Pediatric Annals

Special Issue Article 

The History of Home Cardiorespiratory Monitoring

Gary E. Freed, DO, FAAP, FACOP; Francis Martinez, PNP-BC

Abstract

Home cardiorespiratory monitoring has changed significantly since it was first introduced in the 1970s. It has improved from a simple alarm system to a sophisticated piece of equipment capable of monitoring the patient's electrocardiogram, respiratory effort, and oxygen saturations. In addition, the indications for using a monitor have also changed. The home monitor was initially used to reduce the incidence of sudden infant death syndrome (SIDS). Although there were several studies demonstrating the reduction of SIDS rates in communities where apnea programs existed, none was a prospective, double-blinded study or had adequate numbers to be clinically significant. Therefore, the American Academy of Pediatrics took the stance that monitors were not an effective way to reduce SIDS. However, when used appropriately, as part of a complete program (ie, the monitor is just one of many clinically based modalities), by a clinician with expertise in interpreting download tracings, home cardiorespiratory monitoring can be a useful, lifesaving, and economical tool to observe infants who are at increased risk of sudden death or increased morbidity secondary to intermittent hypoxia. [Pediatr Ann. 2017;46(8):e303–e308.]

Abstract

Home cardiorespiratory monitoring has changed significantly since it was first introduced in the 1970s. It has improved from a simple alarm system to a sophisticated piece of equipment capable of monitoring the patient's electrocardiogram, respiratory effort, and oxygen saturations. In addition, the indications for using a monitor have also changed. The home monitor was initially used to reduce the incidence of sudden infant death syndrome (SIDS). Although there were several studies demonstrating the reduction of SIDS rates in communities where apnea programs existed, none was a prospective, double-blinded study or had adequate numbers to be clinically significant. Therefore, the American Academy of Pediatrics took the stance that monitors were not an effective way to reduce SIDS. However, when used appropriately, as part of a complete program (ie, the monitor is just one of many clinically based modalities), by a clinician with expertise in interpreting download tracings, home cardiorespiratory monitoring can be a useful, lifesaving, and economical tool to observe infants who are at increased risk of sudden death or increased morbidity secondary to intermittent hypoxia. [Pediatr Ann. 2017;46(8):e303–e308.]

In 1963, Warren Guntheroth noted at the International Conference on Sudden Infant Death Syndrome (SIDS) that “Many children come into the emergency room with apparently minor respiratory infections. They develop apnea and marked bradycardia, then they are resuscitated and survive to live normal lives. I wonder if it would be fair to bring up for consideration the fact that this syndrome (SIDS) may be reversible if it is caught in time.”1 This quote provided the conceptual basis for providing continuous surveillance at home for selected groups of infants “at risk” for SIDS. Infants considered at risk included siblings of infants who died of SIDS, premature infants (having clinical apnea and/or bradycardia), and infants who had an apparent life-threatening event (ALTE). By the end of the 1960s, a widely held theory indicated that infants who died of SIDS were essentially healthy except for the possibility of a minor benign acute illness.2,3

Home Monitoring Becomes “Mainstream” in 1970s

In October 1972, Alfred Steinschneider, who would become an internationally acclaimed researcher about SIDS, published a study in which five infants were evaluated.4 All infants had a number of prolonged apneas (defined as over 15 seconds), cyanotic episodes, and an increased frequency of short apneas during sleep that were captured on polysomnography; some events required vigorous resuscitative efforts. Of this group, two of the infants were thought to have died of SIDS and Steinschneider concluded “These data support the hypothesis that prolonged apnea, a physiological component of sleep, is part of the final pathway resulting in sudden death. It is suggested also, that infants at risk might be identified prior to the final tragic event.” After this article, home monitoring with so-called “apnea monitors” for the reduction of SIDS went “mainstream.” However, the two infants who supposedly died from SIDS were ultimately found (more than 20 years later) to be victims of infanticide.5 Thus, the conclusion of the article was based on an incorrect association between apnea and SIDS.

Initial Monitoring Equipment

The initial monitors consisted of a simple “toggle-bolt” on and off switch and lights to indicate respiration, QRS signal, and loose leads. If the monitor alarmed, the parent was to complete a log indicating which light was flashing, how many beeps did the monitor make, if there was any change in color or muscle tone in the infant, and if parental intervention was needed to stop the event (Figure 1). This monitor was widely used into the 1980s and until shortly after the 1986 National Institutes for Health (NIH) Consensus Development Conference.6

The original Healthdyne monitor (no longer in production). Note the toggle on and off switch.

Figure 1.

The original Healthdyne monitor (no longer in production). Note the toggle on and off switch.

Monitoring Controversies for SIDS in the 1980s

In 1986, the NIH held a Consensus Development Conference to determine the effectiveness of home monitoring in reducing the incidence of SIDS.6 An examination was conducted of the scientific studies, published and unpublished, as they applied to the effectiveness of home monitoring when employed for infants at high risk for SIDS, infants who had an ALTE, subsequent siblings of a SIDS victim, and premature infants. This review failed to identify any “…reports of scientifically designed studies of the effectiveness of home monitoring…”6 The panel also examined the annual SIDS rate and concluded that “evidence from several communities in which SIDS surveillance has been maintained for a decade or more indicates that annual SIDS rates vary from year to year, but have not declined perceptibly since the introduction of home monitoring.”6 However, the panel's report and conclusion did not accurately reflect the status of scientific information available at the time.

The data for the annual SIDS rate for the United States were published yearly in the journal Pediatrics.7–11 Contrary to the impression left in the NIH Consensus Development Conference report,6 an examination of the annual death rates reveals a slow but progressive decrease in the incidence of SIDS (1.525 deaths per 1,000 live births in 1980 down to 1.405 deaths per 1,000 live births in 1986).7–11 There were actually a number of studies that collectively suggested that home-monitoring programs, when employed for infants at risk for SIDS, were associated with a decreased incidence of SIDS.12,13 Unfortunately, the data supporting the use of monitors were obtained from clinical reports rather than from randomized, double-blinded studies and the data was not felt to be clinically significant. Thus, the conclusion of the “expert panel” and ultimately the position taken by the American Academy of Pediatrics (AAP) was that home monitoring was not effective in reducing the incidence of SIDS.14

Advances in Home-Monitoring Technology

Event Recording

Another finding of the NIH Consensus Development Conference panel was that “new technology that enables events to be ‘captured’ was needed.”6 Early reports using 24-hour Holter monitors and pneumograms showed little correlation with parental reports and what was actually happening. In 1981, Jeffrey et al.15 ran 24-hour tape recordings (Holter and pneumogram) on 45 infants and found that 44 of 45 apnea alarms were false in spite of the parental report log. In 1986, Krongrad and O'Neil16 evaluated 20 infants who were considered at risk for SIDS using an electrocardiogram (EKG)/heart monitor and found that 93 alarms that were felt to be real were actually false. What was most disconcerting was that parents began “vigorous stimulation” or cardiopulmonary resuscitation on 11of these infants despite the fact that the child was not truly having any significant events.16

In response to these studies, the NIH panel instructed manufacturers to produce monitors that could “capture” waveforms for further evaluation. Between 1987 and 1988, the first documented event recorders became commercially available. These event recorders captured “real-time” EKG and respiratory effort using transthoracic impedance. In addition, the monitor documented when the equipment was turned on and off, enabling the physician to determine if the monitor was actually used. In 1991, Steinschneider and Santos,17 using documented event recordings, confirmed that there was little correlation between parental reports and what was actually documented by the monitor. Despite this, many physicians who were observing infants on home monitors turned off the recording channels and used the equipment only as an alarm system, not using the potential of being able to visualize the actual EKG tracings and respiratory effort (oral communication with the Director of Sales for the manufacturer of the monitor, December 1996). Thus, the full potential of what could be accomplished with these home cardiorespiratory monitors was not recognized by many physicians.

Pulse Oximetry

In 1999, Poets et al.18 published research in which recordings of heart rate and chest wall impedance were analyzed in nine infants who had died at a median age of 4.8 months (range, 1–6 months) while attached to a memory monitor. The primary cause of the monitor alarm was bradycardia in all but two infants. Gasping was already present at the time of the first monitor alarm in three infants and occurred within 2.7 minutes shortly thereafter in four additional infants. Since gasping only occurs if PaO2 is less than 5 to 15 mm Hg, it is most likely that the seven infants who gasped at or shortly thereafter the first monitor alarm were already severely hypoxemic at that time. Given this information, the push started for monitoring saturations and not just apnea and bradycardia. In response, “smart” technology was developed to monitor heart and respiration activity simultaneously (Figure 2).

The SmartMonitor 2PS (Circadiance, Pittsburgh, PA) cardiorespiratory monitor with a built in pulse oximeter.

Figure 2.

The SmartMonitor 2PS (Circadiance, Pittsburgh, PA) cardiorespiratory monitor with a built in pulse oximeter.

Unfortunately, most insurance companies do not pay for both pulse oximetry and cardiorespiratory monitoring. The clinician is forced to pick one modality even though together they would provide an enormous amount of information. In addition, despite some manufacturer's claims to the contrary, based on personal experience, pulse oximeters used in the home have an enormous number of false alarms and many families simply stop using the monitor rather than live with the constant alarming.

Home Monitoring and SIDS Prevention

As monitoring technology has changed over the years, so has the reason for monitoring. Initially, the home monitor was developed to reduce the incidence of SIDS. However, published reports failed to show any decrease in the SIDS rate as the result of home monitoring and the official stance by the AAP is that home monitors do not reduce the incidence of SIDS.19 The AAP noted that “Studies have failed to document any impact of home cardiorespiratory monitoring for apnea and/or bradycardia on the incidence of SIDS. Given the lack of evidence that home cardiorespiratory monitoring has any impact on SIDS, prevention of SIDS is not an acceptable indication for home cardiorespiratory monitoring.”19

In May 2001, the results of the Collaborative Home Infant Monitoring Evaluation (CHIME) study were published.20 This study was designed to test the hypothesis that “preterm infants, siblings of infants who died of SIDS, and infants who have experienced an idiopathic apparent life-threatening event have a greater risk of cardiorespiratory events than healthy infants” when compared to normal controls. The study20 demonstrated that premature infants (regardless if they were siblings of an infant who died of SIDS, infants that had experienced an ALTE, or “healthy” premature infants), all had significantly higher rates of apnea and/or bradycardia than the control infants at 38 to 41 weeks gestation, but by 42 to 45 weeks, no group had a rate significantly higher than the reference group. It must be pointed out that six of the infants enrolled in the study died (rate of 5.5 deaths per 1,000 infants). Two of the six infants were diagnosed as SIDS deaths, two were consistent with SIDS but there was no death scene investigation, one died of a homicide, and one was undetermined.20

The lead author of the study specifically stated that “The CHIME study was…not designed to determine whether use of a monitor decreases the rate of SIDS.”20 Yet, within the same issue of journal in which the CHIME study was published, an editorial21 called for the elimination of home monitoring based on the findings of the CHIME study. “Nevertheless, this study (CHIME study) justifies a severe curtailing of home monitoring to prevent SIDS.”20 Another editorial also against home monitoring to reduce SIDS states22 “…a JAMA study which basically says that monitoring for SIDS is useless, and, if one reads between the lines, the parents have been sold a bunch of useless home monitoring equipment which can't monitor true incidences of SIDS should they actually occur.”

Home Monitoring as Part of a Comprehensive Program

Despite this claim, the Apnea Center at Children's Healthcare of Atlanta has had a different result. As of the beginning of 2016, the Apnea Center has observed 35,492 infants on home monitors. During the 20 years the Apnea Center has been in existence, we have had 145 deaths of which 17 were diagnosed as either SIDS or “probable” SIDS.23 Thus, the SIDS rate is 0.48 deaths per 1,000 infants. This rate is below the national average of 0.5 to 0.6 deaths per 1,000 live births and well below the Georgia rate of 0.83 deaths per 1,000 live births.24 In addition, the Apnea Center's postnatal mortality rate of 4.1 deaths per 1,000 is half of the state of Georgia's rate of 8.1 deaths per 1,000 live births (5.7 white, 12.4 African American, 8.1 overall).24 There is no evidence that this is due to the monitor alone, but may result from the fact that these infants are closely followed by the Apnea Center staff and are referred to their primary care provider or local emergency department at the first sign of “trouble.” In addition, safe-sleep recommendations are repeatedly reviewed and the families are encouraged to seek routine pediatric care including immunizations. Table 1 outlines the number of patients referred to the Apnea Center and the reasons.

Patient Referrals to the Apnea Center for Infants at Increased Risk for SIDS

Table 1.

Patient Referrals to the Apnea Center for Infants at Increased Risk for SIDS

The Benefits of Home Monitoring

Interruption of Prolonged Events

In 2004, Hunt et al.25 concluded that “Having 5+ conventional events (apnea and/or bradycardia detected on a home cardiorespiratory monitor) is associated with lower adjusted mean differences in MDI (mental developmental index) scores in term and preterm infants.” In the same year, another study26 concluded that “An increasing number of days that apnea was recorded (by documented monitoring and pulse oximetry) during hospitalization was associated with a worse outcome. Among the potential explanations for this finding is the possibility that multiple recurrent hypoxic (apnea) and bradycardic spells may cause brain injury.” Based on the literature available at that time, my (G. E. F.) thought was that if I could interrupt prolonged events (apnea and/or bradycardia), I could possibly mitigate the adverse effects of the hypoxia that would have ultimately developed. Thus, my focus of monitoring changed from SIDS prevention to “saving brain cells.”

Monitoring Information as a Diagnostic Tool

As we frequently used the monitors in patients who are hospitalized, or those recently discharged, we found the monitor to be an effective diagnostic tool for use in the home for the detection of sporadic episodes, which could be easily missed during a brief hospitalization. It was recognized that certain waveform patterns were typical of specific entities such as reflux. As early as 1999, Marcus and Hamer27 describe how isolated bradycardias (those not preceded by apnea), especially those associated with asystoles, may be diagnostic of gastroesophageal reflux. In our program, when we began looking at the monitor download tracings carefully, including running the tracing at “real-time” (25 mm per second), we could diagnose a whole host of abnormalities including supraventricular tachycardia (SVT), atrial flutter, first-, second-, and third-degree heart block, gastroesophageal reflux, and seizures (apnea in the presence of tachycardia, confirmed by full-video electroencephalogram done on these children to make final diagnosis of seizures). As previously reported,28 we also noted that many infants will present with a sudden increase in apnea alarms 12 to 24 hours before becoming clinically symptomatic with respiratory syncytial virus. The home cardiorespiratory monitor can provide the clinician with a wealth of information if he or she knows how to read and interpret the monitor download tracings. Without being able to look at the actual tracing, and having the ability to look at the actual EKG in real time, many clinicians have missed the true value of home cardiorespiratory monitoring.

Potential for Cost Savings

Finally, one of the major complaints about home cardiorespiratory monitoring is that it is used simply as a money-making modality;21 this is hardly factual. In fact, if used correctly, home cardiorespiratory monitors can save money. There is no standardization as to how long to keep premature infants in the neonatal intensive care unit (NICU). Darnall et al.29 attempted to define a minimal safe observation period between the time of the last apnea episode and discharge. They concluded that “otherwise healthy preterm infants continue to have apneas separated by as many as 8 days before the last apnea of prematurity.” Many nurseries will put infants that are otherwise ready to be discharged (taking feedings well, able to maintain their temperature, and growing) on a 5- to 7-day “apnea/bradycardia” watch.30 That is, they keep the child in the NICU for 5 to 7 days after the last documented episode of apnea/bradycardia. However, earlier discharge from the NICU even with 3 to 4 days of being event-free and then sending home on a monitor for 1 to 2 months would potentially be much more cost-effective.

Conclusion

Home cardiorespiratory monitors are used quite differently today than they were in the 1970s. With the addition of event-recording, the ability to remotely access information, and the use of pulse oximetry, the monitor can provide a wealth of information. In addition, the indications for monitoring have also changed from an attempt at SIDS reduction to surveillance of specific high-risk infants.

The AAP has taken the stance that monitors are not an effective way to reduce SIDS. However, they point out that home monitors can continue to play an important role in preventing adverse outcomes in specific infant populations considered high risk. In a position statement, the AAP does note that “There are other groups of infants for whom use of a home cardiorespiratory monitor may be warranted, not because of an increased risk of SIDS, but because of other factors that increase the risk of sudden death. Home cardiorespiratory monitoring may be justified to allow rapid recognition of apnea, airway obstruction, or respiratory failure.”18 The authors of this article also believe that bradycardia and other arrhythmias such as SVT should be included in this statement.

Although much maligned, the home monitor, when used appropriately as part of a complete program that clinically manages the patient, can be an effective tool. Home cardiorespiratory monitoring is a useful, lifesaving, and economical modality to observe infants who are at increased risk of death or increased morbidity secondary to intermittent hypoxia.

The future of home cardiorespiratory monitoring remains uncertain. Fewer young physicians are being exposed to the true potential of home monitoring, and more insurance carriers are refusing to pay for the equipment. The population of infants being monitored is decreasing; however, there continues to be a subset of infants who can benefit from early recognition of apnea, airway obstruction, respiratory failure, and/or cardiac arrhythmias.

References

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Patient Referrals to the Apnea Center for Infants at Increased Risk for SIDS

Time Period (August 1, 1998 to August 31, 2000) Time Period (February 11, 2015 to December 8, 2016)
Referral Reason Number of Patients Percentage of Total Referrals Referral Reason Number of Patients Percentage of Total Referrals
Apnea 1,409 54.3 Apnea 1,083 50
Prematurity 470 14.4 Footnote a -- --
GERD 293 11.3 GERD 391 18
SIDS sibling 125 4.8 SIDS sibling 78 3.5
ALTE 93 3.6 ALTE 175 8
Bradycardia 55 2.1 Bradycardia 301 13
Seizure 20 0.6 Seizure 30 1.3
Cardiac abnormality 14 0.5 Cardiac abnormality 8 0.3
Footnote a -- -- Feeding difficulties 129 5.9
Other 248 7.6 -- --
Total 2,727b 99.2c 2,195b 100
Authors

Gary E. Freed, DO, FAAP, FACOP, is a Professor of Pediatrics, Philadelphia College of Osteopathic Medicine-Georgia Campus; and a Professor Emeritus, Emory University School of Medicine. Francis Martinez, PNP-BC, is the Acting Clinical Director, Apnea Center, Children's Healthcare of Atlanta.

Address correspondence to Gary E. Freed, DO, FAAP, FACOP, 625 Old Peachtree Road, NW, Suwanee, GA 30024; email: garyfr@pcom.edu.

Disclosure: The authors have no relevant financial relationships to disclose.

10.3928/19382359-20170725-01

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