Syringe dead space: difference between revisions
Diff·revision 2 → 3·11:42, 10 Sep 2025
Difference between revision 2 and revision 3 of Syringe dead space. 9 lines changed; the page grew by 780 bytes.
| Revision 2 — 16:15, 9 Sep 2025 Chromatokid (talk) consistent en dashes in ranges 1,818 bytes ±0 | Revision 3 — 11:42, 10 Sep 2025 Chromatokid (talk) add confidence interval 2,598 bytes +780 | ||
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| 11 | The quantity matters for two distinct reasons that are frequently conflated. First, the retained liquid is discarded with the device, so each injection consumes the nominal dose ''plus'' the dead-space volume; over the life of a reconstituted vial this reduces the number of doses obtainable. Second, if the dead space is occupied by air rather than liquid at the moment the plunger position is read against the graduations, and that air is subsequently expelled, the volume actually delivered is smaller than the volume indicated. The first effect is a wastage problem and does not alter the delivered dose; the second is a dose error and can be large.{{r|strauss2006}} | 11 | The quantity matters for two distinct reasons that are frequently conflated. First, the retained liquid is discarded with the device, so each injection consumes the nominal dose ''plus'' the dead-space volume; over the life of a reconstituted vial this reduces the number of doses obtainable. Second, if the dead space is occupied by air rather than liquid at the moment the plunger position is read against the graduations, and that air is subsequently expelled, the volume actually delivered is smaller than the volume indicated. The first effect is a wastage problem and does not alter the delivered dose; the second is a dose error and can be large.{{r|strauss2006}} |
| 12 | 12 | ||
| + | 13 | == Anatomy and terminology == | |
| + | 14 | A 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. | |
| + | 15 | ||
| + | 16 | Three cavities contribute: | |
| + | 17 | ||
| + | 18 | * the '''hub''', the conical or cylindrical space between the end of the barrel and the proximal end of the needle cannula, which in a Luer fitting is a substantial void; | |
| + | 19 | * the '''needle lumen''', the bore of the cannula itself; | |
| + | 20 | * the '''plunger-tip recess''', any concavity in the elastomeric or moulded tip that is not filled by the barrel end when fully advanced. | |
| + | 21 | ||
| 13 | == References == | 22 | == References == |
| 14 | {{reflist}} | 23 | {{reflist}} |