FiO2 Group Research Articles

Higher fraction of inspired oxygen during anesthesia increase the risk of postoperative pulmonary complications in patients undergoing non-cardiothoracic surgery: a retrospective cohort study.

The ideal intra-operative inspired oxygen concentration remains controversial. We aimed to investigate the association between the intraoperative fraction of inspired oxygen (FiO2) and the incidence of postoperative pulmonary complications (PPCs) in patients undergoing non-cardiothoracic surgery. This was a retrospective cohort study of elderly patients who underwent non-cardiothoracic surgery between April 2020 and January 2022. According to intraoperative FiO2, patients were divided into low (≤60%) and high (>60%) FiO2 groups. The primary outcome was the incidence of a composite of pulmonary complications (PPCs) within the first seven postoperative days. Propensity score matching (PSM) and inverse probability treatment weighting (IPTW) were conducted to adjust for baseline characteristic differences between the two groups. Multivariate logistic regression analysis was used to calculate the odds ratios (OR) for FiO2 and PPCs. Among the 3,515 included patients with a median age of 70years (interquartile range: 68-74), 492 (14%) experienced PPCs within the first 7 postoperative days. Elevated FiO2 was associated with an increased risk of PPCs in all the logistic regression models. The OR of the FiO2 > 60% group was 1.252 (95%CI, 1.015-1.551, P = 0.038) in the univariate analysis. In the multivariate logistic regression models, the ORs of the FiO2 > 60% group were 1.259 (Model 2), 1.314 (Model 3), and 1.32 (model 4). A balanced covariate distribution between the two groups was created using PSM or IPTW. The correlation between elevated FiO2 and an increased risk of PPCs remained statistically significant with PSM analysis (OR, 1.393; 95% CI, 1.077-1.804; P = 0.012) and IPTW analysis (OR, 1.266; 95% CI, 1.086-1.476; P = 0.003). High intraoperative FiO2 (>60%) was associated with the postoperative occurrence of pulmonary complications, independent of predefined risk factors, in elderly non-cardiothoracic surgery patients. High intraoperative FiO2 should be applied cautiously in surgical patients vulnerable to PPCs.

Effects of 30% vs. 60% inspired oxygen fraction during mechanical ventilation on postoperative atelectasis: a randomised controlled trial

BackgroundThere is the ongoing debate over the effect of inspired oxygen fraction (FiO2) during mechanical ventilation on postoperative atelectasis. We aimed to compare the effects of low (30%) and moderate (60%) FiO2 on postoperative atelectasis. The hypothesis of the study was that 30% FiO2 during mechanical ventilation could reduce postoperative atelectasis volume compared with 60% FiO2.MethodsWe performed a randomized controlled trial with 120 patients. Subjects were randomly assigned to receive 30% or 60% FiO2 during mechanical ventilation in a 1:1 ratio. The primary outcome was the percentage of postoperative atelectasis volume in the total lung measured using chest CT within 30 min after extubation. The secondary outcomes included different aeration region volumes, incidence of clinically significant atelectasis, and oxygenation index.ResultsIn total, 113 subjects completed the trial, including 55 and 58 subjects in the 30% and 60% FiO2 groups, respectively. The percentage of the postoperative atelectasis volume in the 30% FiO2 group did not differ from that in the 60% FiO2 group. Furthermore, there was no significant difference in the atelectasis volume between the two groups after the missing data were imputed by multiple imputation. Additionally, there were no significant differences in the volumes of the over-aeration, normal-aeration, and poor-aeration regions between the groups. No significant differences in the incidence of clinically significant atelectasis or oxygenation index at the end of surgery were observed between the groups.ConclusionsCompared with 60% FiO2, the use of 30% FiO2 during mechanical ventilation does not reduce the postoperative atelectasis volume.Trial registrationChinese Clinical Trial Registry (http://www.chictr.org.cn). Identifier: ChiCTR1900021635. Date: 2 March 2019. Principal invetigator: Weidong Gu.

Updated meta-analysis on intraoperative inspired fraction of oxygen and the risk of surgical site infection in adults undergoing general and regional anesthesia

This updated meta-analysis aims at exploring whether the use of systematic high vs low intraoperative oxygen fraction (FiO2) may decrease the incidence of postoperative surgical site infection during general (GA) or regional anesthesia (RA). PubMed, Cochrane CENTRAL, ClinicalTrials.gov databases were searched from January 1st, 1999 and July, 1st 2022, for randomized and quasi-randomized controlled trials that included patients in a high and low FiO2 groups and reported the incidence of SSI. The meta-analysis was conducted with a DerSimonian and Laird random-effects model. Thirty studies (24 for GA and 6 for RA) totaling 18,055 patients (15,871 for GA and 2184 for RA) were included. We have low-to-moderate-quality evidence that high FiO2 (mainly 80%) was not associated with a reduction of SSI incidence compared to low FiO2 (mainly 30%) in all patients (RR 0.90, 95%CI 0.79–1.03). Moderate inconsistency existed between studies (I2 = 38%). Subgroup analyses showed a moderate protective effect in patients undergoing GA (RR 0.86, 95%CI 0.75–0.99) (low level of evidence), while high FiO2 was not associated with a reduction of SSI in patients undergoing RA (RR 1.17, 95%CI 0.90–1.52) (moderate level of evidence). Sensitivity analyses restricted to patients ventilated without nitrous oxide (n = 20 studies), to patients operated from abdominal surgeries (n = 21 studies), and to patients suffering from deep SSI (n = 13 studies), all showed the absence of any significant effect of high FiO2. As a conclusion there is no compelling evidence that high FiO2 can improve postoperative patient’s outcome on its own when good SSI prevention practices are properly applied. Recent well-designed and adequately powered randomized controlled trials add further weight to these results.

Adjust Intraoperative Oxygen Therapy for Oxygenation Reasons Only!

Adjust Intraoperative Oxygen Therapy for Oxygenation Reasons Only!

An Automation System Equivalent to the Douglas Bag Technique Enables Continuous and Repeat Metabolic Measurements in Patients Undergoing Mechanical Ventilation

PurposeTo develop a system that is equivalent to the gold standard Douglas Bag (DB) technique for measuring oxygen consumption (V̇o2), carbon dioxide generation (V̇co2), and respiratory quotient (RQ) and to validate its use in clinical settings. MethodsThis was a prospective, observational study conducted at a suburban, quaternary care teaching hospital. Healthy volunteers and patients 18 years or older who received mechanical ventilation were enrolled. FindingsData from 3 healthy volunteers and 7 patients were analyzed in this study. The interrater reliability between the automation device and DB methods were 0.999, 0.993, and 0.993 for V̇o2, V̇co2, and RQ, respectively. In healthy volunteers, mean (SD) V̇o2, V̇co2, and RQ measured by DB were 411 (100) mL/min, 288 (79) mL/min, and 0.70 (0.03) at high fraction of inspired oxygen (Fio2) and 323 (46) mL/min, 280 (45) mL/min, and 0.85 (0.05) at normal Fio2, respectively. V̇o2 was significantly higher (P < 0.05) and RQ was lower (P < 0.01) in the high Fio2 group as compared to those in the normal Fio2 group. Values measured by the automation system were 227 (31) mL/min, 141 (18) mL/min, and 0.62 (0.04) at high Fio2 and 209 (25) mL/min, 147 (18) mL/min, and 0.70 (0.06) at normal Fio2, respectively. RQ was significantly lower (P < 0.05) in the high Fio2 group as compared to the normal Fio2 group. We also successfully performed continuous and repeat measurements by using the device. The longest measurement reached 12 hours 15 minutes, including 50 cycles of repeat measurements that are equivalent to the DB technique as described above. ImplicationsWe developed an automation system that enables repeat measurements of V̇o2, V̇co2, and RQ, and the accuracy was equivalent to the DB technique. High Fio2 may decrease RQ because of an increase in V̇o2.

Resuscitation of very preterm infants with 30% vs. 50% oxygen: a randomized controlled trial

Background Preterm infants are susceptible to the damaging effects of hyperoxia which may lead to bronchopulmonary dysplasia (BPD) and intestinal damage. Hyperoxia also affects intestinal microbiota. The optimal initial FiO2 for the resuscitation of premature infants is unknown.&#x0D; Objective To determine the effect of different initial oxygen concentrations on BPD, oxidative stress markers, damage to the gastrointestinal mucosa, and the intestinal microbiome.&#x0D; Methods We conducted an unblinded, randomized controlled clinical trial in premature infants requiring supplemental oxygen in the first minutes of life. Infants started at an FiO2 of either 30% (low) or 50% (moderate), which was adjusted to achieve target oxygen saturations (SpO2) of 88-92% by 10 minutes of life using pulse oximetry. The primary outcome was incidence of BPD. Secondary outcomes included markers of oxidative stress [oxidized glutathione (GSH)/reduced glutathione (GSSG) ratio and malondialdehyde (MDA)], intestinal integrity indicated by fecal alpha-1 antitrypsin (AAT), and intestinal microbiota on fecal examination.&#x0D; Results Eighty-four infants were recruited. There was no significant difference in rates of BPD between the 30% FiO2 and 50% FiO2 groups (42.8% vs. 40.5%, respectively). Nor were there significant differences in GSH/GSSG ratios, MDA concentrations, fecal AAT levels, or changes in facultative anaerobic and anaerobic microbiota between groups.&#x0D; Conclusion In premature infants resuscitated using low vs. moderate initial FiO2 levels, we find no significant differences in BPD incidence, markers of oxidative stress, intestinal mucosa integrity, or intestinal microbiota.

The Effect of Inhaled Albuterol on PaO2 in Anesthetized Horses Receiving a FiO2 of 0.5 or >0.95

Impairment of oxygen uptake can occur during general anesthesia in horses resulting in hypoxemia. Multiple treatments have been investigated for correction of hypoxemia with varying levels of success. In clinical trials, albuterol, a short-acting β2 adrenergic agonist, improved arterial oxygen partial pressure (PaO2) in anesthetized horses unresponsive to adjustments in mechanical ventilation and administration of positive inotropic drugs. However, controlled studies comparing the magnitude of change and duration of effect of albuterol on PaO2 in healthy, nonhypoxemic anesthetized horses are lacking. In a prospective study, 14 horses were anesthetized and received a FiO2 of 0.5 (n = 7) or > 0.95 (n = 7). Horses were maintained on isoflurane and mechanically ventilated. After 15 minutes, baseline PaO2 was determined. Within each FiO2 group, five horses were administered inhaled albuterol (2 µg/kg) and two horses received no treatment. At 10, 20, 30, and 40 minutes after baseline, PaO2 was measured. Data for horses that received albuterol were analyzed with repeated measures analysis of variance with significance at P < .05. Horses that received albuterol had an increase in PaO2 for at least 40 minutes after baseline. Albuterol administered via inhalation, was associated with an increased PaO2 of at least 40 minutes compared to baseline in healthy, nonhypoxemic horses undergoing anesthesia at similar depth, using a FiO2 of 0.5 and > 0.95. Side effects were mild and consisted of increased heart rate and sweating. Albuterol administered at 2 μg/kg via inhalation may be useful for increasing PaO2 in anesthetized horses.

Association of Passive Lung Insufflation Oxygen Fraction in Adult Patients on Cardiopulmonary Bypass with Postoperative Pulmonary Outcomes: A Retrospective Cohort Study

To determine whether FIO2 of passive lung insufflation during cardiopulmonary bypass correlates with postoperative pulmonary function. A retrospective, observational study SETTING: A single-center, university-affiliated, specialist cardiothoracic center in the United Kingdom. Adult patients presenting for nonemergency, nontransplant cardiac surgery requiring cardiopulmonary bypass without the need for deep hypothermic circulatory arrest between January 1, 2018, and December 31, 2018. Passive insufflation of the lungs during cardiopulmonary bypass with fresh gas flow of varying FIO2. Patients were sorted retrospectively into low FIO2 (0.21-0.44), intermediate FIO2 (0.45-0.69), and high FIO2 (0.7-1.0) groups. The primary outcome was the difference between the PaO2:FIO2 on the first postinduction blood gas and on the first blood gas recorded postoperatively in the intensive care unit (ICU) (delta PaO2:FIO2). Secondary outcomes were ICU and hospital lengths of stay, requirement for respiratory support, and 30-day mortality. Nine hundred patients were included in the authors' analysis (low FIO2 n=307, intermediate FIO2 n=459, high FIO2 n=134). There was no significant difference in delta PaO2:FIO2 among the groups (low FIO2=52.5 [-38.8 to 152.4], intermediate FIO2=71.8 [-39.4 to 165.1], high FIO2=60.2 [-19.2 to 184.0], p=0.25). There were no significant differences among groups for any secondary outcomes. Fresh gas flow with a low FIO2 delivered to the lungs without positive airway pressure during cardiopulmonary bypass was not associated with improved postoperative pulmonary function when compared to higher FIO2 levels.

Effect of Conventional High Flow Oxygen Therapy Compared to Conservative Oxygen Therapy in Mechanically Ventilated Neonates

Background: Mechanically ventilated neonates are usually exposed to high oxygen therapy and due to common clinical practice and lack of knowledge about the target and optimum dose &amp; duration of oxygen administration hyperoxia occurs frequently. The study was done to compare the effect between conventional high flow and conservative oxygen therapy. Materials &amp; Methods: A prospective study was done in Dhaka Shishu Hospital NICU from July 2013 to June 2014 and enrolled those were underwent invasive mechanical ventilation. Ventilator settings, FiO2 and SpO2 were recorded for the first 48 hours. The comparison of conventional high FiO2 (&gt; 0.7-1.0) and conservative FiO2(&lt; 0.7) therapy was assessed by SpO2, PaO2, PaO2/ FiO2 ratio and lung injury score within 48 hours of exposure and was analyzed. Results: Among total 40 cases 30/40(75%) were exposed to conventional high FiO2. After invasive mechanical ventilation, there was improvement of SpO2 in both group (76.7% vs 70%) but there was no significant difference in between conventional high FiO2 implementation and conservative group(P=0.67). PaO2/ FiO2 ratio also improved after ventilation (145.17 vs 328.40, P=0.013) in both groups but indicate lung injury in conventional high FiO2 group. After invasive mechanical ventilation 53% (16/30) patients were suffering from acute lung injury(ALI) &amp; acute respiratory distress syndrome (ARDS) with high exposure of FiO2 (&gt;0.7-1) and only 40% (4/10) patient developed ALI &amp; ARDS in low exposure group (FiO2&lt;0.7). Conclusions: Conventional high FiO2 or liberal O2 therapy in mechanically ventilated neonates improves SpO2 but conventional high FiO2 may causes iatrogenic lung injury. BANGLADESH J CHILD HEALTH 2021; VOL 45 (1) : 19-24

Effect of Peri-Operative Hyperoxygenation on Surgical Site Infection in Patients Undergoing Emergency Abdominal Surgery: A Randomized Controlled Trial

Background: The rationale for hyperoxygenation in controlling surgical site infection (SSI) has been described in many studies yet has not been defined clearly. Some studies in colorectal surgery have reported beneficial effects, whereas studies in gynecologic surgery have reported either no effect or a deleterious effect. This study assessed the effectiveness of hyperoxygenation on the reduction of SSI in patients undergoing emergency abdominal surgery. Patients and Methods: Eligible patients were assigned randomly to two groups (study group, 80% oxygen or control group, 30% oxygen). The patients in the study group received 80% oxygen and the patients in the control group received 30% oxygen intra-operatively and for two hours after surgery. Arterial blood gas analysis was done after resuscitation, at the end of the surgery, and at two hours after extubation. All patients were assessed for SSI, post-operative nausea and vomiting, and respiratory complications. Patients were followed post-operatively for 14 days. Surgical site infection was diagnosed according to U.S. Centers for Disease Control and Infection (CDC) criteria and by aerobic wound cultures. Results: After exclusion, 85 patients in the control group and 93 patients in the study group were analyzed. There was no difference for baseline, intra-operative, and post-operative characteristics between the two groups, except for higher oxygen saturation at closure and two hours post-operatively, in the 80% group (p = 0.01). Surgical site infection occurred in 29 patients (34.11%) in 30% fraction of inspired oxygen (FIO2) group and in 19 patients (20.43%) in 80% FIO2 group (p = 0.04). The risk of SSI was 59% lower in the 80% FIO2 group (adjusted odds ratio, 0.41; 95% confidence interval [CI], 0.19-0.88 vs. the 30% FIO2 group). There were no differences in post-operative nausea and vomiting and respiratory complications between the two treatment groups. Conclusions: Administration of 80% peri-operative hyperoxygenation in emergency abdominal surgery reduces SSI and is a cost-effective method.

Effect of intra-operative high inspired fraction of oxygen on postoperative nausea and vomiting in children undergoing surgery: A prospective randomised double-blind study.

Administration of high inspired fraction of oxygen (FiO2) during anaesthesia has been proposed to decrease postoperative nausea and vomiting (PONV) in adults but has not been extensively studied in children. The primary objective of this study was to evaluate the effect of 80% FiO2 on the incidence of PONV in children undergoing surgery. Prospective, randomised, study. Single-centre, teaching hospital. Children of either gender in the age group of 5 to 15 years scheduled for elective surgeries were assessed for eligibility. Emergency surgeries; patients receiving supplemental oxygen pre-operatively or on mechanical ventilation; sepsis; bowel obstruction or ischaemia; poor nutritional status; anaemia (Hb <8 g%) or surgeries lasting less than 1 h or greater than 4 h were excluded from the study. After induction of anaesthesia, children were randomised to receive either 30 or 80% oxygen in air, till the end of surgery. Incidence of PONV within 24 h; surgical site infections (SSI)s; serum serotonin and TNF-α levels and the incidence of postoperative pulmonary complications (PPC)s were studied. The overall 24 h incidence of PONV was not different between the low and high FiO2 groups [24 vs. 23%; P = 0.84; odds ratio (OR) 0.92; 95% confidence interval (CI), 0.44 to 2.06]. The incidence of SSIs (15 vs. 12%; P = 0.61; OR 0.77; 95% CI, 0.28 to 2.10) and PPCs (12 vs. 8%; P = 0.38; OR 0.59; 95% CI, 0.18 to 1.92) were not significant between the low and high FiO2 groups, respectively. Intragroup and intergroup comparisons of serum serotonin and TNF-α showed no significant difference either at baseline or at the end of surgery. High intra-operative FiO2 of 80% does not provide additional protection against PONV in children. The study was registered with Clinical Trials Registry of India (CTRI) with trial registration no: CTRI/2018/07/014974.

The Value of Interleukin-6 among Several Inflammatory Markers as a Predictor of Respiratory Failure in COVID-19 Patients.

Patients with coronavirus disease 2019 (COVID-19) develop severe respiratory failure within a short period during the clinical course. It is essential to predict respiratory deterioration in the short term. We investigated the use of inflammatory markers to predict respiratory distress within three days from their analysis in COVID-19 patients. This retrospective observational study included 81 patients admitted with COVID-19. Patients were divided into two groups according to whether the maximum fraction of inspired oxygen (FiO2) for three days from the blood marker measurements was ≥0.4 (high FiO2 group; HFG) or <0.4 (low FiO2 group; LFG). Interleukin-6 (IL-6), C-reactive protein (CRP), lactate dehydrogenase (LDH), white blood cell, D-dimer, and creatinine levels were compared between the two groups. The levels of all markers were significantly higher in HFG patients. Areas under the receiver operating characteristic curve of IL-6, CRP, and LDH had high values of 0.85, 0.82, and 0.81, respectively. The odds ratio of IL-6 which was crude and adjusted for dexamethasone administration initiated before laboratory measurement, showed the high value of 29.1 (5.6–295.6) and 53.9 (4.5–3242.8), respectively. IL-6 can be used as a reliable marker for predicting respiratory illness within three days after assessment.

Intraoperative Oxygen Concentration and Postoperative Delirium After Laparoscopic Gastric and Colorectal Malignancies Surgery: A Randomized, Double-Blind, Controlled Trial.

PurposePostoperative delirium (POD) is common in elderly patients undergoing laparoscopic surgery for gastric and colorectal malignancies. POD may be affected by different fraction of inspired oxygen (FiO2). The purpose of this study was to compare the effects of different FiO2 on POD.Patients and MethodsA randomized, double-blind controlled trial was performed in Qingdao Municipal Hospital Affiliated to Qingdao University. A total of 662 patients aged 65 to 85 years old underwent isolated laparoscopic radical gastrectomy, radical resection of colon cancer, or radical resection of rectal cancer only. A random number table method was used to divide the patients into two groups: 40% FiO2 (group A) and 80% FiO2 (group B). The primary endpoint was the incidence of POD, which was assessed by the Confusion Assessment Method (CAM) twice daily during the first 7 postoperative days, and POD severity was measured by the Memorial Delirium Assessment Scale (MDAS). The secondary endpoints were the intraoperative regional cerebral oxygen saturation (rSO2), Bispectral (BIS) index, invasive arterial blood pressure (IABP), oxygen saturation (SpO2), end-tidal carbon dioxide partial pressure (PETCO2), the number of atelectasis cases and visual analogue scale (VAS) scores on days 1–7 after surgery.ResultsThe incidence of POD was 19.37% (122/630), including 20.38% (64/314) in group A and 18.35% (58/316) in group B. No statistical significance was found in the incidence of POD between the two groups (P > 0.05); compared with group B, SpO2, rSO2 and PaO2 decreased at T2 to T4 time point (P < 0.01), and the incidence of postoperative atelectasis decreased (P < 0.05) in group A.ConclusionThe incidence of POD was not significantly affected by different FiO2 and the incidence of postoperative atelectasis was decreased at low FiO2.

Perioperative high inspired oxygen fraction induces atelectasis in patients undergoing abdominal surgery: A randomized controlled trial

Study objectiveWe evaluated the feasibility of use and effects on postoperative atelectasis and complications of lower inspired oxygen fraction (FIO2) compared to conventional oxygen therapy. DesignSingle center, randomized clinical trial. SettingUniversity hospital, operating room and postoperative recovery area. PatientsOne hundred ninety patients aged ≥50 with an American Society of Anesthesiologists physical status of I-III who underwent abdominal surgery with general anesthesia. InterventionsParticipants were randomly assigned to either the low FIO2 group (intraoperative: FIO2 0.35, during induction and recovery: FIO2 0.7) or the conventional FIO2 group (intraoperative: FIO2 0.6, during induction and recovery: FIO2 1.0). MeasurementsThe primary outcome was postoperative atelectasis measured with lung ultrasonography at postoperative 30 min in the post-anesthesia care unit (consolidation score: each region 0–3, 12 region, total score range of 0 to 36, a lower score indicating better aeration). Main resultsSeven patients in the low FIO2 group were omitted from the study due to changing FIO2 during intervention (7/95 (8.4%) vs. 2/95 (2.1%), p = 0.088; low FIO2 group vs. conventional FIO2 group). Overall, atelectasis was detected in 29.7% (51/172) of patients 30 min after surgery by lung ultrasound and 40.1% (69/172) of patients after 2 days after surgery by chest X-ray. The scores of lung ultrasonography and the incidence of significant atelectasis (consolidation score ≥ 2 at any region) were lower in the low FIO2 group than in the conventional FIO2 group (median [IQR]: 3 [1,6] vs. 7 [3,9], p < 0.001 and 17/85 (20%) vs. 34/87 (39%), RR: 0.512 [95% CI: 0.311–0.843], p = 0.006, respectively). The incidence of surgical site infection and length of hospitalization were not significantly different between the two groups. ConclusionsBased on our findings, decreased inspired oxygen fraction during anesthesia and recovery did not cause hypoxic events, but instead reduced immediate postoperative atelectasis. The use of intraoperative conventional higher inspired oxygen did not afford any clinical advantages for postoperative recovery in abdominal surgery.

The Effect of Initial Oxygen Exposure on Diaphragm Activity in Preterm Infants at Birth.

Background: The initial FiO2 that should be used for the stabilization of preterm infants in the delivery room (DR) is still a matter of debate as both hypoxia and hyperoxia should be prevented. A recent randomized controlled trial showed that preterm infants [gestational age (GA) < 30 weeks] stabilized with an initial high FiO2 (1.0) had a significantly higher breathing effort than infants stabilized with a low FiO2 (0.3). As the diaphragm is the main respiratory muscle in these infants, we aimed to describe the effects of the initial FiO2 on diaphragm activity.Methods: In a subgroup of infants from the original bi-center randomized controlled trial diaphragm activity was measured with transcutaneous electromyography of the diaphragm (dEMG), using three skin electrodes that were placed directly after birth. Diaphragm activity was compared in the first 5 min after birth. From the dEMG respiratory waveform several outcome measures were determined for comparison of the groups: average peak- and tonic inspiratory activity (dEMGpeak and dEMGton, respectively), inspiratory amplitude (dEMGamp), area under the curve (dEMGAUC) and the respiratory rate (RR).Results: Thirty-one infants were included in this subgroup, of which 29 could be analyzed [n = 15 (median GA 28.4 weeks) and n = 14 (median GA 27.9 weeks) for the 100 and 30% oxygen group, respectively]. Tonic diaphragm activity was significantly higher in the high FiO2-group (4.3 ± 2.1 μV vs. 2.9 ± 1.1 μV; p = 0.047). The other dEMG-parameters (dEMGpeak, dEMGamp, dEMGAUC) showed consistently higher values in the high FiO2 group, but did not reach statistical significance. Average RR showed similar values in both groups (34 ± 9 vs. 32 ± 10 breaths/min for the high and low oxygen group, respectively).Conclusion: Preterm infants stabilized with an initial high FiO2 showed significantly more tonic diaphragm activity and an overall trend toward a higher level of diaphragm activity than those stabilized with an initial low FiO2. These results confirm that a high initial FiO2 after birth stimulates breathing effort, which can be objectified with dEMG.

Comparison of low and high inspiratory oxygen fraction added to lung-protective ventilation on postoperative pulmonary complications after abdominal surgery: A randomized controlled trial

Study objectiveIntraoperative lung-protective ventilation strategy has been recommended to reduce postoperative pulmonary complications (PPCs). However, the role of inspiratory oxygen fraction (FiO2) in this protection remains highly uncertain. We aimed to evaluate the effect of intraoperative low (30%) versus high (80%) FiO2 in the context of lung-protective ventilation strategy on PPCs in patients undergoing abdominal surgery. DesignProspective, two-arm, randomized controlled trial. SettingTertiary university hospital in China. PatientsA total of ASA I-III 252 patients aged ≥18, who were scheduled for elective abdominal surgery under general anesthesia were included in the study. InterventionPatients were randomly assigned to receive either 30% or 80% FiO2 during the intraoperative period. All patients received volume-controlled mechanical ventilation with lung-protective ventilation approach, which included a tidal volume of 8 ml kg−1 of predicted body weight, a positive end-expiratory pressure level of 6–8 cmH2O, and repeated recruitment maneuvers. MeasurementsThe primary outcome was a composite of postoperative pulmonary complications within the first 7 postoperative days, consisting of respiratory infection, respiratory failure, bronchospasm, atelectasis, pleural effusion, pneumothorax, and aspiration pneumonitis. The severity grade of PPCs was measured as a key secondary outcome. Main resultsTwo hundred and fifty-one patients completed the trial. PPCs occurred in 43 of 125 (34.4%) patients assigned to receive 30% FiO2 compared with 59 of 126 (46.8%) patients receiving 80% FiO2 (relative risk 0.74, 97.5% confidence interval, 0.51–1.02, p = 0.045, > 0.025). The severity of PPCs within the first 7 days following surgery was attenuated significantly in the low (30%) FiO2 group (p = 0.001). ConclusionsAmong patients undergoing abdominal surgery under general anesthesia, an intraoperative lung-protective ventilation strategy with 30% FiO2 compared with 80% FiO2 did not reduce the incidence of PPCs. And the use of 30% FiO2 resulted in less severe pulmonary complications.

Lung ultrasound score to determine the effect of fraction inspired oxygen during alveolar recruitment on absorption atelectasis in laparoscopic surgery: a randomized controlled trial

BackgroundAlthough the intraoperative alveolar recruitment maneuver (RM) efficiently treats atelectasis, the effect of Fio2 on atelectasis during RM is uncertain. We hypothesized that a high Fio2 (1.0) during RM would lead to a higher degree of postoperative atelectasis without benefiting oxygenation when compared to low Fio2 (0.4).MethodsIn this randomized controlled trial, patients undergoing elective laparoscopic surgery in the Trendelenburg position were allocated to low- (Fio2 0.4, n = 44) and high-Fio2 (Fio2 1.0, n = 46) groups. RM was performed 1-min post tracheal intubation and post changes in supine and Trendelenburg positions during surgery. We set the intraoperative Fio2 at 0.4 for both groups and calculated the modified lung ultrasound score (LUSS) to assess lung aeration after anesthesia induction and at surgery completion. The primary outcome was modified LUSS at the end of the surgery. The secondary outcomes were the intra- and postoperative Pao2 to Fio2 ratio and postoperative pulmonary complications.ResultsThe modified LUSS before capnoperitoneum and RM (P = 0.747) were similar in both groups. However, the postoperative modified LUSS was significantly lower in the low Fio2 group (median difference 5.0, 95% CI 3.0–7.0, P < 0.001). Postoperatively, substantial atelectasis was more common in the high-Fio2 group (relative risk 1.77, 95% CI 1.27–2.47, P < 0.001). Intra- and postoperative Pao2 to Fio2 were similar with no postoperative pulmonary complications. Atelectasis occurred more frequently when RM was performed with high than with low Fio2; oxygenation was not benefitted by a high-Fio2.ConclusionsIn patients undergoing laparoscopic surgery in the Trendelenburg position, absorption atelectasis occurred more frequently with high rather than low Fio2. No oxygenation benefit was observed in the high-Fio2 group.Trial registrationClinicalTrials.gov, NCT03943433. Registered 7 May 2019,

Effects on Humidification and Ventilatory Parameters of Three Single-limb Heated-wired Circuits for Non-invasive Ventilation: A Bench Study

BackgroundThe objective of this study was to evaluate the effects of three single-limb heated wired circuits (SLHWC) for NIV, on ventilatory parameters and humidification performance in a simulation lung model. MethodsThree SLHWC compatible with the MR-850 Heated Humidifier (HH) (Fisher & Paykel, Auckland, New Zealand) were tested: RT-319 (FP) (Fisher & Paykel, Auckland, New Zealand), Respironics 1045770 (RP) (DEAS, Castel Bolognese, Italy) and Intersurgical B/SYS 5809001 (IT) (Intersurgical, Wokingham, UK). A Bipap Vision ventilator (Philips Respironics, Murrysville, PA, USA) in pressure control ventilation (PCV) connected to a test lung was used for simulation. Each SHWC performance was evaluated in four ventilatory conditions: IPAP of 15cmH2O with FiO2 0.3 and 1, respectively; and, IPAP of 25cmH2O with FiO2 0.3 and 1, respectively. EPAP was set at 5cmH2O. Hygrometric and ventilatory measurements including: relative humidity (RH), temperature (T), Pplat, PIP, PEEP, peak inspiratory flow (PIF), and tidal volume (Vt) were measured. ResultsIn each FiO2 group absolute humidity (AH) was similar with FP regardless of the IPAP level employed compared to IT and RP (P<.001). Except for RP at FiO2 0.3, AH increased significantly in IT and RP groups as IPAP increased (P<.001). PIP, Pplat, PEEP, PIF, and Vt values were significantly higher with FP and RP in each FiO2 group compared to IT (P<.001). ConclusionsHumidification performance varied significantly among the three circuits, being FP the only one able to maintain stable AH values during the study with no influence on ventilatory parameters.

Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy: a randomised controlled trial

BackgroundWe aimed to examine whether using a high fraction of inspired oxygen (FIO2) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery. MethodsWe performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO2 during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality. ResultsWe enrolled 740 subjects: 371 in the high FIO2 group and 369 in the low FIO2 group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO2 groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59–1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48–1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups. ConclusionsAn oxygenation strategy using high FIO2 compared with conventional FIO2 did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found. Clinical trial registrationNCT02776046.

Effects on Humidification and Ventilatory Parameters of Three Single-limb Heated-wired Circuits for Non-invasive Ventilation: A Bench Study

BackgroundThe objective of this study was to evaluate the effects of three single-limb heated wired circuits (SLHWC) for NIV, on ventilatory parameters and humidification performance in a simulation lung model. MethodsThree SLHWC compatible with the MR-850 Heated Humidifier (HH) (Fisher & Paykel, Auckland, New Zealand) were tested: RT-319 (FP) (Fisher & Paykel, Auckland, New Zealand), Respironics 1045770 (RP) (DEAS, Castel Bolognese, Italy) and Intersurgical B/SYS 5809001 (IT) (Intersurgical, Wokingham, UK). A Bipap Vision ventilator (Philips Respironics, Murrysville, PA, USA) in pressure control ventilation (PCV) connected to a test lung was used for simulation. Each SHWC performance was evaluated in four ventilatory conditions: IPAP of 15cmH2O with FiO2 0.3 and 1, respectively; and, IPAP of 25cmH2O with FiO2 0.3 and 1, respectively. EPAP was set at 5cmH2O. Hygrometric and ventilatory measurements including: relative humidity (RH), temperature (T), Pplat, PIP, PEEP, peak inspiratory flow (PIF), and tidal volume (Vt) were measured. ResultsIn each FiO2 group absolute humidity (AH) was similar with FP regardless of the IPAP level employed compared to IT and RP (P<.001). Except for RP at FiO2 0.3, AH increased significantly in IT and RP groups as IPAP increased (P<.001). PIP, Pplat, PEEP, PIF, and Vt values were significantly higher with FP and RP in each FiO2 group compared to IT (P<.001). ConclusionsHumidification performance varied significantly among the three circuits, being FP the only one able to maintain stable AH values during the study with no influence on ventilatory parameters.