Low-Dose CT Screening of Persistent Subsolid Lung Nodules: First-Order Features in Radiomics.

BACKGROUND: Nondisappearing subsolid nodules requiring follow-up are often detected during lung cancer screening, but changes in their invasiveness can be overlooked owing to slow growth. We aimed to develop a method for automatic identification of invasive tumors among subsolid nodules during multiple health checkups using radiomics technology based on low-dose computed tomography (LD-CT) and examine its effectiveness. METHODS: We examined patients who underwent LD-CT screening from 2014 to 2019 and had lung adenocarcinomas resected after 5-year follow-ups. They were categorized into the invasive or less-invasive group; the annual growth/change rate (Δ) of the nodule voxel histogram using three-dimensional CT (e.g., tumor volume, solid volume percentage, mean CT value, variance, kurtosis, skewness, and entropy) was assessed. A discriminant model was designed through multivariate regression analysis with internal validation to compare its efficacy with that of a volume doubling time of < 400 days. RESULTS: The study included 47 tumors (23 invasive, 24 less invasive), with no significant difference in the initial tumor volumes. Δskewness was identified as an independent predictor of invasiveness (adjusted odds ratio, 0.021; p = 0.043), and when combined with Δvariance, it yielded high accuracy in detecting invasive lesions (88% true-positive, 80% false-positive). The detection model indicated surgery 2 years earlier than the volume doubling time, maintaining accuracy (median 3 years vs.1 year before actual surgery, p = 0.011). CONCLUSION: LD-CT radiomics showed promising potential in ensuring timely detection and monitoring of subsolid nodules that warrant follow-up over time.

The treatment and survival of patients with postoperative recurrent thymic carcinoma and neuroendocrine carcinoma: a multicenter retrospective study.

PURPOSE: There are few data available on the outcomes of postoperative recurrent thymic carcinoma (TC) and thymic neuroendocrine carcinoma (TNEC). The aim of this study is to evaluate the treatment and survival in patients with recurrent TC and TNEC after undergoing surgical resection. METHODS: A retrospective chart review was performed using our multicenter database to identify patients with a postoperative recurrence of TC and TNEC from 1995 to 2018. The clinicopathological factors were reviewed and the survival outcomes were analyzed. RESULTS: Sixty patients were identified among 152 patients who underwent resection of TC and TNEC. The median follow-up period from the first recurrence was 14.8 months (range 0-144). The 5-year post-recurrence survival was 23% for the whole cohort. According to a univariable analysis, advanced stage [hazard ratio (HR) 2.81, 95% confidence interval (CI) 1.09-9.54], interval between primary surgery and recurrence (HR 0.97, 95% CI 0.95-0.99), any treatment for recurrence (HR: 0.27, 95% CI 0.13-0.58) and chemotherapy for recurrence (HR: 0.46, 95% CI 0.22-0.95) were significant factors related to post-recurrence survival. CONCLUSIONS: Chemotherapy rather than surgery appears to be the mainstay treatment for managing patients with postoperative recurrent TC and TNEC and it may also be considered in multidisciplinary management. Further studies with a larger sample size are required to confirm our findings.

[Thoracic Incisions for Open Chest Surgery;Posterolateral Thoracotomy, Anterolateral Thoracotomy, Axillary Thoracotomy, and Muscle Sparing Thoracotomy].

Lung disease requiring surgical treatment has shifted from pulmonary tuberculosis that was prevalent in the 1940s during wartime to lung cancer in the last half century. The surgical approach for pulmonary tuberculosis was open chest surgery. Likewise for lung cancer, a thoracotomy approach had initially been used for a while. Thoracoscopic minimally invasive surgery became more widely used around 1990 and was shown to improve the patient's quality of life (QOL). Currently, thoracoscopic surgery and robotic surgery are the mainstream procedures for patients with lung cancer, and thoracotomy procedures have fallen out of favor. However, in some cases of unexpected bleeding from the pulmonary artery or tumor infiltration into the pulmonary artery, appropriate thoracotomy must be performed. In this volume, 4 representative methods of performing thoracotomy are described with some tips in Japanese.

Hepatic Flavin-Containing Monooxygenase 3 Enzyme Suppressed by Type 1 Allergy-Produced Nitric Oxide.

Flavin-containing monooxygenases (FMOs) are major mammalian non-cytochrome P450 oxidative enzymes. T helper 2 cell-activated allergic diseases produce excess levels of nitric oxide (NO) that modify the functions of proteins. However, it remains unclear whether allergy-induced NO affects the pharmacokinetics of drugs metabolized by FMOs. This study investigated alterations of hepatic microsomal FMO1 and FMO3 activities in type 1 allergic mice and further examined the interaction of FMO1 and FMO3 with allergy-induced NO. Imipramine (IMP; FMO1 substrate) N-oxidation activity was not altered in allergic mice with high serum NO and immunoglobulin E levels. At 7 days after primary sensitization (PS7) or secondary sensitization (SS7), benzydamine (BDZ; FMO1 and FMO3 substrate) N-oxygenation was significantly decreased to 70% of individual controls. The expression levels of FMO1 and FMO3 proteins were not significantly changed in the sensitized mice. Hepatic inducible NO synthase (iNOS) mRNA level increased 5-fold and 15-fold in PS7 and SS7 mice, respectively, and hepatic tumor necrosis factor-α levels were greatly enhanced. When a selective iNOS inhibitor was injected into allergic mice, serum NO levels and BDZ N-oxygenation activity returned to control levels. NO directly suppressed BDZ N-oxygenation, which was probably related to FMO3-dependent metabolism in comparison with IMP N-oxidation. In hepatic microsomes from PS7 and SS7 mice, the suppression of BDZ N-oxygenation was restored by ascorbate. Therefore, type 1 allergic mice had differentially suppressed FMO3-dependent BDZ N-oxygenation. The suppression of FMO3 metabolism related to reversible S-nitrosyl modifications of iNOS-derived NO. NO is expected to alter FMO3-metabolic capacity-limited drug pharmacokinetics in humans.

Pharmacokinetics and Differential Regulation of Cytochrome P450 Enzymes in Type 1 Allergic Mice.

Type 1 allergic diseases are characterized by elevated production of specific immunoglobulin E (IgE) for each antigen and have become a significant health problem worldwide. This study investigated the effect of IgE-mediated allergy on drug pharmacokinetics. To further understand differential suppression of hepatic cytochrome P450 (P450) activity, we examined the inhibitory effect of nitric oxide (NO), a marker of allergic conditions. Seven days after primary sensitization (PS7) or secondary sensitization (SS7), hepatic CYP1A2, CYP2C, CYP2E1, and CYP3A activities were decreased to 45%-75% of the corresponding control; however, CYP2D activity was not downregulated. PS7 and SS7 did not change the expression levels of five P450 proteins. Disappearance of CYP1A2 and CYP2D substrates from the plasma was not significantly different between allergic mice and control mice. In contrast, the area under the curve of a CYP1A2-mediated metabolite in PS7 and SS7 mice was reduced by 50% of control values. Total clearances of a CYP2E1 substrate in PS7 and SS7 mice were significantly decreased to 70% and 50% respectively, of the control without altering plasma protein binding. Hepatic amounts of CYP1A2 and CYP2E1 substrates were enhanced by allergic induction, being responsible for each downregulated activity. NO scavenger treatment completely improved the downregulated P450 activities. Therefore, our data suggest that the onset of IgE-mediated allergy alters the pharmacokinetics of major P450-metabolic capacity-limited drugs except for CYP2D drugs. NO is highly expected to participate in regulatory mechanisms of the four P450 isoforms.

[Preoperative Arterial Embolization with N-butyl-2 Cyanoacrylate for Chronic Cavitary Pulmonary Aspergillosis with Trauma Induced Type â Diabetes Mellitus].

A 50-year-old man with hemoptysis, given a diagnosis of left upper lobe pulmonary aspergilloma with cavity and fungus ball by computed tomography. He has a history of typeⅠ diabetes mellitus due to traumatic injury of pancreas and underwent diaphragm plasty. Despite of systemic anti-fungal medication, symptom and radiological findings were not progressed and surgical intervention was planned. Before surgery we performed intercostal artery embolization, in order to minimize bleeding on dissecting adhesion between the chest wall and the lobe with aspergilloma. Left upper lobectomy with muscle-flap prombage was done safely with a blood loss of 450 ml. Postoperative course was favorable. Intercostal artery embolization with N-butyl-2cyanoacrylate is an effective way to minimize hemorrhage during surgical resection for pulmonary aspergillosis with sever adhesion.

Impact of the cardiac arrest mode on cardiac death donor lungs.

BACKGROUND: Donation after cardiac death (DCD) organs could alleviate the shortage of donor lungs. This study aimed to assess the influence on lung injuries of the way in which cardiac arrest was induced and to investigate the mechanisms leading to any differences. MATERIALS AND METHODS: Male rats were allocated into three groups as follows: sham (no warm ischemia), ventricular fibrillation (VF), and asphyxia group. Cardiac arrest was induced by either VF by way of a fibrillator or asphyxia caused by withdrawal of ventilation, which reflected uncontrolled and controlled DCD situations, respectively. The impact on lung flushing after 60 min of warm ischemia time was evaluated (n = 5, in each group). The physiological functions of the lungs in an isolated lung perfusion circuit were also evaluated with warm ischemia time prolonged to 150 min (n = 8, in each group). Messenger RNA expression levels of surfactant proteins (SPs) and inflammatory cytokines, pathologic findings, and high-energy phosphates of the lung tissues were investigated. RESULTS: In the asphyxia group, flushing and physiological functions in the isolated lung perfusion circuit were the most severely affected. Reverse transcription-polymerase chain reaction and pathologic findings revealed depletion of surfactant protein (SP)-C in lung tissues of the asphyxia group after reperfusion. The VF group was characteristic with elevated pulmonary vascular resistance. CONCLUSIONS: Lung injuries were mainly attributed to alveolar wall damage and depletion of SP in the asphyxia group, and perivascular area prominent edema in the VF group. DCD donor lungs were affected differently by the way in which cardiac arrest was induced.

Gastroparesis after living-donor lobar lung transplantation: report of five cases.

Gastroparesis is a challenging gastrointestinal complication of deceased-donor lung transplantation and heart-lung transplantation, but it has not been reported after living-donor lobar lung transplantation (LDLLT). To better understand this complication after LDLLT, we reviewed our institutional experiences. Among the 32 patients who survived for at least 3 months after LDLLT, five (16 %) developed symptomatic gastroparesis. All five patients had undergone bilateral LDLLT, and gastroparesis was diagnosed within 2 months after transplantation. Neither adult patients who received single lobar LDLLT nor pediatric patients who received either bilateral or single lobar LDLLT developed gastroparesis. Although gastroparesis-related symptoms improved after medical treatment in three patients, two patients died of complications related to gastroparesis. We conclude that gastroparesis can occur after LDLLT and may cause grave complications unless carefully managed.

Clinical application of ET-Kyoto solution for lung transplantation.

Because of the severe donor shortage in Japan, even after the revision of the Organ Transplant Law in 2010, the frequency of recovery of extended criteria lungs has increased in Japan. We developed a new lung preservation solution, "ET-Kyoto solution," to enhance lung preservation, to minimize primary graft dysfunction (PGD) and to improve the post-transplant outcomes. In this study, we retrospectively analyzed our results of lung transplantation using the ET-Kyoto solution. From 2002 to 2012, 26 patients underwent transplantation of lungs preserved with ET-Kyoto solution from brain-dead donors. We retrospectively reviewed the post-transplant pulmonary function and long-term survival. The graft performance was assessed by the PGD grading system. The mean graft ischemic time was 483.8 ± 19.0 min. The oxygenation capacity after reperfusion and recovery of respiratory function were both acceptable despite the long ischemic time. The survival rate at 5 years after transplantation was 85.1 %. Lungs preserved by ET-Kyoto solution had satisfactory postoperative lung function, despite the long preservation time, with excellent long-term survival. The results were acceptable for the use of grafts with a long ischemic time.

Identification of subsets of patients with favorable prognosis after recurrence in completely resected non-small cell lung cancer.

BACKGROUND: This retrospective study aimed to determine prognostic factors associated with postrecurrence survival of completely resected non-small cell cancer patients with postoperative recurrence. METHODS: Characteristics, treatment modality, and postrecurrence survival of 234 patients (157 males and 77 females, mean age at recurrence: 68.7 years, 152 adenocarcinomas and 82 non-adenocarcinomas), who underwent complete resection for non-small cell lung cancer between 2003 and 2009 at our hospital and experienced recurrence, were analyzed for prognostic factors. Cox proportional hazard model was applied for multivariate analysis. RESULTS: Among 234 patients, the median survival time after the diagnosis of recurrence was 21 months, and the 5-year postrecurrence survival rate was 19.9 %. Eastern Cooperative Oncology Group Performance Status (ECOG PS) (hazard ratio [HR]: ECOG PS-0/PS-1/PS-2 = 1/3.313/7.622), time to recurrence after surgery (HR: >2 years/1-2 years/<1 year = 1/1.881/2.185), and number of initial recurrent organs (HR: 1 organ/2 organs/3 or more organs = 1/1.896/2.818) were independent prognostic factors. Patients who received resection or stereotactic irradiation for limited number of brain metastases or solitary extracranial metastasis, and those who received mediastinal radiation or chemoradiation for recurrence at regional lymph nodes and/or resected stump had better survival (median survival time after recurrence: 34, 64, and 25 months, respectively). CONCLUSIONS: Poor ECOG PS, shorter time from initial surgery to recurrence, and increasing number of initial recurrent regions are associated with poor prognosis after recurrence. When the number of recurrent lesions is limited, intensive local treatment with curative intent should be applied for achieving long-term postrecurrence survival.

Redo living-donor lobar lung transplantation for bronchiolitis obliterans associated with antibody-mediated rejection.

Living-donor lobar lung transplantation (LDLLT) is an established therapy for patients with end-stage lung disease, but living-donor lobar lung retransplantation (re-LDLLT) is rarely reported. We previously reported a case of unilateral antibody-mediated rejection after LDLLT in the presence of newly formed donor-specific antibodies against a right-lobe donor. The same patient developed contralateral bronchiolitis obliterans, resulting in bilateral bronchiolitis obliterans, but re-LDLLT was successful. Pathological findings of the explanted lungs were consistent with the clinical course of the patient. One year after re-LDLLT, the patient is doing well without any anti-human leukocyte antigen antibodies. Four lobes from four different donors were transplanted in this patient. The first two lobes were rejected eventually, but the two lobes implanted later presented no signs of rejection at least for 1 year after the transplant. Herein, we report this rare case and compare the clinical course and pathological findings.

Prognostic factors for patients in postoperative brain metastases from surgically resected non-small cell lung cancer.

BACKGROUND: Postoperative recurrence in non-small cell lung cancer (NSCLC) reduces the life expectancy of patients. In this retrospective study, we investigated the prognostic factors in patients with postoperative brain metastases from surgical resected non-small cell lung cancer (NSCLC). METHODS: We conducted a retrospective chart review of patients who had undergone resection for NSCLC between April 2004 and February 2009 and found 65 had experienced postoperative brain metastases by March 2010. We reviewed these patients for clinicopathological information, treatments and responses to treatment, and overall survival. RESULTS: The 5-year survival rate after the diagnosis of brain metastases was 15.4 %. Significantly favorable prognostic factors for patients after a diagnosis of brain metastases included female gender, adenocarcinoma, a small number (1-3) of brain metastases, no extracranial metastasis at the diagnosis of brain metastases, radiation treatment (whole-brain radiation and/or stereotactic irradiation), and local treatment [stereotactic irradiation and/or surgical operation (craniotomy)]. Furthermore, in patients with only brain metastases as the postoperative initial recurrence, the favorable positive prognostic factors included a small number (1-3) of brain metastases, adjuvant chemotherapy, chemotherapy (including adjuvant and other chemotherapy and excluding epidermal growth factor receptor-tyrosine kinase inhibitors), and local treatment. CONCLUSIONS: Our study found that the foregoing clinical characteristics in postoperative brain metastases and the administration of treatment contributed to patient life expectancy.

Interim report of the Japanese original donor evaluation and management system: the medical consultant system.

PURPOSE: Lung transplantation (LTx) is an established therapy for end-stage lung failure. However, in Japan, the donor organ shortage is extremely severe compared with other developed countries, because of the strict Japanese Organ Transplantation Law. To maximize LTx opportunities in Japan, we have established a special donor evaluation and management system termed the medical consultant (MC) system. METHODS: Data from 171 lung donor candidates registered in Japan from May 1998 to May 2012 were obtained and investigated in a retrospective manner. The candidates were separated into the non-MC-intervened and MC-intervened groups, and then data regarding the PaO2/FiO2 ratio, donation rate and organ survival rate were analyzed and compared between the groups. RESULTS: The PaO2/FiO2 ratio of the MC-intervened group was ameliorated from the time of first brain death diagnosis to organ harvest. Although the base condition of the MC-intervened group was significantly worse than that of the non-MC-intervened group, the donation rates showed no significant difference (0.64 and 0.66, respectively; p = 0.89). There was a difference in the organ survival rate between the non-MC and MC-intervened groups (5-year survival rates of 67.2 and 88.3 %, respectively; p = 0.16). CONCLUSION: The MC system used for organ donor evaluation and management in Japan has achieved acceptable interim results.

Uniportal thoracoscopic plication of diaphragmatic eventration: loop needle technique for better visualization.

Symptomatic unilateral diaphragmatic eventration require surgical intervention. A 56-year-old woman complained of dyspnoea on exertion and was noted to have left diaphragm elevation on chest radiographs. Dynamic magnetic resonance imaging showed paradoxical movement of the left diaphragm. We performed diaphragmatic plication by uniportal thoracoscopy with knifeless endostaplers and a loop needle device. Her symptoms significantly improved immediately after the operation, and this condition had been maintained for 6 months. We thus suggest this minimally invasive technique as an easy and safe method for diaphragmatic plication.

Zero-leak prediction during major lung resection aiming for minimal chest drainage duration: a retrospective analysis.

BACKGROUND: Early chest tube removal should be considered to enhance recovery after surgery. The current study aimed to provide a predictive algorithm for air leak episodes (ALE) and to create a knowledge base for early chest tube removal. METHODS: This retrospective study enrolled patients who underwent thoracoscopic anatomical pulmonary resections in our unit. We defined ALE as any airflow ≥ 10 mL/min recorded in the follow-up charts based on the digital thoracic drainage device. Multivariate regression analysis was used to control for preoperative and intraoperative confounding factors. The ALE prediction algorithm was constructed by combining an additive ALE risk-scoring system using the coefficients of the significant predictive factors with the intraoperative water-sealing test. RESULTS: In 485 consecutive thoracoscopic major pulmonary resections, ALE developed in 209 (43%) patients. Statistically significant ALE-associated preoperative factors included male sex, lower body mass index, radiologically evident emphysema, lobectomy, and upper lobe surgery. Significant ALE-associated intraoperative factors were incomplete fissure and pleural adhesion. The ALE risk scoring demonstrated an average area under the receiver operating characteristic curve of 0.72 in the fivefold cross-validation test. The ALE prediction algorithm correctly predicted ALE-absent patients at a negative predictive value of 80%. CONCLUSIONS: The algorithm may promote the optimization of the chest tube-dwelling duration by identifying potential ALE-absent patients for accelerated tube removal.

Multimodal modeling with low-dose CT and clinical information for diagnostic artificial intelligence on mediastinal tumors: a preliminary study.

BACKGROUND: Diagnosing mediastinal tumours, including incidental lesions, using low-dose CT (LDCT) performed for lung cancer screening, is challenging. It often requires additional invasive and costly tests for proper characterisation and surgical planning. This indicates the need for a more efficient and patient-centred approach, suggesting a gap in the existing diagnostic methods and the potential for artificial intelligence technologies to address this gap. This study aimed to create a multimodal hybrid transformer model using the Vision Transformer that leverages LDCT features and clinical data to improve surgical decision-making for patients with incidentally detected mediastinal tumours. METHODS: This retrospective study analysed patients with mediastinal tumours between 2010 and 2021. Patients eligible for surgery (n=30) were considered 'positive,' whereas those without tumour enlargement (n=32) were considered 'negative.' We developed a hybrid model combining a convolutional neural network with a transformer to integrate imaging and clinical data. The dataset was split in a 5:3:2 ratio for training, validation and testing. The model's efficacy was evaluated using a receiver operating characteristic (ROC) analysis across 25 iterations of random assignments and compared against conventional radiomics models and models excluding clinical data. RESULTS: The multimodal hybrid model demonstrated a mean area under the curve (AUC) of 0.90, significantly outperforming the non-clinical data model (AUC=0.86, p=0.04) and radiomics models (random forest AUC=0.81, p=0.008; logistic regression AUC=0.77, p=0.004). CONCLUSION: Integrating clinical and LDCT data using a hybrid transformer model can improve surgical decision-making for mediastinal tumours, showing superiority over models lacking clinical data integration.

Successful thoracoscopic operative approach for refractory pneumothorax in interstitial lung disease under local anaesthesia.

Refractory pneumothorax associated with interstitial lung disease (ILD) remains a challenging condition due to the patient's tolerability and lung compliance that restrict the feasibility of aggressive interventions. Additionally, many cases recur after improvement with treatment, and reports of successful management for this complicated condition are limited. Herein, we report the case of a 60-year-old man with ILD, utilizing home oxygen therapy, who experienced a successful recovery from a surgical intervention under local anaesthesia for pneumothorax. This case highlights the potential for operative intervention under local anaesthesia as a viable option for patients who do not respond to internal approaches.

Pulmonary Sclerosing Pneumocytoma: A Case Revealed During 8-Year of Follow-up with CT imaging.

Pulmonary sclerosing pneumocytoma (PSP) is a rare, benign tumor. Given the challenges of a bronchoscopic diagnosis, surgery is performed during the early stages of the disease. Therefore, little is known about the growth pattern of PSP. This case of PSP was not diagnosed despite bronchoscopy, resulting in lung resection eight years after the anomaly was first identified on computed tomography (CT). This report compares the long-term follow-up of CT and pathological findings and discusses the difficulty in making a diagnosis using a bronchoscopic forceps biopsy to aid in future PSP diagnoses and treatment planning.

Postoperative respiratory management in living donor lobar lung transplantation.

BACKGROUND: We evaluated postoperative respiratory management of living donor lobar lung transplantation (LDLLT). METHODS: Perioperative variables were reviewed in 21 patients who underwent LDLLT at our institution. Recipients were kept intubated for at least two d after LDLLT to maintain optimal expansion of the implanted lobes. Subsequently, if weaning from artificial ventilation could be tolerated, extubation was considered with the assistance of non-invasive ventilation (NIV). If this could not be tolerated, early tracheostomy was considered. RESULTS: All 21 recipients were weaned from artificial ventilation. Twelve patients underwent tracheotomy 4.4 ± 1.8 d after LDLLT and were weaned from artificial ventilation 24.3 ± 17.0 d after LDLLT. Eleven patients were extubated 3.6 ± 1.7 d after LDLLT with NIV, but two of them were reintubated, and finally weaned from artificial ventilation via tracheostomy. Excluding these two patients, NIV was required for 3.8 ± 3.9 d after extubation. The early postoperative course was significantly eventful in patients with tracheostomies, and artificial ventilation, ventilatory support, and intensive care unit stays were longer. Twenty patients (95%) showed survival at 24.4 ± 13.4 months of follow-up. CONCLUSIONS: Postoperative respiratory management with NIV and early tracheostomy were useful after LDLLT.

Multi-frequency forced oscillation technique using impulse oscillations: can it give mechanical information about the lung periphery?

Forced oscillation techniques (FOTs) using sine curved oscillatory waves are used for assessing the lung periphery, but measure only overall respiratory mechanics. Therefore, mathematical models of the respiratory system serve as vehicles to obtain detailed mechanics. Although the simplest model of respiratory mechanics is a simple 3-element series (RIC) model, the constant phase (CP) model is recently used for characterizing respiratory mechanics, which has the advantage of partitioning of respiratory mechanics into airway and tissue components. Meanwhile, FOTs using non-sine curved oscillatory waves are easily applied in patients with severe respiratory diseases because they do not require voluntary apnea. If the latter type of FOTs is as informative as the former, the question arises whether a FOT using non-sine curved oscillatory waves (IOS) could be used to study mechanical properties of the lung periphery. And the CP model should fit the impedance spectra. To answer this, subjects with lymphangioleiomyomatosis (LAM) were recruited as a cohort of patients with lung parenchymal disease. Impedance spectra obtained by the IOS were fitted to the CP and RIC models. Mean values of goodness of fit from the CP and RIC models were 0.978 ± 0.022 and 0.968 ± 0.026, respectively. The extra sum-of-squares F test was used to compare the two mathematical models. The F ratio was 2.37 ± 1.40 and the p-value was 0.29 ± 0.21. Unfortunately, there was no compelling evidence for adopting the CP model for the evaluation of impedance spectra obtained by IOS. This result might relate to the uncertainty of IOS for detecting mechanical properties of the lung periphery.