Objective: To investigate the possibility of heart rate as an optimum index for evaluating physical labor intensity. Methods: From September to October, 2015, a total of 111 male young adults were selected as study subjects. A cycle ergometer was used for exercise at different intensities (20, 40, 60, 80, 100, 120, 140, 160, and 180 W) , and the exercise at each intensity lasted for 6 minutes. The subjects wore the K4b2 portable cardiopulmonary function testing instrument for the real-time monitoring of heart rate (HR) , pulmonary ventilation volume (Ve) , oxygen consumption (VO₂) , and energy metabolic rate (E) . The origin software was used for correlation and regression analyses of HR, Ve, VO₂, and E collected at different intensities to establish Ve-HR, VO₂-HR, and E-HR regression equations. Results: At different intensities, HR was positively correlated with Ve, VO₂, and E (r=0.8985, 0.8733, and 0.8973, all P<0.01) . There was a significant difference in the R² value of Ve-HR, VO₂-HR, and E-HR regression equations (R²=0.8070, 0.7625, and 0.8049, all P <0.01) . The validation results showed that there was no significant difference between the calculated values and the measured ones (P>0.05) . Conclusion HR can replace Ve, VO₂, and E and be used as an optimum index for evaluating physical labor intensity.

Objective:To investigate the factors influencing the decision to delivery interval (DDI) in emergency cesarean section in Guangzhou and the impact of DDI on maternal-infant outcomes.Methods:A retrospective study was conducted on clinical data of pregnant women who underwent emergency cesarean section at municipal and district maternal and child health hospitals in Guangzhou city in 2021. Per the classification method of emergency cesarean section and recommendations for DDI provided by National Institute for Health and Clinical Excellence guidelines, these subjects were classified into Category Ⅰ and Category Ⅱ cesarean sections. Each category was further divided into two subgroups based on DDI: the Category Ⅰ group into >30 min and ≤30 min subgroups, and the Category Ⅱ group into >75 min and ≤75 min subgroups. Chi-square test or Fisher's exact test, two independent samples t-test, Mann-Whitney U test, and logistic regression were used to analyze the potential factors influencing DDI and the impact of DDI on maternal-infant outcomes. Results:(1) Totally 502 women underwent urgent cesarean section, including 304 (60.6%) Category Ⅰ and 198 (39.4%) Category Ⅱ, were analyzed. Among the Category Ⅰ group, 30.3% (92/304) achieved a DDI of ≤30 min, while 37.4% (74/198) of Category Ⅱ cases had a DDI of ≤75 min. (2) For the Category Ⅰ cases, multivariate logistic regression showed that more patients under intravertebral anesthesia, than those under general anesthesia, had a DDI >30 min ( OR=14.04, 95% CI: 6.14-32.10) as well as more with ward-based emergencies than those with delivery room emergencies ( OR=3.21, 95% CI: 1.72-6.00, both P=0.001). Among the Category Ⅱ cases, logistic regression revealed that cesarean section during routine working hours was more likely to achieve DDI >75 min than that during resting hours ( OR=3.93, 95% CI: 2.03-7.63, P=0.001). The risk of DDI >75 min was higher in tertiary maternal and child health hospitals compared with secondary maternal and child health hospitals ( OR=2.45, 95% CI: 1.06-5.70, P=0.037). (3) Among the Category Ⅰ cases, compared with the DDI ≤30 min group, the DDI >30 min group had a lower risk of neonatal Apgar score ≤7 at 1 min ( OR=0.31, 95% CI: 0.14-0.69, P=0.004), but there was no significant difference in the risk of neonatal Apgar score ≤7 at 5 min ( OR=0.21, 95% CI: 0.04-1.17) or neonatal asphyxia ( OR=0.32, 95% CI: 0.07-1.44) between the two subgroups. In cases of Category Ⅱ cesarean sections, there was no significant difference in any maternal-infant outcomes between DDI ≤75 min and DDI >75 min subgroups. Conclusions:The location of emergency and types of anesthesia are the influencing factors of DDI for Category Ⅰ cesarean sections, while the operation time and level of maternal and child health hospital are the influencing factors of DDI for Category Ⅱ cesarean sections. We did not find any impact of DDI on maternal or infant outcome.