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Breathing is a 24 Hour Activity by Randy Clare

You are probably paying close attention to how your patients breathe during sleep, but have you been curious about how they breathe during the day?

I have spent most of the last 25 years thinking about the diagnosis and treatments for sleep disordered breathing and related conditions. Recently I gave a talk where I made the statement that breathing is something we do 24 hours a day. This statement should not have been a shock, but like me, my audience hadn’t really put nighttime breathing and daytime breathing into the same category. It is widely reported that, a person at rest takes about 16 breaths per minute. This means we breathe about 960 breaths an hour, 23,040 breaths a day, 8,409,600 a year. The person who lives to 80 will take about 672,768,000 breaths in a lifetime. Since a person sleeps for a third of their life this 80 year old person will have taken 222,013,440 breaths while asleep (one third of their breaths). Sleep apnea, asthma or Chronic Obstructive Pulmonary Disease (COPD) all impact breathing quality, life expectancy and quality of life.

When we consider the sleeping patient we know that a cessation of breathing of 10 seconds or longer is an apnea which means there is no airflow. When we measure chest and abdominal effort we can separate an obstructed breath from times when the brain isn’t stimulating any breathing activity. A hypopnea is a shallow breath with a corresponding oxygen desaturation. The Apnea Hypopnea index or AHI is the sum of these events divided by the number of hours
of sleep.

But what if the patient has a compromised breathing pattern during the day? If the patient presents with wheezing, chronic cough, shortness of breath or blueness of the lips or fingernail beds the patient may have COPD, comorbid with their Sleep Apnea. This is a condition known as overlap syndrome.

For a patient to respond well to any sleep apnea therapy it is critical that the patient have sufficient lung function to breathe properly on their own. COPD affects approximately 20 million people in the United States and is the nation’s third leading cause of death.

Xavier Soler, MD, PhD, Assistant Professor of Medicine, Pulmonary and Critical Care Division, University of California San Diego, reports in his national COPD foundation Blog that:

“Patients with severe COPD commonly exhibit abnormal sleep contributing to chronic fatigue, daytime sleepiness. Additionally, medications used to treat COPD, such as albuterol or prednisone, may affect sleep quality. A reduction of nocturnal oxygen levels commonly seen in patients with COPD can have profound effects and contribute to long-term sequelae, producing arrhythmias, myocardial stress, and, possibly, lower survival. OSA occurs in about 10 to 15% of patients with COPD, a condition referred to as the “overlap syndrome”. Although the prevalence of OSA is similar in patients with COPD as in the general population, individuals with both conditions without CPAP treatment have an increased risk of death and more hospitalizations from acute exacerbations.”

Lung function can be objectively measured using a lung function test called spirometry (CPT 94375). A Spirometer is a device that measures the largest volume of air that can be moved into or out of the lungs. Lung function testing has been around since the mid 1800’s when the water-seal spirometer was developed. This simple device measured the patient’s Vital Capacity (VC). In the 1930’s it was observed that patients with emphysema exhaled more slowly than healthy subjects. The shift was made then to a Forced Vital Capacity (FVC) measurement to calculate the patient’s ability to clear the air out of their lungs and measure the time it took to do so. It was soon learned that healthy patients exhale 80% of their FVC in 1 second, this calculation is called Forced Expiratory Volume in 1 second (FEV1) and is used to identify and assess airway obstruction.

A Spirometer is a flow measurement device that consists of a flow transducer and a small computer to
do analysis. The patient takes a deep breath in and blows through the tube. Flow is measured and the
data is compared to predicted sets

Pulmonary function data is generally presented a flow-volume curve. Normal values for spirometry tests have been compiled into tables called normograms which are based on age, height, sex and race. Most computer based spirometer devices have these tables and can calculate percent to predicted values.

In adults, an FEV1that is lower than 80% of predicted value is considered abnormal. The department of pulmonology at Hospital de Hautepierre in Strasbourg France conducted a study called “Association of Chronic Obstructive Pulmonary Disease and Sleep Apnea Syndrome”, where patients with known sleep apnea were tested with a spirometer and 11% were found to have an FEV1 <60%, putting them at high risk of being Overlap patients; they tended to be older and all were male. It is interesting to note that Body Mass Index (BMI) in Overlap patients was identical to the non-overlap patients. In other words, the FEV1 data might be a critical identifier that would be very useful in managing this patient population. Treating SDB alone may be less effective in achieving maximum health.

This is a normal flow volume loop that shows flow on one axis and volume on the other. As the patient exhales quickly, flow is rapid and achieves a peak as the patient blows out longer the amount of flow diminishes as the volume gets smaller. The shape of the flow volume loop is often used to diagnose COPD and related lung diseases

“When both COPD and OSA are present, there may be an additive (synergistic) effect on the clinical picture, but it has not been established at what level of severity this occurs. For example, it is not clear if patients with severe COPD and mild OSA should be treated in a similar fashion to those with the opposite pattern — mild COPD concurrent with severe OSA. Both COPD and OSA have been linked to vascular endothelial dysfunction, increased levels of inflammatory mediators, and more rapid development of atherosclerosis. Other factors that link the two diseases include a worsening of both entities with increasing age, the shared risk factor of smoking, and worsening conditions when gastrointestinal reflux disease (GERD) is present.

There are many possible reasons why COPD can either cause OSA or make it worse in patients already suffering from the disease, and vice versa. COPD often involves chronic hypoxemia, which worsens during the night. (In addition, hypercapnia increases during the night for overlap disease patients, linking to greater nighttime desaturation and higher AHI.)” – Bill Pruitt, MBA, RRT, CPFT, AE-C, FAARC, is a senior instructor and director of clinical education in the department of Cardiorespiratory Sciences, College of Allied Health Sciences, at the University of South Alabama in Mobile.

COPD patients tend to have very specific respiratory patterns which have adapted in some cases over many years. Dr. Soler and his team at the University of California San Diego recently hypothesized in their study “Age, gender, neck circumference, and Epworth sleepiness scale do not predict obstructive sleep apnea (OSA) in moderate to severe chronic obstructive pulmonary disease (COPD): The challenge to predict OSA in advanced COPD”, that COPD patients are in fact so specific that their indications of OSA may in fact be distinctly different from the general population.

In their observational study, 44 patients who were receiving treatment in UCSD’s Pulmonary Rehabilitation Program who had a diagnosis of advanced COPD, were measured against traditional risk factors that include Sleepiness, Male Gender, Older age and neck circumference and were not associated with OSA in this group. This compares with elevated BMI, the presence of cardiovascular disease and FEV1+/-18.2% pred which were found to be very predictive of OSA in this population.

Patients in dental offices are often screened with the Epworth Sleepiness Scale (ESS), neck circumference and BMI are also often calculated. These simple screening tools start so many sleep conversations in the dental office. I was particularly struck by the comment in this study that, “Although Epworth Sleepiness Scale grades the severity of sleepiness, this symptom alone may be very common in COPD and, thus, lacking in predictive value.”

When I discuss spirometry with dental teams I am often asked if I believe that dentists should be screening patients for COPD. My answer is an unqualified YES. I believe that the dentist who is treating patients with sleep disordered breathing is in fact managing the obstructed airway. The more information at the clinician’s disposal can only improve clinical decision making and positively impact patient outcomes.

Sleep apnea treatment requires a team approach. In many cases patients have been ill for a long time and have more than one condition that require management. COPD and OSA in combination affect over 20% of the general population. The risk of mortality for untreated COPD and OSA is elevated. A simple spirometry test may show a patient who needs a referral for evaluation of an underlying breathing disorder that may seriously affect patient outcomes. The Dental office manages jaw position, and upper airway issues while the pulmonary physician manages the patient’s COPD.

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