When synchronized isn't synchronous- an experimental benchmarking study on the efficiency of SIMV in very-low-birth weight premature infants.

BACKGROUND: Synchronized ventilation promotes a patient's ability to breathe spontaneously by providing intermittent, mechanical-controlled respiration that is synchronized with the patient's own efforts. In "synchronized-intermittent-mandatory-ventilation" SIMV, assisted ventilation is regulated by frequency settings which dictate the interval at which the ventilator becomes sensitive to respiratory efforts and responds with an assisted breath. SIMV has become one of the most widely used modes of ventilation in neonates. Using a neonatal-active-lung-model (NALM), this in-vitro benchmark study investigated how well synchronization works in SIMV with several ventilators.

METHODS: The competence of eight ventilators was tested using a NALM simulator representing a preterm infant weighing approximately 1500 grams. Two conditions were explored: first, the ventilators were set to a constant ventilation rate, while the NALM was adjusted to frequencies equal to and below this ventilation rate. The second condition varied the ventilators' rates while the NALM frequency was held constant. Correctly triggered breaths were counted and displayed as a percentage (%) of the total potential triggerable breaths.

RESULTS: Performance among devices significantly differed, ranging from a low 38.9% competency to a max of 71.7% under the first condition, and 70.7% to 100% under the second condition.

CONCLUSIONS: At high SIMV frequencies, synchronization between the patient and ventilator becomes increasingly limited. Despite their identical ventilator functions, SIMV algorithms of the various manufacturers and models tested, deliver ventilation rates with significantly different degrees of synchronization; not only in comparison to each other, but also in their own ability to continuously and effectively synchronize breaths under variable conditions, typical of preterm lungs.