Ventilatory Pattern Research Articles

Numerical Study on the Operational Ventilation Patterns of Alternative Jet Fans in Curved Tunnels

In tunnel operation ventilation systems, the arrangement of jet fans plays a decisive role in ensuring ventilation efficiency. Curved tunnels, due to their unique radius of curvature, exhibit significant differences in fan installation parameters and jet flow field distribution compared to traditional straight-line tunnels. In order to investigate the distinct characteristics, this research utilized computational fluid dynamics (CFD) simulation methods to analyze the ventilation performance of both an innovative, adjustable jet fan system and conventional jet fans within the context of curved tunnel configurations. The findings reveal that by adjusting the horizontal deflection angle of the novel jet fan, the flow field distribution can be effectively optimized, and the jet effect can be enhanced, thereby improving ventilation efficiency. Compared to traditional jet fans, the novel fan demonstrates a significantly greater capability in flow field optimization, especially when its horizontal deflection angle is adjusted, showing a trend where the jet effect initially increases and then decreases, with the longitudinal impact range being adjustable within a range of 5 m to 25 m.

Nebulized fentanyl does not improve exercise capacity or dyspnoea in fibrosing interstitial lung disease.

Exercise intolerance and exertional dyspnoea are hallmarks of fibrosing interstitial lung disease (FILD) and are associated with worse prognosis and quality of life. Activation of pulmonary vagal afferents influences the ventilatory pattern and contributes to the sensation of dyspnoea. We tested the hypothesis that nebulized fentanyl, which might attenuate aberrant pulmonary afferent activity in FILD, reduces ventilation and dyspnoea while extending exercise endurance time (EET). In this randomized, single-blind, placebo-controlled study, eight FILD patients (two males, 71±6years of age) performed incremental cardiopulmonary cycle exercise tests following nebulization of either fentanyl citrate (100 µg) or 0.9% saline. Previous work indicated that this dose was unlikely to produce central effects. Comparisons between treatment conditions at rest were undertaken using Student's paired t-test, and exercise data were evaluated with two-way ANOVA with repeated measures. Dyspnoea was assessed using the Borg dyspnoea scale. Resting respiratory variables were not different following treatment with fentanyl and saline; however, resting heart rate was lower following fentanyl (P=0.002) and remained lower throughout exercise compared with placebo (P=0.008). Fentanyl did not increase EET (placebo 334±117s vs. fentanyl 348±126s, P=0.250) although overall minute ventilation was reduced slightly (mean difference: -0.97 L/min, P=0.022). There were no differences in ratings of dyspnoea intensity or unpleasantness between the conditions either at rest or at end-exercise. Nebulized fentanyl did not improve EET or exercise dyspnoea but did decrease minute ventilation during exercise, although the extent of this reduction appears clinically insignificant. These findings suggest that nebulized fentanyl is unlikely to offer significant benefits for enhancing exercise capacity in FILD.

Utilising GIS for studying urban entropy, population dynamics, and ventilation disparity: A case study of changing land use, land cover, and socially vulnerable hotspots in Hyderabad, India

Citywide ventilation studies are challenging because they involve complicated interactions between various variables, including anthropogenic variables, housing conditions, and socio-economic considerations. The present paper aims to clarify the complex interactions between these three vital variables and the restricted ventilation zones. The ventilation patterns from 1990 to 2020 are meticulously examined in the first half of this research. This study observed the expansion of built-up areas, which increased from 13.7% in 1990 to 51.8% in 2020. The remainder of the paper explores population dynamics in locations with poor ventilation. In severely ventilated areas, the population increased from 10.7% in 1990 to 16.6% in 2020. The percentage of severely ventilated areas increased from 0.7% in 1990 to 31.6% in 2020, highlighting the urgent need to address ventilation inequities in urban planning. The research uses Spearman correlation analysis, which shows that industrial areas have a substantial positive association with ventilation disparities among anthropogenic factors, indicating the effect of industrial zones on decreased ventilation. The absence of toilets is a powerful and substantial housing variable contributing to poor ventilation. Additionally, the existence of the Total Scheduled Caste population within the socio-economic variables exhibits a strong and significant association, indicating that social issues are intricately linked to ventilation disparities. This research provides critical insights that can inform urban planning and policy decisions to improve ventilation and living conditions in densely populated cities.

Metabolic rate does not scale with body size or activity in some tick species.

Respiration in ticks is highly efficient and exceptionally low. Ticks can survive years between bloodmeals by having low activity and respiration to conserve energetic resources. Our objective was to compare metabolic (VCO2) and activity rates across 6 tick species. We predicted that VCO2 would be different among species and scale linearly with activity and body mass. Activity and CO2 production were measured for 32h in 6 tick species: Dermacentor andersoni, D. variabilis, Haemaphysalis longicornis, Rhipicephalus appendiculatus, R. microplus, and R. sanguineus. Individual ticks were measured for 30min three times to ensure breathing occurred. Absolute and mass-specific VCO2, total activity, body mass, and ventilation patterns were compared among species. As expected, ticks did not always breathe during the 30-minute measurements, especially R. sanguineus. Ventilation patterns differed among species with R. microplus having primarily cyclic patterns and R. appendiculatus having discontinuous gas exchange. VCO2 did not scale with body mass in most species. Haemaphysalis longicornis and R. sanguineus had the lowest VCO2; however, H. longicornis was the second most active species. Life history, including questing behavior and range expansion, could be contributing to differences between species. For instance, H. longicornis had exceptionally low metabolic rates despite above average activity levels, suggesting an energetic advantage which may underlie recently documented range expansions in North America. Our results demonstrate how ticks utilize energetic resources to maximize longevity. Future research describing questing behavior and distribution modeling may help explain differences in metabolic rates and activity and impacts on life history traits.

Environmental Light Controls the Daily Organization of Breathing by Activating Brn3b-expressing Intrinsically Photosensitive Retinal Ganglion Cells in Mice.

Rhythmic, daily fluctuations in minute ventilation are controlled by the endogenous circadian clock located in the suprachiasmatic nucleus (SCN). While light serves as a potent synchronizer for the SCN, it also influences physiology and behavior by activating Brn3b-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs). It is currently unclear the extent to which the external light environment shapes daily ventilatory patterns independent of the SCN. To determine the relative influence of environmental light versus circadian timing on the organization of daily rhythms in minute ventilation, we used whole-body plethysmography to measure the breathing of mice housed on a non-entraining T28 cycle (14 h light:14 h dark). Using this protocol, we found that minute ventilation exhibits a ~28-h rhythm with a peak at dark onset that coincides with the light:dark cycle and the animals' locomotor activity. To determine if this 28-h rhythm in minute ventilation was mediated by Brn3b-expressing ipRGCs, we measured the breathing of Brn3bDTA mice housed under the T28 cycle. Brn3bDTA mice lack the Brn3b-expressing ipRGCs that project to many non-SCN brain regions. We found that despite rhythmic light cues occurring on a 28-h basis, Brn3bDTA mice exhibited 24-h rhythms in minute ventilation, locomotor activity, and core body temperature consistent with organization by the SCN. The 24-h minute ventilation rhythm of Brn3bDTA mice was found to be driven predominantly by tidal volume rather than respiratory rate. These data indicate that the external light:dark cycle can directly drive daily patterns in minute ventilation by way of Brn3b-expressing ipRGCs. In addition, these data strongly suggest that the activation of Brn3b-expressing ipRGCs principally organizes daily patterns in breathing and locomotor activity when light:dark cues are presented in opposition to endogenous clock timing.

Quantifying urban climate response to large-scale forcing modified by local boundary layer effects

Over the past two decades, the joint manifestation of global warming and rapid urbanization has significantly increased the occurrence of heatwaves and the formation of urban heat islands in temperate cities. Consequently, this synergy has amplified the frequency and duration of periods with tropical nights (TNs) in these urban areas. While the occurrences of such extreme events demonstrate irregular and nonlinear annual patterns, they consistently manifest a discernible rising decadal trend in local or regional climatic data. In urban regions situated amidst hilly or mountainous landscapes, changing wind directions—often associated with uphill or downhill thermal flows—profoundly impact the spread and dispersion of heat-related pollution, creating unique natural ventilation patterns. Using the Lausanne/Pully urban area in Switzerland as examples of hilly and lakeshore temperate cities, this study explores the influence of wind patterns and natural urban ventilation on the nonlinearity of recorded climatic data within an urban environment. This study integrates a mesoscale numerical weather prediction model (COSMO-1), a microscale Computational Fluid Dynamics (CFD) model, field observations, variational mode decomposition technique, and statistical analysis to investigate how wind speed and direction critically influence the nonlinearity of recorded long-term trends of extreme events, specifically focusing on the frequency and duration of TNs in lakeshore and hilly cities. The results strongly indicate a direct correlation between the frequency of TNs and the occurrence of specific moderate wind patterns. These wind patterns are exclusively captured by the microscale CFD model, unlike the mesoscale model, which neglects both urban morphology and complex hilly terrains. The impact of temporal and spatial variability of the wind field on long-term observations at fixed measurement stations suggests that caution should be exercised when relying on limited spatial measurement points to monitor and quantify long-term urban climate trends, particularly in cities located in complex terrains.

Shared sanitation facilities and risk of respiratory virus transmission in resource-poor settings: A COVID-19 modeling case study.

Water supply and sanitation are essential household services frequently shared in resource-poor settings. Shared sanitation can increase the risk of enteric pathogen transmission due to suboptimal cleanliness of facilities used by large numbers of individuals. It also can potentially increase the risk of respiratory disease transmission. As sanitation is an essential need, shared sanitation facilities may act as important respiratory pathogen transmission venues even with strict control measures such as stay-at-home recommendations in place. This analysis explores how behavioral and infrastructural conditions surrounding shared sanitation may individually and interactively influence respiratory pathogen transmission. We developed an individual-based community transmission model using COVID-19 as a motivating example parameterized from empirical literature to explore how transmission in shared latrines interacts with transmission at the community level. We explored mitigation strategies, including infrastructural and behavioral interventions. Our review of empirical literature confirms that shared sanitation venues in resource-poor settings are relatively small with poor ventilation and high use patterns. In these contexts, shared sanitation facilities may act as strong drivers of respiratory disease transmission, especially in areas reliant on shared facilities. Decreasing dependence on shared latrines was most effective at attenuating sanitation-associated transmission. Improvements to latrine ventilation and handwashing behavior were also able to decrease transmission. The type and order of interventions are important in successfully attenuating disease risk, with infrastructural and engineering controls being most effective when administered first, followed by behavioral controls after successful attenuation of sufficient alternate transmission routes. Beyond COVID-19, our modeling framework can be extended to address water, sanitation, and hygiene measures targeted at a range of environmentally mediated infectious diseases.

Airflow and aerosol transport in the hospital isolation zone based on dynamic scenarios

To contain the leakage of viral aerosols, buffer rooms are usually provided in front of isolation wards. However, dynamic events of door movement and healthcare worker (HCW) walking will result in highly concentrated aerosols intruding into the buffer room from the ward, challenging the control of virus transmission risk. In this work, airflow exchange and bioaerosol particle transport between the negative-pressure isolation ward and the buffer room under dynamic scenarios were studied by transient computational fluid mechanics (CFD) simulation, thereby the fate of particles was divided into invasion stage and decay stage. The effects of ventilation pattern and HCW location on the concentration level and attenuation trend of particles were quantitatively analyzed. The results showed that increasing the HCW walking distance could increase the peak particle concentration within the buffer room by 4.5 % during the invasion stage. The effect of the buffer room ventilation layout on air exchange and particle transport was more pronounced than the HCW stay position. In the decay stage, the two more effective ventilation layouts could decrease the complete clearance time of particles and the particle concentration in the breathing zone by 31 % and 42 %, respectively. To reduce the infection risk, bioaerosol levels need to be reduced both in the buffer room and in the HCW breathing zone.

Improved exercise ventilatory efficiency with nasal compared to oral breathing in cardiac patients.

Objectives: To assess whether nasal breathing improves exercise ventilatory efficiency in patients with heart failure (HF) or chronic coronary syndromes (CCS). Background: Exercise inefficient ventilation predicts disease progression and mortality in patients with cardiovascular diseases. In healthy people, improved ventilatory efficiency with nasal compared to oral breathing was found. Methods: Four study groups were recruited: Patients with HF, patients with CCS, old (age≥45years) and young (age 20-40years) healthy control subjects. After a 3-min warm-up, measurements of 5min with once nasal and once oral breathing were performed in randomized order at 50% peak power on cycle ergometer. Ventilation and gas exchange parameters measured with spiroergometry were analysed by Wilcoxon paired-sample tests and linear mixed models adjusted for sex, height, weight and test order. Results: Groups comprised 15 HF, CCS, and young control and 12 old control. Ventilation/carbon dioxide production ( E/ CO2), ventilation ( E), breathing frequency (fR), and end-tidal oxygen partial pressure (PETO2) were significantly lower and tidal volume and end-tidal carbon dioxide partial pressure (PETCO2) significantly higher during nasal compared to oral breathing in all groups, with large effect sizes for most parameters. For patients with HF, median E/ CO2 was 35% lower, fR 26% lower, and PETCO2 10% higher with nasal compared to oral breathing, respectively. Exercise oscillatory ventilation (EOV) was present in 6 patients and markedly reduced with nasal breathing. Conclusion: Nasal breathing during submaximal exercise significantly improved ventilatory efficiency and abnormal breathing patterns (rapid shallow breathing and EOV) in 80% of our patients with HF and CCS.

Depleted Housing Elicits Cardiopulmonary Dysfunction After a Single Flaming Eucalyptus Wildfire Smoke Exposure in a Sex-Specific Manner in ApoE Knockout Mice

Although it is well established that wildfire smoke exposure can increase cardiovascular morbidity and mortality, the combined effects of non-chemical stressors and wildfire smoke remains understudied. Housing is a non-chemical stressor that is a major determinant of cardiovascular health, however, disparities in neighborhood and social status have exacerbated the cardiovascular health gaps within the United States. Further, pre-existing cardiovascular morbidities, such as atherosclerosis, can worsen the response to wildfire smoke exposures. This represents a potentially hazardous interaction between inadequate housing and stress, cardiovascular morbidities, and worsened responses to wildfire smoke exposures. The purpose of this study was to examine the effects of enriched (EH) versus depleted (DH) housing on pulmonary and cardiovascular responses to a single flaming eucalyptus wildfire smoke (WS) exposure in male and female apolipoprotein E (ApoE) knockout mice, which develop an atherosclerosis-like phenotype. The results of this study show that cardiopulmonary responses to WS exposure occur in a sex-specific manner. EH blunts adverse WS-induced ventilatory responses, specifically an increase in tidal volume (TV), expiratory time (Te), and relaxation time (RT) after a WS exposure, but only in females. EH also blunted an increase in isovolumic relaxation time (IVRT) and the myocardial performance index (MPI) 1-week after exposures, also only in females. Our results suggest that housing alters the cardiovascular response to a single WS exposure, and that DH might cause increased susceptibility to environmental exposures that manifest in altered ventilation patterns and diastolic dysfunction in a sex-specific manner.

The developmental phenotype of motor delay in extremely preterm infants following early-life respiratory adversity is influenced by brain dysmaturation in the parietal lobe

BackgroundResearch indicates that preterm infants requiring prolonged mechanical ventilation often exhibit suboptimal neurodevelopment at follow-up, coupled with altered brain development as detected by magnetic resonance imaging (MRI) at term-equivalent age (TEA). However, specific regions of brain dysmaturation and the subsequent neurodevelopmental phenotype following early-life adverse respiratory exposures remain unclear. Additionally, it is uncertain whether brain dysmaturation mediates neurodevelopmental outcomes after respiratory adversity. This study aims to investigate the relationship between early-life adverse respiratory exposures, brain dysmaturation at TEA, and the developmental phenotype observed during follow-up in extremely preterm infants.Methods89 infants born < 29 weeks’ gestation from 2019 to 2021 received MRI examinations at TEA for structural and lobe brain volumes, which were adjusted with sex-and-postmenstrual-age expected volumes for volume residuals. Assisted ventilation patterns in the first 8 postnatal weeks were analyzed using kmlShape analyses. Patterns for motor, cognition, and language development were evaluated from corrected age 6 to 12 months using Bayley Scales of Infant Development, third edition. Mediation effects of brain volumes between early-life respiratory exposures and neurodevelopmental phenotypes were adjusted for sex, gestational age, maternal education, and severe brain injury.ResultsTwo distinct respiratory trajectories with varying severity were identified: improving (n = 35, 39%) and delayed improvement (n = 54, 61%). Compared with the improving group, the delayed improvement group exhibited selectively reduced brain volume residuals in the parietal lobe (mean − 4.9 cm3, 95% confidence interval − 9.4 to − 0.3) at TEA and lower motor composite scores (− 8.7, − 14.2 to − 3.1) at corrected age 12 months. The association between delayed respiratory improvement and inferior motor performance (total effect − 8.7, − 14.8 to − 3.3) was partially mediated through reduced parietal lobe volume (natural indirect effect − 1.8, − 4.9 to − 0.01), suggesting a mediating effect of 20%.ConclusionsEarly-life adverse respiratory exposure is specifically linked to the parietal lobe dysmaturation and neurodevelopmental phenotype of motor delay at follow-up. Dysmaturation of the parietal lobe serves as a mediator in the connection between respiratory adversity and compromised motor development. Optimizing respiratory critical care may emerge as a potential avenue to mitigate the consequences of altered brain growth and motor developmental delay in this extremely preterm population.

Delivery of Inhaled Medication in Children: Revisiting Pharmacological and Practical Issues for Better Health Outcome

For safe and effective therapy of respiratory disorders in children, delivering the medication at the site of disease i.e. directly into the respiratory tract via aerosolized medication is critical. But, the anatomical and physiological differences in the respiratory tract of infants/children and adults make the delivery of aerosolized medication complicated. This review article gives an overview of the delivery of inhaled medication in children and discuss the pharmacological and specific clinically relevant aspects of medication delivery using nebulizers, pressurized metered dose inhalers (MDIs), and dry powder inhalers (DPIs) in children. As a physician, one should always keep in mind the various factors like properties of the device, aerosol particle, patient factors such as disease state, ventilatory pattern, and administration technique that can affect drug deposition via aerosol delivery devices.

Differences in Exercise Capacity, Ventilatory Efficiency, and Gas Exchange between Patients with Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension Residing at High Altitude.

Cardiopulmonary exercise testing (CPET) assesses exercise capacity and causes of exercise limitation in patients with pulmonary hypertension (PH). At altitude, changes occur in the ventilatory pattern and a decrease in arterial oxygen pressure in healthy; these changes are increased in patients with cardiopulmonary disease. Our objective was to compare the response to exercise and gas exchange between patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) residing at the altitude of Bogotá (2640 m). All patients performed an incremental CPET with measurement of oxygen consumption ( ), dead space (VD/VT), ventilatory equivalents (VE/ ), and alveolar-arterial oxygen gradient ( ). test and one-way analysis of variance were used for comparisons between PAH and CTEPH. We included 53 patients, 29 with PAH, 24 with CTEPH, and 102 controls as a reference of the normal response to exercise at altitude. CTEPH patients had a higher New York Health Association (NYHA) functional class than PAH (p = 0.037). There were no differences between patients with PAH and CTEPH in hemodynamics and % of predicted (67.8 18.7 vs. 66.0 19.8, p 0.05), but those with CTEPH had higher dyspnea, VD/VT (0.36 0.09 vs. 0.23 0.9, p 0.001), VE/ (45.8 7.1 vs. 39.3 5.6, p 0.001), and (19.9 7.6 vs. 13.5 7.6, p 0.001) than PAH patients. At altitude, patients with PH present severe alterations in gas exchange during exercise. There were no differences in exercise capacity between PAH and CTEPH, but patients with CTEPH had more dyspnea and greater alterations in gas exchange during exercise. CPET made it possible to identify alterations related to the pathophysiology of CTEPH that could explain the functional class and dyspnea in these patients.

Temporal Variability of Ventilation in the Eurasian Arctic Ocean

AbstractThe Arctic Ocean plays an important role in the regulation of the earth's climate system, for instance by storing large amounts of carbon dioxide within its interior. It also plays a critical role in the global thermohaline circulation, transporting water entering from the Atlantic Ocean to the interior and initializing the southward transport of deep waters. Currently, the Arctic Ocean is undergoing rapid changes due to climate warming. The resulting consequences on ventilation patterns, however, are scarce. In this study we present transient tracer (CFC‐12 and SF6) measurements, in conjunction with dissolved oxygen concentrations, to asses ventilation and circulation changes in the Eurasian Arctic Ocean over three decades (1991–2021). We constrained transit time distributions of water masses in different areas and quantified temporal variability in ventilation. Specifically, mean ages of intermediate water layers in the Eurasian Arctic Ocean were evaluated, revealing a decrease in ventilation in each of the designated areas from 2005 to 2021. This intermediate layer (250–1,500 m) is dominated by Atlantic Water entering from the Nordic Seas. We also identify a variability in ventilation during the observation period in most regions, as the data from 1991 shows mean ages comparable to those from 2021. Only in the northern Amundsen Basin, where the Arctic Ocean Boundary Current is present at intermediate depths, the ventilation in 1991 is congruent to the one in 2005, increasing thereafter until 2021. This suggests a reduced ventilation and decrease in the strength of the Boundary Current during the last 16 years.

Exploring thermal buoyant flow in urban street canyons: Influence of approaching turbulent boundary layer

Turbulent boundary layer inflow is a critical factor in urban climate research, shaping canyon flow dynamics, air ventilation patterns, and heat flux distribution. In numerical simulation studies, it serves as a fundamental inflow boundary condition, profoundly influencing overall results. In this study, simultaneous Particle Image Velocimetry and Laser-Induced Fluorescence (PIV-LIF) measurements are utilized within a large closed-circuit water tunnel. This approach allows comprehensive flow data to be gathered under varied flow and thermal conditions, encompassing a spectrum of Richardson numbers ranging from 0.01 to 1.34. The investigation aims to elucidate the effects of turbulent boundary layer flows on heat transfer mechanisms and flow behaviours within a two-dimensional street canyon model with a unit aspect ratio. The analysis reveals distinct heat and fluid flow characteristics, highlighting the interplay between thermal conditions and flow dynamics. The three chosen turbulent boundary layer flows demonstrate unique influences on flow characteristics and heat removal capacity. Significant variations in ventilation rates are observed, with a maximum difference of 80% among the tested boundary layer flows. Additionally, the most pronounced variation in heat removal capacity is approximately 45%. Thicker boundary layers with lower velocities near the canyon exhibit reduced ventilation and heat removal capabilities. Furthermore, the investigation reveals that varied turbulence inlet profiles result in diverse fluctuating features at the canyon roof level, with a comparatively lesser impact on the deeper regions of the canyon.

In Vivo Measurement of Tidal Volume During Non-invasive Respiratory Support by Continuous-Flow Helmet CPAP

Recently, the interest in the Helmet interface during non-invasive respiratory support (NIRS) has increased due to the COVID-19 pandemic. During NIRS, positive end-expiratory pressure (PEEP) can be given as continuous positive airway pressure (CPAP), which maintains a positive airway pressure throughout the whole respiratory cycle with Helmet as an interface (H-CPAP). The main disadvantage of the H-CPAP is the inability to measure tidal volume (VT). Opto-electronic plethysmography (OEP) is a non-invasive technique that is not sensitive to gas compression/expansion inside the helmet. OEP acquisitions were performed on 28 healthy volunteers (14 females and 14 males) at baseline and during Helmet CPAP. The effect of posture (semi-recumbent vs. prone), flow (50 vs. 60 L/min), and PEEP (0 vs. 5 vs. 10 cmH2O) on the ventilatory and thoracic-abdominal pattern and the operational volumes were investigated. Prone position limited vital capacity, abdominal expansion and chest wall recruitment. A constant flow of 60 L/min reduced the need for the subject to ventilate while having a slight recruitment effect (100 mL) in the semi-recumbent position. A progressive increasing recruitment was found with higher PEEP but limited by the prone position. It is possible to accurately measure tidal volume during H-CPAP to deliver non-invasive ventilatory support using opto-electronic plethysmography during different clinical settings.

Involvement of the Lung Parenchyma Analyzed by Frequency Components of the Tidal Volume Assessed by Electrical Bioimpedance

Pulmonary function tests are vital for detecting pathologies, especially chronic obstructive pulmonary diseases (COPD), emphasizing the importance of assessing lung parenchyma involvement in maintaining proper gas exchange. Electrical impedance tomography (EIT) offers a non-invasive alternative for respiratory function evaluation while preserving natural breathing. We propose using EIT to detect lung parenchyma conditions by analyzing tidal volume patterns (by averaging the impedance image) in the frequency domain. Twenty COPD patients underwent simultaneous evaluation with a pneumotachometer and an EIT device, performing three 30-second respiratory maneuvers. FFT spectra analysis yielded parameters, including the area under the curve and quartiles (25 %, 50 %, 75 %) of power values in six frequency regions. Correlations between these parameters and clinical test results (pulmonary diffusing capacity and arterial blood gas analysis) revealed significant associations, particularly with PCO2. Multiple linear regression analysis predicted PCO2 with an R2adj = 0.827, suggesting the potential for non-invasively detecting lung parenchyma affectation by correlating FFT bioimpedance ventilatory patterns with gas exchange performance in COPD patients.

Links between systemic inflammation and the chemoreflex control of breathing following COVID-19

The emergence of SARS-CoV-2 resulted in millions of hospitalizations and 6.9 million deaths to-date. Many individuals who recover from COVID-19 report prolonged dyspnea, with this symptom persisting for months following recovery. Furthermore, data suggests COVID-19 has been linked to systemic and neuronal inflammation which may have downstream impacts on the neural control of breathing. As such, we hypothesized that individuals recovered from COVID-19 may exhibit changes in their ventilatory chemosensitivity to CO2 and/or O2 and that these changes may be linked to higher levels of systemic inflammation. To test this hypothesis, we measured baseline ventilatory patterns and chemoreflex sensitivity using a modified rebreathing technique in individuals recovered from COVID-19 (n = 77), as well as an age and sex-matched control group (n = 41). Peripheral blood samples were also collected for inflammatory profiling. Recovered participants demonstrated lower ventilatory responses to hypercapnia, particularly under a combined hypoxic stimulus (p = 0.032). Furthermore, higher levels of plasma IL-1β and IL-6 were associated with lower hypoxic ventilatory responses (R2 = -0.53, p = 0.025; R2 = -0.49, p = 0.04), highlighting a potential link between systemic inflammation and ventilatory chemoreflex sensitivity. When separated by time-post-recovery, we observed a decreased ventilatory recruitment threshold (VRT) beginning at 4 months post-recovery (p = 0.019) that returned to baseline after one-year post-recovery. A decrease in sensitivity to CO2 was also noted immediately after recovery with no return to baseline observed within the two-year tested time frame (p = 0.023). Overall, this data indicates that (1) COVID-19 may have impacts on the neural control of breathing, and (2) systemic inflammation may play a role in modulating ventilatory chemoreflex sensitivity. These findings may have implications for the pathology of long-COVID symptoms, including sleep disturbance and prolonged dyspnea. This work was funded by the Health Disparities Research Center and the OASIS center at University of California, Riverside. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Contribution of electrical impedance tomography to personalize positive end-expiratory pressure under ECCO2R

Extracorporeal Carbon Dioxide Removal (ECCO2R) is used in acute respiratory distress syndrome (ARDS) patients to facilitate lung-protective ventilatory strategies. Electrical Impedance Tomography (EIT) allows individual, non-invasive, real-time, bedside, radiation-free imaging of the lungs, providing global and regional dynamic lung analyses. To provide new insights for future ECCO2R research in ARDS, we propose a potential application of EIT to personalize End-Expiratory Pressure (PEEP) following each reduction in tidal volume (VT), as demonstrated in an illustrative case. A 72-year-old male with COVID-19 was admitted to the ICU for moderate ARDS. Monitoring with EIT was started to determine the optimal PEEP value (PEEPEIT), defined as the intersection of the collapse and overdistention curves, after each reduction in VT during ECCO2R. The identified PEEPEIT values were notably low (< 10 cmH2O). The decrease in VT associated with PEEPEIT levels resulted in improved lung compliance, reduced driving pressure and a more uniform ventilation pattern. Despite current Randomized Controlled Trials showing that ultra-protective ventilation with ECCO2R does not improve survival, the applicability of universal ultra-protective ventilation settings for all patients remains a subject of debate. Inappropriately set PEEP levels can lead to alveolar collapse or overdistension, potentially negating the benefits of VT reduction. EIT facilitates real-time monitoring of derecruitment associated with VT reduction, guiding physicians in determining the optimal PEEP value after each decrease in tidal volume. This original description of using EIT under ECCO2R to adjust PEEP at a level compromising between recruitability and overdistention could be a crucial element for future research on ECCO2R.

Seasonal ventilation controls nitrous oxide emission in the NW Iberian upwelling

Despite their small spatial extent, coastal upwelling systems are an important source of oceanic nitrous oxide (N2O) to the atmosphere. To date, hot-spot N2O emissions have been reported for low oxygen waters of the eastern boundary upwelling systems at their tropical latitudes, but there is a limited number of studies in their “oxygenated” temperate latitudes. This is the first study of the N2O cycle in the NW Iberian Upwelling system, where we investigated the seasonality of the N2O concentrations and their emissions to the atmosphere, along with the spatial differences in this coastal region in response to the upwelling. Monthly observations were collected from February 2017 to July 2018, in two hydrographic sections within the Ría of Vigo and Ría of A Coruña, two coastal embayments with contrasting response to the upwelling of the Eastern North Atlantic Central Water (ENACW) in the region. N2O concentrations ranged between 8.56 to 12.53 nmol kg−1 (94–121 % of saturation) in the shelf, and from 8.62 to 17.60 nmol kg−1 (94–203 % of saturation) inside the rías, with the highest N2O concentration at the bottom, which increase as the upwelling progress from April to October. The air-sea fluxes of N2O varied between −1.6 to 3.26 µmol m−2 d−1 in the shelf and −1.53 to 7.00 µmol m−2 d−1 inside the rías. Local differences on the ventilation and remineralization pattern drives the seasonality of N2O and differences between Ria of Vigo and Ria of A Coruña, being the higher values of N2O concentrations and air-sea fluxes registered in the inner Ria of Vigo. Our study reports the N2O emissions of an upwelling system in a temperate latitude, where the upwelling waters are central waters relatively well ventilated in terms of oxygen content, behaving as a moderate low net source of N2O to the atmosphere compared to tropical upwelling latitudes, characterised by a lower oxygen content.