Effect of perioperative sigh ventilation on postoperative hypoxemia and pulmonary complications after on-pump cardiac surgery (E-SIGHT): study protocol for a randomized controlled trial.

BACKGROUND: Postoperative hypoxemia and pulmonary complications remain a frequent event after on-pump cardiac surgery and mostly characterized by pulmonary atelectasis. Surfactant dysfunction or hyposecretion happens prior to atelectasis formation, and sigh represents the strongest stimulus for surfactant secretion. The role of sigh breaths added to conventional lung protective ventilation in reducing postoperative hypoxemia and pulmonary complications among cardiac surgery is unknown. METHODS: The perioperative sigh ventilation in cardiac surgery (E-SIGHT) trial is a single-center, two-arm, randomized controlled trial. In total, 192 patients scheduled for elective cardiac surgery with cardiopulmonary bypass (CPB) and aortic cross-clamp will be randomized into one of the two treatment arms. In the experimental group, besides conventional lung protective ventilation, sigh volumes producing plateau pressures of 35 cmH2O (or 40 cmH2O for patients with body mass index > 35 kg/m2) delivered once every 6 min from intubation to extubation. In the control group, conventional lung protective ventilation without preplanned recruitment maneuvers is used. Lung protective ventilation (LPV) consists of low tidal volumes (6-8 mL/kg of predicted body weight) and positive end-expiratory pressure (PEEP) setting according to low PEEP/FiO2 table for acute respiratory distress syndrome (ARDS). The primary endpoint is time-weighted average SpO2/FiO2 ratio during the initial post-extubation hour. Main secondary endpoint is the severity of postoperative pulmonary complications (PPCs) computed by postoperative day 7. DISCUSSION: The E-SIGHT trial will be the first randomized controlled trial to evaluate the impact of perioperative sigh ventilation on the postoperative outcomes after on-pump cardiac surgery. The trial will introduce and assess a novel perioperative ventilation approach to mitigate the risk of postoperative hypoxemia and PPCs in patients undergoing cardiac surgery. Also provide the basis for a future larger trial aiming at verifying the impact of sigh ventilation on postoperative pulmonary complications. TRIAL REGISTRATION: ClinicalTrials.gov NCT06248320. Registered on January 30, 2024. Last updated February 26, 2024.

Comparison of efficacy and safety of different suction pressure for speeding non-ventilated lung collapse in uniport video-assisted thoracoscopic surgery: a randomized-controlled trial.

BACKGROUND: The bronchial suction has been applied in speeding lung collapse. Low suction pressure may not speed lung collapse, but high pressure causes occult lung injury. The aim of the study was to explore efficacy and safety of different suction pressure for speeding lung collapse. METHODS: Eighty-four subjects undergoing uniport video-assisted thoracoscopic surgery (VATS) were randomly assigned for non-suction (Group 0), -10 cmH2O suction pressure (Group - 10), and - 30 cmH2O suction pressure (Group - 30). The primary outcome were the lung collapse scores (LCS) at 0 min (T0) after the visualization of the lung using a 10-point visual analogue scale and area under the curve (AUC) of LCS over time. The secondary outcomes included disconnection from the ventilator, the assessment of occult lung injury using NOS-3 expression, histologic scores of lung injury, and lung W/D weight ratio, intraoperative hypoxemia, the incidence of perioperative pulmonary complications. RESULTS: Both the LCS at T0 and AUC analysis showed that compared with Group 0, Group - 10 and Group - 30 significantly achieved good lung collapse (P < 0.05), but no difference between Group - 10 and Group - 30. Four patients in Group 0 were treated with disconnection maneuver. The assessment of occult lung injury showed no differences. CONCLUSIONS: Applying - 10 cmH2O suction pressure for 1 min when pleural incision is a relatively safe method to promote lung collapse without the occurrence of occult lung injury. TRIAL REGISTRATION: Chinese Clinical Trial Registry number, ChiCTR2200062991. Registered on 26/08/2022.

Cotton Ball Aspiration Leading to Pulmonary Complications in a Child.

BACKGROUND Foreign body aspiration (FBA) is a common and serious problem in childhood that requires early recognition and treatment. Common complications include asphyxia, hemorrhage, infection, and pneumothorax. In severe cases of foreign body obstruction, death can result from asphyxia. We report an interesting case in which a forgotten cotton ball was inhaled into the lungs. CASE REPORT A 5-year-old boy presented to the local hospital with coughing for 6 days and fever for 4 days, without any information of foreign body aspiration upon admission. Laboratory findings indicated an elevated white blood cell; therefore, cefprozil was given as anti-infective treatment. However, the child's condition did not improve. A computed tomography scan showed left pulmonary atelectasis. Considering that the child's condition was serious, he was referred to our hospital for diagnosis and treatment. After referral, auscultation revealed decreased breath sounds over the left lung. After multidisciplinary discussion, combined with the results of auxiliary examination, the possibility of a foreign body was considered. He underwent rigid bronchoscopy, which confirmed a yellow-white foreign body in the left main bronchus that was later verified as a cotton ball. The operation was very successful. Eventually, his condition improved and he was discharged, without additional complications. CONCLUSIONS For children with unclear history of foreign body aspiration, bronchoscopy is recommended if there is recurrent pulmonary infection, low auscultation breath sounds, or abnormal imaging. The choice of surgical method depends on the location and type of foreign body and the experience of the surgeon, which is also very important.

The effects of laryngeal mask versus endotracheal tube on atelectasis after general anesthesia induction assessed by lung ultrasound: A randomized controlled trial.

STUDY OBJECTIVE: This study aims to evaluate the impact of Supreme™ laryngeal masks versus endotracheal tubes on atelectasis during general anesthesia using lung ultrasound (LUS), and provide evidence for respiratory management. DESIGN: A single-center, double-blind, randomized controlled trial was conducted. SETTING: The study was conducted in both the operating room and the post-anesthesia care unit, with follow-up assessments performed in the ward. PATIENTS: Enrollment included 180 cases undergoing non-laparoscopic surgeries in gynecology, urology, and orthopedic limb surgeries. INTERVENTIONS: Patients were randomly assigned 1:1 to the endotracheal intubation or laryngeal mask group. MEASUREMENTS: LUS scores were recorded across 12 lung regions at baseline, 15 min after airway establishment, at the end of surgery, and 30 min following airway removal. Outcome measures encompassed the oxygenation index, dynamic lung compliance, incidence of postoperative pulmonary complications, throat pain, and other postoperative complications assessed at 24 and 48 h postoperatively. The primary outcome focused on the LUS score in all 12 lung regions at 15 min after airway establishment. MAIN RESULTS: Intention-to-treat analysis of 177 subjects revealed endotracheal intubation led to significantly higher LUS scores at 15 min {P < 0.001, mean difference 4.15 ± 0.60, 95% CI [2.97, 5.33]}, end of surgery (P < 0.001, mean difference 3.37 ± 0.68, 95% CI [2.02, 4.72]), and 30 min post-removal (P < 0.001, mean difference 2.63 ± 0.48, 95% CI [1.68, 3.58]). No major complications occurred in the two groups. CONCLUSIONS: Compared to endotracheal intubation, laryngeal masks effectively reduce atelectasis formation and progression in gynecological, urological non-laparoscopic, and orthopedic limb surgeries. However, caution is warranted when generalizing these findings to surgeries with a higher risk of laryngeal mask leakage or obese patients. Additionally, the efficacy of laryngeal masks in reducing postoperative atelectasis remains uncertain when comprehensive monitoring of muscle relaxation and reversal therapy is employed.

Efficacy and safety of simultaneous combined Zephyr and Spiration valve therapy in patients with advanced pulmonary emphysema.

BACKGROUND: Endoscopic lung volume reduction with valves is a minimally invasive treatment strategy for patients with severe pulmonary emphysema. Two valve systems are currently available: Zephyr and Spiration valves. As these can be implanted simultaneously in the same procedure, the question arose as to the effect on lung function, exercise capacity and subjective disease perception after combined valve treatment. METHODS: We conducted a retrospective analysis of 108 patients with combined, simultaneous treatment of Zephyr and Spiration valves. The decision on which and how many valves to implant was based on the individual patient anatomy. Effects on lung function, exercise capacity and atelectasis formation as well as complications were evaluated 90- and 180-days post-treatment (90d-FU and 180d-FU). RESULTS: At 90d-FU (n = 90), the mean change was 86.7 ± 183.7 mL for FEV1 and -645.3 ± 1276.5 mL for RV, with responder rates of 39.8 % and 46.5 %, respectively. Complete atelectasis occurred in 16.7 % and partial atelectasis in 25.5 % of patients. Six-minute walking distance increased by 27.00 m [-1.50 - 68.50m]. The rates of pneumothorax (10.2 %) 6 months after treatment were not higher than in randomized controlled trials (RCTs). Likely due to the inclusion of high-risk patients, there was a higher incidence of severe COPD exacerbation (21.3 %) and pneumonia (12.0 %) compared to RCTs. CONCLUSIONS: The combined implantation of Zephyr and Spiration valves resulted in significant clinical and functional improvements with an acceptable risk profile. Therefore, the ability to combine both valve types in severe emphysema could be a promising option in endoscopic lung volume reduction.

PICC tip dislodgement causing massive pleural effusion and atelectasis with acute respiratory failure: a case report.

Peripheral intravenous central catheter (PICC) is a common tool for intravenous infusion for children who need central venous access. Although it is safe for physicians and nurses to place, complications like infection, occlusion, phlebitis, and bleeding can occur. We report a 5-month-old infant who suffered respiratory failure caused by catheter malposition resulting in massive fluid infusion into the thoracic cavity. Point-of-care ultrasound (POCUS) was utilized to identify a massive pleural effusion that prompted urgent drainage. Complications related to PICC in pediatric patients are not common but difficult to immediately identify sometimes. Therefore, careful attention should be paid by physicians to identify and reduce the risk of complications associated with PICC. Thus, visual tools are strongly advised to enhance the safety of invasive procedures.

Incremental Application of Positive End-Expiratory Pressure for the Evaluation of Atelectasis During RP-EBUS and Bronchoscopy (I-APPEAR).

BACKGROUND: CT-to-body divergence-described as the difference between preprocedural CT scans and intraprocedural lung architecture-is a significant barrier to improving diagnostic yield during navigational bronchoscopy. A major proposed contributor to CT-to-body divergence is the development of atelectasis, which can confound visualization of peripheral lung lesions via radial probe endobronchial ultrasound (RP-EBUS). High positive end-expiratory pressure (PEEP) ventilatory strategies have been used to decrease atelectasis, allowing the lesion to re-APPEAR on intraprocedure imaging. However, standardized PEEP levels may not be appropriate for all patients due to hemodynamic and ventilatory impacts. METHODS: We performed a multicenter, prospective observational study in which patients were imaged with RP-EBUS under general anesthesia to determine if subsegmental atelectasis would resolve as incremental increases in PEEP were applied. Resolution of atelectasis was based on the transition from a non-aerated pattern to an aerated appearance on RP-EBUS. RP-EBUS images were reviewed by 3 experienced operators to determine correlation. RESULTS: Forty-three patients underwent RP-EBUS examination following navigational bronchoscopy. Thirty-seven patients underwent incremental PEEP application and subsequent RP-EBUS imaging. Atelectasis was determined to have resolved in 33 patients (88.2%) following increased PEEP. The intraclass correlation coefficient between reviewers was 0.76. A recruitment maneuver was performed in 7 (16.3%) patients after atelectasis persisted at maximal PEEP. Atelectasis was not identified in the examined subsegments in 6 (10.8%) patients despite zero PEEP. CONCLUSION: RP-EBUS is an effective tool to monitor what pressure atelectasis within a lung segment has resolved with increasing levels of PEEP.

First real-time imaging of bronchoscopic lung volume reduction by electrical impedance tomography.

BACKGROUND: Bronchoscopic lung volume reduction (BLVR) with one-way endobronchial valves (EBV) has better outcomes when the target lobe has poor collateral ventilation, resulting in complete lobe atelectasis. High-inspired oxygen fraction (FIO2) promotes atelectasis through faster gas absorption after airway occlusion, but its application during BLVR with EBV has been poorly understood. We aimed to investigate the real-time effects of FIO2 on regional lung volumes and regional ventilation/perfusion by electrical impedance tomography (EIT) during BLVR with EBV. METHODS: Six piglets were submitted to left lower lobe occlusion by a balloon-catheter and EBV valves with FIO2 0.5 and 1.0. Regional end-expiratory lung impedances (EELI) and regional ventilation/perfusion were monitored. Local pocket pressure measurements were obtained (balloon occlusion method). One animal underwent simultaneous acquisitions of computed tomography (CT) and EIT. Regions-of-interest (ROIs) were right and left hemithoraces. RESULTS: Following balloon occlusion, a steep decrease in left ROI-EELI with FIO2 1.0 occurred, 3-fold greater than with 0.5 (p < 0.001). Higher FIO2 also enhanced the final volume reduction (ROI-EELI) achieved by each valve (p < 0.01). CT analysis confirmed the denser atelectasis and greater volume reduction achieved by higher FIO2 (1.0) during balloon occlusion or during valve placement. CT and pocket pressure data agreed well with EIT findings, indicating greater strain redistribution with higher FIO2. CONCLUSIONS: EIT demonstrated in real-time a faster and more complete volume reduction in the occluded lung regions under high FIO2 (1.0), as compared to 0.5. Immediate changes in the ventilation and perfusion of ipsilateral non-target lung regions were also detected, providing better estimates of the full impact of each valve in place. TRIAL REGISTRATION: Not applicable.

Effects of starting one lung ventilation and applying individualized PEEP right after patients are placed in lateral decubitus position on intraoperative oxygenation for patients undergoing thoracoscopic pulmonary lobectomy: study protocol for a randomized controlled trial.

BACKGROUND: For patients receiving one lung ventilation in thoracic surgery, numerous studies have proved the superiority of lung protective ventilation of low tidal volume combined with recruitment maneuvers (RM) and individualized PEEP. However, RM may lead to overinflation which aggravates lung injury and intrapulmonary shunt. According to CT results, atelectasis usually forms in gravity dependent lung regions, regardless of body position. So, during anesthesia induction in supine position, atelectasis usually forms in the dorsal parts of lungs, however, when patients are turned into lateral decubitus position, collapsed lung tissue in the dorsal parts would reexpand, while atelectasis would slowly reappear in the lower flank of the lung. We hypothesize that applying sufficient PEEP without RM before the formation of atelectasis in the lower flank of the lung may beas effective to prevent atelectasis and thus improve oxygenation as applying PEEP with RM. METHODS: A total of 84 patients scheduled for elective pulmonary lobe resection necessitating one lung ventilation will be recruited and randomized totwo parallel groups. For all patients, one lung ventilation is initiated the right after patients are turned into lateral decubitus position. For patients in the study group, individualized PEEP titration is started the moment one lung ventilation is started, while patients in the control group will receive a recruitment maneuver followed by individualized PEEP titration after initiation of one lung ventilation. The primary endpoint will be oxygenation index measured at T4. Secondary endpoints will include intrapulmonary shunt, respiratory mechanics, PPCs, and hemodynamic indicators. DISCUSSION: Numerous previous studies compared the effects of individualized PEEP applied alone with that applied in combination with RM on oxygenation index, PPCs, intrapulmonary shunt and respiratory mechanics after atelectasis was formed in patients receiving one lung ventilation during thoracoscopic surgery. In this study, we will apply individualized PEEP before the formation of atelectasis while not performing RM in patients allocated to the study group, and then we're going to observe its effects on the aspects mentioned above. The results of this trial will provide a ventilation strategy that may be conductive to improving intraoperative oxygenation and avoiding the detrimental effects of RM for patients receiving one lung ventilation. TRIAL REGISTRATION: www.Chictr.org.cn ChiCTR2400080682. Registered on February 5, 2024.

Clinical validation of the Air-Test for the non-invasive detection of perioperative atelectasis in children.

BACKGROUND: The incidence of anesthesia-induced atelectasis in children is high and closely related to episodes of hypoxemia. The Air-Test is a simple maneuver to detect lung collapse. By a step-reduction in FiO2 to 0.21, a fall in pulse-oximetry hemoglobin saturation <97% unmasks the presence of collapse-related shunt in healthy lungs. The aim of this study was to validate the Air-Test as a diagnostic tool to detect perioperative atelectasis in children using lung ultrasound as a reference. METHODS: We first assessed the Air-Test in a retrospective cohort of 88 anesthetized children (Retrospective study) followed by a prospective study performed in 72 children (45 postconceptional weeks to 16 years old) using a similar protocol (Validation study). We analyzed the performance of the Air-Test to detect atelectasis by an operating characteristic curve (ROC) analysis, using lung ultrasound consolidation score as reference. RESULTS: Preoperative SpO2 was normal in both studies (retrospective 98.7±0.6%, validation 99.0±0.9%). The Air-Test, with a SpO2 cut point <97%, resulted positive in 67 patients in the retrospective study (SpO2 93.3±2.1%) and in 59 in the validation study (SpO2 94.9±1.8%); both P<0.0001. In the validation study, the Air-Test showed a sensitivity of 0.91 (95% CI 0.85-0.92), specificity of 1.00 (95% CI 0.84-1) and an area under the curve (AUC) of 0.98 (95% CI 0.97-1.00). AUC between both studies was similar (P=0.16). CONCLUSIONS: The Air-Test is a noninvasive and accurate method to detect atelectasis in healthy anesthetized children. It can be used as a screening tool to individualize patients that can benefit from lung recruitment maneuvers.

Comparison of the effect of two recruitment manoeuvres to conventional ventilation on lung atelectasis in paediatric laparoscopic surgery- a prospective randomised controlled trial.

BACKGROUND: There is a high incidence of pulmonary atelectasis during paediatric laparoscopic surgeries. The authors hypothesised that utilising a recruitment manoeuvre or using continuous positive airway pressure may prevent atelectasis compared to conventional ventilation. OBJECTIVE: The primary objective was to compare the degree of lung atelectasis diagnosed by lung ultrasound (LUS) using three different ventilation techniques in children undergoing laparoscopic surgeries. DESIGN: Randomised, prospective three-arm trial. SETTING: Single institute, tertiary care, teaching hospital. PATIENTS: Children of ASA PS 1 and 2 up to the age of 10 years undergoing laparoscopic surgery with pneumoperitoneum lasting for more than 30 min. INTERVENTION: Random allocation to one of the three study groups: CG group: Inspiratory pressure adjusted to achieve a TV of 5-8 ml/kg, PEEP of 5 cm H2O, respiratory rate adjusted to maintain end-tidal carbon dioxide (ETCO2) between 30-40 mm Hg with manual ventilation and no PEEP at induction. RM group: A recruitment manoeuvre of providing a constant pressure of 30 cm H2O for ten seconds following intubation was applied. A PEEP of 10 cm H2O was maintained intraoperatively. CPAP group: Intraoperative maintenance with PEEP 10 cm H2O with CPAP of 10 cm H2O at induction using mechanical ventilation was done. OUTCOME MEASURES: Lung atelectasis score at closure assessed by LUS. RESULTS: Post induction, LUS was comparable in all three groups. At the time of closure, the LUS for the RM group (8.6 ± 4.9) and the CPAP group (8.8 ± 6.8) were significantly lower (p < 0.05) than the CG group (13.3 ± 3.8). In CG and CPAP groups, the score at closure was significantly higher than post-induction. The PaO2/FiO2 ratio was significantly higher (p < 0.05) for the RM group (437.1 ± 44.9) and CPAP group (421.6 ± 57.5) than the CG group (361.3 ± 59.4) at the time of pneumoperitoneum. CONCLUSION: Application of a recruitment manoeuvre post-intubation or CPAP during induction and maintenance with a high PEEP leads to less atelectasis than conventional ventilation during laparoscopic surgery in paediatric patients. TRIAL REGISTRY: CTRI/2019/08/02058.

Association between driving pressure-guided ventilation and postoperative pulmonary complications in surgical patients: a meta-analysis with trial sequential analysis.

BACKGROUND: Prior studies have reported inconsistent results regarding the association between driving pressure-guided ventilation and postoperative pulmonary complications (PPCs). We aimed to investigate whether driving pressure-guided ventilation is associated with a lower risk of PPCs. METHODS: We systematically searched electronic databases for RCTs comparing driving pressure-guided ventilation with conventional protective ventilation in adult surgical patients. The primary outcome was a composite of PPCs. Secondary outcomes were pneumonia, atelectasis, and acute respiratory distress syndrome (ARDS). Meta-analysis and subgroup analysis were conducted to calculate risk ratios (RRs) with 95% confidence intervals (CI). Trial sequential analysis (TSA) was used to assess the conclusiveness of evidence. RESULTS: Thirteen RCTs with 3401 subjects were included. Driving pressure-guided ventilation was associated with a lower risk of PPCs (RR 0.70, 95% CI 0.56-0.87, P=0.001), as indicated by TSA. Subgroup analysis (P for interaction=0.04) found that the association was observed in non-cardiothoracic surgery (nine RCTs, 1038 subjects, RR 0.61, 95% CI 0.48-0.77, P< 0.0001), with TSA suggesting sufficient evidence and conclusive result; however, it did not reach significance in cardiothoracic surgery (four RCTs, 2363 subjects, RR 0.86, 95% CI 0.67-1.10, P=0.23), with TSA indicating insufficient evidence and inconclusive result. Similarly, a lower risk of pneumonia was found in non-cardiothoracic surgery but not in cardiothoracic surgery (P for interaction=0.046). No significant differences were found in atelectasis and ARDS between the two ventilation strategies. CONCLUSIONS: Driving pressure-guided ventilation was associated with a lower risk of postoperative pulmonary complications in non-cardiothoracic surgery but not in cardiothoracic surgery. SYSTEMATIC REVIEW PROTOCOL: INPLASY 202410068.

Effect of different lung recruitment strategies and airway device on oscillatory mechanics in children under general anaesthesia.

BACKGROUND: Atelectasis has been reported in 68 to 100% of children undergoing general anaesthesia, a phenomenon that persists into the recovery period. Children receiving recruitment manoeuvres have less atelectasis and fewer episodes of oxygen desaturation during emergence. The optimal type of recruitment manoeuvre is unclear and may be influenced by the airway device chosen. OBJECTIVE: We aimed to investigate the different effects on lung mechanics as assessed by the forced oscillation technique (FOT) utilising different recruitment strategies: repeated inflations vs. one sustained inflation and different airway devices, a supraglottic airway device vs. a cuffed tracheal tube. DESIGN: Pragmatic enrolment with randomisation to the recruitment strategy. SETTING: We conducted this single-centre trial between February 2020 and March 2022. PARTICIPANTS: Seventy healthy patients (53 boys) aged between 2 and 16 years undergoing general anaesthesia were included. INTERVENTIONS: Forced oscillations (5 Hz) were superimposed on the ventilator waveform using a customised system connected to the anaesthesia machine. Pressure and flow were measured at the inlet of the airway device and used to compute respiratory system resistance and reactance. Measurements were taken before and after recruitment, and again at the end of surgery. MAIN OUTCOME MEASURES: The primary endpoint measured is the change in respiratory reactance. RESULTS: Statistical analysis (linear model with recruitment strategy and airway device as factors) did not show any significant difference in resistance and reactance between before and after recruitment. Baseline reactance was the strongest predictor for a change in reactance after recruitment: prerecruitment Xrs decreased by mean (standard error) of 0.25 (0.068) cmH 2 O s l -1 per  1 cmH 2 O -1  s l -1 increase in baseline Xrs ( P  < 0.001). After correcting for baseline reactance, the change in reactance after recruitment was significantly lower for sustained inflation compared with repeated inflation by mean (standard error) 0.25 (0.101) cmH 2 O ( P  = 0.0166). CONCLUSION: Although there was no significant difference between airway devices, this study demonstrated more effective recruitment via repeated inflations than sustained inflation in anaesthetised children. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12619001434189.

Low-volume ventilation of preinjured lungs degrades lung function via stress concentration and progressive alveolar collapse.

Mechanical ventilation can cause ventilation-induced lung injury (VILI). The concept of stress concentrations suggests that surfactant dysfunction-induced microatelectases might impose injurious stresses on adjacent, open alveoli and function as germinal centers for injury propagation. The aim of the present study was to quantify the histopathological pattern of VILI progression and to test the hypothesis that injury progresses at the interface between microatelectases and ventilated lung parenchyma during low-positive end-expiratory pressure (PEEP) ventilation. Bleomycin was used to induce lung injury with microatelectases in rats. Lungs were then mechanically ventilated for up to 6 h at PEEP = 1 cmH2O and compared with bleomycin-treated group ventilated protectively with PEEP = 5 cmH2O to minimize microatelectases. Lung mechanics were measured during ventilation. Afterward, lungs were fixed at end-inspiration or end-expiration for design-based stereology. Before VILI, bleomycin challenge reduced the number of open alveoli [N(alvair,par)] by 29%. No differences between end-inspiration and end-expiration were observed. Collapsed alveoli clustered in areas with a radius of up to 56 µm. After PEEP = 5 cmH2O ventilation for 6 h, N(alvair,par) remained stable while PEEP = 1 cmH2O ventilation led to an additional loss of aerated alveoli by 26%, mainly due to collapse, with a small fraction partly edema filled. Alveolar loss strongly correlated to worsening of tissue elastance, quasistatic compliance, and inspiratory capacity. The radius of areas of collapsed alveoli increased to 94 µm, suggesting growth of the microatelectases. These data provide evidence that alveoli become unstable in neighborhood of microatelectases, which most likely occurs due to stress concentration-induced local vascular leak and surfactant dysfunction.NEW & NOTEWORTHY Low-volume mechanical ventilation in the presence of high surface tension-induced microatelectases leads to the degradation of lung mechanical function via the progressive loss of alveoli. Microatelectases grow at the interfaces of collapsed and open alveoli. Here, stress concentrations might cause injury and alveolar instability. Accumulation of small amounts of alveolar edema can be found in a fraction of partly collapsed alveoli but, in this model, alveolar flooding is not a major driver for degradation of lung mechanics.

A Recruitment Maneuver After Apnea Testing Improves Oxygenation and Reduces Atelectasis in Organ Donors After Brain Death.

BACKGROUND: Hypoxemia is the main modifiable factor preventing lungs from being transplanted from organ donors after brain death. One major contributor to impaired oxygenation in patients with brain injury is atelectasis. Apnea testing, an integral component of brain death declaration, promotes atelectasis and can worsen hypoxemia. In this study, we tested whether performing a recruitment maneuver (RM) after apnea testing could mitigate hypoxemia and atelectasis. METHODS: During the study period, an RM (positive end-expiratory pressure of 15 cm H2O for 15 s then 30 cm H2O for 30 s) was performed immediately after apnea testing. We measured partial pressure of oxygen, arterial (PaO2) before and after RM. The primary outcomes were oxygenation (PaO2 to fraction of inspired oxygen [FiO2] ratio) and the severity of radiographic atelectasis (proportion of lung without aeration on computed tomography scans after brain death, quantified using an image analysis algorithm) in those who became organ donors. Outcomes in RM patients were compared with control patients undergoing apnea testing without RM in the previous 2 years. RESULTS: Recruitment maneuver was performed in 54 patients after apnea testing, with a median immediate increase in PaO2 of 63 mm Hg (interquartile range 0-109, p = 0.07). Eighteen RM cases resulted in hypotension, but none were life-threatening. Of this cohort, 37 patients became organ donors, compared with 37 donors who had apnea testing without RM. The PaO2:FiO2 ratio was higher in the RM group (355 ± 129 vs. 288 ± 127, p = 0.03), and fewer had hypoxemia (PaO2:FiO2 ratio < 300 mm Hg, 22% vs. 57%; p = 0.04) at the start of donor management. The RM group showed less radiographic atelectasis (median 6% vs. 13%, p = 0.045). Although there was no difference in lungs transplanted (35% vs. 24%, p = 0.44), both better oxygenation and less atelectasis were associated with a higher likelihood of lungs being transplanted. CONCLUSIONS: Recruitment maneuver after apnea testing reduces hypoxemia and atelectasis in organ donors after brain death. This effect may translate into more lungs being transplanted.

Delayed targeted atelectasis in a case of bronchoscopic lung volume reduction with endobronchial valves.

A woman in her late 60s with severe chronic obstructive pulmonary disease (COPD) and emphysema underwent bronchoscopic lung volume reduction (BLVR) with endobronchial valves (EBV) to address hyperinflation. The initial EBV placement has led to partial lobar atelectasis of the left lower lobe and resulted in significant improvement in the patient's symptoms and lung function. However, valve migration occurred later due to pneumothorax unrelated to valves, leading to suboptimal clinical improvement. The patient achieved delayed full lobar atelectasis 21 months after EBV placement, which led to a significant clinical improvement. The patient decided to be delisted from the lung transplant list due to the improvement. This case highlights the importance of considering delayed atelectasis as a possible outcome of EBV placement and suggests the need for further exploration of the long-term implications and associations of this procedure.

[A case of nontuberculous mycobacterium presenting as a mass and atelectasis with mediastinal and hilar lymph node enlargement].

With the development of testing technology, the diagnosis of nontuberculous mycobacterium (NTM) lung disease has gradually increased in recent years. Because the clinical characteristics of NTM are not typical, and its imaging manifestations are diverse and nonspecific, missed diagnosis and misdiagnosis are common. Etiological investigation is necessary for diagnosis. Conventional etiological investigations are very limited for the diagnosis of NTM. We reported a case of NTM lung disease presenting with a mass and atelectasis with mediastinal and hilar lymph node enlargement that resembled malignant tumors. The literature on this condition was reviewed to improve the clinician's understanding and broaden clinical thinking.