High-Flow and Low-Flow Oxygen Delivery by Nasal Cannula Evaluated in Infant and Adult Airway Replicas

BACKGROUND

The nasal cannula is widely regarded as a safe and effective means of administering low- and high-flow oxygen to patients irrespective of their age. However, variability in delivered oxygen concentration (FDO2 FDO2 ) via nasal cannula has the potential to pose health risks. The present study aimed to evaluate predictive equations for FDO2 over a large parameter space, including variation in breathing, oxygen flow, and upper-airway geometry representative of both young children and adults.

METHODS

Realistic nasal airway geometries were previously collected from medical scans of adults, infants, and neonates. Nasal airway replicas based on these geometries were used to measure the FDO2 for low-flow oxygen delivery during simulated spontaneous breathing. The present study extends previously published data sets to include higher oxygen flows. The extended data sets included nasal cannula oxygen flows that ranged from 6 to 65 L/min for the adult replicas, and from 0.5 to 6 L/min for the infant replicas. For both age groups, FDO2 was measured over a range of breathing frequencies, inspiratory to expiratory time ratios, and tidal volumes. Measured FDO2 values were compared with values predicted by using a previously derived flow-weighted equation.

RESULTS

For both age groups, FDO2 was observed to increase nonlinearly with the ratio between oxygen flow supplied to the nasal cannula and the average inhalation flow. The previously derived flow-weighted equation over-predicted FDO2 at higher oxygen flows. A new empirical equation, therefore, was proposed to predict FDO2 for either age group as a function of nasal cannula flow, tidal volume, and inspiratory time. Predicted FDO2 values matched measured values, with average relative errors of 2.4% for infants and 4.3% for adults.

CONCLUSIONS

A new predictive equation for FDO2 was obtained that accurately matched measured data in both adult and infant airway replicas for low- and high-flow regimens.

True intratracheal oxygen concentration delivered by SentriO Oxy™ masks under various respiratory conditions: a bench study

SentriO Oxy™ is a newly available, Food and Drug Administration-approved oxygenation mask system that provides high oxygenation, even on low-flow (5-10 L/min) oxygen. This study aimed to accurately measure the intratracheal fraction of inspired oxygen (FiO2) using SentriO Oxy™ masks under relatively low oxygen flow rates. A manikin-ventilator-test lung simulation system was used. We measured FiO2 at the level of the carina, 5 minutes after applying 45 different respiratory parameter combinations using SentriO Oxy™ masks. Tidal volume (TV) was set to 300, 500, and 700 mL; respiratory rate (RR) was set to 8, 12, 16, 20, and 24 breaths per minute; and oxygen flow rate was set to 6, 8, and 10 L/min. Our hypothesis was that FiO2 would be proportional to the difference between oxygen flow rate and minute ventilation. FiO2 measured by smaller TV, lower RR, or higher oxygen flows revealed a significantly higher value, confirming our hypothesis. In addition, using linear regression analysis, we found that TV, RR, and oxygen flow were all significant factors influencing the measured FiO2. Our experiment proposed two prediction equations considering the oxygen flow rate, TV, and RR. The results of our study may provide information and prediction of FiO2 for clinicians to use SentriO Oxy™ masks during sedative anesthetic procedures under low oxygen flow rates.

Early factors associated with continuous positive airway pressure failure in moderate and late preterm infants

To determine the early factors associated with continuous positive airway pressure (CPAP) failure in moderate-to-late preterm infants (32 + 0/7 to 36 + 6/7 weeks' gestation) from the NEOBS cohort study. The NEOBS study was a multi-center, prospective, observational study in 46 neonatal intensive care units in France, which included preterm and late preterm infants with early neonatal respiratory distress. This analysis included a subset of the NEOBS population who had respiratory distress and required ventilatory support with CPAP within the first 24 h of life. CPAP failure was defined as the need for tracheal intubation within 72 h of CPAP initiation. Maternal and neonatal clinical parameters in the delivery room and clinical data at 3 h of life were analyzed. CPAP failure occurred in 45/375 infants (12%), and compared with infants with CPAP success, they were mostly singletons (82.2% vs. 62.1%; p < 0.01), had a lower Apgar score at 10 min of life (9.1 ± 1.3 vs. 9.6 ± 0.8; p = 0.02), and required a higher fraction of inspired oxygen (FiO2; 34.4 ± 15.9% vs. 22.8 ± 4.1%; p < 0.0001) and a higher FiO2*positive end-expiratory pressure (PEEP) (1.8 ± 0.9 vs. 1.1 ± 0.3; p < 0.0001) at 3 h. FiO2 value of 0.23 (R2 = 0.73) and FiO2*PEEP of 1.50 (R2 = 0.75) best predicted CPAP failure. The risk of respiratory distress and early CPAP failure decreased 0.7 times per 1-week increase in gestational age and increased 1.7 times with every one-point decrease in Apgar score at 10 min and 19 times with FiO2*PEEP > 1.50 (vs. ≤ 1.50) at 3 h (R2 of the overall model = 0.83).  Conclusion: In moderate-to-late preterm infants, the combination of singleton pregnancy, lower Apgar score at 10 min, and FiO2*PEEP > 1.50 at 3 h can predict early CPAP failure with increased accuracy. What is Known: •Respiratory distress syndrome (RSD) represents an unmet medical need in moderate-to-late preterm births and is commonly treated with continuous positive airway pressure (CPAP) to reduce mortality and the need for additional ventilatory support. • Optimal management of RSD is yet to be established, with several studies suggesting that identification of predictive factors for CPAP failure can aid in the prompt treatment of infants likely to experience this failure. What is New: •Secondary analysis of the observational NEOBS study indicated that oxygen requirements during CPAP therapy, especially the product of fraction of inspired oxygen (FiO2) and positive end-expiratory pressure (PEEP), are important factors associated with early CPAP failure in moderate-to-late term preterm infants. •The combination of a singleton pregnancy, low Apgar score at 10 minutes, and high FiO2*PEEP at 3 hours can predict early CPAP failure with increased accuracy, highlighting important areas for future research into the prevention of CPAP failure.

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

BACKGROUND

There 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.

METHODS

We 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.

RESULTS

In 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.

CONCLUSIONS

Compared with 60% FiO2, the use of 30% FiO2 during mechanical ventilation does not reduce the postoperative atelectasis volume.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ( http://www.chictr.org.cn ). Identifier: ChiCTR1900021635. Date: 2 March 2019. Principal invetigator: Weidong Gu.

Improvement in vocal-cord visualization with Trachway video intubating stylet using direct oxygen flow and effective analysis of the fraction of inspired oxygen: a bench study

The Trachway video intubating stylet device facilitates the visualization of the airways of patients from the tip of an endotracheal tube (ETT) during intubation. The major limitations of Trachway are the restricted view due to secretions and the risk of a prolonged apnea during intubation. We conducted a bench study to verify the performance of an alternative, easily applicable airway device that allows better visualization of trackways during Trachway-assisted intubation and prevents the detrimental effects of apnea-related hypoxia. We conducted a bench study to thoroughly evaluate the oral-secretion-elimination ability of a newly designed oxygen delivery device (ODD) to improve vocal-cord visualization using the three commonly used ETT sizes (i.e., 7, 7.5, and 8 mm). Moreover, we measured the fraction of inspired oxygen (FiO2) under different, continuous oxygen-flow supplies (1-10 L/min) during intubation. Each condition was analyzed for a 2 min video-stylet-intubation period. The supplemental oxygen flow and FiO2 fraction achieved using our ODD were higher, and smaller ETTs exhibited better secretion elimination. The ODD, which can be easily coupled with Trachway stylets, enabled high-quality visualization during oxygen flows of 6-8 L/min, and higher FiO2 fractions were achieved at higher oxygen flow rates. The use of the ODD improved the visualization of the airways during video stylet-assisted intubations using the additional FiO2 supply. The ODD developed in this study improves the visualization of airways with Trachway stylets and enhances the safety of intubation.

Impact of surgical masks on fraction of inspired oxygen during oxygen therapy depends on the type of oxygen masks and respiratory conditions: volunteer- and simulation-based studies

Purpose

We investigated the impact of surgical masks (SM) during oxygen therapy using oxygen masks in volunteer- and simulation-based studies.

Methods

Fifteen volunteers wore the Hudson RCI^® or Open-Face Mask^® with/without an SM. The fraction of inspired oxygen concentration (FIO₂), end-tidal CO₂ (EtCO₂), partial pressure of inspired CO₂ (PICO₂), and respiratory rate (RR) were measured. The oxygen flow rate increased from 0 to 10 L/min. In the simulation-based study, FIO₂ was measured using a simulator that reproduced spontaneous breathing. RR was 12 or 24 bpm, and the tidal volume (Tv) was 300, 500, or 700 mL. The effect of oxygen mask fitting conditions was also examined. The primary outcome measure was FIO₂ at 6 L/min.

Results

In the volunteer-based study, FIO₂ was reduced when the SM was used with the Hudson RCI^® or Open-Face Mask^®. The FIO₂ drop was larger with the Open-Face Mask^® than with the Hudson RCI^®. The RR, EtCO₂, and PICO₂ significantly changed with the SM, but the differences were not clinically meaningful. In the simulation-based study, the SM with the Hudson RCI^® did not reduce FIO₂, but the SM with the Open-Face Mask^® significantly decreased FIO₂ under several conditions. However, the SM with the Hudson Mask^® reduced FIO₂ when the fit of the mask was inadequate. With the Open-Face Mask^®, lower RR and Tv resulted in larger differences in FIO₂.

Conclusions

The SM decreased FIO₂ during oxygen therapy with oxygen masks. The impact of SM depended on the type of the oxygen mask, mask fitting, and respiratory condition.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00540-022-03083-2.

Effects of wearing surgical masks on fraction of inspired oxygen in spontaneously breathing patients: improving safety for frontline healthcare professionals under pandemic situations

BACKGROUND

During pandemic situations, many guidelines recommend that surgical masks be worn by both healthcare professionals and infected patients in healthcare settings. The purpose of this study was to clarify the levels and changes of oxygen concentration over time while oxygen was administered over a surgical mask.

METHODS

Patients scheduled to undergo general anesthesia (n = 99) were enrolled in this study. First, patients were administered oxygen at 6 L/min via an oxygen mask over a surgical mask for 5 min. The patients removed the surgical mask and then took a 3-min break; thereafter, the same amount of oxygen was administered for another 5 min via the oxygen mask. We measured the fraction of inspired oxygen (FiO₂), the end-tidal CO₂ (EtCO₂), and respiratory frequency every minute for 5 min, both while administering oxygen with and without a surgical mask. The FiO₂ was measured at the beginning of inspiration and the EtCO₂ was measured at the end of expiration.

RESULTS

The FiO₂ at 5 min was significantly lower when breathing with a surgical mask than that without it (mean difference: 0.08 [95% CI: 0.067-0.10]; p <  0.001). In contrast, the EtCO₂ at 5 min was significantly higher when breathing with a surgical mask than that without it (mean difference: 11.9 mmHg [95% CI: 10.9-12.9]; p <  0.001).

CONCLUSION

The FiO₂ was lower when oxygen was administered over surgical masks than when patients did not wear surgical masks. Oxygen flow may need to be adjusted in moderately ill patients requiring oxygen administration.

Variability in low-flow oxygen delivery by nasal cannula evaluated in neonatal and infant airway replicas

BACKGROUND

The nasal cannula is considered a trusted and effective means of administering low-flow oxygen and is widely used for neonates and infants requiring oxygen therapy, despite an understanding that oxygen concentrations delivered to patients are variable.

METHODS

In the present study, realistic nasal airway replicas derived from medical scans of children less than 3 months old were used to measure the fraction of oxygen inhaled (FiO₂) through nasal cannulas during low-flow oxygen delivery. Parameters influencing variability in FiO₂ were evaluated, as was the hypothesis that measured FiO₂ values could be predicted using a simple, flow-weighted calculation that assumes ideal mixing of oxygen with entrained room air. Tidal breathing through neonatal and infant nasal airway replicas was controlled using a lung simulator. Parameters for nasal cannula oxygen flow rate, nasal airway geometry, tidal volume, respiratory rate, inhalation/exhalation, or I:E ratio (t_i/t_e), breath waveform, and cannula prong insertion position were varied to determine their effect on measured FiO₂. In total, FiO₂ was measured for 384 different parameter combinations, with each combination repeated in triplicate. Analysis of variance (ANOVA) was used to assess the influence of parameters on measured FiO₂.

RESULTS

Measured FiO₂ was not appreciably affected by the breath waveform shape, the replica geometry, or the cannula position but was significantly influenced by the tidal volume, the inhalation time, and the nasal cannula flow rate.

CONCLUSIONS

The flow-weighted calculation overpredicted FiO₂ for measured values above 60%, but an empirical correction to the calculation provided good agreement with measured FiO₂ across the full range of experimental data.

Effect of ventilation strategy during cardiopulmonary bypass on postoperative pulmonary complications after cardiac surgery: a randomized clinical trial

BACKGROUND

To determine whether maintaining ventilation during cardiopulmonary bypass (CPB) with a different fraction of inspired oxygen (FiO₂) had an impact on the occurrence of postoperative pulmonary complications (PPCs).

METHODS

A total of 413 adult patients undergoing elective cardiac surgery with CPB were randomly assigned into three groups: 138 in the NoV group (received no mechanical ventilation during CPB), 138 in the LOV group (received a tidal volume (V_T) of 3-4 ml/kg of ideal body weight with the respiratory rate of 10-12 bpm, and the positive end-expiratory pressure of 5-8 cmH₂O during CPB; the FiO₂ was 30%), and 137 in the HOV group (received the same ventilation parameters settings as the LOV group while the FiO₂ was 80%).

RESULTS

The primary outcomes were the incidence and severity of PPCs during hospitalization. The composite incidence of PPCs did not significantly differ between the NoV (63%), LOV (49%) and HOV (57%) groups (P = 0.069). And there was also no difference regarding the incidence of PPCs between the non-ventilation (NoV) and ventilation (the combination of LOV and HOV) groups. The LOV group was observed a lower proportion of moderate and severe pulmonary complications (grade ≥ 3) than the NoV group (23.1% vs. 44.2%, P = 0.001).

CONCLUSION

Maintaining ventilation during CPB did not reduce the incidence of PPCs in patients undergoing cardiac surgery.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR1800015261. Prospectively registered 19 March 2018. http://www.chictr.org.cn/showproj.aspx?proj=25982.

Conservative oxygen supplementation versus usual oxygen supplementation among septic medical intensive care units patients: A before-after investigation

Patients admitted in the intensive care unit (ICU) are always managed with excessive high fraction of inspired oxygen and have hyperoxia for a significant period of time, which has potential harms. The guidelines for the management of patients in ICUs do not provide the target values for partial pressure of oxygen or arterial oxyhemoglobin saturations. The study was a before-after investigation comparing two time periods in which different oxygenation strategies were applied. Data of oxygen control, outcome measures, and mortality of a total of 273 patients (>18 years) admitted at least for 2 days in ICUs and received treatment for the sepsis were retrospectively collected and analyzed. Patients were received usual oxygen supplementation (targeted partial pressure of oxygen: 150 mmHg; a high fraction of inspired oxygen: 0.4; UOS cohort; n = 142) or conservative oxygen supplementation (targeted partial pressure of oxygen: 70-100 mmHg; a high fraction of inspired oxygen as low as possible; COS cohort; n = 131). Mechanical ventilation-free hours were significantly higher for patients of COS cohort than those of UOS cohort (77.99 ± 21.26 h/patient vs 70.01 ± 23.57 h/patient, p = 0.016). ICUs length of stays of patients of COS cohort was fewer than those of UOS cohort (7.05 ± 2.13 days/patient vs 7.69 ± 2.43 days/patients, p = 0.016). The probability of survival of patients was higher among patients of COS cohort than those of UOS cohort (p = 0.049). A higher number of patients from UOS cohort needed vasopressors than those from COS cohort (55 vs 35, p = 0.039). Conservative oxygen supplementation to maintain partial pressure of oxygen was improved outcome measures and decreases mortality as compared to that of usual oxygen supplementation.Level of Evidence: III.Technical Efficacy Stage: 4.

Intensivists' response to hyperoxemia in mechanical ventilation patients: The status quo and related factors

BACKGROUND

Due to the still sparse literature in China, the investigation of hyperoxemia management is required. Thus, we aim to conduct a retrospective study to provide more information about hyperoxemia management in intensive care unit (ICU) patients.

METHODS

We retrospectively screened the medical records of adult patients (age ≥18 years) who required mechanical ventilation (MV) ≥24 hours from January 1, 2018, to December 31, 2018. All arterial blood gas (ABG) tested during MV was retrieved, and MV settings were recorded. The median arterial partial pressure of oxygen (PaO₂) >120 mmHg (1 mmHg=0.133 kPa) was defined as mild to moderate hyperoxemia, and PaO₂ >300 mmHg as extreme hyperoxemia. Intensivists' response to hyperoxemia was assessed based on the reduction of fraction of inspired oxygen (FiO₂) within one hour after hyperoxemia was recorded. Multivariable logistic regression analysis was performed to determine the independent factors associated with the intensivists' response to hyperoxemia.

RESULTS

A total of 592 patients were finally analyzed. The median Acute Physiology and Chronic Health Evaluation II (APACHE II) score was 21 (15-26). The PaO₂, arterial oxygen saturation (SaO₂), FiO₂, and positive end expiratory pressure (PEEP) were 96.4 (74.0-126.0) mmHg, 97.8% (95.2%-99.1%), 0.4 (0.4-0.5), and 5 (3-6) cmH₂O, respectively. Totally 174 (29.39%) patients had PaO₂ >120 mmHg, and 19 (3.21%) patients had extreme hyperoxemia at PaO₂ >300 mmHg. In cases of mild to moderate hyperoxemia with FiO₂ ≤0.4, only 13 (2.20%) patients had a decrease in FiO₂ within one hour. The multivariable logistic regression analysis showed that a positive response was independently associated with FiO₂ (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.06-1.12, P<0.001), PaO₂ (OR 1.01, 95% CI 1.00-1.01, P=0.002), and working shifts (OR 5.09, 95% CI 1.87-13.80, P=0.001).

CONCLUSIONS

Hyperoxemia occurs frequently and is neglected in most cases, particularly when mild to moderate hyperoxemia, hyperoxemia with lower FiO₂, hyperoxemia during night and middle-night shifts, or FiO₂ less likely to be decreased. Patients may be at a risk of oxygen toxicity because of the liberal oxygen strategy. Therefore, further research is needed to improve oxygen management for patients with MV in the ICUs.

PROtective Ventilation with a low versus high Inspiratory Oxygen fraction (PROVIO) and its effects on postoperative pulmonary complications: protocol for a randomized controlled trial

BACKGROUND

Postoperative pulmonary complications (PPCs) are the most common perioperative complications following surgical site infection (SSI). They prolong the hospital stay and increase health care costs. A lung-protective ventilation strategy is considered better practice in abdominal surgery to prevent PPCs. However, the role of the inspiratory oxygen fraction (FiO₂) in the strategy remains disputed. Previous trials have focused on reducing SSI by increasing the inhaled oxygen concentration but higher FiO₂ (80%) was found to be associated with a greater incidence of atelectasis and mortality in recent research. The trial aims at evaluating the effect of different FiO₂ added to the lung-protective ventilation strategy on the incidence of PPCs during general anesthesia for abdominal surgery.

METHODS AND DESIGN

PROtective Ventilation with a low versus high Inspiratory Oxygen fraction trial (PROVIO) is a single-center, prospective, randomized controlled trial planning to recruit 252 patients undergoing abdominal surgery lasting for at least 2 h. The patients will be randomly assigned to (1) a low-FiO₂ (30% FiO₂) group and (2) a high-FiO₂ (80% FiO₂) group in the lung-protective ventilation strategy. The primary outcome of the study is the occurrence of PPCs within the postoperative 7 days. Secondary outcomes include the severity grade of PPCs, the occurrence of postoperative extrapulmonary complications and all-cause mortality within the postoperative 7 and 30 days.

DISCUSSION

The PROVIO trial assesses the effect of low versus high FiO₂ added to a lung-protective ventilation strategy on PPCs for abdominal surgery patients and the results should provide practical approaches to intraoperative oxygen management.

TRIAL REGISTRATION

www.ChiCTR.org.cn , identifier: ChiCTR18 00014901 . Registered on 13 February 2018.

Dose variability of supplemental oxygen therapy with open patient interfaces based on in vitro measurements using a physiologically realistic upper airway model

BACKGROUND

Supplemental oxygen therapy is widely used in hospitals and in the home for chronic care. However, there are several fundamental problems with the application of this therapy such that patients are often exposed to arterial oxygen concentrations outside of the intended target range. This paper reports volume-averaged tracheal oxygen concentration measurements (FtO2) from in vitro experiments conducted using a physiologically realistic upper airway model. The goal is to provide data to inform a detailed discussion of the delivered oxygen dose.

METHODS

A baseline FtO2 dataset using a standard, straight adult nasal cannula was established by varying tidal volume (Vt), breathing frequency (f), and continuous oxygen flow rate (QO2) between the following levels to create a factorial design: Vt = 500, 640, or 800 ml; f = 12, 17, or 22 min- 1; QO2 = 2, 4, or 6 l/min. Further experiments were performed to investigate the influence on FtO2 of variation in inspiratory/expiratory ratio, inclusion of an inspiratory or expiratory pause, patient interface selection (e.g. nasal cannula versus a facemask), and rapid breathing patterns in comparison with the baseline measurements.

RESULTS

Oxygen concentration measured at the trachea varied by as much as 60% (i.e. from 30.2 to 48.0% of absolute oxygen concentration) for the same oxygen supply flow rate due to variation in simulated breathing pattern. Among the baseline cases, the chief reasons for variation were 1) the influence of variation in tidal volume leading to variable FiO2 and 2) variation in breathing frequency affecting volume of supplemental oxygen delivered through the breath.

CONCLUSION

For oxygen administration using open patient interfaces there was variability in the concentration and quantity of oxygen delivered to the trachea over the large range of scenarios studied. Of primary importance in evaluating the oxygen dose is knowledge of the breathing parameters that determine the average inhalation flow rate relative to the oxygen flow rate. Otherwise, the oxygen dose cannot be determined.

Fraction of Inspired Oxygen as a Predictor of CPAP Failure in Preterm Infants with Respiratory Distress Syndrome: A Prospective Multicenter Study

INTRODUCTION

There are limited data available regarding the fraction of inspired oxygen (FiO2) predictive of the failure of continuous positive airway pressure (CPAP) in preterm infants with respiratory distress syndrome (RDS). Therefore, we investigated factors predictive of CPAP failure in the first 72 h of life, with special attention to the prognostic role of FiO2.

METHODS

This multicenter, prospective study enrolled infants <30 weeks gestation in whom CPAP was initiated within the first 15 min after birth. In the univariate and multivariate logistic regression models, demographic, perinatal, and respiratory parameters were analyzed. The FiO2 threshold was determined with ROC curve analysis.

RESULTS

Of 389 recruited newborns, CPAP failure occurred in 108 infants (27.8%). In the univariate model, each gestational week reduced the odds of CPAP failure by 19%, and each 100 g of birth weight reduced the odds by 16% (both p < 0.05). The risk was increased by 4.2 and 7.5% for each 0.01 increase in FiO2in the first and second hours of life, respectively. In the final multivariate model, birth weight and FiO2 in the second hour of life were the predictive measures. The prognostic threshold was FiO2 = 0.29 in the second hour of life (AUC 0.7; p < 0.0001), with a sensitivity of 73% and a specificity of 57%. CPAP failure implied a more than 20-fold higher risk of death and pneumothorax and a 2- to 5-fold higher risk of typical complications of prematurity, including bronchopulmonary dysplasia and severe intraventricular hemorrhage.

CONCLUSION

FiO2 in the second hour of life is a significantpredictor of CPAP failure. The threshold of 0.29 best discriminates the CPAP outcome. Nonresponders to CPAP have a remarkably higher incidence of complications and a higher mortality rate.

Oxygen management in mechanically ventilated patients: A multicenter prospective observational study

PURPOSE

To observe arterial oxygen in relation to fraction of inspired oxygen (F_IO₂) during mechanical ventilation (MV).

MATERIALS AND METHODS

In this multicenter prospective observational study, we included adult patients required MV for >48h during the period from March to May 2015. We obtained F_IO₂, PaO₂ and SaO₂ from commencement of MV until the 7th day of MV in the ICU.

RESULTS

We included 454 patients from 28 ICUs in this study. The median APACHE II score was 22. Median values of F_IO₂, PaO₂ and SaO₂ were 0.40, 96mmHg and 98%. After day two, patients spent most of their time with a F_IO₂ between 0.3 and 0.49 with median PaO₂ of approximately 90mmHg and SaO₂ of 97%. PaO₂ was ≥100mmHg during 47.2% of the study period and was ≥130mmHg during 18.4% of the study period. F_IO₂ was more likely decreased when PaO₂ was ≥130mmHg or SaO₂ was ≥99% with a F_IO₂ of 0.5 or greater. When F_IO₂ was <0.5, however, F_IO₂ was less likely decreased regardless of the value of PaO₂ and SaO₂.

CONCLUSIONS

In our multicenter prospective study, we found that hyperoxemia was common and that hyperoxemia was not corrected.

Minimum oxygen flow needed for vital support during simulated post-cardiorespiratory arrest resuscitation

According to the ERC and the AHA guidelines, FiO2 should be titrated to achieve an O2Sat ≥ 94%. The aim of this study was to determine the minimum oxygen flow and time needed to reach an FiO2 of 0.32 and 0.80 during post-cardiac arrest care. An experimental analysis was performed that consisted of a simulated post-cardiac arrest situation. Different resuscitators were tested and connected to an artificial lung: Mark IV, SPUR II, Revivator Res-Q, O-TWO. The oxygen flow levels tested were 2, 5, 10 and 15 lpm. Bonferroni and Mann-Whitney U tests were used. An FiO2 of 0.32 or more was obtained using any of the oxygen flow and resuscitators. Only the Mark IV achieved an FiO2 of 0.80 after a minimum of 75s ventilating with 2 or 5 lpm. Clinical and statistical differences (P<.05) were found: at 15 lpm it took 35s to reach an FiO2 of 0.80 or more for Mark IV (85.6 [0.3]) and Revivator (84.3 [1.5]) compared to 50s for SPUR II (87.1 [6.4]); at 2 lpm, all of the devices reached an FiO2 of ≥ 0.32 at 30s(Mark IV (34.8 [1.3]), Revivator (35.7 [1.5]) and SPUR II (34.4 [2.1]), except for O-TWO, which took 35s (36.3 [4.3]). Patients could be ventilated with any of the resuscitators using 2 lpm to obtain an FiO2 of 0.32, although possibly O-TWO would be the last option during the first 60s. In order to reach an FiO2 of 0.80, ventilating with 10 lpm should be sufficient, and preferably using Mark IV or Revivator Res-Q. In conclusion, on observing the results of our study, in any possible scenario, it would be advisable to use Revivator Res-Q or Mark IV rather than O-TWO or SPUR II.

A randomized controlled trial of two nasal continuous positive airway pressure levels after extubation in preterm infants

OBJECTIVE

To compare extubation failure rate with two ranges of nasal continuous positive airway pressure (NCPAP) in oxygen dependent preterm infants.

STUDY DESIGN

Preterm infants of birth weight 500-1000 g and gestational age 23-30 weeks, extubated for the first time during the first 6 weeks while requiring fraction of inspired oxygen ≥ 0.25, were randomly assigned to a NCPAP range of 4-6 (low NCPAP) or 7-9 (high NCPAP) cmH2O.

RESULTS

Infants were randomized to low (n = 47) or high NCPAP (n = 46) at day 16.3 ± 14.7 and 15.5 ± 12.4, respectively. Rates of extubation failure per criteria (24% vs 43%, P = .04, OR and 95% CI: 0.39 [0.16-0.96]) and re-intubation (17% vs 38%, P = .023, 0.33 [0.016-0.85]) within 96 hours were significantly lower in the high- compared with the low NCPAP group. This was mainly due to a strikingly lower failure rate in the 500-750 g birth weight strata. Duration of ventilation, bronchopulmonary dysplasia, or severe bronchopulmonary dysplasia did not differ significantly. No infant developed pneumothorax during 96 hours post-extubation.

CONCLUSIONS

Extubation failure in preterm infants with residual lung disease was lower with NCPAP range of 7-9 compared with 4-6 cmH2O. These findings suggest the need for higher distending pressure post-extubation in the more immature infants who are still oxygen dependent.

Achieving targeted pulse oximetry values in preterm infants in the delivery room

OBJECTIVE

To determine whether resuscitation teams can better maintain newborn transitional oxygen saturation (SpO₂) values within a prespecified target range using a graphical display of the targets and real-time SpO₂ data compared with using only numerical oximeter values.

STUDY DESIGN

Preterm neonates were enrolled in this prospective cohort evaluation of a change in practice. The Transitional Oxygen Targeting System (TOTS) plots real-time SpO₂ values in relation to 10th and 50th percentile SpO₂ curves, which provides a visual target. After introduction of the TOTS, the resuscitation team adjusted the fraction of inspired oxygen to maintain the SpO₂ within the target range, and before its use neonates were resuscitated in attempt to target normal transitional SpO₂ values without using the TOTS monitor. Duration of time within 10th-50th percentile values was compared between 2 cohorts, children evaluated with the TOTS and those not evaluated with the TOTS (controls).

RESULTS

A total of 40 infants were enrolled, including 20 prospectively evaluated with the TOTS and 20 controls. Mean gestational age, birth weight, total resuscitation time, duration of supplemental oxygen administration, changes in oxygen concentration, and respiratory support provided were similar in the 2 groups. The TOTS cohort spent 52% of time within the target range; the control cohort, 37% (P = .03).

CONCLUSION

SpO₂ values were maintained within a specified target range for significantly longer in preterm neonates resuscitated using the TOTS display compared with those resuscitated without TOTS.

Cerebral and peripheral regional oxygen saturation during postnatal transition in preterm neonates

OBJECTIVE

To evaluate peripheral regional oxygen saturation (rpSO₂) and cerebral regional oxygen saturation (rcSO₂) during the immediate postnatal transition in late preterm infants with and without the need for respiratory support.

STUDY DESIGN

This was a prospective observational study using near-infrared spectroscopy to evaluate changes in rpSO₂ and rcSO₂. These variables were measured during the first 15 minutes of life after elective cesarean delivery. Peripheral oxygen saturation (SpO₂) and heart rate were measured continuously by pulse oximetry, and cerebral fractional tissue oxygen extraction (cFTOE) was calculated. Two groups were compared based on their need for respiratory support: a respiratory support group and a normal transition group. Positive-pressure ventilation was delivered with a T-piece resuscitator, and oxygen was adjusted based on SpO₂ values. A Florian respiratory function monitor was used to record the ventilation variables.

RESULTS

There were 21 infants in the normal transition group and 21 infants in the respiratory support group. Changes in heart rate over time were similar in the 2 groups. SpO₂, rcSO₂, and rpSO₂ values were consistently higher in the normal transition group. In the respiratory support group, cFTOE values remained significantly elevated for a longer period.

CONCLUSION

This systematic analysis of rpSO₂, rcSO₂, and cFTOE in late preterm infants found significantly lower oxygen saturation values in infants who received respiratory support compared with a normal transition group. We hypothesize that the elevated cFTOE values in the respiratory support group represent compensation for lower oxygen delivery.