This work presents an evaluation of IEEE 802.15.6 standard using CSMA/CA with polling, considering the priority in terms of the different contention window length for heterogeneous data traffic in healthcare monitoring. Data delivery time is crucial for timely assistance needed by the patient during emergency and threshold set for latency in medical application is 250 ms. Simulation has been done using Castalia 3.3 and OMNeT++ to analyse QoS parameters e.g. latency, energy consumption, packet received per node etc. for varying size, rate and priority of medical data traffic. The simulation results show that the increase in the slot length from 2 to 15 doubles the energy consumption. During emergency when the packet rate increases then œ 83% packets received by contention with polling at 100 packets/second/node for different priorities and slot lengths in compare to œ 20% packets received by contention without polling within the desired time limit for medical application.