Total Breath Time Research Articles

Examination of changes in the breathing intolerance index to determine the respiratory support needs of very low birth weight infants.

The breathing intolerance index (BITI) is used to evaluate respiratory muscle tolerance. The higher the ratio of the inspiratory time to the total breathing time and the ratio of the tidal volume to the vital capacity, the more easily the respiratory muscles become fatigued. The BITI is high with chronic respiratory failure, and values of 0.15 or more indicate the need for assisted ventilation. This study aimed to examine the changes in the BITI of very low birth weight infants (VLBWIs) and determine whether it is possible to use the BITI as an objective indicator of the timing of noninvasive respiratory support (NRS) withdrawal. VLBWIs admitted to our neonatal intensive care unit between July 2020 and July 2022 under NRS at 36 weeks' postmenstrual age (PMA). If the BITI was less than 0.15, then we attempted to determine whether NRS could be withdrawn. Sixteen infants with a median gestational age and birth weight of 30.9 weeks and 1249 g, respectively, were eligible. The median PMA at the time of the first examination was 36.6 weeks. The BITI of two VLBWIs was less than 0.15. For 11 of the other VLBWIs, the BITI decreased over time to less than 0.15 at 39 weeks' PMA. After confirming that the BITI was less than 0.15, weaning from NRS was attempted. Weaning from NRS was possible except one VLBWI. The BITI can help evaluate respiratory tolerance and could be an objective indicator of the timing of NRS withdrawal.

A new tidal breathing measurement device detects bronchial obstruction during methacholine challenge test

PurposeBronchial hyperresponsiveness (BHR), a hallmark of bronchial asthma, is typically diagnosed through a methacholine inhalation test followed by spirometry, known as the methacholine challenge test (MCT). While spirometry relies on proper patients' cooperation and precise execution of forced breathing maneuvers, we conducted a comparative analysis with the portable nanomaterial-based sensing device, SenseGuard™, to non-intrusively assess tidal breathing parameters. Materials and methodsIn this prospective study, 37 adult participants with suspected asthma underwent sequential spirometry and SenseGuard™ measurements after inhaling increasing methacholine doses. ResultsAmong the 37 participants, 18 were MCT responders, 17 were non-responders and 2 were excluded due to uninterpretable data. The MCT responders exhibited a significant lung function difference when comparing the change from baseline to maximum response. This was evident through a notable decrease in forced expiratory volume in 1 ​s (FEV1) levels in spirometry, as well as in prominent changes in tidal breathing parameters as assessed by SenseGuard™, including the expiratory pause time (Trest) to total breath time (Ttot) ratio, and the expiratory time (Tex) to Ttot ratio. Notably, the ratios Trest/Ttot (∗p ​= ​0.02), Tex/Ttot (∗p ​= ​0.002), and inspiratory time (Tin) to Tex (∗p ​= ​0.04) identified MCT responders distinctly, corresponding to spirometry (∗p ​< ​0.0001). ConclusionsThis study demonstrates that tidal breathing assessment using SenseGuard™ device reliably detects clinically relevant changes of respiratory parameter during the MCT. It effectively distinguishes between responders and non-responders, with strong agreement to conventional spirometry-measured FEV1. This technology holds promise for monitoring clinical respiratory changes in bronchial asthma patients pending further studies.

The impact of antenatal and postnatal indoor air pollution or tobacco smoke exposure on lung function at 3 years in an African birth cohort.

Indoor air pollution (IAP) and tobacco smoke exposure (ETS) are global health concerns contributing to the burden of childhood respiratory disease. Studies assessing the effects of IAP and ETS in preschool children are limited. We assessed the impact of antenatal and postnatal IAP and ETS exposure on lung function in a South African birth cohort, the Drakenstein Child Health Study. Antenatally enrolled mother-child pairs were followed from birth. Lung function measurements (oscillometry, multiple breath washout and tidal breathing) were performed at 6 weeks and 3 years. Quantitative antenatal and postnatal IAP (particulate matter [PM10 ], volatile organic compounds [VOC]) and ETS exposures were measured. Linear regression models explored the effects of antenatal and postnatal exposures on lung function at 3 years. Five hundred eighty-four children had successful lung function testing, mean (SD) age of 37.3 (0.7) months. Exposure to antenatal PM10 was associated with a decreased lung clearance index (p < 0.01) and postnatally an increase in the difference between resistance at end expiration (ReE) and inspiration (p = 0.05) and decrease in tidal volume (p = 0.06). Exposure to antenatal VOC was associated with an increase in functional residual capacity (p = 0.04) and a decrease in time of expiration over total breath time (tE /tTOT ) (p = 0.03) and postnatally an increase in respiratory rate (p = 0.05). High ETS exposure postnatally was associated with an increase in ReE (p = 0.03). Antenatal and postnatal IAP and ETS exposures were associated with impairment in lung function at 3 years. Strengthened efforts to reduce IAP and ETS exposure are needed.

Changes in tidal breathing biomarkers as indicators of treatment response in AECOPD patients in an acute care setting

PurposeAcute exacerbation of chronic obstructive pulmonary disease (AECOPD) is a complication of COPD that typically necessitates intensified treatment and hospitalization. It is linked to higher morbidity, mortality and healthcare spending. Assessment of therapy response for AECOPD is difficult due to the variability of symptoms and limitations in current measures. Hence, there is a need for new biomarkers to aid in the management of AECOPD in acute care settings. Materials and methodsFifteen hospitalized AECOPD patients (GOLD 3–4) were enrolled in this study. Treatment response was assessed daily through clinical evaluations and by monitoring tidal breathing biomarkers (respiratory rate [RR], expiratory time [Tex], inspiratory time [Tin], expiratory pause [Trst], total breath time [Ttot]), using a novel, wearable nanosensor-based device (SenseGuard™). ResultsPatients who showed significant clinical improvement had substantial changes in ΔTex/Ttot (+14%), ΔTrst/Ttot (−18%), and ΔTin/Tex (+0.09), whereas patients who showed mild or no clinical improvement had smaller changes (+5%, +3%, and −0.03, respectively). Linear regression between change in physician's assessment score and the median change in tidal breathing parameters was significant for Tin/Tex (R2 ​= ​0.449, ∗p ​= ​0.017), Tex/Ttot (R2 ​= ​0.556, ∗p ​= ​0.005) and Trst/Ttot (R2 ​= ​0.446, ∗p ​= ​0.018), while no significant regression was observed for RR, Tin/(Trst ​+ ​Tex) and Tin/Ttot. ConclusionsOur study demonstrates the potential of the SenseGuard™ to monitor treatment response in AECOPD patients by measuring changes in tidal breathing biomarkers, which were shown to be associated with significant changes in the patients' respiratory condition as evaluated by physicians. However, further large-scale clinical studies are needed to confirm these findings.

Influence Of Different Exercise Intensities On The Respiratory Function And Breathing Pattern During Underwater Cycling

Aquatic cycling is gaining a popularity and its physiological responses have been studied in previous research. Exercise intensity during aquatic cycling can be adjusted by changing the cadence and water resistance offered by the paddles on the pedaling mechanism. However, it remains unclear what level of exercise intensity would have a positive effect on the respiratory function. PURPOSE: he purpose of this study was to investigate the association between exercise intensity during aquatic cycling and respiratory function. METHODS: Twelve healthy men performed 15 minutes of aquatic cycling with load (LC) and no load (NLC) conditions. In both conditions, after sitting rest in water for 4 minutes, participants began cycling at 30 rpm, and the cadence was increased 15 rpm every 5 minutes. In LC, 3 paddles were attached to the wheel of stationary bicycle to increase water resistance against pedals. Using a spirometry, respiratory function and respiratory muscle pressure were measured before and after exercise. Breathing pattern was measured by an expiratory gas analyzer during exercise. RESULTS: During aquatic cycling, oxygen uptake (VO2) was significantly higher in LC than NLC (all p < 0.05) and progressively increased from 30 rpm to, 45 and, 60 rpm in both LC and NLC (all p < 0.05). At 60 rpm, respiratory rate was significantly higher (27 ± 3 vs. 23 ± 3 bpm, p < 0.05) and total breathing time, inspiratory time, and expiratory time were significantly lower in LC than NLC (2.3 ± 0.3 vs. 2.7 ± 0.4 sec, 1.0 ± 0.1 vs. 1.2 ± 0.1 sec, 1.3 ± 0.2 vs. 1.5 ± 0.2 sec, respectively, all p < 0.05). While inspiratory volume was significantly higher at 45 and, 60 rpm (855 ± 63 vs. 698 ± 66 ml, 1242 ± 107 vs. 896 ± 84 ml, all p < 0.05), expiratory volume was significantly higher at 30, 45, and 60 rpm (621 ± 76 vs. 576 ± 58 ml, 833 ± 63 vs. 692 ± 67 ml, 1225 ± 105 vs. 884 ± 76 ml, all p < 0.05) in LC than NLC. CONCLUSIONS: These results suggest that inspiratory and expiratory volumes progressively increase with higher cadence during aquatic cycling. But, inspiratory and expiratory times may not change until a higher intensity. Therefore, respiratory muscles may be recruited with increased ventilatory demand in LC compared with NLC.

Ultrasound diaphragmatic manual and semi-automated motion measurements: Application in simulated and in vivo data of critically ill subjects

Background and ObjectiveUltrasound diaphragmatic muscle motion characteristics may provide useful information about normal or abnormal diaphragmatic function and indicate diaphragmatic weakness, or paralysis. In the present work we propose and evaluate an integrated semi-automated analysis system for the quantitative analysis of ultrasonic motion from ultrasound diaphragmatic videos. MethodsThe proposed system was evaluated in simulated videos and in 13 patients, four of whom patients were mechanically ventilated. The major steps of the methodology were as follows: video normalization, despeckle filtering, generation of an M-Mode image, snakes segmentation, and motion measurements. ResultsThe following manual (-/) vs semi-automated (/-), (median±IQR) measurements, which are routinely carried out by the experts, for assessing the severity of the disease, were computed. For the simulated videos the diaphragmatic excursion was 1.80±0.00 cm / 1.76±0.03 cm. For all the real ultrasound videos investigated in this study the following measurements were computed: (i) diaphragmatic excursion: 0.84±0.15 cm / 0.83±0.14 cm, (ii) inspiration time (Tinsp): 0.71±0.18 sec / 0.70±0.15 sec, (iii) total breathing time for one cycle (Ttot): 1.71±0.37 sec / 1.67±0.37 sec, (iv) diaphragmatic curve slope: 1.29±0.36 cm/sec / 1.27±0.36 cm/sec, and (v) relaxation rate (RR): 0.82±0.17 cm/sec / 0.82±0.18 cm/sec. ConclusionsManual and semi-automated measurements were very close with non-statistical significant differences and strong correlations between them. It is anticipated that the proposed system might be useful in the clinical practice in the assessment and follow up of patients with diaphragmatic weakness or paralysis and aid in the separation of normal and abnormal diaphragmatic motion. Further validation and additional experimentation in a larger sample of videos and different patient groups is required.

Inspiratory Resistive (R) Load Endurance Testing in Normal Healthy Adults: Load compensation, effort sensation and affective perception.

Increased respiratory load is a key feature in various respiratory diseases, accompanied by ventilatory compensation, cognitive awareness and affective perception. Loaded breathing can occur from minutes to days requiring the individual to modulate their breathing pattern to maintain alveolar ventilation, minimize work of breathing and minimize aversive load sensations. Increased inspiratory load is associated with cognitive sensation of the load magnitude and affective escape behavior to reduce the aversive perception of loaded breathing. During exacerbations of lung diseases, an individual often must compensate for increased loads that exceed their ability to sustain alveolar ventilation. Yet it is difficult to assess the capacity of an individual to adapt to an increased respiratory load. The aim of this study was to determine the ventilatory and perceptual endurance response to a high magnitude inspiratory R load applied for 10 minutes. It was hypothesized that some individuals would be able to complete the task and other individuals would terminate the task early. It was further hypothesized that early termination of the task would be due to increased aversive affective awareness. Healthy participants were tested while breathing through a non‐rebreathing circuit with an inspiratory load R=50 cmH20/L/s. The individual respired with no‐load for 1 minute, then the load was applied for 10 minutes, followed by 1 minute of no‐load breathing. The subject was instructed that they could terminate the task at any time by removing the mouthpiece. Subjects estimated their perceived load intensity (MEInt) and unpleasantness (MEUn) every minute. Fear (MEF) was estimated before and after the load trial. Two of six subjects terminated the trial early. The ventilatory load pattern for all subjects was a load dependent increased maximum inspiratory pressure, decreased airflow, increased inspiratory duration and unchanged expiratory duration, increased total breath time, increased inspiratory volume, unchanged minute ventilation, PCO2 and PO2. The MEInt increased with the onset of the load, was constant throughout the task and was the same for individuals that completed and stopped the task. MEUn increased with the load onset with greater MEUn for subjects that stopped early. The individuals that stopped early had equal MEF at task onset but much greater MEF when the task stopped. The results suggest that inspiratory R50 endurance capacity is decreased in individuals with greater negative affective responses to high magnitude loaded breathing.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Respiratory load compensation and perception during 10‐breath sustained inspiratory resistive loading in normal subjects

Increased load on the respiratory system is a key feature in various respiratory diseases, accompanied by ventilatory compensatory behavior and breathlessness. This increased inspiratory load is often prolonged, ranging from minutes to days, and requires the individual to adjust their breathing pattern to sustain alveolar ventilation and minimize the work of breathing, i.e. load compensation. Experimentally, this is often studied by breathing through resistive (R) loads. Most prior load compensation studies have used single breath loads within a range of adaptability for most individuals (0–40 cmH2O/l/s) to determine the load compensation mechanisms. However, during exacerbations of lung diseases, the individual must load compensate for multiple breaths against increasing load magnitudes that may exceed their ability to sustain alveolar ventilation. The aim of this study was to investigate load compensation in normal subjects when breathing for multiple breaths (10) through loads of increasing magnitudes greater than their expected ability to sustain alveolar ventilation. A threshold for load decompensation was hypothesized. Healthy participants were tested while breathing through a circuit with inspiratory flow‐resistive loads (R's: 0–100 cmH20/L/s). The loads were presented in random block order, each for 10 consecutive breaths and separated by unloaded breathing periods. The loads were presented in 2 trials, 2 times each per trial. Subjects estimated their perceived load intensity in one trial and unpleasantness in the other trial. A load compensation index (LCI) was calculated using breath phase duration and airflow. For R=0–25 cmH2O/L/s, respiratory load pattern was a load magnitude dependent increased maximum inspiratory pressure, decreased airflow, increased inspiratory duration and decreased expiratory duration. This resulted in a relatively constant total breath time, inspiratory volume, minute ventilation, PCO2, PO2 and LCI. However, decompensation was observed for R50 and R100 leading to declining minute ventilation and LCI. The results suggest, however, that increasing the duration of the R=50–100 load presentations would likely lead to hypoventilation and respiratory failure. The perception of inspiratory R load intensity and unpleasantness increased with load magnitude. The results suggest that high magnitude loads and/or long durations of loaded breathing result in increased affective response and decompensating respiratory pattern indicating that the individual is no longer able to sustain ventilation under these conditions.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Evaluation of the agreement of tidal breathing parameters measured simultaneously using pneumotachography and structured light plethysmography.

Structured light plethysmography (SLP) is a noncontact, noninvasive, respiratory measurement technique, which uses a structured pattern of light and two cameras to track displacement of the thoraco–abdominal wall during tidal breathing. The primary objective of this study was to examine agreement between tidal breathing parameters measured simultaneously for 45 sec using pneumotachography and SLP in a group of 20 participants with a range of respiratory patterns (“primary cohort”). To examine repeatability of the agreement, an additional 21 healthy subjects (“repeatability cohort”) were measured twice during resting breathing and once during increased respiratory rate (RR). Breath‐by‐breath and averaged RR, inspiratory time (tI), expiratory time (tE), total breath time (tTot), tI/tE, tI/tTot, and IE50 (inspiratory to expiratory flow measured at 50% of tidal volume) were calculated. Bland–Altman plots were used to assess the agreement. In the primary cohort, breath‐by‐breath agreement for RR was ±1.44 breaths per minute (brpm). tI, tE, and tTot agreed to ±0.22, ±0.29, and ±0.32 sec, respectively, and tI/tE, tI/tTot, and IE50/IE50SLP to ±0.16, ±0.05, and ±0.55, respectively. When averaged, agreement for RR was ±0.19 brpm. tI, tE, and tTot were within ±0.16, ±0.16, and ±0.07 sec, respectively, and tI/tE, tI/tTot, and IE50 were within ±0.09, ±0.03, and ±0.25, respectively. A comparison of resting breathing demonstrated that breath‐by‐breath and averaged agreements for all seven parameters were repeatable (P > 0.05). With increased RR, agreement improved for tI, tE, and tTot (P ≤ 0.01), did not differ for tI/tE, tI/tTot, and IE50 (P > 0.05) and reduced for breath‐by‐breath (P < 0.05) but not averaged RR (P > 0.05).

Breathing exercises and inspiratory muscle training in heart failure.

Breathing exercises (BE) and inspiratory muscle training (IMT) have been demonstrated to improve ventilation and ventilation-to-perfusion matching, and to improve exercise, functional performance, and many pathophysiologic manifestations of heart failure (HF). This article provides an extensive review of BE and IMT in patients with HF and identifies several key areas in need of further investigation, including the role of expiratory muscle training, IMT targeted at various locations of inspiration (early, mid, or late inspiration), and alteration of the ratio of inspiratory time to total breath time, all of which have substantial potential to improve many pathophysiologic manifestations of HF.

The effect of tracheal occlusion on respiratory load compensation: Changes in neurons containing inhibitory neurotransmitter in the nucleus of the solitary tract in conscious rats

Respiratory load compensation volume–time (Vt–T) relationships have been extensively studied in anesthetized animals. There are only a few studies in conscious animals although consciousness and behavior play a critical role in modulation of breathing. The aims of the study were to determine the effect of intermittent and transient tracheal occlusions (ITTO) elicited load compensation responses and the changes in activation of inhibitory glycinergic neurons in the nucleus of solitary tract (NTS) in conscious rats. The results showed that ITTO elicited an increase in expiratory time (Te) but did not affect inspiratory time (Ti) and diaphragm activity (EMGdia). An increase in total breathing time (Ttot) was due exclusively to the increase in Te. In addition, glycinergic neurons were activated in the intermediate NTS (iNTS) but not in the caudal NTS (cNTS). These results suggest that the activated glycinergic neurons in the iNTS may be important for the neurogenesis of load compensation responses in conscious animals.

Tracheal occlusion-evoked respiratory load compensation and inhibitory neurotransmitter expression in rats

Respiratory load compensation is a sensory-motor reflex generated in the brain stem respiratory neural network. The nucleus of the solitary tract (NTS) is thought to be the primary structure to process the respiratory load-related afferent activity and contribute to the modification of the breathing pattern by sending efferent projections to other structures in the brain stem respiratory neural network. The sensory pathway and motor responses of respiratory load compensation have been studied extensively; however, the mechanism of neurogenesis of load compensation is still unknown. A variety of studies has shown that inhibitory interconnections among the brain stem respiratory groups play critical roles for the genesis of respiratory rhythm and pattern. The purpose of this study was to examine whether inhibitory glycinergic neurons in the NTS were activated by external and transient tracheal occlusions (ETTO) in anesthetized animals. The results showed that ETTO produced load compensation responses with increased inspiratory, expiratory, and total breath time, as well as elevated activation of inhibitory glycinergic neurons in the caudal NTS (cNTS) and intermediate NTS (iNTS). Vagotomized animals receiving transient respiratory loads did not exhibit these load compensation responses. In addition, vagotomy significantly reduced the activation of inhibitory glycinergic neurons in the cNTS and iNTS. The results suggest that these activated inhibitory glycinergic neurons in the NTS might be essential for the neurogenesis of load compensation responses in anesthetized animals.

Sa1161 The High Prevalence of the Positivity to the Lactulose Methane Breath Test in Constipated Patients With Delayed Colonic Transit

Background: Methane (CH4) producing small intestinal bacterial overgrowth (SIBO) is related with constipation, however its relationship with colonic motility is unclear. The aims were to evaluate breath CH4 associated with colonic transit and anorectal pressure in constipated patients. Methods: The study with prospectively collected database involved 51 constipated patients who underwent lactulose CH4 breath test (LMBT), colon marker study, and anorectal manometry. The profile of LMBT in patients were compared to 49 healthy controls. The positivity to LMBT was CH4≥10 ppm in baseline or above baseline within 90 min. The types of constipationwere defined as normal transit and delayed transit constipation according to retention of ≥20% colonic markers. Results: The mean age of the patient was 57.3 years (range: 41 ~ 80 years) and 13 patients (23.8%) were men. There were significant differences in the breath CH4 at the time points of 0, 15, 30, 45, 60, 75, 90, 105, 120, and 135 minute intervals between the delayed transit patients and 1) normal transit patients, or 2) healthy controls, respectively (Fig 1). The positivity to LMBT were higher in delayed transit patients (53.3%, 8/15), than in healthy controls (13.9%, 5/36) or in normal transit patients (53.3%, 8/15), respectively (P < 0.01). The delayed transit was the only independent factor for the positivity to LMBT (OR (95% CI), 142.86 (3.44 9090.9), P < 0.01). The left and total colonic transit time were significantly increased in LMBT-positive patients than in -negative patients (16.4±13.4 vs. 32.5±16.9, P < 0.01, and 48.1±40.2 vs. 82.4±36.7, P < 0.01). The significant correlation was shown between total breath CH4 and time of left colonic transit (γ = 0.39, P < 0.01) (Fig 2), or total colonic transit (γ = 0.33, P = 0.02). However, no significant difference was observed in parameters of anorectal manometry according to LMBT status. Conclusions: SIBO was associated with delayed colonic transit, especially with left colonic transit time, accordingly, which might create a vicious cycle. Further investigation is needed to break the link by therapeutic modality such as antibiotics to target the CH4 producing intestinal bacteria.

Separation anxiety disorder in children: disorder‐specific responses to experimental separation from the mother

Separation anxiety disorder (SAD) is one of the most common anxiety disorders in childhood and is predictive of adult anxiety disorders, especially panic disorder. However, the disorder has seldom been studied and the attempt to distinguish SAD from other anxiety disorders with regard to psychophysiology has not been made. We expected exaggerated anxiety as well as sympathetic and respiratory reactivity in SAD during separation from the mother. Participants were 49 children with a principal diagnosis of SAD, 21 clinical controls (CC) with a principal diagnosis of anxiety disorder other than SAD, and 39 healthy controls (HC) not meeting criteria for any current diagnosis. Analyses of covariance controlling for age were used to assess sympathetic and parasympathetic activation (preejection period and respiratory sinus arrhythmia) as well as cardiovascular (heart rate, mean arterial pressure, total peripheral resistance), respiratory (total breath time, minute ventilation, tidal volume, end-tidal CO(2) , respiratory variability), electrodermal, and self-report (anxiety, cognitions, symptoms) variables during baseline, 4-min separation from, and reunion with the mother. Children with a diagnosis of SAD were characterized by elevated self-reported anxiety responses to separation and increased sympathetic reactivity compared with CC and HC groups. The SAD group also displayed greater vagal withdrawal and higher reactivity in multiple cardiovascular, respiratory, and electrodermal measures compared with the HC group, while corresponding responses were less in the CC group and not significantly different from the other groups. Separation from the mother elicits greater autonomic, respiratory, and experiential responses in children with SAD. Our findings based on brief experimental separation demonstrate differential subjective and physiological manifestations of specific anxiety diagnoses, thus supporting the validity of the diagnostic category of SAD.

Effects of different levels of positive airway pressure on breathing pattern and heart rate variability after coronary artery bypass grafting surgery

The application of continuous positive airway pressure (CPAP) produces important hemodynamic alterations, which can influence breathing pattern (BP) and heart rate variability (HRV). The aim of this study was to evaluate the effects of different levels of CPAP on postoperative BP and HRV after coronary artery bypass grafting (CABG) surgery and the impact of CABG surgery on these variables. Eighteen patients undergoing CABG were evaluated postoperatively during spontaneous breathing (SB) and application of four levels of CPAP applied in random order: sham (3 cmH₂O), 5 cmH₂O, 8 cmH₂O, and 12 cmH₂O. HRV was analyzed in time and frequency domains and by nonlinear methods and BP was analyzed in different variables (breathing frequency, inspiratory tidal volume, inspiratory and expiratory time, total breath time, fractional inspiratory time, percent rib cage inspiratory contribution to tidal volume, phase relation during inspiration, phase relation during expiration). There was significant postoperative impairment in HRV and BP after CABG surgery compared to the preoperative period and improvement of DFAα1, DFAα2 and SD2 indexes, and ventilatory variables during postoperative CPAP application, with a greater effect when 8 and 12 cmH₂O were applied. A positive correlation (P < 0.05 and r = 0.64; Spearman) was found between DFAα1 and inspiratory time to the delta of 12 cmH₂O and SB of HRV and respiratory values. Acute application of CPAP was able to alter cardiac autonomic nervous system control and BP of patients undergoing CABG surgery and 8 and 12 cmH₂O of CPAP provided the best performance of pulmonary and cardiac autonomic functions.

Predator detection enables juvenileLymnaeato form long-term memory

Learning and memory provide the flexibility an organism requires to respond to changing social and ecological conditions. Juvenile Lymnaea have previously been shown to have a diminished capacity to form long-term memory (LTM) following operant conditioning of aerial respiratory behavior. Juvenile Lymnaea, however, can form LTM following classical conditioning of appetitive behaviors. Here, we demonstrate that laboratory-reared juvenile Lymnaea have the ability to detect the presence of a sympatric predator (i.e. crayfish) and respond to the predator by altering their aerial respiratory behavior. In addition to increasing their total breathing time, predator detection confers on juvenile Lymnaea an enhanced capability to form LTM following operant conditioning of aerial respiratory behavior. That is, these juveniles now have the ability to form long-lasting memory. These data support the hypothesis that biologically relevant levels of stress associated with predator detection induce behavioral phenotypic alterations (i.e. enhanced LTM formation) in juveniles, which may increase their fitness. These data also support the notion that learning and memory formation in conjunction with predator detection is a form of inducible defense.

Respiratory Pathophysiology of Panic Disorder: An Ambulatory Monitoring Study

To assess the external validity of laboratory baselines in panic disorder (PD), frequently associated with respiratory pattern abnormalities like increased respiratory variability and sighing, implying a stable pathophysiologic trait characteristic. Physical activity and a variety of breath-by-breath volumetric, timing, and variability measures of respiration were recorded in the daily life of 26 patients with PD and 26 healthy controls (HC), using a novel ambulatory monitoring system optimized for reliable assessment of respiratory pattern. Data were stratified for physical activity to eliminate its confounding effects. Groups showed strong and consistent diurnal patterns in almost all respiratory variables. However, patients with PD did not differ from HC regarding any of the respiratory timing, volumetric and variability measures, with negligible group effect sizes for all measures. Patients with fewer self-reported respiratory symptoms of anxiety exhibited more pronounced rapid shallow breathing as well as diminished total breath time and its variability. Despite state-of-the-art ambulatory assessment and sufficient statistical power to detect respiratory alterations previously observed in the laboratory, we found no evidence for such alterations in PD patients' daily life. Neither the total PD group nor patients with particularly pronounced respiratory symptomatology displayed increased respiratory variability. These results caution against interpreting results from laboratory baselines in PD as reflecting a stable trait characteristic. Rather, they likely represent a state-trait interaction due to enhanced reactivity of PD patients to novel environments. These results challenge aspects of respiratory theories of PD that were based on laboratory findings.

Efficacy and Tolerability of Yoga Breathing in Patients With Chronic Obstructive Pulmonary Disease

Yoga-derived breathing has been reported to improve gas exchange in patients with chronic heart failure and in participants exposed to high-altitude hypoxia. We investigated the tolerability and effect of yoga breathing on ventilatory pattern and oxygenation in patients with chronic obstructive pulmonary disease (COPD). Patients with COPD (N = 11, 3 women) without previous yoga practice and taking only short-acting beta2-adrenergic blocking drugs were enrolled. Ventilatory pattern and oxygen saturation were monitored by means of inductive plethysmography during 30-minute spontaneous breathing at rest (sb) and during a 30-minute yoga lesson (y). During the yoga lesson, the patients were requested to mobilize in sequence the diaphragm, lower chest, and upper chest adopting a slower and deeper breathing. We evaluated oxygen saturation (SaO2%), tidal volume (VT), minute ventilation (E), respiratory rate (i>f), inspiratory time, total breath time, fractional inspiratory time, an index of thoracoabdominal coordination, and an index of rapid shallow breathing. Changes in dyspnea during the yoga lesson were assessed with the Borg scale. During the yoga lesson, data showed the adoption of a deeper and slower breathing pattern (VTsb L 0.54[0.04], VTy L 0.74[0.08], P = .01; i>fsb 20.8[1.3], i>fy 13.8[0.2], P = .001) and a significant improvement in SaO2% with no change in E (SaO2%sb 91.5%[1.13], SaO2%y 93.5%[0.99], P = .02; Esb L/min 11.2[1.1], Ey L/min 10.2[0.9]). All the participants reported to be comfortable during the yoga lesson, with no increase in dyspnea index. We conclude that short-term training in yoga is well tolerated and induces favorable respiratory changes in patients with COPD.

The effect of remifentanil on respiratory variability, evaluated with dynamic modeling

Opioid drugs disrupt signaling in the brain stem respiratory network affecting respiratory rhythm. We evaluated the influence of a steady-state infusion of a model opioid, remifentanil, on respiratory variability during spontaneous respiration in a group of 11 healthy human volunteers. We used dynamic linear and nonlinear models to examine the effects of remifentanil on both directions of the ventilatory loop, i.e., on the influence of natural variations in end-tidal carbon dioxide (Pet(CO(2))) on ventilatory variability, which was assessed by tidal volume (Vt) and breath-to-breath ventilation (i.e., the ratio of tidal volume over total breath time Vt/Ttot), and vice versa. Breath-by-breath recordings of expired CO(2) and respiration were made during a target-controlled infusion of remifentanil for 15 min at estimated effect site (i.e., brain tissue) concentrations of 0, 0.7, 1.1, and 1.5 ng/ml, respectively. Remifentanil caused a profound increase in the duration of expiration. The obtained models revealed a decrease in the strength of the dynamic effect of Pet(CO(2)) variability on Vt (the "controller" part of the ventilatory loop) and a more pronounced increase in the effect of Vt variability on Pet(CO(2)) (the "plant" part of the loop). Nonlinear models explained these dynamic interrelationships better than linear models. Our approach allows detailed investigation of drug effects in the resting state at the systems level using noninvasive and minimally perturbing experimental protocols, which can closely represent real-life clinical situations.

The respiratory time and flow profile at volitional exercise termination

In this study, we examine the effect of exercise on the time and flow characteristics of the respiratory cycle profile at the point of volitional exercise termination. Eight males (mean age 29 years, s = 10; body mass 74 kg, s = 7; height 1.75 m, s = 0.04) undertook a cycle test to volitional exhaustion on a cycle ergometer, which allowed peak oxygen uptake ([Vdot]O2peak) to be measured (mean 51 ml · kg−1 · min−1, s = 7). At a later date, two sub-maximal tests to volitional exhaustion were completed in a random order at 76% (s = 6) and 86%[Vdot]O2peak (s = 7). As expected, the magnitude of the respiratory flow and time characteristics varied with the three exercise intensities, as did the point of exercise termination and terminal ventilation rates, which varied from 7 to 27 min and 112 to 132 litres · min−1 respectively. More importantly, however, at exercise termination some of the characteristics were similar, particularly the breathing frequency (at termination 49 breaths · min−1), the ratio between inspiration and total breath time (0.5), and the later occurrence of peak inspiratory flow (0.24 – 0.48 s). The coincident unity of these time and flow profile characteristics at exercise termination illustrates how the integration of timing and flow during breathing influence exercise capacity in non-elite athletes.