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Friday, August 12, 2011

Benetti TH, Santos MF, Mergulhao MEA, Fagundes JJ, Ayrizono MJS, Coy CSR: Variation of the Anal Resting Pressure Induced by Postexpiratory Apnea Effort in Patients with Constipation. Arq Gastroenterol 2011; 48(1):30-5.

August 10, 2011 Michelle Spicka

Objective:  
To analyze, by manometric data, the anal pressure variation at rest, during evacuation effort by using the Valsalva maneuver and forced post-expiratory apnea in subjects with secondary constipation.

Introduction:
1.  Functional evacuation disorders that lead to constipation are not completely understood (dyskinesia of the pelvic floor) but functional change is common (though underestimated) as a cause of chronic constipation and studies report that 50% of individuals suffer from constipation.
                a. Dyskinesia of the pelvic floor is characterized by difficulty initiating the evacuation and
sensation of incomplete evacuation secondary to failure of relaxation of the puborectal and external anal sphincter or contraction of those muscles during evacuation.
b. The observation that the Valsalva, used by some patients at the end of the evacuation effort, could be an aggravating favor of constipation led to this study to compare this variable with apnea after forced expiration.
c. Patients with dyskinesia of the pelvic floor tend to have decreased rectal sensitivity and muscular incoordination during the act of evacuation, showing an unconscious paradoxical contraction, exacerbated by the Valsalva.


Study Aim:
 
To evaluate the variation of anal canal pressure in patients with constipation with (1) Valsalva maneuver and (2) forced postexpiratory apnea during evacuation effort.

Methods:
1. Subjects: Population of patients from a coloproctology outpatient clinic in Brazil; 21 patients with a diagnosis of constipation and elevation of the pressure values in relation to the resting value with the evacuation effort.  The Agachan score was used for clinical evaluation to determine qualification as “constipated” (Agachan et al., 1996);  average age= 47.5; 19 females http://www.ncbi.nlm.nih.gov/pubmed/8646957
                a. The study included patients whose Agachan’s score was greater or equal to 10
                b. Patients also had to demonstrate elevated anal pressure during evacuation effort (noted on manometry)
2. Anorectal manometry was utilized to correlate data and clinical observation
3. Parameters analyzed in this study were obtained by manometric analysis of the average anal resting pressure followed by evacuation effort with the Valsalva maneuver and return to rest, followed by evacuation efforts with post-expiratory apnea. Study is not totally descriptive of this technique but Michelle did some further investigation and it seem they had patients fully exhale, pause for 1 to 2 seconds.
a. Manometric variables were obtained in the proximal (1) and distal (2) regions of the anal canal. It is not stated which muscles they are measuring – EAS, IAS or puborectalis
            b. The analysis of variables was performed in conditions of rest (R), evacuation effort with the Valsalva (V) and evacuation effort with postexpiratory apnea (A).
4.  Parameters analyzed were:
            a. Average of resting anal pressure in the proximal and distal regions of the anal canal
b. Average of variation of the anal pressure due to the evacuation associated with the Valsalva maneuver in the proximal and distal regions of the anal canal
c. Average of variation of the anal pressure due to evacuation associated with post-expiration apnea in the proximal and distal regions of the anal canal
5. Statistical analysis:  Comparative analysis was carried out using the variables obtained during  different moments, in the proximal and distal anal canal, using descriptive statistics with values of averages, SD, minimum, medium and maximum values (ANOVA, p-value <0.05).

Results:
1. The analysis of the mean values of the anal pressure variation at rest evidenced difference between proximal and distal channels, independent of the moment and tendency to differ during moments Valsalva and apnea
                a. Resting anal pressure was lower in the proximal anal canal than the distal anal canal Does this mean the proximal canal was normal and the distal canal was high or does it mean the proximal canal was too low and distal canal was normal. In the article (pg 32) rest proximal is 51.24, distal rest pressure is 63.05.  Old CAPP manual says max ave resting pressure is 60 to 80, so maybe the distal pressure was normal and the results reflect a weakness of the puborectalis?   
2. The mean of values of the area under the manometric tracing curve showed differences between moments Valsalva and apnea, either at the proximal portion or at the distal portion of the anal orifice.
                a. Lower values were noted following apnea vs Valsalva

Discussion:
1. The authors found no similar studies rendering a comparative analysis impossible (with regards to Valsalva vs postexpiration apnea)
1. Fecal continence is acquired by a combination of competent anal sphincter, anorectal normal sensitivity, rectal capacity and appropriate compliance.
2. The action of the muscles of the pelvic diaphragm are also being considered in the mechanisms of continence, although their role is not fully known.
3. This study identified that the resting anal pressure is lower in the proximal anal canal than the distal anal canal
a. The authors concluded that the difference may be due to greater influence from the voluntary control of the pelvic muscles in the distal portion (which tend to remain in a state of contraction in patients with constipation by dyskinesia of the pelvic floor).
4. Other studies (Giannantoni , et al and Nagib, et al) have shown that during Valsalva there was a simultaneous contraction of the muscles of the pelvic floor (as demonstrated by significant increase in EMG activity and rectoanal pressure gradient
5. This study showed that the evacuation effort associated with the postexpiration apnea could induce the relaxation of the muscles of the pelvic floor during the evacuation, making it easier for patients with constipation to overcome dyskinesia of the pelvic floor.
a. This technique is simple to understand and apply.  The authors speculate that with constantly practiced, better sensory-motor awareness can occur in constipated patients and lead to clinical improvement.
b. Post-expiratory apnea could be related to the decrease of abdominal press, as well as lead to a relaxation of the muscles of the anal canal.

Conclusion:
The effort of evacuation associated with postexpiratory apnea, when compared with the effort associated with the Valsalva maneuver, provides lower elevation of anal pressure at rest by the parameter area under the curve.
Thought Questions:
1. How can this information be applied to general down-training of the pelvic floor?  Can it be applied to generalized down-training of the pelvic floor? Important to remember that they measured pressure and we cannot completely translate that to EMG training.  It was agreed that there are still many questions and application to clinical practice still needs to be demonstrated. 
2. Can focusing on breathing mechanics alone affect pelvic floor tone and correct pelvic muscle dysfunction?
Ann Dunbar pointed out the information in the Sapsford book Women’s Health in which it discusses the contraction of the puborectalis and illiococcygeus during defecation.  No other literature was found with these thoughts.  It was also pointed out that abdominal bulging with bearing down seems to be more associated with PFM relaxation where abdominal inward contraction with bearing down would be associated with a PFM contraction.

Michelle pointed out she uses a straw or balloon with exhaling (on and off the toilet) to train PFM relaxation and feels the relaxation comes in the pause just after exhale and before e/ during inhale.

More Breathing-Pelvic Floor Connection:
1. (Strinic, et al 1997) found that decreased vital capacity and flow rates were noted in women with prolapsed pelvic organs
2. (Smith, Russell and Hodges 2006) found that women with disorders of continence and respiration have a significantly higher prevalence of back pain than women without those disorders.  Physiological data indicates that the postural function of the diaphragm, abdominal and pelvic floor muscles is reduced by incontinence or respiratory disease.
3. Pelvic floor muscles move away from mid zone with inspiration and returns to position with exhalation (Hodges 2008)
4. (Talasz et al 2010) observed a correlation between PFM contraction strength and forced expiratory flows may serve as theoretical background for a potential role of coordinated abdominal and PFM training in diseases with expiratory flow limitations.
5. (Talasz et al 2011) found in health women, real-time dynamic MRI demonstrates parallel cranio-caudal movement of the diaphragm and the PF during breathing, coughing and synchronous changes in abdominal wall diameter.  Both the diaphragm and the PF move caudally during inspiration and cranially during expiration.

 Talasz 2010 article abstract:  http://www.ncbi.nlm.nih.gov/pubmed/19997721
 Talasz 2011 article abstract:  http://www.ncbi.nlm.nih.gov/pubmed/20809211

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