عنوان مقاله [English]
Health Emergency Medical Service (HEMS) plays an important role in reducing injuries by providing advanced medical care in the shortest time and reducing the transfer time to advanced treatment centers. Injury and harm make sudden changes in the performance of body and organs. Most of these injuries can become serious without intervention, but they are resolvable with quick and in-time measures. Locating helicopter stations makes it possible and easier to transfer emergency patients to medical centers in regions without ground relief coverage. Emergency helicopter can pass directly between two points, cover vaster area, and have higher speed than ground ambulances; therefore, they can give better service to emergency injuries or injuries with limit access to hospitals. Some points are geographically mountainous or have high population density that disturb the helicopter landing process. Therefore, it seems critical to install helipads for successful implement of HEMS. Generally, there are three following assumed transfer modes: (1) Transferring patients directly to the hospital by ambulance from demand areas, (2) At first, moving patients to the helicopter station by an ambulance, then transferring them to a hospital by a helicopter deployed at the station, (3) Transferring patients to helipad by ambulance, then transferring them to the hospital by the helicopter. Subject to the uncertainty of incident points in the real world, in this paper, we assume that a demand occurs in a square demand area, and its length and width follows uniform distribution. The necessity of assuming demands in an area is to decrease errors, produced when the travelled distance between cities or facilities in the area is assumed as the distance between the areas's center points. In this paper, an integer nonlinear programming model has been presented for integrated locating of helicopter stations and helipads
considering uncertainty in demand points. The purpose of this model is minimizing the transfer time from demand points to hospital considering different modes. To evaluate the model, a simple numerical example has been presented, and its results have proved the HEMS system more advantageous in comparison with the traditional system. In addition, based on a case study, we
performed a study in Lorestan province, to establish optimum places for helipads and helicopter stations and allocate the type of each facility to demand regions.