Maximum inspiratory and expiratory pressures in the pre and postoperative periods of patients with incisional abdominal hernia corrected by Lázaro da Silva technique

Objective: To verify the effect of longitudinal abdominal incisional herniorrhaphy on respiratory muscle pressure. Method: The technique of incisional herniorrhaphy used was proposed by Lázaro da Silva. To measure the pressure, we used a water manometer in 20 patients, median age 48.5 years (range 24 70). We analyzed the maximum inspiratory pressure at the level of residual volume (IP-RV) and functional residual capacity (IP-FRC) and the maximum expiratory pressure of functional residual capacity (EP-FRC) and total lung capacity (EP-TLC) in the preoperative and late postoperative (40 90 days) periods, in 13 patients with large incisional hernias and in 7 patients with medium incisional hernias. Results: There was a significant increase in IP-FRC (p = 0.027), IP-RV (p = 0.011) and EP-TLC (p = 0.003) in patients with large incisional hernias. EP-FRC increased, but not significantly. In patients with medium incisional hernias, the changes were not significant. Conclusion: Surgical correction of large incisional hernias improves the function of the breathing muscles; however, surgery for medium incisional hernias does not alter this function.


INTRODUCTION
A bdominal incisional hernia is a relatively common surgical disease, with an estimated incidence of around 15-20% of all laparotomies 1 . Without treatment, it tends to increase progressively and complicate with incarceration 2,3 , obstruction, strangulation 4 , deviation of the lumbar spine with low back pain, skin ulcer, skin infection, hernia rupture 2 , loss of domain 5 , muscle changes 6 , circulatory changes 6 , respiratory failure 7 , and tends to worsen patients' quality of life 8,9 . Respiratory dysfunction has been attributed to diaphragmatic dysfunction and the lack of normal action of abdominal muscles that are anatomically poorly positioned. When the incisional hernia is corrected, with anatomical restoration of the abdominal wall muscles, diaphragmatic repositioning occurs, with consequent improvement in the function of the breathing muscles.
In an initial study 10 , one of the authors analyzed only the pressure of the breathing muscles at the level of functional residual capacity (volume of air remaining in the lung after normal expiration). The pressures generated by the muscles of the large and medium hernias were not compared, nor were reported the pressures generated from residual volume (volume of air left in the lung after forced expiration) and total lung capacity (maximum volume of air left in the lung after deep inspiration), which can generate other types of results. In view of this issue, we carried out the present study.
The objective was to verify the maximum respiratory pressure in patients with large and medium longitudinal abdominal incisional hernias, before and after surgical correction, in different lung volumes, and the effect of surgery on these pressures.

Original article
Danilo nagib Salomão Paulo, ECbC-ES 1,2 ; alCino lázaro Da-Silva, ECbC-mg 3 ; luCaS nagib lEmoS Paulo 4 ; alExanDrE olioSi Caliman 2 ; marCEla Souza lima Paulo 5 ; mathEuS nagib lEmoS- Paulo 6 A B S T R A C T Objective: To verify the effect of longitudinal abdominal incisional herniorrhaphy on respiratory muscle pressure. Method: The technique of incisional herniorrhaphy used was proposed by Lázaro da Silva. To measure the pressure, we used a water manometer in 20 patients, median age 48.5 years (range 24 70). We analyzed the maximum inspiratory pressure at the level of residual volume (IP-RV) and functional residual capacity (IP-FRC) and the maximum expiratory pressure of functional residual capacity (EP-FRC) and total lung capacity (EP-TLC) in the preoperative and late postoperative (40 90 days) periods, in 13 patients with large incisional hernias and in 7 patients with medium incisional hernias. Results: There was a significant increase in IP-FRC (p = 0.027), IP-RV (p = 0.011) and EP-TLC (p = 0.003) in patients with large incisional hernias. EP-FRC increased, but not significantly. In patients with medium incisional hernias, the changes were not significant.  To measure the inspiratory and expiratory pressures, the test was conducted with the following guidelines 10 : -the patient was keep in an orthostatic position; -the smaller plastic tube with the disposable tube was perfectly adapted to the patient's mouth, to prevent air escape or inflow during the examination; -Next, we instructed the patient to breathe normally and, after maximum expiration, to take forced inspiration. -Hence, the water column descended from zero towards the ground; we thus obtained the inspiratory pressure at residual volume We repeated the pressure measurements until we obtained values that fulfilled the following criteria 10 : the efforts were theoretically perfect, that is, there were no leaks and the maximum pressure reached during the maneuver was maintained for at least one second; the two values obtained had, among themselves, a variation of, at most, 10%; the maximum value obtained was not the last in the series; the individual did not consider himself/herself capable of making a better effort.
We treated the results with the Wilcoxon's nonparametric test for related samples. All tests were twotailed. We considered a value of p<0.05 as significant. Table 1 Figures 2 and 3).

DISCUSSION
Unlike spirometry, which analyzes lung volume and flows, manometry analyzes the pressure generated by the respiratory muscles. Theoretically, the greater the pressure generated by the respiratory muscles, the greater the lung volume and flows, as long as there is no respiratory obstruction or any other factor that might interfere in this correlation. This is a fact that needs scientific proof with a good level of evidence.
This study evaluated the respiratory pressures with a water manometer. The technical realization of pressure tests with it has already been described 10 .
Although It is important to remember that the herniorrhaphy technique used in this work was proposed by Lázaro da Silva, one of whose advantages is the restoration of the linea alba 10,12 , which is associated with improved abdominal wall function. The analysis of the function of the rectus muscle with the dynamometer showed a significant improvement in isokinetic and isometric measurements, all of which were associated with improved quality of life 15 .
We should note that in large incisional hernias, there is also a lowering of the diaphragm and a decrease in the area of apposition of this muscle, which prevents it from exercising its normal action 10

CONCLUSION
Surgical correction of large incisional hernias improves the function of breathing muscles. However, surgery for medium incisional hernia does not alter this function.