Lungs Aeration Changes Examined by Impedance Tomography During High Frequency Jet Ventilation.

The study was performed in the Department of Anaesthesiology and Intensive Therapy in Zabrze.

After application of eligibility criteria 30 patients were enrolled in a prospective, observational study. Each patient received an information about the study and the consent form to carry out the measurement procedures was obtained. The data about sex, age, weight, height, comorbidities, BMI were collected.

Patients were given premedication, midazolam (Sopodorm, ICN Polfa Rzeszow, Poland; doses: weight 80kg - 7.5 mg; weight 80-100kg - 15mg) on hour before projected surgery.

Upon arrival to the operating room patient's basic monitoring was provided: ECG (3 leads), heart rate, noninvasive measurement of blood pressure (NIBP), and pulse oximetry. At the same time, a belt with electrodes was put on a patient to monitor impedance tomography, then an automatical record of the basic parameters of regional lung ventilation was turned on.

The medications used for induction of anesthesia: fentanyl (Fentanyl WZF, Polfa Warsaw, Poland) at a dose of 2 g /kg bw i.v., propofol (Diprivan, AstraZeneca, PolskaPlofed Polpharma Poland) at a dose of 2 mg / kg bw, i.v. and to carry out an intubation - cis-atracurium (Nimbex, GlaxoSmithKine, UK) at dose of 0.15 mg /kg bw i.v. During rigid bronchoscopy maintenance of general anesthesia was achieved through the supply of intravenous propofol at a dose of 10 - 6 mg/kg bw/h.The high frequency jet ventilation (HFJV) was performed with proper respirator (Universal Jet Ventilator Monsoon DeLuxe ACUTRONIC Switzerland), using following ventilation parameters: f = 160-200 breaths / min, FiO2 (fraction of inspired oxygen) = 1, the DP (drive pressure) = 1.5-2.5 Atm. Simultaneously, patients were monitored using a PulmoVista 500 Dräger device and aeration of the lungs examined by electrical impedance tomography were observed in a monitor.

During anesthesia, patients received hydration in the form of a 0.9% solution of Ringer's lactate at 4 ml/kg bw/h. In the event of bradycardia atropine (Atropine sulfuricum, Polfa Warsaw, Poland) at dose of 0.5 mg iv was given, in the event of a decrease in mean arterial pressure below 70 mmHg or 25% compared to the output pressure, ephedrine (Ephedrinum Hydrochloricum WZF, Polfa Warsaw, Poland) in fractionated doses of 5 mg iv (Max 25 mg) was given and in the case of the ineffectiveness of the proceedings dopamine infusion (Dopaminum Hydrochloricum WZF 4%, Polfa Warsaw, Poland) in the syringe pump titrated to maintain a mean arterial pressure above 70 mmHg.

Recovery from anesthesia took place at the recovery room after the removal of the anesthetics and muscle relaxants. If necessary, reverse the action of muscle relaxants was announced neostigmine (Polstygminum, Teva Pharmaceuticals Poland, Poland) at a dose of 0.5 - 2.5 mg i.v.

During anesthesia following parameters were monitored: ECG (3 leads), heart rate, noninvasive blood pressure (NIBP) every 3 minutes and arterial oxygen saturation measured by pulse oximetry.