SP-21 (Da Bao) Great Embracement

What does SP-21 Da Bao do?

Da Bao SP-21 is the Great Luo-Connecting point of the Spleen — the fifteenth and most unusual member of the Connecting-point set — and its recorded work is to regulate qi and blood, to unbind the chest and lateral costal region, and to firm the sinews and joints of the whole body. Sacred Lotus sources & references record that classification and those actions directly. The last of those actions is the one that marks the point out: almost every point in the repertoire acts on a region or an organ, and this one is credited with an effect on the body as a whole.

• Regulates qi and blood throughout the body — the primary recorded action, and the one that follows from the classification. The Great Luo of the Spleen is described in the classical sources as spreading through the chest and lateral ribs and binding the blood of all the vessels together, which is why its recorded action is general rather than local.
• Firms the sinews and joints — the action behind the point's most distinctive indication, a body that aches all over or limbs that feel slack and weak with no single site of pain. This is a whole-body action, not a local one, and very few points carry anything like it.
• Unbinds the chest — for a chest that feels full, tight or oppressed, and for difficult breathing. The point sits on the side wall of the chest, and this is its local action.
• Benefits the lateral costal region — for pain in the flanks and along the lower ribs. The Spleen channel's upper course runs up the side of the trunk to this point, and pain along that line is what the point is chosen for locally.
• Serves as the Spleen's second, higher connection — the Spleen is the only organ given two Connecting points: Gong Sun SP-04 at the foot, which is the ordinary channel Luo point crossing to the Stomach channel, and Da Bao SP-21 on the chest, which is the Great Luo and crosses to nothing. The two are not alternatives; they do different jobs, and the distinction is set out under the notes below.

Source: Sacred Lotus sources & references (existing action record; Spleen channel and Great Luo classification queried directly); Deadman & Al-Khafaji, A Manual of Acupuncture (p. 204); Chinese Acupuncture & Moxibustion (p. 163); Ling Shu (Spiritual Pivot), Chapter 10, on the fifteen Connecting vessels and the Great Luo of the Spleen; cross-referenced against multiple online sources.

What is SP-21 Da Bao used for?

Da Bao SP-21 is used for pain in the chest and the flanks, for difficult or asthmatic breathing, and — most characteristically — for generalised aching and weakness of the whole body with no single site of pain. The indications below are those carried in Sacred Lotus sources & references together with those set out in the standard reference literature. They describe traditional use, not proven treatment, and this point carries the lateral-chest safety facts set out under needling.

• Pain in the chest
• Pain in the hypochondriac region — the flanks below the ribs
• Fullness and oppression of the chest
• Difficult breathing and asthmatic breathing
• Aching of the whole body with no single site of pain
• General weakness and weakness of the four limbs
• Slackness and looseness of all the joints
• Inability to lie down comfortably because of fullness in the chest
• Pain along the side of the trunk and the lower ribs
• Intercostal pain
• Fatigue with heaviness of the limbs

Source: Sacred Lotus sources & references (existing indication record); Deadman & Al-Khafaji, A Manual of Acupuncture (p. 204); Chinese Acupuncture & Moxibustion (p. 163); Ling Shu (Spiritual Pivot), Chapter 10.

Where is SP-21 Da Bao, and how is it used in practice?

Da Bao lies on the side wall of the chest, on the mid-axillary line — the vertical line dropped from the middle of the armpit — in an intercostal space some way below the armpit. It is the last point of the Spleen channel and the highest, and it is the only Spleen-channel point on the side of the chest rather than the front. It is a bilateral point, and in practice it is very often treated by methods that do not involve a needle at all: moxibustion, cupping and massage over the lateral ribs are all recorded here, and all of them sidestep the depth question that makes this a point to understand before it is used.

Our two location records do not agree on which intercostal space, and we have kept both rather than picking a winner. One of our sourced location records places SP-21 in the sixth intercostal space on the mid-axillary line; the other places it in the seventh. This is a genuine and long-standing disagreement in the reference literature rather than an error in our data, and our own notes have carried it for years. The practical consequence is small — one rib space on the side of the chest — but it is real, and a reader comparing our page against another source should know that the difference is in the sources, not in the transcription. Both records are left exactly as sourced.

Which points is SP-21 combined with?

• With Zhang Men LIV-13 — the Front-Mu point of the Spleen, confirmed by query in Sacred Lotus sources & references, which lies just in front of and below the free end of the eleventh rib on the same side of the trunk. Two Spleen-related points on the flank, one the organ's Front-Mu and one the channel's Great Luo, and they are the natural pair when the target is the Spleen and the complaint is in the side.
• With Gong Sun SP-04 — the Spleen's ordinary Connecting point at the foot. Using the channel's two Luo points together, one at each end of the channel, is the structure that makes sense of a channel given two connections.
• With Shan Zhong REN-17 — the Hui-Meeting point of qi on the front midline of the chest, held in this library. Where the chest is oppressed and the breathing difficult, the front midline point and the lateral chest point are used together, and REN-17's classification as the influential point of qi is what gives the pairing its logic.
• With Zhou Rong SP-20 and the upper Spleen chest points — SP-17 Shi Dou, SP-18 Tian Xi, SP-19 Xiong Xiang and SP-20 Zhou Rong run up the side of the chest below and in front of SP-21, all held here, and all carry the same bounded oblique needling record. They are the local run of the channel on the chest.
• With Yuan Ye GB-22 — the nearest neighbouring point of another channel, on the same mid-axillary line one or two rib spaces above, held here. Our own records place GB-22 on the mid-axillary line in the fifth intercostal space, which is directly above SP-21 on either reading of SP-21's own location.
• With Ge Shu BL-17 — the Hui-Meeting point of blood on the back, added wherever the treatment is aimed at blood rather than qi. SP-21's classical description as the vessel that binds the blood of the whole body is what makes this pairing coherent.
• With San Yin Jiao SP-06, Yin Ling Quan SP-09 and Zu San Li ST-36 — the leg points that build qi and blood, added where SP-21 is being used for generalised weakness and aching rather than for the chest. Local point at the trunk with distal points at the leg is the usual structure.

Where does SP-21 sit among the Connecting points?

The Connecting or Luo points are where a channel throws off a branching vessel that crosses to its interior-exterior partner. Sacred Lotus sources & references hold the complete set of fifteen Connecting points: the twelve channel Luo points — LU-07 Lie Que, LI-06 Pian Li, ST-40 Feng Long, SP-04 Gong Sun, HT-05 Tong Li, SI-07 Zhi Zheng, BL-58 Fei Yang, KI-04 Da Zhong, P-06 Nei Guan, SJ-05 Wai Guan, GB-37 Guang Ming and LIV-05 Li Gou — together with REN-15 Jiu Wei, the Connecting point of the Conception Vessel, DU-01 Chang Qiang, the Connecting point of the Governing Vessel, and SP-21 Da Bao, the Great Connecting point of the Spleen. That is the same set reproduced on our SJ-05, ST-40, GB-37 and BL-58 pages, queried afresh here rather than copied from recall.

SP-21 is the odd one out, and it is worth being precise about why. Fourteen of the fifteen are channel-to-channel connections: each throws a branch across to a named partner vessel, and each is used to treat two channels with one needle. Our own records make this concrete — the Great Luo classification at SP-21 is recorded as its own distinct category, not as the ordinary Luo classification that SP-04 carries. The differences are these:

• It connects to no partner channel. The other fourteen each name a destination. The Great Luo of the Spleen names none; the classical description has it spreading out through the chest and the lateral costal region rather than travelling to another vessel.
• It has no Yuan-Luo partner. The standard use of a Connecting point is to pair it with the Source point of its partner channel — SP-04 with ST-42 Chong Yang, ST-40 with SP-03 Tai Bai, and so on through the twelve, all held here. SP-21 has no such pairing available, because there is no partner channel to take a Source point from.
• Its channel already has an ordinary Luo point. SP-04 Gong Sun is the Spleen's channel Luo point and behaves like the other eleven. SP-21 is additional. The Spleen is the only one of the twelve organs given two.
• Its remit is the whole body rather than a channel. The classical statement is that this vessel binds the blood of all the vessels together, and the recorded excess and deficiency signs are correspondingly general — pain everywhere, or every joint slack — rather than referred to one channel's course.

Source: Sacred Lotus sources & references (location, channel and Great Luo classification; the full fifteen-point Connecting set, the Yuan-Source set and the LIV-13, SP-04, SP-17, SP-18, SP-19, SP-20, GB-22, REN-17, BL-17, SP-06, SP-09 and ST-36 records queried directly); Deadman & Al-Khafaji, A Manual of Acupuncture (p. 204); Chinese Acupuncture & Moxibustion (p. 163); Ling Shu (Spiritual Pivot), Chapter 10; cross-referenced against multiple online sources.

Where is SP-21 located?

• A Manual of Acupuncture (p. 204): On the mid-axillary line, in the seventh intercostal space.
• Chinese Acupuncture and Moxibustion (p. 163): On the lateral side of the chest and on the middle axillary line, in the 6th intercostal space.

How is SP-21 Da Bao needled, and what is the pneumothorax risk?

Stated plainly: SP-21 lies over an intercostal space on the side wall of the chest with the lung directly beneath it, and pneumothorax — a punctured lung — is the documented hazard at this point and at every point in the lateral chest band it belongs to. The reference texts do not record a perpendicular insertion here. Our own record specifies oblique insertion of 0.3 to 0.5 inch, and the angle is the substance of the record, not a stylistic detail. Everything below is recorded as neutral reference data describing what the textbooks and the published anatomical studies state. It is not instruction, this page does not teach technique, and needling is carried out only by a qualified, licensed practitioner.

The angle and depth the texts record

• Sacred Lotus sources & references record oblique insertion of 0.3 to 0.5 inch, with moxibustion applicable. Queried across the whole lateral chest run, our records give the identical bounded figure at SP-17 Shi Dou, SP-18 Tian Xi, SP-19 Xiong Xiang, SP-20 Zhou Rong and at GB-22 Yuan Ye on the same mid-axillary line. That uniformity is itself the informative fact: the constraint belongs to the region, not to any one point in it, and it is the tightest bounded range our records carry anywhere on the trunk.
• Deadman & Al-Khafaji (p. 204) and Chinese Acupuncture & Moxibustion (p. 163) record oblique or transverse insertion along the intercostal space in a comparable range, and both attach an explicit caution against deep or perpendicular insertion at the points of the chest wall because of the lung beneath. Angling along the rib space keeps the needle travelling in the plane of the chest wall rather than pointing into it.
• Moxibustion, cupping and massage are all recorded here and are common at this point. None of them carries the pneumothorax hazard, and that is a substantial part of why the lateral ribs are so often treated without a needle at all.
• For comparison within our own holdings: the 0.3–0.5 inch recorded at SP-21 is the same figure our records give for GB-21 over the apex of the lung, is shallower than the 0.5–0.7 inch given for the thoracic Back-Shu points such as BL-13 and BL-15, and is far shallower than the figures recorded at limb points. Depth figures in this literature track the structure underneath, not the size of the region.

The measured anatomy — and precisely what each study measured

• Honest limit, stated first. No adult imaging or cadaveric measurement of a safe needling depth at SP-21 specifically could be located. One paediatric CT study does measure this point by name, and its figure is given first below. Beyond it, rather than borrow a figure taken elsewhere and attach it to this point, what follows is the measured anatomy of the surrounding region, with every measurement attributed to the point at which it was actually made.
• A CT study that measured SP-21 itself. This is the point-specific finding, and it corrects an earlier statement on this page. A retrospective study measured, directly from CT images, the safe needling depth at 23 upper-back acupoints in 319 patients aged 4 to 18 (205 boys, 114 girls), defining safe depth at the non-midline points as the distance from the skin surface of the point to the pleura. The 23 points were DU-09 to DU-14, BL-11 to BL-17, BL-41 to BL-46, SI-14, SI-15, GB-21 and SP-21 — this last located, in the study's own words, at the intersection of the sixth intercostal space and the midaxillary line, which is one of the two locations our own records give. The measured depth at Da Bao SP-21 was 19.48 ± 4.39 mm in boys and 18.84 ± 4.56 mm in girls, a difference that was not significant at this point (P = 0.216), although it was significant at most others on the list. Across the five age bands the depth at SP-21 rose from 16.97 ± 2.89 mm at ages 4 to 6 to 21.34 ± 5.17 mm at ages 16 to 18 (P < 0.001), and it rose with weight as well, from 17.97 ± 4.26 mm in the lightest band to 22.46 ± 5.89 mm in the heaviest (P < 0.001). Multiple regression identified weight as the single most important determinant at all 23 points (Ma YC et al., BMC Complement Altern Med 2016;16:85, PMID 26922245, PMC4769822, DOI 10.1186/s12906-016-1060-x). State the limits precisely: these are children and adolescents drawn from a single Taiwanese hospital population, all of them patients rather than healthy children, and the figure is the distance at which the pleura is reached — not a recommended needling depth. The fact worth carrying away is the scale: at SP-21 the study found under two centimetres of tissue over the pleura on average, and under 1.7 cm in the youngest band — among the smallest margins anywhere on its 23-point list.
• A second, different paediatric study — of the front of the chest — measured 28 points by name, and SP-21 was not among those. This is a separate paper from the upper-back study above, by an overlapping group, and the two have been confused before; they are kept apart here. It measured, directly from chest CT images, the distance from the skin surface to the major organs at 28 chest acupoints in 319 patients aged 4 to 18 (205 boys, 114 girls). Its point list runs the Conception Vessel chest sequence, the upper Kidney run KI-22 to KI-27, ST-13 to ST-18, SP-17 to SP-20, GB-22, GB-23, LU-01, LU-02 and the first Pericardium point. Depth differed significantly by age group (P < 0.001), by weight group and by body mass index group, and the authors' conclusion was that clinicians should attend to the wide variation in needle depth (Ma YC et al., Evid Based Complement Alternat Med 2015;2015:126028, PMID 26457105, PMC4592721). SP-21 is not in that list — the Spleen run stops at SP-20 — and no figure from the study is attributed to it here. What it does establish, at the neighbouring points, is the scale: at Ru Gen ST-18, measured by name in the same study, the mean depth to the underlying organ was 13.35 ± 4.82 mm in boys and 14.96 ± 7.33 mm in girls, rising from about 10.5 mm in the 4-to-6 age group to about 16.3 mm at 16 to 18. That is ST-18's figure, not SP-21's — but it makes concrete how little tissue can lie over the lung on a child's chest wall.
• How thin the tissue can be over the lung in adults — measured at GB-21. Ultrasonography in 101 adults measured the depth from skin to the pleural line at Jian Jing GB-21 on the shoulder as 17.4 mm in men and 14.6 mm in women on average, increasing with weight, height and body mass index (Lin S-K et al., J Acupunct Meridian Stud 2018;11(6):355–360, PMID 29936338). That figure is for GB-21, not for Da Bao. It is offered as the measured scale of the chest-wall region, and it makes the essential point: over the shoulder girdle and chest wall, a centimetre and a half can be the whole of the margin.
• Cadaveric mapping of the pleural dome — the study named BL-11. A dissection study of 46 adult bodies mapped the dome of the pleura against the commonly used points around it, naming Da Zhu BL-11 explicitly alongside Tian Tu REN-22, Jian Jing GB-21, Qi She ST-11 and Ding Chuan. The projection of the pleural dome varied widely between individuals, extending beyond the medial third of the clavicle in almost 60 per cent of bodies, and the authors concluded that when a point is located and angled as the standard describes the pleura is not reached, while exceeding the recorded depth breaches the pleural membrane (Chen Y et al., Zhongguo Zhen Jiu 2006;26(5):346–348, PMID 16739850). That study named BL-11 and concerns the apex of the lung, not the lateral chest wall at SP-21. It is cited for the principle — that the recorded depth is the whole margin — and not as a measurement of this point.
• Adult chest depths, measured as a region. A computed-tomography study of 120 patients grouped by body weight, height and sex measured, for each commonly used chest point, the distance from the skin surface to the thoracic pleura and defined that distance as the point's safe depth, finding significant differences between body-size groups (Sheu CY, Lin JG, Zhonghua Yi Xue Za Zhi (Taipei) 1992;50(5):388–399, PMID 1338010), with a companion study doing the same for the back (Zhong Xi Yi Jie He Za Zhi 1991;11(1):10–13, PMID 2054884). Neither abstract names SP-21 among the points measured.
• No single agreed safe depth exists for any point. Two systematic reviews of the safe-depth literature — 33 studies in the first, 47 in the second, by MRI, CT, ultrasound and cadaveric dissection — both concluded that measured depths for the same point differ greatly between subject groups and measuring methods, and that "safe depth" has never been standardised (J Altern Complement Med 2011;17(3):199–206, PMID 21417806; Evid Based Complement Alternat Med 2013;2013:740508, PMID 23935678). A textbook depth figure describes an average body, not a constant.
• The single most telling anatomical fact about this location. A published emergency case report describes a 64-year-old woman who developed sudden breathlessness after an acupuncture treatment for back pain, was initially treated as acute heart failure, and was found to have a large left-sided tension pneumothorax; the attending surgeon decompressed it by placing a chest tube in the sixth intercostal space in the mid-axillary line (Hussain AA et al., Case Rep Cardiol 2021;2021:9986300, PMID 34650818, PMC8510795). Those are SP-21's own coordinates on one of our two location records — the sixth intercostal space on the mid-axillary line is precisely the site surgeons use to enter the pleural cavity, because it is the place on the chest wall where the pleural space is most reliably and most easily reached. The report does not name SP-21 and does not attribute the injury to it, and no such claim is made here. It is cited because it states, from the surgical side, exactly what lies behind this piece of chest wall and how directly it is reached.
• What lies beneath, in plain terms. At this point the needle passes through skin and subcutaneous tissue, then the digitations of serratus anterior on the rib cage, then the intercostal muscles filling the rib space — and immediately behind those, the parietal pleura and the lung. The intercostal nerve and vessels run in the groove along the lower border of each rib. There is no bony floor and no muscle mass to absorb a deep needle, which is the whole anatomical reason for the recorded shallow oblique angle.

What is documented, and how often

Pneumothorax is the second most frequently reported serious adverse event in acupuncture. A systematic review of the Chinese case-report literature from 1956 to 2010 identified 1,038 adverse-event cases across 167 articles, of which 307 were pneumothorax — behind only fainting. Thirty-five deaths were recorded across the series, and the authors attributed the events chiefly to improper technique, concluding that most were avoidable through standardised training (He W et al., J Altern Complement Med 2012;18(10):892–901, PMID 22967282). A companion systematic review of 115 Chinese-language articles reporting 479 adverse events including 14 deaths reached the same conclusion (Zhang J et al., Bull World Health Organ 2010;88(12):915–921C, PMID 21124716, PMC2995190). The presentation is not always immediate: a case report describes a healthy 38-year-old woman who developed pleuritic chest pain the day after dry needling of the back, with bedside ultrasound showing absent lung sliding (Cureus 2021;13(3):e14207, PMID 33948398, PMC8086747). Fatal cases exist: an autopsy report describes bilateral pneumothoraces following electroacupuncture, the authors noting that electrical pulses and the muscle contraction they cause may draw needles deeper than the depth at which they were inserted (J Forensic Sci 2022;67(1):377–383, PMID 34435369). A pneumothorax after needling over the chest wall may declare itself hours later, with sudden chest pain, breathlessness or a persistent dry cough; it is a medical emergency requiring immediate assessment.

What we will not claim. Despite an extensive search, we could not source a published case report naming SP-21 specifically as the point at which a pneumothorax or other injury occurred, and no such claim is made here. What is recorded is what is documented: a tightly bounded oblique depth across the whole lateral chest run in the reference texts, measured pleural depths of roughly a centimetre and a half at nearby points in adults and less than that in children, cadaveric evidence that exceeding the recorded depth in the chest wall breaches the pleura, the surgical fact that the sixth intercostal space in the mid-axillary line is the standard route into the pleural cavity, and a large published record of pneumothorax following needling over the thorax.

Risk in proportion

A meta-analysis of prospective clinical studies estimated serious adverse events in acupuncture at approximately 1 per 10,000 patients and around 8 per million treatments, with about half of all recorded events being bleeding, pain or flare at the needle site, placing acupuncture among the safer treatments in medicine (Bäumler P et al., BMJ Open 2021;11:e045961, PMID 34489268). Both facts belong together: the overall rate is low, and the events that do occur concentrate in the band of points over the lung to which Da Bao belongs. The bounded shallow oblique depth exists to keep it that way.

Source: Sacred Lotus sources & references (existing needling record; the SP-17, SP-18, SP-19, SP-20, GB-22, GB-21, BL-13 and BL-15 needling records queried directly for comparison); Deadman & Al-Khafaji, A Manual of Acupuncture (p. 204); Chinese Acupuncture & Moxibustion (p. 163); PMID 26922245 (PMC4769822 — full text Tables 2–6 read; measured SP-21 ITSELF among its 23 upper-back points); PMID 26457105 (PMC4592721 — a different study; measured SP-17 to SP-20 and ST-18, not SP-21); PMID 29936338 (measured GB-21); PMID 16739850 (named BL-11);PMID 1338010; PMID 2054884; PMID 21417806; PMID 23935678; PMID 34650818 (PMC8510795); PMID 22967282; PMID 21124716 (PMC2995190); PMID 33948398 (PMC8086747); PMID 34435369; PMID 34489268 — each verified resolvable and checked for retraction status before citation.

What does the name Da Bao mean?

Da Bao means "Great Embracement" — da, great or large, and bao, to wrap, embrace or enfold. Sacred Lotus sources & references translate it exactly that way; other renderings in circulation are "Great Wrapping", "Great Enveloping" and "General Control". All of them are reaching for the same image, and it is an unusually literal one. The point sits where the ribs curve round the side of the body, and the vessel it names is described in the classics as spreading out over the chest and the lateral ribs — wrapping the trunk. The name also states the classification: this is the great Luo, the large one, as against the ordinary channel Luo point Gong Sun SP-04 at the foot.

What is the Great Luo of the Spleen, and why is it different?

It is the fifteenth Connecting vessel, and it is the only one in the set that does not connect one channel to another. The other fourteen each throw a branch across to a named partner vessel; this one spreads. Chapter 10 of the Ling Shu, which sets out the fifteen Connecting vessels, describes the Great Luo of the Spleen by name as emerging at Da Bao and dispersing through the chest and the lateral costal region, and it gives the vessel a remit no other Luo point has: it is said to bind together the blood of all the vessels of the body. The excess and deficiency signs recorded for it follow directly from that and are worth reading side by side, because they are the clearest statement of what the point is for:

• When the vessel is in excess — pain throughout the whole body. Not pain along a channel, not pain in a region: pain everywhere.
• When the vessel is deficient — all the joints slack and loose, the body weak and unable to hold itself together.

That pair of signs is the reason our own record carries "firms the sinews and joints" as an action and "general aching and weakness" as an indication. A point whose classical remit is the blood of all the vessels is expected to produce whole-body signs when that remit fails, and those are the two the text names.

A related item worth knowing, so it is not confused with this one. The classical literature also describes a Great Luo of the Stomach, called Xu Li, in the Su Wen — the vessel felt beating below the left breast, which corresponds to the apex beat of the heart. It is described as a vessel, not as an acupuncture point, it has no point number, and Sacred Lotus sources & references hold no point of that name. It is mentioned here only because "great luo" appears in two places in the classics and readers meet both.

Why does the Spleen have two Connecting points?

Because the two do different jobs, and reading them together is the clearest way to understand what the Great Luo classification actually adds. Both are held in Sacred Lotus sources & references and both were queried directly:

• Gong Sun SP-04, on the inner edge of the foot, is the Spleen's ordinary Luo point. It behaves exactly like the other eleven channel Luo points: it throws a branch across to the Stomach channel, the Spleen's interior-exterior partner, and it pairs in use with Chong Yang ST-42, the Stomach's Source point — the Yuan-Luo combination. It also carries a second classification as the Confluent point of the Penetrating Vessel, which is why it is one of the busiest points in the repertoire.
• Da Bao SP-21, on the side of the chest, is the Great Luo. It crosses to no channel, has no Yuan-Luo partner, and its remit is the whole body rather than a paired channel. It is used for the chest and flanks locally, and for generalised aching and slackness in the way described above.

The practical rule that follows: if the intention is to treat the Spleen and Stomach together, or to open the Penetrating Vessel, the point is SP-04. If the intention is the chest, the flanks, or a body that aches all over without a locus, the point is SP-21. They are not substitutes for one another.

Is there research on SP-21 Da Bao?

The honest answer is that SP-21 has essentially no research of its own, and the small amount of literature that names it is a good illustration of why point-code searches have to be read rather than counted.

• The one trial that names it does so as one point among several. A randomised study of 52 intensive-care patients with diaphragmatic dysfunction associated with mechanical ventilation applied ultrasound-guided acupoint electrical stimulation, with the point list given as Zhangmen, Dabao (SP 21), Pishu BL-20 and Shenshu BL-23 among others; the treated group had shorter ventilation time and fewer reintubations than the control group (Zhongguo Zhen Jiu 2019;39(9):913–917, PMID 31544375). It is a small, single-centre, unblinded multi-point protocol, and nothing in it is attributable to SP-21 alone. Note in passing that the published abstract codes Zhangmen as "LR 3"; our own records hold Zhang Men as LIV-13, the Front-Mu point of the Spleen, while LIV-03 is Tai Chong at the foot. That is a transcription error in the abstract, not a discrepancy in our data.
• A second paper miscodes the point outright. A study of herpes zoster reports its detected treatment sites as including "Dabao (SP 15)" (Zhongguo Zhen Jiu 2011;31(5):416–419, PMID 21692286). Our own records hold Da Bao as SP-21; SP-15 is Da Heng, "Great Horizontal", on the abdomen. The two names differ by one character in transliteration. We record the paper here rather than citing it as evidence about this point, because a reader searching the literature for "Dabao" will meet it and should know what it is.
• Everything else a point-code search returns for this point is unrelated. Searching the biomedical literature for "SP21" or "Dabao" returns bacterial strain designations, place and surname collisions, genomics and materials-science papers. None of it concerns acupuncture. This is stated because it is a real hazard of citing by point code, and because the absence is the finding.
• What is not here. We could locate no randomised trial of SP-21, no sham-controlled study of it, and no clinical study in which it is the point under test. The one genuinely point-specific piece of research is anatomical, not clinical: the paediatric upper-back CT study described under needling (PMID 26922245, PMC4769822) measured Da Bao SP-21 by name among its 23 points and published a figure for it with the age, weight and body-mass-index breakdowns. Rather than cite whole-protocol trials as though they concerned this point, the accurate statement is that SP-21's basis is the classical record and the reference literature, with that single measurement beside it.

How does SP-21 compare with the points around it?

Zhou Rong SP-20, Xiong Xiang SP-19, Tian Xi SP-18 and Shi Dou SP-17 run up the side of the chest below and in front of SP-21 and are the Spleen channel's other chest points; all four share its bounded oblique needling record, and none carries a special-point classification. Yuan Ye GB-22 is the nearest point of another channel, on the same mid-axillary line one rib space above on our own records, and it is the Gall Bladder channel's armpit point for the chest and flanks. Zhang Men LIV-13, just below the free end of the eleventh rib, is the Spleen's Front-Mu point and the Hui-Meeting point of the zang organs — the point to choose when the Spleen as an organ is the target rather than the chest wall. Gong Sun SP-04 at the foot is SP-21's counterpart at the other end of the channel and the Spleen's ordinary Connecting point. Pi Shu BL-20 on the back is the Spleen's Back-Shu point, confirmed by query. And Shan Zhong REN-17 on the front midline is the point SP-21 is most often paired with when the chest is the target, being the Hui-Meeting point of qi. All are held in Sacred Lotus sources & references.

Source: Sacred Lotus sources & references (name, translation, channel, Great Luo classification, the full fifteen-point Connecting set, the Yuan-Source and Front-Mu sets, and the SP-04, SP-17, SP-18, SP-19, SP-20, GB-22, LIV-13, BL-20, BL-17 and REN-17 records queried directly); Deadman & Al-Khafaji, A Manual of Acupuncture (p. 204); Chinese Acupuncture & Moxibustion (p. 163); Ling Shu (Spiritual Pivot), Chapter 10, on the fifteen Connecting vessels; Su Wen (Basic Questions), Chapter 18, on Xu Li, the Great Luo of the Stomach; PMID 26922245 (PMC4769822 — measured SP-21 itself); PMID 31544375; PMID 21692286 (cited as an example of miscoding, not as evidence about this point) — each verified resolvable and checked for retraction status before citation; cross-referenced against multiple online sources.