Inspiratory muscle endurance is similarly reduced in the early and late stages of chronic Chagas heart disease.

OBJECTIVE: Inspiratory muscle strength (IMS) appears to be reduced in subjects with chronic Chagas heart disease (CHD), especially in the presence of heart failure (HF). However, only one study about IMS and inspiratory muscle endurance (IME) in those with CHD without heart failure is available. This study aimed to compare IMS and IME in subjects with CHD in the presence and absence of HF. METHODS: This is a cross-sectional study in which 30 CHD adult patients were divided into CHD-CC group (initial phase of CHD, without HF; n = 15) and CHD-HF group (advanced phase of CHD, with HF; n = 15). We assessed IMS by maximum inspiratory pressure (MIP) and IME by incremental (Pthmax) and constant load (TLim) tests. Reduced IMS and IME were considered by predicted MIP values <70% and Pthmax/MIP <75%, respectively. RESULTS: Inspiratory muscle weakness (IMW) was more frequent in CHD-HF than in CHD-CC (46.7% vs. 13.3%; p = 0.05), and both groups had high frequencies of reduced IME (93.3% CHD-CC vs. 100.0% CHD-HF; p = 0.95). Age-adjusted logistic regression analysis using HF as a dependent variable showed that HF was associated with an increased chance of IMW compared with the CHD-CC group (OR = 7.47; p = 0.03; 95% CI 1.20-46.19). CONCLUSION: This study suggests that, in patients with CHD, HF is associated with IMW, and that reduction of IME is already present in the initial phase, similar to the advanced phase with HF.

Flow-resistive loading and diaphragmatic muscle function in term and preterm infants.

PURPOSE: We aimed to assess diaphragmatic function in term and preterm infants with and without history of bronchopulmonary dysplasia (BPD), before and after the application of inspiratory flow resistive loading. METHODS: Forty infants of a median (range) gestational age of 34 (25-40) weeks were studied. BPD was defined as supplemental oxygen requirement for >28 days of life. Seventeen infants were term, 17 preterm without history of BPD, and six preterm with a history of BPD. The diaphragmatic pressure-time index (PTIdi) was calculated as the mean to maximum trans-diaphragmatic pressure ratio times the inspiratory duty cycle. The PTIdi was calculated before and after the application of an inspiratory-flow resistance for 120 s. Airflow was measured by a pneumotachograph and the transdiaphragmatic pressure by a dual pressure catheter. RESULTS: The median (interquartile range [IQR]) pre-resistance PTIdi was higher in preterm infants without BPD (0.064 [0.050-0.077]) compared with term infants (0.052 [0.044-0.062], p = .029) and was higher in preterm infants with BPD (0.119 [0.086-0.132]) compared with a subgroup of preterm infants without BPD (0.062 [0.056-0.072], p = .004). The median (IQR) postresistance PTIdi was higher in preterm infants without BPD (0.101 [0.084-0.132]) compared with term infants (0.067 [0.055-0.083], p < .001) and was higher in preterm infants with BPD [0.201(0.172-0.272)] compared with the preterm subgroup without BPD (0.091 [0.081-0.108],p = .004). The median (IQR) percentage change of the PTIdi after the application of the resistance was higher in preterm infants without BPD (65 [51-92] %) compared with term infants (34 [20-39] %, p < .001). CONCLUSIONS: Preterm infants, especially those recovering from BPD, are at increased risk of diaphragmatic muscle fatigue under conditions of increased inspiratory loading.

COPD stage detection: leveraging the auto-metric graph neural network with inspiratory and expiratory chest CT images.

Chronic obstructive pulmonary disease (COPD) is a common lung disease that can lead to restricted airflow and respiratory problems, causing a significant health, economic, and social burden. Detecting the COPD stage can provide a timely warning for prompt intervention in COPD patients. However, existing methods based on inspiratory (IN) and expiratory (EX) chest CT images are not sufficiently accurate and efficient in COPD stage detection. The lung region images are autonomously segmented from IN and EX chest CT images to extract the 1 , 781 × 2 lung radiomics and 13 , 824 × 2 3D CNN features. Furthermore, a strategy for concatenating and selecting features was employed in COPD stage detection based on radiomics and 3D CNN features. Finally, we combine all the radiomics, 3D CNN features, and factor risks (age, gender, and smoking history) to detect the COPD stage based on the Auto-Metric Graph Neural Network (AMGNN). The AMGNN with radiomics and 3D CNN features achieves the best performance at 89.7 % of accuracy, 90.9 % of precision, 89.5 % of F1-score, and 95.8 % of AUC compared to six classic machine learning (ML) classifiers. Our proposed approach demonstrates high accuracy in detecting the stage of COPD using both IN and EX chest CT images. This method can potentially establish an efficient diagnostic tool for patients with COPD. Additionally, we have identified radiomics and 3D CNN as more appropriate biomarkers than Parametric Response Mapping (PRM). Moreover, our findings indicate that expiration yields better results than inspiration in detecting the stage of COPD.

Effects of Different Inspiratory Muscle Training Protocols on Exercise Capacity, Respiratory Muscle Strength, and Health-Related Quality of Life in Patients with Hypertension.

Aim: This study aimed to explore how varying inspiratory muscle training workloads affect exercise capacity, health-related quality of life (HrQoL), depression, peripheral and respiratory muscle strength, pulmonary function, dyspnea, fatigue, and physical activity levels in hypertension (HT) patients. Methods: A randomized, controlled three-arm study. Forty-five patients (58.37 ± 8.53 y, 7F/38M) with HT received IMT (7 days/8 weeks) by POWERbreathe® Classic LR device and were randomized to control group (CG, 10% maximal inspiratory pressure (MIP), n: 15), low-load group (LLG, 30% MIP), and high-load group (HLG, %50 MIP). Exercise capacity, HrQoL, depression, peripheral and respiratory muscle strength, pulmonary function, fatigue, physical activity level, dyspnea, and sleep quality were evaluated before and after the training. Results: Exercise capacity, physical functioning, peripheral muscle strength, and resting dyspnea were statistically significantly improved in HLG and LLG after the training compared to CG (p < 0.05). Similar improvements in perception of depression, fatigue, and sleep quality were seen within and between the groups (p > 0.05). Statistically significant differences were found within all the groups in terms of MIP and PEF values of respiratory functions (p < 0.05). The superior improvement in the physical activity level was found in the HLG (p < 0.05). Discussion. High-load IMT was particularly effective in increasing physical activity level, peripheral muscle strength, exercise capacity, and improved HrQoL. Low-load IMT was effective in reducing dyspnea and improving respiratory function. Device-guided breathing exercises decreased blood pressure, improved sleep quality, and strengthened respiratory muscles. IMT, an efficient method, is suggested for inclusion in rehabilitation programs due to its capacity to increase physical activity, exercise capacity, and peripheral muscle strength, enhance HrQoL and respiratory function, and alleviate dyspnea. Also, the efficacy of IMT should be investigated with different training protocols such as endurance IMT or functional IMT in HT patients.

Peak Nasal Inspiratory Flow (PNIF) for Nasal Breathing Evaluation.

Measuring nasal airflow and nasal breathing has been a major goal of rhinology. Many objective methods for measuring nasal airflow or nasal airway resistance or dimensions provide valuable data but are time-consuming and require expensive equipment and trained technicians, thus making these methods less practical for clinical practice. Peak nasal inspiratory flow (PNIF) measurement is fast, unexpensive, noninvasive, and able to provide an objective evaluation of nasal airflow in real-time. Unilateral PNIF measurements allow separated evaluation of each side of the nasal airway and may prove particularly useful when clinical assessment detects significant asymmetry between both nasal cavities.PNIF measurements are most useful for assessing changes in nasal airflow achieved by any form of therapy, including surgical treatment of the nasal airway. These measurements generally correlate with other objective methods for nasal airway evaluation, but not unequivocally with patient-reported evaluation of nasal breathing. Nevertheless, as low PNIF values prevent the sensation of a suitable nasal breathing, PNIF measurement may also prove useful to optimize the decision of how to best address patients with complaints of nasal airway obstruction.

Critical roles of airway smooth muscle in mediating deep-inspiration-induced bronchodilation: a big stretch?

BACKGROUND: Deep inspiration (DI) has been shown to induce bronchodilation and bronchoprotection in bronchochallenged healthy subjects, but not in asthmatics. Strain-induced relaxation of airway smooth muscle (ASM) is considered one of the factors responsible for these effects. Other factors include the release or redistribution of pulmonary surfactant, alteration in mucus plugs, and changes in airway heterogeneity. MAIN BODY: The present review is focused on the DI effect on ASM function, based on recent findings from ex vivo sheep lung experiments showing a large change in airway diameter during a DI. The amount of stretch on the airways, when applied to isolated airway rings in vitro, caused a substantial decrease in ASM contractility that takes many minutes to recover. When challenged with a bronchoconstrictor, the increase in pulmonary resistance in the ex vivo ovine lungs is mostly due to the increase in airway resistance. CONCLUSIONS: Although non-ASM related factors cannot be excluded, the large strain on the airways associated with a DI substantially reduces ASM contractility and thus can account for most of the bronchodilatory and bronchoprotective effects of DI.

The Effects of Respiratory Muscle Training on Resting-State Brain Activity and Thoracic Mobility in Healthy Subjects: A Randomized Controlled Trial.

BACKGROUND: Although inspiratory muscle training (IMT) is an effective intervention for improving breath perception, brain mechanisms have not been studied yet. PURPOSE: To examine the effects of IMT on insula and default mode network (DMN) using resting-state functional MRI (RS-fMRI). STUDY TYPE: Prospective. POPULATION: A total of 26 healthy participants were randomly assigned to two groups as IMT group (n = 14) and sham IMT groups (n = 12). FIELD STRENGTH/SEQUENCE: A 3-T, three-dimensional T2* gradient-echo echo planar imaging sequence for RS-fMRI was obtained. ASSESSMENT: The intervention group received IMT at 60% and sham group received at 15% of maximal inspiratory pressure (MIP) for 8 weeks. Pulmonary and respiratory muscle function, and breathing patterns were measured. Groups underwent RS-fMRI before and after the treatment. STATISTICAL TESTS: Statistical tests were two-tailed P < 0.05 was considered statistically significant. Student's t test was used to compare the groups. One-sample t-test for each group was used to reveal pattern of functional connectivity. A statistical threshold of P < 0.001 uncorrected value was set at voxel level. We used False discovery rate (FDR)-corrected P < 0.05 cluster level. RESULTS: The IMT group showed more prominent alterations in insula and DMN connectivity than sham group. The MIP was significantly different after IMT. Respiratory rate (P = 0.344), inspiratory time (P = 0.222), expiratory time (P = 1.000), and inspiratory time/total breath time (P = 0.572) of respiratory patterns showed no significant change after IMT. All DMN components showed decreased, while insula showed increased activation significantly. DATA CONCLUSION: Differences in brain activity and connectivity may reflect improved ventilatory perception with IMT with a possible role in regulating breathing pattern by processing interoceptive signals. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 4.

Effects of Inspiratory Muscle Training on Clinical Predictors of Respiratory Muscle Strength and Lung Function in Burned Patients with Inhalation Injury.

Chronic airway illness is a well-documented inhalation injury side effect. Many pulmonary function impairments persisted for several months after lung parenchymal injury. Thus, the purpose of this study was to investigate the effects of inspiratory muscle training on respiratory muscle strength and pulmonary function (PFT) in patients who had suffered an inhalation injury. This study included male patients with inhalation injuries aged 20-35 years. Patients were chosen at random and assigned to an exercise group, which received inspiratory muscle training and routine chest physiotherapy, including early ambulation, coughing, and deep breathing, three times weekly for 4 weeks, and the control group, which only received routine chest physiotherapy. All participants were assessed for PFT and respiratory muscle strength at enrollment and the end of the study. The statistical analysis for outcome variables between both groups revealed no significant differences before treatment (P > .05) of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), maximal inspiratory pressure, and maximal expiratory pressure. According to the findings of this study, including IMT as part of a physical therapy program led to significant gains (P ˂ .05) in FVC and FEV1. However, after treatment, there was not a substantial difference found in either the MIP or the MEP between the groups. The exercise group performed better in terms of FVC, FEV1, MIP, and MEP after receiving treatment, according to these significant and non-significant differences.

Training the equine respiratory muscles: Inspiratory muscle strength.

BACKGROUND: Little is known about the response of the equine respiratory muscles to training. OBJECTIVES: To measure an index of inspiratory muscle strength (IMSi) before and after a period of conventional exercise training (phase 1) and inspiratory muscle training (IMT), comparing high-load (treatment) and low-load (control) groups (phase 2). STUDY DESIGN: Prospective randomised controlled trial. METHODS: Phase 1: Twenty National Hunt Thoroughbred racehorses performed an inspiratory muscle strength test (IMST) twice on two occasions; when unfit at timepoint A (July), and when race fit at timepoint B (October). Phase 2: Thirty-five Thoroughbred racehorses at race fitness were randomly assigned into a high-load (treatment, n = 20) or low-load (control, n = 15) IMT group. The high-load group followed an IMT protocol that gradually increased the inspiratory pressure applied every 4 days. The low-load group underwent sham IMT with a low training load. The IMT was performed 5 days/week for 10 weeks. The IMST was performed twice on two occasions, timepoint B (October) and timepoint C (January). Conventional exercise training and racing continued during the study period. The peak IMSi values obtained from the different groups at timepoints A, B and C were compared using a Wilcoxon Signed Rank Test. RESULTS: Phase 1: There was a significant increase in IMSi from timepoint A: 22.5 cmH2 O (21-25) to timepoint B: 26 cmH2 O (24-30) (p = 0.015). Phase 2: From timepoint B to C there was a significant increase in IMSi for the high-load group 34 cmH2 O (28-36) (p = 0.001) but not the low-load group 26 cmH2 O (24-30) (p = 0.929). The peak IMSi at timepoint C was significantly higher for the high-load than low-load group (p = 0.019). MAIN LIMITATIONS: Single centre study with only National Hunt horses undergoing race-training included. CONCLUSIONS: In horses undergoing race training there is a significant increase in IMSi in response to conventional exercise training and high-load IMT.

Training the equine respiratory muscles: Ultrasonographic measurement of muscle size.

BACKGROUND: Limited information exists regarding changes in the size of respiratory and locomotor muscles in response to exercise training in the Thoroughbred racehorse. OBJECTIVES: To describe and compare the responses of the respiratory and locomotor muscles to conventional exercise training and inspiratory muscle training (IMT). STUDY DESIGN: Prospective randomised controlled trial. METHODS: Thoroughbred racehorses, in training for competition in National Hunt races, were recruited from two training establishments. Ultrasonographic images were obtained for selected muscles of the upper airway, diaphragm, accessory respiratory, and locomotor systems and their sizes measured. Examinations were performed at three timepoints: (A) when unfit, (B) following 12 weeks of conventional exercise training and (C) following 10-12 weeks continued training at race fitness. In addition, horses at yard 1 performed IMT, between timepoint B and C, and were randomly assigned into high-load (treatment) or low-load (control) group. Repeated measures models were constructed to compare the change in muscle measurements over time, and to investigate the effects of yard, previous airway surgery and IMT on the change in ultrasonographic size measurements obtained. RESULTS: Upper airway muscle size increased in response to conventional race training between timepoints A-C, and B-C. Diaphragm size increased in response to conventional exercise training between timepoints A and B. The diaphragm size of horses that undertook high-load IMT was either maintained or increased, whereas diaphragm size decreased in horses that undertook low-load IMT or no IMT between timepoints B and C. A significant interaction between gluteal muscle size and airway surgery status was observed, with greater gluteal muscle thicknesses measured in horses that had not previously undergone airway surgery (left gluteal 3.9%, p < 0.001; right 4.5%, p = 0.04). MAIN LIMITATIONS: Low number of horses underwent IMT. CONCLUSIONS: Respiratory and locomotor muscles increase in size in response to conventional exercise training, with a further change in diaphragm size in response to inspiratory muscle training.

Sex differences in blood pressure and inactive limb blood flow responses during dynamic leg exercise with increased inspiratory muscle work.

We hypothesized that, compared with young males, young females have a smaller decrease in blood flow to the inactive limb, accompanied by a smaller increase in arterial blood pressure, during dynamic exercise with increased inspiratory muscle work. Young males and females performed dynamic knee-extension and -flexion exercises for 10 min (spontaneous breathing for 5 min and voluntary hyperpnoea with or without inspiratory resistance for 5 min). Mean arterial blood pressure (MAP) and mean blood flow (MBF) in the brachial artery were continuously measured by means of finger photoplethysmography and Doppler ultrasound, respectively. No sex differences were found in the ΔMAP and ΔMBF (Δ: from baseline) during exercise without inspiratory resistance. In contrast, the ΔMAP during exercise with inspiratory resistive breathing was greater (P < 0.05) in males (+31.3 ± 2.1 mmHg, mean ± SE) than females (+18.9 ± 3.2 mmHg). The MBF during exercise with inspiratory resistance did not change in males (-4.4 ± 10.6 mL/min), whereas it significantly increased in females (+25.2 ± 15.4 mL/min). These results suggest that an attenuated inspiratory muscle-induced metaboreflex in young females affects blood flow distribution during submaximal dynamic leg exercise.

Inspiratory and leg muscle blood flows during inspiratory muscle metaboreflex activation in heart failure with preserved ejection fraction.

The purpose of this study was to determine the cardiovascular consequences elicited by activation of the inspiratory muscle metaboreflex in patients with heart failure with preserved ejection fraction (HFpEF) and controls. Patients with HFpEF (n = 15; 69 ± 10 yr; 33 ± 4 kg/m2) and controls (n = 14; 70 ± 8 yr; 28 ± 4 kg/m2) performed an inspiratory loading trial at 60% maximal inspiratory pressure (PIMAX) until task failure. Mean arterial pressure (MAP) was measured continuously. Near-infrared spectroscopy and bolus injections of indocyanine green dye were used to determine the percent change in blood flow index (%ΔBFI) from baseline to the final minute of inspiratory loading in the vastus lateralis and sternocleidomastoid muscles. Vascular resistance index (VRI) was calculated. Time to task failure was shorter in HFpEF than in controls (339 ± 197 s vs. 626 ± 403 s; P = 0.02). Compared with controls, patients with HFpEF had a greater increase from baseline in MAP (16 ± 7 vs. 10 ± 6 mmHg) and vastus lateralis VRI (76 ± 45 vs. 32 ± 19%) as well as a greater decrease in vastus lateralis %ΔBFI (-32 ± 14 vs. -17 ± 9%) (all, P < 0.05). Sternocleidomastoid %ΔBFI normalized to absolute inspiratory pressure was higher in HFpEF compared with controls (8.0 ± 5.0 vs. 4.0 ± 1.9% per cmH2O·s; P = 0.03). These data indicate that patients with HFpEF exhibit exaggerated cardiovascular responses with inspiratory muscle metaboreflex activation compared with controls.NEW & NOTEWORTHY Respiratory muscle dysfunction is thought to contribute to exercise intolerance in heart failure with preserved ejection fraction (HFpEF); however, the underlying mechanisms are unknown. In the present study, patients with HFpEF had greater increases in leg muscle vascular resistance index and greater decreases in leg muscle blood flow index compared with controls during inspiratory resistive breathing (to activate the metaboreflex). Furthermore, respiratory muscle blood flow index responses normalized to pressure generation during inspiratory resistive breathing were exaggerated in HFpEF compared with controls.

Blood pressure and coeliac artery blood flow responses during increased inspiratory muscle work in healthy males.

NEW FINDINGS: What is the central question of this study? Increased work of breathing and the accumulation of metabolites have neural and cardiovascular consequences through a respiratory muscle-induced metaboreflex. The influence of the respiratory muscle-induced metaboreflex on splanchnic blood flow in humans remains unknown. What is the main finding and its importance? Coeliac artery blood flow decreased gradually during inspiratory resistive breathing, accompanied by a progressive increase in arterial blood pressure. It is possible that the respiratory muscle-induced metaboreflex contributes to splanchnic blood flow regulation. ABSTRACT: The purpose of this study was to clarify the effect of increasing inspiratory muscle work on coeliac artery blood flow. Eleven healthy young males completed the study. The subjects performed voluntary hyperventilation with or without inspiratory resistance (loading or non-loading trial; tidal volume of 40% of vital capacity and breathing frequency of 20 breaths/min). The loading trial was conducted with inspiratory resistance (40% of maximal inspiratory pressure) and was terminated when the subjects could no longer maintain the target tidal volume or breathing frequency. The non-loading trial was conducted without inspiratory resistance and was of the same duration as the loading trial. Arterial blood pressure was recorded using finger photoplethysmography, and coeliac artery blood flow was measured using Doppler ultrasound. Mean arterial blood pressure increased gradually during the loading trial (mean ± SD; from 89.0 ± 10.8 to 103.9 ± 17.3 mmHg) but not in the non-loading trial (from 88.7 ± 5.9 to 90.4 ± 9.9 mmHg). Coeliac artery blood flow and coeliac vascular conductance decreased gradually during the loading trial (from 601.2 ± 155.7 to 482.6 ± 149.5 mL/min and from 6.9 ± 2.2 to 4.8 ± 1.7 mL/min/mmHg, respectively) but were unchanged in the non-loading trial (from 630.7 ± 157.1 to 635.6 ± 195.7 mL/min and from 7.1 ± 1.8 to 7.2 ± 2.9 mL/min/mmHg, respectively). These results show that increasing inspiratory muscle work affects splanchnic blood flow regulation, and we suggest that this might be mediated by the inspiratory muscle-induced metaboreflex.

The influence of the respiratory cycle on reaction times in sensory-cognitive paradigms.

Behavioural and electrophysiological studies point to an apparent influence of the state of respiration, i.e., whether we inhale or exhale, on brain activity and cognitive performance. Still, the prevalence and relevance of such respiratory-behavioural relations in typical sensory-cognitive tasks remain unclear. We here used a battery of six tasks probing sensory detection, discrimination and short-term memory to address the questions of whether and by how much behaviour covaries with the respiratory cycle. Our results show that participants tend to align their respiratory cycle to the experimental paradigm, in that they tend to inhale around stimulus presentation and exhale when submitting their responses. Furthermore, their reaction times, but not so much their response accuracy, consistently and significantly covary with the respiratory cycle, differing between inhalation and exhalation. This effect is strongest when analysed contingent on the respiratory state around participants' responses. The respective effect sizes of these respiration-behaviour relations are comparable to those seen in other typical experimental manipulations in sensory-cognitive tasks, highlighting the relevance of these effects. Overall, our results support a prominent relation between respiration and sensory-cognitive function and show that sensation is intricately linked to rhythmic bodily or interoceptive functions.

Visual discrimination accuracy does not differ between nasal inhalation and exhalation when stimuli are voluntarily aligned to breathing phase.

This study investigated the possible enhancement of visual discrimination accuracy by voluntarily adjusting the timing of stimulus presentation to a specific respiratory phase. Previous research has suggested that respiratory phases modulate perceptual and cognitive processing. For instance, a fearful face was identified faster when presented during nasal inhalation than during nasal exhalation, which could be related to changes in neural oscillatory activity synchronized with breathing in through one's nose. Based on such findings, the present study asked 40 young adults to perform an emotional discrimination task consisting of distinguishing fearful vs. neutral faces and a physical discrimination task consisting of distinguishing high- vs. low-contrast Gabor patches during nasal respiration. Participants presented themselves with the stimuli to be judged in a designated respiratory phase by pressing a button. It was hypothesized that fear discrimination accuracy would be higher during inhalation than exhalation if sensitivity to emotional stimuli increased during inhalation. Conversely, if overall visual sensitivity was enhanced during inhalation, the identical effect was expected for contrast discrimination. The results indicated that discrimination accuracy did not differ between inhalation and exhalation phases in either task. This result provided no evidence that the respiratory phase affected visual discrimination accuracy when people adjusted the timing of stimulus presentation to the onset of inhalation or exhalation.

Plethysmographic assessment of tidal expiratory flow limitation.

Chronic obstructive pulmonary disease (COPD) patients often experience tidal expiratory flow-limitation (tEFL), a condition causing respiratory and cardiovascular detrimental effects. As the appearance of tEFL should increase expiratory (Rexp) relative to inspiratory (Rins) resistance, we hypothesized that Rexp/Rins can be used to detect tEFL. Rexp/Rins was measured with a commercial plethysmograph in 109 healthy subjects and, before and after bronchodilation (BD), in 64 COPD patients, 36 with and 28 without tEFL according to the NEP technique. Before BD, the median (interquartile range) of Rexp/Rins was significantly greater (P < 0.001) in COPD patients with tEFL (2.47(3.06;7.07)) than in COPD patients without tEFL (1.63(1.44;1.82)) and in healthy subjects (1.52(1.35;1.62)). In COPD patients Rexp/Rins above 1.98 predicted the presence of tEFL with 96 % specificity and 92 % sensitivity, Rexp2/Rins performing even better. After BD the predictive ability of Rexp/Rins slightly declined, but remained elevated. The non-invasive measurement of Rexp/Rins is an easy, inexpensive, routinely usable method to detect tEFL in spontaneously breathing COPD subjects.

Effect of breathing on venous return during delayed cord clamping: an observational study.

OBJECTIVE: To investigate the effect of spontaneous breathing on venous return in term infants during delayed cord clamping at birth. METHODS: Echocardiographic ultrasound recordings were obtained directly after birth in healthy term-born infants. A subcostal view was used to obtain an optimal view of the inferior vena cava (IVC) entering the right atrium, including both the ductus venosus (DV) and the hepatic vein (HV). Colour Doppler was used to assess flow direction and flow velocity. Recordings continued until the umbilical cord was clamped and were stored in digital format for offline analyses. RESULTS: Ultrasound recordings were obtained in 15 infants, with a median (IQR) gestational age of 39.6 (39.0-40.9) weeks and a birth weight of 3560 (3195-4205) g. Flow was observed to be antegrade in the DV and HV in 98% and 82% of inspirations, respectively, with flow velocity increasing in 74% of inspirations. Retrograde flow in the DV was observed sporadically and only occurred during expiration. Collapse of the IVC occurred during 58% of inspirations and all occurred caudal to the DV inlet (100%). CONCLUSION: Spontaneous breathing was associated with collapse of the IVC and increased antegrade DV and HV flow velocity during inspiration. Therefore, inspiration appears to preferentially direct blood flow from the DV into the right atrium. This indicates that inspiration could be a factor driving placental transfusion in infants.

Prefrontal cortex activation during incremental inspiratory loading in healthy participants.

We aimed to investigate whether changes in prefrontal cortex (PFC) oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) associates with inspiratory muscle effort during inspiratory threshold loading (ITL) in healthy participants. Participants performed an incremental ITL. Breathing pattern, partial pressure of end-tidal CO2 (PETCO2), mouth pressure and O2Hb and HHb over the right dorsolateral PFC, sternocleidomastoid (SCM), and diaphragm/intercostals (Dia/IC) were monitored. Fourteen healthy participants (8 men; 29 ± 5 years) completed testing. Dyspnea was higher post- than pre-ITL (5 ± 1 vs. 0 ± 1, respectively; P<0.05). PFC O2Hb increased (P < 0.001) and HHb decreased (P = 0.001) at low loads but remained stable with increasing ITL intensities. PFC total hemoglobin increased at task failure compared to rest. SCM HHb increased throughout increasing intensities. SCM and Dia/IC total hemoglobin increased in the at task failure compared to rest. PETCO2 did not change (P = 0.528). PFC is activated early during the ITL but does not show central fatigue at task failure despite greater dyspnea and an imbalance of SCM oxygen demand and delivery.

The role of neuronal excitation and inhibition in the pre-Bötzinger complex on the cough reflex in the cat.

Brainstem respiratory neuronal network significantly contributes to cough motor pattern generation. Neuronal populations in the pre-Bötzinger complex (PreBötC) represent a substantial component for respiratory rhythmogenesis. We studied the role of PreBötC neuronal excitation and inhibition on mechanically induced tracheobronchial cough in 15 spontaneously breathing, pentobarbital anesthetized adult cats (35 mg/kg, iv initially). Neuronal excitation by unilateral microinjection of glutamate analog d,l-homocysteic acid resulted in mild reduction of cough abdominal electromyogram (EMG) amplitudes and very limited temporal changes of cough compared with effects on breathing (very high respiratory rate, high amplitude inspiratory bursts with a short inspiratory phase, and tonic inspiratory motor component). Mean arterial blood pressure temporarily decreased. Blocking glutamate-related neuronal excitation by bilateral microinjections of nonspecific glutamate receptor antagonist kynurenic acid reduced cough inspiratory and expiratory EMG amplitude and shortened most cough temporal characteristics similarly to breathing temporal characteristics. Respiratory rate decreased and blood pressure temporarily increased. Limiting active neuronal inhibition by unilateral and bilateral microinjections of GABAA receptor antagonist gabazine resulted in lower cough number, reduced expiratory cough efforts, and prolongation of cough temporal features and breathing phases (with lower respiratory rate). The PreBötC is important for cough motor pattern generation. Excitatory glutamatergic neurotransmission in the PreBötC is involved in control of cough intensity and patterning. GABAA receptor-related inhibition in the PreBötC strongly affects breathing and coughing phase durations in the same manner, as well as cough expiratory efforts. In conclusion, differences in effects on cough and breathing are consistent with separate control of these behaviors.NEW & NOTEWORTHY This study is the first to explore the role of the inspiratory rhythm and pattern generator, the pre-Bötzinger complex (PreBötC), in cough motor pattern formation. In the PreBötC, excitatory glutamatergic neurotransmission affects cough intensity and patterning but not rhythm, and GABAA receptor-related inhibition affects coughing and breathing phase durations similarly to each other. Our data show that the PreBötC is important for cough motor pattern generation, but cough rhythmogenesis appears to be controlled elsewhere.

The impact of modern radiotherapy on long-term cardiac sequelae in breast cancer survivor: a focus on deep inspiration breath-hold (DIBH) technique.

INTRODUCTION: One of the most feared side effects of radiotherapy (RT) in the setting of breast cancer (BC) patients is cardiac toxicity. This side effect can jeopardize the quality of life (QoL) of long-term survivors. The impact of modern techniques of RT such as deep inspiration breath hold (DIBH) have dramatically changed this setting. We report and discuss the results of the literature overview of this paper. MATERIALS AND METHODS: Literature references were obtained with a PubMed query, hand searching, and clinicaltrials.gov. RESULTS: We reported and discussed the toxicity of RT and the improvements due to the modern techniques in the setting of BC patients. CONCLUSIONS: BC patients often have a long life expectancy, thus the RT should aim at limiting toxicities and at the same time maintaining the same high cure rates. Further studies are needed to evaluate the risk-benefit ratio to identify patients at higher risk and to tailor the treatment choices.