Target oxygen saturation range: 92-96% Versus 94-98%

Effect of a lower target oxygen saturation range on the risk of hypoxaemia and elevated NEWS2 scores at a university hospital: a retrospective study

BACKGROUND

The optimal target oxygen saturation (SpO2) range for hospital inpatients not at risk of hypercapnia is unknown. The objective of this study was to assess the impact on oxygen usage and National Early Warning Score 2 (NEWS2) of changing the standard SpO2 target range from 94-98% to 92-96%.

METHODS

In a metropolitan UK hospital, a database of electronic bedside SpO2 measurements, oxygen prescriptions and NEWS2 records was reviewed. Logistic regression was used to compare the proportion of hypoxaemic SpO2 values (<90%) and NEWS2 records ≥5 in 2019, when the target SpO2 range was 94-98%; with 2022, when the target range was 92-96%.

RESULTS

In 2019, 218 of 224 936 (0.10%) observations on room air and 162 of 11 328 (1.43%) on oxygen recorded an SpO2 <90%, and in 2022, 251 of 225 970 (0.11%) and 233 of 12 845 (1.81%), respectively (risk difference 0.04%, 95% CI 0.02% to 0.07%). NEWS2 ≥5 was observed in 3009 of 236 264 (1.27%) observations in 2019 and 4061 of 238 815 (1.70%) in 2022 (risk difference 0.43%, 0.36% to 0.50%; p<0.001). The proportion of patients using supplemental oxygen with hyperoxaemia (SpO2 100%) was 5.4% in 2019 and 3.9% in 2022 (OR 0.71, 0.63 to 0.81; p<0.001).

DISCUSSION

The proportion of observations with SpO2 <90% or NEWS2 ≥5 was greater with the 92-96% range; however, absolute differences were very small and of doubtful clinical relevance, in contrast to hyperoxaemia for which the proportion was markedly less in 2022. These findings support proposals that the British Thoracic Society oxygen guidelines could recommend a lower target SpO2 range.

Can guidelines rein in oxygen use? A retrospective cross-sectional study using routinely collected data

Oxygen is one of the most commonly used emergency therapies. Like other therapies, oxygen can cause harm if used inappropriately. During the COVID-19 pandemic, guidelines were released to optimize oxygen and medication use. In the current study, we examine whether oxygen and medication use during the first wave of the COVID-19 pandemic was in concordance with new guidelines. A retrospective cross-sectional study was conducted using routinely collected data from University of Birmingham NHS Foundation Trust in England. Patients were admitted between April 2020 and September 2020, were over the age of 18 years, and had a confirmed diagnosis of COVID-19. To assess adherence to the oxygen guidelines (i.e. SpO2 adherence), the percentage of times oxygen therapy was administered within, over, and under guideline specifications were calculated for patients overall, and then for patients with and without chronic obstructive pulmonary disease (COPD)/pulmonary disease separately. Next, two multinomial regression analyses were conducted to assess whether clinical processes, pre-admission diagnoses, and other demographic factors were related to oxygen use. Analysis 1 included patients not diagnosed with COPD/pulmonary disease. Analysis 2 included patients diagnosed with COPD/pulmonary disease. Results are reported as tallies, percentages, and odds ratios with 95% confidence intervals. To assess adherence to a new medication guideline, the percentage of patients administered oxygen and dexamethasone was calculated for those admitted after 25 June 2020. The overall number of patients included in our SpO2 adherence analyses was 8751 (female = 4168). Oxygen was used within guideline specifications less than half the time, i.e. 41.6% (n = 3638/8751); non-adherence involving under-administering (3.5%, n = 304/8751) was markedly lower than over-administering (55.0%, n = 4809/8751). Adherence was higher for patients without COPD (43.7%, n = 3383/7741) than with COPD (25.2%, n = 255/1010). Under-administering was low across groups (non-COPD 3.5%, n = 274/7741 and COPD 2.9%, n = 30/1010). Over-administering was markedly lower for non-COPD (52.3%, n = 4084/7741) than COPD (71.8%, n = 725/1010) patients. Diagnoses associated with over-administering varied across the groups. Regarding the dexamethasone guidelines, of the 6397 patients admitted after the 24th of June, only 12.6% (n = 805) received dexamethasone. Suboptimal use of oxygen and medication were common during the first wave of the COVID-19 pandemic. As found in previous studies, over-administering was more common than under-administering. The new guidelines issued during the COVID-19 pandemic were not by themselves sufficient to optimize oxygen use. Behavioural strategies are explored which may help policymakers optimize oxygen use.

Oxygenation target in acute respiratory distress syndrome

Determining oxygenation targets in acute respiratory distress syndrome (ARDS) remains a challenge. Although oxygenation targets have been used since ARDS was first described, they have not been investigated in detail. However, recent retrospective and prospective trials have evaluated the optimal oxygenation threshold in patients admitted to the general intensive care unit. In view of the lack of prospective data, clinicians continue to rely on data from the few available trials to identify the optimal oxygenation strategy. Assessment of the cost-benefit ratio of the fraction of inspired oxygen (FiO₂) to the partial pressure of oxygen in the arterial blood (PaO₂) is an additional challenge. A high FiO₂ has been found to be responsible for respiratory failure and deaths in numerous animal models. Low and high PaO₂ values have also been demonstrated to be potential risk factors in experimental and clinical situations. The findings from this literature review suggest that PaO₂ values ranging between 80 mmHg and 90 mmHg are acceptable in patients with ARDS. The costs of rescue maneuvers needed to reach these targets have been discussed. Several recent papers have highlighted the risk of disagreement between arterial oxygen saturation (SaO₂) and peripheral oxygen saturation (SpO₂) values. In order to avoid discrepancies and hidden hypoxemia, SpO₂ readings need to be compared with those of SaO₂. Higher SpO₂ values may be needed to achieve the recommended PaO₂ and SaO₂ values.

Adaptive Responses to Hypoxia and/or Hyperoxia in Humans

Significance: Oxygen is indispensable for aerobic life, but its utilization exposes cells and tissues to oxidative stress; thus, tight regulation of cellular, tissue, and systemic oxygen concentrations is crucial. Here, we review the current understanding of how the human organism (mal-)adapts to low (hypoxia) and high (hyperoxia) oxygen levels and how these adaptations may be harnessed as therapeutic or performance enhancing strategies at the systemic level. Recent Advances: Hyperbaric oxygen therapy is already a cornerstone of modern medicine, and the application of mild hypoxia, that is, hypoxia conditioning (HC), to strengthen the resilience of organs or the whole body to severe hypoxic insults is an important preparation for high-altitude sojourns or to protect the cardiovascular system from hypoxic/ischemic damage. Many other applications of adaptations to hypo- and/or hyperoxia are only just emerging. HC-sometimes in combination with hyperoxic interventions-is gaining traction for the treatment of chronic diseases, including numerous neurological disorders, and for performance enhancement. Critical Issues: The dose- and intensity-dependent effects of varying oxygen concentrations render hypoxia- and/or hyperoxia-based interventions potentially highly beneficial, yet hazardous, although the risks versus benefits are as yet ill-defined. Future Directions: The field of low and high oxygen conditioning is expanding rapidly, and novel applications are increasingly recognized, for example, the modulation of aging processes, mood disorders, or metabolic diseases. To advance hypoxia/hyperoxia conditioning to clinical applications, more research on the effects of the intensity, duration, and frequency of altered oxygen concentrations, as well as on individual vulnerabilities to such interventions, is paramount. Antioxid. Redox Signal. 37, 887-912.

Effects of Acute Hypobaric Hypoxia Exposure on Cardiovascular Function in Unacclimatized Healthy Subjects: A "Rapid Ascent" Hypobaric Chamber Study

Background: This study aimed to observe the effects of a fast acute ascent to simulated high altitudes on cardiovascular function both in the main arteries and in peripheral circulation. Methods: We examined 17 healthy volunteers, between 18 and 50 years old, at sea level, at 3842 m of hypobaric hypoxia and after return to sea level. Cardiac output (CO) was measured with Doppler transthoracic echocardiography. Oxygen delivery was estimated as the product of CO and peripheral oxygen saturation (SpO2). The brachial artery’s flow-mediated dilation (FMD) was measured with the ultrasound method. Post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography. Results: During altitude stay, peripheral oxygen saturation decreased (84.9 ± 4.2% of pre-ascent values; p < 0.001). None of the volunteers presented any hypoxia-related symptoms. Nevertheless, an increase in cardiac output (143.2 ± 36.2% of pre-ascent values, p < 0.001) and oxygen delivery index (120.6 ± 28.4% of pre-ascent values; p > 0.05) was observed. FMD decreased (97.3 ± 4.5% of pre-ascent values; p < 0.05) and PORH did not change throughout the whole experiment. Τhe observed changes disappeared after return to sea level, and normoxia re-ensued. Conclusions: Acute exposure to hypobaric hypoxia resulted in decreased oxygen saturation and increased compensatory heart rate, cardiac output and oxygen delivery. Pre-occlusion vascular diameters increase probably due to the reduction in systemic vascular resistance preventing flow-mediated dilation from increasing. Mean Arterial Pressure possibly decrease for the same reason without altering post-occlusive reactive hyperemia throughout the whole experiment, which shows that compensation mechanisms that increase oxygen delivery are effective.

[Chronic respiratory failure correction in cicatricial laryngeal and tracheal stenosis using helium-oxygen mixture]

The article provides a review of the literature on the development of chronic respiratory failure in patients with chronic cicatricial stenosis of the larynx and cervical trachea. The authors provide data on the etiology, pathogenetic features of the course of cicatricial stenosis of the larynx and trachea, the reasons for the development of chronic respiratory failure, the effect of hypoxemia on general metabolic processes in the body and on regeneration processes, as well as on methods of their correction and improvement of the postoperative period. The methods of respiratory impact on chronic respiratory failure in these patients are considered, based on the experience of a number of researchers and technical advances in recent years.

Determination of oxygen saturation compared to a prescribed target range using continuous pulse oximetry in acutely unwell medical patients

BACKGROUND

Both inadequate and excessive administration of oxygen to acutely unwell patients results in risk of harm. Guidelines recommend titration of oxygen to achieve a target oxygen saturation (SpO2) range. Information regarding whether this is being achieved is limited.

METHODS

In this two-centre non-interventional study we used continuous pulse oximetry in acutely unwell medical patients over a 24-h period to determine the proportion of time spent with SpO2 within the prescribed target range and whether this is influenced by the target range, age, care in a high-dependency area and the number of oxygen adjustments.

RESULTS

Eighty participants were included in the analysis. The mean (SD) proportion of time spent in target range was 55.6% (23.6), this was lower in those with a reduced hypercapnic target range (88-92% or below) compared to those with a range of 92-96%; difference - 13.1% (95% CI - 3.0 to - 23.2), P = 0.012. The proportion of time spent above range was 16.2% (22.9); this was higher in those with a reduced hypercapnic range; difference 21.6% (31.4 to 12), P < 0.001. The proportion of time below range was 28.4% (25.2); there was no difference between target ranges. The proportion of time spent in range was higher for those in a high dependency area in the multivariate model; difference 15.5% (95% CI 2.3 to 28.7), P = 0.02.

CONCLUSIONS

Medical patients receiving oxygen in a ward setting spend significant periods of time with SpO2 both above and below the prescribed target range while receiving oxygen therapy.

Determining a target SpO2 to maintain PaO2 within a physiological range

OBJECTIVE

In the context of an ongoing debate on the potential risks of hypoxemia and hyperoxemia, it seems prudent to maintain the partial arterial oxygen pressure (PaO2) in a physiological range during administration of supplemental oxygen. The PaO2 and peripheral oxygen saturation (SpO2) are closely related and both are used to monitor oxygenation status. However, SpO2 values cannot be used as an exact substitute for PaO2. The aim of this study in acutely ill and stable patients was to determine at which SpO2 level PaO2 is more or less certain to be in the physiological range.

METHODS

This is an observational study prospectively collecting data pairs of PaO2 and SpO2 values in patients admitted to the emergency room or intensive care unit (Prospective Inpatient Acutely ill cohort; PIA cohort). A second cohort of retrospective data of patients who underwent pulmonary function testing was also included (Retrospective Outpatient Pulmonary cohort; ROP cohort). Arterial hypoxemia was defined as PaO2 < 60 mmHg and hyperoxemia as PaO2 > 125 mmHg. The SpO2 cut-off values with the lowest risk of hypoxemia and hyperoxemia were determined as the 95th percentile of the observed SpO2 values corresponding with the observed hypoxemic and hyperoxemic PaO2 values.

RESULTS

220 data pairs were collected in the PIA cohort. 95% of hypoxemic PaO2 measurements occurred in patients with an SpO2 below 94%, and 95% of hyperoxemic PaO2 measurements occurred in patients with an SpO2 above 96%. Additionally in the 1379 data pairs of the ROP cohort, 95% of hypoxemic PaO2 measurements occurred in patients with an SpO2 below 93%.

CONCLUSION

The SpO2 level marking an increased risk of arterial hypoxemia is not substantially different in acutely ill versus stable patients. In acutely ill patients receiving supplemental oxygen an SpO2 target of 95% maximizes the likelihood of maintaining PaO2 in the physiological range.

[Guideline for Long-Term Oxygen Therapy - S2k-Guideline Published by the German Respiratory Society]

Long-term oxygen therapy is of great importance both for reducing mortality and for improving performance in patients with chronic lung diseases. The prerequisites for Long-term oxygen therapy are adequate diagnostics and clearly defined indication. A causal distinction into chronic hypoxaemic and hypercapnic respiratory failure is reasonable, from which the differential indication for non-invasive ventilation results.The revised guideline covers the diagnostics and indication of chronic lung and heart diseases, the role of oxygen in terminal illness and gives a detailed description of available oxygen devices. The guideline is intended to help avoid undersupply, oversupply and false prescriptions. Furthermore, the chapter "Postacute Oxygen Therapy" discusses the procedure, relevant in everyday life, but not yet clearly defined, for prescribing oxygen therapy for the home at the end of an inpatient stay. Another important point, the correct prescription of mobile oxygen systems, is also presented in the guideline. This document is a revised version of the guideline for longterm oxygen therapy and replaces the version of 2008.

Intraoperative lidocaine infusion and 24-hour postoperative opioid consumption in obese patients undergoing laparoscopic bariatric surgery

BACKGROUND

Bariatric surgery is the most effective long-term treatment for obesity. Opioid-sparing anesthesia and multimodal analgesia such as lidocaine infusion have been recommended in these patients to reduce opioid-related complications. However, evidence supporting its use for bariatric surgery population is limited.

OBJECTIVE

To investigate whether intraoperative lidocaine infusion is associated with decreasing opioid consumption in laparoscopic bariatric surgery.

SETTING

A university hospital, California, USA.

METHODS

In this retrospective cohort study, outcomes among consecutive obese patients undergoing laparoscopic bariatric surgery between January 2016 to December 2018 were evaluated to determine the impact of adjunctive intraoperative lidocaine infusion on 24-hour postoperative opioid consumption. Secondary outcomes, including opioid consumption during hospitalization, length of stay, and postoperative complications were determined. Post hoc analyses were performed exploring possible dose effects and drug-drug interactions. Univariable and multivariable analyses were performed to identify factors associated with opioid consumption.

RESULTS

Among 345 patients, 54 (15.7%) received intraoperative lidocaine infusion (L+) whereas 291 (84.3%) did not receive intraoperative lidocaine infusion (L-). Both L+ and L- groups shared similar demographic characteristics. The 24-hour postoperative opioid consumption was 17.6% lower in L+ (95% confidence interval -28.4 to -5.2, P = .007), but nonsignificantly lower in the multivariate model (12.8%, 95% confidence interval -24.4 to .5, P = .06). Opioid consumption during hospitalization, length of stay, and other clinically significant outcomes did not differ. However, subgroup analysis restricted to opioid-naïve patients indicated significantly reduced opioid consumption in the L+ group. Post hoc analysis suggested interaction between lidocaine and ketamine in decreasing 24-hour postoperative opioid consumption.

CONCLUSIONS

Intraoperative lidocaine infusion was not significantly associated with decreasing 24-hour postoperative opioid consumption in obese patients undergoing laparoscopic bariatric surgery.

Nonpharmacologic Therapies in Patients With Exacerbation of Chronic Obstructive Pulmonary Disease: A Systematic Review With Meta-Analysis

OBJECTIVE

To evaluate the effectiveness and adverse events of nonpharmacologic interventions in patients with exacerbation of chronic obstructive pulmonary disease (COPD).

PATIENTS AND METHODS

We searched Embase, MEDLINE, Cochrane databases, Scopus, and clinicaltrials.gov from database inception to January 2, 2019, for randomized controlled trials that enrolled adults with exacerbation of COPD and evaluated the effect of nonpharmacologic interventions on clinical outcomes and/or lung function.

RESULTS

We included 30 randomized controlled trials with 2643 participants. Improvement in 6-minute walking test distance was associated with resistance training (weighted mean difference [WMD], 74.42; 95% CI, 46.85 to 101.99), pulmonary rehabilitation (WMD, 20.02; 95% CI, 12.06 to 28.67), whole body vibration (WMD, 89.42; 95% CI, 45.18 to 133.66), and transcutaneous electrical nerve stimulation (WMD, 64.54; 95% CI, 53.76 to 75.32). Improvement in quality of life was associated with resistance training (WMD, 18.7; 95% CI, 5.06 to 32.34), combined breathing technique and range of motion exercises (WMD, 14.89; 95% CI, 5.30 to 24.50), whole body vibration (WMD, -12.02; 95% CI, -21.41 to -2.63), and intramuscular vitamin D (WMD, -4.67; 95% CI, -6.00 to -3.35 at the longest follow-up). Oxygen titration with a target oxygen saturation range of 88% to 92% was associated with reduced mortality compared with high flow oxygen (odds ratio, 0.36; 95% CI, 0.14 to 0.88). All findings were based on low strength of evidence.

CONCLUSION

In patients hospitalized for exacerbation of COPD, exercise interventions and pulmonary rehabilitation programs may ameliorate functional decline. Oxygen should be titrated with a target oxygen saturation of 88% to 92% in these patients.

TRIAL REGISTRATION

PROSPERO Identifier: CRD42018111609.

A multicentre prospective observational study comparing arterial blood gas values to those obtained by pulse oximeters used in adult patients attending Australian and New Zealand hospitals

Background

Pulse oximetry is widely used in the clinical setting. The purpose of this validation study was to investigate the level of agreement between oxygen saturations measured by pulse oximeter (SpO₂) and arterial blood gas (SaO₂) in a range of oximeters in clinical use in Australia and New Zealand.

Methods

Paired SpO₂ and SaO₂ measurements were collected from 400 patients in one Australian and two New Zealand hospitals. The ages of the patients ranged from 18 to 95 years. Bias and limits of agreement were estimated. Sensitivity and specificity for detecting hypoxaemia, defined as SaO₂ < 90%, were also estimated.

Results

The majority of participants were recruited from the Outpatient, Ward or High Dependency Unit setting. Bias, oximeter-measured minus arterial blood gas-measured oxygen saturation, was − 1.2%, with limits of agreement − 4.4 to 2.0%. SpO₂ was at least 4% lower than SaO₂ for 10 (2.5%) of the participants and SpO₂ was at least 4% higher than the SaO₂ in 3 (0.8%) of the participants. None of the participants with a SpO₂ ≥ 92% were hypoxaemic, defined as SaO₂ < 90%. There were no clinically significant differences in oximetry accuracy in relation to clinical characteristics or oximeter brand.

Conclusions

In the majority of the participants, pulse oximetry was an accurate method to assess SaO₂ and had good performance in detecting hypoxaemia. However, in a small proportion of participants, differences between SaO₂ and SpO₂ could have clinical relevance in terms of patient monitoring and management. A SpO₂ ≥ 92% indicates that hypoxaemia, defined as a SaO₂ < 90%, is not present.

Trial registration

Australian and New Zealand Clinical Trials Registry (ACTRN12614001257651). Date of registration: 2/12/2014.

Use of excessive supplemental oxygen in mechanically ventilated patients is based on unit culture. A multiple-methods study in a regional intensive care unit

BACKGROUND

Administration of supplemental oxygen is widely used in the management of critically ill patients; however, there is evidence that excessive supplemental oxygen exposure is associated with increased mortality. There is limited research evaluating what factors clinicians take into consideration when managing oxygenation in critically ill adults.

OBJECTIVES

The purpose of this study was to explore intensive care unit (ICU) clinicians' experience and decision-making when managing supplemental oxygen therapy in mechanically ventilated patients in a regional intensive care unit.

METHODS

A multiple-methods observational study that included (i) a cross-sectional ICU staff survey and (ii) focus group discussions with critical care nurses was conducted. Descriptive statistics were used to summarise the key outcomes of the staff survey. Thematic analysis was used to analyse the focus group discussions and open-ended questions on the staff survey. The staff survey was completed by 49 ICU clinicians, and 11 critical care nurses participated in the two focus group discussions.

RESULTS

Survey data showed that staff acknowledged the problem of excessive oxygen exposure; 79.6% (n = 39) reported that the minimum acceptable fraction of inspired oxygen for mechanically ventilated patients was 0.3. The majority (89.8%, n = 44) reported that there was an interdisciplinary approach to decision-making in the unit. Two major themes were chosen from the focus group discussions and staff survey data: (i) Decision-making is based on unit culture rather than evidence and (ii) the process of weaning is driven by interdisciplinary team collaboration. Participants acknowledged that there needed to be a culture change from a liberal approach to oxygen therapy.

CONCLUSIONS

Although participants acknowledged the adverse consequences of excessive oxygen use, achieving oxygenation targets with the minimum level of supplemental oxygen was not a key focus of care. The findings highlight the need to develop and evaluate evidence-based protocols to support a conservative approach to supplemental oxygen management.

Evaluating the clinical value of the hypoxia burden index in patients with obstructive sleep apnea

PURPOSE

We aimed to develop a novel index, the hypoxia burden index (HBI), that reflects the degree and duration of oxygen desaturation, and to determine whether this index is better than the apnea hypopnea-index (AHI) for evaluating obstructive sleep apnea (OSA) and cardiovascular diseases morbidities.

METHODS

We retrospectively analyzed 459 adult subjects who underwent overnight polysomnography (PSG) in this study. The HBI was calculated by dividing the total desaturation area of SpO₂ below 90% by the TST measured in seconds. Correlations between the HBI and PSG parameters and the cardiovascular diseases (CVDs) of inpatients were explored.

RESULTS

For the 459 participants, the HBI was highly correlated with the AHI (r = 0.690), lowest oxygen saturation (SpO₂min) (r = -0.733), and proportion of cumulative sleep time with SpO₂ below 90% in total sleep time (TST) (CT90%) (r = 0.801). The HBI was mildly correlated with Epworth sleepiness scale score, morning systolic blood pressure, diastolic blood pressure, and mean arterial pressure. Among the significantly different parameters in the CVD and non-CVD groups in 202 inpatients (age, sex, the longest time of apnea, AHI, and HBI), only age, sex, and HBI [OR 1.006 (1.001-1.011), p = 0.021] were independently correlated with CVDs.

CONCLUSIONS

The HBI considers both hypoxia duration and severity during sleep. It may have potential value in predicting the clinical outcomes of OSA based on its correlation with ESS scores and morning blood pressure as well as its independent association with the prevalence of CVDs, whereas the AHI is not significantly associated with CVD prevalence.