A Functional and Morphologic Analysis of Pressure-Controlled Inverse Ratio Ventilation in Oleic Acid-Induced Lung Injury: Hemodynamics

Cardiac output determinations were carried out in triplicate by injecting 10 ml of ice-cold boli of 5 percent dextrose in the right atrium and recording the thermal dilution curve in the pulmonary artery (Edwards Cardiac Output Computer 9520A). Systemic (SAP) and pulmonary artery pressures (PAP) were recorded (Kontron Medical 8A) using pressure transducers (Medex MX807). The pressure registration system was calibrated against a water column and checked prior to each experiment according to standard procedures.
Functional residual capacity (FRC) was determined twice during each ventilatory setting using the sulfur hexafluoride washin-washout technique.
Airway pressures and gas volumes were recorded from the digital display of the ventilator (Servo). End-expiratory and end-inspiratory hold maneuvers (5 s) were performed to establish static pressure levels. Static total compliance was calculated as expired volume/(static inspiratory pressure-end-expiratory pressure).
End-tidal and mixed expiratory CO2 concentrations were analyzed by capnometry (Siemens 930 CO2 analyzer). Allergies pills comments Arterial and mixed venous blood samples were analyzed in duplicate for P02, Pcc>2, pH, and haemoglobin (ABL 3, Radiometer). Oxygen saturation was determined by spectrophotometry (OSM 3, Radiometer). Oxygen content and venous admixture were calculated according to standard formulas.
All equipment was intermittently checked and calibrated according to the manufacturer’s instructions. Structure and density of the lungs were studied by CT scanning (Somatom Hi Q, Siemens AG, Erlangen, Germany). Transverse CT scans approximately 1 cm above the level of the diaphragm were obtained in end-expiratory and end-inspiratory apnea using the hold function of the ventilator. In each animal, a third scan (dynamic ventilatory cycle) was obtained during a full ventilatory cycle using a scan time of 4 s (respiratory rate was 15/min). Scans were obtained at 225 mA and 133 kV using a slice thickness of 2 cm. The table position was kept constant throughout each individual experiment.

This entry was posted in Respiratory Failure and tagged , , , .