6: What can enable depleted Rebreathing

Chapter 6: What situations or stressors could enable depleted rebreathing to occur?

All of the aforementioned, the unresponsive regulatory breathing system, the underdeveloped lungs, and the relative size of lungs compared to breathing passageways, the strength and development of the early infant, in and of themselves, either combined or by themselves, should not cause SIDS. They only make it possible for SIDS to occur. What are needed to occur are other factors (stressors), situations or scenarios that work in concert with those conditions to cause SIDS. I will now turn to those external factors (scenarios) and issues that may bear upon an early infant such that depleted rebreathing can take place resulting in SIDS or exceptionalities. Let’s look at these individually to see how these could take place, and how harmful rebreathing could be considered in every case to be the cause of SIDS.

The Back to Sleep Program (preventing obstructed breathing)

The first to consider is perhaps the most well known. This is the situation where an early infant is placed or has turned face down into their bedding or a soft blanket or toy such that their breathing is restricted. It is believed that this restricts the quantity of fresh air that a child inhales. The child continues to inhale reduced quantities of oxygen and this eventually results in brain cell damage and a SIDS death. In these cases most believe that it is depleted rebreathing that has resulted in death.

Anyhow, from the general consensus that SIDS deaths can be caused by depleted rebreathing into soft bedding or toy, it has become advisable that early infants be placed on their backs for sleeping (or pretty well at all times). By placing the child on their back, they avoid the possibility of the child’s mouth or nose from being obstructed by the bedding or toy. I, as well as others, believe that the child should also have some side and tummy time (supervised). The practice of having early infants sleep on their backs has resulted in about a 40% to 50% reduction in the incidence of SIDS. Quite remarkable!

Some have voiced concern that having an infant continually lie on their backs will cause the child to have a flat spot on the back of their heads. This flat head problem is called positional plagiocephaly. Serious cases of positional plagiocephaly (flat head or mishappen head) have actually resulted in an asymmetrical shape to their head and misaligned facial features, as neck muscles continually pull to one side. The skull of early babies is very pliable, which makes flat head or plagiocephaly possible, but this pliability is also used to correct the problem. In mild cases, altering the sleeping habits of the baby and physical therapy can redress the problem. However, in more serious cases doctors will, as soon as possible, create a custom molded helmet which the newborn will wear for about 2 to 6 months for close to 24 hours per day. This has been very effective in reshaping the head back to normal. I believe it is prudent to give a child some supervised tummy time each day (as much as reasonable supervision allows). Parents should also be reminded that the back to sleep program needn’t be practiced past much one year of age.

Another reason that I recommend some supervised tummy time is that it gives the early infant an opportunity to develop their neck, back and arm muscles, as they work to try to lift their heads. This strengthening is important as it will give them the ability to protect themselves by moving should the need arise to reach fresh air. Part of the natural learning of an infant is experimenting, reaching out, and trial and error, all of which require freedom of movement. Also consider that a study in the journal Developmental Psychology citing a North Dakota State University, news release, Dec. 11, 2012, suggest that having an early infant sitting up will help with learning. Considering this, think of how negative it would be to restrict any infant’s movement, preventing them from the natural learning that takes place through exploring the world around them.

There has been speculation that the accumulation of carbon dioxide in thick bedding or stuffy can be a contributor to SIDS deaths. Because of this, it has been recommended that mattress be fitted with tightly fitted thin bed sheets which would be incapable of holding CO2. As well, lack of air circulation around the crib can also impact SIDS, therefore some air circulation is recommended. These suggestions often are part of the Back to Sleep program.

There can be some speculation that when an infant sleeps prone, face down on their tummy, the weight of their body may restrict their lungs, limiting the infant’s ability to breathe sufficiently (similar to the restriction caused by tight bindings), even though there is nothing obstructing their breathing. How the baby is lying down may curtail how effectively they can breathe, since their neck may be twisted awkwardly. If there is any validity that there is some possible danger to sleeping prone because of its restriction on the lungs, then the argument could be made that part of the success of the Back to Sleep program is due to the avoidance of pressure on the lungs, rather than for the avoidance of breathing into bedding or soft toy where the accumulation of CO2 and depletion of O2 could occur. This is just speculation that may warrant some study. I'm not convinced.

The authors Steven D. Levitt and Stephen L Dubner in their book Freakonomics suggest as convincing as they could that the recent decline in crime was due to the increase in abortions in the USA. Unfortunately they make a very far reaching assumption that only the worst in society get abortions, and that these abortions resulted in the elimination of many criminals. This is quite a judgement on those who get abortions. It suggests that those who didn’t get abortions in the past, but had to have the child, punished the child with abuse and neglect to the point that these children grew up to be criminals. The fact that any unwanted child, in the past and now, can be put up for adoption weakens this argument. The better assumption that I make is that the recent reduction in crime is due to the Back to Sleep program which resulted not only in a reduction in SIDS deaths, but more importantly also a reduction in learning disabilities and any neurological damage. It is this reduction in learning disabilities and neurological damage that has resulted in the improvement (reduction) in crime, as there has been a clear link between learning disabilities and crime.

Stressors where breathing is not obstructed

How could depleted rebreathing take place when their breathing through the mouth or nose is not obstructed by bedding or a fluffy toy? What I would like you to consider here is the weak nature of these early lungs and their relative size as I have already explained. Normally the lungs will get by, but if their breathing is restricted by swaddling or any type of pressure, this tentative ability could be compromised. Let’s look at these possibilities.


Perhaps the most widespread and age-old practice seen around the world is the practice of swaddling or binding an early infant. They get wrapped up like a little package. What is the need for this? Some may consider that a newborn will swing their arms around possibly hurting themselves or damaging their eyes with their nails. Some consider that it is to make the newborn feel secure. It is considered that babies that are swaddled tend to sleep better and longer, as they feel secure and are not aroused by the movement of their arms.

Some parents see this as a necessary practice in conjunction with the Back to Sleep program, helping to keep the child positioned on the backs. Therefore it may be considered as a preventative measure to reduce the risk of SIDS. I disagree as I believe that binding may increase the risk of a SIDS death. Unfortunately, many parents may be encouraged to bind their child, including their arms, so that they can’t roll over, fearing that if they turn over the child’s mouth might be forced into the mattress. The thinking here is that if their arms are bound, they couldn’t rollover to a face down position.

However, the tentative strength of an early infant’s lungs must be considered when wrapping a child in any type of material. A child that is bound too tightly may not have lungs that are strong enough to draw in sufficient fresh air, even if they are placed on their backs. This binding may be restricting the movement of their ribcage limiting how deeply the newborn can breathe. It is this restrictive nature of these bindings that concern me, as I believe that the bindings may restrict breathing to the point that depleted rebreathing can take place.

Alternatively, as an early infant becomes stronger, they might wiggle somewhat to move the swaddling, accidentally placing a portion of the blanket or sheet over their mouth and nose, restricting breathing. In these cases swaddling can be considered a risk similar to that of soft bedding or toys. My concern here is that some caregivers are unaware that the tightness of the swaddling is a potential danger and as a result bind the early infant even tighter. Although there are some benefits to swaddling, such as improved sleep for the baby (and sleep for the parents), how safely it is done is of significant importance.

My point is that the practice of placing a newborn’s arms in front of their body and applying tight bindings, may very well restrict breathing to the point that depleted rebreathing takes place (as their arm get forced down across their ribcage). Some may even bind their arms and hands for the purpose of preventing thumb sucking. I will have more to say about thumb sucking shortly.

Recently there has been a study in Quebec that has shown that a number of newborns suffered SIDS deaths while sitting in their car seats (these were particularly young newborns). My thinking here is that the bindings of the car seat (perhaps in addition to thick winter clothing) acted similarly to that of tight swaddling, preventing the lungs from breathing deeply enough. The depleted rebreathing that took place resulted in these SIDS deaths in my view. Also consider that clothing, in this case winter clothing, is often bought oversized such that the infant can grow into them (or are passed down from an older sibling). In this case it is very easy for a small infant to slip down in the clothing, such that their mouth and breathing is restricted, leading to rebreathing. I am not aware of the details of these cases, but I assume that these very early infants probably were wearing snowsuits or other outdoor clothing. These suits may not only have added to the pressure on their lungs, but also partially restricted air movement as their heads may have been tilted forward into their chests (or as the seat belt pushed the clothing up over their mouths). Parents need to be aware and reminded that the tightness of the belts in car seats should not be excessively tight.

We shouldn’t overlook the fact that many believe there is a connection between SIDS and overheating. Parents need to be aware that swaddling, tight binding and oversized clothing may all bear on this connection.


It has been observed that in many cases of SIDS there is evidence that the child suffered overheating. However, the relationship between SIDS and overheating is still not clearly understood. Did the infant suffer overheating which in turn causes the infant to suffer SIDS? Or did the infant suffer an incident of SIDS which in turn caused overheating. One possible connection could be that in the process of depleted rebreathing, the lack of oxygen and change in blood chemistry begins to damage brain cells and brain chemistry. When that occurs, if the brain cells that are involved with controlling core temperature become damaged or affected, the infant may begin to overheat. Therefore overheating can be an outcome of depleted rebreathing. If this is the case then overheating might be another potential sign (near-SIDS event) that SIDS may occur and that steps should be taken to prevent this from happening.

It is very possible that the brain stem system that regulates breathing also regulates the control of core temperature. If that is the case, then any sign of overheating could also be a sign that an early infant has a poor breathing regulatory system as well, and as such can be at greater risk of suffering a depleted rebreathing incident and SIDS. This might be the connection of SIDS to overheating. Perhaps overheating does not cause a SIDS death directly; however, these may often occur at the same time due to their connection to the brains ability to control breathing and temperature. Could a simple device that monitors temperature changes be an effective device to warn parent to arouse a child so that they avoid SIDS. Might be worth considering.

Synesthesia is a condition whereby an individual might hear colors or taste shapes due to cross wiring during early development. Is it possible that occasionally breathing and core temperature regulation get cross wired similarly in early infants such that a need for increased breathing due to excess CO2 results in increased heating instead, or vice versa, increased core temperature results in reduced breathing? Again finding a way to monitor unusual temperature changes (where a flu or virus is not suspected) may be an effective way of preventing SIDS tragedies.

Overheating may also be a reaction to toxicity or an infection about which I will discuss shortly.

Bed Sharing

There have been mixed findings when it comes to bed sharing and SIDS. For the most part bed sharing is now considered as a risk for SIDS. There are two ways that SIDS could occur due to bed sharing, covering or arm pressure. Parents need to be aware that if they sleep with their child, the tendency might be to place an arm or blanketing over the child so that they won’t roll over or roll off the bed. Or perhaps while asleep a parent may accidentally place an arm (or blanket) over their child. The first concern is that the added weight of an arm on a newborn’s chest may be excessive and limit the infant’s ability to breath, resulting in depleted rebreathing and SIDS. The second is that blanketing, if moved unknowingly over the mouth or nose of the early infant, may restrict breathing the same way as that of having an infant suffer a SIDS death due to having their mouth and nose blocked by bedding or soft toy. Individually or together these two stresses could cause depleted rebreathing and SIDS. It has been suggested that sharing a bed for nurturing is recommended, but not sharing a bed for sleeping purposes. Unfortunately it is hard not to sleep when you cozy up to your child. Be careful!

There is another possibility where an infant may be placed in a hollow of the bed or between two parents as a preventative measure so that an early infant won’t fall off the bed. These hollows or restricted microenvironments may limit the inflow of fresh air and can result in a deteriorating microenvironment that over time sees an accumulation of CO2 and depletion of O2. This may lead to depleted rebreathing. Conversely, depending on the situation, parental breathing or movement may even help circulate fresh air to their infant. You just never know. If you do have your child in your bed with you, be very cognisant of the need for continuous flow of fresh air to your child.

There is a known statistic that the occurrence of SIDS significantly increases after the first, second, and any subsequent child in a family. This could partially be due to the increased exposure to viruses that any sibling brings home, but also due to the increased chance that an early infant may experience an increase in bed sharing, the larger the family, the increased chance of bed sharing, particularly in poorer families who may have to share beds.


Is sleep a factor in SIDS deaths? We can’t overlook this possibility because SIDS is always preceded by sleep. That is why SIDS is often called crib deaths. These tragedies don’t occur in the middle of eating, crawling, laughing, crying, or other activities. Those deaths would truly be considered as “sudden” if they did occur. But how can sleep be playing a role? Is it possible that SIDS could occur just because the early infant was sleeping (without any airway or lung restrictions such as their mouth being blocked or their chest being bound too tightly)? As I have suggested, an early infant already has a tenuous ability to gain oxygen due to the aforementioned relative size of lungs, relative size of mouth and nose passageways, and a developing breathing control system. If during sleep their breathing rate decreases or is shallow due to inactivity, it is possible that this reduced breathing is insufficient to sustain adequate levels of oxygen in their lungs. Perhaps, but only if a weak breathing regulatory system doesn’t arouse the early infant or cause them to properly adjust their breathing rate. If their breathing regulatory system is functioning properly, then breathing should adjust and be adequate for the infant. But if their breathing didn’t adjust adequately during sleep, then it could lead to an inadequate supply of oxygen, leading to a SIDS death. Is it possible that the breathing regulatory system only malfunctions during sleep? Is it possible that they are sleeping too soundly to notice the discomfort in their lungs? This is pure speculation that the breathing regulatory system goes to sleep (or is less effective) when the child goes to sleep. This can’t be ruled out. But I don’t want parents to be in fear each time they place their child down to sleep. Babies need their sleep. Parents just have to ensure that while their baby is sleeping there is adequate air circulating in the infant’s environment. It’s as simple as that.

I believe that it is the stillness of the air and limited microenvironment that a baby is placed in that opens the possibility of harm to the infant. What do I mean by stillness of the air? I mean that babies are put to sleep often in cribs with bumper pads. The crib is most often placed against a wall, often in a corner, and there is no one moving around the room creating circulation by their movement, as the infants are left in a quiet room by themselves. The baby doesn’t move much itself. All of these conspire to limit air circulation, and increase the possibility of rebreathing. It brings us back to depleted rebreathing. It’s not so much the sleeping that could pose a threat, but the usual environments that the child is placed in for sleep. Knowing this, it become easy to reduce this risk by making sure that when an early infant is placed down to sleep there is no still air around the infant. Removing bumper pads in the crib, removing any toy or bedding that might restrict air flow, not having the crib next to a wall or corner, having the baby sleep on its back, having a small circulation fan keep air moving, these are all excellent ways to protect the baby.


Does crying have any connection to SIDS? When a child is crying they are breathing extensively and as such are getting lots of oxygen. What would worry me more is a child that doesn’t cry. This may be a child who is unresponsive to many stimuli including the discomfort of excessive carbon dioxide in the lungs, and are least likely to correct low levels of oxygen in the lungs and blood.

I don’t believe that there has been any statistics on this but it might be true that SIDS babies are also those that cry the least. Many parents buy monitors so that they can hear their child in the bedroom. This is perfectly fine if the parents are using it to notice when the child is stirring or crying so that they can feed them or change a diaper. But parents who use these should not assume that since all is quiet, the child is fine (although usually so), or the opposite. The sound of a child immediately before suffering a SIDS death is in all likeliness quietness or inactivity. I wouldn’t want any parents to think that quietness means that the child is automatically in danger either. Parents should use these monitors to help indicate when the child needs changing or feeding, not as a defence against SIDS. We know that a healthy child is quiet when they sleep, and a new born sleeps a lot. Parents only have to make sure that they have taken measures that would reduce the possibility of depleted rebreathing occurring by ensuring adequate air circulation as has been suggested.


Is there any relationship between illnesses (flues, colds, ear infections) and SIDS deaths? I believe that these are a significant factor. Due to the relatively small size of the child’s lungs and the weak nature of their developing lungs, any illness due to a cold, flu, infection,or allergy could reduce the child’s ability to breathe efficiently and make depleted rebreathing a greater possibility. Every precaution should be taken to avoid exposure to any illness. Any illness can weaken the infant to the point that they are suffering some level of depleted rebreathing. This can happen either by weakening the child’s muscles (including lung muscles) such that already tentative breathing becomes depleted, or by blocking nose passageways through sinus congestion (forcing breathing through the mouth which I believe is less efficient than that of breathing through the nose), or both.

A report out by the Lung Association of Saskatchewan states that 1 in 10 Neonatal Intensive Care Unit infants who have a diagnosis of chronic lung disease may suddenly die at home without apparent reason; and some of these were appropriately classified as SIDS deaths. Doesn’t this clearly point to the connection between breathing (and rebreathing) and SIDS? I believe so.

Any illness can increase the possibility that an infant can suffer depleted rebreathing that may result in a SIDS tragedy. Of course, these difficulties could be exasperated but other factors such as breathing into bedding or tight bindings (as a parent may try to comfort and protect the child while they are suffering the illness).

We cannot overlook the relationship between SIDS and overheating, as I have previously discussed. Often any child who suffers a flu or illness will do so with a fever; and we have to suspect that a fever may lead to overheating and its relationship to SIDS.

It has been reported that there is an increase in the case of SIDS during the winter months. Can this be due to the increased risk of flues, colds and infections, or is it due to the additional bedding that parents may apply during the colder months (or because the infant is ill)? I believe so for both reasons as both have an impact on depleted rebreathing which can lead to SIDS deaths. I believe the impact of getting a flu or cold is more significant than that of the additional bedding. Most (but not all) parents are now well aware of the dangers of bedding and would take care during the winter months as they would in the warmer season. However, parents have less control over flues and colds. Parents have little or no influence over having their infant avoid these diseases, other than have their infant avoid others who have a cold or flu which is a very good strategy if they are able to follow through. Parents should take any and every measure that would reduce the possibility of their newborn being exposed to any virus.

A number of studies have shown that there is an increase in SIDS for the second, third, fourth, and so on, child in a family. This factor may be called "birth order effect." I believe that the primary reason that there are more SIDS cases in younger siblings is that siblings expose any newborn to flues and colds to which they would not be otherwise exposed. This increased exposure increases the likelihood that they may catch a flu or cold and therefore potentially suffer a SIDS death. Statistics have shown that being a younger sibling increases the risk of suffering a SIDS death by a factor of two to three times. There is also the issue that siblings may be given the opportunity and responsibility to look after an early infant and these children are unaware of the dangers to early infants (bedding, toys, bindings, etc.). In addition to that issue is the increased opportunities for bed sharing which carries its own risk.

There also have been studies that show there is a higher rate of SIDS when early infants are left at daycare centers. This reinforces the theory that exposure to flues and viruses may contribute to the risk of SIDS. This could almost be predicted for the same reasons as that of being exposed to siblings (exposure to viruses, less attention, education of staff, etc.).

There may be a tendency to give the first born the most attention. The reduced attention to a second or any additional child is not neglect but simply due to the fact that having a baby is no longer a new experience, and that the new sibling must share its attention with any older sibling. The extra attention given the first baby may, just by the increased chance of attention, have any incident of depleted rebreathing interrupted, and as such this is partially why the first child has the least risk of SIDS.

I just want to be clear that I don’t think that any flu or illness causes SIDS directly, as this relationship has never been found. What I suggest is that any illness may indirectly lead to depleted rebreathing and this leads to SIDS deaths or learning disabilities. Again, assuring sufficient air circulation can protect the infant from these outcomes.


This is a reoccurring hot topic.

Immunization has often been considered as a potential cause of SIDS. Since I believe that depleted rebreathing is the cause of SIDS, I don’t believe that immunization causes SIDS; however, immunization may temporarily weaken a child’s breathing to the point that depleted rebreathing can take place, just as any flu or illness. Therefore there is a potential indirect association between immunization and SIDS through depleted rebreathing. Since I believe that any condition that potentially weakens the child’s breathing may result in depleted rebreathing that leads to SIDS, I believe that the practice of immunization of early infants, where advisable, should be postponed until the child is at least 12 months of age. Physicians should weigh carefully the risks of delaying immunization to a later date against the risks involved with immunization within the first few months.

Immunization has two opposing considerations. First, immunization could briefly weaken a child’s breathing putting them at a temporary risk. Secondly, immunization may protect the child from an illness that could be suffered while they are an early infant thereby protecting them from practicing depleted rebreathing and suffering a SIDS outcome. If the immunization is for a condition for which the child is not likely to suffer during the first year, then perhaps that immunization should be delayed. Is there any real need to immunize an early infant against a sexually transmitted disease such as Hepatitis B? I don’t know the answer to that, but if the risk is negligible, shouldn’t this immunization wait 12 months? Likewise, if immunization is for something that they are likely to suffer during the first months, then the immunization of course should proceed. Considering the increased risk due to exposure to siblings, daycare personnel and other children, having a flu shot might be a responsible consideration.

However, if a child is immunized within the first few months as they often are, parents and caregivers should be very vigilant during the hours and days immediately following that immunization to guard that depleted rebreathing does not occur. They should be aware of the fragile nature of the infant’s breathing during those days, and be extra cautious that the child’s breathing is not impaired in any way. Parents should also be vigilant to an overheating caused by their baby having a high temperature due to the immunization. As long as these precautions are taken and an adequate circulation of air is in place, depleted rebreathing would not take place and there should be no increased risk of a SIDS death due to immunization.

A study, published in Jama Pediatrics 2018, found that those who were already diagnosed with autism, were less likely to have all their vaccines later. This shows that there is still the fear by parents of children with autism that vaccines are the cause. This is truly unfortunate, because these parents are putting their child at risk, and all those who their children interact with. It's a small percentage, but nonetheless, they may be making these children ill.


Can SIDS be the result of an infection as proposed by Paul Goldwater (Goldwater P N; Sudden infant death syndrome: a critical review of approaches to research, The Woman’s and Children’s Hospital, North Adelaide, South Australia, 2005). He had found a protein, curlin, which can cause a toxic shock reaction in all of the SIDS cases studied. As curlin can be produced by the E. coli bacteria, perhaps SIDS is the result of a reaction to bacteria. Infants who died of SIDS while on medical monitors displayed a shock like process (is this another indicator that SIDS is not a sudden event but the end result of a longer process, and that it is observable). It is difficult to ignore this theory. However, the E. coli bacteria that produces the curlin protein was not present in all of these cases. The reason for this might be that there are other yet undiscovered bacteria which also produce curlin. This is entirely possible, but there appears to be a problem with accounting for reductions in SIDS by the Back to Sleep program or by the use of pacifiers. Because pacifiers can fall on the floor and pick up bacteria, wouldn’t they show an increase in SIDS deaths, not the 90% to 95% reduction that as been reported? If SIDS is only a bacterial infection, these other practices (sleeping on their backs or using a pacifier) should have no impact, but they do.

As I had mentioned before, there is little known about the process whereby depleted rebreathing and the subsequent lower O2 and higher CO2 leads to death. My suggestion is that lower O2 and higher CO2 results in changes to O2 and CO2 levels in the blood. This changes blood chemistry, which in turn may possibly produce curlin, and then this curlin causes a shock like reaction and death. This is just a theory. Be that as it may, it is still depleted rebreathing that leads to the eventual harm to the early infant.

Another question that arises is why the E. coli bacteria (or other bacteria) which produces this curlin, doesn’t do so in older infants and adults. This is unexplained. Perhaps this is because older infants and adults have developed fully functioning and regulated lungs plus the physical capacity to react to and avoid depleted rebreathing.

Somewhat related to this is the strong suggestion that SIDS is the result of toxins found in crib mattresses. This theory was presented by UK scientist Barry Richardson which concluded that SIDS occurs as a result of toxic poisoning by gasses released by mattress, such as, phosphorus, arsenic and antimony. Fungi that grow in mattresses, from such things as food, urine, feces, vomit, etc., will react with the fire retardant chemicals in mattresses to create toxic nerve gasses which lead to SIDS deaths. These gases are heavier than air therefore congregate near the mattress surface. Because of these present gasses, babies in the face down position are more likely to suffer SIDS than those in the face up position. Therefore under this theory the progress made by the Back to Sleep campaign is the result of avoided toxic poisoning, not avoiding depleted rebreathing. Also they suggest that the increase in SIDS from the first, to second, to third and so on, is due to the reuse of mattresses, whereby the fungi are greater. They also suggest that the higher level of SIDS in poorer families is in all likelihood due to the use of used mattresses. To avoid this happening they suggest using special covers, such as organic covers, which will insulate the baby from these toxic chemicals, and therefore prevent SIDS.

This argument is somewhat persuasive, and I don’t doubt that an infant might die of some form of toxic shock due to some chemical. However, many of their arguments are not supported by known facts. Those that argue this theory state that SIDS has occurred as a result of the recent use of flame retardants in mattresses. Yet SIDS has been reported through history long before the use of the flame retardants. They state that babies of single parents are more at risk because these parents are more likely to use previously used mattresses. Really? Their studies show that babies of single parents are at about 8 times more risk as opposed to those of married couples’ first baby. Do these single parents use previously used mattresses by a ratio of eight to one? I doubt it. Have they proven that fungi and these chemicals actually do produce sufficient toxic chemicals at the mattress surface to cause death? They state that the reason that more boys than girls die of SIDS is due to the fact that boys create more heat which in turn produces more gases. Do they? They state that the reason that fewer babies that use pacifiers die of SIDS is due to the fact that those that use pacifiers sleep on their backs away from the mattress surface, which just hasn’t been proven. Many sleep on their tummies or side. They don't address the fact that not all SIDS deaths occur while in cribs.

In any case, notwithstanding the persuasiveness of some of their arguments, this theory has not received widespread acceptance. It may be possible that infants may die due to this toxic mattress theory, but these should not be considered as SIDS deaths. I believe that the medical profession might be advised to forensically classify each SIDS death when possible by category. It might be possible that some deaths are classified as SIDS, when in reality they are due to toxic shock. SIDS is now being decided by exclusion of other known causes. Perhaps the list of known causes needs to be modified or expanded, and toxic shock should be added to that list.

Motionless Air

As I have mentioned healthy air circulation is an important strategy for parents to understand and promote.

The stillness of air around a baby (sleep microenvironment) can increase the risk of SIDS. Consider that in the process of breathing, some of the air we breathe out is immediately redrawn, because it is still adjacent to our mouth. If there is some measure of air flow in the room, the air we breathe out will be pushed away before we draw in the next breath, thereby increasing the content of new air in the lungs. But if the air is still, the percentage of new air will be reduced and perhaps too insufficient for an early infant. Therefore anything around a child that can reduce air flow can possibly increase the risk of SIDS. Significant of these to consider are the bumper guards in a crib. These guards not only protect the child from bumping into the sides of the crib, but they also prevent fresh air from circulating to the child, especially when the child is wedged next to the bumper wall. Excessive or loose bedding as well as large fluffy toys can also impede air flow adjacent to a child.

It is my contention that SIDS may at times occur in cribs because of the bumper guards that are used in almost every modern crib. These bumper guards are used as padding around the walls of the crib to prevent the infant from hitting the side of the crib. These guards often are made of foam rubber or vinyl and when sealed tightly against the crib mattress (often covered with some form of plastic or vinyl to prevent damage due to wetting), cause the mattress and guard combination to function as a container. When a child is placed in a crib with these bumper guards, the child is actually being placed in a container... a low container, but none the less, a container.

Carbon dioxide, CO2, is heavier than air. When there are no means present for the mixing of crib contained air with room air, the CO2 expelled by a child will well or gather in the bottom of the crib, having no means of escape. This air I will call Trapped Spent Air, or TSA. This TSA will have varying degrees of higher concentrations of CO2 and lower concentrations of oxygen. The highest concentration of CO2 and the lowest concentrations of oxygen will be found at the lowest point in the crib container, next to the mattress. Air quality will improve as you go higher in the crib container.

There has been evidence that children who suffer from SIDS experience hypoxia, the deprivation of oxygen getting to the cells. There has also been evidence that the heart rate of SIDS and near-SIDS children is high at the time of the experience (could a high heart rate be another pre-SIDS indicator and can the high heart rate lead to overheating?). This would be consistent with the body working harder as it tries to circulate oxygen to the rest of the body. There has also been evidence that high carbon dioxide levels have been found in SIDS babies who slept on their tummies (again, hypoxia and evidence of CO2 is solid evidence of relationship to depleted rebreathing). The breathing of TSA in a crib or other similar container-like construction would be equivalent to breathing trapped CO2 in the bedding or soft toy when their mouth or nose was forced into it. Children who have been placed on their tummies will be forced to breathe the poorest quality TSA if there are bumper guards or similar items which block air circulation. Any child who is placed on their side will have their mouths, in some circumstances, higher than that of those on their tummies, and will breathe improved TSA. A child who is placed on their back will have their mouths the highest and breathe the highest quality TSA. My point here is that this TSA, trapped spent air, which is higher in CO2 and lower in O2, increases the possibility of depleted rebreathing, and thus increases the risk of SIDS and other outcomes.

Also, a child who is sleeping on their back will be expelling their air upward into the room air, which will help to prevent the accumulation of TSA. This may be another reason that children placed on their backs are the least prone to suffer from SIDS.

Please consider also that bumper guards are also used in playpens, and since playpens are often used as a place for a baby to take a nap during the day, these playpens can be just as dangerous for limiting air circulation and the trapping of CO2.

Trapped spent air does not need bumper guards in order to occur. Any physical condition that results in some form of container-like structure (even just a depression in a surface) can be adequate for trapped spent air to occur. A low point in a parental bed, a dip in a soft cushion, the folds of loose bedding or clothing, or any depression will be adequate to enable TSA to occur. Any condition that causes a container-like environment may result in a TSA danger. Parents will always be concerned over a child rolling off a couch or bed. They would not put the child at a high point as this would increase the risk of the child rolling off and hurting themselves. To avoid this they will position the child at the lowest point, or position articles (including themselves) around the child to form a barrier. This barrier, as well as any depression in the bed, couch, cushion, pillows, comforter, or sheepskins, will function much like a crib with a tightly sealed bumper guard. In some cases when a child sleeps with the parent, the parents’ breathing may add to the CO2well of spent air, while in other circumstances, their breathing may help to circulate air and protect the child. Unfortunately, a parent will have no way of knowing. Parents should always be cognisant of their child needing a fresh circulation of air at all times. An interesting finding is that children who sleep in the same room as their parents, but not in the same bed, are at a reduced risk of SIDS. This may be due in part to the added attention, but also that the parents movements and breathing may cause the air in the room to circulate, enabling a safer breathing environment for their early infant.

The reason that there have not been more deaths due to trapped spent air is that it can easily be mixed or diluted with room air by many means. A well ventilated room with an open window can lead to the dilution of trapped spent air. The proximity of the crib to air vents in homes with forced air heating and cooling can have an impact. A ceiling fan left on low speed as well as forced air furnace fans which can be permanently left on low speed is all that would be needed to ensure that still air is avoided. Are these important? Studies by DK Li, R Odouli , and K Coleman-Phox (Use of a Fan during Sleep and the Risk of Sudden Infant Death Syndrome. Arch Pediatr Adolesc Med. 2008) state that sleeping in a room with a fan reduces the incidence of SIDS by 72%, while sleeping in a room with on open window decreases SIDS by 36%. These statistics suggest that a fan is actually more effective than that of having an early infant sleep on their back. This suggests that the problem of still air adjacent to an infant is not only valid but is more significant than has been considered. It certainly demonstrates the relationship of depleted rebreathing to that of SIDS. Statistically SIDS occurs more often in northern latitudes, as well as more often in winter months. This could be partially due to lack of ventilation due to closed windows, partially due to the use of extra bedding to keep infants warm, as well as partially due to increased exposure to viruses.

Perhaps even a parent coming into a room briskly can cause circulation, or a child or pet running into or out of the room can be enough. A parent standing over the crib and breathing into the crib can be enough to dislodge the trapped spent air. Even the child itself sneezing, moving or sighing may be enough to clear any trapped spent air. Swaddling or tucking a child in tightly would prevent movement that could help circulate air which could lead to a SIDS outcome. What seems clear is that a very still environment is needed for trapped spent air to occur, and this stillness can and should be avoided by using some of the aforementioned strategies.


One of the more significant risks of SIDS is smoking by the mother during pregnancy, and second hand smoke by anyone in the home after the child is born. Passive second hand smoke increases the risk of SIDS by a factor of two. This is significant. It points to the lungs and breathing as the basis of SIDS, and the importance of a constant supply of fresh air to the child. I remember as a child that when my parents or any guests smoked (which was often back then), the smoke formed a low lying cloud which we had to look through to watch TV. I used to love waving my hand through it to make waves. It is not hard to agree that any of the poisonous gasses in smoke will settle in low lying areas of the room, in particular any crib container formed by bumper pads. A child would not only have to survive the accumulation of their own CO2, but also the toxic poisons that would accumulate in this sleep microenvironment. It stands to reason that any depleted rebreathing would be worsened significantly in this situation.

Thumb Sucking and Pacifier use

Does the use of a pacifier or thumb sucking reduce or increase the incidence of SIDS? Studies have shown that for pacifier use, the chance of suffering a SIDS death is reduced possibly by as much as 80% (Joanna Briggs Institute, Early childhood pacifier use in relation to breastfeeding, SIDS, infection and dental malocclusion, Best Practice 2005). Some studies even show a reduction in excess of 90%. This would appear to be more significant than the improvements due to the Back to Sleep program, yet many practitioners are reluctant to encourage pacifier use, as they are concerned about its impact on breastfeeding, possible infections, or their impact on teeth growth such as malocclusion. However, some now do promote the use of a pacifier for the first year in order to avoid an infant suffering SIDS.

Does the use of a pacifier equate to the practice of thumb or finger sucking? Data on thumb sucking appears to be limited at this time, as most of the focus is on pacifier use. It was always thought that the two had similar positive results in the reduction of SIDS. More and more parents have been introducing the use of a pacifier due to its success in reducing SIDS and because it would be easier to end an infant’s use of a pacifier in their second year simply by taking it away. Many parents who allow thumb sucking also allow their child to use a pacifier. At this point I still believe that thumb sucking is as effective as pacifier use. One advantage of thumb sucking is that it never falls on the floor and is always available to the child.

How could the use of a pacifier or thumb sucking have any bearing on the reduction of SIDS? One consideration is the reduced possibility that any bedding or other article could press against their mouth and nose, which in turn impedes breathing, because their fist or pacifier handle would be in the way. This prevents the possibility of depleted rebreathing in many cases. I agree; however, I also believe there is a second important reason. I believe that both thumb sucking and pacifier use both encourage breathing through the nose which will result in more efficient breathing, and in so doing reduce the possibility of depleted rebreathing. As mentioned, the nasal passageways are narrower than an open mouth. This will cause exhaled air to be blown with an increased velocity causing the spent air to be blown further away from the face. Also this velocity of air will act like a venturi, drawing fresh air from around the sides of the nose. This assures that the following drawing of air will be fresh air and not partially spent air.

Some would suggest that the success of pacifier use in reducing the risk is because it prevents the child from entering a deep sleep. This argument suggests that a child in a shallow sleep could easily avoid SIDS because they could be easily aroused. Yet I haven’t seen any studies that prove that pacifiers prevent deep sleep or that SIDS only occurs when an infant is in a deep sleep. They suggest that deep sleep can result in the stoppage of breathing; however, the stoppage of breathing, called apnea, is not considered as a cause of SIDS. Therefore their theory avoids apnea, not SIDS. I have suggested that SIDS might occur through deep sleep through the practice of shallow breathing, possibly increasing depleted rebreathing. Any reduction in SIDS cases attributed to deep sleep could be achieved through pacifier use in that this practice promoted nasal breathing, which reduced the risk of depleted rebreathing, not to mention that generally this practice prevents their being anything near their face that could impede breathing.

The idea that the use of a pacifier is detrimental to a child has not found wide support, although there seems to be a persistent body of parents who are adamant about not allowing this practice to be followed. They consider the use of a pacifier or thumb sucking only as a security issue which is less of a concern than the problems that its practice would cause. Part of the thinking is that the best way to get them out of the habit is to not start the habit in the first place. Others think it will affect their teeth, which is still not totally supported by the medical profession. Some studies have shown that pacifier use does have an impact on mouth and teeth formation but only when the practice continues after the age of two. Therefore it is suggested, and I would agree, that the habit be stopped after the age of two, since SIDS only occurs well before the age of two.

Also there has been some evidence that for some who continue to use a pacifier after the age of six months have an increase in middle ear infections, an increase in yeast infections in the mouth, and an increase in intestinal infections. In the interests of avoiding SIDS parents should weigh that risk against those milder irritants, perhaps having their infant tough it out until the baby is one year of age. Parents should make an effort to ensure that the pacifier is always clean, perhaps limiting their use while they are active, and in the case where there is an infection, ensure that the infant has an uninterrupted access to a fresh circulation of air.

Babies who sleep on their backs, those that use a pacifier and those who suck their thumbs are known to swallow more. Because these all reduce SIDS, is there a relationship between SIDS and swallowing? It may very well be that sucking exercises the throat, lungs and diaphragm in ways not yet understood, working to develop healthy strong lungs. Is there an argument that this increase in swallowing is the reason for the reduced incidence of SIDS with these practices? Perhaps to some extent. I don’t know, but I believe this line of reasoning is still worth investigating further.

Incidentally the same study by DK Li, R Odouli , and K Coleman-Phox , which stated that sleeping in a room with a fan significantly reduces the incidence of SIDS, also found that the use of a fan had little or no impact on those infants who practice pacifier use. This is probably due to the fact that pacifier use on its own is successful enough at reducing SIDS such that other measures are insignificant or difficult to measure. I would suggest practicing both.


As I have demonstrated, I believe that depleted rebreathing results in SIDS deaths. SIDS is caused by a host of variables, some external (such as, bedding or binding) and some internal (i.e., a babies’ developing ability to breathe independently), none of which can be solely identified as “the” cause. We will never identify one cause of rebreathing, because I believe that depleted rebreathing is not a single “sudden” incident caused by one influence. SIDS is the end of a process involving a number of variables under threatening situations over a period of time that may in some instances cause death, while in other cases, not cause death but can result in other disabilities. Depleted rebreathing seems to be the only variable that can be explained in every case. Without it, I don’t believe SIDS deaths occur.

Barry Stanley