Received: 24 September 2014
/Accepted: 27 November 2014 /Published online: 20 December 20
Elizabeth Lewis, PT, OCS, WCS
Oct 14, 2015
Pelvic Physical Therapy Distance
Journal Club
Clinical
Question: What is known about any specific
functional activities and their impact on intra-abdominal pressure? Similar topic was discussed June 2013, see outline here. http://pelvicpt.blogspot.com/2013/06/activity-restrictions-after.html
Clinical
Bottom Line: IAP can be monitored in women
outside of a lab during functional activities of lift/carry and walking. Mean IAP increases with walking speed and the
most common ways of carrying a baby in a car seat (front, side or awkward
carry) had significantly higher associated IAP’s than back pack carry.
Description: Pelvic floor disorders, including POP, UI and FI affect
one in four women in the US. It is not
clear how IAP during daily activities predisposes women to new or recurrent PFM
disorders. Even so, there are many
sources of information that recommend women avoid heavy lifting or repetitive
strenuous exercise to avoid strain to soft tissue which lead to pelvic floor
disorders.
This study looked at how walking speed and
carrying technique affect IAP. They tested
the feasibility of monitoring IAP outside the laboratory environment with a
wireless intravaginal transducer and compared IAP during carrying 13.6 kg
(approximately 30 lb.: the weight of a 3 month old in a car seat) in six
different carrying positions while walking 100m and also while walking 400
meters at a slow, normal and fast pace (self-selected).
Study
Design: Cross sectional, Observational
Methods:
Forty-six healthy women ages 19-54
did the walking and lifting procedures in randomized order, while being
monitored with a wireless intravaginal pressure transducer. They (researchers) analyzed maximal peak IAP
and area under the curve (AUC) IAP. This
was developed because IAP changes with functional ambulatory activities can’t
be measured in a lab and can’t be measured by a balloon catheter (due to poor
dynamic response and restriction of mobility).
The protocol was conducted in 3
areas: an outdoor track, an indoor track and a large, indoor gym. Activity distances of 400 and 100m were
confirmed with a measuring wheel. Each
session lasted about 45 min. including breaks between trials. Lying and standing baseline IAP were
determined for each woman with quiet lying and standing for 30 s each, prior to
exercise. After baseline measurements,
400 m walking IAP was measured with slow, medium and quick speeds in randomized
order.
Then lifting/carrying activities
were measured, with the dependent variables being IAP and AUC IAP and the
independent variable was the manner in which the women carried the 13.6
kg.
Six ways of carrying were used and
carrying with a back pack was used as the basis of comparison with other
ways. IAP during carrying (vs lifting)
was the main activity due to carrying being a more sustained activity.
With the backpack full of the 13.6
kg weight, women picked it up off the floor, put it on their back using both
straps, walk at their self- selected pace for 100m then set down the pack.
The double arm hang involved
carrying 6.8 kg in each of two grocery bags,
Front carrying required holding the
13.6 kg in a pack on the front with both arms at waist level, Combination carry
with 6.8 kg in a grocery bag on dominant side carried on iliac crest and 6.8 kg
held on other side just above iliac
crest,
Awkward carry used an infant car
seat with a weight totaling 13.6 kg carried as they might normally, except not
a front carry.
Women walked 100 m with each of
these carries, done in random order, shifting sides as needed.
Walk, lift and carry activities were
timed and HR, bpm were recorded right afterward. In between activities, supine rests were done
to lower the HR to within 30 bpm of supine resting HR.
Sample
Selection: Inclusion: Healthy
women between 18 and 54 were recruited, Exclusion:
pregnant, < 6 months PP, within 3
months of an injury which could limit participation or if they self-reported a
vaginal bulge. (Women were tested
when not menstruating.)
Measurement:
The researchers developed and tested
a wireless intravaginal transducer in a proof of concept study and then
optimized the transducer and receiver for greater portability in this
study. In the first study, they
developed the wireless transducer to approximate IAP by measuring pressure in
the upper vagina. They found it to
correlate well with rectal balloon catheter measures during coughing and
Valsalva maneuvers.
The transducer includes a pressure
transducer, signal conditioner and wireless components all encapsulated in an
elastomeric capsule filled with silicone gel.
The women would insert the sterilized transducer after voiding, tape the
antenna to their abdomen put on a chest strap to measure their heart rate and
also wear the base station (wireless receiver with a micro-SD card).
The researchers analyzed the raw
data with custom Matlab software. They
divided the walking data into 30 sec. segments and took the 10 highest peaks
and averaged them for the maximal IAP.
Mean maximal IAP would be the average of all 40 peaks in the 4, 30 sec.
segments.
The lifting data were separated into
3 segments (see figure 2): lifting: 1st 10 seconds, carrying and
then setting down: last 10 seconds. One
maximal IAP was recorded for each pickup and set down and then used for the
population average. The mean maximal IAP
for the carry was taken from an average of 10 maximal peaks with 1 sec in
between each. AUC was taken from the
carry segment only. They then did statistical
analysis (see study for details).
Results:
Of the 49 enrolled, 46 women aged
19-54 completed the study, with an average age of 33.7 years. They had a BMI of 22.8 Kg/m2.
78% were nulliparous.
Mean IAP in supine was 11 and in
standing was 31.9 cmH20.
Mean Maximal IAP got progressively
higher with increased walking pace, (p.0001 by mixed model ANOVA). Table 1 and Figure 3 reflect this. Increased
speeds caused decreased times to complete the walk and so decreased AUC
measurements. But when they normalized
AUC to time (reflecting mean IAP), there was an increased AUC with increased
walking speed. During the self- paced
walking activities, IAP tended to stay steady (mean maximal IAP didn’t trend up
or down).
Lift and Carry results are in Tables
2 and 3. Table 2 shows carry comparisons.
Double arm and combination carry didn’t differ significantly from back
pack carry. But awkward, side and front
carries all were significantly higher than the control. Pick up and
put down peaks and averages are in Table 3 but they only give
descriptive statistics as they didn’t plan on doing comparisons with them.
Discussion
This study demonstrated IAP can be
monitored in women during lift/carry and walking activities outside of a lab.
The found that mean IAP increases with
increased walking speed. They used spline
(statistical) models to rule out instability of IAP over time and found that it
was stable for each participant over time.
They also found that the most common positions
PP women use to carry their babies in a car seat: front, side and awkward
carries, had significantly higher associated IAP’s than backpack carry. They surmise that these unequal load
distributions cause trunk muscle recruitment to stabilize and protect the spine
but that they also increase IAP during pick up, and carry. The lowest increases of IAP occurred during
double arm lift due to squatting and grabbing the handles vs “bending at the
hip” and lifting with the arms.
The highest pressures were during lift,
less with setting down and least with carry.
They found that the back pack carry,
which was their standard of comparison, turned out to have higher ranges of
IAP, possibly due to carrying it at a higher center of gravity than other positions.
Weaknesses
Pressures observed with walking/carrying
were less than with coughing or straining, but women spend much more time
walking/carrying than with short bouts of high IAP. It’s not known whether different patterns of
IAP affect the pelvic floor differently, if at al.
Placing the transducer in the upper
vagina correlates with rectal transducers.
But, there is uncertainty about the measurement because it is indirect
and can be affected by viscera, vaginal smooth muscle contractions, etc.
Their subjects were young and healthy,
so the pressures measured can’t be generalized to older, less active or
immediate postpartum women.
Strengths
They said their study’s strengths were
the randomization of walking and lift and carry trials, the use of spline
models to determine whether IAP drifts over the time and the use of valid novel
technology to assess IAP in community settings.
They concluded that it’s not likely that
there’s a single threshold of IAP that increases risk for PFD. Also, it’s not clear that IAP changes with
walking speed or carrying toddler sized loads actually increase risk of PFD.
However, they conclude that it’s prudent
to limit time doing higher IAP activities during high risk times (such as
postpartum or postoperatively).
They recommend, due to their results,
that patients evenly distribute their loads and limit fast walking in the
immediate postoperative period. They
also recommend research to redesign heavy appliances such as car seats, to help
postpartum women have lower IAP.
Questions
1)
How might you
analyze this study, based on the previous Systematic
review: how did it fare in terms of the recommendations given in that study?
2)
Would you use
this information to make any particular recommendations in your practice?
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