[Research on portable airway impedance monitoring device based on expiratory oscillation].

Monitoring airway impedance has significant clinical value in accurately assessing and diagnosing pulmonary function diseases at an early stage. To address the issue of large oscillator size and high power consumption in current pulmonary function devices, this study adopts a new strategy of expiration-driven oscillation. A lightweight and low-power airway impedance monitoring system with integrated sensing, control circuitry, and dynamic feedback system, providing visual feedback on the system's status, was developed. The respiratory impedance measurement experiments and statistical comparisons indicated that the system could achieve stable measurement of airway impedance at 5 Hz. The frequency spectrum curves of respiratory impedance ( R and X) showed consistent trends with those obtained from the clinical pulmonary function instrument, specifically the impulse oscillometry system (IOS). The differences between them were all less than 1.1 cm H 2O·s/L. Additionally, there was a significant statistical difference in the respiratory impedance R5 between the exercise and rest groups, which suggests that the system can measure the variability of airway resistance parameters during exercise. Therefore, the impedance monitoring system developed in this study supports subjects in performing handheld, continuous measurements of dynamic changes in airway impedance over an extended period of time. This research provides a foundation for further developing low-power, portable, and even wearable devices for dynamic monitoring of pulmonary function.

Using digital technology for home monitoring, adherence and self-management in cystic fibrosis: a state-of-the-art review.

Digital healthcare is a rapidly growing healthcare sector. Its importance has been recognised at both national and international level, with the WHO recently publishing its first global strategy for digital health. The use of digital technology within cystic fibrosis (CF) has also increased. CF is a chronic, life-limiting condition, in which the treatment burden is high and treatment regimens are not static. Digital technologies present an opportunity to support the lives of people with CF. We included 59 articles and protocols in this state-of-the-art review, relating to 48 studies from 1999 until 2019. This provides a comprehensive overview of the expansion and evolution of the use of digital technology. Technology has been used with the aim of increasing accessibility to healthcare, earlier detection of pulmonary exacerbations and objective electronic adherence monitoring. It may also be used to promote adherence and self-management through education, treatment management Apps and social media.

Point-of-care blood gas analyzers have an impact on the acceptance of donor lungs for transplantation.

An organ donor PaO2 above 40 kPa is generally required for lung transplantation. Point-of-care (POC) blood gas analyzers are commonly used by organ procurement organizations (OPO) but may underestimate the PaO2 at high levels. We hypothesized that changing to a more accurate blood gas analyzer would result in additional lungs transplanted. All PaO2 measurements on organ donors managed at one OPO's recovery center were performed on an i-STAT POC analyzer prior to October 2015, and on a GEM 4000 subsequently. For 24 weeks, all blood gases were tested simultaneously on both analyzers. We compared lung outcomes of 147 donors in the year prior to this change (using the i-STAT) with 56 donors in the 24-week study period (using the GEM 4000 for lung allocation). When the PaO2 was above 40 kPa, the i-STAT PaO2 was 7.2 kPa lower on average than the GEM 4000. When the GEM PaO2 measured between 40 and 50 kPa, the corresponding i-STAT PaO2 value registered less than 40 kPa 25 out of 48 times (52%), with an average difference of 7.3 kPa (SD = 2.9). The rate of lungs transplanted using the GEM 4000 was 48% compared with 35% in the year prior using the i-STAT (p = .11), with equivalent recipient outcomes. The i-STAT analyzer underestimated the PaO2 above 40 kPa and changing to a more accurate PaO2 analyzer may increase lungs transplanted.

Concordant Validity of a Digital Peak Cough Flow Meter to Assess Voluntary Cough Strength in Individuals with ALS.

Peak cough flow represents an important metric directly related to the physiologic ability of an individual to defend the airway or expel tracheal aspirate. Given the high prevalence of dysphagia and dystussia in individuals with amyotrophic lateral sclerosis (ALS) and recent findings that the expiratory phase of voluntary cough is significantly impaired in ALS individuals, we aimed to determine the reproducibility of an affordable, portable peak cough flow (PCF) meter for the assessment of cough production in individuals with ALS. 109 individuals with ALS completed voluntary cough testing using both the research cough spirometry equipment and a digital peak cough flow meter. Maximum peak expiratory cough flow rates were obtained from each device. Analyses included paired t test, Pearson's correlation, and Lin's concordance correlation to determine the degree of agreement and reproducibility between cough measurement devices (alpha = 0.05). Mean differences between peak cough flow test values (L/min) across instruments were not statistically significant (mean difference = - 2.93; 95% CI - 18.67, 12.82; p = 0.713). PCF values obtained from the digital peak cough flow meter and the research cough spirometry equipment were strongly associated (r = 0.826, p < 0.000) and demonstrated a high level of agreement and reproducibility (ρc = 0.824, 95% CI 0.754, 0.876). These data validate the use of an inexpensive and portable digital peak cough flow device to index peak cough flow strength in individuals with ALS. This assessment could easily be incorporated into a multidisciplinary ALS clinical setting to index the physiologic ability of an individual to protect the airway.

Cuff Leak Test for the Diagnosis of Post-Extubation Stridor: A Multicenter Evaluation Study.

BACKGROUND:: Cuff leak test was developed to predict the occurrence of post-extubation stridor (PES). This study evaluated the diagnostic performance of this test in unselected critically ill patients. METHODS:: Multicenter prospective study including unselected ventilated patients at the time of their first planned extubation. The diagnostic performance of 4 different cuff leak tests was assessed. RESULTS:: Post-extubation stridor occurred in 34 (9.4%) of 362 included patients. Compared to patients without PES, patients with PES required more frequently reintubation (6 [17.6%] vs 26 [7.9%], P = .041), prolonged duration of ventilation (6 [3-13] vs 5 [2-9] days, P = .029), and longer intensive care unit (ICU) stay (12 [6-17.5] vs 7.5 [4-13] days, P = .018). However, ICU mortality was similar in both groups (1 [2.9%] vs 23 [7.0%], P = .61). The 4 cuff leak tests display poor diagnostic accuracy: sensitivities ranging from 27% to 46%, specificities from 70% to 88%, positive predictive values from 14% to 19%, and negative predictive values from 92% to 93%. CONCLUSION:: Post-extubation stridor occurs in less than 10% of unselected critically ill patients. The several cuff leak tests display limited diagnostic performance for the detection of PES. Given the high rate of false positives, routine cuff leak test may expose to undue prolonged mechanical ventilation.

Aligning Lung Function Equipment and Reference Values in Adults.

BACKGROUND: When introducing new equipment or reference equations into the lung function laboratory, systematic z-score deviations could arise due to local differences in population or equipment. OBJECTIVE: To propose a workable method for aligning reference equations with lung function equipment. METHOD: Using two cases of equipment transition in our laboratory as a test case, we first performed lung function testing after the transition, on a control group of 40 normal young adults (20 male/20 female; 20-30 years old). For those indices with an average z-score in excess of ±0.5, adapted reference values were obtained by an offset or scaling factor on the M coefficient with the so-called lambda-mu-sigma (LMS) method recommended by the Global Lung Function Initiative, and the z-scores were computed again. RESULTS: Following a transition involving instrumental dead space reduction, the lung clearance index was predictably reduced, resulting in a mean (±SD) z-score of -1.9 (±1.1) in the control group; by adapting the reference values with an offset on M, the z-score became -0.1 (±1.1). Applying the same method to a transition of standard lung function equipment, the z-scores became centered around zero in the control group, but also became properly aligned in a test group of 81 other subjects spanning a wider age range (20-80 years). CONCLUSIONS: We proposed and verified a method for aligning local equipment with reference values obtained elsewhere, or following a local change in equipment. The key is to measure a relatively small young adult group, identifying those lung function indices that need adaptation based on z-scores, in order to then obtain laboratory-specific reference values that can be applied over the entire age range.

I Say IOS You Say AOS: Comparative Bias in Respiratory Impedance Measurements.

BACKGROUND: The forced oscillation technique (FOT) measures respiratory impedance during normal tidal breathing and requires minimal patient cooperation. OBJECTIVE: To compare IOS and AOS devices in patients with asthma and COPD. METHODS: We compared two different FOT devices, namely impulse oscillometry using a loudspeaker (IOS: Jaeger Masterscreen) and airwave oscillometry using a vibrating mesh (AOS: Thorasys Tremoflo) for pre- and post-bronchodilator measurements in 84 patients with asthma and COPD. RESULTS: The overall pattern of measurement bias was for higher resistance with IOS and higher reactance with AOS, this being the case in asthma and COPD separately. There were small but significantly higher values using IOS for resistance at 5 Hz (R5) and 20(19) Hz (R20(19)). In converse, values for reactance at 5 Hz (X5), reactance area (AX) and resonant frequency (Fres) were significantly higher using AOS but to a much larger extent. The difference in AX between devices was more pronounced in COPD than in asthma. Salbutamol reversibility as % change was greater in asthma than COPD patients with AX but not FEV1. CONCLUSION: Our study showed evidence of better agreement for resistance than reactance when comparing IOS and AOS, perhaps inferring that AOS may be more sensitive at measuring reactance in patients with airflow obstruction.

[Design and Verification of a COPD Screening Equipment Based on Dual-differential Pressure Throttling Technique].

This study was to design a chronic obstructive pulmonary disease (COPD) screening equipment, based on the dual-differential pressure throttling technique. The technique combined a wide range, but low-resolution ratio sensor and a narrow range, but high-resolution ratio one. It can accurately detect the indexes of forced vital capacity (FVC), forced expiratory volume in one second (FEV1), one second rate(FEV1/FVC (%)), and achieve them in a low-cost way. The new designed machine will be compared with a British machine, named ML-3500. The correlations of FVC and FEV1 between new machine and ML-3500 were 0.998 and 0.999, respectively. The P values of paired t test of these two indexes were over 0.05. Bland-Altman analysis of FVC, FEV1 and FEV1/FVC (%) showed that more than 90% of the scatter points of the three parameters fell within the consistency interval. This machine can be used to accurately screen COPD and its low-cost would be advantage to promote in large population.

Underestimation of spirometry if recommended testing guidance is not followed.

Background: Lung function measured at work is used to make important employment decisions. Improving its quality will reduce misclassification and allow more accurate longitudinal interpretation over time. Aims: To assess the amount by which lung function (forced expiratory volume in 1 second [FEV1] and forced vital capacity [FVC]) values will be underestimated if recommended spirometry testing guidance is not followed. Methods: Lung function was measured in a population of workers. Knowledge of the final reproducible FEV1 and FVC for each worker allowed estimation of the underestimates that would have occurred if less forced manoeuvres than recommended had been performed. Results: A total of 667 workers (661 males, mean age 43 years, range 18-66) participated. Among them, 560 (84%) achieved reproducible results for both FEV1 and FVC; 470 (84%) of these did so after three technically acceptable forced expiratory manoeuvres, a cumulative total of 533 after four, 548 after five, 557 after six, 559 after seven and 560 after eight blows. If only one (or first two) technically acceptable blow(s) had been performed, mean underestimates were calculated for FEV1 of 115.1 ml (35.4 ml) and for FVC of 143.4 ml (42.3 ml). Conclusions: In this study, reproducible spirometry was achievable in most workers. Not adhering to standards underestimates lung function by clinically significant amounts.

Discrepancy between in vivo and in vitro comparisons of forced oscillation devices.

The forced oscillation technique (FOT) is an emerging clinical lung function test, with commercial devices becoming increasingly available. However comparability across existing devices has not been established. We evaluated in vivo and in vitro measurements made using three commercial devices against a custom-built device (WIMR): Resmon Pro Diary (Restech srl, Italy), tremoFlo C-100 (Thorasys Medical Systems, Canada), Jaeger Masterscope CT IOS (CareFusion, Hoechberg, Germany). Respiratory system resistance Rrs and reactance Xrs at 5 Hz were examined in twelve healthy subjects (mean age 33 ± 11 years, 7 males), and in two test standards of known resistance and reactance. Subjects performed three measurements during tidal breathing on the four devices in random order. Total, inspiratory and expiratory Rrs and Xrs were calculated and compared using one-way repeated measures ANOVA and Bonferroni post-hoc tests. Rrs did not differ between devices, with <10% deviation from predicted, except for the IOS device. With Xrs, similar values were seen between the WIMR and Resmon devices and between the tremoFlo and IOS devices. No differences were observed using test standards; deviation from theoretical value was <2% for resistance and <5% for reactance. The WIMR, tremoFlo and Resmon Pro but not IOS devices measure similar Rrs, whereas there was more disparity across devices in the estimation of Xrs parameters. The discrepancy between in vivo and in vitro measurements suggest that FOT validation procedures need to take into account the breathing pattern, either using biological controls or a breathing model.

Advances in Remote Respiratory Assessments for People with Chronic Obstructive Pulmonary Disease: A Systematic Review.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality. Advances in remote technologies and telemedicine provide new ways to monitor respiratory function and improve chronic disease management. However, telemedicine does not always include remote respiratory assessments, and the current state of knowledge for people with COPD has not been evaluated. OBJECTIVE: Systematically review the use of remote respiratory assessments in people with COPD, including the following questions: What devices have been used? Can acute exacerbations of chronic obstructive pulmonary disease (AECOPD) be predicted by using remote devices? Do remote respiratory assessments improve health-related outcomes? MATERIALS AND METHODS: The review protocol was registered (PROSPERO 2016:CRD42016049333). MEDLINE, EMBASE, and COMPENDEX databases were searched for studies that included remote respiratory assessments in people with COPD. A narrative synthesis was then conducted by two reviewers according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. RESULTS: Fifteen studies met the inclusion criteria. Forced expiratory volume assessed daily by using a spirometer was the most common modality. Other measurements included resting respiratory rate, respiratory sounds, and end-tidal carbon dioxide level. Remote assessments had high user satisfaction. Benefits included early detection of AECOPD, improved health-related outcomes, and the ability to replace hospital care with a virtual ward. CONCLUSION: Remote respiratory assessments are feasible and when combined with sufficient organizational backup can improve health-related outcomes in some but not all cohorts. Future research should focus on the early detection, intervention, and rehabilitation for AECOPD in high-risk people who have limited access to best care and investigate continuous as well as intermittent monitoring.

Use of pulmonary function test demographic data to identify high-risk patients for lung cancer screening.

Lung Cancer is the primary cause of cancer-related death in the United States. We have recognized a need for novel methods of identification and consideration of enrollment into a lung cancer screening program for those at the highest risk of lung cancer. Our primary goal was to determine if pulmonary function test (PFT) demographic data would be useful in identifying patients for lung cancer screening. We retrospectively reviewed PFTs performed at Lahey Hospital & Medical Center (LHMC) January 2012 through January 2013 and found that of patients identified as high risk of lung cancer, 89% had passed through our PFT lab but had not yet been screened. Investigation into the barriers of lung cancer screening to better understand how to increase appropriate enrollment then followed. A total of 3098 PFTs were reviewed from January 2012 through January 2013 and 634 patients (20%) were identified as high risk for lung cancer.  Of 634 patients, 70 (11%) were already in the LHMC lung cancer screening program. The remaining 564 patients (89%) were not enrolled, and of these, it was found that 292 patients identified as high risk for lung cancer represented missed opportunities for screening. The remaining 272 patients were appropriately not screened with the three most common reasons being prior imaging with positive finding, lung cancer within five years, and provider discussed but scan not yet performed. Appropriate enrollment in a lung cancer screening program may be increased with the careful use of demographic data obtained from a PFT lab.

[Psychophysiological monitoring of women teachers at the turn of the body of middle and old age.]

Objective - to create and hold psychophysiological monitoring elderly organism female teachers in the school year dynamics. The study was conducted with the participation of 30 female teachers aged 60-61 years at the beginning of the year (background level) and 5, and 9 months of teaching in the school. We studied 5-minute recording portions of the electrocardiogram using a program «Poly-Spectrum-Rhythm¼ (the limited liability company «Neurosoft¼); lung function - using the apparatus «Spirosoft-5000¼; psycho-emotional state of teachers in the dynamics of the school year - on the method of SUN (state of health, activity, mood). By the end of the school year biased increased sympathetic influence of the autonomic nervous system on the body of teachers that have been associated with some violation of the rhythmic activity of the heart on the background of destabilization of sinus rhythm and vegetative balance of the organism; indicators of forced expiratory volume in the first second the teachers were not significantly below baseline values, indicating a decline in the functional reserves of the respiratory system; there has been a strong tendency to deterioration of mental and emotional state of women teachers elderly. Consequently, the dynamics of the school year it is advisable to monitor the activities of the body of female teachers the elderly with a view to the possible prevention of various diseases and abnormalities in health status.

[Comparison of Different Mechanical Insufflator-Exsufflator Systems by Measurement of the Peak Exspiratory Flow (PEF)]. / Vergleich verschiedener mechanischer Hustenhilfen durch Messung der exspiratorischen Spitzenflüsse.

Background The management of pulmonary secretion in patients with respiratory muscle weakness using mechanical insufflator-exsufflator systems (MIE) is an established treatment option. There are significant differences in the efficiency of different devices in practical use. The intention of this study was to evaluate the peak exspiratory flow (PEF) values of different devices with and without use of equipment. Methods PEFs of ten MIE were investigated in vitro using different equipment. Results The efficiency of the devices showed significant differences. The use of two bacterial filters showed a significant reduction of 13 % compared to one filter, the use of a catheter mount revealed a significant reduction of 10 %, with an elbow connector additionally 15 %. With a commonly used equipment (1800 mm tube, one filter, catheter tube with elbow) there was a difference of 58 % between the devices Nippy (2,86 l/s) and Pulsar (1,2 l/s). Conclusion There are significant differences in PEF of different MIE and use of different equipment. That could be of therapeutic relevance. Further studies are needed to investigate the clinical relevance of these findings. Recommendations for the use of devices and equipment are necessary to ensure the efficacy of the elimination of pulmonary mucus.

Collapse phenomenon during Chartis collateral ventilation assessment.

Chartis is increasingly used for bronchoscopic assessment of collateral ventilation before endobronchial valve (EBV) treatment for severe emphysema. Its prognostic value is, however, limited by the airway collapse phenomenon. The frequency and clinical significance of the collapse phenomenon remain largely unknown.We performed a retrospective analysis of 92 patients undergoing Chartis evaluation under spontaneous breathing (n=55) or jet ventilation (n=37) from May 2010 to November 2013. Collateral ventilation status (positive/negative/collapse phenomenon/unclear) was reassessed and correlated with high-resolution computed tomography (HRCT) fissure analysis and clinical response.In the absence of the collapse phenomenon, the predictive value of Chartis measurements and HRCT fissural analysis was comparable. The collapse phenomenon was observed in 31.5% of all assessments, and was more frequent in lower lobes (44.9% versus 16.9% in upper lobes) and under jet ventilation (41.4% versus 22.1% under spontaneous breathing). 69.8% of lobes with the collapse phenomenon had complete fissures. Most patients with the collapse phenomenon in the target lobe and complete fissures treated with EBVs were responders (n=11/15). All valve-treated collapse phenomenon patients with fissure defects were nonresponders (n=3).In the absence of the collapse phenomenon Chartis measurement is reliable to predict response to valve treatment. In patients with the collapse phenomenon, treatment decisions should be based on HRCT detection of fissure integrity. Chartis assessment should be performed under spontaneous breathing.

Ensuring safety and functionality of electroglottography measurements during dynamic pulmonary MRI.

PURPOSE: To combine vocal tract measurements with dynamic MRI of the lungs to provide fundamental insights into the lung physiology during singing. METHODS: To analyze vocal fold oscillatory patterns during dynamic lung MRI, an electroglottography (EGG) system was modified to allow for simultaneous EGG measurements during MR image acquisitions. A low-pass filter was introduced to suppress residual radiofrequency (RF) coupling into the EGG signal. RF heating was tested in a gel phantom to ensure MR safety, and functionality of the EGG device was assessed in a volunteer experiment at singing frequencies from A5 to A3. In the recorded EGG signals, remaining RF interferences were removed by independent component analysis post processing, and standard EGG parameters such as fundamental frequency, contact quotient and jitter were calculated. In a second volunteer experiment, EGG recordings were compared with lung diameter measurements from 2D time-resolved trueFISP acquisitions. RESULTS: RF heating measurements resulted in less than 1.2°C temperature increase in the gel phantom. EGG parameters measured during MR imaging are within the range of ideal values. In the lung measurement, both the lung diameter and the EGG recordings could be successfully performed with only minimal interference. CONCLUSION: EGG recording is pos sible during dynamic lung MRI, and glottal activity can be studied safely at 1.5T. Magn Reson Med 76:1629-1635, 2016. © 2015 International Society for Magnetic Resonance in Medicine.

Reliability of an Electronic Inspiratory Loading Device for Assessing Pulmonary Function in Post-Stroke Patients.

BACKGROUND: The purpose of this study was to examine the inter- and intra-rater reliability of an electronic inspiratory loading device for the assessment of pulmonary functions: maximum inspiratory pressure, peak inspiratory flow, and vital capacity. MATERIAL/METHODS: Subjects were 50 patient volunteers in a rehabilitation hospital who had experienced their first episode of unilateral stroke with hemiparesis during the previous 6 months (26 men, 24 women; mean age [±SD], 55.96 [±12.81] years), with no use of medications that could induce drowsiness, evidence of restrictive lung disease, history of asthma, use of psychotropic drugs, or alcohol consumption habit. Maximum inspiratory pressure, peak inspiratory flow, and vital capacity for pulmonary functions were assessed using an electronic inspiratory loading device (PowerBreathe, K5, 2010) by 2 examiners, with patients in an unassisted sitting position, and 1 examiner re-assessed with same patients at the same time of a day after 1 week. Intra-class correlation coefficients were used to assess reliability. RESULTS: Intra-rater reliability ranged from intra-class correlation coefficients (ICCs)=0.959 to 0.986 in variables. For the inter-rater reliability between 2 examiners, the ICCs ranged from 0.933 to 0.985. Intra-rater and inter-rater reliability were good in variables (maximal inspiratory pressure, peak inspiratory flow, and vital capacity). CONCLUSIONS: The intra- and inter-examiner reliability of the pulmonary function measurements, maximum inspiratory pressure, peak inspiratory flow, and vital capacity, for the post-stroke patients was very high. The results suggest that the electronic inspiratory loading device would be useful for clinical rehabilitative assessment of pulmonary function.

Newborn manikin study shows that physicians often fail to detect correct lung compliance when using a self-inflating bag.

AIM: Recognising changes in lung compliance can help clinicians to adjust initial inflations during resuscitation at birth. We examined whether physicians sensed low and normal compliance with a self-inflating bag before and after an educational intervention that used a manikin connected to a newborn lung simulator. METHODS: We asked 43 physicians with neonatal duties to perform two low compliance ventilation attempts and two normal-compliance ventilation attempts in a randomised order at baseline and after the educational intervention, with 34 taking part in a retest three months later. RESULTS: The physicians correctly recognised low and normal compliance in 71% and 66% of the ventilations at baseline, 80% and 66% of the ventilations after the intervention and 74% and 81% at retest. Correct recognition of normal compliance improved from baseline to retest (p = 0.04). Ventilations in low- vs normal-compliance settings resulted in lower tidal volumes (4.4 vs 23.0 mL, p < 0.001), lower ventilation rates (42 vs 51, p < 0.001) and higher peak inflating pressure (35.2 vs 31.4 cmH2 O, p < 0.001). CONCLUSION: Around one in four physicians failed to recognise correct compliance levels when using a self-inflating bag and showed limited improvement after an educational intervention. Ventilations in a low-compliance setting resulted in suboptimal ventilation.

Closed system respirometry may underestimate tissue gas exchange and bias the respiratory exchange ratio (RER).

Closed respirometry is a commonly used method to measure gas exchange in animals due to its apparent simplicity. Typically, the rates of O2 uptake and CO2 excretion (VO2 and VCO2, respectively) are assumed to be in steady state, such that the measured rates of gas exchange equal those at tissue level. In other words, the respiratory gas exchange ratio (RER) is assumed to equal the respiratory quotient (RQ). However, because the gas concentrations change progressively during closure, the animal inspires air with a progressively increasing CO2 concentration and decreasing O2 concentration. These changes will eventually affect gas exchange causing the O2 and CO2 stores within the animal to change. Because of the higher solubility/capacitance of CO2 in the tissues of the body, VCO2 will be more affected than VO2, and we hypothesize therefore that RER will become progressively underestimated as closure time is prolonged. This hypothesis was addressed by a combination of experimental studies involving closed respirometry on ball pythons (Python regius) as well as mathematical models of gas exchange. We show that increased closed duration of the respirometer reduces RER by up to 13%, and these findings may explain previous reports of RER values being below 0.7. Our model reveals that the maximally possible reduction in RER is determined by the storage capacity of the body for CO2 (product of size and specific capacitance) relative to the respirometer storage capacity. Furthermore, modeling also shows that pronounced ventilatory and circulatory response to hypercapnia can alleviate the reduction in RER.

Technical note: A facility for respiration measurements in cattle.

A respiration system consisting of 4 climate-controlled chambers and 1 set of flowmeters and analyzers was constructed and validated. Each chamber had volume of 21.10m(3) (3.68×2.56×2.24m) and was made from steel with double-glazed windows on either side enabling visual contact between animals. The chambers are independently climate-controlled and can maintain temperature and relative humidity in a range from 5 to 45°C and 30 to 80%, respectively. A flow generator and mass flowmeter continuously pull air from each chamber and a slight negative pressure inside the chamber is ensured. Air from all chambers and ambient air share a common gas analysis and data acquisition system for monitoring O2, CO2, and CH4 concentrations over the measurement period, with the cycle time set to 20min. Analyzers are regularly calibrated and the chambers have mean recoveries of 99.0 and 98.0% for CO2 and CH4, respectively. The chambers are equipped with infrared cameras and electronic feed and water bins for intake measurements, as well as sensors for monitoring animal position and heart rate. Data acquisition and analysis software is used to calculate the rate of consumption of O2 and production of CO2 and CH4. The dynamic respiration measurements are integrated with feed intake data and other sensors. The daily gas exchanges are estimated by integration to determine methane emission and heat production. We conducted a trial with 12 lactating 3/4 Holstein × 1/4 Gyr crossbred dairy cows (6 multiparous and 6 primiparous) under 2 feeding regimens (ad libitum or restricted) to validate the system. Two 22-h respiration measurements were obtained from each cow. Restricted-fed cows showed lower values for milk yield, methane emission, and heat production compared with ad libitum-fed animals. We found no difference between groups for CH4 produced per kilogram of dry matter intake. Repeatability for CH4 emission and heat production was high (0.97 and 0.92, respectively). The respiration system described herein is a useful tool for measuring the dynamic and accumulated data of heat production, methane emission, and feed intake.