Sensor/Patch Operation

NOTE: For more detailed instructions on Sensor placement and operation, refer to the Sensor IFU in the Sensor 5-pack carton.


  • The Sensor/Patch should be removed prior to external defibrillation or an MRI scan.
  • Patients with sensitive skin should be careful when using the Sensor. It may cause discomfort, skin irritation, redness, itching, rash, or dermatitis. If the device causes pain or discomfort, it should be removed using the adhesive removal agent provided. If skin irritation persists after removal, patients should consult their healthcare provider.
  • Excessive sweating may limit wear duration. Avoid situations that may cause excessive sweating.
  • The Sensor/Patch electrodes should not contact other conductive equipment or electric ground prior to wear.
  • The Sensor/Patch is intended for single patient use.
  • The Sensor/Patch should not be applied to an open wound or to broken, damaged or irritated skin.
  • The Sensor/Patch is water resistant, but not waterproof. No swimming or immersion bathing.
  • Showering while wearing the Sensor/Patch is permitted. However, instruct the patient to keep total shower time brief and to avoid a continuous, direct water spray over the Sensor.
  • No modification of the Sensor/Patch beyond access to the Electronics Module is allowed. Modification may lead to inaccuracies in reported data or complete loss of data.
  • Replace the Sensor/Patch if it peels off completely; do not reapply (it is meant for one-time use).
  • Do not use the Sensor/Patch if it or its immediate packaging appears damaged or if it is not activated within 15 minutes of application.
  • No creams or lotions should be applied in the application area immediately prior to use of the Sensor/Patch.
  • Store the Sensor/Patch at controlled room temperature.
  • The Sensor/Patch does not replace direct communication between the patient and their health care provider.
  • The Sensor/Patch data should be used along with all other clinical data and exams for a diagnosis.
  • The Sensor/Patch will not summon emergency response in the event the patient needs help.
  • The patient should talk to their health care provider immediately if there are any concerns or changes in condition.

Pouch Contents

(1) Cardea SOLO™ ADX S400 Wearable Sensor/Patch with top three protective paper elements removed.

(1) Application Template, (1) Patient Diary and, (1) Skin Prep Materials


Description automatically generated

Sensor/Patch – Getting Started

The Sensor is a small, lightweight, patch-style, single-use cardiac recorder, designed for ambulatory collection of electrocardiographic (ECG) data continuously for up to 10 days Figure 3.1 illustrates the key elements of the Sensor.

Figure 3.1. Key elements of the wearable Sensor/Patch

  • The button records and notes patient events. At start-up, a green light blinks for a self-test. If there is a fault, a red light appears for 30 seconds and shuts down.
  • The Sensor/Patch checks patient connection and shuts down if there is no connection. If connected, the green light blinks for 10 seconds in sync with the patient’s heartbeat for successful activation.
  • Following a successful activation, each additional button push will repeat the sequence of re-learning the QRS, followed by Green light blinking synchronous with the patient’s heart beat.
  • The Sensor/Patch stops after 10 days of running due to full memory and a slow, 30-second blinking Red light signals a shutdown or device failure resulting in no ECG data recording.

The Electronics Module is housed under a styrofoam cover that provides environmental protection from ingress of solid foreign objects and water. At the conclusion of the monitoring, the cover may be peeled-back and the Electronics Module removed for data transfer – see below. 

  • Do not remove the foam cover until the monitoring period is complete to prevent data loss from premature removal or environmental protection damage.
  • Ensure properly prepared skin before applying the Sensor to prevent poor adhesion and shortened wear duration.
  • Poor adhesion may result in a poor quality ECG recording and reduced diagnostic information available in the Physician Report.
  • If the Sensor/Patch electrode lifts from the skin, the patient should apply firm but gentle pressure to the affected area. If the Sensor will not re-adhere, health care provider assessment is necessary.
  • The useful life of the ECG electrode hydrogel becomes limited (use within 15 min) if the Sensor is removed from its pouch.
  • Remove the Sensor/Patch from its pouch during the same session as patient attachment. The degraded electrodes may result in a poor quality ECG recording and reduced diagnostic information available in the Physician Report.
  • The Sensor/Patch will return to its as-shipped state to conserve battery if it is activated and does not detect an ECG signal.
  • Leave the release liner in place until placement on the patient’s skin to avoid unintended conductive surface contact with the electrodes.

Sensor/Patch Placement

Sensor placement options are shown in the below Figure 3.2.

Figure 3.2. Placement options.

  • Option 1A placement, in the upper left quadrant, is the preferred location and orientation. The leads are aligned with the orientation of Lead I and aVF in a 12-Lead recording. For some patients it may be more comfortable to position the sensor as shown in 1B.
  • NOTE: In large BMI individuals, to avoid folding and distortion of the Sensor as the skin folds, it may be necessary to position the Sensor higher on the chest, in the 1st or 2nd intercostal space, and closer to the sternum.
  • NOTE: In individuals with dense breast tissue and or implants, it may be necessary to modify Sensor/Patch placement by moving it toward the collar bone, slightly more medial and in a horizontal position (1B).
  • For patients with a narrow thorax, and for pediatric patients, Option 2 may be preferrable, with the Sensor centered on the sternum and positioned in a horizontal orientation.
  • Use of the Sensor/Patch on individuals with an anterior axillary spacing of less than 6 inches (~15 cm) is not recommended.
  • Remove Sensor/Patch from pouch. Do not remove adhesive backing liner. Use application template to prep skin and place Sensor. Mark target position for minimal shaving and electrode placement to reduce electrical prep. Follow outlined application process.

Use the Application Template to locate and prepare a spot 1 inch larger than the Sensor/Patch. Shave or clip hair if necessary. Clean the area with alcohol from the Skin Prep Materials to remove oil or lotion and let dry for at least 30 seconds.

Figure 3.3. Using the Application Template to position the Sensor/Patch.

  • Place the Application Template against the skin in the desired placement area as illustrated in Figure 3.3. Use a pen to mark the skin. X’s to mark electrodes (holes) and dots or a short line to mark the border of the sensor where indicated on the template. Discard Application Template.
  • The outer most skin layer, the stratum corneum, consisting chiefly of layers of dead flattened non-nucleated cells filled with keratin, often acts as an effective electrical barrier for ECG monitoring. Good trace quality requires gentle removal of this layer before application of the Sensor. Use one of the skin abrasion items to remove dead skin in the areas marked as the location of the electrodes.
  • Wipe off the placement area with the gauze pad.
  • Turn the Sensor/Patch upside down. Holding it from the foam covered electronics module, carefully remove the two clear plastic liners covering the adhesive.
  • Position the Sensor/Patch over the prepared chest placement area, aligning the edges of the sensor with the edge marks placed on the skin using the template, then press it down.
  • Gently press down again in the middle and all around to make sure the Sensor/Patch is firmly attached, lying smooth and flat across the chest.
  • Remove all three top paper liners from the Sensor/Patch, gently and slowly pulling each tab. Take care not to twist or pull too hard.
  • Patient Position: The Sensor/Patch contains a 3-axis accelerometer designed to monitor patient position (supine vs upright) during the wear period. The system determines the orientation of the sensor from the first three minutes of the recording. The patient should be in a comfortable standing or sitting position when the sensor is activated and remain upright for three minutes.
  • Press the Sensor/Patch’s button. The indicator will rapidly blink green, pause and then flash green in cadence with the heartbeat for 10 seconds. The ECG acquisition sequence has started.
  • It is extremely important to note the date and time of activation of the Sensor/Patch since the timing of events is computed from this information. Cardea SOLO™ ADX S400 Software also analyzes sleeping versus wake intervals and it is helpful to note the patient’s normal time of onset of slumber and awakening. Record the date and time of activation of the Sensor/Patch on the patient’s record.

NOTE: If you do not see the light sequence described above, see the Troubleshooting section (Section 3.9).


  • The SOLO CRV software tool or APP is supported on Android and iOS (iPhone or iPad) Smart Devices.
  • The primary purpose of SOLO CRV is to confirm correct application and activation of the Sensor.
  • When the Patient Event button is pressed the Sensor broadcasts 30 seconds of the ECG trace data using Bluetooth communications.
  • SOLO CRV displays both leads of the ECG signal and supports saving the rhythm image as a PDF picture file on the Smart Device.

Application Installation

TBD – will be a web URL to download / install hosted on Google Play.

Adding Demographic Information

When the user starts SOLO CRV on their Smart Device the following screen is displayed:

The user may enter the Patient’s Name and Birthdate, and the Physician’s name and contact information. Additionally, SOLO CRV filters and removes AC line noise from the recording. The default filter setting is 60 Hz (US). Outside of the US, the line frequency may be 50 Hz.

The entry of the demographic and physician information is optional. The user can bypass this step and activate the Smart Device to start scanning for the Sensor’s Bluetooth signal – Click Start Scanning. Next, click the Sensor Event Button – SOLO CRV will pair with the Sensor and begins display of the ECG trace data.

Figure 3.4. Demographic data entry.

Rhythm Review

Once the Sensor and SOLO CRV are paired and the ECG data are being transmitted, the SOLO CRV screen will transition to the below.

Figure 3.5. Real-time display of the ECG data.

Check Sensor serial number and patient name displayed on top left of screen. Verify it matches Sensor serial number. Use arrows on left to adjust trace amplitude. “Exit” button terminates SOLO CRV, “Stop Running” ends Bluetooth but saves ECG data. Sensor stops broadcasting ECG data after 30 seconds. SOLO CRV computes heart rate and transitions.

Figure 3.6. Save Image.

Finally, the ECG image, including the demographic, heart rate and date/time labeling, can be saved as a PDF image (“Save Image”) on the Smart Device. The “Exit” button will close SOLO CRV without saving the image.

Wearing Instructions

  • The Sensor/Patch is intended to always be worn during the monitoring period, including while showering. The use of standard soaps and cleansers is allowed. Do not use lotions in the placement area.
  • The patient should not remove the Sensor/Patch unless skin irritation or an allergic reaction (e.g. hives) develops.
  • The patient must press the button when experiencing Sensor/Patch-prescribed symptoms for a patient trigger. Relax for 30-60 seconds before pressing the button for a clean ECG recording. Solo ADX searches for abnormal events backwards from the trigger.

Figure 3.7. Activating the patient trigger on the Sensor/Patch.

  • This records a notation in the data indicating the patient felt a symptom.
  • The Sensor/Patch will flash a green light in cadence with the heartbeat for a short duration after the button press.
  • The patient should use the Patient Diary to document activities and symptoms that accompanied their decision to press the button.

Recommendations for Patient Use

  • The patient is expected to wear the Sensor/Patch continuously for up to -10 days or until the end of the prescribed monitoring period.
  • The patient should not remove the Sensor/Patch for showering or sleeping or any other activities of daily living.
  • The patient should not immerse the Sensor in water (i.e. swimming or bathing in a tub) as this may affect the adhesive longevity.
  • The patient should keep total shower time brief and avoid a continuous, direct water spray over the Sensor/Patch.
  • If the Sensor/Patch should start to peel off before the end of the monitoring period, the patient should allow it to dry, if wet, and then press it back on to the skin, smoothing down any wrinkles. If the Sensor is still not adhering to the skin, the patient should contact their health care provider.
  • If the patient starts to significantly itch, experience significant allergic symptoms (e.g. hives), or be otherwise uncomfortable, the patient should remove the Sensor and contact their health care provider.
  • Give the patient the pouch and diary. If they need to remove the Sensor/Patch, put it on paper, store it in the pouch, and call the doctor.  
  • When handling a Sensor that has been worn by a patient use appropriate handling procedures (e.g. gloved hands).

Completion of Monitoring and Removal

  • When the monitoring period is complete, remove the Sensor from the patient.
  • Lift skin by Sensor and peel adhesive off slowly. Use petroleum jelly or adhesive remover wipe for easier removal.
  • Place the Sensor, adhesive side down, onto any appropriately sized piece of paper.
  • Pull upwards on the tab of the foam cover to remove it (see Figure 3.1).
  • Remove the Electronics Module from the adhesive attaching it to the bottom layer of the Sensor.
  • Discard everything except the Electronics Module, according to local regulations. The Electronics Module contains the patient’s ECG recording and will be used in a subsequent step.
  • Remove any residual adhesive from the patient’s skin. Rub petroleum jelly or baby oil over the residual adhesive and let sit for a minute. Use a tissue to wipe off the jelly or oil with the adhesive. Repeat as necessary.
  • There may be some residual redness and a slight odor around the area from which the Sensor is removed. This is normal and should disappear within a few days. If there is persistent redness accompanied by increased itching, the patient should contact their health care provider.
  • Do not expose the Electronics Module to moisture prior to or during the transfer of the ECG Recording.

ECG Retrieval

On the top surface of the Electronics Module is the Sensor/Patch ID label (see Figure 3.8 below). Use this information to associate or to confirm association of the Electronics Module with the patient chart. Copy the Sensor/Patch ID serial number (if not already there) onto the Patient Diary if a diary has been filled out by the patient.

Figure 3.8. The exposed Electronics Module following removal of the foam cover. The barcode uses the GS1 standard format.

  • Use the Smart Cable and Cardea SOLO™ ADX S400 Software to retrieve patient ECG information for the monitoring period, as discussed in the following sections.
  • After retrieval of the patient’s ECG and completion of the final report, the Electronics Module may be discarded.

NOTE: All portions of the Sensor/Patch are single use, disposable. It contains a Lithium battery. Do not incinerate. Recycle or dispose of this device according to your local regulations.


Problem: Light sequence does not occur as expected at start of monitoring period.

  • The Sensor/Patch must detect a valid ECG signal for recording to start.
  • Make sure the Sensor is properly positioned and adhered to the patient.
  • Press the Sensor’s button. It is possible that ECG recording did start, but that the confirmatory flashing green light was not observed. If recording is in progress, the light will flash green in cadence with heartbeat for a short duration and then extinguish.
  • Ensure electrodes are firmly attached to patient by pressing down and smooth over the electrodes. Allow electrodes to warm-up to body temperature for 3-5 minutes and try again to activate the Sensor.
  • If after trying to activate the Sensor/Patch twice, the expected light sequence does not occur, remove the Sensor and use a replacement.

Problem: The Sensor/Patch starts to come off the skin before the end of the monitoring period.

  • The patient should apply firm but gentle pressure to the Sensor over the area that has lost adhesion.
  • If the Sensor/Patch will not re-adhere, health care provider assessment is required.

Problem: Light does not flash upon button press during monitoring period.

  • Check to see whether the flashing green light is visible after a button press in a dark room.
  • If no light is observed after a button press, remove the Sensor/Patch and contact your health care provider.

Problem: The Sensor/Patch is difficult to remove.

  • Lift one edge of the Sensor/Patch and put an alcohol wipe in the space between.
  • Slowly peel the Sensor/patch off, using an alcohol swab or wipe on the skin.
  • If there is still difficulty removing the Sensor, use petroleum jelly or baby oil. An adhesive remover wipe may also be used.

Cardea SOLO™ ADX S400 Software includes administrative tools to customize the system for several clinic specific default settings and for creating individual User accounts.