4. Discussion
In the results obtained from this study, the spontaneous pushing associated with pursed lips breathing showed no difference for the occurrence of episiotomy, perineal lacerations, the duration of the second stage of labor, vaginal, Cesarean or instrumental delivery, when compared to directed pushing. There were no cases of postpartum hemorrhage and maternal blood pressure changes. However, there was a decrease in the duration of the maternal pushing and a difference in maternal anxiety in the spontaneous pushing group with pursed lips breathing. There was no difference in pain, fatigue, and maternal satisfaction. There were no events related to neonatal outcomes.
The expulsive stage is considered a strong indicator of long-term impairments of pelvic floor and bladder functions [18-22]. However, the present study showed no difference between the groups regarding episiotomy and perineal lacerations associated with the type of pushing, confirming the findings of a meta-analysis [2] comprised of five studies with 2.320 women in which no difference in episiotomy occurrence was observed RR 0,95; CI95% 0,87 to 1,04) as well as for grade 3 or 4 perineal lacerations (RR 0,94; CI95% 0,78 to 1,14), as analyzed from seven studies with 2.775 women. These data differ from a prospective cohort and a randomized clinical trial [22,23] published after that meta-analysis, which evidenced the association of directed pushing with VM maintained for 10 seconds or more with a significant increase in the number of episiotomies and grade 3 and 4 perineal lacerations [24].
It was hypothesized that the possible effects of pursed lips breathing would interfere directly in the pelvic floor muscles, since this exercise causes a change in the recruitment pattern of respiratory muscles, increasing the recruitment of accessory muscles of the chest wall and the activity of the abdominal muscles throughout the respiratory cycle, simultaneously decreasing the recruitment of diaphragmatic and pelvic floor muscles [25]. Therefore, one can conclude that the effect of that breathing pattern on pelvic floor muscles depends on the intensity of the abdominal muscles recruitment as the maneuver can be performed with a strong contraction of those muscles, depending on professional instruction and stimulus.
The intensity of abdominal muscles contraction will influence intra-abdominal pressure (IAP). When contracting the abdominal muscles, the diaphragm rises, while the pelvic floor muscles move downwards [26]. Also, in situations of strong abdominal muscles contractions, the diaphragm moves upwards, and the increase in IAP induces a contraction of the pelvic floor muscles [27].
Therefore, considering that the pelvic floor muscles do not contract by themselves, but in cooperation with the muscles around the abdominal area [28], we believe that this reasoning could be applied during the execution of pursed lips breathing, thus promoting the same effects, which can help the pushing in caudal direction [29].
The duration of the second stage of labor has been discussed as an important aspect of parturition, as the ideal duration for this stage is sought. The factors that influence the duration of this stage have been studied for the development of recommendations such as the breathing patterns used during expulsive efforts. There is no consensus yet regarding these practices and the ideal duration of this stage. It is estimated, though, that the longer the duration, the greater the maternal-fetal repercussion [18,24,30].
When evaluating the duration of the second stage of labor there were no differences regarding the type of pushing. These findings are similar to those of an aforementioned meta-analysis [2], which included six studies comparing the duration of that stage of labor associated with spontaneous pushing or with the directed pushing with VM. A total of 667 nulliparous women were evaluated, initially showing no difference in expulsive stage duration (MD 10.26 minutes; CI95%: -1,12 to 21,64). However, after sensitivity analysis, due to inadequate randomization, based on four studies with 494 women, a decrease in the duration of the expulsive stage with directed pushing was observed (MD:17,62; CI95%: 5,28 to 29,95). Those findings were yet considered inconsistent as they presented high heterogeneity due to methodological and statistical limitations, thus with a high association to random effects for those affirmations.
In another retrospective cohort study [22] conducted in Australia with 19.212 women a longer duration of the second stage of labor was observed for those who used the directed pushing when compared to the spontaneous pushing, that duration being 14.4 minutes (95%CI 12.0-16.8) for the nulliparous and 8.0 minutes (95%CI 6.8-9.2) for the multiparous. A randomized clinical trial [18] with 108 women corroborated the findings of the previous meta-analysis [2] regarding the expulsive period duration. Therefore, the discussion about the effect of the type of pushing on the duration of the expulsive period persists.
The duration of maternal pushing is another aspect that can influence maternal-fetal well-being and perineal integrity [31-33]. The women from our study who performed spontaneous pushing with pursed lips breathing showed a 3.2-minute reduction of the expulsive effort. This finding was similar to those of a meta-analysis [2] that analyzed pushing duration based on two studies with a total of 169 women, observing a decrease of 9.76 minutes (MD -9.76 minutes; 95%CI -19.54 to 0.02). However, after sensitivity analysis based on a study with 69 women, there was a 15-minute reduction in pushing duration for the spontaneous pushing group (MD -15,22 minutes; 95%CI -21,64 to -8,80). This analysis was based on one study only with a small sample and therefore should be interpreted with caution [2].
Favoring the discussion about the importance of these outcomes, a cohort [34] that analyzed 57.267 deliveries concluded that a maternal pushing more than 30 minutes long during the second stage of labor, and an expulsive stage more than one hour long are the potential factors for maternal and neonatal morbidities, especially postpartum hemorrhage, as well as uterine atony and cervical and perineal lacerations. This study recommends caution regarding obstetric interventions and better analyzing expectant management during the second stage of labor.
There was no difference between the types of pushing and delivery route or the need for instrumentalization. These data are similar to those found in the literature [2]. When analyzing research on pain, anxiety, and maternal fatigue in the second period of labor there is no consistent evidence about a direct association with the type of pushing. It is understood, however, that those outcomes might influence labor progression, as the stress generated by these sensations result in a greater release of catecholamines, fatty acids, and lactate, which can reduce the effectiveness of uterine contractions, possibly leading to prolonged labor, and consequently to dystocia, instrumentalization, higher post-partum hemorrhage risk, fetal distress and negative labor experience for the woman [32,34,35].
In our study, women who carried out spontaneous pushing with pursed lips breathing showed lower anxiety levels when compared to those on the control group. This result was seen because the more encouraged to do directed pushing with VM, the less physiological was the labor, thus increasing maternal distress following the release of hormones such as catecholamines and adrenaline, responsible for increasing maternal anxiety [16].
The type of maternal pushing did not influence neonatal outcomes in this study. This was expected since the apnea duration was lower than what is found in literature, which estimates that 7 to 8 seconds of apnea with high intrathoracic and abdominal pressures can already interfere in uteroplacental oxygen delivery, which can lead to fetal distress [36-43].
Not collecting data about the posture adopted by the parturient can be cited as a limitation of this study. That data can influence both the duration of the second stage of labor and the pushing. External conditions related to the hospital environment, such as noise or collective hospitalization, may have distracted the parturient’s focus on spontaneous pushing and breathing patterns orientations. Nevertheless, it is important to emphasize that there was no follow-up by the doulas of the service in any of the groups.
It is noteworthy that the exercises were performed by physical therapists. As we know, the individual must be well instructed by the professional to properly perform the technique. The technique is limited to 3 to 5 breaths, as prolonging it causes fatigue of the respiratory muscles and significantly lower levels of carbon dioxide, potentially leading to a decrease in perfusion to the brain, causing syncope. Without the proper use of pursed lips breathing an individual could exacerbate air and carbon dioxide retention [44].
In conclusion, spontaneous pushing with pursed lips breathing was not effective in reducing episiotomy. However, pushing duration decreased by 3.2 minutes, also showing a difference in maternal anxiety. This result may indicate its use for emotional control when compared to directed pushing. As an implication for physical therapy practice, these findings may signal an attitude in decision-making about guiding the breathing pattern in the expulsive stage.
Disclosure of interests
The study has no financial and religious interest, however, there is personal interest to know if the use of the spontaneous pushing with pursed lips breathing improves maternal and neonatal outcomes, as well as, in the political scope of building public and scientific interest, in improving conduct during labor.