Patients undergoing retrograde intrarenal surgery for kidney stones from November 2017 to May 2018 were prospectively recruited to participate in the study. In each case after the beginning of general anesthesia with mechanical ventilation surgeons were asked to assess the mobility of the operative field and conditions for laser lithotripsy according to the developed questionnaire scale. The questionnaire consisted of 5 degrees of assessment of kidney mobility and each question was scored from 1 to 5, 1 being very mobile (extremely poor conditions for dusting) and 5 completely immobile (Ideal conditions for dusting). After this assessment modified technique of general anesthesia was applied called combined respiratory support which consisted of reduction of tidal volume to 250-300 ml and respiratory rate to 4-5 per minute with transcatheter high frequency jet ventilation through endotracheal tube with a respiratory cycle frequency of 300 per minute and maintained during retrograde intrarenal surgery. At the beginning of combined respiratory approach, surgeons were once again asked to assess the mobility of the operative field and the conditions for laser lithotripsy. Main ventilation parameters were recorded and compared in both regimens.

Inclusion Criteria:

• Kidneys stones with indications for retrograde intrarenal surgery

Exclusion Criteria:

• Patients with ASA class of greater than 3
• Patients with active urinary tract infection were excluded from the study