Perioperative Change of Regional Ventilation During Spontaneous Breathing

Study Overview
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Brief Summary
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Perioperative changes in regional ventilation by pulmonary electrical impedance tomography and spirometry will be investigated in patients at risk for postoperative pulmonary complications. Those patients undergo abdominal and limb operations. In a pilot study arm electrical impedance tomography is tested in patients receiving osteosynthesis of serial rib fractures.

Detailed Description
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Postoperative pulmonary complications (Defined as pulmonary infection, pleural effusion, atelectasis, pneumothorax, bronchospasm, aspiration pneumonitis or respiratory insufficiency subsequent to surgery) increase the morbidity and mortality of surgical patients. Several independent factors determined by the patients' characteristics and the operative procedure increase the risk for those complications. The postoperative decrease of values measured by spirometry, such as the forced vital capacity (FVC) and forced expiratory volume in one second (FEV1), were found in patients after major surgical procedures for several days. The postoperative reduction of those measurement can be the result of general functional limitations in those patients (e.g. by postoperative pain) or the result of a regional postoperative pulmonary complication (e.g. atelectasis, pleural effusion). The method of the electrical impedance tomography (EIT) enables to visualize the regional ventilation within a transversal section of the lung in real time. Studies examining the change of pulmonary EIT for several days postoperatively in spontaneously breathing patients are lacking. The aim of the present study is to examine perioperative changes in regional ventilation in spontaneously breathing patients during their recovery after abdominal and limb surgery. Moreover, the association of those changes with expected changes in spirometry is tested. Finally, in patients with evident postoperative pulmonary complications the value of pulmonary EIT to detect those changes is investigated. The study should improve the knowledge about the development of postoperative pulmonary complications and test the scientific and clinical value of pulmonary EIT in those spontaneously breathing patients. In a group of patients undergoing osteosynthesis of a flail chest, it is tested how regional ventilation changes by these operations and whether pulmonary EIT is actually usable in these patients.

Official Title
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Perioperative Change of Regional Ventilation During Spontaneous Breathing

Conditions
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Pulmonary Infection, Pleural Effusion, Atelectasis, Pneumothorax, Bronchospasm, Aspiration Pneumonitis, Respiratory Insufficiency

Intervention / Treatment
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* Other: Perioperative pulmonary function tests


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Adult Inpatient Surgery under general anesthesia with and without additional regional anesthesia increased risk for postoperative pulmonary complications according to the ARISCAT-Score (except pilot arm for osteosynthesis of flail chest) Exclusion Criteria: Missing informed consent Outpatient Emergency procedure Revision surgery of hospitalized patients Operation under local or regional anesthesia alone Expected postoperative ventilation Expected hospital stay of less than three days Pregnancy Allergy against material of the electrode belt (silicone rubber, stainless steel, gold-plated brass) Injured, inflamed or otherwise affected skin within the target region of the electrode belt Unstable spine injury Body mass index of more than 50 kg/m2 Incapacity to lie quietly for the examination Pacemaker, defibrillator or other active implant Reoperation before the examination at the third postoperative day

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| abdominal surgery<br>27 patients undergoing abdominal surgery having an elevated risk for postoperative pulmonary complications will be examined by perioperative pulmonary function tests | Other: Perioperative pulmonary function tests<br>* Pulmonary electrical impedance tomography, spirometry, pulse oximetry and query performed preoperatively, at the first and the third postoperative day<br>|
| limb surgery<br>27 patients undergoing upper and lower limb surgery having an elevated risk for postoperative pulmonary complications will be examined by perioperative pulmonary function tests | Other: Perioperative pulmonary function tests<br>* Pulmonary electrical impedance tomography, spirometry, pulse oximetry and query performed preoperatively, at the first and the third postoperative day<br>|
| flail chest<br>10 patients undergoing an operative stabilization of a flail chest will be examined by perioperative pulmonary function tests | Other: Perioperative pulmonary function tests<br>* Pulmonary electrical impedance tomography, spirometry, pulse oximetry and query performed preoperatively, at the first and the third postoperative day<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline in regional ventilation at the first postoperative day | Regional ventilation is measured by pulmonary electrical impedance tomography. The change in the calculated 'Center of Ventilation' in the sagittal direction is used for the primary outcome measure. Power calculation accounts for the use of two time points for the primary outcome measure. | baseline and 1. postoperative day | 
| Change from baseline in regional ventilation at the third postoperative day | Regional ventilation is measured by pulmonary electrical impedance tomography. The change in the calculated 'Center of Ventilation' in the sagittal direction is used for the primary outcome measure. Power calculation accounts for the use of two time points for the primary outcome measure. | baseline and 3. postoperative day | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in forced vital capacity (FVC) | Measured by spirometry. The best value of three attempts is used. | baseline, 1. and 3. postoperative day |