OXYGEN TOXICITY

Hyperoxia in the management of respiratory failure: A literature review

Management of respiratory failure is closely related to oxygen supplementation. Thus, its administration needed special attention according to indications to avoid the toxic effect. Oxygen supplementation in conditions of respiratory failure aims to overcome hypoxemia. Excessive oxygen exposure can cause oxygen toxicity and lead to hyperoxia. Hyperoxia is a condition in which there is an excess supply of oxygen in the tissues and organs. Clinically, respiratory failure is diagnosed if the PaO2 is less than 60 mmHg with or without an increase in carbon dioxide when the patient breathes room air. Respiratory failure is divided into acute (sudden) respiratory failure and chronic (slow) respiratory failure. The basis for managing respiratory failure consists of supportive/non-specific and causative/specific management. Oxygen should be prescribed wisely not to cause injury to organs such as the heart, lungs, eyes, nervous system, and others. Hyperoxia often occurs in managing respiratory failure, so it requires supervision, especially in administering oxygen. Oxygen should be given as needed to avoid hyperoxia. In oxygen therapy, it is necessary to pay attention to the patient's condition because each condition requires different oxygen concentrations, so dose adjustments are necessary. These conditions can be divided into critical, severe, and observation conditions. The target oxygen saturation in all these conditions is 94–98%.

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The use of oxygen therapy should not be excessive.

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Excess oxygen therapy can cause hyperoxia (oxygen toxicity).

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Oxygen therapy must be adjusted to the patient's condition.

Calling into question the future of hyperoxygenation in pregnancy

Maternal hyperoxygenation has been investigated as a potential diagnostic and therapeutic tool since the 1960s. Since then, it has been applied in many obstetric scenarios, both clinically and in the research setting. It is often administered without any determination of pre-hyperoxygenation maternal or fetal oxygen levels. Studies focussing on maternal oxygen therapy for the treatment of fetal growth restriction have been ongoing for over thirty years and there remains no clear evidence of benefit. Studies investigating the potential diagnostic or therapeutic role of maternal oxygen therapy in the setting of fetal congenital cardiac disease have reported varying success rates and some potentially worrying adverse effects. The purpose of this article is to review the effects of maternal hyperoxygenation on fetal and maternal health and to ascertain the safety of undertaking further clinical trials that employ the use of hyperoxygenation in pregnancy.

Hyperbaric Oxygen Therapy in Sports Musculoskeletal Injuries

Hyperbaric oxygen therapy (HBOT) is a well-established treatment for a variety of conditions. Hyperbaric oxygen therapy is the administration of 100% oxygen breathing in a pressure vessel at higher than atmospheric pressure (1 atmosphere absolute = 101 kPa). Typically, treatment is given daily for between 1 and 2 h at pressures of 2.0 to 2.8 ATA, depending on the indication. Sporting injuries are often treated over 3 to 10 sessions. Hyperbaric oxygen therapy has been documented to be effective and is approved in 14 medical indications by the Undersea and Hyperbaric Medical Society, including, but not limited to, carbon monoxide poisoning, compromised skin grafts and flaps, crush injuries, necrotizing soft tissue infections, and nonhealing ulcers with arterial insufficiencies. Recently, HBOT for sports musculoskeletal injuries is receiving increased attention. Hyperbaric oxygen therapy may allow injured athletes to recover faster than normal rehabilitation methods. Any reduction in collegiate and professional athletes' rehabilitation period can be financially significant for top-level sports teams; however, further research is required to confirm HBOT's benefits on sports musculoskeletal injuries. The purpose of this review to discuss the current understanding of HBOT as a treatment modality for common musculoskeletal injuries in sport medicine. Moreover, we will highlight the advantages and disadvantages of this modality, as well as relevant clinical and research applications.

Turning the Oxygen Dial: Balancing the Highs and Lows

Oxygen is both vital and toxic to life. Molecular oxygen is the most used substrate in the human body and is required for several hundred diverse biochemical reactions. The discovery of the PHD-HIF-pVHL system revolutionized our fundamental understanding of oxygen sensing and cellular adaptations to hypoxia. It deepened our knowledge of the biochemical underpinnings of numerous diseases, ranging from anemia to cancer. Cellular dysfunction and tissue pathology can result from a mismatch of oxygen supply and demand. Recent work has shown that mitochondrial disease models display tissue hyperoxia and that disease pathology can be reversed by normalization of excess oxygen, suggesting that certain disease states can potentially be treated by modulating oxygen levels. In this review, we describe cellular and organismal mechanisms of oxygen sensing and adaptation. We provide a revitalized framework for understanding pathologies of too little or too much oxygen.

Influence of intraoperative oxygen content on early postoperative graft dysfunction in living donor liver transplantation: A STROBE-compliant retrospective observational study

The aim of the present study was to investigate the role of intraoperative oxygen content on the development of early allograft dysfunction (EAD) in patients undergoing living donor liver transplantation (LDLT).This retrospective review included 452 adult patients who underwent elective LDLT. Our study population was classified into 2 groups: EAD and non-EAD. Arterial blood gas analysis was routinely performed 3 times during surgery: during the preanhepatic phase (ie, immediately after anesthetic induction); during the anhepatic phase (ie, at the onset of hepatic venous anastomosis); and during the neohepatic phase (ie, 1 hour after graft reperfusion). Arterial oxygen content (milliliters per deciliters) was derived using the following equation: (1.34 × hemoglobin [gram per deciliters] × SaO2 [%] × 0.01) + (0.0031 × PaO2 [mmHg]).The incidence of EAD occurrence was 13.1% (n = 59). Although oxygen contents at the preanhepatic phase were comparable between the 2 groups, the oxygen contents at the anhepatic and neohepatic phases were lower in the EAD group than in the non-EAD group. Patients with postoperative EAD had lower oxygen content immediately before and continuously after graft reperfusion, compared to patients without postoperative EAD. After the preanhepatic phase, oxygen content decreased in the EAD group but increased in the non-EAD group. The oxygen content and prevalence of normal oxygen content gradually increased during surgery in the non-EAD group, but not in the EAD group. Multivariable analysis revealed that oxygen content during the anhepatic phase and higher preoperative CRP levels were factors independently associated with the occurrence of EAD (area under the receiver-operating characteristic curve: 0.754; 95% confidence interval: 0.681-0.826; P < .001 in the model). Postoperatively, patients with EAD had a longer duration of hospitalization, higher incidences of acute kidney injury and infection, and experienced higher rates of patient mortality, compared to patients without EAD.Lower arterial oxygen concentration may negatively impact the functional recovery of the graft after LDLT, despite preserved hepatic vascular flow. Before graft reperfusion, the levels of oxygen content components, such as hemoglobin content, PaO2, and SaO2, should be regularly assessed and carefully maintained to ensure proper oxygen delivery into transplanted liver grafts.

De novo lung biofabrication: clinical need, construction methods, and design strategy

Chronic lung disease is the 4th leading cause of death in the United States. Due to a shortage of donor lungs, alternative approaches to support failing, native lungs have been attempted, including mechanical ventilation and various forms of artificial lungs. However, each of these support methods causes significant complications when used for longer than a few days and are thus not capable of long-term support. For artificial lungs, complications arise due to interactions between the artificial materials of the device and the blood of the recipient. A potential new approach is the fabrication of lungs from biological materials, such that the gas exchange membranes provide a more biomimetic blood-contacting interface. Recent advancements with three-dimensional, soft-tissue biofabrication methods and the engineering of thin, basement membranes demonstrate the potential of fabricating a lung scaffold from extracellular matrix materials. This scaffold could then be seeded with endothelial and epithelial cells, matured within a bioreactor, and transplanted. In theory, this fully biological lung could provide improved, long-term biocompatibility relative to artificial lungs, but significant work is needed to perfect the organ design and construction methods. Like artificial lungs, biofabricated lungs do not need to follow the shape and structure of a native lung, allowing for simpler manufacture. However, various functional requirements must still be met, including stable, efficient gas exchange for a period of years. Design decisions depend on the disease state, how the organ is implanted, and the latest biofabrication methods available in a rapidly evolving field.

Harmful effects of early hyperoxaemia in patients admitted to general wards: an observational cohort study in South Korea

OBJECTIVES

We evaluated the association between hyperoxaemia induced by a non-invasive oxygen supply for 3 days after emergency department (ED) arrival and the clinical outcomes at day 5 after ED arrival.

DESIGN

Observational cohort study.

SETTING AND PATIENTS

Consecutive ED patients ≥16 years of age with available arterial blood gas analysis results who were admitted to our hospital were enrolled from January 2010 to December 2016.

INTERVENTIONS

The highest (PaO_2MAX), average (PaO_2AVG) and median (PaO_2MED) PaO₂ (arterial oxygen pressure) values within 72 hours and the area under the curve divided by the time elapsed between ED admittance and the last PaO₂ result (AUC₇₂) were used to assess hyperoxaemia. The AUC₇₂ values were calculated using the trapezoid rule.

OUTCOMES

The primary outcome was the 90-day in-hospital mortality rate. The secondary outcomes were intensive care unit (ICU) transfer and respiratory failure at day 5 after ED arrival, as well as new-onset cardiovascular, coagulation, hepatic and renal dysfunction at day 5 after ED arrival.

RESULTS

Among the 10 141 patients, the mortality rate was 5.8%. The adjusted ORs of in-hospital mortality for PaO_2MAX, PaO_2AVG, PaO_2MED and AUC₇₂ were 0.79 (95% CI 0.61 to 1.02; p=0.0715), 0.92 (95% CI 0.69 to 1.24; p=0.5863), 0.82 (95% CI 0.61 to 1.11; p=0.2005) and 1.53 (95% CI 1.25 to 1.88; p<0.0001). All of the hyperoxaemia variables showed significant positive correlations with ICU transfer at day 5 after ED arrival (p<0.05). AUC₇₂ was positively correlated with respiratory failure, as well as cardiovascular, hepatic and renal dysfunction (p<0.05). PaO_2MAX was positively correlated with cardiovascular dysfunction. PaO_2MAX and AUC₇₂ were negatively correlated with coagulation dysfunction (p<0.05).

CONCLUSIONS

Hyperoxaemia during the first 3 days in patients outside the ICU is associated with in-hospital mortality and ICU transfer at day 5 after arrival at the ED.

A More Comprehensive Habitable Zone for Finding Life on Other Planets

The habitable zone (HZ) is the circular region around a star(s) where standing bodies of water could exist on the surface of a rocky planet. Space missions employ the HZ to select promising targets for follow-up habitability assessment. The classical HZ definition assumes that the most important greenhouse gases for habitable planets orbiting main-sequence stars are CO2 and H2O. Although the classical HZ is an effective navigational tool, recent HZ formulations demonstrate that it cannot thoroughly capture the diversity of habitable exoplanets. Here, I review the planetary and stellar processes considered in both classical and newer HZ formulations. Supplementing the classical HZ with additional considerations from these newer formulations improves our capability to filter out worlds that are unlikely to host life. Such improved HZ tools will be necessary for current and upcoming missions aiming to detect and characterize potentially habitable exoplanets.

Tumor oxygenation and cancer therapy-then and now

In 2012, cancer affected 14.1 million people worldwide and was responsible for 8.2 million deaths. The disease predominantly affects aged populations and is one of the leading causes of death in most western countries. In tumors, the aggressive growth of the neoplastic cell population and associated overexpression of pro-angiogenic factors lead to the development of disorganized blood vessel networks that are structurally and functionally different from normal vasculature. A disorganized labyrinth of vessels that are immature, tortuous and hyperpermeable typifies tumor vasculature. Functionally, the ability of the tumor vasculature to deliver nutrients and remove waste products is severely diminished. A critical consequence of the inadequate vascular networks in solid tumors is the development of regions of hypoxia [low oxygen tensions typically defined as oxygen tensions (pO₂ values) < 10 mm Hg]. Tumor cells existing in such hypoxic environments have long been known to be resistant to anticancer therapy, display an aggressive phenotype, and promote tumor progression and dissemination. This review discusses the physiological basis of hypoxia, methods of detection, and strategies to overcome the resulting therapy resistance.

Correlations between maternal and neonatal serum selenium levels in full term neonates with hypoxic ischemic encephalopathy

Perinatal hypoxic-ischemic encephalopathy (HIE) is an important cause of brain injury in the newborn and can result devastating consequences. The principle mechanisms underlying neurological damage in HIE resulting from hypoxemia and/or ischemia is deprivation of glucose and oxygen supply which energy failure. A consequent reperfusion injury often deteriorates the brain metabolism by increasing the oxidative stress damage. Selenium is a constituent of the antioxidant enzyme Glutathione peroxidase and is vital to antioxidant defense. This study aimed to measure the serum selenium levels in full term neonates with HIE and their mothers and to correlate between them and the severity of HIE.

METHODS

The study included 60 full term neonates with HIE admitted to NICU of Minia university hospital during the period from January 2014 to February 2015. Twenty apparently healthy full term neonates selected as a control group. After history taking and careful clinical examination; all neonates were subjected to: Complete blood count, renal and liver function tests and serum electrolytes. Serum selenium was measured for all neonates and their mothers within 48 h of life using atomic flame spectrophotometer method.

RESULTS

Neonates with HIE had significant lower serum selenium levels than normal healthy neonates (p = 0.001**) with the lowest levels in neonates with severe HIE but there were no significant differences between patients and controls as regards the maternal serum selenium levels. Significant negative correlations between serum selenium levels and the severity of HIE and base excess were present, while positive significant correlations were present with Apgar score and pH. There were no correlations between serum selenium levels and maternal serum selenium levels urea or creatinine levels.

CONCLUSIONS

Neonates with HIE had lower serum selenium level than normal healthy neonates which is not dependent on the maternal serum selenium levels and was negatively correlated with the severity of HIE.