Application of the projected isovolumetric pressure 1 in measuring detrusor contractility in females

Abstract

Objective To evaluate the application of the projected isovolumetric pressure 1 (PIP1)in measuring detrusor contractility in females.Methods Urodynamic parameters of 112 female patients were retrospectively analyzed.All the patients had undergone successful pressure-flow study,their age ranged from 18 to 84 years with a mean of 55 years.Fifty-eight patients suffered from lumbar disk herniation.The parameter PIP1 was calculated from the equation P_(det)Q_(max)+Q_(max)(with pressure in cm H_2O and Q_(max) in ml/s).Performed the correlation analysis between PIP1 and age,the maximum Watts factor(WF_(max)),the first sensation volume of the bladder,the maximum cystometric capacity.All the 112 patients were divided into the reduced PIP1 group(PIP1 less than 30 cm H_2O),the normal PIP1 group(PIP1 between 30 and 75 cm H_2O)and the elevated PIP1 group(PIP1 more than 75 cm H_2O).Fifty-eight patients with lumbar disk herniation were divided into the pre-operation group and post-operation group.The urodynamic parameters were statistically analyzed between these groups.Results The average PIP1 was(42.6±16.3)cm H_2O,the average P_(det) Q_(max )was(29.2±15.2)cm H_2O,the average Q_(max) was(13.3±7.3)ml/s,the average WF_(max) was(9.2±5.4)μW/mm~2 in all the 112 patients.Significant correlations were noted between PIP1 and age(r=0.343,P=0.000),PIP1 and WF_(max)(r=0.540,P=0.000).There were significant differences in age(P=0.006),P_(det) Q_(max),(P=0.000),Q_(max)(P=0.003),WF_(max)(p=0.000)among the reduced PIP1 group,the normal PIP1 group,and the elevated PIP1 group.In 58 patients with lumbar disk herniation,the average PIP1 was(44.4±14.2)cm H_2O and(35.4±13.5)cm H_2O,the average P_(det) Q_(max) was (29.3±13.2)cm H_2O and(23.6±11.2)cm H_2O,the average Q_(max) was(15.1±7.7)ml/s and (11.8±5.9)ml/s in the pre-operation and the post-operation group respectively.PIP1 was significant lower in the post-operation group compared with the pre-operation group(P=0.027),whereas no significant differences were found in P_(det) Q_(max)(P=0.114)and Q_(max)(P=0.122)between these 2 groups.Conclusions The parameter PIP1 is simple to calculate from a standard pressure-flow study and is useful for clinical assessment of detrusor contraction strength in females.PIP1 is correlated with age and WF_(max). Key words: Urodynamics; Pressure-flow study; Detrusor