(Chest. 2004;125:935-944.)
© 2004
American College of Chest Physicians
Anatomic Evaluation of Postural Bronchial Drainage of the Lung With Special Reference to Patients With Tracheal Intubation*
Which Combination of Postures Provides the Best Simplification?
Naoaki Takahashi, RPT;
Gen Murakami, MD, PhD;
Akira Ishikawa, RPT, PhD;
Toshio J. Sato, MD, PhD and
Toshikazu Ito, RPT
* From Hokkaido Chitose Institute of Rehabilitation Technology (Mr. Takahashi and Mr. Ito), Chitose; Department of Anatomy (Drs. Murakami and Sato), Sapporo Medical University School of Medicine, Sapporo; and Department of Physical Therapy (Dr. Ishikawa), Sapporo Medical University School of Health Science, Sapporo, Japan.
Correspondence to: Gen Murakami, MD, PhD, Department of Anatomy, Sapporo Medical University School of Medicine, South 1, West 17, Sapporo, 060-8556 Japan; e-mail: chisa{at}sapmed.ac.jp
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Abstract
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Background: Although several sequences of specific postures, each corresponding to a particular lung segment, have been recommended for therapeutic bronchial drainage, these are based on little or no anatomic evidence. Moreover, because these sequences are too complex, especially for intubated patients, they require simplification.
Materials and methods: The courses of the segmental bronchi B1, B2, B1 + 2, B3, and B6 and their subsegmental bronchi are extremely variable. This can result in a small branching angle at the subsegmental bronchial origin. Using 106 lungs, we measured the branching angles of the subsegmental bronchi and examined their running directions in each posture of the sequences recommended for bronchial drainage.
Results: A small branching angle (< 120°) at the subsegmental bronchial origin was sometimes evident, and this made postural drainage difficult. Drainage of B3 and B6 was often difficult because they formed angles of < 45° from the horizontal in certain postures (supine for B3 and prone for B6). Further, we found a 45° rotative prone position effective for draining B1a and B6.
Conclusion: Our anatomic findings predicted increased effectiveness in a sequence of postures: supine, 45° rotative prone with left side up, 45° rotative prone with right side up, and return to supine for simple, safe, and effective bronchial drainage, especially for patients with tracheal intubation. The 10° right-side-up supine and 45° rotative prone with head raised 45° positions seemed helpful if added to the basic sequence.
Key Words: anatomy • bronchial tree • postural bronchial drainage • rotative prone • supine
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Introduction
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Several sequences of specific postures, each corresponding to a particular lung segment, have been recommended for therapeutic bronchial drainage (Table 1
; Fig 1
, left, A through F).1
Miyagawa2
revised and rearranged these postures for patients with tracheal intubation, and recommended a sequence comprising the supine, prone, and 45° rotative prone with left-side-up and right-side-up positions (Table 1
; Fig 1
, right, G through I); this method has been generally accepted for intensive care patients in Japan, although it is not familiar in other countries. In addition to this sequence, inclusion of the prone position has been recommended to improve ventilation-perfusion relationships in the dorsal lung segments in patients with tracheal intubation.3
4
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Figure 1.. Recommended postures for segmental drainage from the upper lobe of the lung (corresponding to Table 1
). Left, A through F: Patient positions for postural drainage of S1, S2, S1 + 2, S3, and S6 as recommended by Potter and Perry.1
Right, G through I: Positions recommended for patients with tracheal intubation by Miyagawa.2
Potter and Perry1
described another 6 postures (ie, 12 postures in all) to cover all lung segments, while Miyagawa2
included another 5 postures (8 postures total). Left, A: Bending backward to drain S1. When bending backward or forward (see left, C), the craniocaudal axis of the lung is tilted at 45° from the horizontal. Left, B: 45° rotative prone with right-side-up position for draining the right S2. In this position, the craniocaudal axis of the lung is the same as in the prone or supine positions, but the coronal plane of the lung is tilted at 45°. Bending forward (left, C) is recommended for drainage of the posterior portion of the left and right upper lobes. Left, D: Supine position for draining S3. Left, E: Prone position for draining S6 and S10. Left, F: 45° rotative prone with head-raised position, which is recommended for S1 + 2 drainage in the left lung. "Head raised" means that the craniocaudal axis of the lung is raised to 30°. The supine position (right, G) is also useful for S3 drainage during tracheal intubation. It is also useful for S1 drainage during tracheal intubation. Right, H and I: 45° rotative prone positions with right and left sides up, respectively. These positions are recommended for S2 and S1 + 2 drainage during intubation.
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It is generally believed that the specific postures for segmental drainage were based on the locations of the segments and/or the courses of the segmental bronchi. However, as far as we can tell, the recommended postures seem to be based simply on the location of the segment and not on anatomic and clinical investigations as to whether a particular posture provides reliable drainage given the course or running direction of the bronchus. In contrast to research on how to provide effective bronchial distribution of inhaled medications5
6
and work on improving ventilation-perfusion relationships,7
8
few basic anatomic studies have been conducted with respect to postural drainage. Moreover, it is well known that the ramification patterns of the subsegmental bronchi vary widely, especially in the upper lobe.9
10
11
12
Postural drainage should facilitate the removal of excess secretions from the peripheral part of the lung.1
This "peripheral part" includes the subsegmental bronchi. However, we have found no information regarding the direction a particular subsegmental bronchus takes when a patient is placed in a specific drainage posture. Do the two or three subsegmental bronchi in a lung segment take a similar course to their mother segmental bronchus? It is likely that one of the subsegmental bronchi will take a recurrent or downward course, ie, at a negative so-called 
angle to the horizontal (Fig 2
), although physiotherapists try to ensure that the mother segmental bronchus is upright to facilitate smooth drainage.
Consequently, we aimed to investigate whether the running directions of the subsegmental bronchi allow effective drainage when a patient is placed in the recommended postures. In a preliminary study, we concentrated on dissections of S1, S2, S3, and S6 in the right lung, and S1 + 2, S3, and S6 in the left lung because, in these segments, we sometimes found that the subsegmental bronchi followed an almost horizontal course when the body was in the recommended postures (Fig 3
). We knew that anatomic evidence does not always connect to a good clinical result. But we wished to postulate an anatomically based sequence of postural bronchial drainage positions, especially for patients with tracheal intubation, because the usual method (see earlier) includes the prone position, which is sometimes very difficult to achieve.
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Figure 3.. Variations in the directions of the subsegmental bronchi in S1. The cadavers have been placed in the supine position for these anatomic representations. The left anterior thoracic wall, heart, and left lung have been removed. The right upper lobes are viewed from the left side after dissection. B1a and B1b run slightly upward in top, A, whereas in bottom, B, B1b is directed slightly upward but B1a runs downward. Thus, the supine position would give a poorer result for S1 drainage in the patient in bottom, B, than in the patient in top, A. PA = right pulmonary artery; PV = right inferior pulmonary vein; RPB = right principal bronchus.
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Materials and Methods
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From > 200 lungs prepared for our previous study,12
we selected 106 (54 right and 52 left lungs) according to three criteria: (1) clearly identifiable segmental bronchi in the upper lobe (conversely, we eliminated lungs with complicated ramifications such as B1b joining B2 on the right side); (2) absence of macroscopic pathology such as tumors (including tuberculosis), severe pneumonectasis, and adhesive pleuritis; and (3) ability to reconstruct the natural three-dimensional (superior-inferior, ventral-dorsal and left-right) lung structure. To achieve the third criterion, we had to preserve the covering thoracic wall and other surrounding structures in order to adjust the three axes of the lung. Thus, we frequently checked the natural shape of each specimen, including its dissected bronchi, by replacing it in the thoracic cavity of the cadaver from which it had been removed (Fig 3)
.
The 106 lung specimens were obtained from 75 cadavers that were donated for medical education and research and had been fixed by systemic arterial perfusion of 10% formalin solution. The ages at death ranged from 65 to 92 years. The lungs were usually fixed at their maximum expiratory point at death. Dissection was performed by the naked eye, usually starting from the mediastinal surface of the material. We measured and described the running directions of the segmental bronchi and the angle (Fig 2)
of each subsegmental bronchus with the lung in the supine or anatomic position. We also noted the branching angle or angle at which a subsegmental bronchus originated from the mother segmental bronchus. The upper lobar bronchi and those in S6 were measured in all specimens, while the bronchi in other segments were examined in approximately 10 specimens from either side. According to the data obtained for the supine position (Fig 3) , the running direction and angle were calculated for each postural variation (Fig 1)
. A "head-raised" posture was estimated to correspond to an additional 30° elevation from the basic posture. During the dissections and measurements, we were careful to maintain the natural topographic relationships between the bronchi, and between the bronchi and the costal surface of the lung, so as to reproduce the original bronchial anatomy of each cadaver.
In the present study, the terminology used to describe the bronchi is based on the Japanese classification system of lung segments, which is in turn based on the system of Jackson and Huber13
developed in the United States.13
The only difference between the Japanese system and the classification of Boyden10
is the numbering of B2 and B3; B3 in the classification of Boyden corresponds to B2 in the Japanese system.
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Results
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Running Directions of the Segmental Bronchi and Recommended Postures
Firstly, we examined the accepted concepts regarding the directions in which the segmental bronchi run. Do B2 and B6 actually run dorsally and B3 run ventrally when a patient lies supine? Although we expected variations, we set out with the belief that these "typical" courses would be found for the majority of segmental bronchi. In fact, B3 formed mean ± SD angles of 50.2 ± 11.8° from the horizontal in the right lung and 49.9 ± 11.6° in the left lung when the cadaver was in the supine position (Table 2
). It never formed a right angle; the maximum angle was 75.0°. Thus, B3 ran in a ventral direction but was never included in the dorsoventral plane when the cadaver was placed in the supine position. Likewise, although B6 ran in a dorsal direction (mean angle of 48.1° from the horizontal in the right lung and 34.7° in the left lung), it did not follow an actual dorsal course (ie, - 90°). Moreover, the angle for B6 was < - 60° in only a few specimens (14 of 54 right lungs and 1 of 52 left lungs). In these lungs, B6 exhibited an almost horizontal course, for which we measured angles of - 5° to - 10° from the horizontal in the supine position. Similarly, B2 ran in a dorsal direction ( angle in the supine position, - 65.9 ± 15.9°) but never took a true dorsal course (maximum angle, - 85° from the horizontal). However, a angle of < - 60° was found for the B2 of 39 right lungs in the supine position. In both the left and right lungs, the B2 courses tended to shift dorsally more frequently than those of B6. B1 formed an mean angle of 16.7 ± 10.1° from the horizontal in the supine position, while B1 + 2 formed an angle of - 8.8 ± 13.0°. These small angles meant that both segmental bronchi ran almost horizontally. Completely horizontal courses were recorded for the B1 of two right lungs and the B1 + 2 of seven left lungs. However, B1 almost always followed a ventral course with a positive angle in the right lung (52 of the 54 specimens), whereas in most of the left lungs (40 of the 52 specimens), B1 + 2 displayed a dorsal course with a negative angle.
Secondly, since we now doubted the usual concepts regarding bronchial courses (see earlier), we investigated whether the segmental bronchi were elevated at an angle sufficient to allow drainage when the cadavers were placed in the recommended postures. We hypothesized that smooth drainage would require a angle of > 45° from the horizontal in any particular posture.
For the right lung, the supine position or bending backward is recommended to achieve drainage along B1 (Table 1
; Fig 1
). The supine position did not provide a B1 elevation of > 45° in any of the 54 right lungs; however, bending backward usually made a steep enough angle (50 of 54 right lungs; Fig 4
, top left, A). The angles ranged from 30.0 to 80.0° (mean, 55.5 ± 11.0°) for B1 when bending backward; in the supine position, they ranged from 0 to 40.0° (mean, 16.7 ± 10.1°). Although either bending forward or the 45° rotative prone position is recommended for B2 drainage, elevation of B2 by > 45° from the horizontal was more often observed in the latter position (47 of 54 lungs; Fig 4
, top right, B) than in the former. The angle for B2 ranged from 15.0 to 75.0° (mean, 42.5 ± 15.0°) when bending forward; in the 45° rotative prone position, it ranged from 20.0 to 85.0° (mean, 55.6. ± 14.4°). The recommended postures for draining B3 or B6 in the right lung, supine and prone respectively, at least sometimes (B3, 12 of 54 lungs; B6, 20 of 54 lungs) provided an inadequate angle of < 45° (Fig 4
, bottom left, C, and bottom right, D) because the majority of cadavers did not show the typical directions for these segmental bronchi (see earlier). The angles ranged from 15.0 to 75.0° (mean, 50.2 ± 11.8°) for B3 in the supine position and from 15.0 to 80.0° (mean, 48.1 ± 15.1°) for B6 in the prone position. Notably, although it is not included among the recommended postures, the 45° rotative prone position was good for B6 drainage because the angle was usually > 45° (Fig 4
, bottom right, D).
We then investigated postures in which other right segmental bronchi formed positive angles (ie, angles > 1°) in the majority (ie, > 90%) of specimens. The supine, 45° rotative supine with head down, lateral, and prone positions have been recommended for drainage of B8, the middle lobe bronchi (B4 and B5), B9 and B10, respectively. However, we found fair or good results for the simple supine position without rotation and head-down in draining the middle lobe and B8, and for the 45° rotative prone (right-side-up) position in draining B9 and B10. In contrast, the prone position led to negative angles not only for B9 and B10 in almost 15% of specimens, but also for the middle lobe bronchi and B8 in > 20% of specimens (not shown in detail).
For the left lung, we found a clear difference in the effectiveness of B1 + 2 drainage between two similar recommended postures: the 45° rotative prone position with or without the head raised (Fig 5
, top, A). With the head raised, the craniocaudal axis of the lung was tilted at 30°, thus providing a great increase in the angle. This angle ranged from 35.0 to 85.0° (mean, 57.8 ± 11.6°) for B1 + 2 in the 45° rotative prone with head-raised position; in the simple 45° rotative prone position, it ranged from 10.0 to 60.0° (mean, 36.2 ± 13.0°). For B3 and B6 in the right and left lungs, the recommended supine or prone positions often or usually (B3, 17 of 52 lungs; B6, 40 of 52 lungs) produced an acute angle of < 45° (Fig 5
, center, B, and bottom, C). These inadequate angles were more frequently seen in the left lung than in the right lung, and were especially evident with the left B6. However, as with the right lung (see above), we found that the 45° rotative prone position provided good B6 drainage in the left lung (Fig 5
, bottom, C). The angle ranged from 25.0 to 75.0° (mean, 49.9 ± 11.6°) for B3 in the supine position and from 5.0 to 70.0° (mean, 34.7 ± 11.3°) for B6 in the prone position. For the other left segmental bronchi (B4, B5, B8, B9, and B10), large angles were obtained with the same positions as in the right lung. Consequently, instead of the recommended postures, the supine position would be most effective in draining B4 and B5, and the 45° rotative prone (left-side-up) position would be most effective in draining B9 and B10.
Angles at Which the Subsegmental Bronchi Originate From the Segmental Bronchus
We have already shown the variations in the angles at the origins of the subsegmental bronchi (see "Materials and Methods" section; Fig 3
). In these measurements at the origins of the subsegmental bronchi, the so-called branching angle,14
or the angle between the segmental and the subsegmental bronchus, was defined as 180° when the subsegmental bronchus was a straight continuation of the mother bronchus. Although it was different from the "angle " defined in Figure 2
, the subsegmental bronchi usually displayed angles of 120 to 180° from the longitudinal axis of the mother segmental bronchi (ie, a branching angle; Table 3
), forming a broom-like bronchial tree. However, in the right lung, we found exceptional cases with angles of < 120° in B1a (4 of 54 lungs), B1b (n = 1), B2a (n = 1), B3a (n = 11), B6a (n = 11), B6b (n = 3), and B6c (n = 5). In particular, two B3a, three B6a, and two B6c bronchi in seven different right lungs exhibited angles of 
90° (minimum 80.0°). This resulted in the subsegmental bronchi taking a recurrent course. Likewise, in the left lung, we sometimes found relatively narrow angles (< 120°) between the mother and daughter bronchi in B1 + 2c (3 of 52 lungs), B3a (n = 13), B3a (n = 4), B6b (n = 1), and B6c (n = 5). However, acute angles or recurrent courses were observed only in the B3a of four left lungs. In other segments, usually those in the lower lobe, none of the subsegmental bronchi followed a recurrent course (not shown in detail). Consequently, 11 of 106 lungs contained a recurrent subsegmental bronchus (one bronchus per lung).
Running Directions of the Subsegmental Bronchi and Recommended Postures for Draining the Segment
Is the posture traditionally recommended for each segment (Fig 1) really effective in draining its peripheral or subsegmental levels? Table 4
shows the incidences of recurrent courses or negative angles (causing extreme difficulty in drainage) and of positive but small angles (< 20°, causing relative difficulty in drainage) for each of the subsegmental bronchi. The direction in which a subsegmental bronchus ran when the lung was placed in the recommended posture for draining a particular segment depended not only on the angle of the mother segmental bronchus (s in Fig 2
; see first subsection in "Results"), but also on the branching angle at the origin of the subsegmental bronchus (see second subsection in "Results").
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Table 4.. Anatomically Evaluated Incidences of Difficult Subsegmental Drainage at Recommended Posture Corresponding to Each Segment*
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Because bending backward (or the 45° rotative prone with head-raised position) consistently resulted in large angles for B1 (or B1 + 2), its subsegmental bronchi did not form a negative angle (and hence a recurrent course) in spite of the major variations in the angle at the subsegmental bronchial origin, which could be > 100° (note that this is not the angle ; Table 3
). Likewise, for B6, the 45° rotative prone position provided a good result, since its subsegmental bronchi did not exhibit a recurrent course. Conversely, in several cases, B3 formed small angles when the lung was in the supine position (Figs 4
, bottom left, C, and 5
, center, B) and B3a exhibited a negative angle or recurrent course (Table 3)
. In this situation, we sometimes found drainage extremely difficult (11.5%) and often found it relatively difficult (51.9%). Notably, the small angle for B1 in the supine position (Fig 4
, top left, A) did not influence the angle for B1b but specifically affected that of B1a. Most of the B1a bronchi were relatively difficult to drain in the supine position (Table 4)
. Likewise, the small angle for B6 in the prone position (Figs 4
, bottom right, D, and 5
, bottom, C) mainly affected that for B6b (Table 4) . We found that the 45° rotative prone position with left or right side up was effective in improving this difficult drainage from B1a, B2b, and B6b in the right lung and B6a-c in the left lung, although this posture is not included in the recommended sequences. Especially in the right B6b and in the left B6b and B6c, a positive shift in the distributions of individual angles was evident (data not shown) when the posture was changed from prone to 45° rotative prone. For the two subsegmental bronchi of B1, effective drainage could not be achieved with a single posture but needed a combination of the supine (for B1b) and 45° rotative prone (for B1a) positions.
Taken together, a combination of the supine and 45° rotative prone with left and right sides up positions usually (almost 80% of specimens) produced angles of > 20° in all segmental and subsegmental bronchi. Consequently, in view of anatomy, even without the prone position, the limited combination of these three postures seemed to be effective in achieving postural bronchial drainage of all lung segments.
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Discussion
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In contrast to previous morphometric studies6
14
15
16
17
18
on the bronchial tree, in which the authors investigated biophysical, topological, and/or geometric rules, the present results provided concrete data regarding the running directions and relative angles of the segmental and subsegmental bronchi. Postural bronchial drainage has been evaluated over a long period of time. Some researchers19
20
21
22
23
have reported purely positive results, whereas others24
25
26
have suggested limitations and/or found no significant effect. In accordance with the latter, the present results also suggest that the classically recommended postures might have yielded poor results. In view of the bronchial anatomy, for instance, the effectiveness of the supine position in draining B1a and B6, and that of the prone position in draining B3 is very doubtful. However, using a combination of several postures rather than a single posture might provide some effect. Indeed, the effects of a series of changing postures seems to be valuable.
Notably, the present work revealed that the 45° rotative prone position was often more effective than the classical recommendations. Although we concentrated on S1-S3, S1 + 2, and S6, the classical method seemed less effective in draining the middle and lower lobes (ie, using the simple prone position for B9 and B10), but the 45° rotative prone position appeared much more effective. Moving a patient into the prone position requires two or three people, including a physiotherapist, whereas one person alone can move a patient into the 45° rotative prone position. Although there may be no pathologic condition prohibiting use of the prone position, the choice of this posture, rather than the 45° rotative prone position, may have resulted simply from an anatomic misunderstanding.
For routine clinical use, it is preferable to use the simplest maneuvers possible. However, a combination of many postures, as recommended in the classical methods,1
2
seems to confer an advantage or a combined effect. Such sequences might be effective in achieving drainage from a long common trunk serving many segmental bronchi, such as the right upper bronchus and left upper division bronchus (B1 + 2 and B3). These common trunks may act as a reservoir for discharge or absorb the therapeutic effect of postural drainage when the discharge is not completely removed. According to Takase,27
the trifurcation of the right upper bronchus ranged from 6.0 to 18.0 mm (mean, 11.7 mm) in length, while the left upper division bronchus averages 7.2 mm (range, 3.0 to 12.0 mm). These lengths may be enough to allow the hypothetical reservoir action. Moreover, combined postures may also improve the clearance of possible back-and-forward flow of bronchial secretions. Nevertheless, postural drainage maneuvers should be as simple as possible and should be based on noninvasive postures, especially for patients with tracheal intubation.
According to our anatomic results, we predict effectiveness of the following sequence of postures: supine, 45° rotative prone with left side up, 45° rotative prone with right side up, and return to supine (Fig 1
, right, G through I) for simple, safe, and convenient bronchial drainage, especially for patients with tracheal intubation. However, our recommendations are not without potential disadvantages, and these are outlined in Table 4 . For the two subsegmental bronchi of B1a, effective drainage is not likely to be achieved with a single posture, but will require a combination of the supine (for B1b) and 45° rotative prone (for B1a) positions. Because patients are usually cared for in the supine position, bronchial secretions from B1a may often (almost 50% of right lungs, data not shown) move easily to B1b. However, in the next turn in the present sequence, moving into the 45° rotative prone with left-side-up position would remove these accumulated secretions from B1b. Likewise, in almost half of the lungs, discharge from B1b seems to move to B1a in the rotative prone position. This would be removed in the next turn to supine.
A potential concern is that, in about half of patients, secretions would not be removed but may move forward and backward between B1a and B1b. This back-and-forward flow may also occur between B2 and B3a because of their different running directions. However, rotational maneuvers provide differences in the drainage courses of secretions besides forward and backward movements. Thus, we believe that our sequence would allow successful drainage of all secretions, including any return flow. In addition to the basic sequence proposed above, patients in whom drainage of B3a is difficult (estimated to occur in 11.5% of the right lungs investigated during the present study) may require inclusion of the 10° right-side-up supine position for complete drainage. Likewise, raising the head by 45° in combination with the 45° rotative prone position would permit complete drainage from B1 + 2a in others. Although the 45° head-raised posture would be contraindicated in emergency patients with low BP, we believe that addition of the 10° right-side-up supine and 45° rotative prone with head-raised 45° postures would not overturn the great advantage of our recommended sequence, ie, its simplicity.
In the present study, we used selected lungs in which identification of the segmental bronchi was clear and easy, such as a right upper bronchus with a simple trifurcation pattern. Does this impose a critical limitation on the study or introduce a selection bias to the results? Simple trifurcation of B1, B2, and B3 occurs in only 30%11
or 40%28
of Japanese subjects. Conversely, three major variations, B1 + 2, B1 + 3, and B2 + 3, are observed in almost half of right lungs. However, these major variations do not seem to compromise segment-specific drainage in a specific posture because their common trunks are usually very short.27
We speculate that problems may arise in < 10% of lungs in which one of the subsegmental bronchi (eg, B2a) forms a common trunk with another segmental bronchus (eg, B1). In the left lung, B1 + 2 and B3 make a long upper division trunk in 16% of lungs according to Arai and Shiozawa.28
Where this variation exists, physiotherapists may find it very difficult to decide how to conduct segmental bronchial drainage. Moreover, in the supine position, bronchial discharge tends to move from B3 to B1 + 2 because of the long common trunk and the dorsal running direction of B1 + 2. As we recommend a postural change from supine for B1 + 2 to 45° rotative prone for B3, discharge would be drained from the long upper division trunk as well as from B1 + 2 due to their similar directions. Thus, complete drainage from the upper division of the left upper lobe should be achievable with these positions. Consequently, we believe that our recommended sequence of postures [ie, (1) supine, (2) 45° rotative prone with left side up, (3) supine, (4) 45° rotative prone with right side up, and (5) supine, as shown in Figure 1
, right, G through I] is adequate even where variations in the bronchial tree exist. Nevertheless, the classical method with its greater combination of postures may have an advantage when there are such variations. Therefore, we postulate limited application of the present method to patients with tracheal intubation who cannot be subjected to multiple position changes.
Study Limitation
The lung materials examined in the present study were usually fixed at their maximum expiratory point at death. However, chest physiotherapy is generally performed in the tidal volume range. How much difference in the bronchial courses and branching angles would there be for the fixed cadaveric lungs? Can some of the extreme variation in branching angles be attributed to the maximum expiratory point at death? Although further intensive studies might be necessary to resolve these questions, using three-dimensionally reconstructed images obtained from high-resolution CT for three pairs of healthy lungs of the present authors (N.T., G.M., A.I.), we investigated the difference in branching angles between the tidal volume range and forced expiratory point. The results were summarized as follows: (1) effectiveness for the segmental drainage seemed to be almost consistent because the changes in branching angles of all segmental bronchi were limited to ± 5° except for B4 and B5 with + 10 to + 15° (thus, they became more effective); (2) the changes in subsegmental bronchial angles ranged from 26 to + 38° (mean, + 5.2°) in B1, B1 + 2, B3, and B6; and (3) changes in branching angles of another subsegmental bronchi, such as in the middle and lower lobes, were limited to ± 10° and provided no negative influence on the effectiveness category. Those plus angles, including the mean subsegmental angle, are predictive of accelerated drainage or increased effectiveness. Thus, these changes in angles provided no negative influence on the effectiveness category because the angles still remained in the "effective" category, even upgrading the category, after changes except for the left B6c of author A.I., in which the effective changed into a "less effective" category. Therefore, not only the forced expiratory phase in the present additional experiment but also the maximum expiratory phase seen in fixed cadavers seemed not to provide a significant negative influence on the effectiveness evaluated in the present study. Moreover, those three pairs of volunteer lungs include several branching angles similar to the extremely deviated variation found in the cadaveric lungs, ie, almost maximum angles were found in B1b and B3b in the right lung of the volunteers and in B1 + 2c, B3a, and B6b in the left lung of the volunteers, while nearly minimum in B2a in the right lung and B6c in the left lung. Therefore, in spite of the difference in age, these three pairs of lungs seemed to roughly reflect a standard distribution of angles in the cadaveric population. Consequently, from the anatomic viewpoints, we believe that our recommended sequence of postures will be effective for patients. Clinical trials to test the effectiveness of our recommended procedures, especially of 45° rotative prone, need to be carried out.
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Acknowledgements
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We are grateful to the professors of the following Departments of Anatomy for permission to use their materials: Emeritus Professors T. Arikuni and H. Hoshi (Nihon University School of Medicine), Emeritus Professor S. Uchino (Tokyo Medical College), Emeritus Professor A. Nakao (Akita University School of Medicine), Professor Y. Dodo (Tohoku University School of Medicine), and Professor T. Kachi (Hirosaki University School of Medicine). We are also grateful to Dr. Akira Sakurada for his advice regarding references. To investigate the suspected study limitation, we needed the strong assistance of Dr. Mitsuharu Tamakawa in the Division of Diagnostic Radiology in Sapporo Medical University. We thank him and his colleagues for their efforts.
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Footnotes
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The present research was performed within the limitation of usual financial support by the Sapporo Medical University.
Received for publication December 16, 2002.
Accepted for publication July 17, 2003.
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Abstract
Introduction
