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Syringe dead space: difference between revisions

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5| Reported magnitude = 0.002–0.100 mL depending on configuration5| Reported magnitude = 0.002–0.100 mL depending on configuration
6| Dominant contributor = Hub cavity, not the needle lumen6| Dominant contributor = Hub cavity, not the needle lumen
+7<!-- Representative volumes -->
+8| Insulin syringe, permanently attached needle = ≈0.002–0.006 mL
+9| 1 mL syringe, Luer slip plus 25G needle = ≈0.070 mL
+10| 3 mL syringe, Luer lock plus 21G needle = ≈0.080–0.100 mL
+11| Low-dead-space needle on a Luer hub = ≈0.010 mL
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13Magnitudes vary across almost two orders of magnitude between device types. A 1 mL insulin syringe with a permanently attached fine needle has a dead space of a few microlitres, because the plunger tip enters the needle hub and displaces almost all of it. A general-purpose syringe with a detachable needle on a Luer fitting retains of the order of 70–100 µL, most of it in the hub rather than in the needle.{{r|zule2009,zule2013}}18Magnitudes vary across almost two orders of magnitude between device types. A 1 mL insulin syringe with a permanently attached fine needle has a dead space of a few microlitres, because the plunger tip enters the needle hub and displaces almost all of it. A general-purpose syringe with a detachable needle on a Luer fitting retains of the order of 70–100 µL, most of it in the hub rather than in the needle.{{r|zule2009,zule2013}}
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+20Because doses of reconstituted peptides are frequently in the range 0.05–0.30 mL, dead space of 0.07 mL is not a marginal quantity in this context: it is comparable to the dose. The choice of device therefore has arithmetic consequences that a dose expressed in milligrams conceals.{{r|ppdeadspace}}
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15== Anatomy and terminology ==22== Anatomy and terminology ==
16A hypodermic syringe delivers liquid by advancing a plunger through a graduated barrel. The graduations relate to the position of the plunger tip, so the volume expelled is the barrel volume swept between the starting and finishing plunger positions. Any volume distal to the plunger tip at full depression is outside that swept volume and is retained.23A hypodermic syringe delivers liquid by advancing a plunger through a graduated barrel. The graduations relate to the position of the plunger tip, so the volume expelled is the barrel volume swept between the starting and finishing plunger positions. Any volume distal to the plunger tip at full depression is outside that swept volume and is retained.
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26The distinction between ''high dead-space'' and ''low dead-space'' devices entered the literature through injecting-drug-use epidemiology, where the retained volume determines how much blood a shared syringe can transfer. Low-dead-space designs achieve their reduction either by moulding the needle permanently into a plunger-penetrable hub, or by fitting a plastic insert into an otherwise standard Luer hub so that the plunger tip advances into it.{{r|zule2013}}33The distinction between ''high dead-space'' and ''low dead-space'' devices entered the literature through injecting-drug-use epidemiology, where the retained volume determines how much blood a shared syringe can transfer. Low-dead-space designs achieve their reduction either by moulding the needle permanently into a plunger-penetrable hub, or by fitting a plastic insert into an otherwise standard Luer hub so that the plunger tip advances into it.{{r|zule2013}}
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+35{{figure|syringe|Schematic of a syringe barrel, plunger and needle. Dead space is the volume distal to the plunger tip when the plunger is fully advanced.}}
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28== Measured and computed magnitudes ==37== Measured and computed magnitudes ==
29Published measurements are made gravimetrically: the assembled device is filled, fully discharged, and the retained mass determined by weighing, with density assumed. Values below are representative of those reported in the injection-equipment literature and vary between manufacturers of nominally equivalent devices.{{r|zule2009,zule2013}}38Published measurements are made gravimetrically: the assembled device is filled, fully discharged, and the retained mass determined by weighing, with density assumed. Values below are representative of those reported in the injection-equipment literature and vary between manufacturers of nominally equivalent devices.{{r|zule2009,zule2013}}
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40The consistent finding is that the hub dominates. This is counter-intuitive, because the needle is the visibly narrow and visibly long component, but the arithmetic is unambiguous once the lumen volume is computed from tubing dimensions.{{r|iso9626}}49The consistent finding is that the hub dominates. This is counter-intuitive, because the needle is the visibly narrow and visibly long component, but the arithmetic is unambiguous once the lumen volume is computed from tubing dimensions.{{r|iso9626}}
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+51|+ Computed needle lumen volume, 12.7 mm (half-inch) cannula
+52| !Gauge | Nominal outside diameter | Typical inside diameter | Lumen volume |
+53|---|---|---|---|
+54| 18G | 1.270 mm | 0.838 mm | 7.00 µL |
+55| 21G | 0.819 mm | 0.514 mm | 2.64 µL |
+56| 23G | 0.641 mm | 0.337 mm | 1.13 µL |
+57| 25G | 0.515 mm | 0.260 mm | 0.67 µL |
+58| 27G | 0.413 mm | 0.210 mm | 0.44 µL |
+59| 29G | 0.337 mm | 0.184 mm | 0.34 µL |
+60| 30G | 0.312 mm | 0.159 mm | 0.25 µL |
+61| 31G | 0.261 mm | 0.133 mm | 0.18 µL |
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+63=== Effect of needle length ===
+64Doubling cannula length from 12.7 mm to 25.4 mm doubles the lumen volume, taking a 25G needle from 0.67 to 1.34 µL. Against a hub of 60–70 µL this is immaterial. Needle length is selected on anatomical grounds — 4, 6 and 8 mm pen needles and 12.7 mm syringe needles are the common lengths for [[Subcutaneous injection|subcutaneous administration]] — and not on dead-space grounds.{{r|iso7864}}
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42== References ==66== References ==
43{{reflist}}67{{reflist}}
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46<ref name="strauss2006">Strauss K, van Zundert A, Frid A, Costigliola V. "Pandemic influenza preparedness: the critical role of the syringe." ''Vaccine'' 24(24):4874–4882 (2006).</ref>70<ref name="strauss2006">Strauss K, van Zundert A, Frid A, Costigliola V. "Pandemic influenza preparedness: the critical role of the syringe." ''Vaccine'' 24(24):4874–4882 (2006).</ref>
47<ref name="iso7886">ISO 7886-1:2017, ''Sterile hypodermic syringes for single use — Part 1: Syringes for manual use''. International Organization for Standardization.</ref>71<ref name="iso7886">ISO 7886-1:2017, ''Sterile hypodermic syringes for single use — Part 1: Syringes for manual use''. International Organization for Standardization.</ref>
+72<ref name="iso7864">ISO 7864:2016, ''Sterile hypodermic needles for single use — Requirements and test methods''. International Organization for Standardization.</ref>
48<ref name="iso9626">ISO 9626:2016, ''Stainless steel needle tubing for the manufacture of medical devices — Requirements and test methods''. International Organization for Standardization.</ref>73<ref name="iso9626">ISO 9626:2016, ''Stainless steel needle tubing for the manufacture of medical devices — Requirements and test methods''. International Organization for Standardization.</ref>
+74<ref name="ppdeadspace">PeptidePedia community device-measurement tally, 2026 (self-reported, uncalibrated balances, protocol not controlled; weak evidence — see [[Project:Sourcing_guidelines]]).</ref>
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50{{DEFAULTSORT:Syringe dead space}}76{{DEFAULTSORT:Syringe dead space}}