Endoscopic system with integrated patient respiratory status indicator

[0001] The present invention relates to an endoscopic system, and in particular, to an endoscopic system having integrated patient respiratory status monitoring capabilities.

[0002] Endoscopes have been used for many years in the medical field to look within a selected region of a patient's body, e.g., the colon or the upper gastrointestinal region. The endoscope is typically inserted through an orifice or a surgical incision into a body channel or cavity. Endoscopes are commonly used to perform surgical, therapeutic, diagnostic, or other medical procedures under direct visualization. Conventional endoscopes generally contain several endoscope components, such as fiber optic light guides, a fiber optic image guide, and a working channel. The endoscope can also be equipped with one or more instrument channels for surgical implements. These components are positioned within the lumen of an endoscope sheathing tube. Endoscopes may be rigid or flexible. Flexible endoscopes incorporate an elongated flexible shaft and may include an articulating distal tip to facilitate navigation through the internal curvature of a body cavity or channel. Examples of conventional endoscope designs are described in U.S. Pat. Nos. 4,706,656; 4,911,148; and 5,704,899.

[0003] In order to facilitate endoscopic procedures, patients often receive sedation. In recent years, fast acting sedation drugs, such as intravenous propofol, have been used in conjunction with endoscopic procedures. The use of sedation has required increased reliance on the use of monitoring devices to detect early signs of patient distress, such as heart rate, transcutaneous PCO₂, EKG and EEG for monitoring heart and brain functions, respectively, during surgery. The risk for patient respiratory distress, such as shock, is increased by any procedure that requires the use of a strong sedative, for example, in upper GI endoscopic procedures, such as endoscope retrograde cholangiopancreatography (“ERCP”), especially in frail patients.

[0004] While the conventional monitoring techniques work well for their intended use, they are not well suited for monitoring respiratory distress during various endoscopic procedures. One means of monitoring the respiratory status of a patient undergoing an endoscopic procedure is by measuring and charting the concentration of CO₂ in the patient's expired air, during the end-tidal phase (ETCO₂) of the respiratory cycle, in a procedure known as capnography. The capnographic unit is typically attached to a mask fitted over the patient's airway. However, a more sensitive means for measuring expired CO₂ is needed to provide early detection of patient respiratory distress during endoscopy.

[0005] To address the above-mentioned concerns and others, the present invention is an endoscopic system having an endoscopic probe routable through passageways of a surgical subject, the endoscopic probe having a proximal end and a distal end; and a capnographic sensor capable of generating signals indicative of CO₂ gas concentration during endoscopic use. In one embodiment, the capnographic sensor is positioned adjacent the distal end of the endoscopic probe. In another embodiment, the capnographic sensor is positioned between the proximal and distal end of the endoscopic probe. In yet another embodiment, the capnographic sensor is associated with a mouthpiece to be placed within the mouth or airway of the surgical subject. The capnographic sensor analyzes expired air from the subject, generates signals indicative of patient respiratory status, and outputs the generated signals to an output device, such as a control console, which synchronizes the CO₂ signals with the respiratory phase to determine the ETCO₂ of the patient

[0013] Embodiments of the present invention will now be described with reference to the accompanying drawings where like numerals correspond to like elements. Embodiments of the present invention are directed to systems of the type broadly applicable to numerous medical applications in which it is desirable to insert a steerable or non-steerable imaging device, catheter or similar device into a body lumen or passageway. The following description provides examples of medical systems that include an endoscopic probe, a capnographic device, and a control console for use in medical procedures.

[0014] Several embodiments of the present invention include medical devices that incorporate endoscopic features, such as illumination and visualization capabilities, for endoscopically viewing anatomical structures within the body. As such, embodiments of the present invention can be used for a variety of different diagnostic and interventional procedures, including upper endoscopy, endoscope retrograde cholangiopancreatography (“ERCP”), bronchoscopy, thoracoscopy, colonoscopy, laparoscopy, ureteroscopy, hysteroscopy and video endoscopy, etc. The various embodiments of the present invention described herein may be used with both reusable and low cost, disposable endoscopes, such as an endoscope that is sufficiently inexpensive to manufacture such that it can be a single-use device as described in U.S. patent application Ser. No. 10/811,781, filed Mar. 29, 2004, and No. 10/956,007, filed Sep. 30, 2004, commonly assigned to Scimed Life Systems, Inc., now Boston Scientific Scimed, Inc.

[0015] Although exemplary embodiments of the present invention will be described hereinafter with reference to endoscopes, it will be appreciated that aspects of the present invention have wide application, and may be suitable for use with other medical devices, such as catheters (e.g., guide catheters, electrode catheters, etc.), and medical procedures where capnographic functionality may be desirable. Accordingly, the following descriptions and illustrations herein should be considered illustrative in nature, and thus, not limiting the scope of the present invention, as claimed.

[0016] FIGS. 1 and 3 illustrate one embodiment of an exemplary endoscopic system, generally designated 10, formed in accordance with aspects of the present invention. The system 10 includes an endoscopic probe 20 and an expired air sampling device 24 (see FIG. 3) functionally connected to a control console 28. In one embodiment, the expired air sampling device 24 includes a capnographic sensor, as will be described in more detail below.

[0017] In use, the endoscopic probe 20 is routed through a body lumen of a patient to visualize a selected region of a patient's body. As the endoscopic probe 20 is routed through the body lumens, the expired air sampling device 24 collects expired air from the patient and generates signals indicative of patient respiratory status and outputs the generated signals to the control console 28. A patient respiration phase sensor 196 generates signals indicative of the phase of the patient's respiratory cycle. The respiration phase sensor 196 may be any type of sensor capable of detecting the respiration phase of the patient, such as, for example, a sensor such as a flow or pressure meter that measures the ventilated volume of gas or pressure from the patient, or a trans-thoracic impedance detector, or a strain gauge that measures chest movement. The control console 28, which includes system circuitry and application software, processes the signals received by the expired air sampling device 24 and the respiration phase sensor 196 in order to estimate the end-tidal CO₂ levels. The measured end-tidal CO₂ levels are monitored and compared to preset parameters in order to detect changes in the respiratory status of the patient. If the respiratory status of the patient changes based on the processed signals of the expired air sampling device 24, the control console 28 may output an audible or visual alert signal. Such alert signals may be useful to assure normal respiratory functioning of the patient under sedation.

[0018] Referring now to FIGS. 1 and 2, the components of the system will be described in more detail. The endoscopic probe 20 can be any flexible, partially-flexible, or rigid elongated probe containing one or more lumens for the purpose of providing endoscopic procedures, and for the purpose of facilitating the insertion and extraction of fluids, gases, and/or medical devices into and out of the body. The endoscopic probe 20 may contain an imaging system of the optical type in which an optical image is carried on a coherent fiber optic bundle, or the video type, in which a miniature camera, which includes a charge coupled device (CCD) or CMOS imaging sensor, is disposed at the distal end of the endoscopic probe 20. In some embodiments, the endoscopic probe 20 is designed for a single-use and is disposable.

[0019] In one embodiment, the endoscopic probe 20 includes a flexible elongated insertion tube 34 having an articulation section 38 disposed at its distal region, and a distal tip 42. The distal tip 42 of the endoscopic probe 20 includes a digital imaging system (not shown) composed of, in one example, a CMOS image sensor, plastic optics, and LED illumination. The endoscopic probe 20 further includes one or more lumens for the purpose of providing endoscopic procedures, and for the purpose of facilitating the insertion and extraction of fluids, gases, and/or medical devices into and out of the body. For example, the lumens may include a working channel 50, irrigation and/or insufflation lumen 54, and an optional suction lumen (not shown), as best shown in the cross sectional view of FIG. 2. In one embodiment, as will be described in detail below, the working channel 50 also functions as the suction lumen.

[0020] The endoscopic probe 20 also includes electrical cables 56 and 58 for supplying power to illumination LEDs and to transmit images back to the control console, respectively. Alternatively, fiber optic cables may be provided for sending and transmitting the same. Each lumen, fiber optic cable, an/or electrical cable extends from the distal tip of the endoscopic probe 20 to the control handle. Finally, in the embodiment shown, the endoscopic probe 20 includes at least one pair of control wires 60A-60B, and preferably, two pairs of control wires 60A-60B and 62A-62B, that are connected at the distal tip and terminate through the proximal end of the insertion tube 34.

[0021] Returning to FIG. 1, the proximal end of the insertion tube 34 enters the control handle 26, from which a communications conduit 80 emanates. The control handle 26 may include steering controls 64, such as one or more knobs, for selectively applying tension on the control wires to steer the distal tip 42 of the endoscopic probe. The control handle 26 may also include a biopsy port 66 for accessing of the lumens, such as the working channel, of the endoscopic probe. The communications conduit 80 functionally interconnects the control handle 26 to the control console 28. The communication conduit 80 carries image information back to imaging electronics housed in the control console 28 from, for example, the imaging sensor. Video related signals are exchanged between the control console 28 and the imaging sensor via electrical cable 58 passing through the insertion tube 34 and the communications conduit 80. As will be described in detail below, video data provided to the control console 28 by the imaging sensor may be placed in a suitable format for viewing and are transmitted to a display for viewing by the examining physician.

[0022] The communications conduit 80 also carries power for illumination LEDs forward from the control console 28 to the endoscopic probe 20, as well as optionally carrying irrigation/insufflation fluids forward through the insertion tube 34 to the distal tip of the endoscopic probe 20. In one embodiment, vacuum pressure is provided to the working channel through the communications connector 80. In one embodiment, the communications conduit 80 further carries expired gas (CO₂) concentration signals from the endoscopic probe to the control console 28. As will be described in detail below, expired gas signals provided to the control console 28 by the endoscopic probe may be processed in a suitable manner for viewing and are transmitted to a display for monitoring by an examining physician.

[0023] Each of the lumens as well as electrical cables that transmit control signals and, for example, expired gas concentration signals terminate at the proximal end of the communications conduit 80 in a communications terminal. The terminal is configured to be cooperatively connected to a control console terminal for establishing functional connection between the endoscopic probe 20 and the control console 28. As will be described in detail below, appropriate passageways, electrical cables, and the like interconnect the control console terminal to the respective components housed in the control console 28.

[0024] FIG. 3 is a block diagram of the system 10, including one exemplary embodiment of the control console 28. The control console 28 is preferably mounted on wheels so that it can easily be placed near a patient prior to an examination procedure. The control console 28 is connected to a source of electrical power, either AC mains or a battery, and optionally connected to a plurality of utilities 100, including, for example, an irrigant 102, a solution of additives 104, a supply of aeration 106, and a source of vacuum 108. The control console 28 further includes a suite of application software 124. The application software 124 includes a graphical user interface (GUI) software application 126, a system control software application 128, and a network software application 134. In addition, the control console 28 includes an optional manifold 148 for use with the utilities 100 for supplying fluids/gas to the endoscopic probe, a series of system electronics 154, an imaging electronics board 158, a capnographic electronics board 160, and a network connection 162. The network connection 162 may include, for example, a local area network or an Internet connection.

[0025] The suite of application software 124 resides on a computer readable memory storage medium 170, such as a hard disc drive, a solid state memory or other non-volatile memory, located in or associated with the control console 28, and may run on standard or custom operating systems and may be processed with processors used in personal computer environments. The GUI software application 126 is well known to those skilled in the art, and provides the physician or operator with live endoscopic video images and CO₂ concentration data, such as ETCO₂ values on display 176.

[0026] The system control software application 128 is the central control program of application software 124 that receives input from optional sensors 120, the user interface 166, the control handle 26, a respiration phase sensor 196, and the expired air sampling device 24 having a capnographic sensor via the system electronics 154, and provides system software control for a majority of features and functions necessary to operate and monitor the endoscopic system 10. Sensors 120 may include, for example, pressure transmitters and temperature sensors, and are used for real-time electronic feedback of hardware operating parameters such as pressure and temperature. The network software application 134 enables the operation of network connection 162 and is representative of the hardware and software required for local area network connection and connection to the World Wide Web.

[0027] The imaging electronics board 158 receives signals transmitted from an imaging sensor (not shown) and its associated electronics at the distal end of the endoscopic probe 20. Imaging electronics board 158 is electronically connected to system electronics 154. The application software 124 provides commands to the imaging electronics board 158 via the system electronics 154. The imaging electronics board 158 can enhance the images received or can provide video effects such as zoom, color changes, highlighting, etc., prior to display of the images on a display 176. The display 176 may be formed integrally with the control console or provided as an external monitor. Images produced by the imaging electronics board 158 may also be printed on a digital printer, sent to a network server to be, for example, archived, saved to a removable storage media 178, such as a floppy disc, CD, DVD, etc., or a video tape for later retrieval and analysis by a physician.

[0028] The imaging electronics board 158 also provides electrical power to a light source, such as a number of light emitting diodes (LEDs), at the distal end of the imaging endoscopic probe 20. Alternatively, if the endoscopic probe 20 utilizes an external light source, then the control console 28 can include a light intensity light source, such as a laser or arc lamp source, that supplies light to a fiber optic illumination guide within the imaging endoscopic probe 20 in order to illuminate an internal body organ. As will be described in detail below, the supply of power may be controlled by signals received from the control handle when the user desires to activate the light source or adjust the intensity of light produced. In one embodiment of the invention, the imaging board 158 is provided on a standard PC circuit board to allow individual endoscopes to be tested with a personal computer and without the need for an additional control console.

[0029] The capnographic electronics board 160 receives signals transmitted from the capnographic sensor of the expired air sampling device 24 that is located, in one example, at the distal end region of the endoscopic probe. The capnographic electronics board 160 is electronically connected to the system electronics 154. The application software 124 may provide commands to the capnographic electronics board 160 via the system electronics 154. The capnographic electronics board 160 may include A/D and D/A converters and other associated conventional components, such as preamplifiers, amplifiers, buffers, signal processors, comparators, conditioners, etc, in a conventional configuration for processing signals received from the capnographic sensor and an associated respiration phase sensor 196 and for outputting capnographic signals in a suitable format to be displayed as a capnogram on the display. The capnographic electronics board 160 contains software algorithms for estimating the ETCO₂ levels based on a correlation between the input signals from the expired air sampling device 24 and the input signal of the respiration phase sensor 196.

[0030] The system 10 also includes an expired air sampling device 24 functionally connected to the control console 28, as best shown in FIG. 3. The expired air sampling device 24 receives a quantity of expired air from the patient during the endoscopic medical procedure. Referring now to FIG. 4, there is shown one exemplary embodiment of the expired air sampling device 24. The expired air sampling device 24 includes a capnographic sensor 72 that analyzes the expired air in real-time for CO₂ content or concentration, and generates an electronic output signal corresponding to the instantaneous concentration levels of CO₂ present in the expired air. The expired air sampling device 24 preferably uses infrared spectroscopy analysis to generate the electronic output signals. However, other CO₂ analysis techniques, such as Raman or photoacoustic spectroscopy, may be practiced with the present invention. As will be explained in more detail below, the electronic output signals generated by the capnographic sensor 72 are transmitted to the control console 28, where the electronic output signals are processed by the capnographic electronics board 160 and displayed as a capnogram on the display 176.

[0031] In one embodiment shown schematically in FIG. 4, the capnographic sensor 72 may be configured as a cuvette that defines a sample chamber 74 through which expired air from the patient passes. A light port 76 and a detector port 78 are formed on opposite sides of the sample chamber 74. The light port 76 and the detector port 78 define an optical path of predetermined length across the sample chamber 74 for the optical detection of carbon dioxide flowing therethrough. An infrared light source 80 is provided and positioned such that infrared emitted by the infrared light source is transmitted through the light port 76 and along the optical path between the light port 76 and the detector port 78. Positioned at the end of the optical path through the detector port 78 is a photo detector 82. The photo detector 82 detects the infrared energy as it passes through the gas and the sample chamber 74, and generates electrical output signals representative thereof. As will be explained in more detail below, these output signals are processed for indicating the concentration of the one or more specific gases located in the sample chamber 74. The infrared light source may be of the specific frequency type, generating infrared by the high frequency-high voltage excitation of CO₂ at low pressure in a sealed tube, or may be a black body source filtered by an appropriate filter to provide infrared at the CO₂ wavelength in a range between 4.3 and 4.35 microns.

[0032] The capnographic sensor 72 may also include an optional reference cell that addresses gain and drift. As best shown in FIG. 4, the reference device includes a reference emitter 84, such as a visible light emitter, and a visible light detector 88 similarly arranged as the infrared light source and photo detector described above. Alternatively, the capnographic sensor 72 may include other electrical and/or mechanical techniques to address drift and/or calibration. For example, the sensing device may include the electrical chopper circuitry as described in U.S. Pat. No. 5,445,160, or the mechanical chopper wheel of U.S. Pat. No. 4,423,739, respectively, both of which are incorporated by reference. The reference cell provides a reference value to which the CO₂ concentration signals from the infrared detector may be compared by the capnographic electronics board 160.

[0033] In several embodiments, the expired air sampling device 24 is attached to or integrated with the distal tip 42 of the endoscopic probe 20, as schematically shown in FIGS. 5 and 6, respectively. It will be appreciated that the expired air sampling device 24 may also be located along any portion of the probe shaft that is in communication with the airway of a patient when inserted. In another embodiment, the expired air sampling device 24 may be incorporated into a mouthpiece, as shown in FIG. 7.

[0034] As best shown in FIG. 7, the mouthpiece 200 has a tube 202 that is positioned in the patient's mouth to provide access into the patient's alimentary or bronchial canals. The tube 202 defines a lumen 204 through which the endoscopic probe 20 may inserted for various medical procedures. The mouthpiece 200 may include a curved tongue 206 that extends distally from the tube 202 and operates to aid the passage of a catheter or endoscopic probe 20 into the patient's esophagus or trachea. In some embodiments, the outer surface of the tube 202 may be covered with a foam or other compressible material to protect the patient's teeth as surgical devices are inserted into the patient. Alternatively, the tube 202 itself may be formed of a relatively soft material. A flange 208 is positioned at the proximal end of the tube 202 and has a diameter larger than the patient's mouth such that the mouthpiece 200 cannot be accidentally swallowed by the patient. The mouthpiece 200 further includes inlet and outlet ports for communication with the sampling chamber of the expired air sampling device 24. The expired gas device is functionally connected to the control console via any suitable transmission means (not shown in FIG. 7). In the embodiment shown in FIG. 7, the mouthpiece 200 is associated with a surgical mask 250 that is fitted over the mouth and nose of a patient 260.

[0035] One suitable method of using the endoscopic system 10 will now be described with reference to FIGS. 1-7. In use, the endoscopic probe 20 is routed through a body lumen of a patient to visualize a selected region of a patient's body. Prior to, during, and/or subsequent the endoscopic probe 20 being routed through the body lumens, the expired air sampling device 24 collects expired air from the patient, generates signals indicative of patient respiratory status, such as CO₂ concentration levels, and outputs the generated signals to the control console 28. In one embodiment, the device 24 is located in a mouthpiece 200, which is positioned within the mouth region of the patient. In other embodiments, the device 24 is located along the proximal shaft of the insertion tube 34 or in proximity of the distal tip 42 of the endoscopic probe. It will be appreciated that the placement of the device 24 may be selected based on various factors, such as the type of medical procedure to be performed.

[0036] The control console 28, which includes appropriately configured circuitry, such as the systems electronics 154 and capnographic electronics board 160, and application software 124, receives the signals from the device 24 and the associated respiration phase sensor 196, such as a chest impedance sensor that outputs signals indicative of patient breath cycles, and processes the received signals. The control console 28 processes the signals by sampling the CO₂ concentration signals received by the device 24 in synchrony with the respiration phase determined by the respiration phase sensor 196. The processed signals are then outputted to the display as a capnogram, plotting, for example, CO₂ concentration versus time. Other data may be displayed on the display, such as ETCO₂ numerical values or ETCO₂ plotted over time to indicate any trends during the procedure.

[0037] The information displayed on the display 176 allows the physician to monitor the respiratory status of the patient. If the respiratory status of the patient changes based on the processed signals of the expired air sampling device 24 such that, for example, the breath by breath ETCO₂ values exceed a predetermined threshold, the control console 28 may output an audible signal through the speaker 198, or a visual alert signal on the display 176. Such alert signals may be useful to assure normal respiratory functioning of the patient under sedation and/or to alert the physician to early indications of respiratory distress in the patient.

[0038] In one embodiment of the present invention, the endoscopic probe 20, control handle 26, and communications conduit 80 (hereinafter “the single-use endoscope”) may be used for single use application. Thus, upon completion of a patient examination procedure, the single use endoscope is disconnected from the control console 28 and disposed of. A new single-use endoscope is then connected to the control console 28 for the next examination procedure to be performed.

[0039] While exemplary embodiments of the present invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. It is therefore intended that the scope of the invention be determined from the following claims and equivalents thereof.