Introduction

The Valsalva manoeuvre is used in everyday clinical practice in the assessment of patients with urinary incontinence and pelvic organ prolapse. It is also an important part of research investigations which involve measurement of urethral mobility, pelvic floor descent and imaging studies of the pelvic floor. The degree of displacement of pelvic structures during straining will depend on the amount of intra-abdominal pressure generated by the Valsalva manoeuvre and may also be influenced by other factors, such as muscle contraction and fatigue, bladder and rectal filling and embarrassment. Generation of a maximum Valsalva effort is often encouraged or ‘coached’ by the investigator, and this repetitive straining may also have an effect on the movement characteristics of structures like the urethra. Standardising the Valsalva manoeuvre during perineal ultrasound measurement has been recommended by European urogynaecology associations [1].

Previous studies have shown that there is substantial variation in the intra-abdominal pressures generated by the Valsalva manoeuvre. This appears to be the case when either a maximum achievable Valsalva is used (16–137 cmH2O) [2] or a standardised verbal instruction is given (16–126 cmH2O) [3]. These are important observations because many research studies use the Valsalva manoeuvre as a standard against which other measurements are made.

The potential to reduce this variation in intra-abdominal pressure between subjects has been reported in pilot studies using a simple airflow tube coupled with a valve release mechanism [4] and modified anaeroid sphygmomanometer [5]. These devices have been termed a ‘valsalvometer’. The aim of this investigation is to assess the potential of a modified valsalvometer to reduce the variation in intra-abdominal pressures between individuals and thereby attempt to standardise the Valsalva manoeuvre.

Materials and methods

This study was a prospective randomised controlled trial comparing the Valsalva manoeuvre with a novel device designed to produce a rise in intra-abdominal pressure. This research was carried out within a tertiary referral urogynaecology unit in the Northwest of England. Institutional ethics committee approval was obtained, and written informed consent was obtained from all participants prior to their taking part in the study. The population sampled was consecutive women referred to the unit for routine urodynamic studies who agreed to participate in the study. Hospital interpreters were available so that volunteers could participate whether or not they could understand English.

The device studied here for comparison against the Valsalva manoeuvre is referred to from now on as a valsalvometer. It consists of an adjustable flow restriction tube enclosed within a box with mouthpiece and exhaust tube. A pressure transducer within the system is set to trigger an audible beeping sound when a predetermined pressure threshold is reached. The audible beep signal was preset to a fixed pressure threshold for the duration of the study. An adjustable valve can alter the airflow resistance within the system. Unlike a standard Valsalva manoeuvre, the glottis remains open when the valsalvometer operates. The rise in intra-abdominal pressure occurs as a result of forced expiration against airflow resistance.

Intra-abdominal pressure was recorded by an air-filled rectal balloon linked to a pressure transducer. This method had been calibrated using a water column to ensure accuracy of measurement at the pressures attained during Valsalva manoeuvres. Each measurement was recorded three times in the semi-recumbent position. A standard verbal instruction shown below was read to each subject in order to carry out a Valsalva manoeuvre or use the novel device. The order in which each action was carried out was computer randomised.

Standardised verbal instruction

‘Please hold your breath and push down as if you are on the toilet.’

Valsalvometer verbal instructions

  1. 1.

    Make a good seal with your mouth around the tube.

  2. 2.

    Take a deep breath and blow into the device.

  3. 3.

    Blow as hard as you can for as long as you can.

  4. 4.

    Do not stop when you hear the beep.

The change in abdominal pressure was recorded by the urodynamic equipment computer monitoring the rectal pressure transducer (Lectromed 6000, Letchworth, UK). The pressure increase with verbal instruction Valsalva was recorded by analysing the computer data after urodynamics to find the maximum pressure attained. The pressures attained when subjects used the valsalvometer where recorded by staff ‘tagging’ the computer pressure recorder with a hand-held push-button pressed when the device beeping sound was heard.

Results

A total of 100 women participated in the study. One volunteer did not produce a measurable intra-abdominal pressure on the third verbal instruction Valsalva manoeuvre. Nine volunteers were not able to produce an adequate pressure to make the valsalvometer beep on all three requests.

Figure 1 shows the data for volunteers who performed a verbal instruction Valsalva manoeuvre first. The graph shows that each patient generates similar abdominal pressures for each of the three attempts at straining, i.e. there is little intra-individual variability (paired t test p>0.05). This occurs for both standard verbal instruction and valsalvometer. Figure 1 also shows that the pressures attained by the valsalvometer machine are generally lower than those reached during verbal instruction Valsalva manoeuvre. The use of the valsalvometer was associated with a reduction in standard deviation of approximately 50% when compared with standard verbal instruction.

Fig. 1
figure 1

Box-plot data for volunteers who carried out a verbal instruction Valsalva manoeuvre first (horizontal bar=median, box=values between 25th and 75th centile, ‘whiskers’ are highest and lowest values excluding outliers, ‘o’ indicates outliers from 1.5→3 box lengths from upper or lower edge of box, ‘*’ indicates extremes more than 3 box lengths from upper or lower edge of box)

Full size image

Figure 2 shows data for volunteers who used the valsalvometer first. Again each subject produces similar intra-abdominal pressures whether simple instruction or valsalvometer is used. There is little intra-individual variability. The use of the valsalvometer is associated again with a reduction in the variation of intra-abdominal pressure generated between individuals.

Fig. 2
figure 2

Box-plot data for volunteers who used the valsalvometer first (horizontal bar=median, box=values between 25th and 75th centile, ‘whiskers’ are highest and lowest values excluding outliers, ‘o’ indicates outliers from 1.5→3 box lengths from upper or lower edge of box, ‘*’ indicates extremes more than 3 box lengths from upper or lower edge of box)

Full size image

There is a difference in pressures obtained by verbal instruction (first manoeuvre only) which is dependent on the order of which set of actions are carried out (unpaired t test p<0.05). The pressures produced tend to be higher in the group who used the valsalvometer first. For this reason, the data are therefore reported in two parts, verbal instructions first and valsalvometer first.

Discussion

This investigation shows that the use of a valsalvometer to produce abdominal straining is associated with a reduction in inter-individual variability of the abdominal pressures produced during the Valsalva manoeuvre. The valsalvometer device therefore shows potential for generating a degree of standardisation of the rise in intra-abdominal pressures produced by individuals when performing the Valsalva manoeuvre.

It is possible however that the decrease in variability of pressure between individuals has occurred as a result of the reduction in peak intra-abdominal pressures achieved by the valsalvometer. In addition, it is not yet known whether the intra-abdominal pressures obtained when using the valsalvometer are likely to produce a significant and clinically measurable displacement of the pelvic organs. This may necessitate resetting the valsalvometer at a higher pressure setting and accepting that a higher proportion of patients will not be able to adequately complete using the device.

Further work will need to be carried out in order to characterise the shape of a pressure-displacement curve to establish whether a plateau is reached and whether hysteresis is present within the system. Accuracy may be improved by measuring prolapse at a point where there is maximal change in tissue movement per unit pressure. This is in agreement with other researchers who suggest that coaching subjects to produce a maximum Valsalva manoeuvre may be associated with lesser degrees of change in urethral excursion [6].

Conclusion

This investigation has shown that the valsalvometer device has the potential to reduce the variability in abdominal pressure between individuals when performing the Valsalva manoeuvre. Further work will confirm whether the intra-abdominal pressure increase produced with the valsalvometer device will be appropriate for measurement of pelvic organ movement in clinical practice.