Existence and global attractivity of positive periodic solutions of a survival model of red blood cells

In this paper, we deal with a model for the survival of red blood cells with periodic coefficients, x(t)=−μ(t)x(t)+P(t)e−r(t)x(t−r(t)),t≥0. Some new sufficient conditions are obtained for the existence and global attractivity of positive periodic solutions of the equation.