Body sensor networks are emerging as a promising platform for healthcare monitoring. These systems are composed of battery-operated embedded devices which process physiological data. The reduction in the power consumption is an important factor to increase the lifetime for such systems and to enhance their wearability through reducing the size of the battery. In this paper, we develop an energy-efficient communication scheme that uses buffers to reduce the number of transmissions among the sensor nodes constrained to limited hardware resources. A direct acyclic graph is used to model the information flow. We define a communication optimization problem and solve it using convex optimization techniques. We present results that support the efficiency of the proposed technique.