Respiratory Cycle Time Research Articles

Point-of-Care Echocardiography in the Difficult-to-Image Patient in the ICU: A Narrative Review.

The objective of this narrative review was to address common obstacles encountered in the ICU to acquiring quality and interpretable images using point-of-care echocardiography. Detailed searches were performed using PubMed and Ovid Medline using medical subject headings and keywords on topics related to patient positioning, IV echo contrast, alternative subcostal views, right ventricular outflow tract (RVOT) hemodynamics, and point-of-care transesophageal echocardiography. Articles known to the authors were also selected based on expert opinion. Articles specific to patient positioning, IV echo contrast, alternative subcostal views, RVOT hemodynamics, and point-of-care transesophageal echocardiography were considered. One author screened titles and extracted relevant data while two separate authors independently reviewed selected articles. Impediments to acquiring quality and interpretable images in critically ill patients are common. Notably, body habitus, intra-abdominal hypertension, dressings or drainage tubes, postoperative sternotomies, invasive mechanical ventilation, and the presence of subcutaneous emphysema or lung hyperinflation are commonly encountered obstacles in transthoracic image acquisition in the ICU. Despite these obstacles, the bedside clinician may use obstacle-specific maneuvers to enhance image acquisition. These may include altering patient positioning, respiratory cycle timing, expanding the subcostal window to include multilevel short-axis views for use in the assessment of RV systolic function and hemodynamics, coronal transhepatic view of the inferior vena cava, and finally point-of-care transesophageal echocardiography. Despite common obstacles to point-of-care echocardiography in critically ill patients, the beside sonographer may take an obstacle-specific stepwise approach to enhance image acquisition in difficult-to-image patients.

Predicting Inhaled Drug Dose Generated by Mesh Nebulizers.

Background: The lung dose of nebulized drugs for spontaneous breathing is influenced by breathing patterns and nebulizer performance. This study aimed to develop a system for measuring breath patterns and a formula for estimating inhaled drugs, and then to validate the hypothesized prediction formula. Methods: An in vitro model was first used to determine correlations among the delivered dose, breath patterns, and doses deposited on the accessories and reservoirs testing with a breathing simulator to generate 12 adult breathing patterns (n = 5). A pressure sensor was developed to measure breathing parameters and used along with a prediction formula that accounted for the initial charge dose, respiratory pattern, and dose on the accessory and reservoir of a nebulizer. Three brands of nebulizers were tested by placing salbutamol (5.0 mg/2.5 mL) in the drug holding chamber. Ten healthy individuals participated in the ex vivo study to validate the prediction formula. The agreement between the predicted and inhaled doses was analyzed using the Bland-Altman plot. Results: The in vitro model showed that the inspiratory time to total respiratory cycle time (Ti/Ttotal; %) was significantly directly correlated with the delivered dose among the respiratory factors, followed by inspiratory flow, respiratory rate, and tidal volume. The ex vivo model showed that Ti/Ttotal was significantly directly correlated with the delivered dose among the respiratory factors, in addition to the nebulization time and accessory dose. The Bland-Altman plots for the ex vivo model showed similar results between the two methods. Large differences in inhaled dose measured at the mouth were observed among the subjects, ranging from 12.68% to 21.68%; however, the difference between the predicted dose and inhaled dose was lower, at 3.98%-5.02%. Conclusions: The inhaled drug dose could be predicted with the hypothesized estimation formula, which was validated by the agreement between the inhaled and predicted doses of breathing patterns of healthy individuals.

Comparison of Changes in Chest Wall Mechanics and Respiratory Timing Between Patient-Controlled Epidural Analgesia and Intravenous Patient-Controlled Analgesia After Laparoscopic Gastrectomy: A Randomized Controlled Trial.

Upper abdominal surgery is associated with postoperative diaphragmatic dysfunction. Whether patient-controlled epidural analgesia (PCEA) is superior to intravenous patient-controlled analgesia (IV-PCA) in preventing postoperative diaphragmatic dysfunction is still unclear in laparoscopic gastric surgery. Sixteen patients undergoing laparoscopic gastrectomy randomly received either PCEA or IV-PCA. The primary outcomes were the change in chest wall mechanics and respiratory timing, measured by respiratory inductive plethysmography(Respitrace; Ambulatory Monitoring Inc., Ardsley, New York, United States) before and after surgery, and analyzed by a data acquisition system (PowerLab; ADInstruments, Dunedin, New Zealand). Inspiratory time (Ti), expiratory time (Te), total respiratory cycle time (Ttot), proportion of inspiratory time over total respiratory cycle time (Ti/Ttot), respiratory rate (RR), and abdominal contribution to tidal volume (AB/VT [%]) were calculated from the stored data. AB/VT, relative volume contribution of diaphragm to tidal breathing, represents an index of diaphragmatic function.Because the diaphragm is the main contributor to tidal volume, decreases in AB/VT indicate diaphragm dysfunction. Changes in outcomes over time between the two groups were analyzed using a linear mixed model, and two-sided p values < 0.05 were considered statistically significant. The secondary outcomes were postoperative pain score(visual analog scale (VAS)), bowel function recovery, and hospital stay duration. Postoperative AB/VT in the IV-PCA group was significantly decreased compared to preoperative levels. AB/VT in the PCEA group was significantly higher than the IV-PCA group on postoperative day (POD) 1. Change in AB/VT over time between the PCEA group and the IV-PCA group differed significantly (p = 0.01). A decrease of AB/VT during POD 1 to 3 was observed in the IV-PCA group but not in the PCEA group. As for respiratory timing, there were significant increases in RR with a reduction of Te and Ttot compared to preoperative levels on POD 1 in the PCEA group. There were significant decreases in RR and Ti/Ttot with an increase of Te and Ttot compared to preoperative levels on POD 1 in the IV-PCA group. There was a significant difference in the change of the Ttot over time between the two groups (p = 0.046). There were no significant differences in the changes of Te, Ti/Ttot, Ti, and RR over time between the two groups. There was no significant difference in VAS over time at rest and mobilization, recovery of bowel function, and hospital stay between the two groups. Continuous ropivacaine infusion with PCEA partially attenuated diaphragmatic dysfunction after laparoscopic gastrectomy, while pain relief by continuous intravenous administration of fentanyl could not attenuate diaphragmatic dysfunction. This suggests that PCEA might ameliorate postoperative diaphragmatic dysfunction after laparoscopic gastrectomy.

RESPIRATORY MECHANICS AND NEURAL RESPIRATORY DRIVE OF UNTREATED GASPING DURING CARDIAC ARREST IN A PORCINE MODEL.

Introduction: Although the effects on hemodynamics of gasping during cardiac arrest (CA) have received a lot of attention, less is known about the respiratory mechanics and physiology of respiration in gasping. This study aimed to investigate the respiratory mechanics and neural respiratory drive of gasping during CA in a porcine model. Method: Pigs weighing 34.9 ± 5.7 kg were anesthetized intravenously. Ventricular fibrillation (VF) was electrically induced and untreated for 10 min. Mechanical ventilation (MV) was ceased immediately after the onset of VF. Hemodynamic and respiratory parameters, pressure signals, diaphragmatic electromyogram data, and blood gas analysis data were recorded. Results: Gasping was observed in all the animals at a significantly lower rate (2-5 gaps/min), with higher tidal volume ( VT ; 0.62 ± 0.19 L, P < 0.01), and with lower expired minute volume (2.51 ± 1.49 L/min, P < 0.001) in comparison with the baseline. The total respiratory cycle time and the expiratory time tended to be lengthened. Statistically significant elevations in transdiaphragmatic pressure, the pressure-time product of diaphragmatic pressure, and the mean of root mean square diaphragmatic electromyogram values (RMSmean) were observed ( P < 0.05, P < 0.05, and P < 0.001, respectively); however, VT /RMSmean and transdiaphragmatic pressure/RMSmean were reduced at all time points. The partial pressure of oxygen showed a continuous decline after VF to reach statistical significance in the 10th minute (9.46 ± 0.96 kPa, P < 0.001), whereas the partial pressure of carbon dioxide tended to first rise and then fall. Conclusions: Gasping during CA was characterized by high VT , extremely low frequency, and prolonged expiratory time, which may improve hypercapnia. During gasping, increased work of breathing and insufficient neuromechanical efficacy of neural respiratory drive suggested the necessity of MV and appropriate management strategies for MV during resuscitation after CA.

A Preliminary Report on the Variation of Respiratory Blood Pressure during Sleep in Patients with Hypertension

ObjectiveExplore whether the blood pressure of hypertensive patients changes periodically with respiration.MethodsThis study analyzed 8 patients with hypertension without sleep apnea who performed cardiopulmonary exercise testing (CPET), polysomnography (PSG), continuous fingertip pulse wave and electrocardiogram (ECG), and compared with 8 normal subjects evaluated in the same period. Calculate the number of respiratory cycles (Bn), average respiratory cycle time (Bn‐T) and other respiratory parameters as well as systolic blood pressure (SBP), diastolic blood pressure (DBP), blood pressure variation cycles (BPV‐n), average blood pressure variation cycle time (BPV‐T) and other blood pressure variability parameters. Continuous variables within and between groups were compared by independent‐sample t test, and data calculated by different methods in the same group were compared by paired‐sample t test.ResultsThe core parameters of CPET such as peak oxygen uptake (72.82±10.07%Pred) and anaerobic threshold (59.69±6.66%Pred) of hypertensive patients without sleep apnea were significantly lower than those of normal subjects (P&lt;0.05). The fingertip pulse wave calculation of SBPV‐n (7000.25±1404.78) and DBPV‐n (6949.25±1407.98) in hypertensive patients were basically the same, similar to the results of normal subjects, and there was no statistically significant difference between the two groups (P&gt;0.05); SBPV‐T, DBPV‐T, SBPV rate and DBPV rate (4.34±0.72 s, 4.37±0.70 s, 14.22±2.39 bpm, 14.10±2.34 bpm) were not statistically different from normal subjects (P&gt;0.05); Bn/SBPV‐n (1.00±0.03) and Bn/DBPV‐n (1.01±0.02) are basically the same as normal subjects (P&gt;0.05), and both are close to 1.SBPV‐n (2464.75±1318.38) and DBPV‐n (936.00±132.18) calculated based on pulse transit time during sleep were significantly lower than the fingertip pulse wave calculation parameter (P&lt;0.01). The systolic blood pressure variation amplitude (2.96±0.83 mmHg) and diastolic blood pressure variation amplitude (2.57±0.38 mmHg) were greater than those of normal subjects, but the difference was not statistically significant.ConclusionThe variability of blood pressure during sleep in hypertensive patients without sleep apnea is similar to variability of respiration, and the change trend is consistent with normal subjects, both blood pressure variability is caused by respiration.

Breathing pattern and muscle activity using different inspiratory resistance devices in children with mouth breathing syndrome.

AimThe aim of this study was to evaluate the acute effects of different inspiratory resistance devices and intensity of loads via nasal airway on the breathing pattern and activity of respiratory muscles in children with mouth breathing syndrome (MBS).MethodsChildren with MBS were randomised into two groups based on inspiratory load intensity (20% and 40% of the maximal inspiratory pressure). These subjects were assessed during quiet breathing, breathing against inspiratory load via nasal airway and recovery. The measurements were repeated using two different devices (pressure threshold and flow resistance). Chest wall volumes and respiratory muscle activity were evaluated by optoelectronic plethysmography and surface electromyography, respectively.ResultsDuring the application of inspiratory load, there was a significant reduction in respiratory rate (p<0.04) and an increase in inspiratory time (p<0.02), total time of respiratory cycle (p<0.02), minute ventilation (p<0.03), tidal volume (p<0.01) and scalene and sternocleidomastoid muscles activity (root mean square values, p<0.01) when compared to quiet spontaneous breathing and recovery, regardless of load level or device applied. The application of inspiratory load using the flow resistance device showed an increase in the tidal volume (p<0.02) and end-inspiratory volume (p<0.02).ConclusionFor both devices, the addition of inspiratory loads using a nasal interface had a positive effect on the breathing pattern. However, the flow resistance device was more effective in generating volume and, therefore, has advantages compared to pressure threshold.

Robust, maintainable, emergency invasive mechanical ventilator.

To develop a simple, robust, safe and efficient invasive mechanical ventilator that can be used in remote areas of the world or war zones where the practical utility of more sophisticated equipment is limited by considerations of maintainability, availability of parts, transportation and/or cost. The device implements the pressure-controlled continuous mandatory ventilation mode, complemented by a simple assist-control mode. Continuous positive airway pressure is also possible. The consumption of compressed gases is minimized by avoiding a continuous flow of oxygen or air. Respiratory rates and inspiration/expiration time ratios are electronically determined, and an apnea/power loss alarm is provided. The pressure profiles were measured for a range of conditions and found to be adjustable within a ± 2.5cmH2O error margin and stable well within this range over a 41-hour period. Respiratory cycle timing parameters were precise within a few percentage points over the same period. The device was tested for durability for an equivalent period of four months. Chemical and biological tests failed to identify any contamination of the gas by volatile organic compounds or microorganisms. A ventilation test on a large animal, in comparison with a well established ventilator, showed that the animal could be adequately ventilated over a period of 60 minutes, without any noticeable negative aftereffects during the subsequent 24-hour period. This ventilator design may be viable, after further animal tests and formal approval by the competent authorities, for clinical application in the abovementioned atypical circumstances.

Coordination of Respiration, Swallowing, and Chewing in Healthy Young Adults.

Examining the coordination of respiration and swallowing is important for elucidating the mechanisms underlying these functions and assessing how respiration is linked to swallowing impairment in dysphagic patients. In this study, we assessed the coordination of respiration and swallowing to clarify how voluntary swallowing is coordinated with respiration and how mastication modulates the coordination of respiration and swallowing in healthy humans. Twenty-one healthy volunteers participated in three experiments. The participants were asked to swallow 3 ml of water with or without a cue, to drink 100 ml of water using a cup without breathing between swallows, and to eat a 4-g portion of corned beef. The major coordination pattern of respiration and swallowing was expiration–swallow–expiration (EE type) while swallowing 3 ml of water either with or without a cue, swallowing 100 ml of water, and chewing. Although cueing did not affect swallowing movements, the expiratory time was lengthened with the cue. During 100-ml water swallowing, the respiratory cycle time and expiratory time immediately before swallowing were significantly shorter compared with during and after swallowing, whereas the inspiratory time did not differ throughout the recording period. During chewing, the respiratory cycle time was decreased in a time-dependent manner, probably because of metabolic demand. The coordination of the two functions is maintained not only in voluntary swallowing but also in involuntary swallowing during chewing. Understanding the mechanisms underlying respiration and swallowing is important for evaluating how coordination affects physiological swallowing in dysphagic patients.

Escherichia Coli Induced Peritonitis Alters the Central Respiratory Network

Severe septic patients manifest respiratory failure and ventilator dependence, both of which we theorize relate to brainstem inflammation leading to dysfunction of the respiratory control network. Brainstem inflammation mirrors the systemic inflammation, associated with sepsis. Here, we hypothesize that dose dependent E. coli peritonitis induce neuroinflammation that alters the central respiratory network. For this AAALAC approved study, ventilatory pattern of awake pups (Sprague Dawley males, n=28, P24-P27) were recorded using whole-body plethysmography for 1h before (Baseline, Bsln) and 24h after implantation surgeries (T24). Fibrin clots containing either 5x106 (D5, n=10) or 2.5x106 (D2.5, n=9) or 0 (D0, n=9) E. coli cells were implanted in the peritoneal cavity. After 24h, ventilatory pattern was recorded and the animal immediately prepared for the in situ preparation where phrenic nerve (PNA), cervical vagus nerve (VNA), thoracic sympathetic chain (tSNA) activities, heart rate and perfusion pressure were recorded. Respiratory pattern was recorded for 10 min to assess differences in patterning between groups. Whole-body plethysmography revealed that 24h after surgery implantation only the group of D5 (TE (time of expiration) 0.24±0.03, p=0.005; TTOT (Total time of respiratory cycle) 0.40±0.02, p=0.008; fR (respiratory frequency) 155± 11, p=0.015) differed compared to D2.5 (TE 0.31±0.02; TTOT 0.50±0.02; fR 122±6) and D0 (TE 0.32±0.02; TTOT 0.505±0.03; fR121± 6). Although no significant changes for the nonlinear complex index (NLCI) were identified between the groups, NLCI trended upwards for both D2.5 (0.100±0.02) and D5 (0.106±0.02) when compared to D0 (0.064±0.01, p=0.136). In the in situ brainstem-spinal cord preparation both D2.5 (TPI (time of Post-inspiration) 2.89±0.40, p=0.002; TTOT 4.25±0.34, p=0.002; fR 14.8± 0.90, p=0.002) and D5 (TPI 3.01±0.16, p<0.001; TTOT 4.37±0.18, p=0.001; fR13.90± 0.50, p=0.004) differed from D0 (TPI 3.01±0.41; TTOT 5.98±0.39; fR 10.60± 0.80), but did not differ from each other. From this data, we conclude that E. coli peritonitis induce changes in breathing pattern that persist in the in situ preparation. Further increase in inoculate does not lead to increased disordered breathing.

Deficiency of Biogenic Amines Modulates the Activity of Hypoglossal Nerve in the Reserpine Model of Parkinson's Disease.

The underlying cause of respiratory impairments appearing in Parkinson’s disease (PD) is still far from being elucidated. To better understand the pathogenesis of respiratory disorders appearing in PD, we studied hypoglossal (HG) and phrenic (PHR) motoneuron dysfunction in a rat model evoked with reserpine administration. After reserpine, a decrease in the baseline amplitude and minute HG activity was noted, and no depressive phase of the hypoxic ventilatory response was observed. The pre-inspiratory time of HG activity along with the ratio of pre-inspiratory time to total respiratory cycle time and the ratio of pre-inspiratory to inspiratory amplitude were significantly reduced during normoxia, hypoxia, and recovery compared to sham rats. We suggest that the massive depletion of not only dopamine, but above all noradrenaline and serotonin in the brainstem observed in our study, has an impact on the pre-inspiratory activity of the HG. The shortening of the pre-inspiratory activity of the HG in the reserpine model may indicate a serious problem with maintaining the correct diameter of the upper airways in the preparation phase for inspiratory effort and explain the development of obstructive sleep apnea in some PD patients. Therapies involving the supplementation of amine depletion other than dopamine should be considered.

Assessment of diaphragm dysfunction during cardiac rehabilitation after heart surgery: the role of ultrasound imaging

Abstract Background Diaphragm dysfunction is a frequent and underdiagnosed complication of cardiac surgery. It can cause dyspnoea, decreased exercise performance and, in more severe cases, respiratory failure. Ultrasonography (US) is a valuable, non-invasive technique for the assessment of diaphragm function. Only few trials have been conducted using US to evaluate diaphragm functional recovery after cardiovascular rehabilitation (CR). Purpose The aim of the study was to assess with US the incidence of diaphragm dysfunction after heart surgery and to define the impact of an inpatient CR programme on diaphragm functional recovery. Methods We performed a single-centre prospective cohort study, enrolling 185 patients hospitalized in our CR unit: 99 patients underwent mitral valve repair or replacement, 28 tricuspid valve repair or replacement, 53 aortic valve replacement, 30 coronary artery bypass grafting, 59 combined surgery and 14 other surgical procedures. Diaphragm US was performed at admission and after 10 rehabilitative sessions. We assess the following parameters on quiet breathing: excursion, time of inspiration, time of a respiratory cycle and contraction velocity (slope) in M-mode on the right anterior subcostal projections and thickening fraction (TF) in B-mode on the right intercostal projections. TF was defined as [(thickness at end inspiration–thickness at end expiration)/thickness at end expiration]. Results The median excursion at admission was 1.6 cm. Patients with excursion &amp;lt;2 cm (lower limit for the general population) were considered with diaphragm dysfunction. Following cardiac surgery, the incidence of diaphragm dysfunction was 70.8%. Patients with excursion &amp;lt;2 cm at admission gained an important benefit from CR, with a significant improvement in TF (p&amp;lt;0.001), excursion (p&amp;lt;0.001), time of inspiration (p&amp;lt;0.001), time of a respiratory cycle (p&amp;lt;0.001) and slope (p&amp;lt;0.001). Conversely, in patients with excursion ≥2 cm there was no significant improvement in slope (p=0.539) and excursion (p=0.179). At the final assessment, diaphragm function recovered in 50.5% of the patients, whilst 49.5% had a failure of recovery (excursion relative change between admission and discharge &amp;lt;33%). The multivariate analysis identified combined surgery (OR 3.08; 95% CI 1.59–5.99, p=0.001) and post-surgical pneumothorax (OR 3.05; 95% CI 1.23–7.55, p=0.036) as independent predictors of failure of diaphragm function recovery. Conclusions US might be a valuable tool for initial and follow-up assessment of patients after cardiac surgery. CR has been shown to be an effective strategy to improve diaphragm parameters in patients with post-surgical dysfunction. Patients undergoing combined surgery or developing post-surgical pneumothorax might benefit from a personalised rehabilitation programme to improve diaphragm function. Funding Acknowledgement Type of funding source: None

Robust Deep Learning Framework For Predicting Respiratory Anomalies and Diseases.

This paper presents a robust deep learning framework developed to detect respiratory diseases from recordings of respiratory sounds. The complete detection process firstly involves front end feature extraction where recordings are transformed into spectrograms that convey both spectral and temporal information. Then a back-end deep learning model classifies the features into classes of respiratory disease or anomaly. Experiments, conducted over the ICBHI benchmark dataset of respiratory sounds, evaluate the ability of the framework to classify sounds. Two main contributions are made in this paper. Firstly, we provide an extensive analysis of how factors such as respiratory cycle length, time resolution, and network architecture, affect final prediction accuracy. Secondly, a novel deep learning based framework is proposed for detection of respiratory diseases and shown to perform extremely well compared to state of the art methods.

Bronchodilation Increases Estimated Ventilatory Capacity In Children With Mild Asthma

PURPOSE: Children with asthma experience reduced maximal expiratory flows, which can decrease ventilatory capacity and increase ventilatory limitations during exercise; however, the effects of mid-flow bronchodilation on these variables are underappreciated. The purpose of this study was to examine the effect of bronchodilation on ventilatory capacity and ventilatory limitations during a maximal exercise test. METHODS: Nine children with mild asthma (7 boys, 10±1 yr, BMI percentile: 66±30, forced expiratory volume in 1s, FEV1: 106±24 %predicted, Range 78-144) completed spirometry before and after 360μg of albuterol. On a separate visit, they completed an incremental exercise test to exhaustion. Estimated ventilatory capacity was calculated using the volume time curve from estimated maximal tidal volume (FVC/2) and estimated maximal total respiratory cycle time (2×FET25-75%) both before and after bronchodilator. Ventilatory limitation was defined as <10% of breathing reserve (Estimated ventilatory capacity - maximum minute ventilation). RESULTS: Estimated ventilatory capacity increased by 16% after bronchodilator (60±23 vs. 69±27 L/min; p=0.013). Measured maximal tidal volume was lower than estimated (1.12±0.32 vs. 1.33±0.25, p=0.002) but measured maximal total respiratory cycle time (TTot) was not different from estimated (1.41±0.36 vs. 1.47±0.46, p=0.792). In a subset of seven children who received 180μg albuterol before the incremental test, five would have been ventilatory limited (i.e., <10%breathing reserve) at maximal exercise using “before bronchodilator” estimated ventilatory capacity (breathing reserve range: -61 to +9%). However, only one child was ventilatory limited at maximal exercise using “after bronchodilator” estimated ventilatory capacity. CONCLUSIONS: Bronchodilator administration prior to maximal exercise testing may be necessary to increase estimated ventilatory capacity and reduce ventilatory limitations even in children with mild asthma.

Cardiorespiratory and Vascular Variability Analysis to Classify Patients with Ischemic and Dilated Cardiomyopathy.

Heart diseases are the leading cause of death in developed countries. Ascertaining the etiology of cardiomyopathies is still a challenge. The objective of this study was to classify cardiomyopathy patients through cardio, respiratory and vascular variability analysis, considering the vascular activity as the input and output of the baroreflex response. Forty-one cardiomyopathy patients (CMP) classified as ischemic (ICM, 24 patients) and dilated (DCM, 17 patients) were analyzed. Thirty-nine elderly control subjects (CON) were used as reference. From the electrocardiographic, respiratory flow, and blood pressure signals, following temporal series were extracted: beat-to-beat intervals (BBI), total respiratory cycle time series (TT), and end- systolic (SBP) and diastolic (DBP) blood pressure amplitudes, respectively. Three-dimensional representation of the cardiorespiratory and vascular activities was characterized geometrically, by fitting a polygon that contains 95% of data, and by statistical descriptive indices. The best classifiers were used to build support vector machine models. The optimal model to classify ICM versus DCM patients achieved 92.7% accuracy, 94.1% sensitivity, and 91.7% specificity. When comparing CMP patients and CON subjects, the best model achieved 86.2% accuracy, 82.9% sensitivity, and 89.7% specificity. These results suggest a limited ability of cardiac and respiratory systems response to regulate the vascular variability in these patients.

New physiological bench test reproducing nocturnal breathing pattern of patients with sleep disordered breathing.

Previous studies have shown that Automatic Positive Airway Pressure devices display different behaviors when connected to a bench using theoretical respiratory cycle scripts. However, these scripts are limited and do not simulate physiological behavior during the night. Our aim was to develop a physiological bench that is able to simulate patient breathing airflow by integrating polygraph data. We developed an algorithm analyzing polygraph data and transformed this information into digital inputs required by the bench hardware to reproduce a patient breathing profile on bench. The inputs are respectively the simulated respiratory muscular effort pressure input for an artificial lung and the sealed chamber pressure to regulate the Starling resistor. We did simulations on our bench for a total of 8 hours and 59 minutes for a breathing profile from the demonstration recording of a Nox T3 Sleep Monitor. The simulation performance results showed that in terms of relative peak-valley amplitude of each breathing cycle, simulated bench airflow was biased by only 1.48% ± 6.80% compared to estimated polygraph nasal airflow for a total of 6,479 breathing cycles. For total respiratory cycle time, the average bias ± one standard deviation was 0.000 ± 0.288 seconds. For patient apnea events, our bench simulation had a sensitivity of 84.7% and a positive predictive value equal to 90.3%, considering 149 apneas detected both in polygraph nasal simulated bench airflows. Our new physiological bench would allow personalizing APAP device selection to each patient by taking into account individual characteristics of a sleep breathing profile.

Impact of moderate-severe persistent allergic rhinitis on thoraco-abdominal kinematics and respiratory muscle function

Objective: To assess thoraco-abdominal kinematics, respiratory muscle strength and electromyographic activity of the diaphragm (EAdi) in moderate-severe allergic rhinitis (AR) patients. Methods: A cross-sectional study involving 40 individuals (20 in the AR group) and 20 in the control group [CG]) was conducted. Ventilatory pattern and chest wall volume distribution (optoelectronic plethysmography), respiratory muscle strength (manovacuometry and sniff nasal inspiratory pressure [SNIP]), and EAdi were assessed in both groups. Results: The AR patients had impaired thoraco-abdominal kinematics (reduced total chest wall volume) (p = 0.004), lower values of total respiratory cycle time (p = 0.014) and expiratory time (p = 0.006). They also presented an increase of percentage contribution of the abdominal rib cage (p = 0.475) and respiratory rate (p = 0.019). A positive correlation among pulmonary rib cage tidal volume and MIP (r = 0.544; p < 0.001), SNIP (r = 0.615; p < 0.001), and MEP (r = 0.604; p < 0.001) was observed. After adjusting for age, BMI and gender through multivariate analysis, the individuals with AR presented lower values ​​of MIP (β = −24.341; p < 0.001), MEP (β = −0.277; p < 0.001), SNIP (β = −34.687; p < 0.001) and RMS (β = −0.041; p = 0.017). Conclusions: The individuals with moderate-severe persistent AR had worse respiratory muscle strength, diaphragm activation and chest wall volume distribution with a higher abdominal contribution to tidal volume than the control group. These findings reinforce the notion that the upper and lower airways work in an integrated and synergistic manner.

Pulmonary Responses During Exercise On Dryland Vs. Immersible Ergocycle

Water immersion can affect respiratory responses during exercise relative to exercise on dry land. Exercise training in an aquatic environment has added benefits relative to training on land, improving central hemodynamic responses as stroke volume (SV), cardiac output (Q) and heart rate recovery (HRR) as well as increasing cerebrovascular blood flow, relative to land-based exercise of a similar intensity, in healthy humans. PURPOSE: We sought to compare pulmonary responses during an incremental exercise done on immersible ergocycle (IE) vs dryland ergocycle (DE) at the same external power output (Pext). METHODS: Ten (10) young healthy subjects (Age: 31±9 years; BMI: 23.3±1.9 kg/m2) performed incremental exercise tests on IE at chest level immersion and DE at equal external power output (Pext). Pulmonary responses were measured and Pext on IE was calculated according to the general fluid equation Fd = ½ρ Av2Cd. Tangential speed of the pedaling mechanism was calculated by 2 πr (rpm), 2 π (r/2)(rpm) and ω2 π (r/2)/360°(rpm), for pedals, paddles-rods, and legs, respectively, as used in previous studies. RESULTS: VO2 (p=0.0087) and VCO2 (p=0.0138) were significantly lower during exercise on IE at every stage of the incremental test relative to DE. No differences were detected between IE and DE for respiratory exchange ratio (RER) ventilation (VE), breathing frequency (f), tidal volume (VT), fraction of expired O2 and CO2 (FetO2 and FeCO2, respectively), time of inspiration (Ti), time of expiration (Te), time of respiratory cycle (Ttot), duty cycle (Ti/Ttot), and partial pressure of end tidal O2 and CO2 (PetO2 and PetCO2, respectively). CONCLUSIONS: Exercise during water immersion results in a significantly lower mean VO2, relative to a land exercise of equivalent power output. No differences were detected in the respiratory parameters suggesting that the lower VO2 reached with IE is not attributed to changes in ventilation, but rather to central or peripheral convection (cardiac output) or diffusion (capillary O2 extraction) factors. We have previously shown that hemodynamic factors (convection) are modestly improved, but not sufficiently to explain the large gap in VO2 between IE and DE. We hypothesize that diffusion is improved by an unknown mechanism that remains to be explained.

Модель обработки массива экспериментальных данных по определению временной структуры респираторного цикла

Quantitative assessment of the duration of respiratory cycle time pauses involves much difficulties. Qualitative evaluation results are only found in the literature. For obtaining quantitative assessments, a model for processing an array of experimental information that refines the respiratory cycle temporal structure is considered. The aim of the study is to develop a model for determining the average quantitative indicators characterizing the duration of respiratory cycle time pauses proceeding from an array of experimental data for the studied groups of individuals, and to carry out a comparison between the estimated respiratory cycle time pauses of a healthy person and those of an ill person. Establishing the respiratory cycle structure in terms of the duration of time pauses is the basis for defining certain diagnostic procedures on determining such factors as the type and frequency of breathing in accordance with the disease nosology, significant parameters from which the therapy procedure can be determined; and the ratio of inspiratory and expiratory pauses at a fixed duration of the time period.

Effects of detraining on breathing pattern and ventilatory efficiency in young soccer players.

This study investigated the effects of detraining on breathing pattern. The aim of this study was to evaluate the effect of a six-week detraining period on breathing patterns and ventilatory efficiency. Fourteen young soccer players were evaluated at the end of a competitive season and after a six-week detraining period. Assessment of respiratory efficiency was based on VE/VCO2 slope changes below 70% of exercise intensity. All participants underwent twice an incremental graded exercise test up to exhaustion. No differences in breathing frequency and inspiratory time/total time ratio (Ti/Ttot) were found after detraining (P>0.05). Differences in tidal volume (VT), VT/Ti quotient and VE were significant (P<0.05) at between 40 to 100% of exercise intensity. The VE/VCO2 slope did not change (P>0.05) during a postdetraining maximal incremental test. A six-week detraining period causes changes in inspiratory flow but does not affect the inspiratory time/total respiratory cycle time ratio. The overall ventilatory efficiency of the respiratory system remains constant and is not affected by detraining.

SU‐F‐T‐541: Impact of VMAT Dose Calculations with Respiratory Movements in Lung

Purpose:To evaluate dose impact due to respiratory movements for volumetric modulated arc therapy (VMAT) in lung, using deformation technique.Methods:The dose impact due to respiratory movements was evaluated for VMAT in lung. VMAT dose distributions were calculated with 4D‐CT images for a 3‐D dynamic lung phantom and seven patients. First, one‐arc VMAT dose distributions were calculated at the reference phase (the maximum of expiratory phase) using the Varian Eclipse (ver.10) treatment planning system. All VMAT were planned with 48Gy for 4 fractions. The VMAT dose distributions were divided into 88 control points (CPs) and were assigned to each one of ten phases divided through one respiratory cycle time. Next, the dose distributions were recalculated at each phase and were deformed at the reference phase using DIRART ver.1.0a and Velocity AI ver.3.1 software. The deformed dose distributions were summed up. Finally, VMAT dose distributions with respiratory movements were evaluated from dose volume histograms (DVHs).Results:VMAT dose distributions deformed by DIRART and the Velocity AI in the phantom study agreed within 2% with that of the reference phase for 95% of GTV (D95). In the patient study, deformed VMAT dose distributions decreased up to 4.15% and 3.46% for DIRART and Velocity AI, respectively. The maximum dose of GTV (Dmax) tended to be higher with increasing tumor movements. In constant, D95 for DVHs decreased with increasing tumor movements. The discrepancy in the VMAT dose distributions deformed by two software depended on specific properties of respective algorithms and parameters.Conclusion:Respiratory movements impact on the dose distributions for GTV. The Dmax may relate with amplitude of tumor movements.