Nonstationary Heart Rate Variability in Respiratory Tests

A new method was proposed for processing a nonstationary heart rate by using frequency-modulated signals rather than amplitude-modulated signals equally spaced over several points of time as in the conventional method. A frequency-modulated signal is a set of identical Gaussian peaks that coincide with the true time points of heart beats. A continuous wavelet transform was used to quantitatively describe the heart rhythm signal. A test with controlled breathing was performed as an example and included three consecutive stages: rest, rhythmic breathing at a specified frequency, and exhalation. Tachograms recorded during the breath test was found to be a nonstationary signal with the alternation of peaks of different spectral ranges. A system of quantitative parameters was developed to describe the dynamics of changes in the spectral properties of the tachogram in transitional areas. A static clustering by the effect of the respiratory test and a dynamic clustering in order to identify the time points when the autonomic nervous system is stressed were performed for all subjects. The article discusses the prospects of using the method as a means to analyze the transient effects in various functional tests and as biofeedback that would help to change the heart rhythm.     

Models of Chance when Measuring Interrater Agreement with Kappa

Two measures of reliability for nominal scales are compared: Coefficient Kappa and k_n, a modification suggested for agreement matrices with free marginals. It is illustrated that the evaluation of two rater's agreement may come to a contradictory conclusion, depending on whether k or k_n is used. On the basis of the underlying chance models it is concluded that k and k_n cannot be interpreted in the same manner. Specifically when raters disagree, the two measures can be widely discrepant.     

Measuring Respiratory Function in Mice Using Unrestrained Whole-body Plethysmography

Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative assessment of lung function in rodent models is an important tool in the development of future therapies. Commonly used techniques for assessing respiratory function including invasive plethysmography and forced oscillation. While these techniques provide valuable information, data collection can be fraught with artefacts and experimental variability due to the need for anesthesia and/or invasive instrumentation of the animal. In contrast, unrestrained whole-body plethysmography (UWBP) offers a precise, non-invasive, quantitative way by which to analyze respiratory parameters. This technique avoids the use of anesthesia and restraints, which is common to traditional plethysmography techniques. This video will demonstrate the UWBP procedure including the equipment set up, calibration and lung function recording. It will explain how to analyze the collected data, as well as identify experimental outliers and artefacts that results from animal movement. The respiratory parameters obtained using this technique include tidal volume, minute volume, inspiratory duty cycle, inspiratory flow rate and the ratio of inspiration time to expiration time. UWBP does not rely on specialized skills and is inexpensive to perform. A key feature of UWBP, and most appealing to potential users, is the ability to perform repeated measures of lung function on the same animal.     

Estimation of Respiratory Nasal Pressure and Flow Rate Signals Using Different Respiratory Sound Features

BackgroundRespiratory sounds are associated with the flow rate, nasal flow pressure, and physical characteristics of airways. In this study, we aimed to develop the flow rate and nasal flow pressure estimation models for the clinical application, and find out the optimal feature set for estimation to achieve the optimal model performance.MethodsRespiratory sounds and flow rate were acquired from nine healthy volunteers. Respiratory sounds and nasal flow pressure were acquired from twenty-three healthy volunteers. Four types of respiratory sound features were extracted for flow rate and nasal flow pressure estimation using different estimation models. Effects of estimations using these features were evaluated using Bland-Altman analysis, estimation error, and respiratory sound feature calculation time. Besides, expiratory and inspiratory phases divided estimation errors were compared with united estimation errors.ResultsThe personalized logarithm model was selected as the optimal flow rate estimation model. Respiratory nasal flow pressure estimation based on this model was also performed. For the four different respiratory sound features, there is no statistically significant difference in flow rate and pressure estimation errors. LogEnvelope was, therefore, chosen as the optimal feature because of the lowest computational cost. In addition, for any type of respiratory sound feature, no statistically significant difference was observed between divided and united estimation errors (flow rate and pressure).ConclusionRespiratory flow rate and nasal flow pressure can be estimated accurately using respiratory sound features. Expiratory and inspiratory phases united estimation using respiratory sounds is a more reasonable estimation method than divided estimation. LogEnvelope can be used for this united respiratory flow rate and nasal flow pressure estimation with minimum computational cost and acceptable estimation error.     

Validation of Respiratory Inductance Plethysmography for Measuring Tidal Volume in Swine

Measuring tidal volume (V_T) in nonintubated swine or swine with leaking breathing circuits is challenging. The aim of this study was to validate respiratory inductance plethysmography (RIP) for measuring V_T in swine that are comparable in size to adult humans. To determine calibration curves, V_T and RIP readings were obtained from anesthetized swine (n = 8; weight, 46–50 kg) during positive-pressure (mechanical) ventilation and spontaneous breathing. For positive-pressure ventilation, 6 pigs were mechanically ventilated by using the pressure-control mode. The 2 pigs in the spontaneously breathing cohort each received a single intravenous bolus dose of propofol to abolish spontaneous breathing; V_T was measured during gradual return of their respiratory drive. A flow–volume sensor was placed between the proximal end of the endotracheal tube and breathing circuit for the recording of inspiratory and expiratory V_T. RIP readings were recorded by using 2 bands, which simultaneously measured ribcage and abdominal excursions. The data revealed that V_T was linearly correlated with the movements of both ribcage and abdomen as measured by using plethysmography over a large range of tidal volume (44 to 1065 mL). In addition, the intercept of the linear equation was small or even negative during spontaneous breathing but increased significantly (maximum, 145 mL, 59.2 ± 35.1 mL) during positive pressure ventilation. Our results indicate that V_T in swine can be calculated by using a simple univariate linear regression equation with RIP readings obtained during either mechanical ventilation or spontaneous breathing.Abbreviations: RIP, respiratory inductance plethysmography; V_T, tidal volumeIn animal care and research, the respiratory function of swine is widely assessed by measuring tidal volume (V_T).⁶ Although V_T is easy to measure in intubated pigs, it is difficult to measure in swine that are either nonintubated or have significant breathing circuit leakage^16,24. Using facemasks attached to minimally restrained swine is currently the method of choice for measuring V_T. This methodology has multiple limitations, including incomplete sealing between the pig''s face and the mask, which is difficult to adapt to these animals. A reliable, minimally invasive method for determining V_T in this species is needed.Respiratory inductance plethysmography (RIP)^11,15 is a viable alternative to measuring V_T. Using RIP, both ribcage and abdominal movements can be recorded. The amplitude changes of the ribcage and abdomen are linearly correlated to the size of the corresponding V_T in humans. This method has been validated in humans^1,13 and is widely used clinically in adults,^14,18 newborns and infants.^5,8 RIP has also been used on animals including sheep⁴ and dogs.¹⁷However, RIP has not yet been validated for use in swine that are comparable in size to adult humans. Considering the profound physiologic and anatomic differences in the respiratory system between swine and humans,^12,20 the validation of plethysmography for use in humans might not extrapolate readily to swine, which are one of the most commonly used animal models in biomedical research. Here we sought to validate the RIP method for calculating V_T in swine during both positive-pressure ventilation and spontaneous breathing.     

Measuring Pairwise Agreement Among Many Observers. II. Some Improvements and Additions

Weighted kappa was defined as a measure of pairwise interobserver agreement for the case where the observers judging one subject are not necessarily the same as those judging another subject. In this paper improved formulas for the large sample variance of the weighted kappa statistic are derived, a new definition of interclass kappa coefficients is suggested, and the intraclass correlation coefficient is shown to be a special case of weighted kappa.     

不同成熟度杨梅果实采后呼吸速率、乙烯释放速率和品质的变化

以3个品种杨梅果实为材料,将采后果实分为未成熟(immature)、成熟(mature)和完熟(ripe)3种不同成熟度,在20℃下48 h贮藏过程中,每隔3 h检测一次呼吸速率和乙烯释放速率,并分析成熟过程相关的品质变化.结果表明,未成熟和成熟果实的呼吸速率和乙烯合成变化呈现典型的跃变型果实特征,而在完熟果实中检测不到呼吸和乙烯跃变过程.未成熟和成熟杨梅果实中PAL活性趋于提高,而完熟果实的呈下降变化,这一结果与矢车菊-3-葡萄糖苷(Cy-3-Glu)含量变化相吻合;CIRG值与杨梅果实Cv-3-Glu含量呈极显著正相关(r=0.96**).结果显示杨梅果实属于跃变型果实.     

Kinetic Concepts for Measuring Microbial Rate Constants: Effects of Nutrients on Rate Constants

We investigated the effect of preincubation of environmental waters amended with inorganic nutrients (nitrogen, phosphorus, and traces of iron and magnesium) on the kinetics of the microbial transformation of phenol, propanil, propyl ester of (2,4-dichlorophenoxy)acetic acid, methyl parathion, Ronnel, and methoxychlor in pond and river waters. No effect on the second-order rate constants for these compounds was observed, although there was an increase in the bacterial populations and the pseudo-first-order rate constants. The use of nutrient-amended waters could be a useful tool for estimating second-order rate constants for an expanded number of compounds. This technique would provide a larger data base for predicting the behavior of xenobiotic compounds in the environment by using currently available mathematical models.     

Measuring Exocytosis Rate Using Corrected Fluorescence Recovery After Photoconversion

Exocytosis plays crucial roles in regulating the distribution and function of plasma membrane (PM) and extracellular matrix proteins. However, measuring the exocytosis rate of a specific protein by conventional methods is very difficult because of exocytosis‐independent trafficking such as endocytosis, which also affects membrane protein distribution. Here, we describe a novel method, corrected fluorescence recovery after photoconversion, in which exocytosis‐dependent and ‐independent trafficking events are measured simultaneously to accurately determine exocytosis rate. In this method, the protein‐of‐interest is tagged with Dendra2, a green‐to‐red photoconvertible fluorescent protein. Following the photoconversion of PM‐localized Dendra2, both the recovery of the green signal and the changes in the photoconverted red signal are measured, and the rate of exocytosis is calculated from the changing rates of these two signals.      

测定冷藏蔬菜呼吸速率时的温度探讨

在冷藏温度下测定的呼吸速率与将冷藏蔬菜置于室温下立即测定或置于室温下1h后测定的呼吸速率有显著差异。低温下贮藏的蔬菜在室温下测定呼吸速率的结果不能真实地反映贮藏状态下的呼吸速率。冷藏蔬菜呼吸速率的测定应在冷藏温度下进行。     

Measuring photosynthetic parameters in individual algal cells by Fast Repetition Rate fluorometry

A Single Cell Fast Repetition Rate (SCFRR) fluorometer was developed to measure the quantum yield of photochemistry, the functional absorption cross section of PS II and the kinetics of electron transport on the acceptor side of PS II in individual algal cells. These parameters are used to quantify the cell-specific photosynthetic performance in natural phytoplankton assembledges in aquatic ecosystems. The SCFRR technique measures chlorophyll fluorescence transients induced by a precisely controlled series of excitation flashlets that cumulatively saturate PS II within 120 s. To meet the requirement in the analysis for single algal cells, the measurements are conducted in micro volumes, such that the probability of probing more than one cell at a time is vanishingly low. We designed a novel, computer-controlled hydromechanical system to deliver a portion of the sample into the measuring chamber and, following measurement, remove it into one of six sorting containers. The fluorescence signal is induced by a series of high frequency flashlets obtained from high luminosity blue light-emitting diodes and is acquired by a novel red-sensitive PMT-based detection system exhibiting both high sensitivity and a very wide dynamic range. The wide dynamic range of the detector allows SCFRR measurements for a wide variety of cell sizes ranging from 1 to 100 m equivalent spherical diameter. The compact and light-weight design makes the SCFRR Fluorometer applicable for both laboratory and field studies.     

Improving the Accuracy and Efficiency of Respiratory Rate Measurements in Children Using Mobile Devices

The recommended method for measuring respiratory rate (RR) is counting breaths for 60 s using a timer. This method is not efficient in a busy clinical setting. There is an urgent need for a robust, low-cost method that can help front-line health care workers to measure RR quickly and accurately. Our aim was to develop a more efficient RR assessment method. RR was estimated by measuring the median time interval between breaths obtained from tapping on the touch screen of a mobile device. The estimation was continuously validated by measuring consistency (% deviation from the median) of each interval. Data from 30 subjects estimating RR from 10 standard videos with a mobile phone application were collected. A sensitivity analysis and an optimization experiment were performed to verify that a RR could be obtained in less than 60 s; that the accuracy improves when more taps are included into the calculation; and that accuracy improves when inconsistent taps are excluded. The sensitivity analysis showed that excluding inconsistent tapping and increasing the number of tap intervals improved the RR estimation. Efficiency (time to complete measurement) was significantly improved compared to traditional methods that require counting for 60 s. There was a trade-off between accuracy and efficiency. The most balanced optimization result provided a mean efficiency of 9.9 s and a normalized root mean square error of 5.6%, corresponding to 2.2 breaths/min at a respiratory rate of 40 breaths/min. The obtained 6-fold increase in mean efficiency combined with a clinically acceptable error makes this approach a viable solution for further clinical testing. The sensitivity analysis illustrating the trade-off between accuracy and efficiency will be a useful tool to define a target product profile for any novel RR estimation device.     

采后钙处理对荔枝果实过氧化物酶活性、呼吸率及乙烯生成的影响

荔枝果实采后用钙处理,结果表明,适当地提高果实钙含量,可以抑制过氧化物酶的活性,降低呼吸作用及乙烯的生成,达到延缓衰老的目的。本实验以8％钙处理效果最佳。