Introduction/Background A key requirement of high-fidelity simulation is mechanical ventilation in critical care areas such as the intensive care unit. There is an unmet need to improve lung mechanics when using the SimMan 3G (Laerdal, Norway) patient simulator with modern critical care ventilators. Critical care ventilators are able to make use of a variety of complex ventilation modes (e.g., pressure control, volume control, pressure support) and incorporate positive end-expired pressure. We compared the SimMan 3G’s lung system with the lung mechanics of two other lung simulators that are sometimes used in conjunction with teaching critical care ventilation. We investigated how modifications to the lung system on the SimMan 3G would enable compatibility over a broad range of critical care ventilation modes. Methods We first compared the lung mechanics of the unmodified SimMan 3G with those of the Michigan Training and Test Lung (TTL, Michigan Instruments, Grand Rapids, MI), and the Siemens Lung Simulator. The Esprit ventilator (Philips Medical, Carlsbad, CA) was used to ventilate each of these lung simulation systems the Michigan TTL, SimMan 3G and the Siemens 920 for a variety of ventilation modes, tidal volumes, respiratory rates, and PEEP levels while the NICO® monitor (Philips, Wallingford, CT) recorded the lung mechanics parameters. Normal lung mechanics were defined as those observed with the Michigan TTL, set to have normal resistance (approximately 3 cm H2O l-1sec-1) and normal compliance (approximately 50 mL/cm H2O). We then made modifications to the SimMan® 3G by adding 650 grams of weight to the top of each lung plate and eliminating the elbow connectors on the small tubing between the chest walls and the lungs in order to slightly reduce airway resistance. We retested the modified lungs using the same ventilation modes. During volume controlled ventilation with normal tidal volume, compliance and resistance settings and zero PEEP, the unmodified SimMan 3G performs acceptably, though resistance is above normal and compliance is below normal. However, we observed high peak inspiratory and plateau pressures during many settings of critical care ventilation for the Siemens 920 and the SimMan® 3G which resulted in high pressure alarms from the ventilator. Large tidal volumes (> 700 mL) pose a challenge for both simulators, especially with PEEP > 0cm H2O. After modifications to the SimMan 3G lung were made, PEEP set to 0-10 cm H2O, tidal volume up to 1000 mL, and high inspiratory flow were compatible in most cases. Results: Conclusion We suggest that for critical care ventilation scenarios, the simulation experience can be improved for the SimMan 3G if 650 grams of weight is added to each of the lung plates and the elbow connectors on the small tubing between the chest walls and the lungs are removed. With these modifications, standard ventilation modes without the use of PEEP remains acceptable, albeit at slightly elevated pressures compared to the unaltered lungs. Our modifications and Results may compliment the prior work performed by other groups who made modifications to the SimMan 3G lung system.1