Research
Alveolar instability caused by mechanical ventilation initially damages the nondependent normal lung
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* Corresponding author: Scott Albert albertsc@upstate.edu
1 Upstate Medical University, Department of Surgery, 750 E Adams Street, Syracuse, NY 13210 USA
2 Department of Biology, Cortland College, P.O. Box 2000 Cortland, NY 13045 USA
Critical Care 2007, 11:R104 doi:10.1186/cc6122
Published: 18 September 2007Additional files
A Windows media player file containing a movie showing normal alveoli ventilated at a Pcontrol of 14 cmH2O and a PEEP of 3 cmH2O. Individual alveoli fill the microscopic field and do not change size appreciably with ventilation. Note the blood flowing around and over the alveoli.
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A Windows media player file containing a movie showing alveolar instability in the nondependent low PEEP group 60 minutes following injurious ventilation. At end expiration there is a great deal of atelectasis, which appears as dark-red areas without the presence of alveolar structures. During inspiration, the collapsed alveoli reach the critical opening pressure and 'pop' open. When the critical closing pressure is reached during exhalation, the alveoli collapse. The mechanism of this collapse and re-expansion appears to be by alveolar folding and unfolding (Figure 5).
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A Windows media player file containing a movie showing that alveoli are stable and appear normal (Additional file 1) in the dependent lung with low PEEP 60 minutes following injurious ventilation.
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A Windows media player file containing a movie showing that alveoli are stable and appear normal (Additional file 1) with a high PEEP 90 minutes following injurious ventilation.
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A Windows media player file containing a movie showing a computer-assisted design rendition of the three-dimensional changes in alveolar volume over time (addition of the time element creates a four-dimensional representation). The alveolar mouth is highlighted in red. Note the large change in the size of the mouth and the minimal changes in the size of the other portions of the alveolus. When functioning together in an air sac, the change in alveolar mouth size results in a large change in the size of the alveolar duct [16].
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