A system (100) for simulating a fluid flow condition within a fluid carrying body cavity includes an elastically deformable bladder (101) simulating the body cavity and mounted to the body of a patient simulator manikin (3). An inlet tube (102) communicates a pressurised fluid supply (1) with the bladder (101). A solenoid valve (103) enables/disables flow of fluid through the inlet tube (102). The solenoid valve (103) is controlled by a control means (2) based on the simulated fluid flow condition. An inlet flow restrictor (106) restricts flow of fluid through the inlet tube (102). An outlet flow restrictor (105) is associated with an outlet (104) for restricting flow of fluid through the outlet to atmosphere. A simulator is also disclosed comprising a manikin (3) and various fluid flow simulation systems associated with the manikin (3) for simulating a lung respiratory rate, blood pulse rate and blood pressure.