Giuseppe
Emeritus
[Source: The New England Journal of Medicine, full page: (LINK). Extract, edited.]
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Editorial
High-Frequency Oscillatory Ventilation on Shaky Ground
Atul Malhotra, M.D., and Jeffrey M. Drazen, M.D.
January 22, 2013 - DOI: 10.1056/NEJMe1300103
Article
We thought it was impossible. Physiological principles maintained that ventilation at tidal volumes less than the anatomical deadspace should be ineffective (i.e., inspired air not reaching the alveolae). Data from a 1980 study dispelled that myth, showing unequivocally that ventilation with tidal volumes as small as 20 to 30 ml in dogs, a mere fraction of the anatomical deadspace, could maintain adequate ventilation.1 These unexplained observations sparked transport and mixing theories predicting that CO<SUB>2</SUB> removal should vary in direct proportion to breathing frequency (although the relationship with tidal volume is more complex2,3), and these predictions were later confirmed experimentally.4 Subsequent studies showed that CO<SUB>2</SUB> removal eventually reaches a plateau when the airways narrow during expiration, indicating the onset of expiratory-flow limitation. This concept is important, since portions of the lung can become hyperinflated dynamically (i.e., regional air trapping) beyond levels predicted from the applied mean airway pressure.5-7
(?)
-High-Frequency Oscillatory Ventilation on Shaky Ground
Atul Malhotra, M.D., and Jeffrey M. Drazen, M.D.
January 22, 2013 - DOI: 10.1056/NEJMe1300103
Article
We thought it was impossible. Physiological principles maintained that ventilation at tidal volumes less than the anatomical deadspace should be ineffective (i.e., inspired air not reaching the alveolae). Data from a 1980 study dispelled that myth, showing unequivocally that ventilation with tidal volumes as small as 20 to 30 ml in dogs, a mere fraction of the anatomical deadspace, could maintain adequate ventilation.1 These unexplained observations sparked transport and mixing theories predicting that CO<SUB>2</SUB> removal should vary in direct proportion to breathing frequency (although the relationship with tidal volume is more complex2,3), and these predictions were later confirmed experimentally.4 Subsequent studies showed that CO<SUB>2</SUB> removal eventually reaches a plateau when the airways narrow during expiration, indicating the onset of expiratory-flow limitation. This concept is important, since portions of the lung can become hyperinflated dynamically (i.e., regional air trapping) beyond levels predicted from the applied mean airway pressure.5-7
(?)
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