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The Flexible Bronchoscope: Which Hand Should Hold It?

2003; Raven Press; Volume: 10; Issue: 4 Linguagem: Inglês

10.1097/00128594-200310000-00018

1536-7959

Thomas R. Gildea, Atul C. Mehta,

Anatomy and Medical Technology

Cultural understanding of left-hand dominance has passed through the millennia as evidence of brain damage to demonic possession. Different cultures and traditions still regard the left hand as unclean. In the last several decades, left-handedness has been accepted and now only with some biases. The extent to which we are a right-handed society can be noted by paying very close attention to the objects we use everyday. Right now, I am typing this on a standard QWERTY keyboard with the mouse at my right hand. The scroll bar is on the right of my window, and when I fire my semiautomatic pistol, the shell casings are expelled away from my face out of the right side. (I actually do not even know how to shoot a gun, but the example is interesting.) Thus, it seems interesting that the “classic teaching” for bronchoscopy is that it should be held in the left hand. Why? Fortunately, we do not really grapple with this; there is no data supporting a specific technique and expert opinions are varied. There are no studies from other procedures to perform any systematic review so this Mehta-analysis will have to suffice. We have identified several areas of possible debate supporting the rationale for using the flexible bronchoscope (FB) in a specific hand (Table 1). The issues we conclude are related to design, tradition, bronchoscopist–patient anatomic ergonometry, advanced techniques, and motor learning. The following few paragraphs describe these arguments, and perhaps demonstrate that the FB might be poorly designed for the majority of bronchoscopists in the era of interventional bronchoscopy.TABLE 1: Issues of Hand Dominance in Interventional BronchoscopyDESIGN The design of the FB is left-handed. The umbilicus power cord and suction line is directed from the head of the scope out of the left side. When the FB is held in the left hand, the cords are out of the way of the right hand such that it has unobstructed access to the working channel (Fig. 1). It would seem that the tower should be placed behind and to the left of the bronchoscopist to give the maximal length of cord and that the cord does not cross-wrap around the head of the scope. The FB, of course, could be held in the right hand, but the cord seems to obstruct the path to the working channel. It is the understanding from at least one manufacturer's design engineer that the FB is intentionally configured to be held with the left hand.FIGURE 1.: (A and B) The bronchoscope held in the left hand allows the cord to be draped over the hand and the approach to the working channel is unobstructed (A). When the bronchoscope is held in the right hand, the cord can interfere (B).TRADITION Of course, we know that Dr. Ikeda was left-handed! The FB was made for the dominant hand of Dr. Ikeda. It is rational that Dr. Ikeda designed the FB to explore bronchial anatomy with more precision, and used his nondominant hand to brush or wash lung segments. It would also seem rational that his students would imitate the master by copying his technique rather than switch hands for ease of use. It is estimated that 90% of the Japanese bronchoscopists hold the FB in the left hand, as they have been taught, and because several of the world's manufactures and designers of the FB are based in Japan, there is little enthusiasm for change (personal communication). BRONCHOSCOPIST–PATIENT ANATOMIC ERGONOMETRY We created the previously mentioned phrase to classify arguments that state that the anatomy of the airways favor the left-handed technique. An a posteriori argument for the left-handed technique can be made in this realm. There can be difficulty with inspection of the right upper lobe posterior segment (B2) and the right lower lobe superior segment (B6) for right-handed bronchoscopists. This idea is supported in the condition when the patient is in the supine position and the bronchoscopist is standing at the head of the patient. In this position, when the FB is in the left hand, the wrist is maximally flexed and the tip is fully flexed with the thumb down. This is fairly comfortable compared with the same approach with the right hand (Fig. 2). While holding the scope in the right hand, full extension of the wrist may not comfortably allow visualization of the posterior segments as a result of the limited range (Fig. 3). The right hand must be flexed beyond comfort, and the right shoulder might need to be externally rotated or fingers extended to fully appreciate the right upper lobe (RUL) segments. Certainly, this could be uncomfortable when held for extended periods of time. The argument is only a problem in the current patient position, but it is not how it was done in the “old days.” When the patient is seated facing the bronchoscopist, the anatomic relationships were opposite favoring the right-handed technique. Another technique to overcome anatomic difficulty is to simply move your body position around the head of the patient, thus improving the approach angle to the RUL. We do not necessarily recommend this in our practice, but it is a logical solution for some. In any scenario, training and body position can overcome these inconveniences. We cannot make an argument that a similar problem exists for the left upper lobe (LUL) for left-handed bronchoscopists because the anatomy is not analogous.FIGURE 2.: Visualization of the right upper lobe posterior segment requires full flexion of the left wrist when held in the left hand.FIGURE 3.: When held in the right hand, visualization of the right upper lobe posterior segment can require extreme wrist extension. ADVANCED BRONCHOSCOPIC TECHNIQUES Because the modern world of FB only begins with inspection, the use of the working channel has become more important. The number and range of instruments that can be placed through the working channel expand to include a host of biopsy instruments, electrocautery surgical instruments, lasers, snares, cryotherapy, ultrasound probes, and so on. It would seem that a whole new range of technical skills would need to be acquired to master these instruments. This is partially true. For the above-average bronchoscopist, the theoretical aspects of procedure are more important than the technical aspects of their use. “When and in whom” continue to be the main issues with interventional bronchology. In fact, the technical side of using these instruments is the same “in and out” or “up and down” movement common to all the working channel instruments when it comes to the hands. Only when a foot pedal is needed is another extremity used. The technical skills are new to the way the FB is manipulated in the hand driving the scope. The rest of the instrument functions are manipulated in the third hand (ie, the hand of a well-trained assistant). The only exception to this generalization is the use of the working-channel hand during transbronchial needle aspiration. Several techniques are described to pass the needle through the bronchial wall (eg, cough, jab, straddle, and so on). 1 Even in this example, the only movement is in and out, and the variation is in anchoring of the needle in the channel to augment tensile force and velocity of the needle to pass through the airway wall. Despite all the innovations in working-channel FB technology, the only movement for the working-channel hand is to push in and remove the instrument. In looking at pictures in early textbooks of bronchoscopy, it would appear that the bronchoscope was held in the left hand so that the right hand would be free to perform the instillation of Lidocaine or close the forceps or pass the brush without any assistant. Dr. Kvale, and others of his fine vintage, might recall the lock on the old bronchoscope that could be used to fix the position of the angle of the tip so that the left hand would have some help not moving while the right hand did the work (Fig. 4). This feature is not present on modern bronchoscopes, and we are more readily dependent of the help of a well-trained assistant.FIGURE 4.: (A and B) Older models of the Olympus bronchoscope had a lever to “engage” or “free” the flexible tip of the scope. In the “engaged” setting, the flexible tip was locked in position.THE EVOLUTION OF RIGHT-HANDEDNESS AND NEUROMOTOR LEARNING The process of becoming adept at any procedure using fine motor skills is one that favors practice and the use of the dominant hand seems to expedite the practice time needed to acquire motor skills. Fine motor skills seem to be more rapidly acquired with the dominant hand. In fact, years of research ranging for neurology to anthropology have weighed in on the issue with very interesting insights. The Hand: How Its Use Shapes the Brain, Language and Human Culture by Frank R. Wilson is a book that outlines some of the evolutionary theories about hand development, not only to anatomic development, but also to hand dominance, which seems to be unique in Homo sapiens. The majority of this section paraphrases some of its contents. How people learn to be adept with any tool, from an evolutionary neurobiology standpoint, is remarkable. The interactions between visual and spatial mapping, fine motor control, timing, and coordination of all of the movements we make with oversight of the consequences of these actions are well beyond my understanding of the brain. Even the simple fact that we are mostly right-handed has led to some very interesting work. Evidence of handedness, described as “lateralized” function, has been evident as early as the Pleistocene epoch. Cro-Magnon man has traced mostly left hands in cave paintings, meaning that it was done with the right hand. 2 How this came to pass is still a mystery. The mystery is still generating hypotheses, not only why this lateralization occurred, but also how it exists in our ability to learn various motor tasks now. It would seem that some skills are more rapidly acquired on the “dominant side” than others, and some can be as easily learned on both. What has been shown, depending on the skill, is that the direction of the transfer of skills and the speed of transfer can vary depending on the nature of the skill and on what side it was originally learned. It has been shown that learning a task with the dominant hand can be transferred to the nondominant hand with ease, but the opposite might not be true. 3,4 It has been postulated that simple motor routines can be learned on the side that generally is used more often for similar tasks. In this way, the new task is recognized by the motor cortex as a variation and an already known theme of movement. Somehow, the left half of the brain communicates to the right half of the brain easier than the opposite in a right-handed person for some skills, but not necessarily through the corpus callosum as we might expect. 4 It is also of interest that not all skills are transferable in the same way. This can be demonstrated using baseball as an example. Swinging a baseball bat is generally performed with the dominant hand held toward the end of the bat where contact is made. Although a big league batter might disagree, as movements go, batting is a simple maneuver of generating speed in a rotational plane meeting the ball with the bat. Speed rather than precision is the dominant aspect of the movement. Pitching, however, requires a whole-body lateralization with shifting weight and precise timing of the hand release to be able to accurately deliver the ball. This difference was noted by a neurologist, Norman Geschwind, who said, “Switch hitters are more common than switch pitchers.”5 Precision timing, which is a dominant hemisphere task, is essential in some skills. Furthermore, we could explore the finer skills of writing and drawing using the small muscles of the hands. Among right-handers, writing and throwing are almost always done with the same hand. The reason for these differences to occur is that the basic control mechanisms could be different. The spatial and temporal scale of movement for the dominant hand is micrometric and the nondominant is macrometric, meaning that movement in the dominant hand tends to be lower in excursion and faster in repetition rates than those of the nondominant hand. Writing is clearly an example of hand dominance manifested in the recognition of the process and output of writing itself. The movement is generally a high-amplitude manipulation of a tool held in a precise grip in requiring rapid alteration of tonic and phasic contractions while moving the arm and wrist in a plane along a sheet of paper. This is the classic example of creating a micrometric movement stereotyping it and repeating it over and over. In another and interesting and intuitive example, writing has been linked or captured by the language center such that the movements are now programmed and part of the dominant hemisphere in most. The movement of the nondominant hand is not linked in such a way and still tends to be reactive and externally driven by circumstances of the dominant hand. The issue now becomes more complex when thinking about bimanual tasks like bronchoscopy or playing the violin. Guiard describes this as the division of labor in the way the right hand motion is built in the context relative to the left hand framing the area of movement. 6 The left hand holds the paper that the right hand draws on. The right hand rhythmically moves the bow across the strings and the left hand controls the lengths of the strings. You cannot argue which is more important to the performance because one cannot occur without the other. However, you can see how the skills of the one hand highlight the skills of the other. Oversimplifying these concepts, humans have evolved to favor a being that can learn and perform a great number of specialized, programmable tasks linked to the dominant hemisphere of the brain such that sequential processing and visual–spatial information is handled and often linked to learned complex micrometric motor routines. The dominant hand is good at learning rapid-sequence fine movements and the nondominant hand can learn these skills with time, but is better at manipulation in support of the dominant hand. There appears to be a neurologic basis of learning fine motor skills in a dominant hand, and that time to learn is also be part of motor learning favoring a dominant brain connection. Time to learn bronchoscopy has other implications. Because actual patients are used for training in most institutions and rarely are there enough patients or procedures for all trainees to acquire these skills in a typical training period, speed is essential. If learning new bronchoscopy skills is slow and the main reason is because of hand dominance, the bronchoscope is poorly designed for the majority of bronchoscopists. In summary, we believe that the FB should be held in the dominant hand, not only because Dr. Ikeda himself used the dominant hand, but because there is a basis for hand-dominant learning that favors the speed of skill acquisition for fine motor movements. Anatomic limitation of the right-handed technique can be overcome with position changes and still keep the scope in the dominant hand. Certainly, we do not suggest that the seasoned bronchoscopist should change hands now, particularly because we have shown data that it could be more difficult to transfer such tasks. Because there is a limited time to learn these skills for trainees, and the fact that actual patients are used even in the high-risk procedures, it simply does not make sense to disadvantage the learner for philosophic reasons. Because most of the world is right-hand-dominant, we believe that the basic FB design is not as good as it can be.