J Appl Physiol 104: 1233-1234, 2008;
doi:10.1152/japplphysiol.01226.2007b
8750-7587/08 $8.00
POINT-COUNTERPOINT
Rebuttal from Drs. Ferguson and Slutsky
Dr. Kacmarek summarizes animal studies putatively demonstrating no advantage of HFV over conventional ventilation (CV; Ref. 1). However, as he states, even his own study demonstrated that HFO produced less lung injury as assessed by interstitial hemorrhage and alveolar septal expansion than CV (4). Of greater concern, he neglected to cite other studies that demonstrate an advantage of HFV in acute lung injury, compared to conventional lung protective ventilation (1–3; 6). It is true that in the spirit of debate we did not cite the few studies showing equivalence; however, importantly, no studies have demonstrated conventional ventilation to be superior to HFO. Furthermore, recent data show that in patients with more severe ARDS, low tidal volume conventional ventilation can cause tidal overdistension, likely leading to increased ventilator-induced lung injury (5).
Kacmarek argues that HFO has been around since 1959 and still has not become the accepted physiological approach. This is not exactly correct—Emerson's patent deals with superimposing oscillations on conventional breaths, it was not high-frequency ventilation per se. In addition, a commercial HFO ventilator capable of ventilating adults has been FDA approved for fewer than 10 years. Conventional ventilation with large and small tidal volumes has been around for centuries, and yet definitive data that smaller tidal volumes are better was not provided until the year 2000. Kacmarek finishes his argument by stating that "optimally applied HFO does work but not any better than even poorly applied [emphasis is ours] CV"—that is certainly a stretch (no pun intended) and patently incorrect.
Kacmarek spends most of his argument demonstrating that there is very little clinical outcome data (i.e., mortality) supporting the use of HFO. As discussed (8), we are in agreement on this point—clearly more data from appropriately powered RCTs are required—but this was not the focus of this debate. The question posed was whether high-frequency ventilation was the optimal physiological approach to ventilate ARDS patients. Indeed, when he does discuss the physiology, Dr. Kacmarek is in total agreement with us on the physiological advantage of HFV compared with conventional ventilation. To quote him: "It is true that theoretically HFO should be more lung protective than CV. Tidal stretch is dramatically limited, tidal volume even in adults is only 1–3 ml/kg PBW and mean airways pressures are sufficient to avoid injury from recruitment/derecruitment"; we thank Dr. Kacmarek for so succinctly summarizing our position, and we rest our case.
REFERENCES
- Imai Y, Nakagawa S, Ito Y, Kawano T, Slutsky AS, Miyasaka K. Comparison of lung protection strategies using conventional and high-frequency oscillatory ventilation. J Appl Physiol 91: 1836–1844, 2001.[Abstract/Free Full Text]
- Muellenbach RM, Kredel M, Said HM, Klosterhalfen B, Zollhoefer B, Wunder C, Redel A, Schmidt M, Roewer N, Brederlau J. High-frequency oscillatory ventilation reduces lung inflammation: a large-animal 24-hour model of respiratory distress. Intensive Care Med 33: 1423–1433, 2007.[CrossRef][Web of Science][Medline]
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- Terragni PP, Rosboch G, Tealdi A, Corno E, Menaldo E, Davini O, Gandini G, Herrmann P, Mascia L, Quintel M, Slutsky AS, Gattinoni L, Ranieri VM. Tidal hyperinflation during low tidal volume ventilation in acute respiratory distress syndrome. Am J Resp Crit Care Med 175: 160–166, 2007.[Abstract/Free Full Text]
- Von der Hardt K Kandler MA, Fink L, Schoof E, Dotsch J, Brandenstein O, Bohle RM, Rascher W. High frequency oscillatory ventilation suppresses inflammatory response in lung tissue and microdidepleted piglets. Pediatr Res 55: 339–346, 2004.[CrossRef][Web of Science][Medline]
Copyright © 2008 by the American Physiological Society.
