Vascular impairments, including compromised flow regulation, have been identified as significant contributors to glaucomatous disease. Recent studies have shown glaucoma patients with significantly reduced peripapillary, macular, and optic nerve head vessel densities occurring with early glaucomatous structural changes prior to detectable visual field loss. This study aims to quantify the potential impact of decreased vessel densities on retinal perfusion and oxygen metabolism. In our clinical observations, pre-perimetric glaucoma patients exhibited a 10-13% reduction in vessel density compared to healthy individuals. Our theoretical model of the retinal vasculature is adapted in this study to assess the potential impact of this reduction in vessel density on retinal oxygenation. The model predicts a 1% and 38% decrease in mean oxygen saturation in retinal vessels immediately downstream of the capillaries when vessel density is decreased from its reference value by 10% and 50%, respectively. The impact of capillary loss on oxygen extraction fraction and the partial pressure of oxygen in retinal tissue is also predicted. Reductions in vessel density are simulated in combination with impaired flow regulation, and the resulting effects on saturation and flow are predicted. The model results showed a nonlinear relationship between vessel density and downstream saturation, indicating that larger decreases in the density of capillaries have a disproportionate impact on oxygenation. The model further demonstrates that the detrimental effects of minor vessel density reductions are exacerbated when combined with other vascular impairments.

How to cite this article: Mishra S, Kothari N, Sharma A, Goyal S. Author Response: Oxygen Delivery Devices in Postoperative Patients: Proper Selection of Patients Matters! Indian J Crit Care Med 2024;28(8):803.

OBJECTIVE: Professional boxing is a sport that requires a high aerobic capacity to prevent fatigue and allow athletes to perform over 4-12 rounds. Typically, athletes will go into a heavy training period in a pre-bout camp lasting 6 to 9 weeks. This study investigates the impact of 3 weeks of repeated Wingate sprint interval training, performed on standard gym ergometer bikes, on skeletal muscle endurance and mitochondrial function.
METHODS: Ten male professional boxers (age: 26 ± 4 years, height: 175 ± 5 cm, weight: 70 ± 5 kg) participated in the study. Baseline testing involved a NIRS monitor attached to the rectus femoris muscle prior to an incremental time to exhaustion test on a treadmill. After the treadmill test participants underwent a series of arterial occlusions to determine mitochondrial function post-volitional exhaustion. Participants then continued their own training for 3 weeks and then repeated baseline testing. After the second testing session, participants undertook three weekly sprint sessions consisting of 3 × 30 s maximal sprints with 60 s recovery. Testing was repeated 3 weeks later.
RESULTS: The time to exhaustion increased by > 6% after 3 weeks of sprint interval training as compared to baseline and control (p < 0.05). Skeletal muscle oxygen saturation (SmO2) at exhaustion was increased by 5.5% after 3 weeks of sprint interval training as compared to baseline and control (p = 0.008). Skeletal muscle mitochondrial rate post exhaustion was increased by 160% after 3 weeks of sprint interval training as compared to baseline and control (p < 0.001).
CONCLUSIONS: The study demonstrated that SIT led to increased incremental time to exhaustion, higher SmO2 levels at volitional exhaustion and increased mitochondrial rates in professional boxers. These findings suggest that SIT should be an integral part of a boxe\'s conditioning regimen to improve performance and safety within the ring.

Pulse oximetry (SpO2) is a critical monitor for assessing oxygenation status and guiding therapy in critically ill patients. Race has been identified as a potential source of SpO2 error, with consequent bias and inequities in healthcare. This study was designed to evaluate the incidence of occult hypoxemia and accuracy of pulse oximetry associated with the Massey-Martin scale and characterize the relationship between Massey scores and self-identified race. This retrospective single institute study utilized the Massey-Martin scale as a quantitative assessment of skin pigmentation. These values were recorded peri-operatively in patients enrolled in unrelated clinical trials. The electronic medical record was utilized to obtain demographics, arterial blood gas values, and time matched SpO2 values for each PaO2 ≤ 125 mmHg recorded throughout their hospitalizations. Differences between SaO2 and SpO2 were compared as a function of both Massey score and self-reported race. 4030 paired SaO2-SpO2 values were available from 579 patients. The average error (SaO2-SpO2) ± SD was 0.23 ± 2.6%. Statistically significant differences were observed within Massey scores and among races, with average errors that ranged from - 0.39 ± 2.3 to 0.53 ± 2.5 and - 0.55 ± 2.1 to 0.37 ± 2.7, respectively. Skin color varied widely within each self-identified race category. There was no clinically significant association between error rates and Massey-Martin scale grades and no clinically significant difference in accuracy observed between self-reported Black and White patients. In addition, self-reported race is not an appropriate surrogate for skin color.

Atrial-esophageal fistulas are rare and potentially fatal complications that can occur from radiofrequency ablation for the treatment of atrial fibrillation. Due to the proximity of the right atrium to the esophagus, thermal injuries can involuntarily lead to connections between the heart and esophagus. In this case study, a 67-year-old male developed an atrial-esophageal fistula following atrial fibrillation ablation. After discharge, the patient first presented with melena with a range of complications including aspiration, fever, atrial fibrillation, and neurological symptoms. The fistula was repaired promptly after diagnosis requiring meticulous planning by the anesthesia and surgical teams. The major consideration from anesthesiology was providing adequate oxygenation during one-lung ventilation via continuous positive airway pressure on the non-dependent lung. This case also highlights the need for recognizing and managing potential complications associated with catheter ablation procedures. A thorough understanding of these rare but critical events is essential for optimizing patient outcomes and minimizing mortality rates, and physicians and healthcare professionals must remain vigilant regarding such complications.

Ventilation during cardiopulmonary resuscitation is vital to achieve optimal oxygenation but continues to be a subject of ongoing debate. This narrative review aims to provide an overview of various components and challenges of ventilation during cardiopulmonary resuscitation, highlighting key areas of uncertainty in the current understanding of ventilation management. It addresses the pulmonary pathophysiology during cardiac arrest, the importance of adequate alveolar ventilation, recommendations concerning the maintenance of airway patency, tidal volumes and ventilation rates in both synchronous and asynchronous ventilation. Additionally, it discusses ventilation adjuncts such as the impedance threshold device, the role of positive end-expiratory pressure ventilation, and passive oxygenation. Finally, this review offers directions for future research.

The aim the study. Increasing the effectiveness of treatment of chronic generalized periodontitis of moderate severity according to microhemodynamics and oxygenation in periodontal tissues.
METHODS: A clinical and functional study and treatment of chronic generalized periodontitis of moderate degree were conducted in 56 people (22 men and 34 women) aged 37 to 55 years. The patients were divided into 2 groups depending on the type of treatment: group 1 (main) - 28 people (11 men and 17 women, the average age of the group was 43.5±2.8 years, photodynamic therapy (PDT) with 1% dimegin gel using an AFS Spectrum LED emitter with a wavelength of 660 nm and an energy density of 95 J/cm2), in group 2 (control) - 28 people. (9 men and 19 women, the average age of the group was 45.0±3.1 years) standard treatment was performed without PDT. The level of tissue blood flow, its activity and vasomotor activity of microvessels, as well as the blood flow bypass index were determined by laser Doppler flowmetry. The study of oxygenation was carried out by optical tissue oximetry with determination of the index of oxygenation, specific oxygen consumption and perfusion oxygen saturation.
RESULTS: After PDT, the periodontal tissues showed an increase in blood flow by 65.5% after 3 months, the level of oxygen metabolism increased by 51%, which increased after 6 months. The use of PDT in the complex treatment of chronic generalized periodontitis of moderate severity has an activating effect on the microcirculation system and the level of oxygen metabolism in periodontal tissues both in the near and long-term follow-up periods.
CONCLUSIONS: The use of PDT with 1% dimegin gel has an effective effect on the state of microhemodynamics and oxygenation in periodontal tissues.
UNASSIGNED: Повышение эффективности лечения хронического генерализованного пародонтита средней степени тяжести по данным микрогемодинамики и оксигенации в тканях пародонта.
UNASSIGNED: Проведено клинико-функциональное исследование и лечение хронического генерализованного пародонтита средней степени у 56 человек (22 мужчин и 34 женщин) в возрасте от 37 до 55 лет. Пациенты были разделены на 2 группы в зависимости от вида лечения: 1-я группа (основная) — 28 человек (11 мужчин и 17 женщин, средний возраст группы 43,5±2,8 года, фотодинамическую терапию (ФДТ) с 1% гелем на основе 2,4-ди(1-метоксиэтил)-дейтеропорфирина проводили при помощи светодиодного излучателя АФС Спектр с длиной волны 660 нм и плотностью энергии 95 Дж/см2); во 2-й группе (контрольная) — 28 человек (9 мужчин и 19 женщин, средний возраст группы 45,0±3,1 года), проводили стандартное лечение без ФДТ. Методом лазерной допплеровской флоуметрии определяли уровень тканевого кровотока, его активность и вазомоторную реактивность микрососудов, а также показатель шунтирования кровотока. Исследование оксигенации проводили методом оптической тканевой оксиметрии с определением индексов оксигенации, удельного потребления кислорода и перфузионной сатурации кислорода.
UNASSIGNED: После ФДТ в тканях пародонта отмечался рост уровня кровотока через 3 мес на 65,5%, уровень кислородного метаболизма повышался на 51%, эффект еще усиливался через 6 мес. Применение ФДТ в комплексном лечении хронического генерализованного пародонтита средней степени тяжести оказывает активизирующее влияние на систему микроциркуляции и уровень кислородного метаболизма в тканях пародонта как в ближайшие, так и в отдаленные сроки наблюдения.
UNASSIGNED: Применение ФДТ с 1% гелем на основе 2,4-ди(1-метоксиэтил)-дейтеропорфирина оказывает эффективное воздействие на состояние микрогемодинамики и оксигенации в тканях пародонта.

How to cite this article: Mishra S, Kothari N, Sharma A, Goyal S, Rathod DK, Meshram T, et al. Author Response: Beyond the Nasal Prongs: A Joust of Oxygen Delivery Methods in Post-op Hypoxemia. Indian J Crit Care Med 2024;28(6):626-627.

Staphylococcus aureus is commonly isolated from astronauts returning from spaceflight. Previous analysis of omics data from S. aureus low Earth orbit cultures indicated significantly increased expression of the Agr quorum sensing system and its downstream targets in spaceflight samples compared to ground controls. In this current study, the rotary cell culture system (RCCS) was used to investigate the effect of low-shear modeled microgravity (LSMMG) on S. aureus physiology and Agr activity. When cultured in the same growth medium and temperature as the previous spaceflight experiment, S. aureus LSMMG cultures exhibited decreased agr expression and altered growth compared to normal gravity control cultures, which are typically oriented with oxygenation membrane on the bottom of the high aspect rotating vessel (HARV). When S. aureus was grown in an inverted gravity control orientation (oxygenation membrane on top of the HARV), reduced Agr activity was observed relative to both traditional control and LSMMG cultures, signifying that oxygen availability may affect the observed differences in Agr activity. Metabolite assays revealed increased lactate and decreased acetate excretion in both LSMMG and inverted control cultures. Secretomics analysis of LSMMG, control, and inverted control HARV culture supernatants corroborated these results, with inverted and LSMMG cultures exhibiting a decreased abundance of Agr-regulated virulence factors and an increased abundance of proteins expressed in low-oxygen conditions. Collectively, these studies suggest that the orientation of the HARV oxygenation membrane can affect S. aureus physiology and Agr quorum sensing in the RCCS, a variable that should be considered when interpreting data using this ground-based microgravity model.IMPORTANCES. aureus is commonly isolated from astronauts returning from spaceflight and from surfaces within human-inhabited closed environments such as spacecraft. Astronaut health and immune function are significantly altered in spaceflight. Therefore, elucidating the effects of microgravity on S. aureus physiology is critical for assessing its pathogenic potential during long-term human space habitation. These results also highlight the necessity of eliminating potential confounding factors when comparing simulated microgravity model data with actual spaceflight experiments.

OBJECTIVE: There are many approaches to the quantitative BOLD (qBOLD) technique described in the literature, differing in pulse sequences, MRI parameters and data processing. Thus, in this review, we summarized the acquisition methods, approaches used for oxygenation quantification and clinical populations investigated.
METHODS: Three databases were systematically searched (Medline, Embase, and Web of Science) for published research that used qBOLD methods for quantification of oxygen metabolism. Data extraction and synthesis were performed by one author and reviewed by a second author.
RESULTS: A total of 93 relevant papers were identified. Acquisition strategies were summarized, and oxygenation parameters were found to have been investigated in many pathologies such as steno-occlusive diseases, stroke, glioma, and multiple sclerosis disease.
CONCLUSIONS: A summary of qBOLD approaches for oxygenation measurements and applications could help researchers to identify good practice and provide objective information to inform the development of future consensus recommendations.