DIFFICULTY OF WEANING FROM MECHANICAL VENTILATION

Abstract

After mechanical ventilation was introduced into clinical practice, there was a flurry of interest in developing newer modes of ventilation that would benefit patients with respiratory failure. This type of "more is best" approach was based on a perception that mechanical ventilation is a type of therapy for patients with respiratory failure. However, there is nothing therapeutic about mechanical ventilation. In fact, the most significant discovery about mechanical ventilation since it was first introduced is the fact that it damages the lungs (and indirectly damages other organs as well). Mechanical ventilation is a technique that opposes the normal physiology of ventilation (by creating positive pressure instead of negative pressure to ventilate the lungs) and, in this sense, it is not surprising that it is problematic. The current trend of using lower tidal volumes during mechanical ventilation is a step in the right direction because a "less is best" strategy is the only one that makes sense with a technique that is so unphysiological. The "less is best" strategy is currently advised only for patients with ARDS, but it seems likely that it will (and should) be adopted for all patients who require positive pressure ventilation. Since mechanical ventilation is a support measure and not a treatment modality, nothing that is done with a ventilator will have a favorable impact on the outcome of the primary illness. On the other hand, mechanical ventilation can have a negative impact on outcomes by creating adverse effects. This means that the best mode of mechanical ventilation is the one with the fewest adverse effects. It also means that, if we really want to improve outcomes in ventilator-dependent patients, less attention should be directed to the knobs on ventilators, and more attention should be directed at the diseases that create ventilator dependency. The rising popularity of non invasive ventilation tends to overshadow the value of endotracheal intubation, but because of hesitation invites trouble and endotracheal intubation is not the "kiss of death", the golden rule is " Don't Forget to Intubate". Reports that mortality is not increased by ventilator-associated pneumoniadeserve much more attention in discussions of how to manage pneumonia in the ICU. Because there is no gold-standard method for identifying ICU-acquired pneumonia other than post-mortem examination, it is possible that studies showing a lack of impact on survival included many false-positive diagnoses of pneumonia. The patient's clinical course in the first few days of mechanical ventilation will give us a fairly accurate indication of what is coming. If the patient is not improving, proceed to tracheostomy as soon as it can be done safely (Tracheostomies are more comfortable for patients, and they allow more effective airway care.) Most of the day-to-day management in the ICU is aimed at preventing other adverse events (such as pneumothorax), and remaining vigilant for adverse events so they can be treated or corrected quickly. In many cases, we are (unfortunately) not the ones controlling the course of the patient's illness.