MRI protocol for critically ill patients

BACKGROUND Ventilators compatible with magnetic resonance imaging machines are not universally available. However, the lack of such equipment should not preclude magnetic resonance imaging. We have developed a method by which a critically ill patient requiring mechanical ventilation can safely undergo such imaging without compatible equipment. METHOD By using extended ventilator tubing and calculating volume lost due to tubing compliance, safe and reliable mechanical ventilation can be achieved from a distance without impairing scan quality. RESULTS We devised a method to calculate volume lost due to mechanical compliance of the tubing with ventilator circuits employing 20, 30, and 50 feet of tubing. We added the estimated loss of volume to the set tidal volume of 700 mL to give a delivered volume of 700 mL. Twenty breaths were evaluated for each length of tubing. The evaluation of the 20- and 30-foot lengths of tubing demonstrated 10- and 52-mL discrepancies, respectively, between predicted and measured volumes. The 50-foot length showed a 121-mL discrepancy between predicted and measured volumes. CONCLUSIONS Our method appears to be clinically accurate for predicting volume lost due to tubing compliance for lengths of ventilator tubing less than or equal to 30 feet. We have found this technique to be a safe and effective way to ensure patient safety and scan quality in patients requiring mechanical ventilation during magnetic resonance imaging.