Dynamic alveolar mechanics in four models of lung injury

DiRocco, Joseph D.; Pavone, Lucio A.; Carney, David E.; Lutz, Charles J.; Gatto, Louis A.; Landas, Steve K.; Nieman, Gary F.

doi:10.1007/s00134-005-2854-3

Cited by 45 publications

(44 citation statements)

References 32 publications

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“…Surfactant integrity would clearly play a pivotal role in this mechanism for recruitment/de-recruitment of alveoli, consistent with previous studies in which instability of alveoli was linked to the integrity of the surfactant (10,12,13,15). The results of a recently presented study indicate that alveolar instability is greater with low PEEP (5 cm H 2 O) and high tidal volume, while alveolar stability can be achieved with high PEEP (20 cm H 2 O) and low tidal volume (8).…”

Section: Discussionsupporting

confidence: 89%

“…The increase in open/recruited alveoli increases the stability of the lung. From this we hypothesize that subsequent cycles would progressively increase the stability of the alveoli until eventually the majority become stable and exhibit minimal change in size during tidal breathing, as postulated by Mead and coworkers (28) and shown by Nieman and colleagues (8,(10)(11)(12)(13)(14)(15)(29)(30)(31)(32) and Escolar and coworkers (19).…”

Section: Discussionmentioning

confidence: 70%

“…There have also been a substantial number of direct dynamic studies imaging the pleural surface aspect of alveoli using twodimensional in vivo video microscopy techniques (8)(9)(10)(11)(12)(13)(14)(15). These studies evaluate the alveolar dimensions as seen through the overlying pleural surface with the expected lack of detailed morphology and measurement.…”

mentioning

confidence: 99%

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Alveolar Dynamics during Respiration

Namati¹,

Thiesse²,

Ryk³

et al. 2008

Am J Respir Cell Mol Biol

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The change in alveolar size and number during the full breathing cycle in mammals remains unanswered, yet these descriptors are fundamental for understanding alveolar-based diseases and for improving ventilator management. Genetic and environmental mouse models are used increasingly to evaluate the evolution of disease in the peripheral lung; however, little is known regarding alveolar structure and function in the fresh, intact lung. Therefore, we have developed an optical confocal process to evaluate alveolar dynamics in the fresh intact mouse lung and as an initial experiment, have evaluated mouse alveolar dynamics during a single respiratory cycle immediately after passive lung deflation. We observe that alveoli become smaller and more numerous at the end of inspiration, and propose that this is direct evidence for alveolar recruitment in the mouse lung. The findings reported support a new hypothesis that requires recruitable secondary (daughter) alveoli to inflate via primary (mother) alveoli rather than from a conducting airway.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 70%

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Alveolar Dynamics during Respiration

Namati¹,

Thiesse²,

Ryk³

et al. 2008

Am J Respir Cell Mol Biol

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“…Although the lavage model does not encompass the pathophysiologic complexity of human ALI, it is likely to reflect several of its features, such as surfactant dysfunction (40,41), atelectasis (18), and edema (36,38). Addition of a detergent (19,21,39) allows the target hypoxemia to be reached with a lower volume of fluid than pure saline (34,35,41). More important, the detergent inactivates any surfactant produced after injury, affording the model to remain stable over time (19).…”

Section: Rationale and Critique Of The Experimentsmentioning

confidence: 99%

Relation between Shunt, Aeration, and Perfusion in Experimental Acute Lung Injury

Musch¹,

Bellani²,

Melo³

et al. 2008

Am J Respir Crit Care Med

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Rationale: In a pulmonary process characterized by spatially heterogeneous loss of aeration, the impairment of gas exchange is expected to depend on the regional distribution of perfusion relative to that of aeration. Objectives: To investigate how regional aeration, shunt, and perfusion are interrelated at different levels of end-expiratory pressure and how their interplay relates to global shunt fraction in acute lung injury. Methods: Regional shunt and perfusion were assessed by imaging with positron emission tomography the pulmonary kinetics of [ 13 N]nitrogen infused in saline solution in five sheep after lung lavage. The lung field was divided in six horizontal regions. Measurements and Main Results: Each animal showed an inverse relation between regional shunt (FS) and gas (FG) fractions: FS 5 2m Á FG 1 FS 0 . This relation was similar among animals (m 5 1.25 6 0.14, FS 0 5 0.75 6 0.15) and invariant with end-expiratory pressure, despite lack of correlation between global shunt and gas fractions and large interanimal variability in global shunt fraction. When this relation was used to estimate global shunt fraction as a perfusion-weighted average of the estimates of regional shunt fraction derived from regional gas fraction, 72% of the interanimal variability in global shunt fraction could be explained. Conclusions: Despite large interanimal variability in global shunt fraction, there was a consistent inverse relation between regional shunt and gas fractions, independent of end-expiratory pressure. Most of the interanimal variability in global shunt fraction could be explained by the combined effect of this relation and the distribution of perfusion on regional shunt, rather than by differences in global aeration.

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“…There have already been many studies that used experimental methods to optically track alveoli in mechanically ventilated animals, including the pioneering works of Nieman's group. [5][6][7][8][9][10][11] However, because the results of some of these studies are inconsistent, there is still the need for further observations. Hence, new methods for intravital imaging of subpleural alveoli have recently been presented.…”

Section: Introductionmentioning

confidence: 99%