Effect of prone position on mechanical power in patients undergoning neurosurgical operations

The effect of prone position on mechanical power will be investigated in patients undergoing neurosurgical operations under general anesthesia in prone position. The patient is positioned in the prone position as follows: The table is in a flat position. The arms are extended above the patient's head. The chest wall is supported by rollers that run from the pubic area to the collarbone.The support is placed under the pelvis. Knees and elbows are supported by pillows. The legs are bent up to knee level. The head is turned sideways and supported by a pillow so that there is no pressure on the eyes and ears. The arms are rotated backwards at torso level.The table is inclined to reduce lumbar lordosis. A belt is placed between the subgluteal region and the legs to prevent the patient from slipping caudally or cephalad. Various abdominal supports are placed to prevent pressure on the abdomen, such as tightly wrapped parallelepipeds, adjustable metal frames covered with soft supports, quadrupedal frames and more. Mechanical power refers to the energy delivered into the respiratory system and becomes particularly relevant during mechanical ventilation. Mechanical power is used to encapsulate potential lung injuries, such as barotrauma, atelectotrauma, and volutrauma, into a single value. These injuries often arise due to excessive pressure or volume changes within the lungs. Several parameters are employed in determining mechanical power: tidal volume , driving pressure , peak pressure , flow rate , respiratory rate, and PEEP . These data, recorded on the mechanical ventilation device and customized for the patient's condition, are analyzed using Gattinoni's formula for calculating mechanical power in volume-controlled ventilation: MP = TIDAL VOLUME X RESPIRATORY RATE X 0.098 X [ P PEAK – 1/2(P PLATEAU-PEEP)] This formula enables the calculation of mechanical power, providing insight into how much energy is imparted to the lungs and indicating the potential risk of damage. Mechanical power will be calculated as:15 minutes after anesthesia induction in supine position, 15 minutes after positioning the patient to prone position, and with 1 hour intervals therafter until the end of surgery and the last mechanical power calculations will be done at the end of the operation in prone position and concomittant with positioning the patient to supine before waking up the patient. Prone positioning will be done by the operation room personnel under the control of the anesthesiologist responsible for the care of the patient.