# US 5,331,967 A · Tracheal intubation monitoring apparatus and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,331,967 A - Document ID: US5331967A - Status: Granted - Kind: A - Application number: 08/015,405 - Filed: 1993-02-05 - Granted: 1994-07-26 - Earliest claimed: 1993-02-05 - Assignees: Playa de los Vivos S.A. - Inventors: Steve H. Akerson - Web page: https://patentgrep.com/patent/US5331967A ## CPC - G01F 23/2966: {making use of acoustical resonance or standing waves} - A61M 16/04: Tracheal tubes (catheters in general A61M25/00) - A61M 16/0411: {with means for differentiating between oesophageal and tracheal intubation} - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} ## Abstract A method and apparatus for monitoring and indicating whether a tracheal tube is located in the trachea or esophagus during an endotracheal intubation of a human or animal is disclosed. In a calibration mode, the resonant frequency of the tube is determined by generating a signal at a plurality of frequencies and finding the signal which propagates with the greatest amplitude. This :indicates the resonant frequency. When the tube is inserted into the patient, the resonant frequency of the system shifts, thus the amplitude of the signal changes. Based on known characteristics of the trachea and esophagus, the amount of change is dictated by whether the tube has been inserted into the trachea or esophagus. Alternatively, the device can continually determine the resonant frequency and use this to monitor the level of liquid in a tank. ## Claims ### Claim 1 A monitoring apparatus comprising: a tube and means for determining a position of the tube in a patient having; signal generator means for generating a plurality of signals, each signal having a predetermined frequency, wherein said signal generator means is operatively connected to said tube so that said plurality of signals are propagated into said tube; signal amplitude determining means for individually determining a signal amplitude for each of said plurality of signals; resonant frequency determining means responsive to said signal amplitude determining means for determining a resonant frequency of said tube: first memory means for storing the determined resonant frequency; and second memory means for storing a signal amplitude associated with said resonant frequency. ### Claim 2 (depends on 1) The monitoring apparatus of claim 1 wherein: said signal generator means continuously produces a measuring signal having a frequency substantially equal to said resonant frequency and said amplitude determining means determines a signal amplitude associated with said measuring signal, said monitoring apparatus further comprising: comparator means for comparing the signal amplitude associated with said measuring signal with a stored signal amplitude associated with said determined resonant frequency; and indicator means responsive to said comparator means for indicating a result of a comparison made by said comparator means. ### Claim 3 (depends on 2) The monitoring apparatus of claim 2 wherein said comparator means comprises: means for digitizing the signal amplitude associated with said measuring signal; digital comparator means for comparing the signal amplitude associated with said measuring signal and said stored signal amplitude associated with said resonant frequency; and wherein said indicator means comprises a digital display. ### Claim 4 (depends on 3) The monitoring apparatus of claim 3 wherein said comparator means compares the signal amplitude associated with said measuring signal by measuring a phase angle where said measuring signal crosses a preset threshold. ### Claim 5 (depends on 4) The monitoring apparatus of claim 4 wherein said indicator means comprises a multicolored light display that changes color when the phase angle is past a preset amount. ### Claim 6 (depends on 4) The monitoring apparatus of claim 4 wherein said digital display comprises means for displaying the phase angle. ### Claim 7 (depends on 1) The monitoring apparatus of claim 1 wherein said signal generator means comprises a sine wave generator. ### Claim 8 (depends on 1) The monitoring apparatus of claim 1 wherein said first memory means initially stores an initial resonant frequency and said monitoring apparatus further comprises: means for continually determining a new resonant frequency; and means for comparing said initial resonant frequency and new resonant frequency and displaying a difference between said resonant frequencies.