Dorsal Lung Research Articles

Orthostatic Ex-Vivo Lung Perfusion (EVLP): A Proof of Concept.

The key goal in lung donation remains the improvement of graft preservation with the ultimate objective of increasing the number and quality of lung transplants (LTx). Therefore, in recent years the field of graft preservation focused on improving outcomes related to solid organ regeneration and restoration. In this contest Ex-Vivo Lung Perfusion (EVLP) plays a crucial role with the purpose to increase the donor pool availability transforming marginal and/or declined donor lungs suitable for transplantation. Aim of this proof of concept is to test the safety, suitability and feasibility of a new tilting dome for EVLP designed considering the dorsal lung areas as the "Achilles' heel" of the EVLP due to a more fluid accumulation than in the supine standard position.

Breath-by-breath assessment of acute pulmonary edema using electrical impedance tomography, spirometry and volumetric capnography in a sheep (Ovis Aries) model.

The bedside diagnosis of acute pulmonary edema is challenging. This study evaluated the breath-by-breath information from electrical impedance tomography (EIT), respiratory mechanics and volumetric capnography (VCap) to assess acute pulmonary edema induced by xylazine administration in anesthetized sheep. To determine the ability and efficiency of each monitoring modality in detecting changes in lung function associated with onset of pulmonary edema. Twenty healthy ewes were anesthetized, positioned in sternal (prone) recumbency and instrumented. Synchronized recordings of EIT, spirometry and VCap were performed for 60 s prior to start of injection, during xylazine injection over 60 s (0-60 s) and continuously for 1 min (60-120 s) after the end of injection. After visual assessment of the recorded mean variables, statistical analysis was performed using a mixed effect model for repeated measures with Bonferroni's correction for multiple comparisons, to determine at which breath after start of injection the variable was significantly different from baseline. A significant change over time was defined as an adjusted p < 0.05. All statistics were performed using GraphPad Prism 0.1.0. Electrical impedance tomography showed significant changes from baseline in all but two variables. These changes were observed simultaneously during xylazine injection at 48 s and were consistent with development of edema in dependent lung (decreased end-expiratory lung impedance, ventilation in centro-ventral and ventral lung region) and shift of ventilation into non-dependent lung (decreased non-dependent silent spaces and increased center of ventilation ventral to dorsal and increased ventilation in centro-dorsal and dorsal lung region). All changes in lung mechanics also occurred during injection, including decreased dynamic respiratory system compliance and increased peak expiratory flow, peak inspiratory pressure and airway resistance at 48, 54 and 60 s, respectively. Changes in VCap variables were delayed with all occurring after completion of the injection. In this model of pulmonary edema, EIT detected significant and rapid change in all assessed variables of lung function with changes in regional ventilation indicative of pulmonary edema. Volumetric capnography complemented the EIT findings, while respiratory mechanics were not specific to lung edema. Thus, EIT offers the most comprehensive method for pulmonary edema evaluation, including the assessment of ventilation distribution, thereby enhancing diagnostic capabilities.

Effect of prone positioning ventilation on pulmonary function in neonates during venous-arterial extracorporeal membrane oxygenation.

The use of extracorporeal membrane oxygenation (ECMO) technology has significantly decreased mortality rates associated with neonatal pulmonary hypertension and respiratory failure. Prone positioning ventilation (PPV) is a commonly used technique in critically ill infants, designed to improve thoracic pressure gradients, re-expand dorsal lung segments, and increase oxygenation in approximately 70-80% of patients suffering from acute respiratory distress syndrome. This study aimed to evaluate the effects of PPV on pulmonary function in neonates undergoing venous-arterial extracorporeal membrane oxygenation (VA-ECMO). We conducted a retrospective analysis of clinical data from 17 neonates who received ECMO support in our institution, divided into two groups based on ventilation strategy: ECMO with PPV (ECMO-PPV, n=8) and ECMO with supine positioning ventilation (ECMO-SPV, n=9). Parameters such as the P/F ratio [arterial oxygen partial pressure (PaO2)/fraction of inspired oxygen (FiO2)], oxygenation index (OI), respiratory system compliance (Crs), and airway resistance (RAW) were collected and analyzed at baseline, and at 1, 2, and 3 days post-ECMO initiation. In the ECMO-PPV group, these parameters were also assessed 3 days pre-treatment and 2 hours post-treatment initiation. Initial comparisons between ECMO-PPV and ECMO-SPV groups showed no significant difference in PaO2/FiO2, OI, Crs, or RAW. Throughout the ECMO treatment, both groups demonstrated gradual improvements in PaO2/FiO2 and Crs, and reductions in OI and RAW. Notably, by day 3, the ECMO-PPV group exhibited significant improvements in Crs and RAW compared to the ECMO-SPV group (P<0.05). Specifically, in the ECMO-PPV group, Crs significantly increased and RAW decreased after 2 hours of initiating PPV, with these changes becoming statistically significant by day 3 (Crs P=0.03, RAW P=0.03). No severe PPV-related complications were noted. PPV during neonatal ECMO may improve respiratory compliance and reduce RAW, potentially aiding lung recovery. Our findings suggest PPV as a viable strategy for neonates under ECMO support.

Monitoring lung recruitment.

This review explores lung recruitment monitoring, covering techniques, challenges, and future perspectives. Various methodologies, including respiratory system mechanics evaluation, arterial bold gases (ABGs) analysis, lung imaging, and esophageal pressure (Pes) measurement are employed to assess lung recruitment. In support to ABGs analysis, the assessment of respiratory mechanics with hysteresis and recruitment-to-inflation ratio has the potential to evaluate lung recruitment and enhance mechanical ventilation setting. Lung imaging tools, such as computed tomography scanning, lung ultrasound, and electrical impedance tomography (EIT) confirm their utility in following lung recruitment with the advantage of radiation-free and repeatable application at the bedside for sonography and EIT. Pes enables the assessment of dorsal lung tendency to collapse through end-expiratory transpulmonary pressure. Despite their value, these methodologies may require an elevated expertise in their application and data interpretation. However, the information obtained by these methods may be conveyed to build machine learning and artificial intelligence algorithms aimed at improving the clinical decision-making process. Monitoring lung recruitment is a crucial component of managing patients with severe lung conditions, within the framework of a personalized ventilatory strategy. Although challenges persist, emerging technologies offer promise for a personalized approach to care in the future.

Lung Ultrasound Evaluation of Aeration Changes in Response to Prone Positioning in Acute Respiratory Distress Syndrome (ARDS) Patients Requiring Venovenous Extracorporeal Membrane Oxygenation: An Observational Study.

Prone positioning (PP) has been proven to be a beneficial approach in enhancing survival outcomes for patients with severe acute respiratory distress syndrome (ARDS) who need venovenous extracorporeal membrane oxygenation (V-V ECMO) support. The study utilized bedside lung ultrasound (LUS) to evaluate changes in lung aeration caused by PP in ARDS patients receiving V-V ECMO. This retrospective single-center study involved adult ARDS patients requiring V-V ECMO. The assessment of LUS involved examining specific dorsal lung regions, encompassing 16 areas, during three pre-defined time points: baseline (10 minutes prior), three-hour PP positioning, and 10-minute post-supine repositioning, all within the initial three days. Based on the oxygenation response to PP, patients were categorized into responder and non-responder groups. The primary outcome was LUS score changes during the initial three-day period. Secondary outcomes examined the impact of PP on the partial pressure of oxygen (PaO2)/fraction of inspired oxygen (FiO2) (P/F) ratio, V-V ECMO weaning success, length of ICU stay, and hospital survival. Among the enrolled patients (27 in total), 16 were responders and 11 were non-responders. In the responder group, the global LUS score underwent a significant reduction from 26.38 ± 4.965 at baseline to 20.75 ± 3.337 (p < 0.001) after the first PP session, which further decreased to 15.94 ± 2.816 (p< 0.001) after three days. However, no significant differences were observed among PP non-responders. The oxygenation reaction yielded comparable results. There was a significant correlation between the duration of daily PP and the reduction in global LUS score among PP responders (r = -0.855, p < 0.001). In cases where the global LUS score decreased by > 7.5 after three days of PP, the area under the receiver operating characteristic curve (AUROC) for predicting ECMO weaning success was 0.815, while it was 0.761 for predicting hospital survival. LUS has the potential to predict the response to PP and evaluate the prognosis of ARDS patients with V-V ECMO, althoughmore studies are demanded in the future.

High vs Low PEEP in Patients With ARDS Exhibiting Intense Inspiratory Effort During Assisted Ventilation: A Randomized Crossover Trial

BackgroundPEEP can potentially modulate inspiratory effort (ΔPes), which is the major determinant of self-inflicted lung injury. Research questionDoes high PEEP reduce ΔPes in moderate-to-severe ARDS patients on assisted ventilation? Study Design and MethodsSixteen patients with PaO2/FiO2≤200 mmHg and ΔPes≥10 cmH2O underwent a randomized sequence of four ventilator settings: PEEP=5 cmH2O or PEEP=15 cmH2O + synchronous (pressure support ventilation, PSV) or asynchronous (pressure-controlled intermittent mandatory ventilation, PC-IMV) inspiratory assistance. ΔPes, respiratory system, lung and chest-wall mechanics were assessed with esophageal manometry and occlusions. PEEP-induced alveolar recruitment and overinflation, lung dynamic strain and tidal volume distribution were assessed with electrical impedance tomography. ResultsΔPes was not systematically different at high vs. low PEEP (PSV: median 20 [15-24] cmH2O vs. 15 [13-23], p=0.24; PC-IMV: 20 [18-23] vs. 19 [17-25], p=0.67). Similarly, respiratory system and transpulmonary driving pressure, tidal volume, lung/chest-wall mechanics and pendelluft extent were not different between study phases. High PEEP resulted in lower or higher ΔPes, respiratory system and transpulmonary driving pressure according to whether this increased or decreased respiratory system compliance, respectively (r=-0.85, p<0.001; r=-0.75, p<0.001; r=-0.80, p<0.001, respectively). PEEP-induced changes in respiratory system compliance were driven by its lung component and were dependent on the extent of PEEP-induced alveolar overinflation (r=-0.66, p=0.006). High PEEP caused variable recruitment and systematic redistribution of tidal volume towards dorsal lung regions, thereby reducing dynamic strain in ventral areas (PSV: 0.49 [0.37-0.83] vs. 0.96 [0.62-1.56], p=0.003; PC-IMV: 0.65 [0.42-1.31] vs. 1.14 [0.79-1.52], p=0.002). All results were consistent during synchronous and asynchronous inspiratory assistance. InterpretationThe impact of high PEEP on ΔPes and lung stress is inter-individually variable according to different effects on respiratory system and lung compliance resulting from alveolar overinflation. High PEEP may help mitigate the risk of self-inflicted lung injury solely if it increases lung/respiratory system compliance.

Postmortem temporal chest CT and its pathological correlation in piglets.

Post-mortem computed tomography (PMCT) is a useful tool to investigate the cause of death. To appropriately use PMCT for cause-of-death analysis, it is necessary to know natural courses after death such as hypostasis in the lungs. We aimed to investigate the natural time-course change of postmortem chest CT findings and its pathological correlation in piglets. Serial chest PMCT scans of four piglets were performed each hour for 24 h and the chronological changes of the lung were evaluated. Immediately after the final CT scan, the autopsy was conducted and bilateral lungs were taken for pathological examination. Two additional piglets were sacrificed and pathological specimens were prepared immediately after death for reference. On pulmonary PMCT, ground glass attenuation (GGA) appeared after the first several hours and increased gradually. Histologically, GGA corresponded to pulmonary edema. The time-related increase in CT attenuation was more prominent in the dorsal lung. Consolidation, endotracheal air defects, and pleural effusion were not observed on PMCT. GGA appeared after the first several hours and increased gradually, and it corresponded to pulmonary edema. GGA in the lung as one of the natural postmortem processes needs to be distinguished from pathogenic findings depending on the time elapsed since death. J. Med. Invest. 71 : 232-236, August, 2024.

Pronation Reveals a Heterogeneous Response of Global and Regional Respiratory Mechanics in Patients With Acute Hypoxemic Respiratory Failure.

Experimental models suggest that prone position and positive end-expiratory pressure (PEEP) homogenize ventral-dorsal ventilation distribution and regional respiratory compliance. However, this response still needs confirmation on humans. Therefore, this study aimed to assess the changes in global and regional respiratory mechanics in supine and prone positions over a range of PEEP levels in acute respiratory distress syndrome (ARDS) patients. A prospective cohort study. Twenty-two intubated patients with ARDS caused by COVID-19 pneumonia. Electrical impedance tomography and esophageal manometry were applied during PEEP titrations from 20 cm H2O to 6 cm H2O in supine and prone positions. Global respiratory system compliance (Crs), chest wall compliance, regional lung compliance, ventilation distribution in supine and prone positions. Compared with supine position, the maximum level of Crs changed after prone position in 59% of ARDS patients (n = 13), of which the Crs decreased in 32% (n = 7) and increased in 27% (n = 6). To reach maximum Crs after pronation, PEEP was changed in 45% of the patients by at least 4 cm H2O. After pronation, the ventilation and compliance of the dorsal region did not consistently change in the entire sample of patients, increasing specifically in a subgroup of patients who showed a positive change in Crs when transitioning from supine to prone position. These combined changes in ventilation and compliance suggest dorsal recruitment postpronation. In addition, the subgroup with increased Crs postpronation demonstrated the most pronounced difference between dorsal and ventral ventilation distribution from supine to prone position (p = 0.01), indicating heterogeneous ventilation distribution in prone position. Prone position modifies global respiratory compliance in most patients with ARDS. Only a subgroup of patients with a positive change in Crs postpronation presented a consistent improvement in dorsal ventilation and compliance. These data suggest that the response to pronation on global and regional mechanics can vary among ARDS patients, with some patients presenting more dorsal lung recruitment than others.

Effects of changes in trunk inclination on ventilatory efficiency in ARDS patients: quasi-experimental study

BackgroundTrunk inclination from semirecumbent head-upright to supine-flat positioning reduces driving pressure and increases respiratory system compliance in patients with acute respiratory distress syndrome (ARDS). These effects are associated with an improved ventilatory ratio and reduction in the partial pressure of carbon dioxide (PaCO2). However, these physiological effects have not been completely studied, and their mechanisms have not yet been elucidated. Therefore, this study aimed to evaluate the effects of a change in trunk inclination from semirecumbent (45°) to supine-flat (10°) on physiological dead space and ventilation distribution in different lung regions.ResultsTwenty-two ARDS patients on pressure-controlled ventilation underwent three 60-min steps in which trunk inclination was changed from 45° (baseline) to 10° (intervention) and back to 45° (control) in the last step. Tunk inclination from a semirecumbent (45°) to a supine-flat (10°) position resulted in a higher tidal volume [371 (± 76) vs. 433 (± 84) mL (P < 0.001)] and respiratory system compliance [34 (± 10) to 41 (± 12) mL/cmH2O (P < 0.001)]. The CO2 exhaled per minute improved from 191 mL/min (± 34) to 227 mL/min (± 38) (P < 0.001). Accordingly, Bohr’s dead space ratio decreased from 0.49 (± 0.07) to 0.41 (± 0.06) (p < 0.001), and PaCO2 decreased from 43 (± 5) to 36 (± 4) mmHg (p < 0.001). In addition, the impedance ratio, which divides the ventilation activity of the ventral region by the dorsal region ventilation activity in tidal images, dropped from 1.27 (0.83–1.78) to 0.86 (0.51–1.33) (p < 0.001). These results, calculated from functional EIT images, indicated further ventilation activity in the dorsal lung regions. These effects rapidly reversed once the patient was repositioned at 45°.ConclusionsA change in trunk inclination from a semirecumbent (45 degrees) to a supine-flat position (10 degrees) improved Bohr’s dead space ratio and reduced PaCO2 in patients with ARDS. This effect is associated with an increase in tidal volume and respiratory system compliance, along with further favourable impedance ventilation distribution toward the dorsal lung regions. This study highlights the importance of considering trunk inclination as a modifiable determinant of physiological parameters. The angle of trunk inclination is essential information that must be reported in ARDS patients.

Endotracheal tube, by the venturi effect, reduces the efficacy of increasing inlet pressure in improving pendelluft.

In mechanically ventilated severe acute respiratory distress syndrome patients, spontaneous inspiratory effort generates more negative pressure in the dorsal lung than in the ventral lung. The airflow caused by this pressure difference is called pendelluft, which is a possible mechanisms of patient self-inflicted lung injury. This study aimed to use computer simulation to understand how the endotracheal tube and insufficient ventilatory support contribute to pendelluft. We established two models. In the invasive model, an endotracheal tube was connected to the tracheobronchial tree with 34 outlets grouped into six locations: the right and left upper, lower, and middle lobes. In the non-invasive model, the upper airway, including the glottis, was connected to the tracheobronchial tree. To recreate the inspiratory effort of acute respiratory distress syndrome patients, the lower lobe pressure was set at -13 cmH2O, while the upper and middle lobe pressure was set at -6.4 cmH2O. The inlet pressure was set from 10 to 30 cmH2O to recreate ventilatory support. Using the finite volume method, the total flow rates through each model and toward each lobe were calculated. The invasive model had half the total flow rate of the non-invasive model (1.92 L/s versus 3.73 L/s under 10 cmH2O, respectively). More pendelluft (gas flow into the model from the outlets) was observed in the invasive model than in the non-invasive model. The inlet pressure increase from 10 to 30 cmH2O decreased pendelluft by 11% and 29% in the invasive and non-invasive models, respectively. In the invasive model, a faster jet flowed from the tip of the endotracheal tube toward the lower lobes, consequently entraining gas from the upper and middle lobes. Increasing ventilatory support intensifies the jet from the endotracheal tube, causing a venturi effect at the bifurcation in the tracheobronchial tree. Clinically acceptable ventilatory support cannot completely prevent pendelluft.

Physiological effects of awake prone position in acute hypoxemic respiratory failure

BackgroundThe effects of awake prone position on the breathing pattern of hypoxemic patients need to be better understood. We conducted a crossover trial to assess the physiological effects of awake prone position in patients with acute hypoxemic respiratory failure.MethodsFifteen patients with acute hypoxemic respiratory failure and PaO2/FiO2 < 200 mmHg underwent high-flow nasal oxygen for 1 h in supine position and 2 h in prone position, followed by a final 1-h supine phase. At the end of each study phase, the following parameters were measured: arterial blood gases, inspiratory effort (ΔPES), transpulmonary driving pressure (ΔPL), respiratory rate and esophageal pressure simplified pressure–time product per minute (sPTPES) by esophageal manometry, tidal volume (VT), end-expiratory lung impedance (EELI), lung compliance, airway resistance, time constant, dynamic strain (VT/EELI) and pendelluft extent through electrical impedance tomography.ResultsCompared to supine position, prone position increased PaO2/FiO2 (median [Interquartile range] 104 mmHg [76–129] vs. 74 [69–93], p < 0.001), reduced respiratory rate (24 breaths/min [22–26] vs. 27 [26–30], p = 0.05) and increased ΔPES (12 cmH2O [11–13] vs. 9 [8–12], p = 0.04) with similar sPTPES (131 [75–154] cmH2O s min−1 vs. 105 [81–129], p > 0.99) and ΔPL (9 [7–11] cmH2O vs. 8 [5–9], p = 0.17). Airway resistance and time constant were higher in prone vs. supine position (9 cmH2O s arbitrary units−3 [4–11] vs. 6 [4–9], p = 0.05; 0.53 s [0.32–61] vs. 0.40 [0.37–0.44], p = 0.03). Prone position increased EELI (3887 arbitrary units [3414–8547] vs. 1456 [959–2420], p = 0.002) and promoted VT distribution towards dorsal lung regions without affecting VT size and lung compliance: this generated lower dynamic strain (0.21 [0.16–0.24] vs. 0.38 [0.30–0.49], p = 0.004). The magnitude of pendelluft phenomenon was not different between study phases (55% [7–57] of VT in prone vs. 31% [14–55] in supine position, p > 0.99).ConclusionsProne position improves oxygenation, increases EELI and promotes VT distribution towards dependent lung regions without affecting VT size, ΔPL, lung compliance and pendelluft magnitude. Prone position reduces respiratory rate and increases ΔPES because of positional increases in airway resistance and prolonged expiratory time. Because high ΔPES is the main mechanistic determinant of self-inflicted lung injury, caution may be needed in using awake prone position in patients exhibiting intense ΔPES.Clinical trail registeration: The study was registered on clinicaltrials.gov (NCT03095300) on March 29, 2017.

Computed Tomographic and Histopathologic Studies of Lung Function Immediately Post Natum in Canine Neonates.

The lung tissue in newborn canine neonates is still in a morphologically and functionally immature, canalicular-saccular stage. True alveoli are only formed postnatally. The aim of this study was to analyze the spatial and temporal development of the ventilation of the lung tissue in vital canine neonates during the first 24 h post natum (p.n.). Forty pups (birth weight Ø 424 g ± 80.1 g) from three litters of large dog breeds (>20 kg live weight) were included in the studies. Thirty-three pups (29 vital, 2 vitally depressed, 2 stillborn neonates) originated from controlled, uncomplicated births (n = 3); moreover, six stillborn pups as well as one prematurely deceased pup were birthed by other dams with delivery complications. Computed tomography (CT) was used in 39 neonates, and histopathologic tissue classification techniques (HALO) were used in 11 neonates (eight stillborn and three neonates died early post natum, respectively) to quantify the degree of aerated neonatal lung tissue. It was shown that, in vital born pups, within the first 10 min p.n., the degree of ventilation reached mean values of -530 (±114) Hounsfield units (HU) in the dorsal and -453.3 (±133) HU in the ventral lung area. This is about 75-80% of the final values obtained after 24 h p.n. for dorsal -648.0 (±89.9) HU and ventral quadrants -624.7 (±76.8) HU. The dorsal lung areas were always significantly better ventilated than the ventral regions (p = 0.0013). CT as well as histopathology are suitable to clearly distinguish the nonventilated lungs of stillborns from neonates that were initially alive after surviving neonatal respiratory distress syndrome but who died prematurely (p = 0.0398). The results of this study are clinically relevant since the lung tissue of canine neonates presents an aeration profile as early as 10 min after birth and continues progressively, with a special regard to the dorsal lung areas. This is the basis for resuscitation measures that should be performed, preferably with the pup in the abdomen-chest position.

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.

Real-time effects of lateral positioning on regional ventilation and perfusion in an experimental model of acute respiratory distress syndrome.

Low-volume lung injury encompasses local concentration of stresses in the vicinity of collapsed regions in heterogeneously ventilated lungs. We aimed to study the effects on ventilation and perfusion distributions of a sequential lateral positioning (30°) strategy using electrical impedance tomography imaging in a porcine experimental model of early acute respiratory distress syndrome (ARDS). We hypothesized that such strategy, including a real-time individualization of positive end-expiratory pressure (PEEP) whenever in lateral positioning, would provide attenuation of collapse in the dependent lung regions. A two-hit injury acute respiratory distress syndrome experimental model was established by lung lavages followed by injurious mechanical ventilation. Then, all animals were studied in five body positions in a sequential order, 15min each: Supine 1; Lateral Left; Supine 2; Lateral Right; Supine 3. The following functional images were analyzed by electrical impedance tomography: ventilation distributions and regional lung volumes, and perfusion distributions. The induction of the acute respiratory distress syndrome model resulted in a marked fall in oxygenation along with low regional ventilation and compliance of the dorsal half of the lung (gravitational-dependent in supine position). Both the regional ventilation and compliance of the dorsal half of the lung greatly increased along of the sequential lateral positioning strategy, and maximally at its end. In addition, a corresponding improvement of oxygenation occurred. In conclusion, our sequential lateral positioning strategy, with sufficient positive end-expiratory pressure to prevent collapse of the dependent lung units during lateral positioning, provided a relevant diminution of collapse in the dorsal lung in a porcine experimental model of early acute respiratory distress syndrome.

Lateral Dorsal Basal Lung Resection Based on Functional Preserving Sublobectomy Method: Single-Center Experience.

Functional preserving sublobectomy (FPSL), a novel balancing strategy for segmentectomy and wedge resection, allows rapid and accurate removal of invisible nodules without the use of any preoperative localization markers. This study aimed to share single-center experience of lateral dorsal basal lung resection based on FPSL, so as to provide new surgical options for thoracic surgeons. A retrospective analysis was performed on 13 patients who underwent thoracoscopic basal lung resection after FPSL at XX hospital from January 2021 to August 2022. The operation was successfully performed in 13 patients by using FPSL, including 12 patients with malignant tumors. The mean operating time was 107.5 ± 25.6 min. The mean postoperative hospital stay was 3.7 ± 2.4 days. None of the patients needed extended excision, such as an entire basal or inferior lobectomy. Our single-center experience showed that the FPSL method only dealt with the target vessels, which greatly reduced the technical difficulty of surgery. In addition, both arteries and veins could be used as target vessels, and in particular cases such as undeveloped interlobar fissure, the operation could still be completed successfully. Lateral dorsal basal lung resection based on FPSL may be a new surgical option for surgeons.

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.

Quantitative lung ultrasound detects dynamic changes in lung recruitment in the preterm lamb

BackgroundLung ultrasound (LUS) may not detect small, dynamic changes in lung volume. Mean greyscale measurement using computer-assisted image analysis (Q-LUSMGV) may improve the precision of these measurements.MethodsPreterm lambs (n = 40) underwent LUS of the dependent or non-dependent lung during static pressure–volume curve mapping. Total and regional lung volumes were determined using the super-syringe technique and electrical impedance tomography. Q-LUSMGV and gold standard measurements of lung volume were compared in 520 images.ResultsDependent Q-LUSMGV moderately correlated with total lung volume (rho = 0.60, 95% CI 0.51–0.67) and fairly with right whole (rho = 0.39, 0.27–0.49), central (rho = 0.38, 0.27–0.48), ventral (rho = 0.41, 0.31–0.51) and dorsal regional lung volumes (rho = 0.32, 0.21–0.43). Non-dependent Q-LUSMGV moderately correlated with total lung volume (rho = 0.57, 0.48–0.65) and fairly with right whole (rho = 0.43, 0.32–0.52), central (rho = 0.46, 0.35–0.55), ventral (rho = 0.36, 0.25–0.47) and dorsal lung volumes (rho = 0.36, 0.25–0.47). All correlation coefficients were statistically significant. Distinct inflation and deflation limbs, and sonographic pulmonary hysteresis occurred in 95% of lambs. The greatest changes in Q-LUSMGV occurred at the opening and closing pressures.ConclusionQ-LUSMGV detected changes in total and regional lung volume and offers objective quantification of LUS images, and may improve bedside discrimination of real-time changes in lung volume.ImpactLung ultrasound (LUS) offers continuous, radiation-free imaging that may play a role in assessing lung recruitment but may not detect small changes in lung volume.Mean greyscale image analysis using computer-assisted quantitative LUS (Q-LUSMGV) moderately correlated with changes in total and regional lung volume.Q-LUSMGV identified opening and closing pressure and pulmonary hysteresis in 95% of lambs.Computer-assisted image analysis may enhance LUS estimation of lung recruitment at the bedside.Future research should focus on improving precision prior to clinical translation.

Prone Positioning Decreases Inhomogeneity and Improves Dorsal Compliance in Invasively Ventilated Spontaneously Breathing COVID-19 Patients-A Study Using Electrical Impedance Tomography.

Background: We studied prone positioning effects on lung aeration in spontaneously breathing invasively ventilated patients with coronavirus disease 2019 (COVID-19). Methods: changes in lung aeration were studied prospectively by electrical impedance tomography (EIT) from before to after placing the patient prone, and back to supine. Mixed effect models with a random intercept and only fixed effects were used to evaluate changes in lung aeration. Results: fifteen spontaneously breathing invasively ventilated patients were enrolled, and remained prone for a median of 19 [17 to 21] hours. At 16 h the global inhomogeneity index was lower. At 2 h, there were neither changes in dorsal nor in ventral compliance; after 16 h, only dorsal compliance (βFe +18.9 [95% Confidence interval (CI): 9.1 to 28.8]) and dorsal end-expiratory lung impedance (EELI) were increased (βFe, +252 [95% CI: 13 to 496]); at 2 and 16 h, dorsal silent spaces was unchanged (βFe, –4.6 [95% CI: –12.3 to +3.2]). The observed changes induced by prone positioning disappeared after turning patients back to supine. Conclusions: in this cohort of spontaneously breathing invasively ventilated COVID-19 patients, prone positioning decreased inhomogeneity, increased lung volumes, and improved dorsal compliance.

Prevalence of lung atelectasis in sedated dogs examined with computed tomography

BackgroundComputed tomography (CT) scanning of the lung is known to be a valuable tool when investigating lung pathology of the dog. During CT-scan the dog needs to be immobilized and general anesthesia has historically been considered as gold standard although being a more expensive and time-consuming alternative to sedation. Today, modern high speed multidetector CT-scanners offer new possibilities for sedation as an alternative. Both anesthesia and sedation can cause lung atelectasis, and this can be problematic when reading the CT-images since it potentially can masque or mimic lung pathology leading to misdiagnosis. The objective of this prospective analytic study was to investigate the prevalence of lung atelectasis and changes in lung attenuation over time in dogs that receive intravenous sedation and positioned in sternal recumbency.Results20 dogs without known lung pathology underwent three consecutive CT-scans of the lung; the first scan was initiated as soon as the dog was sufficiently sedated, the second scan approximately 5 min after the first one and the last scan after the dog’s orthopaedic scan was completed. The dogs received intravenous sedation in a combination of dexmedetomidine and butorphanol and were kept positioned in a strict sternal recumbency during sedation and exam. Each lung lobe was individually examined in an axial plane and measurements of dorsal, ventral, and mean lung attenuation were made. Atelectasis or areas with poorly aerated lung tissue were not detected as all parts of the lobes were normally aerated at all three scans. A statistically significant increase in lung attenuation between the first and the second scan (P = 0.03) and between the first and the third scan (P = 0.0004) was seen in the ventral part of the lobes.ConclusionsThis study indicates that CT-examination of the lungs can be performed on sedated dogs that are kept in a sternal recumbency without development of atelectasis. It also suggests that there is an early correlation between time and increase in lung attenuation.

Effect of body position on the redistribution of regional lung aeration during invasive and non-invasive ventilation of COVID-19 patients

Severe COVID-19-related acute respiratory distress syndrome (C-ARDS) requires mechanical ventilation. While this intervention is often performed in the prone position to improve oxygenation, the underlying mechanisms responsible for the improvement in respiratory function during invasive ventilation and awake prone positioning in C-ARDS have not yet been elucidated. In this prospective observational trial, we evaluated the respiratory function of C-ARDS patients while in the supine and prone positions during invasive (n = 13) or non-invasive ventilation (n = 15). The primary endpoint was the positional change in lung regional aeration, assessed with electrical impedance tomography. Secondary endpoints included parameters of ventilation and oxygenation, volumetric capnography, respiratory system mechanics and intrapulmonary shunt fraction. In comparison to the supine position, the prone position significantly increased ventilation distribution in dorsal lung zones for patients under invasive ventilation (53.3 ± 18.3% vs. 43.8 ± 12.3%, percentage of dorsal lung aeration ± standard deviation in prone and supine positions, respectively; p = 0.014); whereas, regional aeration in both positions did not change during non-invasive ventilation (36.4 ± 11.4% vs. 33.7 ± 10.1%; p = 0.43). Prone positioning significantly improved the oxygenation both during invasive and non-invasive ventilation. For invasively ventilated patients reduced intrapulmonary shunt fraction, ventilation dead space and respiratory resistance were observed in the prone position. Oxygenation is improved during non-invasive and invasive ventilation with prone positioning in patients with C-ARDS. Different mechanisms may underly this benefit during these two ventilation modalities, driven by improved distribution of lung regional aeration, intrapulmonary shunt fraction and ventilation-perfusion matching. However, the differences in the severity of C-ARDS may have biased the sensitivity of electrical impedance tomography when comparing positional changes between the protocol groups.Trial registration: ClinicalTrials.gov (NCT04359407) and Registered 24 April 2020, https://clinicaltrials.gov/ct2/show/NCT04359407.