Ventilator-induced diaphragm dysfunction: time for (contr)action!
Authors: Ghislaine Gayan-Ramirez
Journal: European Respiratory Journal (2013)

New studies indicate that diaphragm pacing techniques could protect against ventilator-induced diaphragm injury http://ow.ly/kTvSoDuring the past 10 years, intensive experimental research has focused on the effects of mechanical ventilation on the diaphragm.Whatever the animal species studied, all these studies have consistently shown that mechanical ventilation impaired diaphragm function, resulting in the so-called ventilatorinduced diaphragm dysfunction (VIDD) [1][2][3][4][5][6][7][8][9].The development of this effect is rapid and worsens with the time spent on the ventilator [5].It is associated with early diaphragm fibre atrophy leading, ultimately, to diaphragm weight loss and to diaphragm ultrastructural alterations, with disorganisation of the sarcomere's architecture [8].Oxidative stress, decreased protein synthesis and increased proteolysis have been all reported in the diaphragm after mechanical ventilation [8].These data revealed that a healthy diaphragm was made diseased after mechanical ventilation.For a long time, the importance of these data has been neglected, probably because of the experimental nature of the studies.But the study of LEVINE et al. [10] in ventilated brain-dead organ donors, which revealed rapid diaphragm fibre atrophy and enhanced proteolysis, as in animal models, highlighted the fact that the mechanical ventilation effect was not exclusive to laboratory models.Subsequent studies in animal models, and also in humans, have further documented the impact of controlled mechanical ventilation on the diaphragm [11][12][13][14][15][16][17][18][19][20].Despite this evidence, the impact of VIDD as an important component of diaphragm disability during mechanical ventilation remains questioned.It has been claimed that the available data pertain to controlled mechanical ventilation, a ventilation mode which is not the preferential mode of ventilation in patients.Well, this is true, although this ventilation mode is a necessary tool in particular situations (e.g. in patients treated with neuromuscular blocking agents, in attempts to minimise oxygen consumption, and in patients with central neurological problems) and is therefore still being used in the intensive care unit [21].But other ventilation modes may not be as innocent as it is believed.Experimental data showed that 3 days of assist-control mechanical ventilation in healthy animals resulted in about 15% loss in maximal diaphragm force, which is obviously far less than the 45% reduction seen with controlled mechanical ventilation [22], but still indicative that it is also harmful.Along the same lines, pressure support ventilation that did not affect diaphragm proteolysis or synthesis, in contrast to controlled mechanical ventilation, induced as much diaphragmatic oxidative stress as controlled mechanical ventilation did [23].Because the debate on whether VIDD is a myth or a reality is still going on, little has been done to develop strategies to minimise these effects, except for the use of pharmacological agents in experimental models of healthy animals [24][25][26][27].But we can do more and in this issue of European Respiratory Journal, MASMOUDI et al. [28] present preliminary original and provocative results that indicates it is time for (contr)action.The