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Respiratory Care Jul 2021Hypoxemia is common in postoperative patients and is associated with prolonged hospital stays, high costs, and increased mortality. This review discusses the... (Review)
Review
Hypoxemia is common in postoperative patients and is associated with prolonged hospital stays, high costs, and increased mortality. This review discusses the postoperative management of hypoxemia in regard to the use of conventional oxygen therapy, high-flow nasal cannula oxygen therapy, CPAP, and noninvasive ventilation. The recommendations made are based on the currently available evidence.
Topics: Cannula; Continuous Positive Airway Pressure; Humans; Hypoxia; Noninvasive Ventilation; Oxygen; Oxygen Inhalation Therapy
PubMed: 34006596
DOI: 10.4187/respcare.08929 -
Respiratory Care Oct 2014Oxygen is essential for normal aerobic metabolism in mammals. Hypoxia is the presence of lower than normal oxygen content and pressure in the cell. Causes of hypoxia... (Review)
Review
Oxygen is essential for normal aerobic metabolism in mammals. Hypoxia is the presence of lower than normal oxygen content and pressure in the cell. Causes of hypoxia include hypoxemia (low blood oxygen content and pressure), impaired oxygen delivery, and impaired cellular oxygen uptake/utilization. Many compensatory mechanisms exist at the global, regional, and cellular levels to allow cells to function in a hypoxic environment. Clinical management of tissue hypoxia usually focuses on global hypoxemia and oxygen delivery. As we move into the future, the clinical focus needs to change to assessing and managing mission-critical regional hypoxia to avoid unnecessary and potential toxic global strategies. We also need to focus on understanding and better harnessing the body's own adaptive mechanisms to hypoxia.
Topics: Adaptation, Physiological; Humans; Hypoxia; Oxygen; Oxygen Inhalation Therapy
PubMed: 25161296
DOI: 10.4187/respcare.03357 -
The European Respiratory Journal Oct 2014This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to... (Review)
Review
This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2 and PCO2) are determined by the ratio of alveolar ventilation to blood flow (V'A/Q') for each unit. Shunt and low V'A/Q' regions are two examples of V'A/Q' mismatch and are the most frequent causes of hypoxaemia. Diffusion limitation, hypoventilation and low inspired PO2 cause hypoxaemia, even in the absence of V'A/Q' mismatch. In contrast to other causes, hypoxaemia due to shunt responds poorly to supplemental oxygen. Gas exchanging units with little or no blood flow (high V'A/Q' regions) result in alveolar dead space and increased wasted ventilation, i.e. less efficient carbon dioxide removal. Because of the respiratory drive to maintain a normal arterial PCO2, the most frequent result of wasted ventilation is increased minute ventilation and work of breathing, not hypercapnia. Calculations of alveolar-arterial oxygen tension difference, venous admixture and wasted ventilation provide quantitative estimates of the effect of V'A/Q' mismatch on gas exchange. The types of V'A/Q' mismatch causing impaired gas exchange vary characteristically with different lung diseases.
Topics: Humans; Hypoxia; Lung; Lung Diseases; Models, Biological; Pulmonary Gas Exchange; Ventilation-Perfusion Ratio
PubMed: 25063240
DOI: 10.1183/09031936.00037014 -
Nature Biomedical Engineering Oct 2018Although anaesthesiologists strive to avoid hypoxemia during surgery, reliably predicting future intraoperative hypoxemia is not currently possible. Here, we report the...
Although anaesthesiologists strive to avoid hypoxemia during surgery, reliably predicting future intraoperative hypoxemia is not currently possible. Here, we report the development and testing of a machine-learning-based system that, in real time during general anaesthesia, predicts the risk of hypoxemia and provides explanations of the risk factors. The system, which was trained on minute-by-minute data from the electronic medical records of over fifty thousand surgeries, improved the performance of anaesthesiologists when providing interpretable hypoxemia risks and contributing factors. The explanations for the predictions are broadly consistent with the literature and with prior knowledge from anaesthesiologists. Our results suggest that if anaesthesiologists currently anticipate 15% of hypoxemia events, with this system's assistance they would anticipate 30% of them, a large portion of which may benefit from early intervention because they are associated with modifiable factors. The system can help improve the clinical understanding of hypoxemia risk during anaesthesia care by providing general insights into the exact changes in risk induced by certain patient or procedure characteristics.
Topics: Adult; Aged; Aged, 80 and over; Anesthesia, General; Anesthesiologists; Area Under Curve; Electronic Health Records; Female; Humans; Hypoxia; Machine Learning; Male; Middle Aged; ROC Curve; Risk Factors; Surgical Procedures, Operative
PubMed: 31001455
DOI: 10.1038/s41551-018-0304-0 -
American Journal of Physiology.... Nov 2014Intermittent hypoxia (IH) has been the subject of considerable research in recent years, and triggers a bewildering array of both detrimental and beneficial effects in... (Review)
Review
Intermittent hypoxia (IH) has been the subject of considerable research in recent years, and triggers a bewildering array of both detrimental and beneficial effects in multiple physiological systems. Here, we review the extensive literature concerning IH and its impact on the respiratory, cardiovascular, immune, metabolic, bone, and nervous systems. One major goal is to define relevant IH characteristics leading to safe, protective, and/or therapeutic effects vs. pathogenesis. To understand the impact of IH, it is essential to define critical characteristics of the IH protocol under investigation, including potentially the severity of hypoxia within episodes, the duration of hypoxic episodes, the number of hypoxic episodes per day, the pattern of presentation across time (e.g., within vs. consecutive vs. alternating days), and the cumulative time of exposure. Not surprisingly, severe/chronic IH protocols tend to be pathogenic, whereas any beneficial effects are more likely to arise from modest/acute IH exposures. Features of the IH protocol most highly associated with beneficial vs. pathogenic outcomes include the level of hypoxemia within episodes and the number of episodes per day. Modest hypoxia (9-16% inspired O2) and low cycle numbers (3-15 episodes per day) most often lead to beneficial effects without pathology, whereas severe hypoxia (2-8% inspired O2) and more episodes per day (48-2,400 episodes/day) elicit progressively greater pathology. Accumulating evidence suggests that "low dose" IH (modest hypoxia, few episodes) may be a simple, safe, and effective treatment with considerable therapeutic potential for multiple clinical disorders.
Topics: Animals; Bone and Bones; Cardiovascular System; Humans; Hypoxia; Inflammation; Nervous System; Oxygen; Respiratory System; Time Factors
PubMed: 25231353
DOI: 10.1152/ajpregu.00208.2014 -
The Cochrane Database of Systematic... Nov 2015Acute hypoxaemia de novo or on a background of chronic hypoxaemia is a common reason for admission to intensive care and for provision of mechanical ventilation. Various... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Acute hypoxaemia de novo or on a background of chronic hypoxaemia is a common reason for admission to intensive care and for provision of mechanical ventilation. Various refinements of mechanical ventilation or adjuncts are employed to improve patient outcomes. Mortality from acute respiratory distress syndrome, one of the main contributors to the need for mechanical ventilation for hypoxaemia, remains approximately 40%. Ventilation in the prone position may improve lung mechanics and gas exchange and could improve outcomes.
OBJECTIVES
The objectives of this review are (1) to ascertain whether prone ventilation offers a mortality advantage when compared with traditional supine or semi recumbent ventilation in patients with severe acute respiratory failure requiring conventional invasive artificial ventilation, and (2) to supplement previous systematic reviews on prone ventilation for hypoxaemic respiratory failure in an adult population.
SEARCH METHODS
We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 1), Ovid MEDLINE (1950 to 31 January 2014), EMBASE (1980 to 31 January 2014), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (1982 to 31 January 2014) and Latin American Caribbean Health Sciences Literature (LILACS) (1992 to 31 January 2014) in Ovid MEDLINE for eligible randomized controlled trials. We also searched for studies by handsearching reference lists of relevant articles, by contacting colleagues and by handsearching published proceedings of relevant journals. We applied no language constraints, and we reran the searches in CENTRAL, MEDLINE, EMBASE, CINAHL and LILACS in June 2015. We added five new studies of potential interest to the list of "Studies awaiting classification" and will incorporate them into formal review findings during the review update.
SELECTION CRITERIA
We included randomized controlled trials (RCTs) that examined the effects of prone position versus supine/semi recumbent position during conventional mechanical ventilation in adult participants with acute hypoxaemia.
DATA COLLECTION AND ANALYSIS
Two review authors independently reviewed all trials identified by the search and assessed them for suitability, methods and quality. Two review authors extracted data, and three review authors reviewed the data extracted. We analysed data using Review Manager software and pooled included studies to determine the risk ratio (RR) for mortality and the risk ratio or mean difference (MD) for secondary outcomes; we also performed subgroup analyses and sensitivity analyses.
MAIN RESULTS
We identified nine relevant RCTs, which enrolled a total of 2165 participants (10 publications). All recruited participants suffered from disorders of lung function causing moderate to severe hypoxaemia and requiring mechanical ventilation, so they were fairly comparable, given the heterogeneity of specific disease diagnoses in intensive care. Risk of bias, although acceptable in the view of the review authors, was inevitable: Blinding of participants and carers to treatment allocation was not possible (face-up vs face-down).Primary analyses of short- and longer-term mortality pooled from six trials demonstrated an RR of 0.84 to 0.86 in favour of the prone position (PP), but findings were not statistically significant: In the short term, mortality for those ventilated prone was 33.4% (363/1086) and supine 38.3% (395/1031). This resulted in an RR of 0.84 (95% confidence interval (CI) 0.69 to 1.02) marginally in favour of PP. For longer-term mortality, results showed 41.7% (462/1107) for prone and 47.1% (490/1041) for supine positions, with an RR of 0.86 (95% CI 0.72 to 1.03). The quality of the evidence for both outcomes was rated as low as a result of important potential bias and serious inconsistency.Subgroup analyses for mortality identified three groups consistently favouring PP: those recruited within 48 hours of meeting entry criteria (five trials; 1024 participants showed an RR of 0.75 (95% CI 0.59 to 94)); those treated in the PP for 16 or more hours per day (five trials; 1005 participants showed an RR of 0.77 (95% CI 0.61 to 0.99)); and participants with more severe hypoxaemia at trial entry (six trials; 1108 participants showed an RR of 0.77 (95% CI 0.65 to 0.92)). The quality of the evidence for these outcomes was rated as moderate as a result of potentially important bias.Prone positioning appeared to influence adverse effects: Pressure sores (three trials; 366 participants) with an RR of 1.37 (95% CI 1.05 to 1.79) and tracheal tube obstruction with an RR of 1.78 (95% CI 1.22 to 2.60) were increased with prone ventilation. Reporting of arrhythmias was reduced with PP, with an RR of 0.64 (95% CI 0.47 to 0.87).
AUTHORS' CONCLUSIONS
We found no convincing evidence of benefit nor harm from universal application of PP in adults with hypoxaemia mechanically ventilated in intensive care units (ICUs). Three subgroups (early implementation of PP, prolonged adoption of PP and severe hypoxaemia at study entry) suggested that prone positioning may confer a statistically significant mortality advantage. Additional adequately powered studies would be required to confirm or refute these possibilities of subgroup benefit but are unlikely, given results of the most recent study and recommendations derived from several published subgroup analyses. Meta-analysis of individual patient data could be useful for further data exploration in this regard. Complications such as tracheal obstruction are increased with use of prone ventilation. Long-term mortality data (12 months and beyond), as well as functional, neuro-psychological and quality of life data, are required if future studies are to better inform the role of PP in the management of hypoxaemic respiratory failure in the ICU.
Topics: Acute Disease; Adult; Humans; Hypoxia; Middle Aged; Patient Positioning; Prone Position; Randomized Controlled Trials as Topic; Respiration, Artificial; Respiratory Distress Syndrome; Respiratory Insufficiency
PubMed: 26561745
DOI: 10.1002/14651858.CD008095.pub2 -
Ugeskrift For Laeger Nov 2022Oxygen is a standard treatment for patients with chronic lung diseases and hypoxemia. The two main groups of lung diseases leading to oxygen treatment is chronic... (Review)
Review
Oxygen is a standard treatment for patients with chronic lung diseases and hypoxemia. The two main groups of lung diseases leading to oxygen treatment is chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD). Several guidelines for home oxygen therapy for patients with ILD is, however, based on older observation and extrapolations from studies on COPD. This review focuses on the different oxygen treatment modalities for patients with ILD focusing on present evidence and upcoming trials that might change the oxygen therapy approach for patients with ILD.
Topics: Humans; Oxygen Inhalation Therapy; Lung Diseases, Interstitial; Pulmonary Disease, Chronic Obstructive; Oxygen; Hypoxia
PubMed: 36426814
DOI: No ID Found -
BMC Pulmonary Medicine May 2021To investigate the indications for high-flow nasal cannula oxygen (HFNC) therapy in patients with hypoxemia during ventilator weaning and to explore the predictors of...
BACKGROUND
To investigate the indications for high-flow nasal cannula oxygen (HFNC) therapy in patients with hypoxemia during ventilator weaning and to explore the predictors of reintubation when treatment fails.
METHODS
Adult patients with hypoxemia weaning from mechanical ventilation were identified from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The patients were assigned to the treatment group or control group according to whether they were receiving HFNC or non-invasive ventilation (NIV) after extubation. The 28-day mortality and 28-day reintubation rates were compared between the two groups after Propensity score matching (PSM). The predictor for reintubation was formulated according to the risk factors with the XGBoost algorithm. The areas under the receiver operating characteristic curve (AUC) was calculated for reintubation prediction according to values at 4 h after extubation, which was compared with the ratio of SpO/FiO to respiratory rate (ROX index).
RESULTS
A total of 524,520 medical records were screened, and 801 patients with moderate or severe hypoxemia when undergoing mechanical ventilation weaning were included (100 < PaO2/FiO2 ≤ 300 mmHg), including 358 patients who received HFNC therapy after extubation in the treatment group. There were 315 patients with severe hypoxemia (100 < PaO2/FiO2 ≤ 200 mmHg) before extubation, and 190 patients remained in the treatment group with median oxygenation index 166[157,180] mmHg after PSM. There were no significant differences in the 28-day reintubation rate or 28-day mortality between the two groups with moderate or severe hypoxemia (all P > 0.05). Then HR/SpO was formulated as a predictor for 48-h reintubation according to the important features predicting weaning failure. According to values at 4 h after extubation, the AUC of HR/SpO was 0.657, which was larger than that of ROX index (0.583). When the HR/SpO reached 1.2 at 4 h after extubation, the specificity for 48-h reintubation prediction was 93%.
CONCLUSIONS
The treatment effect of HFNC therapy is not inferior to that of NIV, even on patients with oxygenation index from 160 to 180 mmHg when weaning from ventilator. HR/SpO is more early and accurate in predicting HFNC failure than ROX index.
Topics: Aged; Cannula; Critical Care; Databases, Factual; Female; Humans; Hypoxia; Male; Middle Aged; Noninvasive Ventilation; Oxygen; Oxygen Inhalation Therapy; Respiratory Insufficiency; Retrospective Studies; Time Factors
PubMed: 33985472
DOI: 10.1186/s12890-021-01526-2 -
Chest Oct 2022Mortality historically has been the primary outcome of choice for acute and critical care clinical trials. However, undue reliance on mortality can limit the scope of... (Review)
Review
Mortality historically has been the primary outcome of choice for acute and critical care clinical trials. However, undue reliance on mortality can limit the scope of trials that can be performed. Large sample sizes are usually needed for trials powered for a mortality outcome, and focusing solely on mortality fails to recognize the importance that reducing morbidity can have on patients' lives. The COVID-19 pandemic has highlighted the need for rapid, efficient trials to rigorously evaluate new therapies for hospitalized patients with acute lung injury. Oxygen-free days (OFDs) is a novel outcome for clinical trials that is a composite of mortality and duration of new supplemental oxygen use. It is designed to characterize recovery from acute lung injury in populations with a high prevalence of new hypoxemia and supplemental oxygen use. In these populations, OFDs captures two patient-centered consequences of acute lung injury: mortality and hypoxemic lung dysfunction. Power to detect differences in OFDs typically is greater than that for other clinical trial outcomes, such as mortality and ventilator-free days. OFDs is the primary outcome for the Fourth Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV-4) Host Tissue platform, which evaluates novel therapies targeting the host response to COVID-19 among adults hospitalized with COVID-19 and new hypoxemia. This article outlines the rationale for use of OFDs as an outcome for clinical trials, proposes a standardized method for defining and analyzing OFDs, and provides a framework for sample size calculations using the OFD outcome.
Topics: Acute Lung Injury; Adult; COVID-19; Clinical Trials as Topic; Humans; Hypoxia; Outcome Assessment, Health Care; Oxygen; Pandemics
PubMed: 35504307
DOI: 10.1016/j.chest.2022.04.145 -
Ugeskrift For Laeger Dec 2023Home oxygen therapy is an acknowledged treatment for patients suffering from chronic hypoxaemia, due to pulmonary or cardiac disease, and may have positive effects on... (Review)
Review
Home oxygen therapy is an acknowledged treatment for patients suffering from chronic hypoxaemia, due to pulmonary or cardiac disease, and may have positive effects on survival and quality of life. The risks and side effects of the treatment are usually mild, and the equipment has developed to become relatively affordable, accessible and easy to transport. Adjustments in the oxygen settings can be necessary when travelling by airplane or during physical effort or sleep. Prescription and follow-ups are usually best maintained by hospital departments with expertise in pulmonary medicine, as argued in this review.
Topics: Humans; Quality of Life; Oxygen Inhalation Therapy; Lung; Oxygen; Denmark; Hypoxia
PubMed: 38078470
DOI: No ID Found