The healthy adult at rest involuntarily inhales and exhales some 20,000 times a day, as naturally as seawater slides back and forth in a tidal zone. This cycle is so routine and rhythmic that we hardly notice it—except when something goes wrong, such as when we can't seem to get enough air into our lungs.
A number of easily identified disorders can cause such shortness of breath (dyspnea, in technical terms), including asthma, lung infections and chronic obstructive pulmonary disease (or COPD, an umbrella term for various conditions that permanently impair airflow through the lungs). Congestive heart failure, in which the heart no longer pumps normally and so cannot deliver enough oxygen and nutrients to the body, is also well known to disrupt breathing. But absent any of those conditions, patients who are out of breath are also often out of luck in terms of getting an accurate diagnosis—or an effective treatment.
Indeed, it turns out that the seemingly basic act of breathing is more complex than scientists have traditionally understood it to be. New research efforts are under way to figure out how it works and why it goes awry. The science of why breathing falters is still young, but already fresh insights are spurring investigators to develop new tools for pinpointing the causes of mysterious cases and devising ways that clinicians can help patients breathe easier.
To get a sense of how complicated it can be to identify why someone is short of breath, consider a hypothetical scenario described by pediatric pulmonologist J. Tod Olin of National Jewish Health in Denver. A shy 16-year-old who is under a lot of stress says she “just can't get a good breath.” By the time the young woman reaches a pulmonary or respiratory specialist, she may already have visited four or five other doctors and come up empty.
The specialist puts her through standard tests for the most obvious causes, starting with asthma, which is marked by inflammation that can lead the lungs' airways to swell, constrict and fill with mucus temporarily. As a result, patients may become short of breath or wheeze, making a whistling sound in their chest. Exercise can trigger asthma symptoms, but this patient is sedentary and has not responded to asthma medications. Spirometry, a test that measures airflow during breathing, does not demonstrate a pattern consistent with asthma or COPD. Moreover, when the specialist listens to lung and heart sounds for signs of decreased function and observes the motions of the chest, throat and other relevant body parts, the inhalations and exhalations resemble frequent deep sighing breaths rather than the wheezes common in asthmatics.
The doctor orders a chest x-ray, electrocardiogram and CT scans to check for infection, a foreign object in the windpipe or food pipe, or signs of possible cancer or heart disease. But these tests all look normal, as does a check of the patient's vocal cords to see if they might be constricted and blocking her airway.
So the doctor examines the patient's breathing more closely. The patient dons a plastic mask that connects to a device that collects samples of exhaled air. The samples get channeled to sensors that instantaneously measure airflow, oxygen levels, carbon dioxide levels, and more. The data reveal an erratic pattern in the amount of air the patient inhales: she alternates between drawing in 20 liters one minute and eight liters the next. A blood test shows standard levels of dissolved oxygen and slightly low carbon dioxide levels, signaling that the patient is taking in sufficient quantities of oxygen but exhaling excessively.
By process of elimination, the doctor finally diagnoses the young woman with “dysfunctional breathing,” a mysterious disorder that researchers have only recently begun to recognize. Dysfunctional breathing, also known as dysfunctional breathlessness, may accompany and worsen symptoms of asthma, COPD and other conditions, but it can also stand alone. As Olin's scenario suggests, there is no medical consensus on gold-standard diagnostic criteria for dysfunctional breathing. Further complicating matters, patients may not seek medical attention, because they have adapted their behavior to avoid symptoms—giving up singing or a competitive sport, for instance—notes Mark L. Everard of the University of Western Australia. People with the disorder, which by some estimates may affect 10 percent of adults at some point in their life, are often thus undiagnosed or misdiagnosed or receive inappropriate care.
Exactly what causes dysfunctional breathlessness is uncertain, but many experts suspect that it originates from biomechanical or psychological disturbances, or some combination of the two. One possible culprit is breathing that stems from the upper chest rather than the entire chest and abdomen.
Treatment for dysfunctional breathing is not standardized yet. By the time patients are diagnosed with it, they have most likely already tried drugs known as beta-agonists that relax the airways to ease breathing, with disappointing results. Switching to other combinations of beta-agonists may help, however. Some people with the condition may receive coaching on how to breathe normally at rest and in motion, as well as psychological counseling if a doctor thinks that stress or emotions are involved. Over time patients usually take more control over their breathing, and the condition fades. Still, treatment may have resolved the symptoms but done nothing to address the root cause.
Clearing the Air
Experts agree that better care for breathless patients will require sharper understanding of the processes surrounding inhalation and exhalation and the mechanisms behind breathing disorders. Improved technology for measuring breathing patterns and clearer diagnostic criteria for dysfunctional breathing will also be key.
Of course, the body's controls on breathing are far from unknown. Scientists understand that signals sent from the brain stem instruct the throat, chest and abdominal muscles, especially the diaphragm, to expand and contract involuntarily, drawing in and expelling air. And it is clear that we also have some behavioral control over breathing—we can intentionally slow it down, speed it up, and take deeper breaths or shallower ones. Likewise, we can coordinate it with swallowing, speaking, singing and eating. But dig much deeper into the science of dysfunctional breathing, and the picture becomes murkier.
To be fair, pulmonary and respiratory researchers face particular challenges. Lungs perform at least three functions: they bring in oxygen and clear out carbon dioxide, they regulate the body's balance of acidic and basic compounds required for proper organ functioning, and they filter out the soup of foreign particles we constantly inhale. A lung is thus a more complicated organ in some ways than the kidney or the heart, says Richard Castriotta of the University of Texas Health Science Center at Houston.
Further, the process of breathing involves many systems in the body, from the central and peripheral nervous systems to the respiratory and digestive systems. “If you go to the doctor and say, ‘I have trouble breathing,’ there are so many different diseases, disorders, maladaptive positions and techniques that could be the cause of the problem,” says Gina Vess of Duke University. “You might go to a cardiologist, a pulmonologist, an [ear, nose and throat] surgeon, a laryngologist, a speech pathologist, a physical therapist, a respiratory therapist or a psychiatrist.”
Even so, the developing field of breathing research (which is distinct from the larger field of pulmonology) is delivering new insights into various breathing disorders. For example, Olin has figured out how to obtain real-time images of the voice boxes, or larynxes, of athletes suffering from exercise-induced breathlessness, which is distinct from dysfunctional breathing. He outfits patients with a helmet-mounted digital endoscope that shows the larynx while they cycle on stationary bikes. He and his team have found that the larynx becomes more severely constricted in these athletes when they exercise at maximum intensity than when they exercise less arduously or are at rest. The observations hint that the athletes may differ from the general population in the structure of the upper part of their airway or in their behavioral response to intense exercise. Surveys of the existing medical literature on dysfunctional breathing have also proved enlightening. Stephen J. Fowler of the University of Manchester in England and his colleagues recently reviewed dozens of reports on the condition to take stock of the ways in which it manifests and is assessed and treated. Their analysis revealed five common types of dysfunctional breathing and the breathing patterns associated with each of them—findings that could eventually help doctors tailor treatments more closely to patients' needs.
Clinical applications of those discoveries may be a way off, however. In the near term, the best hope for those suffering from breathing problems lies in better agreement on standards for diagnosis and treatment. To that end, Fowler and others who treat and study dysfunctional breathing have met in England every week for the past six months to discuss difficult cases.
Pulmonary specialists agree on where we should aim to end up: breathing naturally. Vess notes that people can often help themselves reach that goal by avoiding clothing that restricts movement of the chest and abdomen and relaxing the gut to likewise liberate the breathing muscles. Excess fat in the abdominal area can impede inhalation and exhalation in extreme cases, Castriotta says, so maintaining a healthy weight is important, too.
As for when to worry about shortness of breath, Castriotta offers the following recommendation: people who struggle to keep up with others their own age during activities such as walking or climbing stairs should seek medical attention.
Some people who have no shortness of breath may wonder whether they should take measures anyway to tone their breathing apparatus. The answer, says Michael Koehle of the University of British Columbia, is no. Deep-breathing exercises such as yoga breathing may help reduce stress and anxiety. But even during exercise our innate respiratory-control system usually does quite well at providing adequate oxygen supply and removing carbon dioxide produced by metabolism. “In the strictest definition of health—absence of disease—it is not necessary to do specific breathing practices,” Koehle notes. In other words, you may now exhale.