Breathing Response Research Articles

Lateral hypothalamic astrocytes contribute to the hypercapnic chemoreflex in a light-dark cycle-dependent manner in unanesthetized rats

Brainstem astrocytes are important for CO2/H+ chemoreception. Lateral Hypothalamus/Perifornicial Area (LH/PFA) neurons have an excitatory effect on the ventilatory response to CO2, however the role of the astrocytes is unknown. We hypothesized that LH/PFA astrocytes play an excitatory role in the hypercapnic ventilatory response in a sleep-wake and light-dark cycles-dependent manner. We manipulated the activity of astrocytes in the LH/PFA of male Wistar rats through microinjection of Fluorocitrate (Fct), which selectively affects astrocytes, inducing the exocytosis of gliotransmitters. We investigated the effects of intra-LH/PFA Fct microinjection on resting breathing and ventilatory responses to hypercapnia and hypoxia during wakefulness and NREM sleep, in the light and dark phases. Fct increased ventilation during hypercapnia but not during room air or hypoxia. The hypercapnic chemoreflex was increased exclusively during the dark-active phase during both, wakefulness and NREM sleep, indicating that LH/PFA astrocytes play an excitatory role in hypercapnic ventilatory response in a light-dark cycle-dependent manner.

Developing zebrafish utilize taste-signaling pathways for oxygen chemoreception

A fundamental requirement for all animals is to sense and respond to changes in environmental O2 availability. Low O2 (hypoxia) typically stimulates breathing, a universal and critical response termed the hypoxic ventilatory response (HVR). In this study, we test the hypothesis that taste-signaling pathways are used for O2 sensing and activation of the HVR. We show that Merkel-like cells (MLCs), which are part of the taste-bud complex, function as O2 chemoreceptor cells in larval zebrafish and that transduction of the O2 signal uses taste-signaling pathways. Specifically, MLCs responded to hypoxia invivo with an increase in Ca2+ activity that can drive the HVR. In addition, MLCs transmit O2 signals to afferent cranial nerves IX and X (nIX/X), which project into the area postrema within the hindbrain and synapse with interneurons that are in contact with vagal motor neurons. Hypoxia or chemo-activation of nIX/X caused Ca2+ activity to increase within the area postrema and elicited hyperventilation. The results provide the first demonstration of an O2 signaling pathway that commences with the activation of taste receptors (MLCs) to yield a critical physiological reflex, the HVR.

Modulation of Posterior Default Mode Network Activity During Interoceptive Attention and Relation to Mindfulness

BackgroundInteroceptive attention to internal sensory signals, such as the breath, is fundamental to mindfulness. However, interoceptive attention can be difficult to study, with many studies relying on subjective and retrospective measures. Response consistency is an established method for evaluating variability of attention on exteroceptive attention tasks, but it has rarely been applied to interoceptive attention tasks. MethodsIn this study, we measured consistency of response times on a breath-monitoring task with simultaneous electroencephalography in individuals across the life span (15–91 years of age, N = 324). ResultsWe found that consistency on the breath-monitoring task was positively correlated with attentive performance on an exteroceptive inhibitory control task. Electroencephalography source reconstruction showed that on-task alpha band (8–12 Hz) activity was greater than that measured at rest. Low-consistency/longer breath responses were associated with elevated brain activity compared with high-consistency responses, particularly in posterior default mode network (pDMN) brain regions. pDMN activity was inversely linked with functional connectivity to the frontoparietal network and the cingulo-opercular network on task but not at rest, suggesting a role for these frontal networks in on-task regulation of pDMN activity. pDMN activity within the precuneus region was greater in participants who reported low subjective mindfulness and was adaptively modulated by task difficulty in an independent experiment. ConclusionsElevated pDMN alpha activity serves as an objective neural marker for low-consistency responding during interoceptive breath attention, scales with task difficulty, and is associated with low subjective mindfulness.

Quantification of breathing irregularity for the diagnosis of dysfunctional breathing using proportional tidal volume variation: a cross-sectional, retrospective real-world study

ObjectivesTo develop a statistical approach that provides a quantitative index measuring the magnitude of the irregularity of the breathing response to exercise for the diagnosis of dysfunctional breathing.DesignCross-sectional, retrospective, real-world...

Unraveling the Role of Enkephalin Signaling in Respiratory Control

Opioid-induced respiratory depression (OIRD) is the primary cause of death during opioid overdose characterized by a dramatic decrease in respiratory frequency and regularity. Opioid drugs cause neural depression in the ventral respiratory column (VRC) of the medulla via activation of mu-opioid receptors (MORs) that partially contribute to breathing cessation. Nonetheless, little is known about the role of endogenous opioid signaling in respiratory modulation. This study investigates the role of endogenous MORs ligands, enkephalins encoded by the Penk gene, in breathing control. To test whether enkephalin-expressing neurons of the preBӧtzinger Complex (preBӧtC) — the inspiratory rhythm-generating region of the VRC — are necessary for breathing rhythmogenesis, we permanently silenced the region’s Penk+ population via AAV1 injections encoding tetanus toxin light chain. Using whole-body plethysmography, we recorded the animals' respiratory performance within 14 days post-injection. During the second week of testing, we observed unexpected mortality in some experimental but not control animals; post-hoc analysis of breathing traces revealed the development of severe tachypnea in succumbed mice. These data suggest that Penk+ preBӧtC cells are integral for normal respiration. Still, these observations did not assess the specific contribution of enkephalin, as opposed to other types of signaling, to breathing stability. To directly dissect the effects of enkephalin on respiratory rhythm, we utilized optogenetics and pharmacological approaches in brainstem slice preparation from neonatal mice. Brief optogenetic activation of Penk+ neurons in the preBӧtC evoked population bursts while prolonged stimulation increased the rhythm frequency. However, the application of MOR antagonist Naloxone did not affect the network’s responses to light stimulations indicating the lack of MOR/enkephalin involvement in mediating these excitatory effects. High fidelity and temporal coordination of evoked bursts implicated glutamatergic transmission as the primary mechanism of excitation. Likewise, we were able to optogenetically drive respiratory rhythm in urethane-anesthetized spontaneously breathing adult mice by stimulating the preBӧtC. Further, there was a small but significant difference in breathing responses in the presence of Naloxone compared to control conditions. We hypothesized that longitudinal projections to the VRC that might be disrupted during slice preparation contributed enkephalin to the respiratory circuits in the whole-body preparation. We utilized recombinase-dependent reporter mice crosses and retrograde AAV tracers to identify brain-wide Penk inputs to the preBӧtC. Using conventional and light sheet fluorescence microscopy, we located regions in the pons, midbrain, and forebrain that send direct enkephalinergic projections to the VRC. Functional characterizations of these projections will potentially uncover state-dependent mechanisms of respiratory modulation via endogenous opioids. Untimely, this study will help elucidate the role of enkephalin signaling in breathing control and may establish therapeutic targets for preventing OIRD. R01HL166317, R00HL145004. 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.

Dissecting the interaction of pain and respiration at the level of the rostral ventromedial medulla via cell-type specific manipulations

Opioid drugs are highly effective for pain management, but they also cause respiratory depression. This life-threatening side-effect of opioid use occurs due to the interacting and/or overlapping neuronal circuits that regulate pain and breathing. Understanding the brain regions and cell-types that link pain and breathing will be essential to develop safer pain management strategies. Opioid analgesia involves altered firing patterns of neurons within the rostral ventromedial medulla (RVM). Although the RVM is known for its role in descending pain modulation, local administration of opioids within the RVM induces potent respiratory depression in addition to analgesia. The RVM has two main classes of neurons identified based on their firing response to pain stimuli. As their name suggests, “ON-cells” are activated during pain and “OFF-cells” are inhibited. Pharmacological and electrophysiological studies have shown that ON-cells express the μ-opioid receptor (MOR) and respond directly to opioids. Moreover, it is thought that the activity of ON-cells facilitates pain and respiration, and that opioid suppression of ON-cells contributes to respiratory depression. In contrast, OFF-cells do not appear to express MOR; however, activation of these neurons is required for opioid-induced analgesia. Therefore, changes in OFF-cells activity may more selectively affect pain thresholds. Due to a lack of selective pharmacological agents, directly testing these predictions has not been possible. Moreover, ON-cells can be excitatory or inhibitory, whereas OFF-cells are mostly inhibitory, adding another layer of complexity to their proposed functions. Here, we dissect these RVM subpopulations using modern intersectional genetic approaches to selectively manipulate RVM neurons based on expression of Oprm1 (the gene encoding MOR), as well as genetic markers for excitatory (Vglut2) or inhibitory (Vgat) neurotransmitter phenotypes. To examine the functional effects of Oprm1+ RVM neurons, an AAV designed to express Cre-dependent ChR2 was injected into the RVM of Oprm1Cre mice, followed by the implantation of an optical fiber. Respiratory activity of awake mice was then recorded using plethysmography during optogenetic stimulation of Oprm1+ RVM neurons. Consistent with the expected effects of ON-cells, breathing rate was increased to 5-6 Hz for the duration of the stimulation, and mice exhibited flinching and freezing behavior at light onset. In a second set of experiments, double transgenic Oprm1Cre; Vglut2FlpO mice were injected with an AAV that expresses ChR2 only when FlpO is present but Cre is absent (i.e. FlpO NOT Cre). Using this strategy, we were able to selectively target excitatory RVM neurons that do not express MOR. Optogenetic stimulations of these neurons during plethysmography revealed no changes in breathing or notable behavioral responses. However, paw withdrawal thresholds tested using Hargreaves’ method suggest that optogenetic activation of these neurons increases pain sensitivity. Our ongoing work will expand on these preliminary findings by using this approach to specifically manipulate Oprm1+;Vglut2+, Oprm1+;Vgat+, and Oprm1-;Vgat+ neurons to assess the roles of these RVM subpopulations in the regulation of pain and breathing. (NAB) R00HL145004; R01HL166317 (RSP) K01DA058543. 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.

The effect of epilepsy and antiseizure medications on cardiac autonomic functions in children with epilepsy

ABSTRACT Background Autonomic manifestations have been frequently studied in adults with epilepsy. Here, we evaluated cardiac autonomic (ANS) functions in children with epilepsy in the interictal period and determined the risks for their dysfunctions. Research design and methods This study included 60 patients (boys = 25; girls = 35 age: 14.53 ± 2.54 yrs) and 25 controls. Patients were well-controlled on antiseizure medications (ASMs). The battery of testing included measuring resting heart rate (HR) and blood pressure (BP), 30:15 ratio, HR variability (HRV) response to deep breathing, Valsalva ratio and BP changes in response to standing, isometric exercise and cold. Results Dizziness was reported in 25%. Autonomic dysfunctions were found in 45% (n = 27). Manifestations included high frequencies of abnormal 30:15 ratio (22%), HRV responses to deep breathing (45%), Valsalava ratio (45%), and BP responses to standing (35%), isometric exercise (27%) and cold (27%), indicating parasympathetic and sympathetic hypofunctions. There were positive correlations between parasympathetic and sympathetic dysfunctions. Logistic analysis showed that the durations of epilepsy and ASMs therapy were associated with ANS dysfunctions [95% CI: 0.895–4.719, p = 0.004]. Conclusions Parasympathetic and sympathetic autonomic hypofunctions are common in children with epilepsy. This could be due to the depressant effect of sodium channel blocker ASMs on central and/or cardiac autonomic systems.

Interaction between Kölliker-Fuse/A7 and the parafacial respiratory region on the control of respiratory regulation

Respiration is regulated by various types of neurons located in the pontine-medullary regions. The Kölliker-Fuse (KF)/A7 noradrenergic neurons play a role in modulating the inspiratory cycle by influencing the respiratory output. These neurons are interconnected and may also project to brainstem and spinal cord, potentially involved in regulating the post-inspiratory phase. In the present study, we hypothesize that the parafacial (pF) neurons, in conjunction with adrenergic mechanisms originating from the KF/A7 region, may provide the neurophysiological basis for breathing modulation. We conducted experiments using urethane-anesthetized, vagotomized, and artificially ventilated male Wistar rats. Injection of L-glutamate into the KF/A7 region resulted in inhibition of inspiratory activity, and a prolonged and high-amplitude genioglossal activity (GGEMG). Blockade of the α1 adrenergic receptors (α1-AR) or the ionotropic glutamatergic receptors in the pF region decrease the activity of the GGEMG without affecting inspiratory cessation. In contrast, blockade of α2-AR in the pF region extended the duration of GG activity. Notably, the inspiratory and GGEMG activities induced by KF/A7 stimulation were completely blocked by bilateral blockade of glutamatergic receptors in the Bötzinger complex (BötC). While our study found a limited role for α1 and α2 adrenergic receptors at the pF level in modulating the breathing response to KF/A7 stimulation, it became evident that BötC neurons are responsible for the respiratory effects induced by KF/A7 stimulation.

Aesthetic and physiological effects of naturalistic multimodal music listening

Compared to audio only (AO) conditions, audiovisual (AV) information can enhance the aesthetic experience of a music performance. However, such beneficial multimodal effects have yet to be studied in naturalistic music performance settings. Further, peripheral physiological correlates of aesthetic experiences are not well-understood. Here, participants were invited to a concert hall for piano performances of Bach, Messiaen, and Beethoven, which were presented in two conditions: AV and AO. They rated their aesthetic experience (AE) after each piece (Experiment 1 and 2), while peripheral signals (cardiorespiratory measures, skin conductance, and facial muscle activity) were continuously measured (Experiment 2). Factor scores of AE were significantly higher in the AV condition in both experiments. LF/HF ratio, a heart rhythm that represents activation of the sympathetic nervous system, was higher in the AO condition, suggesting increased arousal, likely caused by less predictable sound onsets in the AO condition. We present partial evidence that breathing was faster and facial muscle activity was higher in the AV condition, suggesting that observing a performer's movements likely enhances motor mimicry in these more voluntary peripheral measures. Further, zygomaticus (‘smiling’) muscle activity was a significant predictor of AE. Thus, we suggest physiological measures are related to AE, but at different levels: the more involuntary measures (i.e., heart rhythms) may reflect more sensory aspects, while the more voluntary measures (i.e., muscular control of breathing and facial responses) may reflect the liking aspect of an AE. In summary, we replicate and extend previous findings that AV information enhances AE in a naturalistic music performance setting. We further show that a combination of self-report and peripheral measures benefit a meaningful assessment of AE in naturalistic music performance settings.

Hypoxia sensing requires H2S-dependent persulfidation of olfactory receptor 78.

Oxygen (O2) sensing by the carotid body is critical for maintaining cardiorespiratory homeostasis during hypoxia. Hydrogen sulfide (H2S) signaling is implicated in carotid body activation by low O2. Here, we show that persulfidation of olfactory receptor 78 (Olfr78) by H2S is an integral component of carotid body activation by hypoxia. Hypoxia and H2S increased persulfidation in carotid body glomus cells and persulfidated cysteine240 in Olfr78 protein in heterologous system. Olfr78 mutants manifest impaired carotid body sensory nerve, glomus cell, and breathing responses to H2S and hypoxia. Glomus cells are positive for GOlf, adenylate cyclase 3 (Adcy3) and cyclic nucleotide-gated channel alpha 2 (Cnga2), key molecules of odorant receptor signaling. Adcy3 or Cnga2 mutants exhibited impaired carotid body and glomus cell responses to H2S and breathing responses to hypoxia. These results suggest that H2S through redox modification of Olfr78 participates in carotid body activation by hypoxia to regulate breathing.

An Effective Resistive-Type Alcohol Vapor Sensor Using One-Step Facile Nanoporous Anodic Alumina.

With the increases in work environment regulations restricting alcohol to 1000 ppm, and in drink-driving laws, testing for alcohol with a simple method is a crucial issue. Conventional alcohol sensors based on sulfide, metal oxide, boron nitride or graphene oxide have a detection limit in the range of 50-1000 ppm but have disadvantages of complicated manufacture and longer processing times. A recent portable alcohol meter based on semiconductor material using conductivity or chemistry measurements still has the problem of a complex and lengthy manufacturing process. In this paper, a simple and effective resistive-type alcohol vapor sensor using one-step anodic aluminum oxide (AAO) is proposed. The nanoporous AAO was produced in one-step by anodizing low-purity AA1050 at room temperature of 25 °C, which overcame the traditional high-cost and lengthy process at low temperature of anodization and etching from high-purity aluminum. The highly specific surface area of AAO has benefits for good sensing performance, especially as a humidity or alcohol vapor sensor. With the resistance measurement method, alcohol vapor concentration of 0, 100, 300, 500, 700 and 1000 ppm correspond to mean resistances of 8524 Ω, 8672 Ω, 9121 Ω, 9568 Ω, 10,243 Ω, and 11,045 Ω, respectively, in a linear relationship. Compared with other materials for detecting alcohol vapor, the AAO resistive sensor has advantages of fast and simple manufacturing with good detection limits for practical applications. The resistive-type alcohol vapor-sensing mechanism is described with respect to the resistivity of the test substance and the pore morphology of AAO. In a human breath test, the AAO sensor can quickly distinguish whether the subject is drinking, with normal breath response of -30% to -40% and -20% to -30% response after drinking 50 mL of wine of 25% alcohol.

L-DOPA Improves Ventilation but Not the Ventilatory Response to Hypercapnia in a Reserpine Model of Parkinson's Disease.

Parkinson's disease (PD) is a neurological disorder characterized by progressive degeneration of the substantia nigra that affects mainly movement control. However, pathological changes associated with the development of PD may also alter respiration and can lead to chronic episodes of hypoxia and hypercapnia. The mechanism behind impaired ventilation in PD is unclear. Therefore, in this study, we explore the hypercapnic ventilatory response in a reproducible reserpine-induced (RES) model of PD and parkinsonism. We also investigated how dopamine supplementation with L-DOPA, a classic drug used to treat PD, would affect the breathing and respiratory response to hypercapnia. Reserpine treatment resulted in decreased normocapnic ventilation and behavioral changes manifested as low physical activity and exploratory behavior. The respiratory rate and the minute ventilation response to hypercapnia were significantly higher in sham rats compared to the RES group, while the tidal volume response was lower. All of this appears to be due to reduced baseline ventilation values produced by reserpine. L-DOPA reversed reduced ventilation, indicating a stimulatory effect of DA on breathing, and showed the potency of DA supplementation in restoring normal respiratory activity.

Organ- and function-specific anatomical organization of vagal fibers supports fascicular vagus nerve stimulation

Vagal fibers travel inside fascicles and form branches to innervate organs and regulate organ functions. Existing vagus nerve stimulation (VNS) therapies activate vagal fibers non-selectively, often resulting in reduced efficacy and side effects from non-targeted organs. The transverse and longitudinal arrangement of fibers inside the vagal trunk with respect to the functions they mediate and organs they innervate is unknown, however it is crucial for selective VNS. Using micro-computed tomography imaging, we tracked fascicular trajectories and found that, in swine, sensory and motor fascicles are spatially separated cephalad, close to the nodose ganglion, and merge caudad, towards the lower cervical and upper thoracic region; larynx-, heart- and lung-specific fascicles are separated caudad and progressively merge cephalad. Using quantified immunohistochemistry at single fiber level, we identified and characterized all vagal fibers and found that fibers of different morphological types are differentially distributed in fascicles: myelinated afferents and efferents occupy separate fascicles, myelinated and unmyelinated efferents also occupy separate fascicles, and small unmyelinated afferents are widely distributed within most fascicles. We developed a multi-contact cuff electrode to accommodate the fascicular structure of the vagal trunk and used it to deliver fascicle-selective cervical VNS in anesthetized and awake swine. Compound action potentials from distinct fiber types, and physiological responses from different organs, including laryngeal muscle, cough, breathing, and heart rate responses are elicited in a radially asymmetric manner, with consistent angular separations that agree with the documented fascicular organization. These results indicate that fibers in the trunk of the vagus nerve are anatomically organized according to functions they mediate and organs they innervate and can be asymmetrically activated by fascicular cervical VNS.

Paced breathing and respiratory movement responses evoked by bidirectional constant current stimulation in anesthetized rabbits.

Objective: Diaphragm pacing (DP) is a long-term and effective respiratory assist therapy for patients with central alveolar hypoventilation and high cervical spinal cord injury. The existing DP system has some limitations, especially high price, inconvenience preoperative evaluation methods and diaphragm fatigue easily. Our objective was to develop a DP system and evaluated reliability through hardware testing and animal experiments. Methods: A DP system with bidirectional constant current was designed, manufactured and tested. Effects of a wide range of stimulus amplitudes (range: .5-2.5mA) and frequencies (range: 10-250Hz) on airflow and corresponding inspired volume were investigated during DP. Differences in airflow characteristics under various stimulation parameters were evaluated using power function. ECG interference in diaphragm electromyography (EMGdi) was filtered out using stationary wavelet transform to obtain pure EMGdi (EMGdip). 80-min period with a tendency for diaphragm fatigue by root mean square (RMS) and centroid frequency (f c ) of EMGdip was studied. Results: The increase of stimulus frequency and amplitude in animals resulted in different degrees of increase in envoked volume. Significant difference in Airflow Index (b) between anesthesia and DP provided a simple, non-invasive and feasible solution for phrenic nerve conduction function test. Increased stimulation duration with the developed DP system caused less diaphragm fatigue. Conclusion: A modular, inexpensive and reliable DP was successfully developed. Its effectiveness was confirmed in animal experiments. Significance: This study is useful for design of future implantable diaphragmatic pacemakers for improving diaphragm fatigue and convenient assessment of respiratory activity in experiments.

Reply to Kenney.

Reply to Kenney.

Associations between risk of Alzheimer's disease and obstructive sleep apnea, intermittent hypoxia, and arousal responses: A pilot study.

Obstructive sleep apnea (OSA) may increase the risk of Alzheimer's disease (AD). However, potential associations among sleep-disordered breathing, hypoxia, and OSA-induced arousal responses should be investigated. This study determined differences in sleep parameters and investigated the relationship between such parameters and the risk of AD. Patients with suspected OSA were recruited and underwent in-lab polysomnography (PSG). Subsequently, blood samples were collected from participants. Patients' plasma levels of total tau (T-Tau) and amyloid beta-peptide 42 (Aβ42) were measured using an ultrasensitive immunomagnetic reduction assay. Next, the participants were categorized into low- and high-risk groups on the basis of the computed product (Aβ42 × T-Tau, the cutoff for AD risk). PSG parameters were analyzed and compared. We included 36 patients in this study, of whom 18 and 18 were assigned to the low- and high-risk groups, respectively. The average apnea-hypopnea index (AHI), apnea, hypopnea index [during rapid eye movement (REM) and non-REM (NREM) sleep], and oxygen desaturation index (≥3%, ODI-3%) values of the high-risk group were significantly higher than those of the low-risk group. Similarly, the mean arousal index and respiratory arousal index (R-ArI) of the high-risk group were significantly higher than those of the low-risk group. Sleep-disordered breathing indices, oxygen desaturation, and arousal responses were significantly associated with an increased risk of AD. Positive associations were observed among the AHI, ODI-3%, R-ArI, and computed product. Recurrent sleep-disordered breathing, intermittent hypoxia, and arousal responses, including those occurring during the NREM stage, were associated with AD risk. However, a longitudinal study should be conducted to investigate the causal relationships among these factors.

Характеристика стійкого стану функцій спортсменів у видах спорту з варіативними умовами змагальної діяльності

The purpose of the study was to develop generalized and specific characteristics of the steady state of the highly qualified athletes, who specialize in the standard program of sports dance and boxing. Materials and methods. Twenty sportsmen-dancers and twenty boxers of high qualification took part in the research. Gas analysis. Measurements of О2 consumption reaction, СО2 emissions, minute volume of breathing were carried out using the MetaMax 3B analyzer. Ergometry. Modeling of standard conditions of measurement was carried out on the basis of bicycle ergometer Monark. Standard conditions are associated with the use of a given ergometric load power of 50 W. The composition of Cardiorespiratory Intermittent endurance test included eight accelerated 10-second intervals, eight 20-second rest intervals. The duration of the task is four minutes. Mathematic statistics. Descriptive statistics suggested determining the arithmetic mean – x ̅, standard deviation – S, as well as median – Me, maximum (max) and minimum (min) indices, 25% and 75% indices. Steady state is a period of competitive activity, in the process of which sportsmen demonstrate high level of technical and tactical skills and physical performance. Steady state diagnostics is an essential reserve for managing the functional support of special performance of athletes in sports with variable conditions of competitive activity. Results and discussion. An increase in the response of pulmonary ventilation indicates its role as a response to respiratory compensation of metabolic acidosis. Differences in the breathing response in standard measurement conditions are related to the specificity of the breathing response of athletes-dancers. To some extent, “artificial” management of the breathing response causes a decrease in the intensity of breathing cycles. Empirical knowledge indicates that this refers to the “aesthetic” component of the judges' assessment of the performance of the sports dance program. To some extent, this is related to the specifics of the formation of programs of special physical training, correction of certain structural components of functional maintenance of working capacity, in this case, the respiratory system. Another obvious fact is related to the structure of the load, when the intensity of the work of boxers causes more significant acidemic shifts and, as a result, predicts an increase in the reaction of pulmonary ventilation as a mechanism for removing excess CO2 during work. The increase (maintenance) of the O2 consumption response of athletes-dancers is associated with the formation of excess CO2 within the RER – 1.03–1.05 and excessive pulmonary ventilation in the range of 37.2–39.1. Boxers, respectively, with the formation of excess CO2 within the limits of RER – 1.07–1.09 and excessive pulmonary ventilation in the range of 40.0–44.1. The increase in excess ventilation in the third-fifth of dancers was 4.9%, 9.9% – in boxers, provided that the O2 consumption reaction remained stable. Conclusion. The steady state of the functional support of the special performance of athletes in sports with variable conditions of competitive activity ensures the stable development of cardio-respiratory system and aerobic energy supply in the middle of intense motor activity

Respiratory function and breathing response to water‐ and land‐based cycling at the matched oxygen uptake

The impact of underwater exercise on respiratory function remains unclear when its metabolic rate is matched with exercise performed on land. Therefore, we compared the breathing responses and respiratory function during and after water (WC)‐ and land (LC)‐based cycling performed at the matched oxygen uptake (VO2). Twelve healthy men performed 15 min of incremental WC and LC on separate days. During WC, participants cycled continuously at 30, 45, and 60 rpm (stages 1, 2, and 3) for 5 min each. During LC, participants cycled at 60 rpm for 15 min while wattage was increased every 5 min and adjusted to match VO2 to the WC condition. Breathing patterns during cycling and spirometry data before and after cycling were collected. VO2 during WC and LC was similar. Respiratory rate (WC: 27 ± 3 vs. LC: 23 ± 4 bpm, p = 0.012) and inspiratory flow (WC: 1233 ± 173 vs. LC: 1133 ± 200 ml/s, p = 0.035) were higher and inspiratory time (WC: 1.0 ± 0.1 vs. LC: 1.2 ± 0.2 s, p = 0.025) was shorter at stage 3 during WC than LC. After WC, forced vital capacity (p = 0.010) significantly decreased while no change was observed after LC. These results suggest that at similar metabolic rates during WC and LC, breathing is slightly shallower during WC which may have chronic effects on respiratory muscle function after multiple bouts of aquatic cycling. Underwater exercise may be beneficial for respiratory muscle rehabilitation when performed on a chronic basis.

Influence of exercise intensity and hypoxic exposure on physiological, perceptual and biomechanical responses to treadmill running

ABSTRACT Acute physiological, perceptual and biomechanical consequences of manipulating both exercise intensity and hypoxic exposure during treadmill running were determined. On separate days, eleven trained individuals ran for 45 s (separated by 135 s of rest) on an instrumented treadmill at seven running speeds (8, 10, 12, 14, 16, 18 and 20 km.h−1) in normoxia (NM, FiO2 = 20.9%), moderate hypoxia (MH, FiO2 = 16.1%), high hypoxia (HH, FiO2 = 14.1%) and severe hypoxia (SH, FiO2 = 13.0%). Running mechanics were collected over 20 consecutive steps (i.e. after running ∼25 s), with concurrent assessment of physiological (heart rate and arterial oxygen saturation) and perceptual (overall perceived discomfort, difficulty breathing and leg discomfort) responses. Two-way repeated-measures ANOVA (seven speeds × four conditions) were used. There was a speed × condition interaction for heart rate (p = 0.045, ηp2 = 0.22), with lower values in NM, MH and HH compared to SH at 8 km.h−1 (125 ± 12, 125 ± 11, 128 ± 12 vs 132 ± 10 b.min−1). Overall perceived discomfort (8 and 16 km.h−1; p = 0.019 and p = 0.007, ηp2 = 0.21, respectively) and perceived difficulty breathing (all speeds; p = 0.023, ηp2 = 0.37) were greater in SH compared to MH, whereas leg discomfort was not influenced by hypoxic exposure. Minimal difference was observed in the twelve kinetics/kinematics variables with hypoxia (p > 0.122; ηp 2 = 0.19). Running at slower speeds in combination with severe hypoxia elevates physiological and perceptual responses without a corresponding increase in ground reaction forces. Highlights The extent to which manipulating hypoxia severity (between normoxia and severe hypoxia) and running speed (from 8 to 20 km.h−1) influence acute physiological and perceptual responses, as well as kinetic and kinematic adjustments during treadmill running was determined. Running at slower speeds in combination with severe hypoxia elevates heart rate, while this effect was not apparent at faster speeds. Arterial oxygen saturation was increasingly lower as running speed and hypoxic severity increased. Overall perceived discomfort (8 and 16 km.h−1) and perceived difficulty breathing (all speeds) were lower in moderate hypoxia than in severe hypoxia, whereas leg discomfort remained unchanged with hypoxic exposure.

Breath response following a nutritional challenge monitored by secondary electrospray ionization high-resolution mass spectrometry

On-line breath analysis using secondary electrospray ionization coupled to high-resolution mass spectrometry (SESI-HRMS) is a sensitive method for biomarker discovery. The strengths of this technology have already been demonstrated in the clinical environment. For the first time, this study demonstrates the application of SESI-HRMS in the field of nutritional science using a standardized nutritional intervention, consisting of a high-energy shake (950 kcal, 8% protein, 35% sugar and 57% fat). Eleven subjects underwent the intervention on three separate days and their exhaled breath was monitored up to six hours postprandially. In addition, sampling was performed during equivalent fasting conditions for selected subjects. To estimate the impact of inter- and intra-individual variability, analysis of variance simultaneous component analysis was conducted, revealing that the inter-individual variability accounted for 30% of the data variation. To distinguish the effect of the intervention from fasting conditions, partial least squares discriminant analysis was performed. Candidate compound annotation was performed with pathway analysis and collision-induced dissociation (CID) experiments. Pathway analysis highlighted, among others, features associated with the metabolism of linoleate, butanoate and amino sugars. Tentative compounds annotated through CID measurements include fatty acids, amino acids, and amino acid derivatives, some of them likely derived from nutrients by the gut microbiome (e.g. propanoate, indoles), as well as organic acids from the Krebs cycle. Time-series clustering showed an overlap of observed kinetic trends with those reported previously in blood plasma.