung heterogeneity, global lung strain may not accurately represent regional total tissue lung strain (TSTOTAL), which may also be described by a regional dynamic (TSDYNAMIC) and static (TSSTATIC) component. Six healthy anesthetized beagles (12.4 ± 1.4 kg body weight) were placed in dorsal recumbency and ventilated with a tidal volume of 15 ml/kg, respiratory rate of 15 bpm, and zero end-expiratory pressure (ZEEP). Respiratory system mechanics and full thoracic end-expiratory and end-inspiratory CT scan images were obtained at ZEEP. Thereafter, a PEEP of 5 cmH2O was set and respiratory system mechanics measurements and end-expiratory and end-inspiratory images were repeated. Computed lung volumes from CT scans were used to evaluate the global LSTOTAL, LSDYNAMIC, and LSSTATIC during PEEP. During ZEEP, LSSTATIC was assumed zero; therefore, LSTOTAL was the same as LSDYNAMIC. Image segmentation was applied to CT images to obtain maps of regional TSTOTAL, TSDYNAMIC, and TSSTATIC during PEEP, and TSDYNAMIC during ZEEP. Compliance increased (p = 0.013) and driving pressure decreased (p = 0.043) during PEEP. PEEP increased the end-expiratory lung volume (p < 0.001) and significantly reduced global LSDYNAMIC (33.4 ± 6.4% during ZEEP, 24.0 ± 4.6% during PEEP, p = 0.032). LSSTATIC by PEEP was larger than the reduction in LSDYNAMIC; therefore, LSTOTAL at PEEP was larger than LSDYNAMIC at ZEEP (p = 0.005). There was marked topographic heterogeneity of regional strains. PEEP induced a significant reduction in TSDYNAMIC in all lung regions (p < 0.05). Similar to global findings, PEEP-induced TSSTATIC was larger than the reduction in TSDYNAMIC; therefore, PEEP-induced TSTOTAL was larger than TSDYNAMIC at ZEEP. In conclusion, PEEP reduced both global and regional estimates of dynamic strain, but induced a large static strain. Given that lung injury has been mostly associated with tidal deformation, limiting dynamic strain may be an important clinical target in healthy and diseased lungs, but this requires further study.

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Lung aeration and volumes following alveolar recruitment maneuvers with three airway pressures in healthy anesthetized and mechanically ventilated Beagle dogs

Araos

Sedgwick

Staffieri

et al. 2022

Veterinary Anaesthesia and Analgesia

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Definition and clinical evaluation of a recruiting airway pressure based on the specific lung elastance in anesthetized dogs

Cited by 7 publications

References 25 publications

Evaluation of Lung Aeration and Respiratory System Mechanics in Obese Dogs Ventilated With Tidal Volumes Based on Ideal vs. Current Body Weight

Evaluation of Lung Aeration and Respiratory System Mechanics in Obese Dogs Ventilated With Tidal Volumes Based on Ideal vs. Current Body Weight

Distribution and Magnitude of Regional Volumetric Lung Strain and Its Modification by PEEP in Healthy Anesthetized and Mechanically Ventilated Dogs

Lung aeration and volumes following alveolar recruitment maneuvers with three airway pressures in healthy anesthetized and mechanically ventilated Beagle dogs

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