A meta-analysis of the effects of transnasal high-flow oxygen therapy in gastrointestinal endoscopy.

Purpose: This study aimed to systematically evaluate the clinical effects of using transnasal high-flow nasal cannula (HFNC) and conventional oxygen therapy (COT) in patients undergoing gastrointestinal endoscopy. Methods: A comprehensive literature search was conducted from 2004 to April 2024 to collect relevant studies on the application of HFNC in patients undergoing gastrointestinal endoscopy. Multiple Chinese and English databases, including China National Knowledge Infrastructure (CNKI), Wanfang Data, Web of Science, PubMed, and Cochrane Library, were searched systematically for randomized controlled trials (RCTs). Two researchers independently screened the literature, extracted data, and assessed the risk of bias in the included studies. RevMan 5.4 software was utilized for conducting the network meta-analysis. Results: A total of 12 RCTs involving 3,726 patients were included. Meta-analysis results showed that HFNC reduced the incidence of hypoxemia and improved the minimum oxygen saturation (SpO2) compared with COT [odds ratio (OR) = 0.39, 95% confidence interval (CI): 0.29-0.53], [mean difference (MD) = 4.07, 95% CI: 3.14-5.01], and the difference was statistically significant. However, the baseline SpO2 levels and incidence of hypercapnia were not statistically significantly different between the HFNC and COT groups [MD = -0.21, 95% CI: -0.49-0.07]; [OR = 1.43, 95% CI: 0.95-2.15]. In terms of procedure time, the difference between HFNC and COT was not statistically significant, and subgroup analyses were performed for the different types of studies, with standard deviation in the gastroscopy group (MD = 0.09, 95% CI: -0.07-0.24) and the endoscopic retrograde cholangiopancreatography group (MD = 0.36, 95% CI: -0.50-1.23). The results demonstrated a significant reduction in the adoption of airway interventions in the HFNC group compared to the COT group (OR = 0.16, 95% CI: 0.05-0.53), with a statistically significant difference; this result was consistent with those of the included studies. Conclusion: The application of HFNC improves the incidence of hypoxemia, enhances oxygenation, and reduces airway interventions during gastrointestinal endoscopy. However, HFNC does not significantly affect baseline SpO2, hypercapnia, or procedure time. The limitations of this study must be acknowledged, and further high-quality studies should be conducted to validate these findings.

The benefits and drawbacks of home oxygen therapy for COPD: what's next?

INTRODUCTION: Home oxygen therapy is one of the few interventions that can improve survival in patients with chronic obstructive pulmonary disease (COPD) when administered appropriately, although it may cause side effects and be an unnecessary burden for some patients. AREAS COVERED: This narrative review summarizes the current literature on the assessment of hypoxemia, different types of home oxygen therapy, potential beneficial and adverse effects, and emerging research on home oxygen therapy in COPD. A literature search was performed using MEDLINE and EMBASE up to January 2024, with additional articles being identified through clinical guidelines. EXPERT OPINION: Hypoxemia is common in patients with more severe COPD. Long-term oxygen therapy is established to prolong survival in patients with chronic severe resting hypoxemia. Conversely, in the absence of chronic severe resting hypoxemia, home oxygen therapy has an unclear or conflicting evidence base, including for palliation of breathlessness, and is generally not recommended. However, beneficial effects in some patients cannot be precluded. Evidence is emerging on the optimal daily duration of oxygen use, the role of high-flow and auto-titrated oxygen therapy, improved informed decision-making, and telemonitoring. Further research is needed to validate novel oxygen delivery systems and monitoring tools and establish long-term effects of ambulatory oxygen therapy in COPD.

Duration-Dependent Risk of Hypoxemia in Colonoscopy Procedures.

Background and Aims: Colonoscopy is a critical diagnostic and therapeutic procedure in gastroenterology. However, it carries risks, including hypoxemia, which can impact patient safety. Understanding the factors that contribute to the incidence of severe hypoxemia, specifically the role of procedure duration, is essential for improving patient outcomes. This study aims to elucidate the relationship between the length of colonoscopy procedures and the occurrence of severe hypoxemia. Methods: We conducted a retrospective cohort study at Sheba Medical Center, Israel, including 21,524 adult patients who underwent colonoscopy from January 2020 to January 2024. The study focused on the incidence of severe hypoxemia, defined as a drop in oxygen saturation below 90%. Sedation protocols, involving a combination of Fentanyl, Midazolam, and Propofol were personalized based on the endoscopist's discretion. Data were collected from electronic health records, covering patient demographics, clinical scores, sedation and procedure details, and outcomes. Statistical analyses, including logistic regression, were used to examine the association between procedure duration and hypoxemia, adjusting for various patient and procedural factors. Results: We initially collected records of 26,569 patients who underwent colonoscopy, excluding 5045 due to incomplete data, resulting in a final cohort of 21,524 patients. Procedures under 20 min comprised 48.9% of the total, while those lasting 20-40 min made up 50.7%. Only 8.5% lasted 40-60 min, and 2.9% exceeded 60 min. Longer procedures correlated with higher hypoxemia risk: 17.3% for <20 min, 24.2% for 20-40 min, 32.4% for 40-60 min, and 36.1% for ≥60 min. Patients aged 60-80 and ≥80 had increased hypoxemia odds (aOR 1.1, 95% CI 1.0-1.2 and aOR 1.2, 95% CI 1.0-1.4, respectively). Procedure durations of 20-40 min, 40-60 min, and over 60 min had aORs of 1.5 (95% CI 1.4-1.6), 2.1 (95% CI 1.9-2.4), and 2.4 (95% CI 2.0-3.0), respectively. Conclusions: The duration of colonoscopy procedures significantly impacts the risk of severe hypoxemia, with longer durations associated with higher risks. This study underscores the importance of optimizing procedural efficiency and tailoring sedation protocols to individual patient risk profiles to enhance the safety of colonoscopy. Further research is needed to develop strategies that minimize procedure duration without compromising the quality of care, thereby reducing the risk of hypoxemia and improving patient safety.

Evaluation of wakefulness electroencephalogram in OSA patients.

OBJECTIVE: Obstructive sleep apnea (OSA) has been associated with an elevated cardiovascular risk, increased daytime sleepiness, cognitive decline, and slower electroencephalographic activity (EEG). This study assesses EEG patterns during wakefulness in OSA patients compared to those without sleep-disordered breathing. MATERIALS AND METHODS: This retrospective study analyzed 30 OSA patients with an Apnea/Hypopnea Index (AHI) of 15 or higher, as well as 29 individuals without sleep-disordered breathing (AHI of 5 or lower) who underwent hospital polysomnography and met all inclusion criteria. Sociodemographic and EEG data were obtained from the sleep laboratory database. Blinded EEG analysis was conducted by two observers, assessing activity in the frontal, central, and occipital regions. RESULTS: No significant differences were observed in EEG activity between OSA and non-OSA patients. However, a weak correlation was found between decreased C3 EEG frequency and higher AHI (p = 0.033), as well as increased total sleep time and higher O2 EEG frequency (p = 0.038). Lower amplitudes in C3 (p = 0.043) and O1 (p = 0.031) were correlated with reduced average oxygen saturation. CONCLUSION: Our findings suggest that OSA-related hypoxemia may impact neuronal activity, highlighting the need to address this sleep-disordered breathing in order to potentially prevent the cognitive decline observed in OSA patients.

Racial and Ethnic Disparities in Occult Hypoxemia Prevalence and Clinical Outcomes Among Hospitalized Patients: A Systematic Review and Meta-analysis.

BACKGROUND: There is growing concern that pulse oximeters are routinely less accurate in hospitalized patients with darker skin pigmentation, in turn increasing risk of undetected (occult) hypoxemia and adverse clinical outcomes. The aim of this systematic review and meta-analysis was to synthesize evidence on racial and ethnic disparities in occult hypoxemia prevalence and clinical impacts of undetected hypoxemia. METHODS: Ovid MEDLINE, Embase, and CINAHL databases were searched for relevant articles published through January 2024. Eligible studies must have been conducted among adults in inpatient or outpatient settings and report occult hypoxemia prevalence stratified by patient race or ethnicity, or clinical outcomes stratified by patient race or ethnicity and occult hypoxemia status. Screening for inclusion was conducted independently by two investigators. Data extraction and risk of bias assessment were conducted by one investigator then checked by a second. Outcome data were synthesized using random-effects meta-analyses. RESULTS: Fifteen primary studies met eligibility criteria and reported occult hypoxemia prevalence in 732,505 paired oximetry measurements from 207,464 hospitalized patients. Compared with White patients, occult hypoxemia is likely more common among Black patients (pooled prevalence ratio = 1.67, 95% CI 1.47 to 1.90) and among patients identifying as Asian, Latinx, Indigenous, multiracial, or other race or ethnicity (pooled prevalence ratio = 1.39, 95% CI 1.19 to 1.64). Findings from studies reporting clinical outcomes suggest that Black patients with undetected hypoxemia may experience poorer treatment delivery outcomes than White patients with undetected hypoxemia. No evidence was found from outpatient settings. DISCUSSION: This review and included primary studies rely on self-identified race or ethnicity, which may obscure variability in occult hypoxemia risk. Findings underscore that clinicians should be aware of the risk of occult hypoxemia in hospitalized patients with darker skin pigmentation. Moreover, oximetry data from included studies suggests that the accuracy of pulse oximeters could vary substantially from patient to patient and even within individual patients. TRIAL REGISTRATION: PROSPERO ( CRD42023402152 ).

Beyond the Rib Cage: Unraveling Abernethy Syndrome as a Rare Cause of Cyanosis.

Abernethy syndrome is a rare congenital malformation stemming from a portosystemic shunt. Diagnosis proves challenging due to nonspecific clinical symptoms, with presentation varying based on age and disease severity. Consequences include hepatic, cardiovascular, renal, gastrointestinal, and neurological complications, and growth retardation. We report the case of a child presenting with perioral and digital cyanosis, observed in early childhood. Clinical examination revealed low saturation, telangiectasias, digital clubbing, and collateral venous circulation in the thorax. Imaging confirmed the diagnosis of Abernethy syndrome.

High flow oxygen therapy versus conventional oxygen therapy in dogs and cats undergoing bronchoscopy and bronchoalveolar lavage: a pilot study.

Objectives: To evaluate the safety and feasibility of high flow oxygen therapy (HFOT), and to record SpO2 and desaturation episodes in dogs and cats receiving HFOT or conventional oxygen therapy (COT) during bronchoscopy ± bronchoalveolar lavage (BAL). Materials and methods: Dogs and cats undergoing bronchoscopy ± BAL between January and May 2023 were included in the study. Patients were randomly allocated to two groups: HFOT (HFOT group; two cats and four dogs) and COT (COT group; one cat and five dogs). HFOT and COT were started at the beginning of the bronchoscopy. HFOT was delivered with a gas flow rate of 1 L/kg/min at an FiO2 of 100% and a temperature of 34°C (pediatric mode) or 37°C (adult mode). COT was delivered through the working channel of the bronchoscope at a rate of 1.5 L/min. The safety and feasibility of HFOT were assessed, and peripheral oxygen saturation (SpO2) was measured by pulse oximetry every 30 s throughout the procedure. Measurements and main results: HFOT was feasible and safe in both dogs and cats with no complications reported. While there was no significant difference in the number of desaturation episodes (SpO2 < 94%) between the two groups, none of the patients in the HFOT group experienced severe desaturation (SpO2 < 90%). In contrast, two patients in the COT group had an SpO2 < 90%. Mean SpO2 was significantly higher in the HFOT group compared to the COT group at T0 (98% ± 2% vs. 94 ± 2%), T0.5 (98% ± 2% vs. 94% ± 3%) and T1 (98% ± 2% vs. 94% ± 4%). Conclusion: To the authors' knowledge, this is the largest study conducted to date using HFOT during bronchoscopy in dogs and cats. Our results suggest that HFOT is feasible and safe during bronchoscopy ± BAL. Furthermore, HFOT may reduce the risk of desaturation episodes in dogs and cats undergoing bronchoscopy and BAL.

Rapid pulmonary fistulization complicating a psoas abscess with intraoperative hypoxemia: a rare case report.

Introduction and importance: Psoas abscess is a relatively uncommon condition that can present with vague clinical features. Patients with this condition often present in different ways to different specialties leading to delays in diagnosis and management. Case presentation: The authors present a 47-year-old woman with complaint of vague abdominal pain, fever, and raised inflammatory markers who underwent CT examination. On CT, a collection was noted in the right iliac fossa that extended along the right retroperitoneum through the retrocrural space in the right lung base communicating with a cavitary pulmonary lesion with air-fluid level. The psoas abscess was drained. Clinical discussion: Our case presents a number of rare and intriguing features. Notably, the patient, who was immunocompetent, experienced a primary Staphylococcus infection that swiftly progressed to a sizable pulmonary abscess, a phenomenon uncommon in such hosts. The rarity further extends to the source of infection, originating abdominally but culminating in thoracic complications through contiguous spread from a retroperitoneal site. Despite the potential severity, the patient's outcome was remarkably positive. Conclusion: This case underscores the potential rapidity of pulmonary involvement in psoas abscesses, emphasizing the need for heightened awareness and consideration of respiratory signs during preoperative assessments.

Basing intubation of acutely hypoxemic patients on physiologic principles.

The decision to intubate a patient with acute hypoxemic respiratory failure who is not in apparent respiratory distress is one of the most difficult clinical decisions faced by intensivists. A conservative approach exposes patients to the dangers of hypoxemia, while a liberal approach exposes them to the dangers of inserting an endotracheal tube and invasive mechanical ventilation. To assist intensivists in this decision, investigators have used various thresholds of peripheral or arterial oxygen saturation, partial pressure of oxygen, partial pressure of oxygen-to-fraction of inspired oxygen ratio, and arterial oxygen content. In this review we will discuss how each of these oxygenation indices provides inaccurate information about the volume of oxygen transported in the arterial blood (convective oxygen delivery) or the pressure gradient driving oxygen from the capillaries to the cells (diffusive oxygen delivery). The decision to intubate hypoxemic patients is further complicated by our nescience of the critical point below which global and cerebral oxygen supply become delivery-dependent in the individual patient. Accordingly, intubation requires a nuanced understanding of oxygenation indexes. In this review, we will also discuss our approach to intubation based on clinical observations and physiologic principles. Specifically, we consider intubation when hypoxemic patients, who are neither in apparent respiratory distress nor in shock, become cognitively impaired suggesting emergent cerebral hypoxia. When deciding to intubate, we also consider additional factors including estimates of cardiac function, peripheral perfusion, arterial oxygen content and its determinants. It is not possible, however, to pick an oxygenation breakpoint below which the benefits of mechanical ventilation decidedly outweigh its hazards. It is futile to imagine that decision making about instituting mechanical ventilation in an individual patient can be condensed into an algorithm with absolute numbers at each nodal point. In sum, an algorithm cannot replace the presence of a physician well skilled in the art of clinical evaluation who has a deep understanding of pathophysiologic principles.

Treating sleep-disordered breathing of idiopathic pulmonary fibrosis patients with CPAP and nocturnal oxygen treatment. A pilot study : Sleep-disordered breathing treatment in IPF.

INTRODUCTION: Sleep-disordered breathing (SDB) is a major comorbidity in idiopathic pulmonary fibrosis (IPF) and is associated with a poor outcome. There is a lack of knowledge regarding the impact of SDB treatment on IPF. We assessed at one year: (1) the effect of CPAP and/or nocturnal oxygen therapy on IPF regarding lung function, blood mediators, and quality of life; (2) adherence to SDB treatment and SDB changes. METHODOLOGY: This is a prospective study of consecutive newly diagnosed IPF patients initiating anti-fibrotic treatment. Lung function, polysomnography, blood tests and quality of life questionnaires were performed at inclusion and after one year. Patients were classified as obstructive sleep apnoea (OSA), central sleep apnoea (CSA), and sleep-sustained hypoxemia (SSH). SDB therapy (CPAP and/or nocturnal oxygen therapy) was initiated if needed. RESULTS: Fifty patients were enrolled (36% had OSA, 22% CSA, and 12% SSH). CPAP was started in 54% of patients and nocturnal oxygen therapy in 16%. At one-year, polysomnography found improved parameters, though 17% of patients had to add nocturnal oxygen therapy or CPAP, while 33% presented SDB onset at this second polysomnography. CPAP compliance at one year was 6.74 h/night (SD 0.74). After one year, matrix metalloproteinase-1 decreased in OSA and CSA (p = 0.029; p = 0.027), C-reactive protein in OSA (p = 0.045), and surfactant protein D in CSA group (p = 0.074). There was no significant change in lung function. CONCLUSIONS: Treatment of SBD with CPAP and NOT can be well tolerated with a high compliance. IPF patients may exhibit SDB progression and require periodic re-assessment. Further studies to evaluate the impact of SDB treatment on lung function and serological mediators are needed.

Performance of a Wearable Ring in Controlled Hypoxia: A Prospective Observational Study.

BACKGROUND: Over recent years, technological advances in wearables have allowed for continuous home monitoring of heart rate and oxygen saturation. These devices have primarily been used for sports and general wellness and may not be suitable for medical decision-making, especially in saturations below 90% and in patients with dark skin color. Wearable clinical-grade saturation of peripheral oxygen (SpO2) monitoring can be of great value to patients with chronic diseases, enabling them and their clinicians to better manage their condition with reliable real-time and trend data. OBJECTIVE: This study aimed to determine the SpO2 accuracy of a wearable ring pulse oximeter compared with arterial oxygen saturation (SaO2) in a controlled hypoxia study based on the International Organization for Standardization (ISO) 80601-2-61:2019 standard over the range of 70%-100% SaO2 in volunteers with a broad range of skin color (Fitzpatrick I to VI) during nonmotion conditions. In parallel, accuracy was compared with a calibrated clinical-grade reference pulse oximeter (Masimo Radical-7). Acceptable medical device accuracy was defined as a maximum of 4% root mean square error (RMSE) per the ISO 80601-2-61 standard and a maximum of 3.5% RMSE per the US Food and Drug Administration guidance. METHODS: We performed a single-center, blinded hypoxia study of the test device in 11 healthy volunteers at the Hypoxia Research Laboratory, University of California at San Francisco, under the direction of Philip Bickler, MD, PhD, and John Feiner, MD. Each volunteer was connected to a breathing apparatus for the administration of a hypoxic gas mixture. To facilitate frequent blood gas sampling, a radial arterial cannula was placed on either wrist of each participant. One test device was placed on the index finger and another test device was placed on the fingertip. SaO2 analysis was performed using an ABL-90 multi-wavelength oximeter. RESULTS: For the 11 participants included in the analysis, there were 236, 258, and 313 SaO2-SpO2 data pairs for the test device placed on the finger, the test device placed on the fingertip, and the reference device, respectively. The RMSE of the test device for all participants was 2.1% for either finger or fingertip placement, while the Masimo Radical-7 reference pulse oximeter RMSE was 2.8%, exceeding the standard (4% or less) and the Food and Drug Administration guidance (3.5% or less). Accuracy of SaO2-SpO2 paired data from the 4 participants with dark skin in the study was separately analyzed for both test device placements and the reference device. The test and reference devices exceeded the minimum accuracy requirements for a medical device with RMSE at 1.8% (finger) and 1.6% (fingertip) and for the reference device at 2.9%. CONCLUSIONS: The wearable ring meets an acceptable standard of accuracy for clinical-grade SpO2 under nonmotion conditions without regard to skin color. TRIAL REGISTRATION: ClinicalTrials.gov NCT05920278; https://clinicaltrials.gov/study/NCT05920278.

Evaluation of a Rebreathing System for Use with Portable Mechanical Ventilators.

INTRODUCTION: Maximizing the capabilities of available lowflow oxygen is key to providing adequate oxygen to prevent/treat hypoxemia and conserve oxygen. We designed a closed-circuit system that allows rebreathing of gases while scrubbing carbon dioxide (CO2) in conjunction with portable mechanical ventilators in a bench model. METHODS: We evaluated the system using two portable mechanical ventilators currently deployed by the Department of Defense-Zoll 731 and AutoMedx SAVe II-over a range of ventilator settings and lung models, using 1 and 3L/min low-flow oxygen into a reservoir bag. We measured peak inspired oxygen concentration (FiO2), CO2-absorbent life, gas temperature and humidity, and the effect of airway suctioning and ventilator disconnection on FiO2 on ground and at altitude. RESULTS: FiO2 was =0.9 across all ventilator settings and altitudes using both oxygen flows. CO2-absorbent life was >7 hours. Airway humidity range was 87%-97%. Mean airway temperature was 25.4°C (SD 0.5°C). Ten-second suctioning reduced FiO2 22%-48%. Thirtysecond ventilator disconnect reduced FiO2 29%-63% depending on oxygen flow used. CONCLUSION: Use of a rebreathing system with mechanical ventilation has the potential for oxygen conservation but requires diligent monitoring of inspired FiO2 and CO2 to avoid negative consequences.

Characterizing the Racial Discrepancy in Hypoxemia Detection in Venovenous Extracorporeal Membrane Oxygenation: An Extracorporeal Life Support Organization Registry Analysis.

PURPOSE: Skin pigmentation influences peripheral oxygen saturation (SpO2) compared to arterial saturation of oxygen (SaO2). Occult hypoxemia (SaO2 ≤ 88% with SpO2 ≥ 92%) is associated with increased in-hospital mortality in venovenous-extracorporeal membrane oxygenation (VV-ECMO) patients. We hypothesized VV-ECMO cannulation, in addition to race/ethnicity, accentuates the SpO2-SaO2 discrepancy due to significant hemolysis. METHODS: Adults (≥ 18 years) supported with VV-ECMO with concurrently measured SpO2 and SaO2 measurements from over 500 centers in the Extracorporeal Life Support Organization Registry (1/2018-5/2023) were included. Multivariable logistic regressions were performed to examine whether race/ethnicity was associated with occult hypoxemia in pre-ECMO and on-ECMO SpO2-SaO2 calculations. RESULTS: Of 13,171 VV-ECMO patients, there were 7772 (59%) White, 2114 (16%) Hispanic, 1777 (14%) Black, and 1508 (11%) Asian patients. The frequency of on-ECMO occult hypoxemia was 2.0% (N = 233). Occult hypoxemia was more common in Black and Hispanic patients versus White patients (3.1% versus 1.7%, P < 0.001 and 2.5% versus 1.7%, P = 0.025, respectively). In multivariable logistic regression, Black patients were at higher risk of pre-ECMO occult hypoxemia versus White patients (adjusted odds ratio [aOR] = 1.55, 95% confidence interval [CI] = 1.18-2.02, P = 0.001). For on-ECMO occult hypoxemia, Black patients (aOR = 1.79, 95% CI = 1.16-2.75, P = 0.008) and Hispanic patients (aOR = 1.71, 95% CI = 1.15-2.55, P = 0.008) had higher risk versus White patients. Higher pump flow rates (aOR = 1.29, 95% CI = 1.08-1.55, P = 0.005) and on-ECMO 24-h lactate (aOR = 1.06, 95% CI = 1.03-1.10, P < 0.001) significantly increased the risk of on-ECMO occult hypoxemia. CONCLUSION: SaO2 should be carefully monitored if using SpO2 during ECMO support for Black and Hispanic patients especially for those with high pump flow and lactate values at risk for occult hypoxemia.

Hypoxemia and its clinical predictors among children with respiratory distress admitted to the University of Gondar Comprehensive Specialized Hospital, Northwest Ethiopia.

INTRODUCTION: Hypoxemia is a common complication of childhood respiratory tract infections and non-respiratory infections. Hypoxemic children have a five-fold increased risk of death compared to children without hypoxemia. In addition, there is limited evidence about hypoxemia and clinical predictors in Ethiopia. Therefore, this study was conducted to assess the prevalence and clinical predictors of hypoxemia among children with respiratory distress admitted to the University of Gondar Comprehensive Specialized Hospital. METHODS: An institutional-based cross-sectional study was conducted from December 2020 to May 2021 in northwest Ethiopia. A total of 399 study participants were selected using systematic random sampling. The oxygen saturation of the child was measured using Masimo rad-5 pulse oximetry. SPSS version 21 software was used for statistical analysis. RESULT: In this study, the prevalence of hypoxemia among children with respiratory distress was 63.5%. The clinical signs and symptoms significantly associated with hypoxemia were: head-nodding (AOR: 4.1, 95% CI: 1.81-9.28) and chest indrawing (AOR: 3.08, 95% CI: 1.32-7.16) which were considered statistically the risk factors for hypoxemia while inability to feed (AOR: 0.13, 95% CI: 0.02-0.77) was the protective factor for hypoxemia. The most sensitive predictors of hypoxemia were fast breathing with sensitivity (98.4%), nasal flaring (100.0%), chest indrawing (83.6%), and intercostal retraction (93.1%). The best specific predictors of hypoxemia were breathing difficulty with specificity (79.4%), inability to feed (100.0%), wheezing (83.0%), cyanosis (98.6%), impaired consciousness (94.2%), head-nodding (88.7%), and supra-sternal retraction (96.5%). CONCLUSION AND RECOMMENDATION: The prevalence of hypoxemia among children was high. The predictors of hypoxemia were the inability to feed, head nodding, and chest indrawing. It is recommended that the health care settings provide immediate care for the children with an inability to feed, head nodding, and chest indrawing. The policymakers better to focus on preventive strategies, particularly those with the most specific clinical predictors.

COVID-19 and silent hypoxemia in a minimal closed-loop model of the respiratory rhythm generator.

Silent hypoxemia, or "happy hypoxia," is a puzzling phenomenon in which patients who have contracted COVID-19 exhibit very low oxygen saturation ( SaO 2 < 80%) but do not experience discomfort in breathing. The mechanism by which this blunted response to hypoxia occurs is unknown. We have previously shown that a computational model of the respiratory neural network (Diekman et al. in J Neurophysiol 118(4):2194-2215, 2017) can be used to test hypotheses focused on changes in chemosensory inputs to the central pattern generator (CPG). We hypothesize that altered chemosensory function at the level of the carotid bodies and/or the nucleus tractus solitarii are responsible for the blunted response to hypoxia. Here, we use our model to explore this hypothesis by altering the properties of the gain function representing oxygen sensing inputs to the CPG. We then vary other parameters in the model and show that oxygen carrying capacity is the most salient factor for producing silent hypoxemia. We call for clinicians to measure hematocrit as a clinical index of altered physiology in response to COVID-19 infection.

Effects of moderate alcohol consumption and hypobaric hypoxia: implications for passengers' sleep, oxygen saturation and heart rate on long-haul flights.

BACKGROUND: Passengers on long-haul flights frequently consume alcohol. Inflight sleep exacerbates the fall in blood oxygen saturation (SpO2) caused by the decreased oxygen partial pressure in the cabin. We investigated the combined influence of alcohol and hypobaric hypoxia on sleep, SpO2 and heart rate. METHODS: Two groups of healthy individuals spent either two nights with a 4-hour sleep opportunity (00:00-04:00 hours) in the sleep laboratory (n=23; 53 m above sea level) or in the altitude chamber (n=17; 753 hPa corresponding to 2438 m above sea level, hypobaric condition). Participants consumed alcohol before one of the nights (mean±SE blood alcohol concentration 0.043±0.003%). The order of the nights was counterbalanced. Two 8-hour recovery nights (23:00-07:00 hours) were scheduled between conditions. Polysomnography, SpO2 and heart rate were recorded. RESULTS: The combined exposure to alcohol and hypobaric condition decreased SpO2 to a median (25th/75th percentile) of 85.32% (82.86/85.93) and increased heart rate to a median (25th/75th percentile) of 87.73 bpm (85.89/93.86) during sleep compared with 88.07% (86.50/88.49) and 72.90 bpm (70.90/78.17), respectively, in the non-alcohol hypobaric condition, 94.97% (94.59/95.33) and 76.97 bpm (65.17/79.52), respectively, in the alcohol condition and 95.88% (95.72/96.36) and 63.74 bpm (55.55/70.98), respectively, in the non-alcohol condition of the sleep laboratory group (all p<0.0001). Under the combined exposure SpO2 was 201.18 min (188.08/214.42) below the clinical hypoxia threshold of 90% SpO2 compared with 173.28 min (133.25/199.03) in the hypobaric condition and 0 min (0/0) in both sleep laboratory conditions. Deep sleep (N3) was reduced to 46.50 min (39.00/57.00) under the combined exposure compared with both sleep laboratory conditions (alcohol: 84.00 min (62.25/92.75); non-alcohol: 67.50 min (58.50/87.75); both p<0.003). CONCLUSIONS: The combination of alcohol and inflight hypobaric hypoxia reduced sleep quality, challenged the cardiovascular system and led to extended duration of hypoxaemia (SpO2 <90%).