Accuracy of the oxygen cylinder duration calculator of the LTV-1000 portable ventilator.

BACKGROUND Resource planning is essential for successful transport of the mechanically ventilated patient. Mechanically ventilated patients require adequate oxygen supplies to ensure transport is completed without incident. The LTV-1000 portable ventilator utilizes a program to calculate oxygen cylinder duration, based on cylinder size, fraction of inspired oxygen (F(IO(2))), and current minute ventilation. We evaluated the accuracy of the cylinder-duration algorithm in a laboratory setting. METHODS The LTV-1000 was attached to a test lung. Lung compliance was set at 0.04 L/cm H(2)O, and airway resistance was 5.0 cm H(2)O/L/s. We tested 7 different combinations of ventilator settings a minimum of 2 times each. With each setting, minute ventilation was kept at 10 L/min. Breath type, positive end-expiratory pressure, and F(IO(2)) were varied to evaluate the accuracy of the algorithm across a range of clinical scenarios. The cylinder-duration calculation from the ventilator program and manual calculation was determined at each setting and compared to the actual cylinder duration. RESULTS The ventilator algorithm and the manual calculation underestimated the actual cylinder duration by 12 +/- 3% with each test. The range of differences between calculated and actual cylinder duration was 2-26 min across the 7 conditions. CONCLUSION Actual cylinder duration averaged 12% longer than the cylinder duration estimated by the algorithm of the LTV-1000. One explanation is that the E cylinders may contain more liters of oxygen than indicated by the sticker on the side of the tank. Additionally, the bias flow during expiration is affected by inspiratory-expiratory ratio and respiratory rate. Clinicians should be aware of these differences when planning for patient transport.