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CATHETER GUIDE SYSTEM FOR MANAGEMENT OF DIFFICULT UPPER AIRWAY MANEUVERS
BACKGROUND OF THE INVENTION 5
1. Field of the Invention
The present invention relates generally to tracheal intubation, and more specifically to an airway catheter guide system for retrograde intubation.
2. State of the Art 10 Failure to maintain a patent airway for more than a
few minutes can result in brain damage or death. Tracheal intubation is an essential procedure for maintaining a patent airway in patients receiving general anaesthesia for certain kinds of operations, for assisting ventilation 15 in patients with ventilatory insufficiency, and to protect the lungs where protective reflexes of the larynx are inadequate. A categorized list of indications for this procedures is set forth as follows: Upper airway obstruction 20
Bilateral vocal cord paralysis 25 Airway control Epiglottitis
Surgical field adoidance during anaesthesia
General anaesthesia in other than supine position
Prolonged anaesthesia 30
Prevention of aspiration
Bulbar neuromuscular disease
Drug overdose 35
General anaesthesia for patient with full stomach
Genera] anaesthesia for parturient
General anaesthesia for prolonged surgical proce-
Inability to clear tracheobronchial secretions 40
Flail chest and lung contusion 45
Need for mechanical ventilation
Muscular relaxation for surgery
Central nervous system trauma
Anaesthesia for intrathoracic surgery There are numerous ways to intubate a trachea, the 55 choice of which depends on the preference of the anesthesiologist. For a patient with a normal airway, blind nasotracheal intubation in a spontaneously breathing awake patient has a good chance of success, yet the risk of causing upper airway bleeding may cause the anes- 60 thesiologist to turn to direct laryngoscopy. In any case, there are times when anesthesiologists are faced with management of difficult airway during intubation procedures.
Difficulty in intubation may be caused by one or 65 more of the following: congenital facial and upper airway deformities, maxillofacial and airway trauma, airway tumors and abscesses, anatomical deformities in the
nasopharyngeal or oropharyngeal region, the requirement for cervical spine immobility, fibrosis of the face and neck (bums or radiation), surgically induced deformities, and some systemic diseases. Attempts to push a endotracheal tube blindly through obstacles in the upper airway may result in excessive trauma and bleeding, possibly leading to severe glottic spasm or asphyxia. Bleeding prevents clear visualization of vocal cords, leading to further complication in the intubation process. Arthritis of temporomandibular joint or trismus limits the exposure of the patient's mouth, thus prevents the use of conventional direct laryngoscopy.
The management of the difficult airway may follow the algorithm shown in FIG. 1 of the drawings. Awake tracheal intubation is generally preferred. For an awake patient, the natural airway is better maintained and the muscle tone is enough to maintain the airway structure, which eases intubation.
Special techniques and instruments are required in managing the difficult airway. Since its first introduction in 1960, retrograde intubation, also referred as translaryngeal guided intubation, has been successfully used on patients with ankylosis of the jaw, cervical arthritis, tumors of the mouth and recently on patients with severe maxillofacial trauma. It is also an effective technique for securing the airway at an accident scene or in prehospital care of trauma patients, and for unexpectedly difficult intubation in operating theatres. The technique has a high success rate, is easy to learn and requires little practice. However, while apparatus for retrograde intubation is simple, it is not readily available in hospitals as there is no standardized equipment or procedure.
A planned retrograde intubation may be performed under local anaesthesia using light sedation and translaryngeal anaesthesia. A wide bore needle such as a 16 G Tuohy needle is used to puncture the cricothyroid membrane percutaneously towards cephalad (FIG. 2a). Air aspiration into a syringe filled with sterile water is used to confirm the position of the needle within the lumen of the larynx. Once the position is located, the syringe is removed and a guide (vascular guide wire or epidural catheter) is inserted through the needle (FIG. 2b) and threaded between the vocal cords into the pharynx. When an epidural catheter is used, it may coil up in the pharynx. The catheter may be spat out or retrieved from the patient's mouth by using Magill forceps (FIG. 2c). The needle is then withdrawn and the guide is secured at puncture site using a hemostat. For oral intubation, the endotracheal tube can be placed directly over the guide or a suction catheter can be passed over the original guide to provide a larger and stiffer guide for the tracheal tube (FIG. 2d). Once the top of the endotracheal tube reaches the cricothyroid membrane (FIG. 2e), the guide is released at the puncture site and is removed from above. The endotracheal tube is further advanced into the final position in the trachea (FIG. 2J).
If nasal intubation is intended, a soft plastic suction catheter is inserted through the nose into the pharynx and brought out through the mouth (FIG. 3). The tip of the retrograde catheter and the proximal end of the suction catheter are tied together with suture and the retrograde catheter is pulled back through the pharynx and out of the nose. In another approach employed by S. S. Dhara, one of the inventors of the present invention, a length is cut from the tip of the suction catheter and the epidural catheter is fed through the lumen of the
suction catheter until it protrudes from the nasal end. The suction catheter is then completely retrieved to bring the epidural catheter out from the nose. The tracheal tube is then inserted over the retrograde catheter and into the larynx. The rest of the procedure is 5 similar to that for orotracheal intubation.
Several variations of the apparatus and technique used in guided retrograde intubation have been employed in the prior art. These variations were designed and used to solve complications encountered during 10 retrograde intubation. However, such prior art apparatus and technique all possess one or more deficiencies.
A relatively large and stiff endotracheal tube threaded over a soft catheter guide or a thin flexible fibreoptic endoscope in fibreoptic aided intubation may 15 be diverted into the esophagus (FIG. 4), resulting in esophageal intubation. Long flexible tip retrograde guide wires such as the Seldinger type intravascular guide wire or teflon coated Swan-Ganz introducer wire provides better stiffness and control over an epidural 20 catheter. However, discrepancy between the outer diameter of the guide wire and the inner diameter of the endotracheal tube may cause the endotracheal tube to move round the guide, causing the endotracheal tube to hang up on the glottis (FIG. 5), epiglottis and arytenoid 25 cartilages.
Various techniques have been used for reproducible and successful guiding of the endotracheal tube into the trachea, including use of a stiffer retrograde guide, and by reduction of the discrepancy in diameters b enlarg- 30 ing the external diameter of the retrograde guide using an anterograde guide over it in a one-stop Seldinger type technique. Frozen suction catheter warmed-up plastic sheath stylet, cut gum elastic Eschmann stylet (FIG. 6), and fibreoptic bronchoscopes have been used. 35 The type of anterograde guide used currently depends very much on the convenience and availability of the devices, and preference of individual anesthesiologist.
All of the foregoing anterograde guides have to stop at the point of puncture at the cricothyroid membrane. 40 When the retrograde guide is completely withdrawn for further insertion of the endotracheal tube, the tube may dislodge from the laryngeal inlet, resulting in esophageal intubation. One of the modifications to prevent the dislodgement of endotracheal tube is to pass 45 the guide through the "Murphy eye" of the tracheal tube (FIG. 7) to allow for an additional 1 cm of the endotracheal tube within the trachea prior to removal of the guide. In another approach, a gum elastic bougie (FIG. 8) was inserted through the tracheal tube and 50 used as an anchor for further insertion of the tracheal tube. The disadvantage of this method is the inability to fit the gum elastic bougie through the tracheal tube and the anterograde catheter.
Breathholding and respiratory (inspiratory) obstruc- 55 tion may occur during the insertion of an epidural catheter and endotracheal tube. Sometimes, oxygen administration is necessary during intubation. Extra doses of topical local anaesthetic may be needed during the procedure to suppress the reflex arising from upper airway. 60 An anterograde guide which allows continuous ventilation, measurement of airway pressure and respiratory gases, and application of local anaesthetic without disrupting the insertion of endotracheal tube would be extremely useful in such situations. 65
To the inventors' knowledge, there is only one kit marketed for retrograde intubation (Cook, Australia). Cook's retrograde guide wire is rather thick and stiff.
The anterograde guide is a long, narrow single lumen tapered nylon tubing. The step or gradual tapering of the anterograde guide is a very important factor for guiding such as in intravascular catheterization where the Seldinger wire, dilator and sheath make a smooth cone. The discrepancy in diameters between the anterograde guide and the endotracheal tube leaves a large gap causing the endotracheal tube to be "caught" in the glottic inlet.
Little emphasis has been placed in the designing of an anterograde guide with regards to appropriate stiffness and diameter. The anterograde guide should be flexible enough to follow the retrograde guide along the curvatures of the upper airway. At the same time, it must have adequate stiffness for its primary function as an anterograde guide so as to avoid the endotracheal tube straying into the oesophagus.
Ventilation, monitoring of airway pressure or sampling of respiratory gases may be required during or immediately after the procedure of intubation. The "jet stylet" described by Bedger, et al. (1987) provides ventilation through a narrow long catheter which is inadequate for more than a few minutes. Measurement of airway pressure is very important while this mode of ventilation is employed, yet prior art apparatus makes no provision to facilitate such monitoring.
Administration of local anaesthetic into the upper respiratory tract during the procedure may be needed, yet again prior art devices do not readily accommodate such a requirement.
Anchoring of the anterograde catheter to prevent dislodgement of the endotracheal tube when the hold of the retrograde guide is being discontinued and the endotracheal tube is being negotiated through the laryngeal inlet is very important. However, there is currently no easily reproducible manoeuvre available to achieve this.
SUMMARY OF THE INVENTION
The airway catheter guide system of the present invention overcomes the above-enumerated deficiencies of prior art apparatus and procedures and provides an easily employed means and method for facilitating the management of difficult airways during retrograde intubation.
The catheter guide system of the present invention comprises a multilumen airway catheter and a cooperating adaptor which renders the catheter suitable for high frequency jet ventilation during intubation, with simultaneous measurement of airway pressure or respiratory gas sampling. The airway catheter is employed as an anterograde catheter in retrograde intubation procedures to guide the insertion of an endotracheal tube and prevent dislodgement from the larynx while the retrograde guide is withdrawn.
The catheter itself includes three separate channels or lumens, one large and two smaller ones. The large channel is of irregular cross section and extends the entire length of the catheter, and includes two lateral openings immediately adjacent the distal end or tip. The smaller channels are located in the wall of the catheter and extend from slightly different levels at the proximal end of the catheter and terminate on diametrically opposite sides of the catheter approximately 1.5 cm and 3 cm, respectively from the distal end.
The three channel openings at the proximal end of the catheter can be mutually isolated for purposes of jet ventilation by utilization of the airway adaptor of the present invention When placed on the proximal end of
the catheter, the airway adaptor includes three internal seals or O-rings to separate the annulus between the catheter and the adaptor into three chambers, each communicating with a catheter lumen and having a port extending through the wall of the adaptor. Each port 5 terminates in a luer lock fitting for connection to a ventilation gas source, monitoring device, or syringes to instill local anesthetic into the respiratory tract.
The tapered proximal end of the catheter provides an easily connectable and disconnectable resilient, fric- 10 tional interface with the adaptor via the O-rings. The tapered end also easily fits into the cut end of a 14 FG suction catheter if required to increase the effective length of the catheter used as a guide for an endotracheal tube during intubation. 15
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graphic depiction of an algorithm for management of a difficult airway;
FIGS. 2a-2/ schematically depicts the steps in a ret- 20 rograde intubation performed without the apparatus of the present invention;
FIG. 3 schematically depicts apparatus employed in a nasal intubation;
FIG. 4 schematically depicts the undesirable phe- 25 nomenon of esophageal intubation;
FIG. 5 schematically depicts the hang up of an endotracheal tube on the glottis;
FIG. 6 schematically depicts a prior art method guiding an endotracheal tube; 30
FIGS. 7 and 8 schematically depict prior art techniques for preventing dislodgement of the endotracheal tube;
FIG. 9 is an elevation of an airway catheter in accordance with the present invention; 35
FIG. 9a is a cross-sectional view of the interior of the catheter of FIG. 9 taken along lines A—A.
FIG. 10 is a schematic sectional view of the airway adaptor in accordance with the present invention applied to the proximal end of the airway catheter of FIG. 40 9.
DETAILED DESCRIPTION OF THE
Referring to FIGS. 9, 9a and 10 of the drawings, the 45 airway catheter guide system of the present invention comprises multilumen airway catheter 20 as depicted in FIG. 9, which may be employed alone or in combination with airway adaptor 100 in a retrograde intubation procedure. 50
Airway catheter 20 comprises a one-piece 35 cm long extrusion of a radiopaque elastomeric material such as medical grade polyvinyl chloride (PVC) having a Shore A durometer harness of 80-100, and a stiffness of 20-50 MPa as measured with a Tinius Olsen stiffness 55 tester. It is gradually tapered both at proximal end 22 and at distal end or tip 24, and is preferably graduated on its exterior as shown in FIG. 9 at 10, 15, 20 and 25 cm from distal end 24.
Catheter 20 defines a maximum external diameter of 60 4.75 mm, gradually tapering to 3.5 mm at both ends and includes three longitudinal channels or lumens 26, 28 and 30. As may be seen by reference to FIG. 9a, large central channel 26 is of irregular cross-sectional shape due to the presence of smaller side channels 28 and 30 65 which are formed in the wall 32 of catheter 20 as it is being extruded during the manufacturing process. The wall thickness between the central channel 26 and the
outer diameter of the catheter is 0.6-0.7 mm, and channels 28 and 30 are each of 1.2 mm interior diameter.
Large central channel 26 extends throughout the entire length of catheter 20 between outlets or apertures through proximal end 22 and distal end 24, and is intersected near (about 5 mm from) distal end 24 by 1 mm side exits or passages 31. Side channel 28 extends from an outlet or aperture 34 about 3.8 cm from the proximal end 22 of catheter 20 on its exterior surface 33 to an aperture 36 approximately 1.5 cm from the distal end or tip 24. Side channel 30 extends from an aperture 38 about 4.8 cm from proximal end 22 to an aperture 40 approximately 3.0 cm from the distal end or tip 24. Apertures 34, 36, 38 and 40 are of approximately 4 mm in width and are produced by removing wall material from the catheter to expose the underlying channel, the border of catheter material surrounding each aperture being generally scalloped in configuration. The apertures at each end of one of the two side channels are marked, such as by a dot on the catheter exterior, for ease of identification.
Referring to FIG. 10 in the drawings, airway adaptor 100 is shown placed over the proximal end 22 of catheter 20. Adaptor 100 includes a generally cylindrical clear plastic housing 102 comprised of clear acrylic or polycarbonate having a port 104 luer lock ventilation connector at one end and a barrel 106 in which are disposed three axially separated (by about 12 mm) rubber O-rings or seals 108,110,112. The interior diameter of barrel 106 is about 5.5 mm, and the inner diameter defined by O-rings 108-112 in an uncompressed state is about 4.5 mm. While not specifically shown in FIG. 10 due to its schematic nature, the wall of barrel 106 is sufficiently thick to accommodate annular grooves on the interior thereof in which O-rings 108, 110 and 112 are disposed and maintained after each is compressed and inserted into barrel 106, the expansion of each 0ring after insertion in barrel 106 ensuring proper seating in its corresponding groove.
When proximal end 22 of catheter 20 is inserted into barrel 106 of adaptor 100, O-rings 108,110 and 112 are compressed by the exterior 33 of catheter 20 and divide the annular space between the inner wall 114 of barrel 106 and the exterior surface 33 of catheter 20 into three chambers 116,118 and 120, each of which is in communication with a port extending through the wall of barrel 106. Port 122 opens into chamber 116, port 124 opens into chamber 118 and port 104 opens into chamber 120. Each port terminates at a luer lock fitting for easy connection to gas sources or monitoring equipment. Due to the previously noted spacing of apertures 34 and 38 from the proximal end 22 of catheter 20 and cooperative spacing of the O-rings 108-112 and ports 122 and 124, aperture (also termed side lumen) 34 opens into adaptor chamber 116 while aperture 38 opens into adaptor chamber 118. The proximal end of large channel 26 opens into chamber 120. Thus, when adaptor 100 is placed over the proximal end 22 of the catheter 20, a manifold is created which may be used to employ fluid sources (such as oxygen, air, anesthetic) and monitoring devices with airway catheter 20 during an intubation procedure.
It should also be noted that tapered proximal end 22 of catheter 20 also fits into the cut end of a suction catheter such as 14 FG PVC tubing to form a firm connection when needed to increase the length of catheter guide needed during intubation.