***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Pathological formation of reactive oxygen species within the coronary circulation has been hypothesized to mediate some clinical manifestations of ischemic heart disease ( IHD ) by interfering with physiological regulation of coronary tone . To determine the degree to which coronary tone responds to acute changes in ambient levels of oxidants and antioxidants in vivo in a clinical setting , we measured the effect of an acute oxidative stress ( breathing 100 % oxygen ) on coronary capacitance artery diameter ( quantitative angiography ) and blood flow velocity through the coronary microcirculation ( intracoronary Doppler ultrasonography ) before and after treatment with the antioxidant vitamin C ( 3-g intravenous infusion ) in 12 IHD patients undergoing a clinical coronary interventional procedure . Relative to room air breathing , 100 % oxygen breathing promptly reduced coronary blood flow velocity by 20 % and increased coronary resistance by 23 % , without significantly changing the diameter of capacitance arteries .  Vitamin C administration promptly restored coronary flow velocity and resistance to a slightly suprabasal level , and it prevented the reinduction of coronary constriction with rechallenge with 100 % oxygen . This suggests that acute oxidative stress produces prompt and substantial changes in coronary resistance and blood flow in a clinical setting in patients with IHD , and it suggests that these changes are mediated by vitamin C-quenchable substances acting on the coronary microcirculation . This observation may have relevance for clinical practice BACKGROUND Administration of supplemental oxygen in the perioperative period is controversial , as it may increase long-term mortality . Our aim was to assess the association between 80 % oxygen and occurrence of subsequent cancer in patients undergoing abdominal surgery in a post hoc analysis of the PROXI trial . METHODS The 1386 patients in the PROXI trial underwent elective or emergency laparotomy between 2006 and 2008 with r and omization to either 80 % or 30 % oxygen during and for 2 h after surgery . We retrieved follow-up status regarding vital status , new cancer diagnoses , and new histological cancer specimens . Data were analysed using the Cox proportional hazards model . RESULTS Follow-up was complete in 1377 patients ( 99 % ) after a median of 3.9 yr . The primary outcome of new cancer diagnosis or new malignant histological specimen occurred in 140 of 678 patients ( 21 % ) in the 80 % oxygen group vs 150 of 699 patients ( 21 % ) assigned to 30 % oxygen ; hazards ratio 1.06 [ 95 % confidence interval ( CI ) 0.84 , 1.34 ] , P=0.62 . Cancer-free survival was significantly shorter in the 80 % oxygen group ; hazards ratio 1.19 ( 95 % CI 1.01 , 1.42 ) , P=0.04 , as was the time between surgery and new cancer , median 335 vs. 434 days in the 30 % oxygen group . In patients with localized disease , non-significant differences in cancer and cancer-free survival were found with hazard ratios of 1.31 and 1.29 , respectively . CONCLUSIONS Although new cancers occurred at similar rate , the cancer-free survival was significantly shorter in the 80 % oxygen group , but this did not appear to explain the excess mortality in the 80 % oxygen group . CLINICAL TRIAL REGISTRATION Clinical Trials.gov ( NCT01723280 ) BACKGROUND Perioperative supplemental oxygen has been proposed to decrease the incidence of surgical site infection ( SSI ) in colorectal surgery with controversial results . We have assessed the influence of hyperoxygenation on SSI by using the most homogeneous study population . METHODS We studied , in a prospect i ve r and omized study , 81 patients , who underwent elective open infraperitoneal anastomosis for rectal cancer . Patients were assigned r and omly to an oxygen/air mixture with a fraction of inspired oxygen ( FiO2 ) of 30 % ( n = 41 ) or 80 % ( n = 40 ) . Administration was commenced after induction of anesthesia and maintained for 6 hours after surgery . RESULTS The overall wound infection rate was 21 % : 11 patients ( 26.8 % ) had wound infections in the 30 % FiO2 group and 6 ( 15 % ) in the 80 % FiO2 group ( P < .05 ) . The risk of SSI was 41 % lower in the 80 % FiO2 group . CONCLUSION Supplemental 80 % FiO2 reduced postoperative SSI with few risks to the patient and little associated cost OBJECTIVE The purpose of this study was to investigate whether supplemental oxygen during and for 2 hours after cesarean delivery reduces the incidence of postcesarean infectious morbidity . STUDY DESIGN We conducted a r and omized , controlled trial from 2008 - 2010 . Women who underwent cesarean delivery were r and omly assigned to receive either 2 L of oxygen by nasal cannula during cesarean delivery only ( st and ard care ) or 10 L of oxygen by nonrebreather mask ( intervention group ) during and for 2 hours after cesarean delivery .  Women who underwent scheduled or intrapartum cesarean delivery were eligible and were observed for 1 month after the procedure . The primary composite outcome was maternal infectious morbidity , which included endometritis and wound infection . RESULTS Five hundred eighty-five women were included in the final analysis .  Infectious morbidity occurred in 8.8 % of patients in the st and ard care group and in 12.2 % of patients in the supplemental oxygen group . There was no significant difference in the rate of infectious morbidity between the st and ard care and intervention groups ( relative risk , 1.4 ; 95 % confidence interval , 0.9 - 2.3 ) . CONCLUSION Supplemental oxygen does not reduce the rate of postcesarean delivery infectious morbidity , including endometritis and wound infection BACKGROUND : A high perioperative inspiratory oxygen fraction ( 80 % ) has been recommended to prevent postoperative wound infections . However , the most recent and one of the largest trials , the PROXI trial , found no reduction in surgical site infection , and 30-day mortality was higher in patients given 80 % oxygen . In this follow-up study of the PROXI trial we assessed the association between long-term mortality and perioperative oxygen fraction in patients undergoing abdominal surgery . METHODS : From October 8 , 2006 , to October 6 , 2008 , 1386 patients underwent elective or emergency laparotomy and were r and omized  to receive either 80 % or 30 % oxygen during and for 2 hours after surgery . The follow-up date was February 24 , 2010 . Survival was analyzed using Kaplan-Meier statistics and the Cox proportional hazards model . RESULTS : Vital status was obtained in 1382 of 1386 patients after a median follow-up of 2.3 years ( range 1.3 to 3.4 years ) . One hundred fifty-nine of 685 patients ( 23.2 % ) died in the 80 % oxygen group compared to 128 of 701 patients ( 18.3 % ) assigned to 30 % oxygen ( HR , 1.30 [ 95 % confidence interval , 1.03 to 1.64 ] , P = 0.03 ) . In patients undergoing cancer surgery , the HR was 1.45 ; 95 % confidence interval , 1.10 to 1.90 ; P = 0.009 ; and after noncancer surgery , the HR was 1.06 ; 95 % confidence interval , 0.69 to 1.65 ; P = 0.79 . CONCLUSIONS : Administration of 80 % oxygen in the perioperative period was associated with significantly increased long-term mortality and this appeared to be statistically significant in patients undergoing cancer surgery but not in noncancer patients This explicit and strong recommendation has caused considerable concern in the anaesthesia community because it directly contradicts the results of many trials ( and a meta- analysis of those trials ) which showednobenefitof supplemental oxygen . The use of an increased inspired oxygen fraction ( FiO2 ) has a long history in anaesthesia , intensive care , and emergency medicine . Planned induction and extubation of anaesthesia are conducted with 100 % oxygen to enhance safety in the case of airwaydifficulty . Extra oxygen is alsogivenduringgeneral anaesthesia as 21 % is rarely sufficient , with concentrations ranging from 30 % to nearly 100 % depending on case factors and anaesthesiologist preference . There is considerable reason to expect that supplemental oxygen might reduce the risk of surgical site infection [ 21 ] . All surgical wounds become contaminated , and the primary defence against bacterial contamination isoxidativekillingbyneutrophils , a process that requires molecular oxygen and depends on the partial pressureofoxygenintissueovertheentire physiological range . Consistent with this theory , Hopf et al. [ 11 ] showed that surgical wound infection risk was inversely related to tissue oxygenation . Based on these observational data , the Outcomes Research Consortium r and omized 500 patients having colorectal resection to either 80%or30 % inspiredoxygen [ 9 ] . The incidence of SSI was halved from 11.2 AIM An association has been proposed between perioperative administration of 80 % oxygen and a lower incidence of wound infection after colorectal surgery . The present study was conducted to assess this hypothesis . METHODS Thirty-eight patients ( ASA classification 1 and 2 ) undergoing elective colorectal cancer surgery were allocated at r and om to 2 groups . Group 1 consisted of 19 patients who received an admixture of 80 % oxygen and 20 % nitrogen during anesthesia through an orotracheal tube and during the 2 first hours in the recovery room through a tight facemask with reservoir . Group 2 consisted of 19 patients who received an admixture of 70 % nitrous oxide and 30 % oxygen during anesthesia , followed by administration of 30 % oxygen delivered by a blender through a tight facemask with reservoir in the same manner than group 1 , during the first 2 hours in the recovery room . Wound infection was evaluated daily during hospital stay and after 7 days , 2 weeks , and 1 month . RESULTS The incidence of wound infection was 12.5 % in group 1 and 17.6 % in group 2 ( p=0.53 ) . CONCLUSIONS The results of this study showed no reduction in the incidence of wound infection following elective colorectal surgery in patients receiving 80 % oxygen during the perioperative period Background : Benefits and limitations of supplementation with 80 % fraction of inspired oxygen for preventing surgical site infections have not yet been clearly defined . Some studies have reported benefits in colorectal surgery , whereas trials in abdominal and gynecologic surgery have reported either no effect or a deleterious effect . Methods : Controlled , r and omized , assessor-blind multicenter trial , the ISO2 study , comparing the effects of hyperoxygenation ( fraction of inspired oxygen , 80 % ) with those of 30 % oxygen on the frequency of surgical site infections in routine abdominal , gynecologic , and breast surgery on 434 patients . Patients not seen in consultation after discharge were contacted . Results : In total , 208 patients received 30 % perioperative oxygen and 226 received 80 % .  There was no difference between the two groups for baseline , intraoperative , and postoperative characteristics , except for oxygen saturation at closure , higher in the 80 % group ( P = 0.01 ) . The frequency of 30-day surgical site infections was 7.2 % ( 15/208 ) in the 30 % group and 6.6 % ( 15/226 ) in the 80 % group ( relative risk , 0.92 ; 95 % CI [ 0.46–1.84 ] , P = 0.81 ) . Frequency of adverse events ( nausea and vomiting , sternal pain , cough , hypotension ) was similar in the two groups . Desaturation and bradycardia were more frequent in the 30 % group . In an up date d meta- analysis including the result of this trial and those of eight published r and omized trials , the overall relative risk was 0.97 ; 95 % CI ( 0.68–1.40 ) , I2 ( inconsistency degree ) = 73 % , ( P = 0.88 ) . Conclusions : The routine use of hyperoxygenation throughout abdominal , gynecologic , and breast surgery had no effect on the frequency of 30-day surgical site infections and was not accompanied by more frequent adverse effects Background A high perioperative inspiratory oxygen fraction ( FiO2 ) may reduce the frequency of surgical site infection . Perioperative atelectasis is caused by absorption , compression and reduced function of surfactant . It is well accepted , that ventilation with 100 % oxygen for only a few minutes is associated with significant formation of atelectasis . However , it is still not clear if a longer period of 80 % oxygen results in more atelectasis compared to a low FiO2.Our aim was to assess 
    Output:
    
Conclusions No definite signal of harm with 80 % FiO2 in adult surgical patients undergoing general anaesthesia was demonstrated and there is little evidence on safety‐related issues to discourage its use in this population