In my last two shareposts on obstructive sleep apnea I referenced treatments involving CPAP machine. These machines are very familiar to those with sleep apnea or those who know a person who uses one. In my practice, it seems like everyone knows what CPAP is and how it works. But I’m pretty sure as a pulmonologist, that this assumption is quite wrong.
So What Is It?CPAP stands for Continuous Positive Airway Pressure. When we normally breathe air in, the lungs and diaphragm work to create breath by generating negative air pressure. Usually the pressure is enough to draw the breath into the lungs and then release. But for those with apnea, the breath causes the person’s airway to close, and since the muscles aren’t strong enough to create pressure to push it back open it stops airflow. This is especially the case in those that have central obesity (a big belly) pushing up against the diaphragm. For anyone, apnea can occur many times during the sleep cycle when muscles are most relaxed, restricting the flow of oxygen to a person. Their spouse may notice that during sleep, the person literally stops breathing and then suddenly gasps for breath.
How Does a CPAP work?The main purpose of the CPCP is to regulate the pressure throughout the airways to create breath. Just how much pressure is necessary keep the airway open? It actually varies with each individual. Doctors will often conduct sleep studies are to evaluate the individual. The art of the sleep study is devoted in part, to evaluating the titration phase. The machine is applied to the patient with a baseline pressure of 4 cc (of water). The pressure is raised every 15 minutes, until all of the apnea events are completely eliminated.
Although they have been a relief to patients, doctors have previously faced challenges with CPAP machines. Due to the constant rush of air into the body, it can be very challenging to exhale when a machine is providing that air flow. For this reason, newer CPAP machines have a feature called the expiratory release valve or** Cflex** (there are proprietary names by different manufacturers), which allows the machine to lower the pressure during exhalation. Other machines, known as BIPAP, offer two pressure settings during operation, and are commonly used in hospitals.
Another challenge doctors face is addressing the type of apnea that needs to be treated. There is apnea caused by obstruction of the airway interfering with the effort of breathing, as well as the apnea due to a lack of effort, called central apnea. Some specialized ans sensitive machines, called Adaptive Servo Ventilators have a feature that helps distinguish between the two causes. When the machine senses that the apnea is due to the fact that the brain forgot to send the signal to breathe, it sends a full breath rather than just the pressure (in the case of obstruction).
Find the Best CPAP Therapy for YouThere is clearly so much mechanics, technology, and physics to know when handling a patient who is diagnosed with sleep apnea. It is actually beyond the knowledge and skills of most clinicians.** That is why it is crucial for both types of apnea, to be diagnosed and treated by highly specialized physicians, pulmonologists and board certified sleep disorder specialists.** I can tell you from my experience that this is often not the case. Most physicians believe that they know what to order (in terms of CPAP) simply by reading the results of the sleep test. My personal perspective is that a great disservice to many patients suffering with this serious condition is done when they are not referred to specialists.
It’s also important to note that most machines have a reading card that records the patient’s usage, the apnea events, and air leaks that can occur. The doctor who orders the CPAP machine should have the training necessary to do readings and interpretations of the card, 30 to 90 days after the machine has been prescribed, and to make adjustments to the settings if necessary. Obviously if apnea events are still occurring, adjustments are crucial.
Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music. Find him on Twitter @Lung_doctor.