Tag: sleep

Not Everyone Breathes While they Sleep: The Dangers of Sleep Apnea

You might think that breathing in our sleep should come naturally – if breathing and sleeping are both physiologically necessary, then we must be able to do them simultaneously right? Unfortunately, almost a quarter of middle-aged American men and nearly 10% of women suffer from sleep apnea, a chronic condition characterized by repeatedly stopping breathing while sleeping. The clinical symptoms seem rather benign – snoring, sleepiness, fatigue during the day or other issues sleeping. However, by far the most dangerous aspect of this disease is that it puts patients at increased risk of high blood pressure, stroke, coronary heart disease, as well as occupational and/or automobile accidents. Over the last several decades, a variety of therapy options have been studied to treat this condition, ranging from drugs to masks to surgery.

One of the earliest documented therapy options is using protriptyline to treat obstructive sleep apnea. Protriptyline is an anti-depressant drug that was used for its ability to clear airway obstructions during sleep; however, it did not gain significant popularity due to its adverse effects including cardiac complications and limited demographics for whom it would be an appropriate treatment.

The next treatment discussed was altering sleep positions for patients suffering from sleep apnea. A seemingly simple idea, a study determined that laying on the back significantly increased the severity of sleep apnea. Interestingly, the difference in severity between back and side sleeping positions was most noticeable in healthy, non-obese patients. The authors believe that lying on the back causes tissues of the throat to obstruct the trachea and prevent smooth airflow during breathing, as shown in the image below, which would explain why obesity can exacerbate sleep apnea.

Diagram of airflow obstruction through mouth and throat
Photo by Habib M’Henni on Wikimedia Commons.

Multiple non-invasive devices were also studied, including oral appliances, sleep posture alarms, and positive airway pressure devices. Oral appliances can either protrude the lower jaw or restrain the tongue; both aim to restructure the upper airway (mouth, trachea, etc.). Sleep posture alarms were suggested to train patients to sleep on either side, rather than on their backs. Positive airway pressure devices (Bi-PAP, CPAP) are the most commonly used treatment for sleep apnea currently; they maintain a consistent air pressure flowing into the mouth to ensure the airways do not collapse during sleep.

Man sleeping while using CPAP machine
Photo by ApneaMed

The final treatment studied was nocturnal supplemental oxygen (NSO), which involves increasing the concentration of oxygen in the air inhaled while sleeping. However, a study comparing use of a CPAP with use of NSO found that CPAP treatment was far more effective at decreasing the patients’ blood pressure and still proved effective in patients already taking blood pressure medication.

Overall, the best method for treating sleep apnea is dependent on the patient and his or her underlying conditions. Changes in sleep posture could greatly enhance the sleep quality of a moderate case of sleep apnea; CPAP would be ideal for someone who can easily tolerate the mask and does not frequently move in his or her sleep. Each of these demographics makes it difficult to define one optimal solution for treating sleep apnea, but the variety of available treatment options provides hope for those patients who suffer from this chronic illness.

The Study of Snoring is Anything but Boring

Here we take a deeper look about that noise that plagues some of our family members, our roommates…or even ourselves!

Elderly man sitting in the sun, asleep with head back and mouth open.
Photo by Stephen Oliver on Unsplash

What Causes You to Snore in the First Place?

The human upper airway contains anatomical parts that are membranous, meaning they lack support from cartilage. Some parts include the tongue, the soft palate, and the tonsillar pillars. A lack of cartilaginous support enables these parts of the airway to be susceptible to vibrations.

Anatomical diagram of the human upper airway.
Modified from Huang, Quinn, Ellis, and Williams, “Biomechanics of Snoring,” from Endeavor, 1995.

During sleep the upper airway muscles relax and cause the size of the airway space to decrease, resulting in airflow limitation and turbulence.

Whenever we inhale, the turbulent flow through the relaxed airway causes those membranous structures to vibrate and produce a sound most commonly known as snoring.

A Brief Mechanical Explanation of Snoring

Examining snoring in the view of mechanical systems, respiratory noise is created by the oscillation of the upper airway with the air passing through it. This oscillation is indicative of an issue with flow instability (turbulent flow) over a flexible structure (the relaxed airway).

An experiment was created to model the movement of the soft palate during snoring, where a piece of wood was used to simulate the hard palate and a piece of leather simulated the soft palate. The leather and wood were attached to each other inside of a rigid tube that was connected to a pump (meant to model the lung inspiration).

During inspiration, the leather flap oscillated until it reached its full amplitude. Upon reaching the maximum amplitude, the leather flap hit the wall of the tube and created a noise known as palatal “flutter”. This palatal flutter is the most common method of noise production in humans: snoring.

Is Snoring Something to Be Concerned About?

Young woman waking up in the morning, appearing tired.
Photo by Kinga Cichewicz on Unsplash

Approximately 44% of men and 28% of women are habitual snorers.

Snoring can be a symptom of obstructive sleep apnea, a condition distinguished by snoring and breathing that is labored by repetitive and obstructive gasps.

The fragmented sleep resulting from sleep apnea can lead to decreased energy and poor attention and concentration. Sleep apnea can also be related to vascular issues like hypertension and its prevalence appears to increase in people over 65 years of age.

What Are Some Remedies to Snoring?

Remedies for snoring range from noninvasive devices to invasive surgical procedures.

The surgical option to remedy snoring involves removing a portion of the vibratory tissue from the back of the upper airway. For those people wanting to avoid surgery, non-invasive solutions include the use of nasal strips to lift and open the nasal passages; experimenting with sleep positions other than sleeping on the back; or using oral appliances and nasal continuous positive airway pressure (nCPAP) to prevent the tongue and soft palate from collapsing into the upper airway. Losing weight, avoiding smoking and alcohol can also help to reduce snoring.

There are also resources for snoring in kids, as well as additional home remedies and surgical information regarding snoring.

Below is a great animated video which gives an introductory explanation to snoring.

How do Flamingos Stand on One Leg?

How long can you stand up before you get tired?

This is an important question for animals that sleep standing up, like horses and flamingos.  Our joints are stabilized by muscles, but the constant activation of muscles needed to maintain balance requires energy and induces fatigue.

flamingo standing on one leg while grooming
Photo by Lieselot. Dalle on Unsplash

Flamingos are especially perplexing because they often sleep on only one leg. This requires that single leg to support the entire weight of the animal and maintain balance. Researchers think that this is beneficial because it allows them to switch legs when one gets tired. But does that benefit outweigh the cost of maintaining balance on a single leg?

Researchers Young-Hui Chang at Georgia Tech and Lena Ting at Emory investigated this question in a recent paper by examining the muscle forces required to support body weight and maintain balance in flamingos standing on one leg.

Using dead flamingos (that can’t generate active muscle forces), the researchers clamped one leg and tilted the cadavers forward and backward (video).   They found that the leg remained straight even after rotating it more than 45 degrees in each direction. This only happens when the bird’s foot is right underneath its body, not when it’s off center (like it is when standing on two legs).

This is remarkable, because flamingos’ femurs (the large bone in our thighs) are horizontal. Essentially, a standing flamingo is in a position similar to a human doing a squat! The researchers think that the bird’s bodyweight generates passive joint moments around the hip and knee, keeping the joints into a fixed position in order to support the weight of their body. A similar arrangement, called a stay apparatus, is found in horses for the same purpose, and bat fingers contain a similar lock that helps them stay hanging for long periods of time.

In a second experiment involving live baby flamingos, the researchers used a force plate to measure the center of pressure in their feet as they stood on one leg. (To feel this center of pressure, stand on one leg and feel different parts of your foot press into the ground as you try to keep your balance.)

baby flamingo standing on one leg, with diagrams showing force plate readings
modified from Chang & Ting, Biology Letters 2017

While they were awake and active, the center of pressure moved a lot, but when they rested or fell asleep, they were remarkably stable. This led the researchers to suggest that the birds may have a way to balance without active muscle forces as well, although they do need to work actively to keep their balance when being active, like while grooming.

Flamingos, with their big bodies and long, slender legs, resemble an inverted pendulum. Inverted pendulums are a classic example of an unstable system, which will fall over without active control. But flamingos manage to stay upright for long stretches of time – and if we can figure out how, we might be able to bring stability to other unstable systems! This could be helpful as we try to make robots who can walk on uneven surfaces – and they need all the help they can get with that: