Kim, Chul‐Ho

Abstract Brief inhalation of carbon dioxide (CO 2 ) has been proposed to counteract transient hypocapnia by enhancing oxygen unloading, vasodilation, and sympathetic modulation. Despite these potential ergogenic mechanisms, CO 2 has rarely been investigated in the exercise context. The present study investigated whether brief CO 2 inhalation (iCO 2 ) 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% CO 2 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 iCO 2 . During the first interval, iCO 2 increased exercise duration and VO 2 . At matched exercise time, perceived exertion and dyspnea were lower with iCO 2 . During recovery, systolic blood pressure was lower and heart rate was higher following iCO 2 . Brief iCO 2 improved first‐interval performance, altered cardiovascular recovery, and reduced perceptual strain but did not extend overall exercise duration. These findings suggest iCO 2 may transiently modulate tolerance and autonomic‐vascular responses during high‐intensity interval exercise.

Background: Exhaled volatile organic compounds (VOCs) can provide insight into various physiological and metabolic processes. Aim: The purpose of this study was to determine if exhaled VOCs would differ across disease severity in heart failure (HF) patients. Methods: We recruited 62 individuals who were classified as healthy control (CTL), admissions with fluid overload (DHF), NYHA class I-II or NYHA class II-III. Breath samples were collected using the ReCIVA Breath Sampler (Owlstone Medical Ltd) and analyzed using mass spectrometry and gas chromatography. Typical clinical characteristics were documented at the time of exhaled breath collection. Results: Data were obtained on 16 CTL, 21 DHF, 15 NYHA I-II and 10 NYHA II-III (characteristics shown in Table). For the HF groups, DHF, NYHA I-II and NYHA II-III, the %HPEFF were 32, 63 and 63% respectively. Regarding exhaled VOCs, we observed a stepwise increase in VOCs potentially linked to lipid peroxidation or fatty acid metabolism, such as pent-3-en-2-one, 2-pentanone, and 4-heptanone, as disease severity worsened. A similar trend was seen for sulphur containing compounds (methyl propyl sulfide, allyl methyl sulfide and 1(methyl thiol)-1 propene)), potentially providing insight into impaired hepatic or renal clearance in more advanced HF. The level of methyl pyruvate on breath also rose with increasing disease severity, which may reflect altered energy metabolism. Finally, gut microbiome-related VOCs (acetoin, 2,3-butanediol, and butyric anhydride) increased across severity groups, potentially reflecting dysbiosis in advanced disease. Conclusions: In a small pilot study aiming to identify potential exhaled breath biomarkers in HF, we observed significant differences in VOCs across disease severity. These compounds have been linked to lipid peroxidation, energy metabolism, liver and kidney function as well as microbial fermentation and short-chain fatty acid metabolism. Collectively, these data demonstrate the ability of breath omics to potentially stratify disease severity and provide additional biological insights into HF pathophysiology. Larger studies are needed to determine whether a breath biomarker panel could be established to quantify disease severity and predict decompensation risk in HF.

Abstract 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.

A wireless, wearable Doppler ultrasound offers a new paradigm for linking physiology to resuscitation medicine. To this end, the image analysis of simultaneously-acquired venous and arterial Doppler spectrograms attained by wearable ultrasound represents a new source of hemodynamic data. Previous investigators have reported a direct relationship between the central venous pressure (CVP) and the ratio of the internal jugular-to-common carotid artery diameters. Because Doppler power is directly related to the number of red cell scatterers within a vessel, we hypothesized that (1) the ratio of internal jugular-to-carotid artery Doppler power (V/APOWER) would be a surrogate for the ratio of the vascular areas of these two vessels and (2) the V/APOWER would track the anticipated CVP change during simulated hemorrhage and resuscitation. To illustrate this proof-of-principle, we compared the change in V/APOWER obtained via a wireless, wearable Doppler ultrasound to B-mode ultrasound images during a head-down tilt. Additionally, we elucidated the change in the V/APOWER during simulated hemorrhage and transfusion via lower body negative pressure (LBNP) and release. With these Interesting Images, we show that the Doppler V/APOWER ratio qualitatively tracks anticipated changes in CVP (e.g., cardiac preload) which is promising for both diagnosis and management of hemodynamic unrest.

This study investigated the combined effect of handgrip strength (HGS) and non-alcoholic fatty liver disease (NAFLD) on pulmonary function using the Korea National Health and Nutrition Examination Survey (KNHANES) from 2016 to 2018. For the present study, forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), the FEV1/FVC ratio, handgrip strength (HGS) and the hepatic steatosis index (HSI) to estimate NAFLD were obtained from nationwide cross-sectional surveys. For HGS, subjects were divided into higher HGS (upper 50%) and lower HGS (lower 50%). For NAFLD, subjects were divided into the NAFLD cohort (HSI > 36) and the normal cohort (HSI ≤ 36). Of 1651 subjects (men, n = 601), 25.5% of subjects (n = 421) met the HSI > 36. Based on the normal cohort with high HGS, the normal cohort with low HGS showed an increased risk of reduced FVC (OR = 3.062, 95% CI = 2.46–4.83, p < 0.001) and the NAFLD cohort with low HGS showed a further increased risk of reduced FVC (OR = 4.489, 95% CI = 3.43–7.09, p < 0.001). However, the risk of reduced FVC was not significantly increased in NAFLD with high HGS (OR = 1.297, 95% CI = 0.67–2.50, p = 0.436). After adjusted for covariates such as age, sex, smoking, FBG, HDL-C, TG, SBP, DBP, CRP and alcohol consumption, the results remained similar. More importantly, these results were consistent in the obesity-stratified analysis. The current findings of the study suggest that higher muscle strength is associated with a lower risk of reduced pulmonary function in individuals with NAFLD.

BACKGROUND: Methacholine bronchoprovocation or challenge testing (MCT) is commonly performed to assess airway hyper-responsiveness in the setting of suspected asthma. Nebulization is an aerosol-generating procedure, but little is known about the risks of MCT in the context of the ongoing coronavirus disease 2019 (COVID-19) pandemic. We aimed to quantify and characterize aerosol generation during MCT by using different delivery methods and to assess the impact of adding a viral filter. METHODS: Seven healthy subjects performed simulated MCT in a near particle-free laboratory space with 4 different nebulizers and with a dosimeter. Two devices continuously sampled the ambient air during the procedure, which detected ultrafine particles, from 0.02–1 μm, and particles of sizes 0.3, 0.5, 1.0, 2.0, 5.0, and 10 µm, respectively. Particle generation was compared among all the devices, with and without viral filter placement. RESULTS: Ultrafine-particle generation during simulated MCT was significant across all the devices. Ultrafine-particle (0.02–1 μm) concentrations decreased 77%–91% with the addition of a viral filter and varied significantly between unfiltered (P < .001) and filtered devices (P < .001). Ultrafine-particle generation was lowest when using the dosimeter with filtered Hudson nebulizer (1,258 ± 1,644 particle/mL). Ultrafine-particle concentrations with the filtered nebulizer devices using a compressor were higher than particle concentrations detected when using the dosimeter: Monaghan (3,472 ± 1,794 particles/mL), PARI (4,403 ± 2,948), Hudson (6,320 ± 1,787) and AirLife (9,523 ± 5,098). CONCLUSIONS: The high particle concentrations generated during MCT pose significant infection control concerns during the COVID-19 pandemic. Particle generation during MCT was significantly reduced by using breath-actuated delivery and a viral filter, which offers an effective mitigation strategy.

Introduction Optivol (Medtronic Inc.) thoracic impedance (ZT) provides preemptive disease status information in heart failure (HF). It remains unclear how pulmonary‐capillary blood volume (Vc), lung volume (Lvol), and interstitial fluid influence ZT. Hypothesis Positional change and exercise result in increased Vc and/or lung interstitial fluid and ZT tracks fluctuation in these variables. Methods 12 HF patients (age 63±8yr, LVEF 41±14%) were recruited. Measures were taken at rest, exercise, recovery. This included: spirometry, ZT, diffusing capacity of the lungs for CO and NO (DLCO, DLNO), alveolar‐capillary conductance (Dm, interstitial fluid index), and Vc. Inspiratory capacity was obtained to provide consistent lung volumes for assessing ZT. Results Positional change (upright‐supine) resulted in an increased ZT (5±4%, p<0.01), while the change in Lvol (RV‐TLC) resulted in a 7±2 ohm swing in ZT (0.2±0.1ohm change/100ml change in Lvol). After 30min supine, Vc increased 28±39% (p<0.05) while Dm/Vc and Lvol decreased (29±11% and 17±3%, p<0.05). During exercise compared to baseline, Vc increased 56±44% (p<0.01), DmCO/Vc decreased 25±7% (p<0.05), and ZT did not change. During recovery measures normalized except DmCO/Vc. Conclusion Positional changes and fluctuations in Lvol influence ZT yet measures of lung fluid minimally impact this measure despite significant fluctuations.