Patent Application
20160022943
The present invention generally relates to endotracheal tubes. More specifically, the present invention relates to a method and apparatus for more accurately determining the optimal endotracheal tube size for safe and effective intubation and airway maintenance of any individual patient requiring placement of an endotracheal tube.
When a patient is unable to breathe on his or her own due to a critical illness or injury, it becomes necessary for a clinician to place an endotracheal tube (also referred to herein as “ETT”) into that patient's trachea to facilitate the patient's breathing. Similarly, when a patient is unable to breathe independently because s/he is under general anesthesia for surgery, it becomes necessary for a clinician to place an endotracheal tube into that patient's trachea to sustain the patient's breathing.
When preparing to manage a patient's airway, it is important to determine the correct size endotracheal tube for any individual patient for several reasons. As discussed in greater detail below, two parameters are critical—tube diameter and tube length. Tube diameter is measured relative to the narrowest diameter of the upper airway, the cricoid ring. However, the glottic aperture, a triangular shaped opening to the trachea, is defined by the true vocal cords and arytenoid cartilage and is located just proximal to the cricoid ring. The glottic aperture can be measured and the diameter of the cricoid ring can then be calculated. Tube length is measured relative to the distance between the patient's vocal cords and the carina of the trachea (a cartilaginous ridge within the trachea that runs antero-posteriorly between the two primary brochi at the site of the tracheal bifurcation at the lower end of the trachea).
For purposes of reference, two oppositely disposed ends of a tube shall be referred to as the machine end and the patient end, the machine end being the end that remains outside a patient's mouth for connection to a ventilation source (i.e. bag valve mask or mechanical ventilator), and the patient end being the end that is placed into the trachea. Also, for purposes of reference, the trachea can be divided into three theoretical zones. Zone 1 will be referred to as the Upper Trachea—Unsafe Positioning Zone. It is 3.1 cm long and is made up of the 1 cm long cricoid ring immediately below the vocal cords and a 2.1 cm length of the trachea. Research shows that if the machine end of the endotracheal tube cuff (balloon) encroaches on this region, increased risk arises for recurrent laryngeal nerve impingement or pressure directly applied to the vocal cords, either of which may lead to an increased risk for vocal cord injury and paralysis. Encroachment on this region also leads to an increased risk for unplanned extubation. Zone 2 is the Lower Trachea—Unsafe Positioning Zone. It is 2.0 cm long and if the tip of the tube encroaches on this region, an increased risk for endobronchial mal-positioning and associated complications arises. Zone 3 is the Safe Positioning Zone and lies between Zones 1 and 2.
If an endotracheal tube having too large a diameter (relative to the patient's glottic aperture) is placed through the glottic aperture, the force applied to the vocal cords may cause a subluxation or dislocation of the crico-arytenoid joints leading to vocal cord dysfunction. Too small a diameter tube may lead to air leaks and inadequate ventilation of the patient. Similarly, if an endotracheal tube whose length from the tip of the tube at the patient end (T) to the machine end of the balloon or endotracheal tube cuff (BME) (illustrated as T-BME in
Both the outside diameter (OD) of the tube relative to the diameter of the glottic aperture and the (T-BME) length of the endotracheal tube relative to the length of the Safe Positioning Zone should be known when determining the size of endotracheal tube that will be used to intubate a patient to minimize complications of endotracheal intubation and airway maintenance. Historically, however, endotracheal tube sizes and identification nomenclatures have been based solely upon the interior diameter (ID) of the endotracheal tube. Although it is important for the physician to determine the correct endotracheal tube size for every individual patient, most clinicians responsible for the intubation determine endotracheal tube size based upon an educated guess, rather than upon scientific formula, algorithm or accurate measurement of any kind. Some practitioners will choose to place a 7.5 mm endotracheal tube for all females and an 8.0 mm endotracheal tube for all males. Some will choose a 7.0 mm tube for small adults, a 7.5 mm tube for medium size adults and an 8.0 mm tube for large adults. Others may just get a so-called “feel” for the “appropriate” size tube they think a person may need based on their physical characteristics such as height, weight and general size appearance. No generally accepted and widely utilized method, formula, or system exists that maximizes the probability of choosing the optimally-sized endotracheal tube for adults.
In contrast, certain formulas and methods exist that are generally accepted and used by clinicians to calculate the “proper” size tube for insertion into neonates, infants and children. One generally accepted formula based on the age of the child is given as (ETT Size=4+ age in years/4), and both weight-based and length-based systems are generally accepted and utilized to choose tube sizes in neonates, infants and children. However, even the weight and length-based systems that are considered the gold standard methods for choosing pediatric size tubes use indirect measures (weight/length) that do not correlate highly to nor predict well the tracheal length and glottic opening diameter and, thus, are not great predictors of optimal tube size.
As noted above, the size of an endotracheal tube is currently defined based on the inside diameter (I.D.) of the tube. Tube sizes range from a size 2.5 mm I.D. to a 10.5 mm I.D in 0.5 mm increments. However, endotracheal tubes with the same inside diameter (I.D.), have varying outside diameters (O.D.) depending upon the manufacturer and tube type. For instance, the Rusch 7.5 mm Standard ETT has an O.D. of 10.0 mm; the Mallinckrodt 7.5 mm Standard ETT has an O.D. of 10.2 mm; the Mallinckrodt 7.5 mm Hi-Lo Evac ETT has an O.D. of 11.2 mm; and the Teleflex 7.5 mm and the ISIS ETT each have an O.D. of 11.3 mm.
The International Organization for Standardization (ISO) requires that both the inside diameter (I.D.) and outside diameter (O.D.) be clearly marked on every endotracheal tube. Despite this reference to the outside diameter, most clinicians do not consider the outside diameter marking on the tube to determine the size of tube that will be utilized for any individual patient.
The ratio of the outside diameter of the endotracheal tube relative to the glottic aperture must be considered in order to minimize the risk for vocal cord injury. This ratio should be less than one. Preferably, the largest diameter endotracheal tube possible (which will minimize the “work of breathing”) should be used while not placing a tube so large that it causes significant pressure on the vocal cords or dislocation of the arytenoid cartilages (leading to vocal cord dysmobility). Ensuring that the diameter of the ETT is smaller than the diameter of the glottic aperture will decrease the risk of vocal cord paralysis from arytenoid cartilage dislocation and other complications as noted hereinabove.
Historically in determining tube size based upon the diameter of the tube, the assumption is made that if the appropriate diameter tube is chosen, the appropriate length of tube automatically follows. However, determination of optimal endotracheal tube size for any individual patient should be based upon considerations of both diameter and length. More specifically, the clinician should consider not only the outside diameter of the ETT relative to the size of the patient's glottic aperture, but also should consider the T-BME length relative to the VC-C length. The VC-C length is defined as the distance from a patient's vocal cords to the patient's tracheal carina. Every patient, based on his or her tracheal length, has a Safe Positioning Zone within the trachea, which defines the region within which both the endotracheal tube tip and balloon must be positioned.
In an attempt to protect patients from vocal cord injury from tubes whose T-BME length is too long, ISO Standard 5361-1999 dictates to manufacturers the maximum allowable distance (DMAX) from the tip of the patient end of an endotracheal tube to the machine end of the inflatable length of the tube's balloon. The ISO Standard DMAX for all size tubes is shown in Table 1. Because the maximum distance rather than the exact distance is defined in the ISO standard, this distance may vary for the same size tube from one manufacturer to another. The ISO Standard simply controls the T-BME length for a given diameter tube. However, even if the clinician chooses a tube having the correct diameter tube, the T-BME length may still be too long, despite ISO standards.
In order to assist clinicians in placing an endotracheal tube at the correct depth, many manufacturers place a depth localizer band or marker on their endotracheal tubes. The depth localizer bands indicate the position of the tube that should be placed at the level of the vocal cords. Although ISO standards permit depth localizer markers on endotracheal tubes to provide assistance in positioning the tracheal tube within the trachea, no specific standards exist for the placement of these bands on the tube body. Moreover, no standards exist for determining VC-T distances for different size (I.D.) tubes.
As shown in
Ensuring that both the tip of the tube and the entire balloon are within the Safe Positioning Zone of the trachea will minimize the risk of complications due to mal-positioning of the tube either at the time of placement of the tube or subsequently should any movement of the tube occur. If any of the T-BME complex is too deep, the patient is at increased risk for endobronchial intubation and any of its inherent complications including hypoventilation, hypoxemia, pneumonia, and pneumothorax. If the T-BME complex is too shallow, the patient is at increased risk for the inflatable balloon impinging on the recurrent laryngeal nerve and/or vocal cords and the inherent complications of vocal cord paralysis. In addition, if the T-BME complex is too shallow, the patient is at increased risk for unplanned extubation and its inherent potentially deadly complications including vocal cord injury/paralysis, aspiration pneumonia, hypoxemia, brain injury and death.
The length of the trachea, from the upper end at the cricoid ring to the lower end at the carina varies in adults from approximately 10 cm to 15 cm with the average adult trachea measuring approximately 12.5 cm.
As shown in
In view of the foregoing, it will be apparent to those skilled in the art from this disclosure that a need exists for an improved method and apparatus for determining the optimal endotracheal tube size for safe intubation of a patient to minimize the risk for mal-positioning of the endotracheal tube and the complications associated therewith and that the optimal tube size must be based upon both tube diameter relative to the narrowest portion of the upper airway and length from the tip to the machine end of the balloon relative to the length of the patients trachea and Safe Position Zone. Moreover, a need exists for a method and device that accurately determines the limiting diameter of the patient's upper airway (cricoid ring/glottic aperture) as well as the length of the patient's trachea.
In order to achieve the above-mentioned objectives and other objects of the present invention, a method and an apparatus are provided to determine optimal endotracheal tube size based upon both an optimal tube length and optimal tube diameter for any individual patient requiring intubation therewith.
The above method and apparatus utilize a measurement device to determine the smallest diameter of a patient's airway by measuring the glottic aperture and then algorithmically determining the limiting diameter of the airway in order to determine the optimal outer diameter of the tube for any individual patient.
In one embodiment of the present invention, a measurement device may utilize indirect methods for determining the glottic aperture such as optical scanning, ultrasound, or any other indirect methods to measure the limiting diameter of the upper airway. The device may scan the glottic aperture and thereby determine the diameter of the opening of the glottis. The device may also scan the cricoid arch and measure the subglottic transverse diameter
In an embodiment, the measurement device may also utilize methods to directly measure the glottic aperture such as a ring mandrel-type device directly deployed into the glottic aperture and cricoid arch.
In another embodiment, in addition to determining optimal tube diameter, a method and apparatus are provided which utilize a measuring device to determine the length of a patient's trachea and then algorithmically determine the optimal tube length for any individual patient. The measurement device employs indirect methods for determining the tracheal length such as ultrasound or other scanning devices. It may utilize associated external anatomical measurements to algorithmically determine the tracheal length, and it may employ direct measurement techniques that deploy a measuring tube directly into the trachea to determine the length thereof in a particular patient.
In an embodiment, an algorithm may be used with a machine, a processor or a computer to determine optimal endotracheal tube size by combining input data from demographics, by way of example, age, height, weight, and/or other anatomical measures, glottic diameter scan, subglottic transverse diameter scan and tracheal length scan.
In yet another embodiment, an apparatus is provided that includes a maneuverable arm, a fiber optic video guidance system and an introducer guide to maneuver an end of the apparatus around obstructions in a patient with a difficult airway to facilitate insertion of either an optimally sized ETT or a standard ETT into the patient's airway.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings, figures and tables and by reference to the appended claims.
Referring now to the attached drawings which form a part of this original disclosure:
Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Referring now to
In accordance with current practice, the size of an endotracheal tube is defined based on the inside diameter (I.D.) of the tube. Tube sizes range from a size 2.5 mm I.D. to a 10.5 mm I.D in 0.5 mm increments, and The International Organization for Standardization (ISO) requires that both the inside diameter (I.D.) and outside diameter (O.D.) be clearly marked on every endotracheal tube. In the ETT shown in
As discussed above, the SPZ 46 places the tip (patient end of the tube) 18 at least 2 cm above the carina 40 to minimize the risk of endobronchial positioning of the tube, should the tube move either due to inadequate stabilization or due to flexion/extension of the patient's neck. Similarly, the SPZ 46 places the machine end of the balloon at least 2 cm below the typical level of the recurrent laryngeal nerve and vocal cords to minimize the risk of both vocal cord injury and unplanned extubation.
Ensuring that both the tip of the tube and the entire balloon are within the Safe Positioning Zone 46, within the trachea 30, will minimize the risk of complications due to endobronchial intubation, unplanned extubation and impingement on the vocal cords 42 and recurrent laryngeal nerve lying near the cricoid ring 44. If the tip of the tube is too deep, the patient is at increased risk for endobronchial intubation and the inherent complications of endobronchial intubation including hypoventilation, hypoxemia, pneumonia, and pneumothorax (a collapsed or partially collapsed lung). If the tip of the tube is too shallow, the patient is at increased risk of the ETT balloon impinging the vocal cords or recurrent laryngeal nerve leading injury, vocal cord dysmobility, speech abnormalities and vocal cord paralysis. If the tip of the tube is too shallow, the patient is at increased risk for unplanned extubation and the inherent complications of unplanned extubation including vocal cord paralysis, aspiration pneumonia, hypoxemia, brain injury and death.
Referring now to
Referring now to
The apparatus 60 includes various attachments and devices which will be discussed in greater detail below to perform the following functions to carry out the steps of the novel methods of the present invention to ensure that an ETT of both the proper diameter and length is selected for safe intubation of any patient:
Referring to
The housing includes a carrying handle 64 secured thereto for ease of transporting the apparatus for field use by aeromedical flight teams and field paramedics. Various scan, test and control dials, selection buttons, input and output connection ports, and readout screens as known in the medical instrumentation art are illustrated generally at 66. The apparatus 60 includes, by way of illustration and not of limitation, an optical and/or ultrasound scanning device as part of a hand-held intubating video laryngoscope, shown generally at 68, for generating indirect images for measurement of the glottic aperture during intubation. By way of example and not of limitation,
Directing the reader's attention now to
To measure the tracheal length directly, an introducer 80 may be inserted via the hand-held intubating video laryngoscope 68 having a video laryngoscope tip or end portion 85 placed during the intubation process that directly measures tracheal length, as best shown in
Referring now to
As shown in greater detail in
In another embodiment, a second fiber optic bundle 101 can be mounted on the curvilinear blade 96 and attached to the video monitor through cable 105 to allow for continuous viewing of the movement of the flexible intubation arm 98 relative to its position in the oral pharynx and vocal cords. The secondary fiber optic video will allow for continued viewing of the vocal cords/intubation arm/introducer even when the primary fiber optic bundle 104 is deployed into the trachea.
In addition, the apparatus 90 of the present invention addresses a problem associated with current intubation devices/methods. Specifically, once the vocal cords are exposed with a video laryngoscope, the endotracheal tube must then be maneuvered separately around the same obstructions with a clinician's right hand while the view of the cords is maintained in the video laryngoscope with the clinician's left hand. The difficult airway intubator 90 herein disclosed solves that problem by incorporating a detachable sterile cartridge 106 having an introducer 80 stored therein and being selectively extendable via controls 94 through handle portion 92 and curvilinear section 96 into the longitudinally extended core 99 of the intubation arm 98, thereby allowing for manual deployment of an introducer 80 through the tip 103 of the intubator and into the trachea 50, once the tip is aligned with the glottic aperture. Once the introducer 80 is deployed into the trachea 50 it can be used to guide the endotracheal tube 10 around any obstructions, through the vocal cords and into the trachea. The secondary fiberoptic 101 can be used to view the endotracheal tube passing through the cords and into the trachea. The introducer may also be adapted to deliver oxygen to the patient via a separate tube 109 within the core of the introducer. As the patient is being intubated, oxygen is continuously delivered through the core of the introducer.
In operation, the difficult airway intubator 90 would be introduced into a patient's oral cavity 110 as shown in
In another embodiment, once the introducer is positioned as shown in
In understanding the scope of the present invention, the term “configured” as used herein to describe a component, section or part of a device that is constructed to carry out the desired function. In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including,” “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Finally, terms of degree such as “substantially,” “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
This application claims priority to U.S. Provisional Patent Application No. 62/000,182 filed May 19, 2014, the entire disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62000182 | May 2014 | US |
