Although humans have experimented with different models of lung ventilation, recent history of mechanical ventilation began during the polio epidemics of the 1940s and 1950s. Initially, there was the use of various forms of negative-pressure ventilation with the iron lung and chest cuirass, and then there was tracheostomy and intubation with positive-pressure ventilation. Mechanical ventilation has evolved to a complex and often controversial science. Many aspects of ventilation that have not been well documented in controlled studies have instead become community standards simply through experience and general use.

The first modern-day positive-pressure ventilators of the late 1940s were composed of a simple structure and valving systems. The mode of ventilation was not a choice, and the usual controls were simply the inspiratory pressure with a controlled respiratory rate. Even an Fi o₂ setting was not specific since oxygen was bled into the reusable rubber tubing. However, one objective has remained steady: to maintain the patient's ventilation and oxygenation until it can be effectively managed independently. This remains the positive outcome for which all practitioners strive.

This, then begins the controversy and ignites the stimulating debates over numerous and varied practice patterns. As practitioners (physicians, respiratory care practitioners, and nurses), we have not been satisfied to simply push positive-pressure into the airways and let exhalation passively occur. The phrase, primum non nocere, “First of all, do no harm,” has pressed practitioners to explore methods and practice patterns to undergo mechanical ventilation with the least work of breathing, to eliminate the incidents of barotrauma and airway damage, to minimize stress on the other body systems during ventilation, and to create as much comfort as possible to the patient connected to the breathing machine.

The main objective of this article is to explore various selection criteria of mechanical ventilators. It is primarily aimed toward a discussion of mechanical ventilators: evaluation guidelines and the overall purchase decision of the mechanical ventilator. To accomplish this, discussion cannot exclude ventilation modes available in practice. It also cannot ignore the valiant attempt at a move toward standardization by the American College of Chest Physician's published Mechanical Ventilation Consensus Conference<sup>30 Mechanical Ventilation American College of Chest Physicians Consensus Conference Chest 1993 ;  104 : 1833-1859

Haga clic aquí para ir a la sección de Referencias</sup> and the American Association of Respiratory Cares published “Essentials of Mechanical Ventilation.”<sup>1 AARC Document Consensus Statement on the Essentials of Mechanical Ventilation 1992 Respiratory Care 1992 ;  37 : 999-1008

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In the United States, the respiratory care profession emerged alongside the advent of mechanical ventilation. Their history paths are parallel, and it is hard to discuss one topic without mentioning the other. Typically, the purchase of mechanical ventilators has been with the Respiratory Care Departments. Since these departments in the past have been one of the revenue-generating departments of the acute care hospital, it was fairly easy to justify capital equipment costs to replace old equipment or expand the ventilator army. Because of reimbursement changes in our medical payment structure, the focus of these departments has shifted to become a cost center. Justification for the newest and best has had to also take a major shift. The decision-making process has to balance patient needs with technological advancements, efficiency of equipment, cost, and patient outcomes.