Cardiorespiratory Monitoring
M. Kabir Abubakar
CARDIAC MONITORING
Monitoring of heart rate, oxygenation, and respiration is necessary to ensure physiologic stability for most infants in the neonatal intensive care unit (NICU). To be effective, monitoring needs to be continuous, noninvasive, accurate, and resistant to movement with few false alarms in both spontaneously breathing infants and those needing respiratory support. Progress in microchip and computer technology has facilitated the development of bedside monitors that can integrate multiple monitoring parameters into a single system. This chapter covers the fundamentals of cardiac and respiratory monitoring.
A. Purpose
1. Provide reliable, continuous, noninvasive, and accurate monitoring of neonatal cardiac activity
a. Provide trends of heart rate over time
2. To allow continuous evaluation and surveillance of critically ill neonates
3. To provide early warning of potentially significant changes in heart rate by identification of heart rates above or below certain preset alarm limits
B. Background
1. Electrical activity of the heart is detected using impedance technology via skin surface electrodes (3).
2. The low-level electrical signal is amplified and filtered to eliminate interference and artifacts.
3. The electrical signal, defined in millivolts, is displayed as an electrocardiogram (ECG) tracing.
4. R-wave detection from the QRS complex is used to calculate heart rate.
5. The typical three-lead configuration (i.e., leads I, II, III) provides alternative vectors for ECG analysis.
C. Contraindications
None
D. Limitations
1. The three-lead ECG is most useful for long-term continuous cardiac monitoring; more detailed cardiac evaluation (i.e., assessment of hypertrophy or axis) or the identification of abnormal cardiac rhythms will require complete 12-lead ECG with rhythm strip.
2. Close proximity of electrodes in extremely small infants may interfere with signal detection.
E. Equipment
Hardware—Specifications
1. The monitoring system should have the appropriate frequency response and sensitivity to track the fast and narrow QRS complex of the neonate accurately
2. Heart rate is processed on a beat-to-beat basis with a short updating interval
3. Default heart rate alarm limits should be tailored to the neonatal population
a. Low heart rate (bradycardia) limit of 100 beats/min (Note: Some term infants may have resting heart rates of 80 to 100 beats/min, requiring lower bradycardia alarm settings)
b. High heart rate (tachycardia) limit of 180 to 200 beats/min
4. Monitor displays
a. Cathode-ray tube (CRT)
(1) Has high resolution and definition
(2) Display can be either color or monochrome and more easily seen from different angles. CRT displays are no longer in common use
because of the improved quality and resolution of liquid crystal displays (LCD)
because of the improved quality and resolution of liquid crystal displays (LCD)
b. LCD
(1) Flat, thin display monitor
(2) Now have improved resolution for fast and narrow QRS complex of the neonate
(3) Back-lighting is necessary for viewing in lowlight environments
(4) Unlike CRT, viewing angle is critical
5. Heart rate displayed as alphanumeric part of waveform display or in a separate numerical display window
6. Recorder (optional)
a. Electronic memory
(1) Real-time ECG
(2) Delayed ECG—stored retrospective display used primarily for review of a short time interval prior to and during the occurrence of an alarm. Many systems now have the ability to store information (both numerical data and waveforms) for extended periods of time (up to 7 days) for later review
b. Printed record of ECG trend information
(1) Typically used to document selected segments of ECG tracings such as periods associated with alarms or abnormal rhythms
(2) Monitors may have dedicated printers (often integrated into monitor cases)
(3) Central monitoring stations can provide remote access to information from all networked monitor units with printing capabilities
 FIGURE 9.1 Typical multiparameter neonatal bedside monitor. (© 2019 GE Healthcare. All Rights Reserved.) |
a. Transport monitors typically smaller and battery powered
b. Similar capabilities regarding parameter availability, but monitor specific
 FIGURE 9.2 Typical multiparameter neonatal transport monitor with integrated printer. (Courtesy of Royal Philips.) |
c. Some monitors now have the ability to have modules that can be removed from the main monitor and used for transport then plugged back into the main monitor to allow for continuous recording without loss of memory data during transport.
Consumables—Specifications
1. Disposable neonatal ECG electrodes
a. Patient contact surfaces of electrodes are coated in adhesive electrolyte gel, which acts as conductive medium between the patient and the metal lead while preventing direct patient contact with the metal.
b. Typical commercially available neonatal leads incorporate silver-silver-chloride electrodes directly onto paper, foam, or fabric bodies with integrated lead wires; these are available in different sizes and forms designed for use in neonates of different gestations.
c. Less commonly, adhesive electrode pads are separate from lead wires, which connect to the electrodes via clips.
d. ECG limb plate electrodes may be used in extremely low-birth-weight infants with a small chest surface area and sensitive skin and when the application of chest leads would interfere with resuscitation or the performance of other procedures. Use of electrode gel as a conductor at the skin interface (rather than alcohol pads) is imperative in such cases. All neonatal leads should be latex, phthalate, and mercury free.
2. Characteristics to consider in electrode selection
a. Adherence to skin of an active infant
b. Quality of signal attained
c. Minimal skin irritation
d. Ease of removal using water or adhesive remover without damage to or removal of skin
e. Performance in the warm, moist environment of an infant incubator
f. Adhesive-skin interaction under overhead infant warmers
3. Lead wires and patient cable
a. All cables should be clean and the insulation should be free of nicks or cuts.
b. Lead wires should lock or snap into the patient cable, preventing easy disconnections.
c. If using electrodes that attach via clips, use infant/pediatric lead wires with small electrode clips—standard adult-size clips will place too much torsion on the infant electrode, tugging on the skin, and possibly peeling off the electrode.
F. Precautions
1. Do not leave alcohol wipes under electrodes as conductors.
2. Do not apply electrodes to broken or bruised skin.
3. Avoid placing electrodes directly on the nipples.
4. Select the smallest appropriate/effective electrode for patient monitoring to minimize skin exposure and limit potential complications from irritation/adhesives.
5. Do not apply electrodes to clear film plastic dressings—dressing will act as an insulator between the skin and the electrode.
6. To avoid skin damage, do not use fingernails to remove electrodes.
7. Secure the patient cable to the patient’s environment to prevent excessive traction.
8. Use only monitors that have been checked for safety and performance regularly—usually indicated by a dated sticker on the monitor from biomedical engineering.
9. Do not use monitors with defects such as exposed wires, broken or dented casing, broken knobs or controls, or cracked display.
10. Monitor alarms should prompt immediate patient assessment.
a. Note alarm indication (i.e., tachycardia or bradycardia).
b. Treat patient condition as necessary or correct the source of any false alarm.
c. If alarm is silenced or deactivated during the course of patient evaluation, it should be reactivated prior to leaving the patient’s bedside.
G. Techniques
1. Familiarize yourself with the monitor prior to patient use
2. Electrode and lead wire placement: Although you should refer to the monitor manufacturer’s placement instructions, general electrode placement guidelines follow
a. Skin preparation: Skin should be clean and dry to provide the best electrode-to-skin interface.
(1) Wipe skin with an alcohol pad (use a normal saline swab in extremely low-birth-weight infants with sensitive skin) and allow to dry thoroughly
(2) Avoid the use of tape to secure electrodes—for optimal performance and proper electrical interface, electrodes must adhere directly to skin
b. Basic three-lead configuration for electrode placement (for electrodes with integrated lead wires) (Fig. 9.3)
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
