In my role at Sentec, I have the privilege of working closely with care teams across the country as they implement and optimize the use of transcutaneous CO₂ monitoring in their units. One of the most common—and often overlooked—topics I find myself returning to is the importance of using Contact Gel when applying the Sentec V-Sign™ Sensor.
It may seem like a small detail, but the correct use of Contact Gel can significantly impact sensor accuracy, membrane integrity, and clinical workflow. Unfortunately, many teams have learned this the hard way—either through outdated or misguided training, trial and error, or system efforts to reduce consumable use.
Let me explain why this seemingly simple step matters so much.
When gel is missing, trust in the technology can falter
I often hear from care teams who initially struggled with unreliable values or frequent sensor issues only to later realize that they weren’t applying the sensor as designed. In a recent Q&A published in Neonatal Intensive Care, Mark Schorr, RRT, from Woman’s Hospital in Baton Rouge reflected on the challenges they faced during their initial implementation of transcutaneous monitoring:
Read the full Q&A with the team at Woman's Hospital
In that case, it wasn't the monitor that failed—it was the application technique (which was the result of improper guidance). Without the Contact Gel, the sensor could not deliver reliable data, and the team understandably lost trust in the measurements.
This experience is not uncommon. In fact, it's something I hear repeatedly from sites that have since made the switch to proper gel use.
What is contact gel? What makes contact gel effective?
Sentec’s Contact Gel is a water-based, skin-friendly formulation specifically designed to not only facilitate accurate transcutaneous gas diffusion, but to enable accuracy over time, striking the right balance of viscosity and wettability to last 8-12 hours. It serves several essential functions:
- Creates an air-tight seal between the sensor and the skin
- Maintains consistent thermal contact to support reliable measurements
- It serves as an additional buffer between the warmth of the sensor and the baby’s skin
- Supports adhesive ring integrity, improving sensor stability
Only 1–2 drops are needed per application. Each single-use vial contains more than the recommended amount, but overapplication can oversaturate the adhesive ring and reduce adherence. I often recommend applying the gel directly to the sensor (rather than the skin) if the patient is side-lying, to avoid seepage under the adhesive.
Insights from the field: lessons learned about using contact gel
Anne Geistkemper, MSc, RRT – NPS, from Rush University Medical Center, shared her own team’s experience in a Sentec clinical education webinar:
View a recording of Anne's Transcutaneous webinar
These observations are consistent with what I see across clinical environments: when Contact Gel is used consistently and correctly, sensor performance improves, troubleshooting decreases, and confidence in the data is restored.
Why saline isn’t a safe substitute
The instinct to use saline—often seen as a more accessible or cost-effective alternative—is understandable. However, saline is a sodium-based solution. When placed under a heated sensor, it evaporates, leaving behind sodium crystals that can:
Scratch and degrade the sensor membrane,
- Interfere with gas diffusion
- Lead to inaccurate readings
- Increase the frequency of calibrations and membrane changes
Sometimes teams have identified the evaporation issue on their own, noticing that the values correlate for the first 2 hours or so, then start to struggle, but will start to perform better if saline is reapplied. Unfortunately, we often don’t hear from those teams until they start having “adhesion issues” with their patient attachment rings, which is generally due to the constant wetting of the adhesive when reapplying saline.
Why ultrasound gel isn’t the right choice
While ultrasound gel may seem like a convenient substitute, it is not formulated for transcutaneous CO₂ monitoring. Unlike Sentec Contact Gel, ultrasound gel lacks the electrolyte composition that supports accurate gas diffusion.
Sentec Contact Gel has a higher water content than ultrasound gel which helps maintain a stable interface, encourages CO2 molecules’ journey from skin to sensor, optimizes accuracy, and prevents the monitoring site from drying out prematurely.
Ultrasound gel’s thicker, gummier viscosity can impair measurement accuracy, damage the sensor membrane, and even clog the Docking Station, resulting in frustrating error messages.
Accuracy, efficiency, and cost control
Some teams initially avoid using gel to reduce consumable cost—but in my experience, using gel reduces costs over time by:
- Preserving membrane life,
- Minimizing calibration frequency,
- Preventing sensor downtime or premature replacement,
- Reducing the need for unnecessary blood gases due to poor correlation.
- Avoiding constantly replacing attachment rings due to repeated wetting
More importantly, it improves workflow and clinical trust in the monitor while minimizing team frustration—a benefit that is difficult to quantify, but essential for safe and effective use.
Here’s how I discover that a NICU I’m working with is using saline or ultrasound gel instead of Sentec Contact Gel:
1. They say their readings aren’t accurate.
“The readings seem fine for the first two hours, and then the correlation drops off!”
Saline will give you reasonably good readings while it’s still wet and maintaining the seal between sensor and skin. But when it evaporates, the seal (and your correlating CO2 values) evaporate too.
2. They say their rings keep falling off.
Sometimes, NICU teams figure out #1 for themselves. However, what they often do instead of heading straight for Contact Gel is reapply saline to the ring whenever the reading seems off or the skin beneath the sensor seems dry. Unfortunately, that means they are continuously wetting the adhesive ring, and they won’t stay adhered to the patient as long as they would otherwise.
3. They’re experiencing a lot of docking station errors.
Docking station errors are most likely to be caused by placing poorly-cleaned sensors in the docking station – and using thicker, gummier ultrasound gel instead of Sentec Contact Gel is one way to end up with docking station problems.
4. They’re experiencing sensor errors and changing membranes more often than they should be.
Saline=salt. Salt = crystals. Crystals = scratches and dryness on your sensor membrane. Poor membrane condition is the primary cause for most sensor errors you might see on a transcutaneous monitor. Sentec Contact Gel is formulated to optimize gas diffusion and protect the sensor membrane, so they last their whole lifetime (~28 days).
In closing
Proper use of Contact Gel is one of the most important contributors to the successful implementation and use of transcutaneous monitoring. It's not just about following instructions—it's about enabling accurate, continuous CO₂ data that clinicians can trust.
When I work with teams that have struggled with sensor performance or correlation, one of the first things I ask is: Are you using the Contact Gel, every time? More often than not, this small adjustment makes a big difference.
If your team is new to Sentec—or if you're revisiting workflows—I encourage you to make gel usage a non-negotiable part of your protocol.
It's a small step with a big clinical impact.
In every NICU I've worked with, teams want the same thing: reliable readings, safe practices, and fewer disruptions to patient care.
When those outcomes aren't happening, it's often not the monitor that needs troubleshooting—it's the workflow. Consistent, proper use of contact gel may seem like a small adjustment, but it directly impacts everything from signal quality to adhesive wear to membrane lifespan. And more importantly, it supports the clinical trust and efficiency that make Sentec transcutaneous CO2 monitoring a valuable part of neonatal care.
