End-expiratory Volume Research Articles

Impact of Fluid Balance on the Development of Lung Injury.

The pathophysiological relationship between fluid administration, fluid balance, and mechanical ventilation in the development of lung injury is unclear. To quantify the relative contribution of mechanical power and fluid balance in the development of lung injury. Thirty-nine healthy female pigs, divided into four groups, were ventilated for 48 hours with high (~18J/min) or low (~6J/min) mechanical power; and high (~4L) or low (~1L) targeted fluid balance. We measured physiological variables e.g., end-expiratory lung gas volume, respiratory-system mechanics, gas-exchange and hemodynamics, and pathological variables, i.e., lung weight, wet-to-dry ratio, and histology score of lung injury. End-expiratory lung gas volume, respiratory system elastance, strain and oxygenation significantly worsened in the two groups assigned to receive high fluid balance, irrespective of the mechanical power received. All four groups had similar lung weight (i.e., lung edema), lung wet-to-dry ratio and pathological variables. Animals with higher fluid balance developed more ascites, which was associated with a decrease in end-expiratory lung gas volume. In conclusion, our study did not detect a significant difference in lung injury between high and low mechanical power. Some damage is directly attributable to mechanical power, while additional injury appears to result indirectly from high fluid balance, which reduces end-expiratory lung gas volume, with ascites playing an important role in this process.

High flow nasal cannula and low level continuous positive airway pressure have different physiological effects during de novo acute hypoxemic respiratory failure

BackgroundLarge tidal volumes during de novo acute hypoxemic respiratory failure (AHRF) may promote patient self-inflicted lung injury. Tidal volume assessment under high flow nasal cannula (HFNC) is not routinely feasible at the bedside. Our objective was to determine whether tidal volume during low-level continuous positive airway pressure (CPAP) could predict tidal volume during HFNC and to compare the physiological effects of HFNC and low-level CPAP.MethodsProspective, single-center study including 29 de novo AHRF patients treated with HFNC (50 to 60 L.min− 1). Patients were monitored using electrical impedance tomography during HFNC then CPAP at 4 cmH2O. Tidal volume during HFNC was calculated based on tidal impedance variation. The ability of tidal volume under low-level CPAP to predict tidal volume under HFNC was explored using Bland-Altman analysis. CPAP and HFNC were compared in terms of tidal volume, minute ventilation, respiratory comfort, dyspnea, oxygenation, ventilation distribution, end-expiratory lung volume, thoraco-abdominal asynchrony and recruitment.ResultsUnder HFNC, patients had a tidal volume of 6.6 (5.9–8.7) mL.kg− 1 PBW. 20 (69%) patients exhibited a tidal volume between 4 and 8 mL.kg− 1 PBW, while in 5 (17%) patients it exceeded 9 mL.kg− 1 PBW. Tidal volume under CPAP was higher (9.4 (8.3–11) mL.kg− 1 PBW, p < 0.001). Tidal volumes under CPAP and under HFNC were modestly correlated (Spearman r = 0.50, p = 0.005). Bland-Altman analysis showed a bias of 2.4 mL.kg− 1, with limits of agreement ranging from − 1.1 mL.kg− 1to 5.9 mL.kg− 1. Nevertheless, a larger (> 11.5 mL.kg− 1 PBW ) tidal volume under low-level CPAP predicted a larger (> 9 mL.kg− 1 PBW ) tidal volume under HFNC with 80% sensitivity and 96% specificity. Low-level CPAP was associated with increased minute ventilation, end-expiratory lung volume, and oxygenation as compared to HFNC. It decreased signs of respiratory distress in the most severe patients but was associated with lower comfort compared to HFNC.ConclusionAmong ICU patients with de novo AHRF, tidal volume under HFNC was mostly protective. Tidal volume during CPAP at 4 cmH2O did not predict tidal volume during HFNC. Such low-level CPAP was associated with increased tidal volume, minute ventilation, end-expiratory volume, and oxygenation.Trial registrationClinicalTrials.gov ID NCT03919331. Registration date: 2019-03-26.

Outcomes of a Single Transverse Chest Roll for Prone Positioning Technique During Percutaneous Nephrolithotomy

ObjectiveTo compare anesthetic parameters using a novel prone single transverse chest roll technique (STR) to the standard thoraco-pelvic dual transverse roll technique (DTR). MethodsA retrospective review of 441 patients who underwent PCNL between 2018 to 2022 was performed. A total of 4 surgeons were included—surgeon 1 utilized the STR technique while surgeons 2, 3, and 4 used the DTR technique. Anesthetic parameters including end tidal CO2 (ETCO2), mean arterial pressure (MAP), peak airway pressure (Ppeak), plateau airway pressure (Pplat), positive end expiratory pressure (PEEP), oxygen saturation (SpO2), and tidal volume (TV) were compared between both groups at 0 (supine), 15, 30, and 60 minutes post-intubation intervals. Mixed effects regression models with interaction and pairwise comparisons were made between both groups (p<0.05). ResultsA total of 581 PCNLs were performed with 199 using STR and 382 using DTR. Surgery duration, ASA class, and age were similar amongst the STR and DTR groups. Estimated blood loss (59cc vs 83cc, p=0.007) and length of stay (77 hrs vs 163 hrs, p=<0.001) was significantly lower in the STR group. There was a significantly lower Ppeak, Pplat and TV in the STR compared to DTR group at 0, 15, 30, and 60 minutes (p<0.001). ConclusionUsage of a single transverse chest roll during prone PCNL appears to be a safe positioning method. STR patients had lower Ppeak and Pplat at all timepoints, which has been shown to be predictive of lower blood loss.

Quantitative CT lung volumetry and densitometry in pediatric pectus excavatum.

The purpose of this study was to evaluate the quantitative computed tomography (CT) volumetry and densitometry and in pediatric patients with pectus excavatum (PE). We measured pectus index (PI) and separated inspiratory and expiratory lung volumes and densities. We obtained the total lung volume (TLV) and mean lung density (MLD) during inspiration and expiration, and the ratio of end expiratory to inspiratory volume (E/I volume) and MLD (E/I density) were calculated. The difference between inspiratory and end expiratory volume (I-E volume) and MLD (I-E density) were also calculated. A total of 199 patients, including 164 PE patients and 35 controls, were included in this study. The result shows that the PE group had lower inspiratory TLV (mean, 2670.76±1364.22 ml) than the control group (3219.57±1313.87 ml; p = 0.027). In the PE group, the inspiratory (-787.21±52.27 HU vs. -804.94±63.3 HU) and expiratory MLD (-704.51±55.41 HU vs. -675.83±64.62 HU) were significantly lower than the indices obtained from the control group (p = 0.006). In addition, significantly lower values of TLV and MLD difference and higher value of TLV and MLD ratio were found in the PE group (p <0.0001). PE patients were divided into severe vs. mild groups based on the PI cutoff value of 3.5. The inspiratory MLD and TLV ratio in the severe PE group were lower than those in the mild PE group, respectively (p <0.05). In conclusion, quantitative pulmonary evaluation through CT in pediatric PE patients may provide further information in assessing the functional changes in lung parenchyma as a result of chest wall deformity.

Safety and efficacy of high flow nasal canula in patients with mild hypercapnia

ContextHigh flow nasal canula is usually used for management of acute hypoxemic failure; however, it may have a potential therapeutic benefits in hypercapnia as it can alter tidal volume, end expiratory volume, positive end expiratory pressure, and respiratory rate.AimEvaluate safety and efficacy of application HFNC (high flow nasal canula) for patients with mild hypercapnia.Settings and designA prospective interventional study.Patients and methodsOver six months, thirty eight patients were enrolled, with mild hypercapnia and PH level not less 7.30 and PaCo2 not more 60 mmhg; with applying HFNC, serial checking of arterial blood gases was done. Checkpoints were at 2 h, 12 h, 24 h, and 48 h post application of HFNC. HFNC can be shifted to NIV or invasive MV at any time whenever indicated.ResultsPrimary pulmonary disorder was chronic obstructive pulmonary disorder in (22 patients) and (16 patients) had interstitial lung disease. For PH in overall, mean values had changed from 7.33 until reached 7.37 at 48 h post HFNC with calculation of P value at each checkpoint from baseline value; significant changes were recorded at 24 h and 48 h post HFNC application. A similar observation was observed for PaCO2. No significant changes were observed at any checkpoint for HCO3.ConclusionHigh flow nasal canula is safe in cases with mild hypercapnia with a considerable success rate and a proven high efficacy.Trial registrationClinicaltrials.gov/NCT05948527, Registered 14 July 2023—Retrospectively registered, https://www.clinicaltrials.gov/NCT05948527.

The effect intraoperative positive end expiratory pressure and tidal volume on postoperative acute kidney injury after orthopedic surgery.

To test whether higher intraoperative PEEP levels and/or higher TV levels are associated with higher incidence of postoperative AKI within the first postoperative week, in adult patients having orthopedic surgeries under general anesthesia. We conducted a sub analysis of a non-randomized alternating intervention cross over study performed in patients undergoing orthopedic surgery under general anesthesia at Cleveland Clinic, Cleveland, OH. We included four different combinations of PEEP (5 or 8 cm H2 O) and TV (6 or 10 mL/kg of PBW) that alternated each week in the six orthopedic operating rooms. Our primary outcome was postoperative AKI defined by the KDIGO criteria with baseline creatinine as the closest preoperative value to the time of surgery obtained within 30 days and postoperative value as the highest creatinine value within 7 days after surgery. Secondary outcome was the maximum postoperative in-hospital creatinine level within seven postoperative days. A total of 1933 patients were included in the analysis. The incidence of AKI was 6.8% in the study population and similar in high TV versus low TV group and high PEEP versus low PEEP group. Neither TV nor PEEP significantly impacted AKI incidence. The estimated odds ratio of AKI comparing TV = 6 mL/kg to TV = 10 mL/kg was 0.96 (97.5% CI: 0.63, 1.46; p = .811); while the estimated odds ratio of AKI comparing PEEP = 5cm H2 O to PEEP = 8cm H2 O was 0.92 (97.5% CI: 0.60, 1.39; p = .623). No interaction was found between TV and PEEP on AKI. Additionally, neither TV nor PEEP had a significant effect on the seven postoperative day creatinine levels. Higher levels of PEEP or TV during mechanical ventilation in adult patients undergoing orthopedic surgeries under general anesthesia do not increase the odds of developing postoperative AKI within the narrow limits studied.

A primer for the student joining the adult cardiac surgery service tomorrow: Primer 1 of 7

A primer for the student joining the adult cardiac surgery service tomorrow: Primer 1 of 7

Quantitative Magnetic Resonance Imaging of the epicardial adipose tissue with free-running cardiac Dixon

There is a growing interest to better understand the pathophysiological role of cardiac fat towards cardiovascular degradation in metabolic diseases. As epicardial adipose tissue (EAT) can become an inflammatory substrate under pathological conditions, emerging therapies are aiming at modulating its metabolic functions. However, there is a lack of non-invasive tools that can probe EAT, which is thin and moves with cardiac and respiratory motion. This study aims at developing quantitative MRI biomarkers that can characterize EAT. As detailed in the Fig. 1, a custom-built free-running Dixon-MRI technique enabled high resolution mapping of proton density fat-fraction (PDFF) and R2*, free-breathing, in the heart. Cardiac Dixon MRI was implemented on a 3 T MRI with a self-navigated gradient echo radial sequence (Fig. 1.1) acquiring N = 13-echo bipolar 3D (TE1/ΔTE = 1.12/1.07ms). The “free-running’ self-navigation (Fig. 1.2) reconstructed 4 respiratory and 8-12 cardiac phases of 100 ms. Measurements were performed on end-expiratory peak-systole volume. K-space trajectories were corrected (Fig. 1.3) with the gradient impulse function (GIRF). The 5D reconstruction (Fig. 1.4) of volumes was performed by Compressed Sensing followed by iterative least-square IDEAL water-fat separation (Fig. 1.5). Eventually, R2*&PDFF 3D maps (overlayed in Fig. 1 over echo TE1 image) are resolved in cardiac and respiratory time. The sequence proved highly accurate and precise with mean biases of PDFF and R2* estimated by simulation under 0.05% and 0.05 s-1 and an accuracy of ±1.2% and 5.0 s-1. As expected, in the healthy population, epicardial fat had a significantly lower fat fraction than subcutaneous fat (PDFF EAT = 81.6 ± 9.6% vs. PDFF ScAT = 92.7 ± 4.2%, P < 0.001) and paracardiac fat (PDFF PAT = 90.6 ± 3.7%). Preliminary results in type-2 diabetic patients also showed a lower PDFF in EAT compared to neighbor paracardiac fat, which remains to be confirmed in a larger cohort. This study demonstrated precise and highly-resolved PDFF and R2* 3D maps to probe cardiac fat, in particular epicardial adipose tissue, thanks to free-running cardiac Dixon-MRI at 3 T. Due to the proximity of the lungs, the B0 inhomogeneities field map had large spatial variations, hampering unbiased R2* quantification. Nevertheless, 3D maps of PDFF in the heart allow characterization of the EAT, whose brown-beige fat composition was confirmed in controls and few type 2 diabetic patients.

Changes in ventilation distribution during general anesthesia measured with EIT in mechanically ventilated small children

BackgroundAtelectasis during general anesthesia is a risk for perioperative complications. EIT measurements were performed in mechanically ventilated healthy children during elective surgery to demonstrate the changes in ventilation distribution during general anesthesia. The ventilation distribution was quantified by calculating the Global Inhomogeneity index (GI).MethodsEIT measurements were performed in 23 children (9 weeks—10 years) without lung disease to detect changes in regional ventilation during elective surgery. Three previously defined time points were marked during the measurement: after intubation and start of pressure-controlled ventilation (PCV), change to pressure support ventilation (PSV), and after extubation (spontaneous breathing—SB). Ventilation distribution based on regions of interest (ROI) and changes in end-expiratory volume (∆EELV) were collected at these time points and compared. The Global Inhomogeneity index was calculated at the beginning of pressure-controlled ventilation (PCV).ResultsWith increasing spontaneous breathing, dorsal recruitment of atelectasis occurred. The dorsal ventilation fraction increased over the time of general anesthesia with increasing spontaneous breathing, whereas the ventral fraction decreased relatively (Difference ± 5.5 percentage points respectively; 95% CI; 3.5—7.4; p < 0.001). With the onset of spontaneous breathing, there was a significant reduction in end-expiratory volume (Difference: 105 ml; 95% CI, 75–135; p < 0.001). The GI of the lung-healthy ventilated children is 47% (SD ± 4%).ConclusionControlled ventilation of healthy children resulted in increased ventilation of the ventral and collapse of the dorsal lung areas. Restart of spontaneous breathing after cessation of surgery resulted in an increase in ventilation in the dorsal with decrease in the ventral lung areas. By calculating the GI, representing the ratio of more to less ventilated lung areas, revealed the presumed homogeneous distribution of ventilation.Trial registrationClinicalTrials.gov Registration ID: NCT04873999. First registration: 05/05/2021.

Performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask.

To investigate if a cloth facemask could affect physiological and perceptual responses to exercise at distinct exercise intensities in healthy young individuals. Nine participants (sex, female/male: 6/3; age: 13±1 years; VO2peak: 44.5±5.5 mL/kg/min) underwent a progressive square-wave test at four intensities: (1) 80% of ventilatory anaerobic threshold (VAT), (2) VAT, and (3) 40% between VAT and [Formula: see text] wearing a triple-layered cloth facemask or not. Participants then completed a final stage to exhaustion at a running speed equivalent to the maximum achieved during the cardio-respiratory exercise test (Peak). Physiological, metabolic, and perceptual measures were measured. Mask did not affect spirometry (forced vital capacity, peak expiratory flow, forced expiratory volume; all p≥0.27), respiratory (inspiratory capacity, end-expiratory volume [EELV] to functional vital capacity ratio, EELV, respiratory frequency [Rf], tidal volume [VT], Rf/VT, end-tidal carbo dioxide pressure, ventilatory equivalent to carbon dioxide ratio; all p≥0.196), hemodynamic (heart rate, systolic and diastolic blood pressure; all p>0.41), ratings of perceived exertion (p = 0.04) or metabolic measures (lactate; p = 0.78) at rest or at any exercise intensity. This study shows that performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask. ClinicalTrials.gov: NCT04887714.

Inspiratory and end-expiratory effects of lung recruitment in the prone position on dorsal lung aeration - new physiological insights in a secondary analysis of a randomised controlled study in post-cardiac surgery patients.

Cardiac surgery produces dorso-basal atelectasis and ventilation/perfusion mismatch, associated with infection and prolonged intensive care. A postoperative lung volume recruitment manoeuvre to decrease the degree of atelectasis is routine. In patients with severe respiratory failure, prone positioning and recruitment manoeuvres may increase survival, oxygenation, or both. We compared the effects of lung recruitment in prone vs supine positions on dorsal inspiratory and end-expiratory lung aeration. In a prospective RCT, 30 post-cardiac surgery patients were randomly allocated to recruitment manoeuvres in the prone (n=15) or supine position (n=15). The primary endpoints were late dorsal inspiratory volume (arbitrary units [a.u.]) and left/right dorsal end-expiratory lung volume change (a.u.), prone vs supine after extubation, measured using electrical impedance tomography. Secondary outcomes included left/right dorsal inspiratory volumes (a.u.) and left/right dorsal end-expiratory lung volume change (a.u.) after prone recruitment and extubation. The last part of dorsal end-inspiratory volume after extubation was higher after prone (49.1 a.u.; 95% confidence interval [CI], 37.4-60.6) vs supine recruitment (24.2 a.u.; 95% CI, 18.4-29.6; P=0.024). Improvement in left dorsal end-expiratory lung volume after extubation was higher after prone (382 a.u.; 95% CI, 261-502) vs supine recruitment (-71 a.u., 95% CI, -140 to -2; n=15; P<0.001). After prone recruitment, left vs right predominant end-expiratory dorsal lung volume change disappeared after extubation. However, both left and right end-expiratory volumes were higher in the prone group, after extubation. Recruitment in the prone position improves dorsal inspiratory and end-expiratory lung volumes after cardiac surgery. NCT03009331.

Different positive end expiratory pressure and tidal volume controls on lung protection and inflammatory factors during surgical anesthesia.

Mechanical ventilation can lead to the severe impairment of the metabolic pathway of alveolar surfactants, inactivating alveolar surfactants and significantly reducing lung-chest compliance. The cardiopulmonary function of elderly patients usually reduced to a certain extent, and there are lung complications after surgical anesthesia, just like lung barotrauma caused by mechanical ventilation, atelectasis and postoperative hypoxemia. To investigate the effects of different positive end expiratory pressures (PEEPs) and tidal volumes (VTs) on respiratory function, the degree of the inflammatory response and hemodynamic indexes in patients undergoing surgery under general anesthesia. A total of 120 patients undergoing surgery for gastric or colon cancer under general anesthesia in Xinghua People's Hospital from January 2017 to January 2021 were randomly divided into Group A and Group B, with 60 cases in each group. The ventilation mode in Group A was VT (6.0 mL/kg) + PEEP (5.0 cmH2O), while that in Group B was VT (6.0 mL/kg) + PEEP (8.0 cmH2O). Blood gas parameters, respiratory mechanical parameters, inflammatory response indicators, hemodynamic indicators and related complications were compared between the two groups. There were no significant differences in PaCO2, PaO2, oxygen or the examined indexes at T0 between group A and group B (P > 0.05). The measured PaO2 value of patients in group A at T3 was higher than that in group B, and the difference was significant (P < 0.05). There were no significant differences in peak airway pressure (Ppeak), mean airway pressure or dynamic pulmonary compliance (Cdyn) at T0 between group A and group B (P > 0.05). The measured Ppeak value of patients in group A at T1 was higher than that in group B, and the difference was significant (P < 0.05). The measured Cdyn value at T1 and T2 was greater than that in group B (P < 0.05). Before surgery, there were no significant differences in tumor necrosis factor-α (TNF-α), interleukin (IL)-6 or IL-10 between group A and group B (P > 0.05). After 4 h, the measured values of TNF-α and IL-6 in group A were lower than those in group B, and the differences were significant (P < 0.05). The IL-10 Level in group A was higher than that in group B (P < 0.05). At T0, there were no significant differences in cardiac output, cardiac index (CI), stroke volume index (SVI) or mean arterial pressure between group A and group B (P > 0.05). The measured values of CI and SVI at T2 in patients in group A were higher than those in group B, and the differences were significant (P < 0.05). For patients undergoing surgery for gastric or colon cancer under general anesthesia, the VT (6.0 mL/kg) + PEEP (5.0 cmH2O) regimen was more effective than the VT (6.0 mL/kg) + PEEP (8.0 cmH2O) regimen in protecting the lung function and ventilatory function of patients, and it had better effects on maintaining hemodynamic stability and reducing inflammatory reactions.

ABDOMINAL COMPRESSION IN END-STAGE FIBROTIC INTERSTITIAL LUNG DISEASE (ILD) IMPROVES RESPIRATORY COMPLIANCE

ABDOMINAL COMPRESSION IN END-STAGE FIBROTIC INTERSTITIAL LUNG DISEASE (ILD) IMPROVES RESPIRATORY COMPLIANCE

Dynamic positive end-expiratory pressure strategies using time and pressure recruitment at birth reduce early expression of lung injury in preterm lambs.

Positive end-expiratory pressure (PEEP) is critical to the preterm lung at birth, but the optimal PEEP level remains uncertain. The objective of this study was to determine the effect of maximum PEEP levels at birth on the physiological and injury response in preterm lambs. Steroid-exposed preterm lambs (124-127 days gestation; n = 65) were randomly assigned from birth to either 1) positive pressure ventilation (PPV) at 8 cmH2O PEEP or 3-min dynamic stepwise PEEP strategy (DynPEEP), with either 2) 20 cmH2O maximum PEEP (10 PEEP second steps) or 3) 14 cmH2O maximum PEEP (20-s steps), all followed by standardized PPV for 90 min. Lung mechanics, gas exchange, regional ventilation and aeration (electrical impedance tomography), and histological and molecular measures of lung injury were compared between groups. Dynamic compliance was greatest using a maximum 20 cmH2O (DynPEEP). There were no differences in gas exchange, end-expiratory volume, and ventilator requirements. Regional ventilation became more uniform with time following all PEEP strategies. For all groups, gene expression of markers of early lung injury was greater in the gravity nondependent lung, and inversely related to the magnitude of PEEP, being lowest in the 20 cmH2O DynPEEP group overall. PEEP levels had no impact on lung injury in the dependent lung. Transient high maximum PEEP levels using dynamic PEEP strategies may confer more lung protection at birth.

Asynchronous changes of normal lung lobes during respiration based on quantitative computed tomography (CT).

This study aimed to explore the coordinated and independent actions of lung lobes during respiration using quantitative computed tomography (CT) in order to increase our in vivo understanding of pulmonary anatomy. Cases for whom test results showed normal pulmonary function tests (PFTs) results, and normal paired inspiratory-expiratory chest CT findings, as assessed by 2 radiologists, were retrospectively included in this study. From the chest CT results, we measured quantitative indices of lung volume (LV) and mean lung density (MLD) for the total lung (TL), left lung (LL), right lung (RL), and 5 lobes in inspiratory and expiratory phases. The differences of these measures between bilateral lungs and among the lobes were evaluated to study whether they were consistent or different during respiration. A total of 70 cases were included {median age of 49.5 [interquartile range (IQR), 38.0 to 60.3] years; 32 males; 38 females}. Overall, the inspiratory and expiratory volumes of the LL were smaller than those of the RL (both P<0.001). For the ventilation workload (λ, which indicates the ratio of lobar volume to total LV), the end-expiratory volume ratio (λex ) of the LL was 0.44 (IQR, 0.43 to 0.46), while the end-inspiratory volume ratio (λin ) had risen to 0.46 (IQR, 0.45 to 0.47) (P<0.001). Comparing the 5 lobes, not all lobes shared the same LV. However, the left lower lobe (LLL) and right lower lobe (RLL) showed some similarities. The λin-LLL and λin-RLL was higher than λex-LLL and λex-RLL , respectively (both P<0.001), while the ratios of the other lobes reduced. The pairwise mean absolute difference (PMAD) on λin and λex of the bilateral lower lobes was low in inspiration (0.0288) and expiration (0.0346). The MLD of bilateral lower lobes showed consistency in inspiration or in expiration (inspiration: P>0.999; expiration: P=0.975). In addition, the PMADs between the right middle lobe (RML) and other lobes were significantly larger than the PMAD between other pairs of lobes in both inspiration and expiration. Beyond that, the expiratory MLD of RML [-789.6 (IQR, -814 to -762.05) HU] was the lowest among the 5 lobes. We found that the LL assumes a higher workload during ventilation than it does during respiration. The 5 normal lobes were non-synchronous during respiration and contributed differently to ventilation. The bilateral lower lobes showed similarities and had a high-ventilation function, while and the LV and MLD of the RML showed the least changes within a respiration cycle.

The association between regional transcriptome profiles and lung volumes in response to mechanical ventilation and lung injury

BackgroundLung inhomogeneity plays a pivotal role in the development of ventilator-induced lung injury (VILI), particularly in the context of pre-existing lung injury. The mechanisms that underlie this interaction are poorly understood. We aimed to elucidate the regional transcriptomic response to mechanical ventilation (MV), with or without pre-existing lung injury, and link this to the regional lung volume response to MV.MethodsAdult female BALB/c mice were randomly assigned into one of four groups: Saline, MV, lipopolysaccharide (LPS) or LPS/MV. Lung volumes (tidal volume, Vt; end-expiratory volume, EEV) were measured at baseline or after 2 h of ventilation using four-dimensional computed tomography (4DCT). Regional lung tissue samples corresponding to specific imaging regions were analysed for the transcriptome response by RNA-Seq. Bioinformatics analyses were conducted and the regional expression of dysregulated gene clusters was then correlated with the lung volume response.ResultsMV in the absence of pre-existing lung injury was associated with regional variations in tidal stretch. The addition of LPS also caused regional increases in EEV. We identified 345, 141 and 184 region-specific differentially expressed genes in response to MV, LPS and LPS/MV, respectively. Amongst these candidate genes, up-regulation of genes related to immune responses were positively correlated with increased regional tidal stretch in the MV group, while dysregulation of genes associated with endothelial barrier related pathways were associated with increased regional EEV and Vt when MV was combined with LPS. Further protein–protein interaction analysis led to the identification of two protein clusters representing the PI3K/Akt and MEK/ERK signalling hubs which may explain the interaction between MV and LPS exposure.ConclusionThe biological pathways associated with lung volume inhomogeneity during MV, and MV in the presence of pre-existing inflammation, differed. MV related tidal stretch induced up-regulation of immune response genes, while LPS combined with MV disrupted PI3K/Akt and MEK/ERK signalling.

Free-breathing half-radial dual-echo balanced steady-state free precession thoracic imaging with wobbling Archimedean spiral pole trajectories

PurposeTo demonstrate free-breathing thoracic MRI with a minimal-TR balanced steady-state free precession (bSSFP) technique using wobbling Archimedean spiral pole (WASP) trajectories. MethodsPhantom and free-breathing in vivo chest imaging in healthy volunteers was performed at 1.5T with a half-radial, dual-echo, bSSFP sequence, termed bSTAR. For maximum sampling efficiency, a single analog-to-digital converter window along the full bipolar readout was used. To ensure a homogeneous coverage of the k-space over multiple breathing cycles, radial k-space sampling followed short-duration Archimedean spiral interleaves that were randomly titled by a small polar angle and rotated by a golden angle about the polar axis; depticting a wobbling Archimedean spiral pole (WASP) trajectory. In phantom and in vivo experiments, WASP trajectories were compared to spiral phyllotaxis sampling in terms of eddy currents and were used to generate in vivo thorax images at different respiratory phases. ResultsWASP trajectories provided artifact-free bSTAR imaging in both phantom and in vivo and respiratory self-gated reconstruction was successfully performed in all subjects. The amount of the acquired data allowed the reconstruction of 10 volumes at different respiratory levels with isotropic resolution of 1.77mm from a scan of 5.5minutes (using a TR of 1.32ms), and one high-resolution 1.16mm end-expiratory volume from a scan of 4.7minutes (using a TR of 1.42ms). The very short TR of bSTAR mitigated off-resonance artifacts despite the large field-of-view. ConclusionWe have demonstrated the feasibility of high-resolution free-breathing thoracic imaging with bSTAR using the wobbling Archimedean spiral pole in healthy subjects at 1.5T.

Dynamic lung behavior under high G acceleration monitored with electrical impedance tomography

Objective. During launch and atmospheric re-entry in suborbital space flights, astronauts are exposed to high G-acceleration. These acceleration levels influence gas exchange inside the lung and can potentially lead to hypoxaemia. The distribution of air inside the lung can be monitored by electrical impedance tomography. This imaging technique might reveal how high gravitational forces affect the dynamic behavior of ventilation and impair gas exchange resulting in hypoxaemia. Approach. We performed a trial in a long-arm centrifuge with ten participants lying supine while being exposed to +2, +4 and +6 G x (chest-to-back acceleration) to study the magnitude of accelerations experienced during suborbital spaceflight. Main results. First, the tomographic images revealed that the dorsal region of the lung emptied faster than the ventral region. Second, the ventilated area shifted from dorsal to ventral. Consequently, alveolar pressure in the dorsal area reached the pressure of the upper airways before the ventral area emptied completely. Finally, the upper airways collapsed and the end-expiratory volume increased. This resulted in ventral gas trapping with restricted gas exchange. Significance. At +4 G x , changes in ventilation distribution varied considerably between subjects, potentially due to variation in individual physical conditions. However, at +6 G x all participants were affected similarly and the influence of high gravitational conditions was pronounced.

Coil embolisation for massive haemoptysis in cystic fibrosis

IntroductionMassive haemoptysis is a life-threatening event in advanced cystic fibrosis (CF) lung disease with bronchial artery embolisation (BAE) as standard of care treatment. The aim of our study was to...

Vitamin D Status and Clinical Outcomes in Acute Respiratory Distress Syndrome: A Secondary Analysis From the Assessment of Low Tidal Volume and Elevated End-Expiratory Volume to Obviate Lung Injury (ALVEOLI) Trial.

Acute respiratory distress syndrome (ARDS) is a highly morbid condition that has limited therapeutic options. Optimal vitamin D status has been linked to immunological effects that may benefit critically ill patients. Therefore, we investigated whether admission 25-hydroxyvitamin D levels (25OHD) are associated with clinical outcomes in ARDS patients. We performed a secondary analysis of data from a randomized, controlled trial comparing oxygenation strategies in 549 patients with ARDS (NCT00000579). Baseline 25OHD was measured in stored plasma samples. We investigated the relationship between vitamin D status and ventilator-free days (VFD) as well as 90-day survival, using linear regression and Cox proportional hazard models, respectively. Analyses were adjusted for age, race, and Acute Physiology and Chronic Health Evaluation III score. Baseline 25OHD was measured in 476 patients. 90% of these individuals had 25OHD <20 ng/ml and 40% had 25OHD <10 ng/ml. Patients with 25OHD <20 ng/ml were likely to be ventilated for 3 days longer than patients with levels ≥20 ng/ml (ß 3.41; 95%CI 0.42-6.39: P = 0.02). Patients with 25OHD <10 ng/ml were likely to be ventilated for 9 days longer (ß 9.27; 95%CI 7.24-11.02: P < 0.001) and to have a 34% higher risk of 90-day mortality (HR 1.34; 95% CI 1.06-1.71: P = 0.02) compared to patients with levels >10 ng/ml. In patients with ARDS, vitamin D status is associated with duration of mechanical ventilation and 90-day mortality. Randomized, controlled trials are warranted to determine whether vitamin D supplementation improves clinical outcomes in ARDS patients.