Ventilation Strategy for the Elderly Patients in Prone Position

Modification of Ventilation Strategy for the Elderly Patients During Spine Surgery in Prone Position

The investigators compare three ventilation modes; volume controlled ventilation, volume guaranteed pressure controlled ventilation and volume controlled ventilation with pause during spine surgery for the elderly patients. The investigators can reveal that how lung collapse can be reduced by optimizing the inspiratory flow pattern under general anesthesia.

<Protocol>

1. All patients were ventilated by an anaesthesia ventilator (Zeus, Dräger, Lübeck, Germany) under general anesthesia.

2. Ventilation strategy:

   • Pressure controlled ventilation volume guaranteed (PCV-VG) mode or volume control ventilation (VCV) mode
   • tidal volume 6-8 mL/kg (predicted body weight)
   • Inspiratory/expiratory (I/E) ratio 1:1.5
   • Inspired oxygen concentration (FIO2) 0.5 with air
   • 3.0 L/min of inspiratory fresh gas flow
   • Positive end-expiratory pressure (PEEP) of 5 cm H2O
   • Respiratory rate (RR) of 10 to 14 min-1

3. After prone positioning and hemodynamic condition was stabilized, patients were ventilated with VCV, PCV-VG mode, VCV with pause following a randomized order, previously determined for each patient. Before each ventilator setting was started, lung recruitment maneuvers were performed to set the lungs to a defined baseline status.

   • ventilation order : one of the following examples is taken by randomization.

VCV 15 min -- VCV pause 15min -- PCV-VG 15min

VCV 15 min -- PCV-VG 15min -- VCV pause 15min

VCV pause 15min -- VCV 15 min -- PCV-VG 15min

VCV pause 15min -- PCV-VG 15min -- VCV 15 min

PCV-VG 15min -- VCV 15 min -- VCV pause 15min

PCV-VG 15min -- VCV pause 15min -- VCV 15 min

Inclusion Criteria:

• patients undergoing elective spine surgery under general anesthesia

Exclusion Criteria:

• obesity (body mass index >35 kg/m2)
• chronic obstructive pulmonary disease
• respiratory infection