The Effect of Prolonged Inspiratory Time on Pulmonary Mechanics in Obese Patients

After written informed consent was obtained from all patients, 50 adult patients were enrolled in the study.

The patients met the following inclusion criteria: (1) body mass index (BMI, weight in kilograms divided by the square of height in metres) > 25 kg/m2; (2) American Society of Anesthesiology (ASA) physical status classification grade I or II (BMI by itself was not used as the basis for the ASA classification); (3) aged 20 - 65 years; and (4) scheduled for elective spine surgery in prone position.

Exclusion criteria

• Patients who have severe pulmonary disease:

history of chronic obstructive pulmonary disease (COPD), asthma, or pneumothorax. Patients with haemodynamic instability, hypovolaemia, bronchopleural fistula, The enrolled patients were randomly allocated according to a predetermined allocation sequence to receive an I:E ratio of either 1:1 (group 1:1) or 1:2 (group 1:2).

The allocation sequence with no blocking was generated in an Internet website Standard monitoring techniques, including electrocardiography, pulse oximetry, and noninvasive arterial blood pressure measurement, are applied upon arrival at the operating room.

Anesthesia was induced with intravenous propofol 1.5 mg_kg-1 and rocuronium 0.8 mg_kg-1 was administered intravenously.

After tracheal intubation, volume-controlled ventilation was initiated with an I:E ratio of 1:2 or 1:1, no positive end-expiratory pressure, and a tidal volume of 10 mL per ideal body weight (kg). A respiratory rate was adjusted in order to end-tidal carbon dioxide (EtCO2) of 33 - 36 mmHg during surgery. Anesthesia was maintained with an end-tidal concentration of 2-2.5 vol% sevoflurane in 40% oxygen/air. The bispectral index score was monitored continuously in order to maintain an adequate anesthetic depth and was targeted at a range of 40-60 during surgery.

Radial artery cannulation was conducted for monitoring continuous arterial blood pressure and blood sampling.

Respiratory, hemodynamic, and arterial blood gas data were assessed and recorded at three time points: ten minutes after tracheal intubation in the supine position (T1), 30 min after prone positioning (T2), 90 min after prone positioning(T3). Respiratory data consisted of peak airway pressure, plateau airway pressure, mean airway pressure, static compliance, EtCO2, respiratory rate, and minute volume. Arterial pH, arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2), and lactate level were obtained from arterial blood gas analysis.

Inclusion criteria

• ASA I-II adult patients scheduled for spine surgery under general anesthesia.
• patient age : greater than 20 years and less than 65years
• Body Mass Index(BMI) >25 kg/m2

Exclusion criteria

• Patients who have severe pulmonary disease:

history of chronic obstructive pulmonary disease (COPD), asthma, or pneumothorax. Patients with haemodynamic instability, hypovolaemia, bronchopleural fistula, history of cardiopulmonary disease, or previous lung surgery are excluded.