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Identification of the breathing cycle forms the basis of any breath-by-breath gas exchange analysis. Classically, the breathing cycle is defined as the time interval between the beginning of two consecutive inspiration phases. Based on this definition, several research groups have developed algorithms designed to estimate the volume and rate of gas transferred across the alveolar membrane ("alveolar gas exchange"); however, most algorithms require measurement of lung volume at the beginning of the ith breath (VLi-1; i.e., the end-expiratory lung volume of the preceding ith breath). The main limitation of these algorithms is that direct measurement of VLi-1 is challenging and often unavailable. Two solutions avoid the requirement to measure VLi-1 by redefining the breathing cycle. One method defines the breathing cycle as the time between two equal fractional concentrations of lung expired oxygen (Fo2) (or carbon dioxide; Fco2), typically in the alveolar phase, whereas the other uses the time between equal values of the Fo2/Fn2 (or Fco2/Fn2) ratios [i.e., the ratio of fractional concentrations of lung expired O2 (or CO2) and nitrogen (N2)]. Thus, these methods identify the breathing cycle by analyzing the gas fraction traces rather than the gas flow signal. In this review, we define the traditional approach and two alternative definitions of the human breathing cycle and present the rationale for redefining this term. We also explore the strengths and limitations of the available approaches and provide implications for future studies.

In the mouse olfactory system, odor information is converted to a topographic map of activated glomeruli in the olfactory bulb (OB). Although the arrangement of glomeruli is genetically determined, the glomerular structure is plastic and can be modified by environmental stimuli. If the pups are exposed to a particular odorant, responding glomeruli become larger recruiting the dendrites of connecting projection neurons and interneurons. This imprinting not only increases the sensitivity to the exposed odor, but also imposes the positive quality on imprinted memory. External odor information represented as an odor map in the OB is transmitted to the olfactory cortex (OC) and amygdala for decision making to elicit emotional and behavioral outputs using two distinct neural pathways, innate and learned. Innate olfactory circuits start to work right after birth, whereas learned circuits become functional later on. In this paper, the recent progress will be summarized in the study of olfactory circuit formation and odor perception in mice. We will also propose new hypotheses on the timing and gating of olfactory circuit activity in relation to the respiration cycle. [ABSTRACT FROM AUTHOR]

Brain-Computer Interfaces (BCIs) are devices designed for establishing communication between the central nervous system and a computer. The communication can occur through different sensory modalities, and most commonly visual and auditory modalities are used. Here we propose that BCIs can be expanded by the incorporation of olfaction and discuss the potential applications of such olfactory BCIs. To substantiate this idea, we present results from two olfactory tasks: one that required attentive perception of odors without any overt report, and the second one where participants discriminated consecutively presented odors. In these experiments, EEG recordings were conducted in healthy participants while they performed the tasks guided by computer-generated verbal instructions. We emphasize the importance of relating EEG modulations to the breath cycle to improve the performance of an olfactory-based BCI. Furthermore, theta-activity could be used for olfactory-BCI decoding. In our experiments, we observed modulations of theta activity over the frontal EEG leads approximately 2 s after the inhalation of an odor. Overall, frontal theta rhythms and other types of EEG activity could be incorporated in the olfactory-based BCIs which utilize odors either as inputs or outputs. These BCIs could improve olfactory training required for conditions like anosmia and hyposmia, and mild cognitive impairment. [ABSTRACT FROM AUTHOR]

External respiration consists of relatively independent cycles. During each breath cycle the respiratory center makes a decision about how to meet the respiratory necessity of the body. The infl uence of previous respiratory cycles for the next leads to the formation of the breath cycles continuum.The method was developed for analysis of unevenness of respiratory rhythm, which takes into account the relative independence of each breathing cycle and the impact of previous respiratory cycles later. It was found that the unevenness of respiratory rhythm refl ects the degree of emotional stress and is not associated with the physical strain of the organism. The uneven rhythm of breathing increased when dietary behavior, mental activity, pain reactions, acute emotional stress, fatigue in real productive activity. Uneven breathing rhythm changed unilaterally with blood pressure (r=0.66) and galvanic skin response (r=0.81). Uneven breathing rhythm changed from 0 to 20 % in diff erent functional states of the body. The increasing irregularity of the rhythm of breathing more than 30 % was short-lived, and was a harbinger of the imminent death of the body. The unevenness of respiratory rhythm was possible to predict the survival of animals in acute experimental emotional stress. Assessment of the degree of analgesia using the uneven rhythm of breathing helped to develop the microwave refl ex therapy. Study of the uneven breathing rhythm in actual work activity contributed to the prevention of the workers morbidity. The hunger motivation in humans was investigated in olfactory stimuli with the unevenness of breathing rhythm. The unevenness of respiratory rhythm has characterized the magnitude of the animals’ emotional reactions over itself stimulation of the brain.

Brain-Computer Interfaces (BCIs) are devices designed for establishing communication between the central nervous system and a computer. The communication can occur through different sensory modalities, and most commonly visual and auditory modalities are used. Here we propose that BCIs can be expanded by the incorporation of olfaction and discuss the potential applications of such olfactory BCIs. To substantiate this idea, we present results from two olfactory tasks: one that required attentive perception of odors without any overt report, and the second one where participants discriminated consecutively presented odors. In these experiments, EEG recordings were conducted in healthy participants while they performed the tasks guided by computer-generated verbal instructions. We emphasize the importance of relating EEG modulations to the breath cycle to improve the performance of an olfactory-based BCI. Furthermore, theta-activity could be used for olfactory-BCI decoding. In our experiments, we observed modulations of theta activity over the frontal EEG leads approximately 2 s after the inhalation of an odor. Overall, frontal theta rhythms and other types of EEG activity could be incorporated in the olfactory-based BCIs which utilize odors either as inputs or outputs. These BCIs could improve olfactory training required for conditions like anosmia and hyposmia, and mild cognitive impairment.

Respiratory activity is the most important basic life activity of human body, respiratory state detection is of great practical significance. Based on the characteristic of high correlation between the change of tidal volume and the change of abdominal displacement, a method of detecting respiratory status through abdominal displacement data is proposed. The method uses a gas pressure sensor to collect the tidal volume in the steady state of the subject once, which is used as the baseline data. The abdominal displacement data of the subject in the three breathing states of slow breathing, steady breathing and rapid breathing were collected with an acceleration sensor. The warp path distance between the lung and abdominal data in the three different states was calculated, this warp path distance together with the period extracted from the abdominal data is used as a two-dimensional feature and input to the support vector machine classifier. The experiments show that the accuracy of the classification results reaches 90.23%. The method only needs to measure the lung data once in smooth breathing state, and the subsequent continuous detection is achieved by measuring the displacement of the abdomen only. This method has the advantages of stable and reliable acquisition results, low implementation cost and simplified wearing method, and has high practicality.

Resting breathing and ventilatory chemoreflexes are regulated in a 24-hr manner by the endogenous circadian clock. However, it is unclear how circadian biology influences different phases of the breath-to-breath respiratory cycle which are predominantly controlled by pontomedullary regions of the brainstem. Here, we performed whole-body plethysmography during quiet wakefulness in young adult male and female mice lacking the core clock gene Brain and Muscle Arnt-like 1 (BMAL1) to determine the extent to which the molecular clock affects respiratory cycle timing and ventilatory airflow mechanics. Breath waveform analysis revealed that male BMAL1 knockout (KO) mice exhibit time of day-specific differences in inspiratory and expiratory times, total cycle length, end inspiratory pause, relaxation time, and respiratory rate compared to wild-type littermates. Notably, changes in respiratory pattern were not observed in female BMAL1 KO mice when compared to wild-type females. Additionally, BMAL1 deficiency did not disrupt overall minute ventilation or peak airflow in either sex, suggesting total ventilatory function during quiet wakefulness is preserved. Taken together, these findings indicate that genetic disruption of the circadian clock in mice elicits sex-specific changes in respiratory cycle timing., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This document is a reply to a letter from Drs. Francescato and Cettolo regarding a recent review on cardiopulmonary exercise testing (CPET). The authors clarify that their review does not support relating volumes computed using one definition of the breathing cycle to gas tensions measured using a different definition, as this would lead to misinterpretation of key CPET variables. Instead, the review emphasizes the physiological implications of using different definitions of the breathing cycle and suggests investigating an approach to identify an equivalent value for pulmonary ventilation. The authors also highlight the broader implications of different definitions on respiratory measurements in various fields, such as ventilator management and the diagnosis and treatment of certain conditions. They acknowledge the need for further research to understand the impact of alternative definitions on CPET interpretation. The document concludes by stating that while alternative breathing cycle definitions may enrich the information provided by gas exchange measurement, their applications remain limited due to a lack of comprehensive data. The authors disclose their funding sources and potential conflicts of interest. [Extracted from the article]

In this study, feature extraction methods used in the classification of single-channel lung sounds obtained by automatic identification of respiratory cycles were examined in detail in order to extract distinctive features at the lowest size. In this way, it will be possible to design a system for the detection of lung diseases, completely autonomously. In the study, automatic separation and classification of 400 respiratory cycles were performed from the single-channel common lung sounds obtained from 94 people. Leave one out cross validation (LOOCV) was used for the calibration and validation of the classification model. The Mel frequency cepstrum coefficients (MFCC), time domain features, frequency domain features, and linear predictive coding (LPC) were used for classification. The performance of the features was tested using linear discriminant analysis (LDA), k-nearest neighbors (k-NN), support vector machines (SVM), and naive Bayes (NB) classification algorithms. The success of combinations of features was explored and enhanced using the sequential forward selection (SFS). As a result, the best accuracy (90.14% in the training set and 90.63% in the test set) was acquired using the k-NN for the triple combination, which included the standard deviation of LPC and the standard deviation and the mean of MFCC. [ABSTRACT FROM AUTHOR]

[Display omitted] Thoracic computed tomography scans (CT) are used by several study groups to investigate the circulatory structures (heart and vessels) located behind the pressure point for chest compressions. Yet, it remains unclear how the positioning of these structures is influenced by factors such as intubation, the respiratory cycle and arm positioning. We retrospectively analyzed data of adult patients with in- or out-of-hospital cardiac arrest who underwent thoracic CT imaging within one year before or up to six months after arrest. A region of interest (ROI) behind the pressure point was defined. The largest structure within this region was defined as "leading circulatory structure", which was the primary outcome. Airway status (intubated versus spontaneous breathing), respiratory cycle (inspiration, expiration, resting expiratory position), and arm position (up over the head versus down beside the trunk) served as covariates in an ordinal regression model. Among 500 initially screened patients, 411 (82.2 %) were included in the analysis. There was a significant association between the arm position and the leading circulatory structure behind the pressure point. However, no association was found with airway status or respiratory cycle. The most frequently identified leading circulatory structure was the left atrium (arms up: 41.8 %, down: 50.7 %), followed by the ascending aorta (up: 23.8 % vs. down: 16.7 %). The left ventricle was the leading structure in only one case (0.2 %, arms down). This study shows that arm position is significantly associated with the leading circulatory structure behind the pressure point for chest compressions in cardiac arrest. [ABSTRACT FROM AUTHOR]

In the course of Human Physiology, students of different specialties learn cyclic processes reflecting the work of the cardiovascular, respiratory, female reproductive systems and sleep as well. Visualization of the cyclic processes is essential for better understanding of the organization and functioning of these systems and finding pathological deviations with formation of defective cycles. The objective of the work is to analyze the application of the visualization of the respiratory stages into the educational process. Dynamics of the physiological processes at various stages of respiration with the help of schematic visual figures allows effective formation of the students’ systemic understanding of the respiratory system functions and its interrelations with the cardiovascular system. These enable to apply the acquired theoretical knowledge while solving clinical situational tasks and formation of professional competence.

In the mouse olfactory system, odor signals detected in the olfactory epithelium are converted to a topographic map of activated glomeruli in the olfactory bulb. The map information is then conveyed by projection neurons, mitral cells and tufted cells, to various areas in the olfactory cortex. An odor map is transmitted to the anterior olfactory nucleus by tufted cells for odor identification and recollection of associated memory for learned decisions. For instinct decisions, odor information is directly transmitted to the valence regions in the amygdala by specific subsets of mitral cells. Transmission of orthonasal odor signals through these two distinct pathways, innate and learned, are closely related with exhalation and inhalation, respectively. Furthermore, the retronasal/interoceptive and orthonasal/exteroceptive signals are differentially processed during the respiratory cycle, suggesting that these signals are processed in separate areas of the olfactory bulb and olfactory cortex. In this review article, the recent progress is summarized for our understanding of the olfactory circuitry and processing of odor signals during respiration. [ABSTRACT FROM AUTHOR]

In the mouse olfactory system, odor signals detected in the olfactory epithelium are converted to a topographic map of activated glomeruli in the olfactory bulb. The map information is then conveyed by projection neurons, mitral cells and tufted cells, to various areas in the olfactory cortex. An odor map is transmitted to the anterior olfactory nucleus by tufted cells for odor identification and recollection of associated memory for learned decisions. For instinct decisions, odor information is directly transmitted to the valence regions in the amygdala by specific subsets of mitral cells. Transmission of orthonasal odor signals through these two distinct pathways, innate and learned, are closely related with exhalation and inhalation, respectively. Furthermore, the retronasal/interoceptive and orthonasal/exteroceptive signals are differentially processed during the respiratory cycle, suggesting that these signals are processed in separate areas of the olfactory bulb and olfactory cortex. In this review article, the recent progress is summarized for our understanding of the olfactory circuitry and processing of odor signals during respiration.

In mammals, odor information detected by olfactory sensory neurons is converted to a topographic map of activated glomeruli in the olfactory bulb. Mitral cells and tufted cells transmit signals sequentially to the olfactory cortex for behavioral outputs. To elicit innate behavioral responses, odor signals are directly transmitted by distinct subsets of mitral cells from particular functional domains in the olfactory bulb to specific amygdala nuclei. As for the learned decisions, input signals are conveyed by tufted cells as well as by mitral cells to the olfactory cortex. Behavioral scene cells link the odor information to the valence cells in the amygdala to elicit memory-based behavioral responses. Olfactory decision and perception take place in relation to the respiratory cycle. How is the sensory quality imposed on the olfactory inputs for behavioral outputs? How are the two types of odor signals, innate and learned, processed during respiration? Here, we review recent progress on the study of neural circuits involved in decision making in the mouse olfactory system. [ABSTRACT FROM AUTHOR]

In the mouse olfactory system, odor information is converted to a topographic map of activated glomeruli in the olfactory bulb (OB). Although the arrangement of glomeruli is genetically determined, the glomerular structure is plastic and can be modified by environmental stimuli. If the pups are exposed to a particular odorant, responding glomeruli become larger recruiting the dendrites of connecting projection neurons and interneurons. This imprinting not only increases the sensitivity to the exposed odor, but also imposes the positive quality on imprinted memory. External odor information represented as an odor map in the OB is transmitted to the olfactory cortex (OC) and amygdala for decision making to elicit emotional and behavioral outputs using two distinct neural pathways, innate and learned. Innate olfactory circuits start to work right after birth, whereas learned circuits become functional later on. In this paper, the recent progress will be summarized in the study of olfactory circuit formation and odor perception in mice. We will also propose new hypotheses on the timing and gating of olfactory circuit activity in relation to the respiration cycle., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Mori and Sakano.)

• Arsenic (As) caused a marked inhibition in organic acid production and activity of enzymes of respiratory cycle in the susceptible variety, Khitish. • Arsenic exposure stimulated the accumulation of sugar in both the cultivars. • Exogenous melatonin supplementation improved the accumulation of organic acids in Khitish. • Exogenous melatonin supplementation significantly increased the activities of enzymes and corresponding gene expressions related to respiratory cycle and sugar metabolism. • The ameliorative effect of melatonin was more prominent in the susceptible variety as compared to the tolerant cultivar. The objective of the present investigation was to understand the impact of exogenously applied melatonin on mitochondrial respiration and sugar metabolism in two contrasting rice cultivars, viz., Khitish (arsenic-susceptible) and Muktashri (arsenic-tolerant) under arsenic-stress. Melatonin effectively restored the level of organic acids like pyruvic acid, malic acid and more particularly citric acid by 33 % in Khitish which were lowered during arsenic-stress, whereas their levels were further elevated in Muktashri to provide energy for defence against arsenic-induced injury. Arsenic-exposure led to a significant inhibition in enzyme activities as well as corresponding transcript level of key respiratory enzymes, viz., pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, intriguingly more prominently in case of Khitish. Conversely, melatonin supplementation, irrespective of cultivars, considerably improved the activity of the above enzymes and corresponding gene expressions during stress, indicating acceleration in the rate of Krebs cycle. Melatonin supplementation also stimulated the accumulation of total soluble sugars by 62 % and 25 %, reducing sugars by 50 % and 44 % and non-reducing sugars by 75 % and 14 % in Khitish and Muktashri respectively, concomitant with higher activities of acid invertase, sucrose synthase and sucrose phosphate synthase enzymes, along with the expression of corresponding genes. Enhanced starch accumulation via regulation of alpha amylase and starch phosphorylase activities and gene expression, by melatonin also contributed towards better stress tolerance. Overall, this work illustrated the efficacy of melatonin in the regulation of representative organic acids and enzymes of respiratory cycle along with starch and sugar metabolism in rice cultivars under arsenic toxicity. [ABSTRACT FROM AUTHOR]

Little is known about the dynamics of baleen whale respiratory cycles, especially the mechanics and activity of the blowholes and their interaction with seawater. In this study, the duration of complete respiration cycles (expiration/inhalation events) were quantified for the first time in two species: North Atlantic right whale (NARW) and humpback whale (HW) using high resolution, detailed imagery from an unoccupied aerial system (UAS). The mean duration of complete respiration cycles (expiration/inhalation event) in the NARW and HW were 3.07 s (SD = 0.503, n = 15) and 2.85 s (SD = 0.581, n = 21), respectively. Furthermore, we saw no significant differences in respiration cycle duration between age and sex classes in the NARW, but significant differences were observed between age classes in the HW. The observation of seawater covering an open blowhole was also quantified, with NARW having 20% of all breaths with seawater presence versus 90% in HW. Seawater incursion has not been described previously and challenges the general consensus that water does not enter the respiratory tract in baleen whales. Prevalent seawater has implications for the analysis and interpretation of exhaled respiratory vapor/mucosa samples, as well as for the potential inhalation of oil in spills. [ABSTRACT FROM AUTHOR]

Background/Objectives: The objective of the present study was to use original data on respiration and tumor location coordinates saved during treatment period of patients who underwent body Radiotherpay to operate a 3D phantom for backward verification of the accuracy of stereotactic body radiotherapy. Methods/Statistical analysis: The present study acquired original treatment data of 20 patients who underwent CyberKnife radiotherapy. Radiation was irradiated on the 3D phantom after applying external respiratory coordinates and tumor movement coordinate, which were original data from actual patients. The irradiated radiochemical film was scanned 24 hour later and assessment was made by γ-index values based on comparison of 2D dose distribution and radiotherapy plan. Findings: The mean correlation error of entire treatment process of 20 patients was 1.26±073 (range: 0.47-1.98). The mean respiratory cycle of the patients during the entire treatment period was 3.77 sec (range: 1.90-5.39 sec). As an indicator of regularity of patient respiratory cycle, standard deviation of respiration during the entire treatment period was measured, the results of which showed minimum of 0.35 and maximum of 1.65. When the respiration and internal tumor movement of entire process after completion of treatment in 20 patients were applied to the 3D phantom for comparative analysis against the treatment plan, the mean pass rate of gamma-index values was 95.20±4.35% (range: 81.87% - 99.92%). Since the mean pass rate was ≥ 95%, accuracy of radiotherapy was confirmed by backward verification Improvements/Applications: The significance of the present study can be found in the fact that it performed backward dose verification by reproducing respiratory and tumor coordinate after radiotherapy, using the same condition as before radiotherapy. [ABSTRACT FROM AUTHOR]

Identification of the breathing cycle forms the basis of any breath-by-breath gas exchange analysis. Classically, the breathing cycle is defined as the time interval between the beginning of two consecutive inspiration phases. Based on this definition, several research groups have developed algorithms designed to estimate the volume and rate of gas transferred across the alveolar membrane ("alveolar gas exchange"); however, most algorithms require measurement of lung volume at the beginning of the i th breath ( V Li- 1 ; i.e., the end-expiratory lung volume of the preceding i th breath). The main limitation of these algorithms is that direct measurement of V Li- 1 is challenging and often unavailable. Two solutions avoid the requirement to measure V Li- 1 by redefining the breathing cycle. One method defines the breathing cycle as the time between two equal fractional concentrations of lung expired oxygen ( Fo 2 ) (or carbon dioxide; Fco 2 ), typically in the alveolar phase, whereas the other uses the time between equal values of the Fo 2 / Fn 2 (or Fco 2 / Fn 2 ) ratios [i.e., the ratio of fractional concentrations of lung expired O 2 (or CO 2 ) and nitrogen (N 2 )]. Thus, these methods identify the breathing cycle by analyzing the gas fraction traces rather than the gas flow signal. In this review, we define the traditional approach and two alternative definitions of the human breathing cycle and present the rationale for redefining this term. We also explore the strengths and limitations of the available approaches and provide implications for future studies.

The aim of the present study was to investigate the association between the dynamic intensity-modulated radiation therapy planned γ analysis passing rate and respiratory amplitude (A) and period (T) for different tumor volumes. A total of 30 patients with malignant lung tumors were divided into three groups: A; B; and C. The average tumor volumes (V) in the A, B and C groups were 635, 402 and 213 cm3, respectively. The simulated A values were set at 0, 5, 10, 15, 20 and 25 mm. The T values were set at 4, 5 and 6 sec. The γ analysis passing rate was calculated under different conditions (dose difference, 3%; distance difference, 3 mm). Compared with the γ analysis passing rate in the A group (A=0, static; T=4, 5, 6 sec), the γ analysis passing rate deviation (A=5 mm) was <3.3%. However, this difference was not statistically significant (P>0.05). With a gradual increase in A value, the passing rate decreased. The deviation between the 3 groups was <2.5% at the same A value (T=4, 5 and 6 sec). A descending trend of passing rate with increased A value was revealed. At the same A and T values, the passing rate decreased with decreased tumor volume. At the same tumor volume, the passing rate decreased when the A value increased. The respiratory cycle was not demonstrated to be associated with the passing rate. Overall, these results suggest that the A value should be controlled in clinical radiotherapy. [ABSTRACT FROM AUTHOR]

Purpose: A new algorithm is illustrated for the determination of breath-by-breath alveolar gas exchange that neglects the contiguity in time of breaths, i.e. it allows the breaths to be partially superimposed or disjoined in time.Methods: Traces of oxygen, carbon dioxide fractions, and ventilatory flow were recorded continuously over 20 min in 15 healthy subjects in resting conditions; at 5-min intervals, subjects voluntarily hyperventilated for ~ 30 s to induce abrupt changes in lung gas stores. Gas exchange data were calculated applying the new algorithm and were compared to those yielded by a reference algorithm, also providing values at the alveolar level.Results: Average O2 uptakes (V'O2) obtained with the two algorithms were similar during quiet breathing (0.28 ± 0.06 vs. 0.29 ± 0.06 L/min; two-sided paired t test, n = 45, p = NS); during hyperventilation, average V'O2 was significantly lower applying the new algorithm compared to the reference algorithm (0.57 ± 0.15 vs. 0.65 ± 0.17 L/min; difference - 0.077 ± 0.048 L/min; two-sided paired t test, n = 45, p < 0.001). The first breath of each hyperventilation manoeuvre showed the greatest difference in V'O2 (- 0.25 ± 0.23 L/min, z test against zero, n = 45, p < 0.001). The volumes of O2 considered twice (or neglected) because of the lack of contiguity of breaths were overall small (maximum of 3 mL) and, if accounted for, had only a slight softening effect on the fluctuations of the O2 uptake.Conclusion: The new algorithm, which assumes each breath as the leading subject, was able to effectively account for changes in lung gas stores without requiring any predetermined value or off-line optimisation procedure. [ABSTRACT FROM AUTHOR]

Summary: The automatic metabolic units calculate breath‐by‐breath gas exchange from the expiratory data only, applying an algorithm (‘expiration‐only’ algorithm) that neglects the changes in the lung gas stores. These last are theoretically taken into account by a recently proposed algorithm, based on an alternative view of the respiratory cycle (‘alternative respiratory cycle’ algorithm). The performance of the two algorithms was investigated where changes in the lung gas stores were induced by abrupt increases in ventilation above the physiological demand. Oxygen, carbon dioxide fractions and ventilatory flow were recorded at the mouth in 15 healthy subjects during quiet breathing and during 20‐s hyperventilation manoeuvres performed at 5‐min intervals in resting conditions. Oxygen uptakes and carbon dioxide exhalations were calculated throughout the acquisition periods by the two algorithms. Average ventilation amounted to 6·1 ± 1·4 l min−1 during quiet breathing and increased to 41·8 ± 27·2 l min−1 during the manoeuvres (P<0·01). During quiet breathing, the two algorithms provided overlapping gas exchange data and noise. Conversely, during hyperventilation , the ‘alternative respiratory cycle’ algorithm provided significantly lower gas exchange data as compared to the values yielded by the ‘expiration‐only’ algorithm. For the first breath of hyperventilation, the average values provided by the two algorithms amounted to 0·37 ± 0·34 l min−1 versus 0·96 ± 0·73 l min−1 for O2 uptake and 0·45 ± 0·36 l min−1 versus 0·80 ± 0·58 l min−1 for exhaled CO2 (P<0·001 for both). When abrupt increases in ventilation occurred, such as those arising from a deep breath, the ‘alternative respiratory cycle’ algorithm was able to halve the artefactual gas exchange values as compared to the ‘expiration‐only’ approach. [ABSTRACT FROM AUTHOR]

Objective: To research the anesthesia effect of dexmedetomidine combined with propofol on the clear tracheal intubation and the influences on the respiration and circulation. Methods: 80 cases of clearly tracheal intubation from January 2015 to 2016 were selected and divided into two groups according to different anesthesia with 40 patients in each group. The control group was induced by propofol anesthesia, the research group was induced by dexmedetomidine combined with propofol anesthesia. The anesthetic effect, breathing and circulation, and incidence of complications were compared between the two groups. Results: The intubation time,ramsay score, well tolerated, intubation success rate, respiratory rate, minute ventilation, heart rate and mean arterial pressure of research group were significantly higher than those of the control group(P<0.05), the tidal volume, serum norepinephrine and cortisol levels of research group were lower than those of the control group(P<0.05). Conclusion: Dexmedetomidine combined with propofol was effective in the awake tracheal intubation, which could reduce the inhibition of respiration and circulation. [ABSTRACT FROM AUTHOR]

Listening to the sounds made by the lungs is a long-standing method that is still used to diagnose lung diseases. Many studies have been conducted on the automatic recognition of recorded sounds from the lungs. However, in these studies, respiratory cycles, i.e. inhalations followed by exhalations, were either monitored manually or by using multichannel signals of the sounds made by the lungs. In order to recognize sounds made by the lungs automatically, one must first use these sounds to determine the respiratory cycles. Our previous study was the first study presented in the literature in which the boundaries of respiratory cycles were determined based on single-channel sounds from the lungs. However, this method was not successful when ambient noise occurred and interfered with the sounds from the lungs. In the present study, a new method has been developed in which important changes were made to reduce or negate the effects of ambient noises. Our proposed new method includes a processing method that we developed to obtain respiratory cycles as smooth, repetitive patterns. Then the dynamic time-warping algorithm was used to determine the boundaries of the respiratory cycles, based on the similarity of the patterns. This new method was used to detect the seven sounds that are commonly made by the lung. As a result, the limits of the respiratory cycles were obtained with a mean absolute error of 56.51 ms. In addition, the method we developed has the potential to determine the boundaries of the patterns in signals that contain repetitive data, such as the sounds made by the lungs in this study. [ABSTRACT FROM AUTHOR]

Respiratory activity is the most important basic life activity of human body, respiratory state detection is of great practical significance. Based on the characteristic of high correlation between the change of tidal volume and the change of abdominal displacement, a method of detecting respiratory status through abdominal displacement data is proposed. The method uses a gas pressure sensor to collect the tidal volume in the steady state of the subject once, which is used as the baseline data. The abdominal displacement data of the subject in the three breathing states of slow breathing, steady breathing and rapid breathing were collected with an acceleration sensor. The warp path distance between the lung and abdominal data in the three different states was calculated, this warp path distance together with the period extracted from the abdominal data is used as a two-dimensional feature and input to the support vector machine classifier. The experiments show that the accuracy of the classification results reaches 90.23%. The method only needs to measure the lung data once in smooth breathing state, and the subsequent continuous detection is achieved by measuring the displacement of the abdomen only. This method has the advantages of stable and reliable acquisition results, low implementation cost and simplified wearing method, and has high practicality., Competing Interests: The authors declare no conflict of interest., (©2023PublishedbyElsevierLtd.)