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ObjectiveTo apply electrical impedance tomography (EIT) technology to assess the lung regional ventilation distribution in patients admitted to the intensive care unit (ICU) after a cardiac surgery, and to analyze its value of predicting patients' short-term prognosis.MethodsData from 46 patients admitted to ICU after a cardiac surgery from January to November 2023 were retrospectively collected. Using EIT, we assessed the lung regional ventilation of four regions of interest (ROI) and analyzed its influence on patients' length of stay in ICU, mechanical ventilation duration and tracheal intubation duration.ResultsA total of 46 patients were selected, including 29 males and 17 females, with an average age of (58.2±9.5) years.The patients who received a cardiac surgery equal to or over 5 hours had worse ventilation in the dorsal region (ROI 4) (P=0.022). The patients with worse dorsal region ventilation (ROI 4 < 9%) had lower oxygenation index (P=0.025), longer mechanical ventilation duration (P=0.004), longer tracheal intubation duration (P=0.010), and longer ICU stay (P=0.018). A larger ROI 4 percent was a protective factor for patients' prognosis (OR=0.743, 95% CI: 0.587-0.941, P=0.014) after controlling for the impact of age, gender, length of surgery and acute physiology and chronic health evaluation (APACHE) score at the admission. With a cutoff value of 9.5%, ROI 4 had 85.7% sensitivity and 56.2% specificity to predict worse prognosis.The area under the curve (AUC) was 0.752 (95% CI: 0.599-0.905, P=0.007).ConclusionsThe length of a cardiac surgery influences patients' lung ventilation, which further impacts patients' prognosis. EIT can be used as a bedside tool to assess patients' lung ventilation and inform corresponding clinical interventions to improve patients' prognosis.

Abstract Background This aim of study was to introduce a diaphragm-based EIT-belt placement method based on diaphragm position by ultrasound, and to evaluate the difference between diaphragm-based EIT-belt placement and conventional EIT-belt placement. Method The diaphragm position (L 0) determined by ultrasound was taken as zero reference level. The direction of headward is defined as positive, and toward feet is negative. For EIT data collection, the electrode belt was placed at 7 different levels, respectively (denoted as L −2 cm, L 0, L 2cm, L 4cm, L 6cm, L 8cm, L 10cm) at supine position in healthy volunteers. The diaphragm-based EIT-belt level (L xcm) was defined where highest tidal impedance variation (TV) was achieved. Subsequently, EIT measurements were conducted at diaphragm-based EIT-belt levels and traditional EIT-belt level in 50 critically ill patients under mechanical ventilation. Result The highest TV was achieved at L6cm and the smallest at L −2 cm., so the L 6cm were taken as diaphragm-based EIT-belt level by ultrasound in 8 healthy volunteers. In 23 patients, the diaphragm-based EIT-belt plane agreed with the conventional planes (4th–6th ICS), which was defined as the Agreed group. Other patients were classified to the Disagreed group (above 4th ICS). The Disagreed group has a significantly higher BMI and lower global TV at the diaphragm-based EIT-belt plane compared to the Agreed group. Conclusions The diaphragm-based EIT-belt position by ultrasound was feasible and resulted in different belt positions compared to the conventional position in > 50% of the examined subjects, especially in patients with higher BMI. Further study is required to validate the impact on EIT images with this novel method on clinical management.

Background. The identification of early predictors of poor outcomes of new coronavirus infection is necessary for optimizing patient management algorithms for hospitalized patients with COVID-19. Aim. To study the role of chitotriosidase activity as a marker of unfavorable outcomes in COVID-19 hospitalized patients. Materials and methods. The prospective observational single-center study included 347 patients with COVID-19 hospitalized in university clinic. In addition to the standard laboratory analysis (complete blood count, C-reactive protein, ferritin, creatinine, international normalized ratio, etc.) the blood serum chitotriosidase activity was determined at all the patients on admission. Primary endpoints were mortality from all causes and performing invasive ventilation (IV) and/or non-invasive ventilation (NIV). This study was approved by the Local Ethics Committee №12-21 (Clinical Trial Registry: NCT04752085). Results. A total of 347 patients were enrolled in this study (average age 66 years, females 182 52.5%), 30 patients (8.6%) died during the hospitalization, 39 (11.2%) performed IV or NIV. Along with age more than 65 (odds ratio OR 10.81, 95% confidence interval CI 2.6444.22) and Neutrophil-Lymphocyte Ratio higher than 7 (OR 15.89, 95% CI 3.0981.65) chitotriosidase activity higher than 170 ng/hr/ml (OR 4.23, 95% CI 1.4512.35) were independent predictors of mortality during hospitalization. Neutrophil-Lymphocyte Ratio higher than 5.6 (OR 11.22, 95% CI 2.3753,1) and сhitotriosidase activity higher than 151 ng/hr/ml (OR 3.17, 95% CI 1.317.67) have been evaluated as predictors of performing IV/NIV. Conclusion. Chitotriosidase level more than 151 nmol/h/mL could be considered as an early predictor of severity and poor prognosis in hospitalized patients with COVID-19.

Military stress has a traumatic effect on mental and physical health, and disrupts the adaptive capabilities of the body, in particular, its ability to adequately respond to hypoxia. However, the specifics of the reaction of the cardiorespiratory system to dosed hypoxia in individuals who experiencing warrelated chronic stress (WRCS) have not yet been elucidated. The peculiarities of the reaction of the cardiorespiratory system to dosed hypoxia in women experiencing WRCS were clarified. It was shown that during breathing of atmospheric air, the blood saturation level, lung ventilation indicators, and hemodynamics did not differ significantly between women exposed to WRCS and those not exposed to it. However, during a controlled hypoxic test (breathing a gas mixture with 12% oxygen for 20 min), women experiencing WRCS experienced a more significant decrease in blood saturation, indicating a lower tolerance to hypoxia. This is also evidenced by a reduced lung ventilation response to controlled hypoxia in the WRCS group, where the increase in ventilation primarily occurred due to an elevation in breathing rate rather than tidal volume. At the same time, the hemodynamic response to hypoxia in women with WRCS was characterized by a more substantial increase in heart rate and systolic arterial pressure. Thus, it was established that in women who were in the state of HCV, the body's resistance to the effects of hypoxia decreases. At the same time, in conditions of hypoxia, the nature of their breathing changes, and the compensatory growth of pulmonary ventilation decreases, but the growth of hemodynamic indicators increases. [ABSTRACT FROM AUTHOR]

Background: This aim of study was to introduce a diaphragm-based EIT-belt placement method based on diaphragm position by ultrasound, and to evaluate the difference between diaphragm-based EIT-belt placement and conventional EIT-belt placement. Method: The diaphragm position (L0) determined by ultrasound was taken as zero reference level. The direction of headward is defined as positive, and toward feet is negative. For EIT data collection, the electrode belt was placed at 7 different levels, respectively (denoted as L−2 cm, L0, L2cm, L4cm, L6cm, L8cm, L10cm) at supine position in healthy volunteers. The diaphragm-based EIT-belt level (Lxcm) was defined where highest tidal impedance variation (TV) was achieved. Subsequently, EIT measurements were conducted at diaphragm-based EIT-belt levels and traditional EIT-belt level in 50 critically ill patients under mechanical ventilation. Result: The highest TV was achieved at L6cm and the smallest at L−2 cm., so the L6cm were taken as diaphragm-based EIT-belt level by ultrasound in 8 healthy volunteers. In 23 patients, the diaphragm-based EIT-belt plane agreed with the conventional planes (4th–6th ICS), which was defined as the Agreed group. Other patients were classified to the Disagreed group (above 4th ICS). The Disagreed group has a significantly higher BMI and lower global TV at the diaphragm-based EIT-belt plane compared to the Agreed group. Conclusions: The diaphragm-based EIT-belt position by ultrasound was feasible and resulted in different belt positions compared to the conventional position in > 50% of the examined subjects, especially in patients with higher BMI. Further study is required to validate the impact on EIT images with this novel method on clinical management. [ABSTRACT FROM AUTHOR]

Panel (a) shows an example from that reference where end-tidal carbon dioxide (ETCO2) is initially < 1 kPa for a sustained (>7 breath) period, but rises with improved cardiopulmonary resuscitation (CPR) quality and treatment (the patient may still die despite this). Keywords: blood gases; cardiac arrest; difficult intubation; hypoxia; lung ventilation EN blood gases cardiac arrest difficult intubation hypoxia lung ventilation 937 942 6 07/06/23 20230801 NES 230801 The principle that using waveform capnography is essential to confirm correct tracheal tube placement dates from the 1980s [[1]], and its mandatory use has been repeated in successive minimum monitoring guidelines [[2]]. Some cases of unrecognised oesophageal intubation highlighted the need to extend this principle to cardiopulmonary resuscitation (CPR), where it had been wrongly assumed that cardiac arrest would invariably result in a flat waveform making capnography useless, but this is not the case. [Extracted from the article]

– OBJECTIVE: The aim of this study was to evaluate the application value of lung ultrasound in monitoring bronchopulmonary dysplasia (BPD) and pulmonary artery pressure in premature infants. PATIENTS AND METHODS: A total of 98 preterm infants diagnosed with BPD in the Fourth Hospital in Shijiazhuang were recruited, and their disease severity was classified as mild (n=32), moderate (n=33), or severe BPD (n=33) based on gestational age and oxygen concentration. Lung ultrasonography of the children was performed. The correlation between lung ventilation scores and disease severity was statistically analyzed, and the discrete optimization results were documented. The pulmonary hypertension indexes of the three groups of children were compared. RESULTS: Aberrant alterations of the pleural line were observed in all included children, and the B-line rose as the disease progressed. The duration of invasive ventilation, medication, and hospital stay increased with disease exacerbation (p<0.05). The three groups significantly differed in terms of ultrasound pulmonary ventilation scores and clinical severity (p<0.05). Only mild BDP was identified by lung ultrasound on the first day of birth (T1), and severe BDP was detectable during the first and second week (T2-T3) as well as the third and fourth week (T4-T5). Severe BPD was associated with significantly higher levels of pulmonary hypertension indices vs. mild and moderate BPD (p<0.05). CONCLUSIONS: Pulmonary ultrasonography demonstrates great potential to predict pulmonary hypertension in children and assesses the disease severity. Pulmonary ultrasound allows for dynamical real-time observation of the pulmonary lesions in children with pulmonary hypertension, thereby revealing the severity of pulmonary hypertension in premature children. [ABSTRACT FROM AUTHOR]

Abstract Background Although high-frequency percussive ventilation (HFPV) improves gas exchange, concerns remain about tissue overdistension caused by the oscillations and consequent lung damage. We compared a modified percussive ventilation modality created by superimposing high-frequency oscillations to the conventional ventilation waveform during expiration only (eHFPV) with conventional mechanical ventilation (CMV) and standard HFPV. Methods Hypoxia and hypercapnia were induced by decreasing the frequency of CMV in New Zealand White rabbits (n = 10). Following steady-state CMV periods, percussive modalities with oscillations randomly introduced to the entire breathing cycle (HFPV) or to the expiratory phase alone (eHFPV) with varying amplitudes (2 or 4 cmH2O) and frequencies were used (5 or 10 Hz). The arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were determined. Volumetric capnography was used to evaluate the ventilation dead space fraction, phase 2 slope, and minute elimination of CO2. Respiratory mechanics were characterized by forced oscillations. Results The use of eHFPV with 5 Hz superimposed oscillation frequency and an amplitude of 4 cmH2O enhanced gas exchange similar to those observed after HFPV. These improvements in PaO2 (47.3 ± 5.5 vs. 58.6 ± 7.2 mmHg) and PaCO2 (54.7 ± 2.3 vs. 50.1 ± 2.9 mmHg) were associated with lower ventilation dead space and capnogram phase 2 slope, as well as enhanced minute CO2 elimination without altering respiratory mechanics. Conclusions These findings demonstrated improved gas exchange using eHFPV as a novel mechanical ventilation modality that combines the benefits of conventional and small-amplitude high-frequency oscillatory ventilation, owing to improved longitudinal gas transport rather than increased lung surface area available for gas exchange.

Purpose: Clinical ventilation studies are primarily performed with computerized tomography (CT) and more often with single-photon emission Computerized tomography (SPECT) using radiolabelled aerosols, both presenting certain limitations. Here, we investigate the use of the radiofluorinated gas [18F]SF6 as a positron emission tomography (PET) ventilation marker in an animal model of impaired lung ventilation. Procedures: Sprague–Dawley rats (n = 15) were randomly assigned to spontaneous ventilation (sham group), endotracheal administration of phosphate-buffered saline (PBS group), or endotracheal administration of lipopolysaccharide (LPS group). PET-[18F]SF6 images (10-min acquisition) were acquired at t = 48 h after LPS or PBS administration under mechanical ventilation. CT images were acquired after each PET session. Volumes of interest were manually delineated in the lungs on CT images, and voxel-by-voxel analysis was carried out on PET images to obtain the corresponding histograms. After the imaging sessions, lungs were harvested to conduct histological analysis. Results: Ventilation studies in sham animals showed uniform distribution of [18F]SF6 and fast elimination of the radioactivity after discontinuation of the administration. For PBS- and LPS-treated rats, ventilation defects were observed on PET images in some animals, identified as regions with low presence of the radiolabelled gas. Hypoventilated areas co-localized with regions with higher x-ray attenuation than healthy lungs on the CT images, suggesting the presence of oedema and, in some cases, atelectasis. Histograms obtained from PET images showed quasi-Gaussian distributions for control animals, while PBS- and LPS-treated animals demonstrated the presence of hypoventilated voxels. Deviation of the histograms from Gaussian distribution correlated with histological score was obtained by ex vivo histological analysis. Conclusions: [18F]SF6 is an appropriate marker of regional lung ventilation and may find application in the early diagnose of acute lung disease. [ABSTRACT FROM AUTHOR]

Measuring cardiorespiratory variables can be challenging in developing animals, especially when they use bimodal gas exchange to maintain metabolic activity. In tadpoles, gas exchange may occur through the integument and gills when breathing in the water and through the lungs when breathing air, with varying contributions of each respiratory structure during development. The interaction between aquatic and air breathing results in a complex physiological response that may affect the cardiac cycle. Measuring the heart rate (fH) together with aquatic and aerial gas exchange in anurans during their development can be challenging, since it may involve handling small animals and/or a certain degree of invasiveness (i.e., surgery to implant electrodes). Here, we evaluated concomitantly aquatic and aerial gas exchange, lung ventilation, and fH in three stages of development of the bullfrog Lithobates catesbeianus (Shaw, 1802). We built a novel, noninvasive, closed respirometry system capable of measuring fH, aerial and aquatic gas exchange simultaneously in animals of different sizes. Our integrative analysis revealed a decrease in the heart rate and an increase in oxygen consumption during the developmental stages of the bullfrog, but there was no adjustment of heart rate after or during air breathing. Moreover, tadpoles in metamorphosis showed higher oxygen consumption in air than in water, while aquatic breathing was responsible for releasing CO2. Our results are consistent with those found in the literature, yet our study represents the first non-invasive investigation to evaluate bimodal gas exchange and heart rate simultaneously. Moreover, our setup holds potential for further advancements that would allow for controlled water and air composition. This tool could greatly facilitate the investigation of how cardiorespiratory physiology responds to varying environmental conditions. [ABSTRACT FROM AUTHOR]

Background: Although high-frequency percussive ventilation (HFPV) improves gas exchange, concerns remain about tissue overdistension caused by the oscillations and consequent lung damage. We compared a modified percussive ventilation modality created by superimposing high-frequency oscillations to the conventional ventilation waveform during expiration only (eHFPV) with conventional mechanical ventilation (CMV) and standard HFPV.Methods: Hypoxia and hypercapnia were induced by decreasing the frequency of CMV in New Zealand White rabbits (n = 10). Following steady-state CMV periods, percussive modalities with oscillations randomly introduced to the entire breathing cycle (HFPV) or to the expiratory phase alone (eHFPV) with varying amplitudes (2 or 4 cmH2O) and frequencies were used (5 or 10 Hz). The arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2) were determined. Volumetric capnography was used to evaluate the ventilation dead space fraction, phase 2 slope, and minute elimination of CO2. Respiratory mechanics were characterized by forced oscillations.Results: The use of eHFPV with 5 Hz superimposed oscillation frequency and an amplitude of 4 cmH2O enhanced gas exchange similar to those observed after HFPV. These improvements in PaO2 (47.3 ± 5.5 vs. 58.6 ± 7.2 mmHg) and PaCO2 (54.7 ± 2.3 vs. 50.1 ± 2.9 mmHg) were associated with lower ventilation dead space and capnogram phase 2 slope, as well as enhanced minute CO2 elimination without altering respiratory mechanics.Conclusions: These findings demonstrated improved gas exchange using eHFPV as a novel mechanical ventilation modality that combines the benefits of conventional and small-amplitude high-frequency oscillatory ventilation, owing to improved longitudinal gas transport rather than increased lung surface area available for gas exchange. [ABSTRACT FROM AUTHOR]

Abstract Background The aim of this study was to validate whether regional ventilation and perfusion data measured by electrical impedance tomography (EIT) with saline bolus could discriminate three broad acute respiratory failure (ARF) etiologies. Methods Perfusion image was generated from EIT-based impedance–time curves caused by 10 ml 10% NaCl injection during a respiratory hold. Ventilation image was captured before the breath holding period under regular mechanical ventilation. DeadSpace % , Shunt % and VQMatch % were calculated based on lung perfusion and ventilation images. Ventilation and perfusion maps were divided into four cross-quadrants (lower left and right, upper left and right). Regional distribution defects of each quadrant were scored as 0 (distribution% ≥ 15%), 1 (15% > distribution% ≥ 10%) and 2 (distribution%

Objective To evaluate the application effect of continuous medium and low flow oxygen supply to nonventilated lung in elderly patients with thoracoscopic radical surgery for lung cancer and its effect on the postoperative pulmonary complications (PPC). Methods A total of 100 elderly patients undergoing elective thoracoscopic radical resection of lung cancer were selected and randomly divided into the observation group and control group，with 50 cases in each group. In the observation group，1-4 L/min of oxygen was given to the non-ventilated side lung after one-lung ventilation （OLV），while patients in the control group received no special treatment. The operation time，anesthesia time，one-lung ventilation time，intraoperative blood loss，respiratory recovery time，wake-up time，tracheal intubation time，operator satisfaction during OLV，and arterial partial pressure of oxygen（PaO2 ）and arterial partial pressure of carbon dioxide（Pa‐ CO2）immediately after induction of anesthesia（T0）and 30 min（T1)，1 h（T2 ）and 2 h（T3 ）after OLV，and preoperative and postoperative white blood cell count，neutrophil count and percentage of neutrophils on postoperative 1st and 3rd days， postoperative PPC and adverse reactions，the 15-item Quality of Recovery Scale（QoR-15）score on postoperative 1st and 2nd days，and post-anesthesia care unit（PACU）stay time and length of hospital stay were compared between the two groups. Results There were no significant differences in the operation time，anesthesia time，one-lung ventilation time，intraoperative blood loss，respiratory recovery time，wake-up time，tracheal intubation time，or operator satisfaction during OLV between the two groups（all P>0. 05）. Compared with T0 in the same group，PaO2 decreased and PaCO2 increased in both groups from T1 to T3，and the changes in the control group were more obvious（all P<0. 05）. Compared with the same group before operation，the white blood cell count，neutrophil count and the percentage of neutrophils in the two groups in‐ creased on postoperative 1st and 3rd days，and the increase was more obvious in the control group（all P<0. 05）. The total incidence of postoperative PPC was 14%（7/50）in the observation group and 34%（17/50）in the control group，with statistically significant difference between the two groups（P<0. 05）. No statistically significant difference was found in the incidence of adverse reactions after operation between the two groups（P>0. 05）. The postoperative PACU stay time and hospital stay time in the observation group were shorter than those in the control group，and the QoR-15 scores on postoperative 1st and 2nd days were higher than those in the control group（all P<0. 05）. Conclusion In elderly patients undergoing thoracoscopic radical resection of lung cancer，continuous medium and low flow oxygen supply to the non-ventilated lung can improve oxygenation function，inhibit postoperative inflammatory response，reduce the occurrence of PPC，and promote postoperative recovery，with high safety. 2 [ABSTRACT FROM AUTHOR]

Chest auscultation is the first procedure performed to detect endotracheal tube malpositioning but conventional stethoscopes do not conform to the personal protective equipment (PPE) protocol during the COVID-19 pandemic. This double-blinded randomized controlled trial evaluated the feasibility of using ear-contactless electronic stethoscope to identify endobronchial blocker established selective lung ventilation, simulating endobronchial intubation during thoracic surgery with full PPE. Conventional and electronic auscultation was performed without and with full PPE, respectively, of 50 patients with selective lung ventilation. The rates of correct ventilation status detection were 86 and 88% in the conventional and electronic auscultation groups (p = 1.00). Electronic auscultation revealed a positive predictive value of 87% (95% CI 77 to 93%), and a negative predictive value of 91% (95% CI 58 to 99%), comparable to the results for conventional auscultation. For detection of the true unilateral lung ventilation, the F1 score and the phi were 0.904 and 0.654, respectively for conventional auscultation; were 0.919 and 0.706, respectively for electronic auscultation. Furthermore, the user experience questionnaire revealed that the majority of participant anesthesiologists (90.5%) rated the audio quality of electronic lung sounds as comparable or superior to that of conventional acoustic lung sounds. In conclusion, electronic auscultation assessments of ventilation status as examined during thoracic surgery in full PPE were comparable in accuracy to corresponding conventional auscultation assessments made without PPE. Users reported satisfactory experience with the electronic stethoscope.

Background: Lung compliance, a biomarker of pulmonary fibrosis, is generally measured globally. Hyperpolarized 129 Xe gas MRI offers the potential to evaluate lung compliance regionally, allowing for visualization of changes in lung compliance associated with fibrosis., Purpose: To assess global and regional lung compliance in a rat model of pulmonary fibrosis using hyperpolarized 129 Xe gas MRI., Study Type: Prospective., Animal Model: Twenty Sprague-Dawley male rats with bleomycin-induced fibrosis model (N = 10) and saline-treated controls (N = 10)., Field Strength/sequence: 7-T, fast low-angle shot (FLASH) sequence., Assessment: Lung compliance was determined by fitting lung volumes derived from segmented 129 Xe MRI with an iterative selection method, to corresponding airway pressures. Similarly, lung compliance was obtained with computed tomography for cross-validation. Direction-dependencies of lung compliance were characterized by regional lung compliance ratios (R) in different directions. Pulmonary function tests (PFTs) and histological analysis were used to validate the pulmonary fibrosis model and assess its correlation with 129 Xe lung compliance., Statistical Tests: Shapiro-Wilk tests, unpaired and paired t-tests, Mann-Whitney U and Wilcoxon signed-rank tests, and Pearson correlation coefficients. P < 0.05 was considered statistically significant., Results: For the entire lung, the global and regional lung compliance measured with 129 Xe gas MRI showed significant differences between the groups, and correlated with the global lung compliance measured using PFTs (global: r = 0.891; regional: r = 0.873). Additionally, for the control group, significant difference was found in mean regional compliance between areas, eg, 0.37 (0.32, 0.39) × 10 -4  mL/cm H 2 O and 0.47 (0.41, 0.56) × 10 -4  mL/cm H 2 O for apical and basal lung, respectively. The apical-basal direction R was 1.12 ± 0.09 and 1.35 ± 0.13 for fibrosis and control groups, respectively, indicating a significant difference., Data Conclusion: Our findings demonstrate the feasibility of using hyperpolarized gas MRI to assess regional lung compliance., Evidence Level: 2 TECHNICAL EFFICACY: Stage 1., (© 2024 International Society for Magnetic Resonance in Medicine.)

This collection of research articles was put together in honour of respiratory physiologist Professor Peter Frappell's (Frapps's) academic achievements. It encompasses various topics relating to the oxygen transport cascade, which was central to Frapps' career as a comparative physiologist. This issue highlights the diversity and outreach of his influence on the field and his pioneering spirit; promoting novel perspectives, methodologies and research techniques. This issue also demonstrates how Frapps' knowledge and scientific findings answered some of the fundamental questions within the field of respiratory physiology while creating and fostering a rather unique work atmosphere in the laboratories he led. We thank Frapps for the contributions he has made and the friendships he has nurtured over his career. Cheers, Frapps – we love you mate! [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to validate whether regional ventilation and perfusion data measured by electrical impedance tomography (EIT) with saline bolus could discriminate three broad acute respiratory failure (ARF) etiologies. Methods: Perfusion image was generated from EIT-based impedance–time curves caused by 10 ml 10% NaCl injection during a respiratory hold. Ventilation image was captured before the breath holding period under regular mechanical ventilation. DeadSpace%, Shunt% and VQMatch% were calculated based on lung perfusion and ventilation images. Ventilation and perfusion maps were divided into four cross-quadrants (lower left and right, upper left and right). Regional distribution defects of each quadrant were scored as 0 (distribution% ≥ 15%), 1 (15% > distribution% ≥ 10%) and 2 (distribution% < 10%). Data percentile distributions in the control group and clinical simplicity were taken into consideration when defining the scores. Overall defect scores (DefectV, DefectQ and DefectV+Q) were the sum of four cross-quadrants of the corresponding images. Results: A total of 108 ICU patients were prospectively included: 93 with ARF and 15 without as a control. PaO2/FiO2 was significantly correlated with VQMatch% (r = 0.324, P = 0.001). Three broad etiologies of ARF were identified based on clinical judgment: pulmonary embolism-related disease (PED, n = 14); diffuse lung involvement disease (DLD, n = 21) and focal lung involvement disease (FLD, n = 58). The PED group had a significantly higher DeadSpace% [40(24)% vs. 14(15)%, PED group vs. the rest of the subjects; median(interquartile range); P < 0.0001] and DefectQ score than the other groups [1(1) vs. 0(1), PED vs. the rest; P < 0.0001]. The DLD group had a significantly lower DefectV+Q score than the PED and FLD groups [0(1) vs. 2.5(2) vs. 3(3), DLD vs. PED vs. FLD; P < 0.0001]. The FLD group had a significantly higher DefectV score than the other groups [2(2) vs. 0(1), FLD vs. the rest; P < 0.0001]. The area under the receiver operating characteristic (AUC) for using DeadSpace% to identify PED was 0.894 in all ARF patients. The AUC for using the DefectV+Q score to identify DLD was 0.893. The AUC for using the DefectV score to identify FLD was 0.832. Conclusions: Our study showed that it was feasible to characterize three broad etiologies of ARF with EIT-based regional ventilation and perfusion. Further study is required to validate clinical applicability of this method. Trial registration clinicaltrials, NCT04081142. Registered 9 September 2019—retrospectively registered, https://clinicaltrials.gov/show/NCT04081142. [ABSTRACT FROM AUTHOR]

Background: Motion correction is mandatory for the functional Fourier decomposition magnetic resonance imaging (FD-MRI) of the lungs. Therefore, it is important to evaluate the quality of various image-registration algorithms for pulmonary FD-MRI and to determine their impact on FD-MRI outcome. Purpose: To evaluate different image-registration algorithms for FD-MRI in functional lung imaging. Material and Methods: Fifteen healthy volunteers were examined in a 1.5-T whole-body MR scanner (Magnetom Avanto, Siemens AG) with a non-contrast enhanced 2D TrueFISP pulse sequence in coronal view and free-breathing (acquisition time 45 s, 250 images). Three image-registration algorithms were used to compensate the spatial variation of the lungs (fMRLung 3.0, ANTs, and Elastix). Quality control for image registration was performed by edge detection (ED), quotient image criterion (QI), and dice similarity coefficient (DSC). Ventilation, perfusion, and a ventilation/perfusion quotient (V/Q) were calculated using the three registered datasets. Results: Average computing times for the three image-registration algorithms were 1.0 ± 1.6 min, 38.0 ± 13.5 min, and 354 ± 78 min for fMRLung, ANTs, and Elastix, respectively. No significant difference in the quality of motion correction provided by different image-registration algorithms occurred. Significant differences were observed between fMRLung- and Elastix-based perfusion values ​​of the left lung as well as fMRLung- and ANTs-based V/Q quotient of the right and the entire lung (P < 0.05). Other ventilation and perfusion values were not significantly different. Conclusion: The mandatory motion correction for functional FD-MRI of the lung can be achieved through different image-registration algorithms with consistent quality. However, a significantly difference in computing time between the image-registration algorithms still requires an optimization. [ABSTRACT FROM AUTHOR]

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The primary objective is to evaluate the potential dosimetric gains of performing functional avoidance‐based proton treatment planning using 4DCT derived ventilation imaging. 4DCT data of 31 patients from a prospective functional avoidance clinical trial were evaluated with intensity modulated proton therapy (IMPT) plans and compared with clinical volumetric modulated arc therapy (VMAT) plans. Dosimetric parameters were compared between standard and functional plans with IMPT and VMAT with one‐way analysis of variance and post hoc paired student t‐test. Normal Tissue Complication Probability (NTCP) models were employed to estimate the risk of two toxicity endpoints for healthy lung tissues. Dose degradation due to proton motion interplay effect was evaluated. Functional IMPT plans led to significant dose reduction to functional lung structures when compared with functional VMAT without significant dose increase to Organ at Risk (OAR) structures. When interplay effect is considered, no significant dose degradation was observed for the OARs or the clinical target volume (CTV) volumes for functional IMPT. Using fV20 as the dose metric and Grade 2+ pneumonitis as toxicity endpoint, there is a mean 5.7% reduction in Grade 2+ RP with the functional IMPT and as high as 26% in reduction for individual patient when compared to the standard IMPT planning. Functional IMPT was able to spare healthy lung tissue to avoid excess dose to normal structures while maintaining satisfying target coverage. NTCP calculation also shows that the risk of pulmonary complications can be further reduced with functional based IMPT. [ABSTRACT FROM AUTHOR]

Firefighters must meet certain physical requirements. This study compares the demands of a new firefighting-specific tasks test with an existing laboratory test. Thirty-five male subjects were tested. In both tests, the subjects wore a complete firefighting outfit including breathing apparatus, but not the usual facemask. Test durations were 8 min (existing test) vs ≈10 min (new test). Peak oxygen uptake was similar in the tests, ≈45 ml · kg−1 min−1. The time with an oxygen uptake above 35 ml kg−1 min−1 was longer in the new test, 6.4 vs 4.7 min. The results suggest that the new test is as demanding as the traditional test and offers the advantages of being more specific. The new test could therefore serve as an alternative to the existing test. Based on regression analysis of the two tests, a pass/fail time of 10 min 30 s is suggested. [ABSTRACT FROM AUTHOR]

To develop a stochastic five-lobe lung model and to compute particle deposition fractions in the five lobes, considering anatomical as well as ventilatory asymmetry. The stochastic five-lobe lung model was derived from an existing stochastic model for the whole lung, which implicitly contains information on the lobar airway structure. Differences in lobar ventilation and sequential filling of individual lobes were simulated by a stochastic lobar ventilation model. Deposition fractions of inhaled unit density particles in the five lobes were calculated by an updated version of the Monte Carlo deposition code Inhalation, Deposition, and Exhalation of Aerosols in the Lung (IDEAL). Simulations for defined exposure and breathing conditions revealed that the two lower lobes receive higher deposition and the two upper lobes lower deposition, compared to the average deposition for the whole lung. The resulting inter-lobar distribution of deposition fractions indicated that the non-uniform lung morphometry is the dominating effect, while non-uniform ventilation only slightly enhances the lobar differences. The relation between average lobe-specific deposition fractions and corresponding average values for the whole lung allowed the calculation of lobe-specific deposition weighting factors. Comparison with limited deposition measurements for upper vs. lower (U/L) and left vs. right (L/R) lobes revealed overall agreement between experimental and theoretical data. Calculations of the L/R deposition ratio for inhaled aerosol boli confirmed the hypothesis of Möller et al. that the right lung is less able to expand at the end of a breath because of the restrictive position of the liver. [ABSTRACT FROM AUTHOR]

Objective. Impedance pneumography (IP) has provided static assessments of subjects' breathing patterns in previous studies. Evaluating the feasibility and limitation of ambulatory IP based respiratory monitoring needs further investigation on clinically relevant exercise designs. The aim of this study was to evaluate the capacity of an advanced IP in ambulatory respiratory monitoring, and its predictive value in independent ventilatory capacity quantification during cardiopulmonary exercise testing (CPET). Approach. 35 volunteers were examined with the same calibration methodology and CPET exercise protocol comprising phases of rest, unloaded, incremental load, maximum load, recovery and further-recovery. In 3 or 4 deep breaths of calibration stage, thoracic impedance and criterion spirometric volume were simultaneously recorded to produce phase-specific prior calibration coefficients (CCs). The IP measurement during exercise protocol was converted by prior CCs to volume estimation curve and thus calculate minute ventilation (VE) independent from the spirometry approach. Main results. Across all measurements, the relative error of IP-derived VE (VE R ) and flowrate-derived VE (VE f ) was less than 13.8%. In Bland-Altman plots, the aggregate VE estimation bias was statistically insignificant for all 3 phases with pedaling exercise and the discrepancy between VE R and VE f fell within the 95% limits of agreement (95% LoA) for 34 or all subjects in each of all CPET phases. Significance. This work reinforces the independent use of IP as an accurate and robust alternative to flowmeter for applications in cycle ergometry CPET, which could significantly encourage the clinical use of IP and improve the convenience and comfort of CPET., (© 2024 Institute of Physics and Engineering in Medicine.)

Jie Wang,1,* Ruochen Wang,1,* Niannian Li,1 Xi Shen,2 Gang Huang,3 Jun Zhu,1,4 Dannong He1,4 1School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, People’s Republic of China; 2The Department of Ophthalmology, Ruijin Hospital, Shanghai Jiao Tong University, Shanghai, People’s Republic of China; 3Shanghai University of Medicine and Health Sciences, Shanghai, People’s Republic of China; 4National Engineering Research Center for Nanotechnology, Shanghai, People’s Republic of China *These authors contributed equally to this work Background: Hypoxemia is one of the most common pathological processes in various clinical diseases. Methods: A novel emulsion of poly(lactide-co-glycolide)-poly(ethylene glycol)/perfluorooctyl bromide has been developed to improve arterial hypoxemia through pulmonary drug delivery. Hypoxia-reoxygenation experiment was used to investigate the ability of the emulsion to supply oxygen and the saline lavage acute lung injury model was established to evaluate oxygen supply of the emulsion. Results: It has been demonstrated that an apparent increase has been detected in the cytotoxicity test of the emulsion, indicating its lower cell toxicity. A hypoxia-reoxygenation experiment uncovered the fact that notable cell growth was observed after reoxygenation with poly(lactide-co-glycolide)-poly(ethylene glycol)/perfluorooctyl bromide emulsion because of the ability of the emulsion to supply oxygen adequately and reasonably. Moreover, the level of intracellular reactive oxygen species was significantly enhanced during hypoxia, which further influenced the concentration and activity of hypoxia-inducible factor-1α (HIF-1α). Furthermore, the upregulated expression of HIF-1α during hypoxia has verified that certain emulsions can increase HIF-1α content and relieve hypoxia, which further indicates HIF-1α plays an essential role in improving cell viability. Afterwards, the saline lavage acute lung injury model was established to evaluate oxygen supply of the emulsion and the result shows considerable improvement of lung ventilation of rabbits. Conclusion: We recommend that the feedback relationship between reactive oxygen species and HIF-1 plays an essential role in improving cell viability. It is anticipated that the emulsion will be applied in the field of alleviating hypoxemia. Keywords: perfluorocarbon, oxygen concentration, hypoxia-reoxygenation, reactive oxygen species, hypoxia-inducible factor-1α, lung ventilation

Background: To determine the level of inspiratory pressure minimizing the risk of gastric insufflation while providing adequate pulmonary ventilation.Methods: In this prospective, randomized, double-blind study, patients were allocated to one of the two groups (P10, P15) defined by the inspiratory pressure applied during controlled-pressure ventilation: 10 and 15 cm H2O. Anesthesia was induced using propofol and sufentanil; no neuromuscular-blocking agent was administered. Once loss of eyelash reflex occurred, facemask ventilation was started for a 2-min period. The cross-sectional antral area was measured using ultrasonography before and after facemask ventilation. Respiratory parameters were recorded.Results: Forty patients were analyzed. Mean tidal volume was about 7 ml/kg in group P10, and was >11 ml/kg in group P15 in the same period. As indicated by ultrasonography test, the antral area in P15 group was markedly incresed compared with P10 group.Conclusion: Inspiratory pressure of 10 cm H2O allowed for reduced occurrence of gastric insufflation with proper lung ventilation during induction of anesthesia with sufentanil and propofol in nonparalyzed and nonobese patients. [ABSTRACT FROM AUTHOR]

Purpose. Physiologic demands of five common tasks in firefighting have been examined. Methods. Eight male volunteers, dressed up as smoke divers (+21 kg extra load), carried out the following tasks at constant pace for 5 min: walking at 1.4 m·s–1, walking (all walks at the same speed) while carrying a 10-kg ladder, walking carrying two hose packs of 16 kg together, walking carrying a 32-kg spreader tool and, finally, climbing up and down a ladder at a preset pace. A 5-min break separated each exercise. The heart rate, oxygen uptake and lung ventilation were measured continuously, and the blood lactate concentration was recorded after each task. Results. The end-exercise heart rate rose from 108 to 180 bpm from the first to last task, blood lactate concentration rose from 1 to 7 mmol·L–1, oxygen uptake rose from 19 to 48 ml·kg–1 min–1 and lung ventilation rose from 38 to 124 L·min–1. Discussion. Walking was an easy task even when dressed up as a smoke diver. Adding loads increased demands; ladder climbing taxed >90% of the subjects' aerobic power. Conclusions. The physiologic demands varied considerably between different tasks. [ABSTRACT FROM AUTHOR]

Several aspects of postnatal pulmonary adaption in the bovine neonate remain unclear, particularly the dynamics and regional ventilation of the lungs. We used electric impedance tomography (EIT) to measure changes in ventilation in the first 3 weeks of life in 20 non-sedated neonatal calves born without difficulty in sternal recumbency. Arterial blood gas variables were determined in the first 24 h after birth. Immediately after birth, dorsal parts of the lungs had 4.53% ± 2.82% nondependent silent spaces (NSS), and ventral parts had 5.23% ± 2.66% dependent silent spaces (DSS). The latter increased in the first hour, presumably because of gravity-driven ventral movement of residual amniotic fluid. The remaining lung regions had good ventilation immediately after birth, and the percentage of lung regions with high ventilation increased significantly during the study period. The centre of ventilation was always dorsal to and on the right of the theoretical centre of ventilation. The right lung was responsible for a significantly larger proportion of ventilation (63.84% ± 12.74%, p < 0.00001) compared with the left lung. In the right lung, the centrodorsal lung area was the most ventilated, whereas, in the left lung, it was the centroventral area. Tidal impedance changes, serving as a surrogate for tidal volume, increased in the first 3 weeks of life (p < 0.00001). This study shows the dynamic changes in lung ventilation in the bovine neonate according to EIT measurements. The findings form a basis for the recognition of structural and functional lung disorders in neonatal calves.

We have studied the reaction of the respiratory system to transcutaneous spinal cord stimulation inducing stepping movements of large and small amplitudes. We have shown that the small amplitude of the generated stepping movements was associated with a reduction of the tidal volume, and generated movements with a large amplitude resulted in the elevation of the expiratory flow. We have compared the reactions of the respiratory system during stepping movements induced by spinal cord stimulation and by voluntary efforts. It has been found that, during stepping movements induced by the spinal cord stimulation, lung ventilation increased through reduction of the inspiration and expiration times, while the expiratory flow increased. During voluntary stepping movements, the inspiration time decreased, while the inspiratory and expiratory flows increased. These effects can ensue from tonic activation of abdominal muscles, as well as from the summation of the effects of spinal stimulation and working hyperpnoea. [ABSTRACT FROM AUTHOR]

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Background: Deformable image registration (DIR)‐based lung ventilation mapping is attractive due to its simplicity, and also challenging due to its susceptibility to errors and uncertainties. In this study, we explored the use of 3D Hyperpolarized (HP) gas tagging MRI to evaluate DIR‐based lung ventilation. Method and Material: Three healthy volunteers included in this study underwent both 3D HP gas tagging MRI (t‐MRI) and 3D proton MRI (p‐MRI) using balanced steady‐state free precession pulse sequence at end of inhalation and end of exhalation. We first obtained the reference displacement vector fields (DVFs) from the t‐MRIs by tracking the motion of each tagging grid between the exhalation and the inhalation phases. Then, we determined DIR‐based DVFs from the p‐MRIs by registering the images at the two phases with two commercial DIR algorithms. Lung ventilations were calculated from both the reference DVFs and the DIR‐based DVFs using the Jacobian method and then compared using cross correlation and mutual information. Results: The DIR‐based lung ventilations calculated using p‐MRI varied considerably from the reference lung ventilations based on t‐MRI among all three subjects. The lung ventilations generated using Velocity AI were preferable for the better spatial homogeneity and accuracy compared to the ones using MIM, with higher average cross correlation (0.328 vs 0.262) and larger average mutual information (0.528 vs 0.323). Conclusion: We demonstrated that different DIR algorithms resulted in different lung ventilation maps due to underlining differences in the DVFs. HP gas tagging MRI provides a unique platform for evaluating DIR‐based lung ventilation. [ABSTRACT FROM AUTHOR]

Estimating the effect of microgravity/hypogravity on pulmonary ventilation function remains topical. Recently developed acoustic techniques based on the evaluation of the forced expiratory noise time (FETa) were hypothesized to be a promising tool for this aim. The aim of the protocol is to study the effect of two different modalities of bed rest space simulations (microgravity and lunar gravity) on FETa and spirometric indices. The FETa in the frequency band of 200–2000 Hz, recorded above human trachea, was evaluated. The 21st-day exposure to 6 degree head-down tilt (HDT) bed rest, simulating microgravity, and 9.6 degree head-up tilt (HUT) bed rest with head-zero tilt (HZT) rest intervals (HUT + HZT), simulating lunar gravity, in statistically identical subgroups of five and six healthy male volunteers, was studied. In the course of HDT bed rest, a significant elongation of FETa was found in relation to background measurements in “sitting” position (p = 0.016). The effect corresponded to a significant decrease of basic spirometric indices (p < 0.02). Moreover, FETa provided reliable discrimination of HDT and HUT + HZT bed rest tests (p = 0.018), while spirometric indices did not (p > 0.05). Based on previously found correlations (Korenbaum and Pochekutova, 2008; Malaeva et al., 2017), a FETa elongation in response to HDT bed rest was attributed to an increase of aerodynamic resistance of the respiratory tract. The technique seems promising to monitor human pulmonary ventilation dynamics in long-term space missions; however, new studies are welcome to verify it in real spaceflight.

Estimating the effect of microgravity/hypogravity on pulmonary ventilation function remains topical. Recently developed acoustic techniques based on the evaluation of the forced expiratory noise time (FETa) were hypothesized to be a promising tool for this aim. The aim of the protocol is to study the effect of two different modalities of bed rest space simulations (microgravity and lunar gravity) on FETa and spirometric indices. The FETa in the frequency band of 200–2000 Hz, recorded above human trachea, was evaluated. The 21st-day exposure to 6 degree head-down tilt (HDT) bed rest, simulating microgravity, and 9.6 degree head-up tilt (HUT) bed rest with head-zero tilt (HZT) rest intervals (HUT + HZT), simulating lunar gravity, in statistically identical subgroups of five and six healthy male volunteers, was studied. In the course of HDT bed rest, a significant elongation of FETa was found in relation to background measurements in "sitting" position (p = 0.016). The effect corresponded to a significant decrease of basic spirometric indices (p < 0.02). Moreover, FETa provided reliable discrimination of HDT and HUT + HZT bed rest tests (p = 0.018), while spirometric indices did not (p > 0.05). Based on previously found correlations (Korenbaum and Pochekutova, 2008; Malaeva et al., 2017), a FETa elongation in response to HDT bed rest was attributed to an increase of aerodynamic resistance of the respiratory tract. The technique seems promising to monitor human pulmonary ventilation dynamics in long-term space missions; however, new studies are welcome to verify it in real spaceflight. [ABSTRACT FROM AUTHOR]

Background: The number of obese patients undergoing surgery, either bariatric or non-bariatric, is steadily increasing. These patients are more labile to the perioperative complications, such as hypoxemia, hypercapnia, and atelectasis. Intraoperative protective ventilation consisting of low tidal volume, high PEEP and recruitment maneuvers resulted in alveolar recruitment and optimization of intraoperative respiratory mechanics. Objective: This study tested two strategies of mechanical ventilation in obese patients during pneumoperitoneum to conclude which is better as regard gas exchange optimization and hemodynamic stability. Methods: Study was a randomized prospective comparative control study which was carried out on 50 obese patients with BMI 30-50 kg/m2. Patients were prepared for laparoscopic cholecystectomy. Patient's selection according to attendees at time of operation as a single numbers were protective ventilation (group A) and a double numbers were conventional ventilation (group B). Results: Study showed significance between oxygenation in both groups. Post-operative oxygenation in protective ventilation (group A). Mean Post P (A-a) O2 in group A was 27.93 (±7.76) mmHg, while in group B was 35.82 (±11.98) mmHg, p value (0.022). Hemodynamic instability observed in 24% in group A, but only occurred in 8% in group B. Conclusion: Study found that protective ventilation was superior to conventional ventilation as it was associated with better oxygenation in the post-operative in obese laparoscopic cholecystectomy. In spite of it was very effective in optimizing gas exchange, but associated with more hemodynamic affection. [ABSTRACT FROM AUTHOR]

Background. Respiratory support is a vital method for temporary compensation of external breathing function in patients with severe traumatic brain injury. However, it is not always possible to deal with severe respiratory dysfunction even with the usage of up-to-date respiratory technologies. This work is aimed to find an answer how different pattern of mechanical ventilation influence on a treatment of patients with severe traumatic brain injury. Objective. The influence of respiratory support, as a main method for temporary compensation of external breathing function, on treatment result for patients with severe traumatic brain injury. Methods. Treatment results of 253 patients with severe traumatic brain injury of Ternopil University Hospital were evaluated due to the type of respiratory support used. The results were separately evaluated in alive and dead patients. Results. Mortality rate of patients depended on the type of mechanical ventilation that was used. The highest mortality (58.69 %) was in the group, when a patient was transferred to forced ventilation a volume control. The mortality rate was decreasing by 51.78% in case of adding PEEP. The strategy of using accessory lung ventilation patterns CPAP and BiPAP caused significant (in 1.48 times) decrease of mortality in this group of patients. Conclusion The survival of patients with severe traumatic brain injury, who were ventilated by the method of consistent combination of forced ventilation with pressure control (CРV) and 2 patterns of accessory lung ventilation: Constant Positive Airway Pressure (CPAP) and Biphasic positive airway pressure (BiPAP), is reliably higher than in the case of forced ventilation with volume control with Positive end-expiratory pressure.