Change in upper airway related ultrasonographic parameters during percutaneous nephrolithotomy under prone position- A prospective observational cohort study

Surgery under prone position is often a necessity when accessing posterior anatomic structures like spine, retroperitoneum and upper urinary tracts. However, prone position is associated with position related oedema, visual loss, peripheral nerve palsies, pressure sores, cardiovascular compromise, compartment syndrome, oropharyngeal edema, macroglossia, sublingual hematoma which have to be assessed increasingly to be able to predict early and to have adequate prophylactic measures. Ultrasound is a quick, accessible and reliable tool which can be used in operating rooms and can visualize anatomical structures in the supraglottic, glottic and subglottic regions. There is sufficient evidence to advocate utility of airway ultrasound to predict difficult intubation, but literature on intraoperative change in these parameters is sparse. we hypothesize that change in upper airway during prone position may be reflected as significant change in upper airway related ultrasound parameters namely tongue thickness (TT), tongue volume (TV), skin to hyoid distance (SH), skin to thyrohyoid membrane distance (ST). It may help in predicting ease of extubation at the end of surgery and estimating the associated risk of postoperative airway related complications in patient undergoing surgery under prone position. We aim to investigate the intraoperative change in upper airway related ultrasonographic parameters in patients with unanticipated difficult airway, undergoing percutaneous nephrolithotomy under prone position.