Perioperative Change of Regional Ventilation During Spontaneous Breathing

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.

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