Chest
Volume 64, Issue 3, September 1973, Pages 331-335
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Intermittent Mandatory Ventilation: A New Approach to Weaning Patients from Mechanical Ventilators

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Mechanical ventilatory support has become a prime mode of therapy for patients with acute respiratory insufficiency. Some patients who have had their ventilation controlled are difficult to wean from mechanical to spontaneous ventilation. We have developed a method of ventilatory support which allows the patient to breathe spontaneously as desired, but which also delivers a mechanical hyperinflation at regular preset intervals: intermittent mandatory ventilation (IMV). The mechanical hyperinflations can gradually be reduced in frequency until weaning is complete. We have used IMV to facilitate weaning from mechanical ventilation in over 50 patients. The case histories of six of these patients, who failed to wean with conventional techniques, are presented in detail. Our experience suggests that IMV is more efficient, safer, more readily accepted by the patient and, therefore, preferable to conventional ventilatory and weaning methods.

Section snippets

RATIONALE AND THEORETIC ADVANTAGES OF IMV

Intermittent mandatory ventilation decreases the complexity and amount of equipment required for mechanical respiratory support and subsequent weaning. With the IMV assembly, it is not necessary to switch equipment or to utilize a separate device to provide PEEP during weaning. In addition, the intricate and expensive sigh and assist mechanisms incorporated into many recently marketed ventilators are unnecessary. Weaning with IMV also lessens the necessity for ventilatory measurements, and

CASE 1

A 62-year-old woman with chronic obstructive lung disease sustained a fractured pelvis, clavicle, and second rib, a ruptured urinary bladder, laceration of the liver, and right-sided tension pneumothorax in an automobile accident. During induction of general anesthesia, she vomited and aspirated liquid gastric contents. She was given methylprednisolone sodium succinate (Solu-Medrol) 2 gm intravenously, and after operation her respirations were assisted with a volume-limited ventilator (MA-1,

COMMENT

The above six cases represent weaning problems of varying etiology. The first two patients had severe chronic obstructive pulmonary disease and resultant CO2 retention. Abrupt discontinuation of mechanical ventilation resulted in anxiety, tachypnea, and CO2 retention in both cases. The gradual discontinuation of mechanical ventilation with IMV was successful in both cases. The third, fourth and fifth patients developed hypoxemia when subjected to “Tee-piece” trials, but not with IMV and PEEP.

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Supported in part by an NIH Research Training Grant 5 T01 GM00427-12.

Manuscript received February 1; revision accepted March 29, 1973.

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