Standardisation facilitates reliable interpretation of ETCO2 during manual cardiopulmonary resuscitation.

BACKGROUND: Interpretation of end-tidal CO2 (ETCO2) during manual cardiopulmonary resuscitation (CPR) is affected by variations in ventilation and chest compressions. This study investigates the impact of standardising ETCO2 to constant ventilation rate (VR) and compression depth (CD) on absolute values and trends. METHODS: Retrospective study of out-of-hospital cardiac arrest cases with manual CPR, including defibrillator and clinical data. ETCO2, VR and CD values were averaged by minute. ETCO2 was standardised to 10 vpm and 50 mm. We compared standardised (ETs) and measured (ETm) values and trends during resuscitation. RESULTS: Of 1,036 cases, 287 met the inclusion criteria. VR was mostly lower than recommended, 8.8 vpm, and highly variable within and among patients. CD was mostly within guidelines, 49.8 mm, and less varied. ETs was lower than ETm by 7.3 mmHg. ETs emphasized differences by sex (22.4 females vs. 25.6 mmHg males), initial rhythm (29.1 shockable vs. 22.7 mmHg not), intubation type (25.6 supraglottic vs. 22.4 mmHg endotracheal) and return of spontaneous circulation (ROSC) achieved (34.5 mmHg) vs. not (20.1 mmHg). Trends were different between non-ROSC and ROSC patients before ROSC (-0.3 vs. + 0.2 mmHg/min), and between sustained and rearrest after ROSC (-0.7 vs. -2.1 mmHg/min). Peak ETs was higher for sustained than for rearrest (53.0 vs. 42.5 mmHg). CONCLUSION: Standardising ETCO2 eliminates effects of VR and CD variations during manual CPR and facilitates comparison of values and trends among and within patients. Its clinical application for guidance of resuscitation warrants further investigation.

Driving pressure, as opposed to tidal volume based on predicted body weight, is associated with mortality: results from a prospective cohort of COVID-19 acute respiratory distress syndrome patients.

OBJECTIVE: To evaluate the association between driving pressure and tidal volume based on predicted body weight and mortality in a cohort of patients with acute respiratory distress syndrome caused by COVID-19. METHODS: This was a prospective, observational study that included patients with acute respiratory distress syndrome due to COVID-19 admitted to two intensive care units. We performed multivariable analyses to determine whether driving pressure and tidal volume/kg predicted body weight on the first day of mechanical ventilation, as independent variables, are associated with hospital mortality. RESULTS: We included 231 patients. The mean age was 64 (53 - 74) years, and the mean Simplified Acute and Physiology Score 3 score was 45 (39 - 54). The hospital mortality rate was 51.9%. Driving pressure was independently associated with hospital mortality (odds ratio 1.21, 95%CI 1.04 - 1.41 for each cm H2O increase in driving pressure, p = 0.01). Based on a double stratification analysis, we found that for the same level of tidal volume/kg predicted body weight, the risk of hospital death increased with increasing driving pressure. However, changes in tidal volume/kg predicted body weight were not associated with mortality when they did not lead to an increase in driving pressure. CONCLUSION: In patients with acute respiratory distress syndrome caused by COVID-19, exposure to higher driving pressure, as opposed to higher tidal volume/kg predicted body weight, is associated with greater mortality. These results suggest that driving pressure might be a primary target for lung-protective mechanical ventilation in these patients.

Effects of inspiratory muscle training on thoracoabdominal volume regulation in older adults: A randomised controlled trial.

OBJECTIVES: We investigated the effect of inspiratory muscle training (IMT) on inspiratory muscle strength, functional capacity and respiratory muscle kinematics during exercise in healthy older adults. METHODS: 24 adults were randomised into an IMT or SHAM-IMT group. Both groups performed 30 breaths, twice daily, for 8 weeks, at intensities of ∼50 % maximal inspiratory pressure (PImax; IMT) or <15 % PImax (SHAM-IMT). Measurements of PImax, breathing discomfort during a bout of IMT, six-minute walk distance, physical activity levels, and balance were assessed pre- and post-intervention. Respiratory muscle kinematics were assessed via optoelectronic plethysmography (OEP) during constant work rate cycling. RESULTS: PImax was significantly improved (by 20.0±11.9 cmH2O; p=0.001) in the IMT group only. Breathing discomfort ratings during IMT significantly decreased (from 3.5±0.9-1.7±0.8). Daily sedentary time was decreased (by 28.0±39.8 min; p=0.042), and reactive balance significantly improved (by 1.2±0.8; p<0.001) in the IMT group only. OEP measures showed a significantly greater contribution of the pulmonary and abdominal rib cage compartments to total tidal volume expansion post-IMT. CONCLUSIONS: IMT significantly improves inspiratory muscle strength and breathing discomfort in this population. IMT induces greater rib cage expansion and diaphragm descent during exercise, thereby suggesting a less restrictive effect on thoracic expansion and increased diaphragmatic power generation.

Explorative study on lower inflection point dynamics during cardiopulmonary resuscitation: Potential implications for airway management.

INTRODUCTION: In patients undergoing cardiopulmonary resuscitation (CPR) after an Out-of-Hospital Cardiac Arrest (OHCA), intrathoracic airway closure can impede ventilation, adversely affecting patient outcomes. This explorative study investigates the evolution of intrathoracic airway closure by analyzing the lower inflection point (LIP) during the inspiration phase of CPR, aiming to identify the potential thresholds for alveolar recruitment. METHODS AND MATERIALS: Eleven OHCA patients undergoing CPR with endotracheal intubation and manual bag ventilation were included. Flow and pressure measurements were obtained using Sensirion SFM3200AW and Wika CPT2500 sensors attached to the endotracheal tube, connected to a Surface Go Tablet for data collection. Flow data was analyzed in Microsoft Excel, while pressure data was processed using the Wika USBsoft2500 application. Analysis focused on the inspiration phase of the first 6-8 breaths, with an additional 2 breaths recorded and analyzed at the end of CPR. RESULTS: Across the cohort, the median tidal volume was 870.00 milliliter (mL), average flow was 31.90 standard liters per minute (slm), and average pressure was 17.21 cmH2O. The calculated average LIP was 31.47 cmH2O. Most cases (72.7%) exhibited a negative trajectory in LIP evolution during CPR, with 2 cases (18.2%) showing a positive trajectory and 1 case remaining inconclusive. The average LIP in the first 8 breaths was significantly higher than in the last 2 breaths (p = 0.018). No significant correlation was found between average LIP and return of spontaneous circulation (ROSC), compression depth, frequency, or end-tidal CO2 (EtCO2). However, a significant negative correlation was observed between the average LIP of the last 2 breaths and CPR duration (p = 0.023). VALIDATION: LIP calculation in low-flow ventilations using the novel mathematical method yielded values consistent with those reported in the literature. DISCUSSION/CONCLUSION: These explorative data demonstrate a predominantly negative trajectory in LIP evolution during CPR, suggesting potential challenges in maintaining airway patency. Limitations include a small sample size and sensor recording issues. Further research is warranted to explore the evolution of LIP and its implications for personalized ventilation strategies in CPR.

Early administration of umbilical cord blood cells following brief high tidal volume ventilation in preterm sheep: a cautionary tale.

BACKGROUND: Umbilical cord blood (UCB) cells are a promising treatment for preterm brain injury. Access to allogeneic sources of UCB cells offer the potential for early administration to optimise their therapeutic capacities. As preterm infants often require ventilatory support, which can contribute to preterm brain injury, we investigated the efficacy of early UCB cell administration following ventilation to reduce white matter inflammation and injury. METHODS: Preterm fetal sheep (0.85 gestation) were randomly allocated to no ventilation (SHAM; n = 5) or 15 min ex utero high tidal volume ventilation. One hour following ventilation, fetuses were randomly allocated to i.v. administration of saline (VENT; n = 7) or allogeneic term-derived UCB cells (24.5 ± 5.0 million cells/kg; VENT + UCB; n = 7). Twenty-four hours after ventilation, lambs were delivered for magnetic resonance imaging and post-mortem brain tissue collected. Arterial plasma was collected throughout the experiment for cytokine analyses. To further investigate the results from the in vivo study, mononuclear cells (MNCs) isolated from human UCB were subjected to in vitro cytokine-spiked culture medium (TNFα and/or IFNγ; 10 ng/mL; n = 3/group) for 16 h then supernatant and cells collected for protein and mRNA assessments respectively. RESULTS: In VENT + UCB lambs, systemic IFNγ levels increased and by 24 h, there was white matter neuroglial activation, vascular damage, reduced oligodendrocytes, and increased average, radial and mean diffusivity compared to VENT and SHAM. No evidence of white matter inflammation or injury was present in VENT lambs, except for mRNA downregulation of OCLN and CLDN1 compared to SHAM. In vitro, MNCs subjected to TNFα and/or IFNγ displayed both pro- and anti-inflammatory characteristics indicated by changes in cytokine (IL-18 & IL-10) and growth factor (BDNF & VEGF) gene and protein expression compared to controls. CONCLUSIONS: UCB cells administered early after brief high tidal volume ventilation in preterm fetal sheep causes white matter injury, and the mechanisms underlying these changes are likely dysregulated responses of the UCB cells to the degree of injury/inflammation already present. If immunomodulatory therapies such as UCB cells are to become a therapeutic strategy for preterm brain injury, especially after ventilation, our study suggests that the inflammatory state of the preterm infant should be considered when timing UCB cells administration.

Expiratory flow limitation during mechanical ventilation: real-time detection and physiological subtypes.

BACKGROUND: Tidal expiratory flow limitation (EFLT) complicates the delivery of mechanical ventilation but is only diagnosed by performing specific manoeuvres. Instantaneous analysis of expiratory resistance (Rex) can be an alternative way to detect EFLT without changing ventilatory settings. This study aimed to determine the agreement of EFLT detection by Rex analysis and the PEEP reduction manoeuvre using contingency table and agreement coefficient. The patterns of Rex were explored. METHODS: Medical patients ≥ 15-year-old receiving mechanical ventilation underwent a PEEP reduction manoeuvre from 5 cmH2O to zero for EFLT detection. Waveforms were recorded and analyzed off-line. The instantaneous Rex was calculated and was plotted against the volume axis, overlapped by the flow-volume loop for inspection. Lung mechanics, characteristics of the patients, and clinical outcomes were collected. The result of the Rex method was validated using a separate independent dataset. RESULTS: 339 patients initially enrolled and underwent a PEEP reduction. The prevalence of EFLT was 16.5%. EFLT patients had higher adjusted hospital mortality than non-EFLT cases. The Rex method showed 20% prevalence of EFLT and the result was 90.3% in agreement with PEEP reduction manoeuvre. In the validation dataset, the Rex method had resulted in 91.4% agreement. Three patterns of Rex were identified: no EFLT, early EFLT, associated with airway disease, and late EFLT, associated with non-airway diseases, including obesity. In early EFLT, external PEEP was less likely to eliminate EFLT. CONCLUSIONS: The Rex method shows an excellent agreement with the PEEP reduction manoeuvre and allows real-time detection of EFLT. Two subtypes of EFLT are identified by Rex analysis. TRIAL REGISTRATION: Clinical trial registered with www.thaiclinicaltrials.org (TCTR20190318003). The registration date was on 18 March 2019, and the first subject enrollment was performed on 26 March 2019.

Evaluation of the relationship between end-tidal carbon dioxide level and heart failure classification.

OBJECTIVE: Heart failure is a disease with cardiac dysfunction, and its morbidity and mortality are associated with the degree of dysfunction. The New York Heart Association classifies the heart failure stages based on the severity of symptoms and physical activity. End-tidal carbon dioxide refers to the level of carbon dioxide that a person exhales with each breath. End-tidal carbon dioxide levels can be used in many clinical conditions such as heart failure, asthma, and chronic obstructive pulmonary disease. The aim of the study was to reveal the relationship between end-tidal carbon dioxide levels and the New York Heart Association classification of heart failure stages. METHODS: This study was conducted at Kahramanmaras Sütçü Imam University Faculty of Medicine Adult Emergency Department between 01/03/2019 and 01/09/2019. A total of 80 patients who presented to the emergency department with a history of heart failure or were diagnosed with heart failure during admission were grouped according to the New York Heart Association classification of heart failure stages. The laboratory parameters, ejection fraction values, and end-tidal carbon dioxide levels of the patients were measured and recorded in the study forms. RESULTS: End-tidal carbon dioxide levels and ejection fraction values were found to be significantly lower in the stage 4 group compared to the other groups. Furthermore, pro-B-type natriuretic peptide (BNP) values were found to be significantly higher in stage 4 group compared to the other groups. CONCLUSION: It was concluded that end-tidal carbon dioxide levels could be used together with pro-BNP and ejection fraction values in determining the severity of heart failure.

Are instructors correctly gauging ventilation competence acquired by course attendees?

Achievement of adequate ventilation skills during training courses is mainly based on instructors' perception of attendees' capability to ventilate with correct rate and chest compression:ventilation ratio, while leading to chest raising, as evidence of adequate tidal volume. Accuracy in evaluating ventilation competence was assessed in 20 ACLS provider course attendees, by comparing course instructors' evaluation with measures from a ventilation feedback device. According to course instructors, all candidates acquired adequate ventilation competence. However, data from the feedback device indicated a ventilation not aligned with current guidelines, with higher tidal volume and lower rate (p < 0.01). Deploying quality ventilation during CPR is a skill whose acquisition starts with effective training. Therefore, course instructors' capability to accurately evaluate attendees' ventilation maneuvers is crucial.

Tracking Tidal Volume From Holter and Wearable Armband Electrocardiogram Monitoring.

A novel method for tracking the tidal volume (TV) from electrocardiogram (ECG) is presented. The method is based on the amplitude of ECG-derived respiration (EDR) signals. Three different morphology-based EDR signals and three different amplitude estimation methods have been studied, leading to a total of 9 amplitude-EDR (AEDR) signals per ECG channel. The potential of these AEDR signals to track the changes in TV was analyzed. These methods do not need a calibration process. In addition, a personalized-calibration approach for TV estimation is proposed, based on a linear model that uses all AEDR signals from a device. All methods have been validated with two different ECG devices: a commercial Holter monitor, and a custom-made wearable armband. The lowest errors for the personalized-calibration methods, compared to a reference TV, were -3.48% [-17.41% / 12.93%] (median [first quartile / third quartile]) for the Holter monitor, and 0.28% [-10.90% / 17.15%] for the armband. On the other hand, medians of correlations to the reference TV were higher than 0.8 for uncalibrated methods, while they were higher than 0.9 for personal-calibrated methods. These results suggest that TV changes can be tracked from ECG using either a conventional (Holter) setup, or our custom-made wearable armband. These results also suggest that the methods are not as reliable in applications that induce small changes in TV, but they can be potentially useful for detecting large changes in TV, such as sleep apnea/hypopnea and/or exacerbations of a chronic respiratory disease.

Respiratory and chest wall mechanics in very preterm infants.

Data on static compliance of the chest wall (Ccw) in preterm infants are scarce. We characterized the static compliance of the lung (CL) and Ccw to determine their relative contribution to static compliance of the respiratory system (Crs) in very preterm infants at 36 wk postmenstrual age (PMA). We also aimed to investigate how these compliances were influenced by the presence of bronchopulmonary dysplasia (BPD) and impacted breathing variables. Airway opening pressure, esophageal pressure, and tidal volume (VT) were measured simultaneously during a short apnea evoked by the Hering-Breuer reflex. We computed tidal breathing variables, airway resistance (R), and dynamic lung compliance (CL,dyn), inspiratory capacity (IC), and Crs, CL, and Ccw. Functional residual capacity was assessed by the multiple breath washout technique (FRCmbw). Breathing variables, compliances, and lung volumes were adjusted for body weight. Twenty-three preterm infants born at 27.2 ± 2.0 wk gestational age (GA) were studied at 36.6 ± 0.6 wk PMA. Median and interquartile range (IQR) Crs/kg is 0.69 (0.6), CL/kg 0.95 (1.0), and Ccw/kg 3.0 (2.4). Infants with BPD (n = 11) had lower Crs/kg (P = 0.013), CL/kg (P = 0.019), and Ccw/kg (P = 0.027) compared with infants without BPD. Ccw/CL ratio was equal between groups. FRCmbw/kg (P = 0.044) and IC/kg (P = 0.005) were decreased in infants with BPD. Infants with BPD have reduced static compliance of the respiratory system, the lungs, and chest wall. Decreased Crs, CL, and Ccw in infants with BPD explain the lower FRC and IC seen in these infants.NEW & NOTEWORTHY Data on chest wall compliance in very preterm infants in the postsurfactant era are scarce. To our knowledge, we are the first group to report data on static respiratory system compliance (Crs), lung compliance (CL), and chest wall compliance (Ccw) in preterm infants with and without bronchopulmonary dysplasia (BPD) in the postsurfactant era.

Obesity-related reduced spirometry and altered breathing pattern are associated with mechanical disadvantage of the diaphragm.

The aim of this study was to characterize the breathing patterns of individuals with obesity during routine activities such as sitting and standing, and to identify potential contributors to alterations in these patterns. Measurements performed in 20 male subjects with obesity (BMI, 31.8±1.5 kg/m2) and 20 controls (BMI, 23.5±1.4 kg/m2) included anthropometric parameters, breathing-patterns in sitting and standing positions, spirometry, maximal respiratory pressures, and diaphragm B-mode ultrasonography. Individuals with obesity exhibited lower tidal volume and increased respiratory rate to maintain a similar minute-ventilation (p<0.05). Subjects with obesity demonstrated impaired spirometry and respiratory muscle strength, with inspiratory functions being notably compromised (p<0.05). Individuals with obesity had a greater diaphragm thickness at end inspiration but lower thickening-fraction at end quiet and forced breathings and reduced diaphragmatic displacement and excursion during maximal breaths (p<0.05). BMI was negatively associated with all respiratory function markers (p<0.05). Individuals with obesity exhibit a higher respiratory rate but lower tidal volume, likely to accommodate decreased compliance and excess thoracic and abdominal fat, further hindering inspiratory function. Moreover, increased adiposity is associated with a thicker but weaker diaphragm, primarily due to the diaphragm's mechanical disadvantage rather than its intrinsic inability to generate force.

Comparison of volume-controlled ventilation, pressure-controlled ventilation and pressure-controlled ventilation-volume guaranteed in infants and young children in the prone position: A prospective randomized study.

STUDY OBJECTIVE: To explore if the pressure-controlled ventilation (PCV) and pressure-controlled ventilation-volume guaranteed (PCV-VG) modes are superior to volume-controlled ventilation (VCV) in optimizing intraoperative respiratory mechanics in infants and young children in the prone position. DESIGN: A single-center prospective randomized study. SETTING: Children's Hospital, Zhejiang University School of Medicine. PATIENTS: Pediatric patients aged 1 month to 3 years undergoing elective spinal cord detethering surgery. INTERVENTIONS: Patients were randomly allocated to the VCV group, PCV group and PCV-VG group. The target tidal volume (VT) was 8 mL/kg and the respiratory rate (RR) was adjusted to maintain a constant end tidal CO2. MEASUREMENTS: The primary outcome was intraoperative peak airway pressure (Ppeak). Secondary outcomes included other respiratory and ventilation variables, gas exchange values, serum lung injury biomarkers concentration, hemodynamic parameters and postoperative respiratory complications. MAIN RESULTS: A total of 120 patients were included in the final analysis (40 in each group). The VCV group showed higher Ppeak at T2 (10 min after prone positioning) and T3 (30 min after prone positioning) than the PCV and PCV-VG groups (T2: P = 0.015 and P = 0.002, respectively; T3: P = 0.007 and P = 0.009, respectively). The prone-related decrease in dynamic compliance was prevented by PCV and PCV-VG ventilation modalities at T2 and T3 than by VCV (T2: P = 0.008 and P = 0.015, respectively; T3: P = 0.015 and P = 0.014, respectively). Additionally, there were no significant differences in other secondary outcomes among the three groups. CONCLUSION: In infants and young children undergoing spinal cord detethering surgery in the prone position, PCV-VG may be a better ventilation mode due to its ability to mitigate the increase in Ppeak and decrease in Cdyn while maintaining consistent VT.

Volume-targeted ventilation.

Despite strong evidence of important benefits of volume-targeted ventilation, many high-risk extremely preterm infants continue to receive traditional pressure-controlled ventilation in the United States and elesewhere. Reluctance to abandon one's comfort zone, lack of suitable equipment and a lack of understanding of the subtleties of volume-targeted ventilation appear to contribute to the relatively slow uptake of volume-targeted ventilation. This review will underscore the benefits of using tidal volume as the primary control variable, to improve clinicians' understanding of the way volume-targeted ventilation interacts with the awake, breathing infant and to provide information about evidence-based tidal volume targets in various circmstances. Focus on underlying lung pathophysiology, individualized ventilator settings and tidal volume targets are essential to successful use of this approach thereby improving important clinical outcomes.

Infant Pulmonary Function Tests in Children with Airway Anomalies and Correlation with Bronchoscopy Findings.

OBJECTIVES: To evaluate the role infant pulmonary function tests (Tidal Breathing Flow Volume Loops, TBFVL) in children with airway anomalies and to correlate the TBFVL so obtained with bronchoscopy findings. METHODS: In this prospective cohort study, we enrolled children aged 0-2 years with airway anomalies and performed TBFVL and bronchoscopy. The primary outcome measure was graphic pattern of TBFVL in laryngomalacia. Secondary outcome measures were types of TBFVL results in various airway anomalies and controls. RESULTS: Out of 53 children enrolled, 28 (52.3%) had laryngomalacia. Pattern 3 (fluttering of inspiratory limb) was commonest TBFVL pattern in laryngomalacia. Among TBFVL parameters, the ratio of inspiratory time to expiratory time (Ti/Te) and tPTEF/tE was significantly high in children with isolated laryngomalacia compared to controls. At six months of follow-up, TBFVL pattern 1 (normal) became the commonest pattern. CONCLUSION: A particular type of airway anomaly may have a characteristic graphic pattern in TBFVL and TBFVL pattern may indicate improvement in airway anomalies in follow-up.

Tidal expiratory flow limitation during exercise is unrelated to peripheral hypercapnic chemosensitivity.

We sought to determine if peripheral hypercapnic chemosensitivity is related to expiratory flow limitation (EFL) during exercise. Twenty participants completed one testing day which consisted of peripheral hypercapnic chemosensitivity testing and a maximal exercise test to exhaustion. The chemosensitivity testing consisting of two breaths of 10% CO2 (O2∼21%) repeated 5 times during seated rest and the first 2 exercise intensities during the maximal exercise test. Following chemosensitivity testing, participants continued cycling with the intensity increasing 20 W every 1.5 minutes till exhaustion. Maximal expiratory flow-volume curves were derived from forced expiratory capacity maneuvers performed before and after exercise at varying efforts. Inspiratory capacity maneuvers were performed during each exercise stage to determine EFL. There was no difference between the EFL and non-EFL hypercapnic chemoresponse (mean response during exercise 0.96 ± 0.46 and 0.91 ± 0.33 l min-1 mmHg-1, p=0.783). Peripheral hypercapnic chemosensitivity during mild exercise does not appear to be related to the development of EFL during exercise.

Mechanisms and consequences of excess exercise ventilation in fibrosing interstitial lung disease.

The causes and consequences of excess exercise ventilation (EEV) in patients with fibrosing interstitial lung disease (f-ILD) were explored. Twenty-eight adults with f-ILD and 13 controls performed an incremental cardiopulmonary exercise test. EEV was defined as ventilation-carbon dioxide output (⩒E-⩒CO2) slope ≥36 L/L. Patients showed lower pulmonary function and exercise capacity compared to controls. Lower DLCO was related to higher ⩒E-⩒CO2 slope in patients (P<0.05). 13/28 patients (46.4%) showed EEV, reporting higher dyspnea scores (P=0.033). Patients with EEV showed a higher dead space (VD)/tidal volume (VT) ratio while O2 saturation dropped to a greater extent during exercise compared to those without EEV. Higher breathing frequency and VT/inspiratory capacity ratio were observed during exercise in the former group (P<0.05). An exaggerated ventilatory response to exercise in patients with f-ILD is associated with a blunted decrease in the wasted ventilation in the physiological dead space and greater hypoxemia, prompting higher inspiratory constraints and breathlessness.

Sports Bra Restriction on Respiratory Mechanics during Exercise.

PURPOSE: We set out to understand how underband tightness or pressure of a sports bra relates to respiratory function and the mechanical work of breathing ( during exercise. Our secondary purpose was to quantify the effects of underband pressure on O 2 during submaximal running. METHODS: Nine highly trained female runners with normal pulmonary function completed maximal and submaximal running in three levels of underband restriction: loose, self-selected, and tight. RESULTS: During maximal exercise, we observed a significantly greater during the tight condition (350 ± 78 J·min -1 ) compared with the loose condition (301 ± 78 J·min -1 ; P < 0.05), and a 5% increase in minute ventilation ( ) during the tight condition compared with the loose condition ( P < 0.05). The pattern of breathing also differed between the two conditions; the greater maximal during the tight condition was achieved by a higher breathing frequency (57 ± 6 vs. 52 ± 7 breaths·min -1 ; P < 0.05), despite tidal volume being significantly lower in the tight condition compared with the loose condition (1.97 ± 0.20 vs. 2.05 ± 0.23 L; P < 0.05). During steady-state submaximal running, O 2 increased 1.3 ± 1.1% (range: -0.3 to 3.2%, P < 0.05) in the tight condition compared with the loose condition. CONCLUSIONS: Respiratory function may become compromised by the pressure exerted by the underband of a sports bra when women self-select their bra size. In the current study, loosening the underband pressure resulted in a decreased work of breathing, changed the ventilatory breathing pattern to deeper, less frequent breaths, and decreased submaximal oxygen uptake (improved running economy). Our findings suggest sports bra underbands can impair breathing mechanics during exercise and influence whole-body metabolic rate.

Validation of three-dimensional thoracic electrical impedance tomography of horses during normal and increased tidal volumes.

Objective. Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3D EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing).Approach. Two-plane EIT data, using two electrode planes 20 cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3D EIT whereby tidal impedance variation (TIV), ventilated area, and right-left and ventral-dorsal centres of ventilation (CoVRLand CoVVD, respectively) were calculated in cranial, middle and caudal slices of lung, from data collected using the two planes of electrodes.Main results. There was a significant interaction of time and slice for TIV (p< 0.0001) with TIV increasing during rebreathing in both caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p= 0.0002). There were significant effects of time and slice on CoVVDwhereby the cranial slice was more ventrally distributed than the caudal slice (p< 0.0009 for the interaction).Significance. The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3D EIT can accurately represent lung anatomy and changes in ventilation distribution during rebreathing in standing sedate horses.

Comparison of pressure controlled, volume controlled, and volume guaranteed pressure controlled modes in prone position in patients operated for lumbar disc herniation: A randomized trial.

BACKGROUND: To compare pressure-controlled ventilation (PCV), volume-controlled ventilation (VCV), and pressure-controlled ventilation-volume guaranteed (PCV-VG) modes in patients undergoing spinal surgery in the prone position under general anesthesia. METHODS: The study included 78 patients aged 20 to 80 years, American Society of Anesthesiologists 1-2, scheduled for lumbar spinal surgery. Patients included in the study were randomly divided into 3 groups Group-VCV; Group-PCV; Group-PCV-VG. Standard anesthesia protocol was applied. In addition to routine monitoring, train of four and BIS monitoring were performed. All ventilation modes were set with a target tidal volume of 6 to 8 mL/kg, FiO2: 0.40-0.45 and a respiratory rate of normocarbia. Positive end-expiratory pressure: 5 cm H2O, inspiration/expiration ratio = 1:2, and the maximum airway pressure:40 cm H2O. Hemodynamic, respiratory variables and arterial blood gases was measured, 15 minutes after induction of anesthesia in the supine position (T1), after prone position 15 minutes (T2), 30 minutes (T3), 45 minutes (T4), 60 minutes (T5), 75 minutes (T6), 90 minutes (T7). RESULTS: There was no significant difference between the groups in patient characteristics. SAP, DAP, mean arterial pressure, and heart rate decreased after being placed in the prone position in all groups. Hemodynamic variables did not differ significantly between the groups. partial arterial oxygen pressure and arterial oxygen saturation levels in blood gas were found to be significantly higher in Group-PCV-VG compared to Group-PCV and Group-VCV in both the supine and prone positions. Ppeak and plateau airway pressure (Pplato) values increased and dynamic lung compliance (Cdyn) values decreased after placing the patients in the prone position in all groups. Lower Ppeak and Pplato values and higher Cdyn values were observed in both the supine and prone positions in the Group-PCV-VG group compared to the Group-PCV and Group-VCV groups. CONCLUSION: PCV-VG provides lower Ppeak and Pplato values, as well as better Cdyn, oxygenation values compared to PCV and VCV. So that PCV-VG may be an effective alternative mode of mechanical ventilation for patients in the prone position during lumbar spine surgery.