3.2 Pressure-flow/volume analyses
In the cystometry, saline infusion into the pre-emptied bladder of
patients provoked a voiding (Figure 2A). The pressure-volume analysis
(PVA), which was established by plotting the detrusor pressure (Pdet)
against the intra-vesical volume (Vive), demonstrated the trajectory of
pressure-volume data moved counterclockwise and shaped an enclosed loop
representing a voiding cycle (Figure 2B). Four phases were identified in
the loop, namely (1) Filling (F; from the infusion began to the voiding
contraction onset): an increasing Vive in accompanied by a slightly but
progressively elevated baseline Pdet. (2) Iso-volumic contraction (IVC;
from the voiding contraction onset to the emission began): the bladder
contracted without fluid expulsion that resulted in an abruptly elevated
Pdet with a nearly constant Vive. (3) Emission (E; from the beginning to
the end of fluid emission): a plateau Pdet that slightly elevated at the
end of this stage with a marked Vive decrease. (4) Iso-volumic
relaxation (IVR; from the end of emission to the end of bladder
relaxation): the bladder relaxed without fluid expulsion that resulted
in a marked Pdet decline with an almost constant Vive.