A system comprising: a sound generator to emit sound waves into an endotracheal tube ("ETT", 102); at least one sound receiver to detect returning acoustic reflections; a reflectometry device having at least one processor and a memory that is accessible to the processor for analyzing timings and amplitudes of the returning acoustic reflections to determine a location and size of ETT obstructions; and a ventilation device in communication with the ETT and the reflectometry device; wherein the reflectometry device is arranged to estimate a pressure drop across the ETT when a patient spontaneously breathes; the ventilation device having a pressure and flow sensor in an airway circuit, wherein the reflectometry device is configured to determine a pressure within the trachea based on an algorithm that implements an equation generally of the form: P TRACHEA = P AW - R TUBE x Flow, where P TRACHEA = tracheal pressure, P AW = mean pressure at a Y-piece, R TUBE = resistance parameter, Flow = airway flow; and wherein the resistance parameter ("RTUBE") is representative of resistance to actual flow of air through the ETT and calculated using a function of a diameter of the ETT ("d ETT "), length of the ETT ("1"), and percent obstruction of the ETT ("Pct1"), wherein the percent obstruction of the ETT is representative of a reduced diameter of the ETT; and the reflectometry device, in response to the pressure drop, is arranged to automatically increase the pressure at a proximal end of the ETT to compensate for the pressure drop in an amount based on the algorithm. a sound generator to emit sound waves into an endotracheal tube ("ETT", 102); at least one sound receiver to detect returning acoustic reflections; a reflectometry device having at least one processor and a memory that is accessible to the processor for analyzing timings and amplitudes of the returning acoustic reflections to determine a location and size of ETT obstructions; and a ventilation device in communication with the ETT and the reflectometry device; wherein the reflectometry device is arranged to estimate a pressure drop across the ETT when a patient spontaneously breathes; the ventilation device having a pressure and flow sensor in an airway circuit, wherein the reflectometry device is configured to determine a pressure within the trachea based on an algorithm that implements an equation generally of the form: P TRACHEA = P AW - R TUBE x Flow, where P TRACHEA = tracheal pressure, P AW = mean pressure at a Y-piece, R TUBE = resistance parameter, Flow = airway flow; and wherein the resistance parameter ("RTUBE") is representative of resistance to actual flow of air through the ETT and calculated using a function of a diameter of the ETT ("d ETT "), length of the ETT ("1"), and percent obstruction of the ETT ("Pct1"), wherein the percent obstruction of the ETT is representative of a reduced diameter of the ETT; and the reflectometry device, in response to the pressure drop, is arranged to automatically increase the pressure at a proximal end of the ETT to compensate for the pressure drop in an amount based on the algorithm. P TRACHEA = P AW - R TUBE x Flow, where P TRACHEA = tracheal pressure, P AW = mean pressure at a Y-piece, R TUBE = resistance parameter, Flow = airway flow; and wherein the resistance parameter ("RTUBE") is representative of resistance to actual flow of air through the ETT and calculated using a function of a diameter of the ETT ("d ETT "), length of the ETT ("1"), and percent obstruction of the ETT ("Pct1"), wherein the percent obstruction of the ETT is representative of a reduced diameter of the ETT; and the reflectometry device, in response to the pressure drop, is arranged to automatically increase the pressure at a proximal end of the ETT to compensate for the pressure drop in an amount based on the algorithm.