Household air pollution (HAP), particularly from cooking-related particulate matter (PM2.5), poses significant health risks but remains understudied compared to ambient air pollution. We evaluated the short-term cardiorespiratory effects of exposure to cooking-generated PM2.5 and examined the efficacy of automated indoor air quality interventions. Using a crossover design, seven cohorts of two participants each were exposed to two residential conditions over four weeks in a Living Lab: the Standard Control Condition (SCC), featuring basic HVAC, and the Advanced Control Condition (ACC), which included automated range hoods, portable air cleaners and exhaust systems activated by PM2.5 sensors. PM2.5 concentrations were continuously monitored in the breathing zone at the room level. The physiological markers, blood pressure (BP), heart rate (HR), heart rate variability (HRV) and fractional exhaled nitric oxide (FeNO), were measured on the occupant before and after cooking events. Cooking events caused substantial short-term increases in PM2.5 levels, median concentrations rose from < 1 µg/m³ to 263.7 µg/m³ under SCC and to 168.9 µg/m³ under ACC during HRV measurement periods, with exposure levels exceeding WHO 24-hour guidelines up to 82% of the time. Compared to SCC, the ACC significantly reduced PM2.5 exposure (p < 0.05). Systolic blood pressure (SBP) decreased significantly post-cooking under ACC (ΔSBP = -3.1 ± 10.0 mmHg) but not in the SCC (ΔSBP = -0.9 ± 8.0 mmHg; p < 0.05). HR and HRV showed no statistically significant differences between conditions, though trends in RMSSD, SDNN and LF/HF ratio suggested improved autonomic balance under ACC. HR decreased post-cooking under ACC but increased slightly under SCC (ΔHR = -4.5 ± 6.5 bpm vs. 1.0 ± 1.1 bpm; 95% CI: (-9.8 to -1.2)). FeNO decreased significantly within both conditions pre- to post-cooking, but the difference in reduction between conditions did not reach statistical significance, despite a trend toward greater decline in the ACC. These findings suggest that semi-chronic exposure to cooking-related PM2.5 can adversely affect cardiovascular function, particularly systolic BP and HR, and that automated indoor air quality interventions can meaningfully reduce pollutant exposure and associated physiological impacts. Our results support the implementation of HAP mitigation strategies in residential settings and highlight the need for further research among populations with existing cardiopulmonary conditions.

INTRODUCTION:Detecting and estimating blood volume loss are important for the diagnosis and management of life-threatening hemorrhage. There is a direct relationship between percent blood volume loss (BVL%) and falling in stroke volume (SV); furthermore, there is a direct relationship between diminishing SV and the corrected flow time of the carotid artery (ccFT). Therefore, we hypothesized that change in ccFT (ccFTΔ) would directly relate with BVL% in a phlebotomy paradigm. MATERIALS AND METHODS:A prospective, convenience sample of healthy volunteers was studied. Volunteers underwent blood donation protocol in a physiology lab. A wireless, wearable Doppler ultrasound system monitored ccFT during blood donation. Traditional vital signs were also measured throughout. The relationship between traditional vital signs as well as ccFTΔ were compared to BVL% using 2 mixed linear regression models. RESULTS:Data from 20 subjects and blood donations comprising 46,123 cardiac cycles are included. On average 413.5 ± 39 mL of blood were drawn representing 8.6 ± 1.6% BVL%. There was a significant and strong linear relationship between BVL% and ccFTΔ during blood draw with the regression slope demonstrating that for every 1 ms reduction in ccFT there was a 0.4% reduction in blood volume. CONCLUSIONS:In healthy subjects and when blood loss is the sole mechanism for falling SV, we estimate that for every 1 ms reduction in ccFT, there is an approximate 0.4 BVL%. Validation of these results in patients with traumatic hemorrhage is underway.

Abstract Brief inhalation of carbon dioxide (CO2) has been proposed to counteract transient hypocapnia by enhancing oxygen unloading, vasodilation, and sympathetic modulation. Despite these potential ergogenic mechanisms, CO2 has rarely been investigated in the exercise context. The present study investigated whether brief CO2 inhalation (iCO2) influences performance and recovery during high‐intensity interval exercise. Nine healthy adults completed two randomized, single‐blinded crossover trials of repeated cycling intervals at 85% peak work rate until volitional exhaustion or cadence dropped below 60 rpm, with a minimum 2‐min interval duration required and 3‐min active recovery between bouts. Participants inhaled 5% CO2 or room air (15 breaths) before and after each exercise bout. Gas exchange, cardiovascular responses, and perceived exertion were assessed. Total exercise time was similar between trials; however, participants completed more intervals with iCO2. During the first interval, iCO2 increased exercise duration and VO2. At matched exercise time, perceived exertion and dyspnea were lower with iCO2. During recovery, systolic blood pressure was lower and heart rate was higher following iCO2. Brief iCO2 improved first‐interval performance, altered cardiovascular recovery, and reduced perceptual strain but did not extend overall exercise duration. These findings suggest iCO2 may transiently modulate tolerance and autonomic‐vascular responses during high‐intensity interval exercise.

Background Uphill walking is a popular low-impact exercise for fitness and weight management, but most treadmills are limited to 12%–15% grades. Few studies have examined the metabolic cost of more extreme grades. Purpose To quantify energy expenditure (EE) during steep uphill walking, identify factors influencing EE variability, compare fixed-speed versus self-selected (SS) speeds, and examine potential hysteresis between ascending and descending protocols. Methods Twenty healthy adults (12 males/8 females; [37.20 ± 7.49] y; body mass index [BMI] = [24.37 ± 2.67] kg/m2) completed Fixed (1.5 mph) and SS protocols on separate days. Grades increased sequentially from 0% to 40% (4 min/stage), followed by a descending sequence after 30 min recovery. Oxygen consumption ( O2) was continuously measured and EE calculated. Results EE rose significantly with grade (p < 0.001). In Fixed, EE increased linearly to 30% and sharply at 40%, reaching ∼2.9-fold higher than 5% and ∼1.9-fold higher than 12%–15%. In SS, EE plateaued beyond 20%, increasing only ∼30% from 15% to 40%. Variability rose with grade (p < 0.05) and was associated with sex (p < 0.001), with additional contributions from body weight and age. Hysteresis occurred in Fixed but was attenuated in SS. American College of Sports Medicine (ACSM)-predicted EE correlated strongly (R2 > 0.9) but overestimated values at 30%–40% by up to 18%. Conclusions Steep-incline walking (30%–40%) markedly elevates EE comparable to level running (∼6 mph). Increasing inclines amplify inter-individual variability and alter metabolic hysteresis, underscoring the need for revised predictive equations for extreme grades.

Postprandial blood glucose (BG) regulation is a central determinant of metabolic health and cardiometabolic risk. While conventional exercise effectively lowers postprandial BG, alternative approaches that impose minimal musculoskeletal load remain underexplored. Inspiratory loading (IL) -repeated inspirations against graded resistance -selectively activates oxidative respiratory muscles. However, its real-time metabolic and mechanical demands and their influence on systemic glucose regulation have not been quantified. In this study, we quantitatively characterized the concurrent metabolic and mechanical responses to graded IL and examined their acute effects on postprandial BG in healthy adults. Six participants completed three randomized IL sessions-SHAM (no resistance), MOD (~ 40% maximal inspiratory pressure, MIP), and HIGH (~ 60% MIP)-separated by ≥ 72-h washouts. After fasting measurements, participants ingested 45 g of D-glucose followed by a 30-min IL protocol (6 × 4-min bouts with 1-min rest). Oxygen consumption (VO2), heart rate (HR), inspiratory pressure (IP), and estimated work of breathing (eWOB) were continuously recorded, and BG was measured before and after IL. Glucose ingestion elevated BG across all conditions. IL elicited load-dependent increases in VO2, HR, IP, and eWOB, with MOD and HIGH both significantly elevated relative to SHAM. Post-IL, BG decreased in HIGH and MOD but remained elevated in SHAM (p < 0.05). The change in BG correlated inversely with both VO2 and inspiratory effort indices (IP, eWOB; r = - 0.54 to - 0.59). These findings provide quantitative evidence that respiratory muscle activation alone can elevate whole-body metabolic demand and acutely attenuate postprandial BG elevation. Inspiratory loading, therefore, represents a unique, accessible, and time-efficient stimulus capable of engaging both metabolic and mechanical pathways relevant to glycemic regulation across diverse populations.

Introduction:Ultra-marathon races present a prolonged cardiopulmonary physiological stress but the magnitude, persistence, and impact of race environment on respiratory function are incompletely understood. The aim of this study is to observe the effect of ultra-marathon trail races on both lung function and airway impedance. Methods:Fifty-seven individuals (49/8, M/F) participated in either the Courmayeur-Champex-Chamonix (CCC®, 101.5km), Ultra Trail du Mont-Blanc (UMTB®, 171.5 km), or the Hong Kong 100 (HK, 100 km) races. Participant demographics were measured pre-race and included: age (40.7±10.3 yrs); height (175.5±7.1 cm), body mass (69.7±8.3 kg). Spirometry, airway impedance (via forced oscillation technique, FOT), maximal inspiratory (MIP) and expiratory pressure (MEP), and exhaled nitric oxide (ExNO) were assessed before, immediately (18-4 hours after), and 188-24 hours post-race. Mixed effects analysis with Dunnett's post-hoc correction were conducted to evaluate the effects of race and time. Results:Results demonstrated significant effects of time for: forced vital capacity (FVC), forced expiratory flow over one second (FEV1), peak expiratory flow (PEF), forced expiratory flow between 25-75% (FEF25-75), forced expiratory flow at 25% and at 50% (FEF25 and FEF50, respectively), MIP, MEP, airway reactance (X) at all frequencies from FOT (X5, X11, X19), respiratory rate, and ExNO (all p<0.05). A significant effect of race was also observed for ExNO (p=0.002). Discussion:Findings indicate declines in lung function and airway impedance immediately after ultra-marathon races, some of which, persisted up to 24 hours post-race. Further investigations are required to better understand the etiology of changes in lung function following ultra-endurance events.

Abstract Aim We investigated whether a commercial bi‐level positive airway pressure (BPAP) device, would improve peripheral oxygen saturation (SpO2) during recreational aviation up to 12,500 feet without supplemental oxygen. Ten adults with recreational flight experience (age:47 ± 14; female = 5) completed a standardized flight profile in an unpressurised aircraft, involving randomized crossover design at 8,000 feet and 12,500 feet with BPAP or control. SpO2, middle cerebral artery velocity (MCAv), heart rate (HR), respiratory rate (RR), and relative tidal volume (TV) index were measured continuously. Psychomotor vigilance test (3‐min) assessed reaction time halfway through taxi and altitude stages. Altitude significantly (p < 0.05) decreased mean SpO2, MCAv, and RR, and increased TV index and HR. There was no effect of altitude (p > 0.05) on reaction time. BPAP increased mean SpO2 at 8,000 feet [Control: 92 ± 1%; BPAP: 94 ± 2%; mean difference (MD) = 2 ± 2%; p = 0.002] and 12,500 feet [Control: 86 ± 4%; BPAP: 89 ± 4%; MD = 2 ± 3%; p = 0.013]. BPAP lowered MCAv at 8,000 feet [Control: 53 ± 10 cm/s; BPAP: 50 ± 9 cm/s; MD = ‐3 ± 2 cm/s; p = 0.001] and 12,500 feet [Control: 52 ± 10 cm/s; BPAP: 50 ± 8 cm/s; MD = ‐2 ± 3 cm/s; p = 0.041]. BPAP increased TV index at 8,000 feet (Control: 6.6 ± 1.3; BPAP:8.1 ± 1.8; MD = 1.9 ± 0.8; p < 0.001) but not 12,500 feet, without effect on RR or reaction time. This study provides preliminary results that BPAP may improve mean SpO2 for recreational aviators up to 12,500 feet without supplemental oxygen.

Intermittent hypoxia has been used to enhance oxygen delivery in athletes and patients; however, it is unclear whether acute exposure is sufficient to elicit lasting physiologic adaptation(s). The purpose of this study was to evaluate physiologic response(s) to hypobaric‐hypoxic (HH) exercise. Nine participants (4 M/5F; 37.9 ± 12.7 yrs.; 174.3 ± 9.4 cm; 75.3 ± 15.9 kg; 24.4 ± 3.4 kg/m 2 ) were exposed to progressively higher simulated altitudes and completed two HH submaximal exercise sessions (~30 min ea., ≥72 h apart) on a cycle ergometer at the first altitude that posed a significant challenge to them. Altitude was dependent on individual response as determined from heart rate (HR), peripheral oxygenation (SpO 2 ), and the ratio of HR response to SpO 2 (HR/SpO 2 ). Statistical analyses included paired samples t ‐test ( p ≤ 0.05). No significant change in SpO 2 (HH‐1: 85 ± 4% vs. HH‐2: 85 ± 4%, p = 0.684) was observed between sessions. However, there were significant decreases in: HR (HH‐1: 150 ± 18 bpm vs. HH‐2: 133 ± 27 bpm, p = 0.001) of 18 bpm (11%); HR/SpO 2 (HH‐1: 1.76 ± 0.22 vs. HH‐2: 1.57 ± 0.33, p = 0.012); and RPE (HH‐1: 15 ± 2 vs. HH‐2: 11 ± 4, p = 0.017). While workload significantly increased (HH‐1: 89 ± 36 W vs. HH‐2: 105 ± 36 W, p = 0.024). Some participants had a threshold/challenging altitude, but from a single bout there is evidence of improved tolerance that can last over a week. Further investigation is required to replicate and understand possible mechanisms.

Rationale: Heart failure (HF) is often characterized by elevated left ventricular filling pressures (LVFP) and pulmonary congestion. However, LVFP may not always predict congestion. Pulmonary congestion can be quantified by computed tomography (CT) imaging. We hypothesized that extravascular lung water quantified by CT may differ in HF groups such as HF with preserved ejection fraction (HFpEF) vs HF with reduced ejection fraction (HFrEF), inpatients with acute decompensated heart failure (ADHF) vs stable and this would be related to echocardiography (echo) derived estimates of LVFP. Methods: We enrolled and studied 83 patients with HF who were either admitted or had a clinic visit at Mayo Clinic, Rochester, MN from May 2018 through March 2019. All subjects underwent comprehensive echo and supine thoracic CT scans. CT lung fluid was quantified and reported as proportion (%) of total lung volume. CT attenuation in lung tissue was also measured. LVFP was evaluated according to standardized echo diagnostic algorithms. Patients were stratified based on clinical diagnosis of HF as inpatients with HFpEF (n=26, 75.6±8.5yrs, M=50%, BMI=36.2±8.9kg/m2) inpatients with HFrEF (n=33, 75.6±14yrs, M=79%, BMI=31.1±9.1kg/m2), inpatients with ADHF (n=14, 72.6±14.5yrs, m=64.2%, BMI= 32.2±7.6Kg/m2) and stable outpatient HF controls (n=10, 65±13 yrs, m=90%, BMI= 29.5±5.2Kg/m2). All four groups were compared using one-way ANOVA followed by a post-hoc analysis. A correlation between lung fluid % and LVFP was performed using Spearman's correlation test. Results: When HF groups were compared according to CT % lung fluid, significant differences were found between HF groups (p=0.004). Post-hoc analysis revealed a significant difference in % lung fluid as HFrEF group had higher mean value in % lung fluid compared to HF control group (p=0.004). Similarly, ADHF group had higher mean % lung fluid compared to HF control group (p= 0.007). However, we found no correlation between LVFP and % lung fluid. The rightward shift in CT attenuation for HFpEF, HFrEF, and ADHF subjects, as displayed in figure 1, suggests greater levels of % lung water in these subjects compared to controls. Conclusion: These data suggest that CT measures of lung water differ in subgroups of HF patients and may not correlate with LVFP.

Rationale: Volatile organic compounds (VOCs) in exhaled breath change significantly after ultramarathons and could help monitor athletes’ physiological status to optimize training. While VOCs can reflect metabolic changes, the connection between VOCs and clinical blood and respiratory data remains unknown. In this study, we investigated how breath VOCs are linked to clinical variables that reflect the cardiovascular and respiratory system. Methods: Correlation analysis was performed between respiratory data collected in pre- and post-race samples from 24 runners who participated in the 2019 Ultra-Trail du Mont Blanc (UTMB®) ultra-marathon. Correlation analysis was then performed between these clinical data and previously published breath VOC data collected from the same individuals. Results: Clinical data indicated a slight decrease in runner's lung function post-race. Interestingly, in post-race samples, respiratory parameters vital capacity (VC) and forced expiratory volume in one second (FEV1) formed a moderate positive correlation with 2,3-butanediol (r = 0.53, r = 0.63, respectively), a compound produced by bacterial metabolism. We hypothesize that production of 2,3-butanediol results from the effect of exhaustive exercise on the gut microbiome, which may provide protection to ameliorate lung injury. Additionally, a strengthened correlation from moderate (r = 0.5 – 0.7) to strong (r > 0.7) between VC and FEV1 (r = 0.67 to r = 0.84), forced vital capacity (FVC) and maximal expiratory pressure (MEP) (r = 0.57 to r = 0.75), was observed from pre-race to post-race samples. Finally, FEV1 and MEP shifted from no correlation (r < 0.5) in pre-race to a strong correlation (r = 0.73) in post-race. Conclusion: The strengthened correlation between respiratory data in post-race samples suggests that the gut microbiome, under the effect of exercise, may have an indirect impact on both lung function and respiratory muscle function changes. Our findings support the notion that there is an intricate relationship between exhaustive exercise, altered gut microbiome activity, and lung function, and together they can influence athlete performance.

This case study investigated the impact of SCS on alterations in blood pressure during constant-load exercise in a female patient with heart failure. Three different SCS frequencies [No SCS (~0 Hz), Low SCS (~100 Hz), and High SCS (~1000 Hz)] with and without ischaemic stimulation of the legs (cuffs) were randomly applied during constant-load exercise. To determine cardiovascular and ventilatory responses to exercise following SCS frequencies, BP, heart rate (HR), and respiratory gas exchange were measured. This experiment was duplicated in visit 1 and visit 2 with a random application of SCS frequency order and the data were averaged. There were no significant differences among three frequencies with no leg ischaemia. However, High SCS demonstrated lower BP, HR, and respiratory gas exchange relative to No SCS and Low SCS. SCS may be effective in improving cardiovascular and ventilatory responses in HF and high-frequency stimulation provides more clinical benefit; however, further studies are needed.

Background: The forced oscillation technique (FOT) enables non-invasive measurement of respiratory system impedance. Limited data exists on how changes in operating lung volume (OLV) impact FOT-derived measures of airway resistance (Rrs) and reactance (Xrs).Objectives: This study examined the reproducibility and responsiveness of FOT-derived measures of Rrs and Xrs during simulated changes in OLV.Methods: Participants simulated breathing at six OLVs: total lung capacity (TLC), similar to 50% of inspiratory reserve volume (IRV50), similar to two-times tidal volume (VT2), tidal volume (VT), similar to 50% of expiratory reserve volume (ERV50), and residual volume (RV), on a commercially available FOT device. Each simulated OLV manuever was performed in triplicate and in random order. Total Rrs and Xrs were recorded at 5, 11, and 19 Hz.Results: Twelve healthy participants (2 female) completed the study (weight: 76.5 +/- 13.6 kg, height: 178.6 +/- 9.7 cm, body mass index: 23.9 +/- 3.1 kg/m(2)). Reproducibility of Rrs and Xrs at VT, VT2 and IRV50 was good to excellent (Range: ICC: 0.89-0.98, 95% confidence interval (CI): 0.70-0.98), while reproducibility at TLC, RV, and ERV50 was poor to excellent (Range: ICC: 0.60-0.98, 95% CI: 0.36-0.97). Rrs and Xrs were not different between VT and VT2 at any frequency (P > .05). With lung hyperinflation from VT to TLC, Rrs and Xrs decreased at all three frequencies (e.g., At 5 Hz Rrs: mean difference (MD): - 0.89, 95%CI: - 0.03 to - 1.75, P = .04; Xrs: MD: - 0.56, 95%CI: - 0.25 to - 0.86, P < .01). With lung hypoinflated from VT to RV, Rrs increased, and Xrs decreased for all frequencies (e.g., MD at 5 Hz, Rrs: MD: 2.31, 95%CI: 0.94-3.67, P < .01; Xrs: MD: -2.53, 95%CI: -4.02 to -1.04, P < .01).Conclusion: FOT-derived measures of airway Rrs and Xrs are reproducible across a range of OLV's, and are responsive to hyper- and hypo-inflation of the lung. To further understand the impact of lung hyper- and hypo-inflation on FOT-derived airway impedance additional study is required in individuals with pathological variations in operating lung volume.

Optimizing left ventricular assist device (LVAD)–patient interaction is important. This is typically accomplished via an outpatient ramp test, monitored by echocardiography and/or invasive measures. We have developed a wireless, wearable Doppler ultrasound that we hypothesized would detect relatively small (i.e., ± 5