Negative pressure pumps and related methods

A method of removing fluid from a target site, the method comprising:

• placing a first end of a manifold at the target site, wherein a second end of the manifold is coupled to a negative pressure pump comprising:
• a reservoir comprising an inner wall that defines a lumen along a longitudinal axis of the reservoir, the manifold being in communication with the reservoir;
• a drive assembly coupled to the reservoir and comprising a spring;
• and
• a piston coupled to the drive assembly, the piston having a cross-sectional dimension corresponding to a cross-sectional dimension of the reservoir;
• and
• initiating the drive assembly of the negative pressure pump, wherein motion of the spring moves the piston within the lumen to create a negative pressure within the reservoir.