A fluid analysing system comprises: a pneumatic system for fluid analysis of expiratory and/or inspiratory breath, wherein said pneumatic system comprises a pneumatic manifold comprising: a connection interface for a fluid analyser unit; a connection interface for a pump unit ; and a buffer volume arranged between said connection interface for the fluid analyser unit and said connection interface for the pump unit, and wherein said buffer volume is configured to act as a constant flow cavity, a pump capacity improving cavity and as a ripple cancellation cavity; wherein said pneumatic system further comprises: a flow sensor and/or a pressure sensor; and a control unit; said fluid analysing system further comprising a pump unit connected to said connection interface for a pump unit; and a fluid analyser unit connected to said connection interface for a fluid analyser unit; wherein said control unit is configured to regulate a pump stroke force and/or pump frequency of said pump unit based on measurements from said flow sensor and said pressure sensor for obtaining a constant flow through said pneumatic system during a breath cycle with dynamic pressure, such as an inhale and/or an exhale. a pneumatic system for fluid analysis of expiratory and/or inspiratory breath, wherein said pneumatic system comprises a pneumatic manifold comprising: a connection interface for a fluid analyser unit; a connection interface for a pump unit ; and a buffer volume arranged between said connection interface for the fluid analyser unit and said connection interface for the pump unit, and wherein said buffer volume is configured to act as a constant flow cavity, a pump capacity improving cavity and as a ripple cancellation cavity; a connection interface for a fluid analyser unit; a connection interface for a pump unit ; and a buffer volume arranged between said connection interface for the fluid analyser unit and said connection interface for the pump unit, and wherein said buffer volume is configured to act as a constant flow cavity, a pump capacity improving cavity and as a ripple cancellation cavity; wherein said pneumatic system further comprises: a flow sensor and/or a pressure sensor; and a control unit; said fluid analysing system further comprising a pump unit connected to said connection interface for a pump unit; and a fluid analyser unit connected to said connection interface for a fluid analyser unit; wherein said control unit is configured to regulate a pump stroke force and/or pump frequency of said pump unit based on measurements from said flow sensor and said pressure sensor for obtaining a constant flow through said pneumatic system during a breath cycle with dynamic pressure, such as an inhale and/or an exhale. a flow sensor and/or a pressure sensor; and a control unit; said fluid analysing system further comprising a pump unit connected to said connection interface for a pump unit; and a fluid analyser unit connected to said connection interface for a fluid analyser unit; wherein said control unit is configured to regulate a pump stroke force and/or pump frequency of said pump unit based on measurements from said flow sensor and said pressure sensor for obtaining a constant flow through said pneumatic system during a breath cycle with dynamic pressure, such as an inhale and/or an exhale. <EOS>