Dorsal Lung Research Articles

Lung ultrasound response to awake prone positioning predicts the need for intubation in patients with COVID-19 induced acute hypoxemic respiratory failure: an observational study

BackgroundAwake prone positioning (APP) reduces the intubation rate in COVID-19 patients treated by high-flow nasal cannula (HFNC). However, the lung aeration response to APP has not been addressed. We aimed to explore the lung aeration response to APP by lung ultrasound (LUS).MethodsThis two-center, prospective, observational study enrolled patients with COVID-19-induced acute hypoxemic respiratory failure treated by HFNC and APP. LUS score was recorded 5–10 min before, 1 h after APP, and 5–10 min after supine in the first APP session within the first three days. The primary outcome was LUS score changes in the first three days. Secondary outcomes included changes in SpO2/FiO2 ratio, respiratory rate and ROX index (SpO2/FiO2/respiratory rate) related to APP, and the rate of treatment success (patients who avoided intubation).ResultsSeventy-one patients were enrolled. LUS score decreased from 20 (interquartile range [IQR] 19–24) to 19 (18–21) (p < 0.001) after the first APP session, and to 19 (18–21) (p < 0.001) after three days. Compared to patients with treatment failure (n = 20, 28%), LUS score reduction after the first three days in patients with treatment success (n = 51) was greater (− 2.6 [95% confidence intervals − 3.1 to − 2.0] vs 0 [− 1.2 to 1.2], p = 0.001). A decrease in dorsal LUS score > 1 after the first APP session was associated with decreased risk for intubation (Relative risk 0.25 [0.09–0.69]). APP daily duration was correlated with LUS score reduction in patients with treatment success, especially in dorsal lung zones (r = − 0.76; p < 0.001).ConclusionsIn patients with acute hypoxemic respiratory failure due to COVID-19 and treated by HFNC, APP reduced LUS score. The reduction in dorsal LUS scores after APP was associated with treatment success. The longer duration on APP was correlated with greater lung aeration.Trial registration This study was prospectively registered on clinicaltrials.gov on April 22, 2021. Identification number NCT04855162.

Lung ultrasound of the dependent lung detects real-time changes in lung volume in the preterm lamb

BackgroundEffective lung protective ventilation requires reliable, real-time estimation of lung volume at the bedside. Neonatal clinicians lack a readily available imaging tool for this purpose.ObjectiveTo determine the ability of lung...

Pronation in acute respiratory distress syndrome (ARDS) secondary to COVID-19

: In March 2020, the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was declared a pandemic by the World Health Organization. Patients with SARS-CoV-2 infection can develop coronavirus disease 2019 (COVID-19), the most concerning complication of which is acute hypoxaemic respiratory failure requiring mechanical ventilation and intensive care unit (ICU) admission. In this context prone position ventilation is an established method to improve oxygenation in severe acute respiratory distress syndrome (ARDS), and its application was able to reduce mortality rate. Prone position has been used since the 1970s to treat severe hypoxemia in patients with ARDS because of its effectiveness at improving gas exchange. Compared with the supine position, placing patients in prone position effects a more even tidal volume distribution, in part, by reversing the vertical pleural pressure gradient, which becomes more negative in the dorsal regions. Prone position also improves resting lung volume in the dorsocaudal regions by reducing the superimposed pressure of both the heart and the abdomen. In contrast, pulmonary perfusion remains preferentially distributed to the dorsal lung regions, thus improving overall alveolar ventilation/perfusion relationships. Moreover, the larger tissue mass suspended from a wider dorsal chest wall effects a more homogeneous distribution of pleural pressures throughout the lung that reduces abnormal strain and stress development. This is believed to ameliorate the severity or development of ventilator-induced lung injury and may partly explain why prone position reduces mortality in severe ARDS. In this review we investigate the physiological aspects of the pronation.

Prone positioning improves ventilation–perfusion matching assessed by electrical impedance tomography in patients with ARDS: a prospective physiological study

BackgroundThe physiological effects of prone ventilation in ARDS patients have been discussed for a long time but have not been fully elucidated. Electrical impedance tomography (EIT) has emerged as a tool for bedside monitoring of pulmonary ventilation and perfusion, allowing the opportunity to obtain data. This study aimed to investigate the effect of prone positioning (PP) on ventilation–perfusion matching by contrast-enhanced EIT in patients with ARDS.DesignMonocenter prospective physiologic study.SettingUniversity medical ICU.PatientsTen mechanically ventilated ARDS patients who underwent PP.InterventionsWe performed EIT evaluation at the initiation of PP, 3 h after PP initiation and the end of PP during the first PP session.Measurements and main resultsThe regional distribution of ventilation and perfusion was analyzed based on EIT images and compared to the clinical variables regarding respiratory and hemodynamic status. Prolonged prone ventilation improved oxygenation in the ARDS patients. Based on EIT measurements, the distribution of ventilation was homogenized and dorsal lung ventilation was significantly improved by PP administration, while the effect of PP on lung perfusion was relatively mild, with increased dorsal lung perfusion observed. The ventilation–perfusion matched region was found to increase and correlate with the increased PaO2/FiO2 by PP, which was attributed mainly to reduced shunt in the lung.ConclusionsProlonged prone ventilation increased dorsal ventilation and perfusion, which resulted in improved ventilation–perfusion matching and oxygenation.Trial registration: ClinicalTrials.gov, NCT04725227. Registered on 25 January 2021.

Pleural pressure during sleep in Marfan syndrome: details about the CPAP effect.

Pleural pressure during sleep in Marfan syndrome: details about the CPAP effect.

Dynamic Relative Regional Lung Strain Estimated by Electrical Impedance Tomography in an Experimental Model of ARDS.

To analyze the role of PEEP on dynamic relative regional strain (DRRS) in a model of ARDS, respective maps were generated by electrical impedance tomography (EIT). Eight ARDS pigs submitted to PEEP steps of 0, 5, 10, and 15 cm H2O at fixed ventilation were evaluated by EIT images. DRRS was calculated as (VT-EIT/EELI)/(VT-EIT[15PEEP]/EELI[15PEEP]), where the tidal volume (VT)-EIT and end-expiratory lung impedance (EELI) are the tidal and end-expiratory change in lung impedance, respectively. The measurement at 15 PEEP was taken as reference (end-expiratory transpulmonary pressure > 0 cm H2O). The relationship between EIT variables (center of ventilation, EELI, and DRRS) and airway pressures was assessed with mixed-effects models using EIT measurements as dependent variables and PEEP as fixed-effect variable. At constant ventilation, respiratory compliance increased progressively with PEEP (lowest value at zero PEEP 10 ± 3 mL/cm H2O and highest value at 15 PEEP 16 ± 6 mL/cm H2O; P < .001), whereas driving pressure decreased with PEEP (highest value at zero PEEP 34 ± 6 cm H2O and lowest value at 15 PEEP 21 ± 4 cm H2O; P < .001). The mixed-effect regression models showed that the center of ventilation moved to dorsal lung areas with a slope of 1.81 (1.44-2.18) % points by each cm H2O of PEEP; P < .001. EELI increased with a slope of 0.05 (0.02-0.07) (arbitrary units) for each cm H2O of PEEP; P < .001. DRRS maps showed that local strain in ventral lung areas decreased with a slope of -0.02 (-0.24 to 0.15) with each cm H2O increase of PEEP; P < .001. EIT-derived DRRS maps showed high strain in ventral lung zones at low levels of PEEP. The findings suggest overdistention of the baby lung.

Lung perfusion during veno-venous extracorporeal membrane oxygenation in a model of hypoxemic respiratory failure

BackgroundVeno-venous extracorporeal membrane oxygenation (ECMO) provides blood oxygenation and carbon dioxide removal in acute respiratory distress syndrome. However, during ECMO support, the native lungs still play an important role in gas exchange, functioning as a second oxygenator in series with ECMO. The hypoxic vasoconstriction mechanism diverts regional blood flow within the lungs away from regions with low oxygen levels, optimizing ventilation/perfusion matching. ECMO support has the potential to reduce this adaptive pulmonary response and worsen the ventilation/perfusion mismatch by raising venous oxygen partial pressure. Thus, the objective of this study was to evaluate the effect of ECMO on regional pulmonary perfusion and pulmonary hemodynamics during unilateral ventilation and posterior lung collapse.MethodsFive Agroceres pigs were instrumented, monitored and submitted to ECMO. We used the Electrical Impedance Tomography (EIT) to evaluate lung ventilation and perfusion in all protocol steps. Effects of ECMO support on pulmonary hemodynamics and perfusion involving two different scenarios of ventilation/perfusion mismatch: (1) right-lung selective intubation inducing collapse of the normal left lung and (2) dorsal lung collapse after repeated lung lavage. Data including hemodynamics, respiratory, lung perfusion/ventilation, and laboratory data over time were analyzed with a mixed generalized model using the subjects as a random factor.ResultsThe initiation of ECMO support provided a significant reduction in Mean Pulmonary Artery Pressure (PAPm) in both situations of ventilation/perfusion mismatch. However, distribution of lung perfusion did not change with the use of ECMO support.ConclusionsWe found that the use of ECMO support with consequent increase in venous oxygen pressure induced a significant drop in PAPm with no detectable effect on regional lung perfusion in different scenarios of ventilation/perfusion mismatch.

Prone Position Minimizes the Exacerbation of Effort-dependent Lung Injury: Exploring the Mechanism in Pigs and Evaluating Injury in Rabbits

Vigorous spontaneous effort can potentially worsen lung injury. This study hypothesized that the prone position would diminish a maldistribution of lung stress and inflation after diaphragmatic contraction and reduce spontaneous effort, resulting in less lung injury. A severe acute respiratory distress syndrome model was established by depleting surfactant and injurious mechanical ventilation in 6 male pigs ("mechanism" protocol) and 12 male rabbits ("lung injury" protocol). In the mechanism protocol, regional inspiratory negative pleural pressure swing (intrabronchial balloon manometry) and the corresponding lung inflation (electrical impedance tomography) were measured with a combination of position (supine or prone) and positive end-expiratory pressure (high or low) matching the intensity of spontaneous effort. In the lung injury protocol, the intensities of spontaneous effort (esophageal manometry) and regional lung injury were compared in the supine position versus prone position. The mechanism protocol (pigs) found that in the prone position, there was no ventral-to-dorsal gradient in negative pleural pressure swing after diaphragmatic contraction, irrespective of the positive end-expiratory pressure level (-10.3 ± 3.3 cm H2O vs. -11.7 ± 2.4 cm H2O at low positive end-expiratory pressure, P = 0.115; -10.4 ± 3.4 cm H2O vs. -10.8 ± 2.3 cm H2O at high positive end-expiratory pressure, P = 0.715), achieving homogeneous inflation. In the supine position, however, spontaneous effort during low positive end-expiratory pressure had the largest ventral-to-dorsal gradient in negative pleural pressure swing (-9.8 ± 2.9 cm H2O vs. -18.1 ± 4.0 cm H2O, P < 0.001), causing dorsal overdistension. Higher positive end-expiratory pressure in the supine position reduced a ventral-to-dorsal gradient in negative pleural pressure swing, but it remained (-9.9 ± 2.8 cm H2O vs. -13.3 ± 2.3 cm H2O, P < 0.001). The lung injury protocol (rabbits) found that in the prone position, spontaneous effort was milder and lung injury was less without regional difference (lung myeloperoxidase activity in ventral vs. dorsal lung, 74.0 ± 30.9 μm · min-1 · mg-1 protein vs. 61.0 ± 23.0 μm · min-1 · mg-1 protein, P = 0.951). In the supine position, stronger spontaneous effort increased dorsal lung injury (lung myeloperoxidase activity in ventral vs. dorsal lung, 67.5 ± 38.1 μm · min-1 · mg-1 protein vs. 167.7 ± 65.5 μm · min-1 · mg-1 protein, P = 0.003). Prone position, independent of positive end-expiratory pressure levels, diminishes a maldistribution of lung stress and inflation imposed by spontaneous effort and mitigates spontaneous effort, resulting in less effort-dependent lung injury.

Sequential lateral positioning as a new lung recruitment maneuver: an exploratory study in early mechanically ventilated Covid-19 ARDS patients

BackgroundA sequential change in body position from supine-to-both lateral positions under constant ventilatory settings could be used as a postural recruitment maneuver in case of acute respiratory distress syndrome (ARDS), provided that sufficient positive end-expiratory pressure (PEEP) prevents derecruitment. This study aims to evaluate the feasibility and physiological effects of a sequential postural recruitment maneuver in early mechanically ventilated COVID-19 ARDS patients.MethodsA cohort of 15 patients receiving lung-protective mechanical ventilation in volume-controlled with PEEP based on recruitability were prospectively enrolled and evaluated in five sequentially applied positions for 30 min each: Supine-baseline; Lateral-1st side; 2nd Supine; Lateral-2nd side; Supine-final. PEEP level was selected using the recruitment-to-inflation ratio (R/I ratio) based on which patients received PEEP 12 cmH2O for R/I ratio ≤ 0.5 or PEEP 15 cmH2O for R/I ratio > 0.5. At the end of each period, we measured respiratory mechanics, arterial blood gases, lung ultrasound aeration, end-expiratory lung impedance (EELI), and regional distribution of ventilation and perfusion using electric impedance tomography (EIT).ResultsComparing supine baseline and final, respiratory compliance (29 ± 9 vs 32 ± 8 mL/cmH2O; p < 0.01) and PaO2/FIO2 ratio (138 ± 36 vs 164 ± 46 mmHg; p < 0.01) increased, while driving pressure (13 ± 2 vs 11 ± 2 cmH2O; p < 0.01) and lung ultrasound consolidation score decreased [5 (4–5) vs 2 (1–4); p < 0.01]. EELI decreased ventrally (218 ± 205 mL; p < 0.01) and increased dorsally (192 ± 475 mL; p = 0.02), while regional compliance increased in both ventral (11.5 ± 0.7 vs 12.9 ± 0.8 mL/cmH2O; p < 0.01) and dorsal regions (17.1 ± 1.8 vs 18.8 ± 1.8 mL/cmH2O; p < 0.01). Dorsal distribution of perfusion increased (64.8 ± 7.3% vs 66.3 ± 7.2%; p = 0.01).ConclusionsWithout increasing airway pressure, a sequential postural recruitment maneuver improves global and regional respiratory mechanics and gas exchange along with a redistribution of EELI from ventral to dorsal lung areas and less consolidation.Trial registration ClinicalTrials.gov, NCT04475068. Registered 17 July 2020, https://clinicaltrials.gov/ct2/show/NCT04475068

Prolonged Continuous Monitoring of Regional Lung Function in Infants with Respiratory Failure.

Rationale: Electrical impedance tomography (EIT) allows instantaneous and continuous visualization of regional ventilation and changes in end-expiratory lung volume at the bedside. There is particular interest in using EIT for monitoring in critically ill neonates and young children with respiratory failure. Previous studies have focused only on short-term monitoring in small populations. The feasibility and safety of prolonged monitoring with EIT in neonates and young children have not been demonstrated yet. Objectives: To evaluate the feasibility and safety of long-term EIT monitoring in a routine clinical setting and to describe changes in ventilation distribution and homogeneity over time and with positioning in a multicenter cohort of neonates and young children with respiratory failure. Methods: At four European University hospitals, we conducted an observational study (NCT02962505) on 200 patients with postmenstrual ages (PMA) between 25 weeks and 36 months, at risk for or suffering from respiratory failure. Continuous EIT data were obtained using a novel textile 32-electrode interface and recorded at 48 images/s for up to 72 hours. Clinicians were blinded to EIT images during the recording. EIT parameters and the effects of body position on ventilation distribution were analyzed offline. Results: The average duration of EIT measurements was 53 ± 20 hours. Skin contact impedance was sufficient to allow image reconstruction for valid ventilation analysis during a median of 92% (interquartile range, 77-98%) of examination time. EIT examinations were well tolerated, with minor skin irritations (temporary redness or imprint) occurring in 10% of patients and no moderate or severe adverse events. Higher ventilation amplitude was found in the dorsal and right lung areas when compared with the ventral and left regions, respectively. Prone positioning resulted in an increase in the ventilation-related EIT signal in the dorsal hemithorax, indicating increased ventilation of the dorsal lung areas. Lateral positioning led to a redistribution of ventilation toward the dependent lung in preterm infants and to the nondependent lung in patients with PMA > 37 weeks. Conclusions: EIT allows continuous long-term monitoring of regional lung function in neonates and young children for up to 72 hours with minimal adverse effects. Our study confirmed the presence of posture-dependent changes in ventilation distribution and their dependency on PMA in a large patient cohort. Clinical trial registered with www.clinicaltrials.gov (NCT02962505).

Effects of Awake Prone Positioning in Non-intubated Spontaneously Breathing COVID-19 Patients Requiring High Flow Oxygen Therapy in High Dependency Unit (HDU): An Observational Study.

Prone positioning increases oxygenation by recruiting dorsal lung regions and draining airway secretions and improves gas exchange and survival in ARDS. We describe the efficacy of prone positioning in awake non-intubated spontaneously breathing COVID-19 positive patients with hypoxemic acute respiratory failure. We studied 26 awake non-intubated spontaneously breathing patients with hypoxemic respiratory failure treated with prone positioning. Patients were kept in prone position for two hours in each session and four such sessions were given to patients in 24 hours. SPO2, PaO, 2RR and haemodynamics were measured before prone positioning (PRE), 60 minutes of prone positioning (PRONE), and one hour after the completion of each session (POST). 26 patients (12 males and 14 females) non-intubated spontaneously breathing with SPO2 <94% on 0.4 FiO2 were treated with prone positioning. One patient required intubation and was shifted to ICU, the rest (25 patients) were discharged from HDU. Mean hours of prone positioning were 19.4 ± 2.06 hr. There was significant improvement in oxygenation (increase in PaO2 from 53.15 ± 6.0 mmHg to 64.23 ± 6.96 mmHg in PRE and POST sessions respectively, likewise there was increase in SPO2). No complications were noted with various sessions. Prone positioning was feasible and improved oxygenation in awake non-intubated, spontaneously breathing COVID-19 patients with hypoxemic acute respiratory failure.

Lung Ultrasound versus Pulmonary Auscultation in Detecting Pulmonary Congestion in the Critically Ill

BACKGROUND: In critically ill patients, auscultation might be challenging as dorsal lung fields are difficult to reach in supine-positioned patients, and the environment is often noisy. In recent years, clinicians have started to consider lung ultrasound (LUS) as a useful diagnostic tool for a variety of pulmonary pathologies, including pulmonary edema. AIM: The aim of this study was to compare LUS versus pulmonary auscultation for detecting pulmonary edema in critically ill patients. PATIENTS AND METHODS: Sixty-one patients were included in this study, all included patients underwent clinical examination, chest auscultation of anterior and lateral (axillary) chest wall and back in each hemithorax in supine position was done, followed by LUS using Bedside LUS in Emergency (BLUE) protocol. LUS score was recorded; abnormal auscultation was defined as the presence of rales or wheezes. Laboratory tests were done on admission such as pro-BNP, renal function, and blood gases. Pro-BNP was used as diagnostic tool for volume overload and was correlated with LUS and stethoscope for detecting pulmonary edema. Pneumonia was excluded with normal total leukocyte counts, C-reactive protein, and absence of fever. RESULTS: This study included 61 patients with diagnosis of pulmonary edema, all data were recorded on admission and showed that there was statistically significant good positive correlation between LUS and Pro-BNP (p &lt; 0.05), and Pearson correlation between LUS and Pro-BNP among the studied patients is statistically significant at the 0.01 level (two-tailed). Furthermore, we found that both LUS and Pro-BNP were statistically significant higher among patients with rales (p &lt; 0.05) only 36 (59%) patients were positive as pulmonary edema with pulmonary auscultation (presence of rales) and 25 (41%) patients were negative for pulmonary edema (NO RALES) while they were positive for pulmonary edema with LUS (high LUS score)and pro-BNP. CONCLUSION: Pulmonary auscultation has poor sensitivity for pulmonary congestion while LUS had statistically significant higher sensitivity for pulmonary edema.

Assessment of Postnatal Pulmonary Adaption in Bovine Neonates Using Electric Impedance Tomography (EIT).

Simple SummaryThe lungs of the neonate must oxygenate the blood and eliminate carbon dioxide at birth. Efficient gas exchange requires ventilation of the pulmonary alveoli to meet rapidly increasing oxygen demands. It is not entirely clear how quickly the different regions of the lungs become ventilated and when ventilation of all lung regions is achieved. We used electric impedance tomography (EIT) to measure lung stretch and aeration in 20 non-sedated neonatal calves born without difficulty. For EIT measurement, an electrode belt was placed around the thorax of each calf positioned in sternal recumbency immediately after birth and at various other times until 3 weeks of age to measure aeration and ventilation in different regions of the lungs. Standard EIT variables describing distribution of ventilation, respiratory rate, and several blood gas variables were determined. Most lung regions were ventilated immediately after birth. Ventilation of the ventral regions increased during the first hour, after which it decreased. Dorsal lung regions and the right lung had the greatest ventilation. The respiratory rate decreased, and the tidal impedance change as a surrogate for tidal volume increased in the first 3 weeks of life. The study showed that most regions of the lungs are ventilated immediately after birth. However, this is followed by a reduction in ventilation of ventral regions of the lungs, presumably because of gravity-driven ventral movement of residual amniotic fluid. These findings may allow identification of calves with insufficient lung expansion and ventilation after birth.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.

The Effect of Physical Therapy on Regional Lung Function in Critically Ill Patients.

Early mobilization has become an important aspect of treatment in intensive care medicine, especially in patients with acute pulmonary dysfunction. As its effects on regional lung physiology have not been fully explored, we conceived a prospective observational study (Registration number: DRKS00023076) investigating regional lung function during a 15-min session of early mobilization physiotherapy with a 30-min follow-up period. The study was conducted on 20 spontaneously breathing adult patients with impaired pulmonary gas exchange receiving routine physical therapy during their intensive care unit stay. Electrical impedance tomography (EIT) was applied to continuously monitor ventilation distribution and changes in lung aeration during mobilization and physical therapy. Baseline data was recorded in the supine position, the subjects were then transferred into the seated and partly standing position for physical therapy. Afterward, patients were transferred back into the initial position and followed up with EIT for 30 min. EIT data were analyzed to assess changes in dorsal fraction of ventilation (%dorsal), end-expiratory lung impedance normalized to tidal variation (ΔEELI), center of ventilation (CoV) and global inhomogeneity index (GI index).Follow-up was completed in 19 patients. During exercise, patients exhibited a significant change in ventilation distribution in favor of dorsal lung regions, which did not persist during follow-up. An identical effect was shown by CoV. ΔEELI increased significantly during follow-up. In conclusion, mobilization led to more dorsal ventilation distribution, but this effect subsided after returning to initial position. End-expiratory lung impedance increased during follow-up indicating a slow increase in end-expiratory lung volume following physical therapy.

Therapeutic benefits of proning to improve pulmonary gas exchange in severe respiratory failure: focus on fundamentals of physiology.

New Findings What is the topic of this review? The use of proning for improving pulmonary gas exchange in critically ill patients. What advances does it highlight? Proning places the lung in its ‘natural’ posture, and thus optimises the ventilation‐perfusion distribution, which enables lung protective ventilation and the alleviation of potentially life‐threatening hypoxaemia in COVID‐19 and other types of critical illness with respiratory failure. The survival benefit of proning patients with acute respiratory distress syndrome (ARDS) is well established and has recently been found to improve pulmonary gas exchange in patients with COVID‐19‐associated ARDS (CARDS). This review outlines the physiological implications of transitioning from supine to prone on alveolar ventilation‐perfusion (V˙A--Q˙) relationships during spontaneous breathing and during general anaesthesia in the healthy state, as well as during invasive mechanical ventilation in patients with ARDS and CARDS. Spontaneously breathing, awake healthy individuals maintain a small vertical (ventral‐to‐dorsal) V˙A/Q˙ ratio gradient in the supine position, which is largely neutralised in the prone position, mainly through redistribution of perfusion. In anaesthetised and mechanically ventilated healthy individuals, a vertical V˙A/Q˙ ratio gradient is present in both postures, but with better V˙A--Q˙ matching in the prone position. In ARDS and CARDS, the vertical V˙A/Q˙ ratio gradient in the supine position becomes larger, with intrapulmonary shunting in gravitationally dependent lung regions due to compression atelectasis of the dorsal lung. This is counteracted by proning, mainly through a more homogeneous distribution of ventilation combined with a largely unaffected high perfusion dorsally, and a consequent substantial improvement in arterial oxygenation. The data regarding proning as a therapy in patients with CARDS is still limited and whether the associated improvement in arterial oxygenation translates to a survival benefit remains unknown. Proning is nonetheless an attractive and lung protective manoeuvre with the potential benefit of improving life‐threatening hypoxaemia in patients with ARDS and CARDS.

Extubation generates lung volume inhomogeneity in preterm infants

ObjectiveTo evaluate the feasibility of electrical impedance tomography (EIT) to describe the regional tidal ventilation (VT) and change in end-expiratory lung volume (EELV) patterns in preterm infants during the process...

Regional lung viscoelastic properties in supine and prone position in a porcine model of acute respiratory distress syndrome.

Regional viscoelastic properties of thoracic tissues in acute respiratory distress syndrome (ARDS) and their change with position and positive end-expiratory pressure (PEEP) are unknown. In an experimental porcine ARDS, dorsal and ventral lung (R2,L and E2,L) and chest wall (R2,cw and E2,cw) viscoelastic resistive (R) and elastic (E) parameters were measured at 20, 15, 10, and 5 cmH2O PEEP in supine and prone position. E2 and R2 were obtained by fitting the decay of pressure after end-inspiratory occlusion to the equation: Pviscmax (t) =R2 e-t/τ2, where t is the length of occlusion and τ2 time constant. E2 was equal to R2/τ2. R2,cw and E2,cw were measured from esophageal, dorsal, and ventral pleural pressures. Global R2,L and E2,L were obtained from the global transpulmonary pressure (airway pressure-esophageal pressure), and regional R2,L and E2,L from the dorsal and ventral airway pressure-pleural pressure difference. Lung ventilation was measured by electrical impedance tomography (EIT). Global R2,cw and E2,cw did not change with PEEP or position. Global R2,L [median(Q1-Q3)] was 37.1 (11.0-65.1), 5.1 (4.3-5.5), 12.1 (8.4-19.5), and 41.0 (26.6-53.5) cmH2O/L/s in supine, and 15.3 (9.1-41.9), 7.9 (5.7-11.0), 8.0 (5.1-12.1), and 12.9 (6.4-19.4) cmH2O/L in prone from 20 to 5 cmH2O PEEP (P = 0.06 for PEEP and P = 0.06 for position). Dorsal R2,L significantly and positively correlated with the amount of collapse measured with EIT. Global and regional lung and chest wall viscoelastic parameters can be described by a simple rheological model. Regional E2 and R2 were uninfluenced by PEEP and position except for PEEP on dorsal E2,L and position on dorsal E2,cw.NEW & NOTEWORTHY In a porcine model of acute respiratory distress syndrome, data were successfully fitted to a rheological model of the nonlinear behavior of viscoelastic properties of lung and chest wall at different positive end-expiratory pressure (PEEP) in the supine and prone position. Prone position tended to decrease lung viscoelastic resistive component. PEEP had a significant effect on dorsal lung viscoelastic elastance. Finally, lung viscoelastic resistance correlated with the amount of lung collapse assessed by electrical impedance tomography.

Pleural Pressure Targeted Positive Airway Pressure Improves Cardiopulmonary Function in Spontaneously Breathing Patients With Obesity

Increased pleural pressure affects the mechanics of breathing of people with class III obesity (BMI > 40kg/m2). What are the acute effects of CPAP titrated to match pleural pressure on cardiopulmonary function in spontaneously breathing patients with class III obesity? We enrolled six participants with BMI within normal range (control participants, group I) and 12 patients with class III obesity (group II) divided into subgroups: IIa, BMI of 40 to 50kg/m2; and IIb, BMI of≥ 50kg/m2. The study was performed in two phases: in phase 1, participants were supine and breathing spontaneously at atmospheric pressure, and in phase 2, participants were supine and breathing with CPAP titrated to match their end-expiratory esophageal pressure in the absence of CPAP. Respiratory mechanics, esophageal pressure, and hemodynamic data were collected, and right heart function was evaluated by transthoracic echocardiography. The levels of CPAP titrated to match pleural pressure in group I, subgroup IIa, and subgroup IIb were 6 ± 2cmH2O, 12 ± 3cmH2O, and 18 ± 4cmH2O, respectively. In both subgroups IIa and IIb, CPAP titrated to match pleural pressure decreased minute ventilation (IIa, P= .03; IIb, P= .03), improved peripheral oxygen saturation (IIa, P= .04; IIb, P= .02), improved homogeneity of tidal volume distribution between ventral and dorsal lung regions (IIa, P= .22; IIb, P= .03), and decreased work of breathing (IIa, P< .001; IIb, P= .003) with a reduction in both the work spent to initiate inspiratory flow as well as tidal ventilation. In five hypertensive participants with obesity, BP decreased to normal range, without impairment of right heart function. In ambulatory patients with class III obesity, CPAP titrated to match pleural pressure decreased work of breathing and improved respiratory mechanics while maintaining hemodynamic stability, without impairing right heart function. ClinicalTrials.gov; No.: NCT02523352; URL: www.clinicaltrials.gov.

A survived case of penetrating neck injury with intrathoracic organ damage

BackgroundThoracic surgeons rarely encounter stab wounds with injury to the intrathoracic organs. However, such sudden and urgent situations could arise; therefore, experiences in managing such cases are invaluable.Case presentationAn 84-year-old woman with depression who had a stab injury in the neck caused by a broad-bladed kitchen knife was brought to our facility by ambulance. She was stable in the emergency room; however, a computed tomography scan revealed that the blade had penetrated the right thoracic cavity. A right hemopneumothorax was seen. Considering the possibility of injury to the major vessels, a median sternotomy was performed. During the dissection around the blade, the patient started bleeding profusely, which required repair of an injury to the right internal jugular vein. The blade tip had penetrated the dorsal right upper lung lobe; however, it did not reach the hilum, and the knife was carefully removed. The damaged area of the lung was removed by wedge resection.ConclusionPatients with deep stab wounds from knives are often hemodynamically stable because the blade acts as tamponade and prevents hemorrhage. Therefore, a surgical approach that allows for good visualization should be considered for the extraction of the blade.

Assessment of Electrical Impedance Tomography to Set Optimal Positive End-Expiratory Pressure for Venoarterial Extracorporeal Membrane Oxygenation-Treated Patients.

Patients on venoarterial extracorporeal membrane oxygenation have many risk factors for pulmonary complications in addition to their heart failure. Optimal positive end-expiratory pressure is unknown in these patients. The aim was to evaluate the ability of electrical impedance tomography to help the physician to select the optimal positive end-expiratory pressure in venoarterial extracorporeal membrane oxygenation treated and mechanically ventilated patients during a positive end-expiratory pressure trial. Observational prospective monocentric. University hospital. Patients (n = 23) older than 18 years old, on mechanical ventilation and venoarterial extracorporeal membrane oxygenation. A decreasing positive end-expiratory pressure trial (20-5 cm H2O) in increments of 5 cm H2O was performed and monitored by a collection of clinical parameters, ventilatory and ultrasonographic (cardiac and pulmonary) to define an optimal positive end-expiratory pressure according to respiratory criteria (optimal positive end-expiratory pressure selected by physician with respiratory parameters), and then adjusted according to hemodynamic and cardiac tolerances (optimal positive end-expiratory pressure selected by physician with respiratory, hemodynamic, and echocardiographic parameters). At the same time, electrical impedance tomography data (regional distribution of ventilation, compliance, and overdistension collapse) were recorded and analyzed retrospectively to define the optimal positive end-expiratory pressure. The median of this optimal positive end-expiratory pressure was 10 cm H2O in our population. Electrical impedance tomography showed that increasing positive end-expiratory pressure promoted overdistention of ventral lung, maximum at positive end-expiratory pressure 20 cm H20 (34% [interquartile range, 24.5-40]). Decreasing positive end-expiratory pressure resulted in collapse of dorsal lung (29% [interquartile range, 21-45.8]). The optimal positive end-expiratory pressure selected by physician with respiratory parameters was not different from the positive end-expiratory pressure chosen by the electrical impedance tomography. However, there is a negative impact of a high level of intrathoracic pressure on hemodynamic and cardiac tolerances. Our results support that electrical impedance tomography appears predictive to define optimal positive end-expiratory pressure on venoarterial extracorporeal membrane oxygenation, aided by echocardiography to optimize hemodynamic assessment and management.