This work is about the feasibility of using slender elements combined with pneumatic chambers as support structural elements in temporary membrane structures applications. Spline term in this work refers to those straight and slender elements that are bent to form a continuous spatial curve and identical moment of inertia (second moment of area) about any axis perpendicular to its centroidal axis. It is common to use arches as supporting elements in membrane lightweight structures. There are very few applications of spline elements combined with membranes in medium - large span structures. Applications in small spans are more common for example in camping tent systems where spline elements are stiff enough to take external forces. For medium (16 - 32 m) span structures it is common that spline elements need in-plane bracing systems formed by masts and cables, in order to increase stiffness and strength properties to be able to bare real external forces (wind or snow). It is included the use of pneumatic chambers instead of mast-cables system in order to make spline arches stiff enough to withstand real external forces. Analytical models whereas realistic load conditions were developed using specialized software (EASY, RSTAB). Several configurations of size and position of pneumatic chambers were evaluated. Different materials and their properties were also analyzed to be adequate for spline element requirements. Additional vertical truss elements and cables were required to stabilize the hybrid arch. As a result of this work, it is demonstrated analytically that it is possible to use pneumatic chambers and additional vertical truss elements and cables to give enough stiffness to spline slender arches under real loading conditions. A basic detailing proposal for connections and erection process is presented.