In a previous article, I wrote about one method for reducing pain from injections: using thinner needles.
You can read that article here → Needle Design Innovations for Less Painful Injections
The idea was that thinner needles cause less stimulation to the pain receptors in the skin, reducing the pain at the moment of insertion.
However, focusing solely on needle thickness is not enough to ensure a truly painless injection.
One essential factor involved is pressure.
In this article, I’ll explore the concept of pressure from a nursing perspective and examine how it plays a role in injections, IV infusions, and pressure ulcer care.
What Is Pressure?
Pressure refers to the force applied per unit area.
Pressure (Pa) = Force (N) ÷ Area (m²)
This means that the same amount of force creates higher pressure when applied to a smaller area.
For example, if you press your palm with your fingertip, it barely hurts. But if you press the same spot with your fingernail, it causes a sharp pain and may leave a mark.
This is because the force from the fingertip is spread over a wider area, resulting in lower pressure. In contrast, the force from the nail is concentrated in a smaller area, increasing pressure and creating a sharper sensation.
So, pressure can also be thought of as how concentrated a force is.
Injections and Pressure
To reduce injection pain, it’s important not only to use a thin needle but also to select a syringe with a narrow barrel whenever possible.
There are two types of pressure involved in injections.
1. Pressure When Piercing the Skin
The skin acts as a protective barrier and requires a certain amount of pressure to puncture.
Even when you press your fingernail into the skin, it doesn’t break easily. That’s because the force applied is not enough to generate the required pressure.
The smaller the area receiving the force, the greater the pressure becomes.
When a needle has a sharp tip, even a small amount of force can generate enough pressure to easily pierce the skin.
This reduces the force needed and shortens the duration of stimulation, helping to minimize pain.
Thinner and sharper needles reduce pain not just by stimulating fewer nerve endings, but also because they make penetration easier by concentrating force more effectively.
While the thickness of the needle is chosen based on the injection site and purpose, all needles are designed with a sharp tip to ensure smooth and low-pain insertion, thanks to this focused pressure.
2. Pressure When Injecting the Medication
Another important factor is the pressure required to push the medication through the syringe and needle.
This depends on both the inner diameter of the needle and the width of the syringe barrel.
Generally, the needle is narrower than the syringe. The greater the difference in diameter between the two, the more force is required to inject the medication.
So if the needle is very thin and the syringe is wide, more force is needed.
You might think a wide syringe is easier to push, but let’s revisit the formula:
Pressure = Force ÷ Area, or rearranged, Force = Pressure × Area
If the required pressure stays the same, the larger the surface area (such as the cross-section of the plunger), the greater the force needed.
Wider syringes require more force to generate the same pressure, and thinner needles require even higher pressure to allow the medication to pass through.
This can make the injection slower and increase the chance of hand movement, which may cause additional pain.
For this reason, selecting a smaller syringe according to the medication volume is ideal.
This is especially important in pediatric vaccinations, where children may cry or move due to pain or fear. Quick, steady injections help avoid complications.
In most facilities, physicians administer these shots, and I believe they also consider syringe size for this reason.
What It Takes to Truly Reduce Injection Pain
As we’ve seen, two types of pressure influence injection pain:
- When piercing the skin: A sharp needle concentrates force onto a small area, allowing the needle to penetrate more easily and reduce pain.
- When injecting the medication: A thin needle requires higher pressure, and a wide syringe requires more force to generate that pressure.
So, simply using a thinner needle is not enough. The combination of needle and syringe should be chosen based on the medication volume and purpose.
Understanding these mechanics allows us to design and perform injections that minimize patient discomfort.
IV Infusions and Pressure
Pressure also plays an important role in IV therapy.
One key task for nurses during IV infusions is managing the flow rate (drip speed).
The infusion speed is determined by the drug and the patient’s condition and must be adjusted to deliver the correct volume over a set period.
Some infusions are delivered using a pump for precision, but many rely on gravity-based dripping, which requires manual adjustment.
If the drip finishes too early or too late, it may affect the patient and complicate handovers during shift changes.
This is particularly true at night, when staff numbers are limited. Having to explain why the IV finished too soon or too late can be stressful.
Even with careful monitoring, it often doesn’t go as planned.
One major factor behind this is the height of the IV bottle.
Water naturally flows from higher to lower points due to gravitational potential energy.
Hydroelectric power generation, for example, uses the height difference between upstream and downstream to create energy.
IV infusions work the same way. The height difference between the IV bottle (upstream) and the insertion site (downstream) allows the fluid to flow naturally.
The higher the IV bottle is positioned relative to the patient, the greater the potential energy of the fluid.
This energy translates into hydrostatic pressure, which pushes the liquid through the tubing.
So, placing the IV bottle higher increases pressure and speeds up the drip rate.
On the other hand, lowering the bottle weakens the pressure, causing the drip to slow down.
When patients move or the bottle is re-hung at a different height, the height difference can change, causing variations in drip speed.
Pressure Ulcers and Pressure
Pressure ulcers (bedsores) occur when the skin is subjected to continuous pressure that restricts blood flow, leading to tissue damage.
Unlike wounds caused by friction or trauma, pressure ulcers develop from the inside due to prolonged poor circulation.
Bedridden patients are especially prone to developing pressure ulcers on bony prominences such as the scapula, sacrum, or heels.
Sourse:https://www.robsonforensic.com/articles/nursing-home-bed-sore-expert
If you lie on a hard surface on your back, you’ll notice discomfort in these areas, as body weight concentrates on them and increases pressure.
Over time, this concentrated pressure impedes blood circulation, cutting off oxygen and nutrients and causing cells to die.
That’s why regular repositioning is essential for patients who can’t move on their own—to shift the pressure to different areas.
Using pressure-relieving mattresses, such as air mattresses, is also highly effective in preventing pressure ulcers.
These mattresses allow the body to sink in gradually, spreading weight across a wider surface.
This prevents pressure from concentrating on bony areas and helps maintain healthy blood flow.
Conclusion
Pressure is not just about how strong a force is—it’s about how concentrated that force is across a given area.
Injections, IV drips, and pressure ulcers are all closely linked to pressure in nursing practice.
By understanding how pressure works, we can improve the quality of care and better adapt to changing conditions—finding more meaning and interest in our work as nurses.
In upcoming articles, I’ll explore medical and care products related to pressure, such as syringes, air mattresses, and IV equipment.
Alongside this blog, I also use my nursing experience and growing knowledge of medical patents to write technical content and support product evaluation and market development.
If you’re interested in collaboration or learning more, feel free to contact me through the contact form.
References
Yutaka Okaniwa , Byoki ga Mieru Vol.14: Dermatology, 1st edition, 2020, Medic Media Co., Ltd.
Koichi Ogawa, Illustrated Guide to Nursing Ergonomics, 2016, Tokyo Denki University Press
