There are several different types of respiratory disorders that can primarily be described as either restrictive or obstructive. Obstructive disorders are more common than restrictive and share the characteristics of blocked airways. With a restrictive disorder, such as cystic fibrosis, the person would show an inability to expand the lungs to the needed volume to properly ventilate. Restrictive disorders can also be a consequence of pulmonary scarring because of diseases such as idiopathic pulmonary fibrosis, which will result in failure of lung expansion. Restrictive disorders typically have a lower survival rate. Diseases that would be considered obstructive include chronic obstructive pulmonary disease (COPD), asthma, and bronchitis. There are some similarities noted with obstructive and restrictive disorders such as symptoms, signs, diagnosis, and treatment methods (1).

There are a wide variety of restrictive lung diseases that range in severity and have fluctuating treatments. Conditions that lead to lung restriction include, but are not limited to, neuromuscular disease, obesity hypoventilation syndrome, kyphoscoliosis, interstitial lung disease, and pregnancy. People with restrictive lung diseases such as interstitial lung disease are noted to have increased sleep difficulties, which often present as obstructive sleep apnea (OSA) (1). Treatment for OSA as well as restrictive lung diseases does frequently correlate because of the mechanisms that affect both diagnoses and the benefits of noninvasive ventilation or continuous positive airway pressure in these patients. Given the prevalence of OSA as well as restrictive lung diseases, it is not uncommon to see them in association with each other. The unfortunate consequences of both diagnoses increase the severity of these diseases and, in turn, could lead to higher morbidity and mortality rates. With treatment, it is possible to reduce the long-term consequences of OSA and restrictive lung disease.

OSA is the most common form of sleep apnea and is an obstructive respiratory disorder (2). There are several sleep disorders that have been identified using polysomnography (PSG). OSA has shown negative consequences on a person’s health because it affects his or her ability to properly perform gas exchange—carbon dioxide (CO₂) and oxygen, while asleep. Although someone may have no trouble breathing during the day, the shift that the body makes from wake to sleep reduces the muscle tension throughout the body. During an apneic event, there is a reduction in the airway when the pharynx collapses, resulting in reduced airflow (hypopnea) or a completely obstructed airway (apnea). The frequency and the severity of these events are typically dependent on anatomic and neural factors. When there is a reduction or cessation of airflow, the oxygen provided to the body is reduced, which will notify the body’s neurochemical
receptors that the body has gone into a hypoxic state and this leads to hypercapnia because of inefficient exchange of gases. Generally, when these events show a cyclic pattern, it increases the severity. The negative effects of sleep apnea are notable for the importance of diagnosis and treatment. A person presenting with sleep apnea commonly shows adverse effects on all body systems that could result in the following: hypertension, coronary artery disease, stroke, cardiac arrhythmias, and pulmonary hypertension. Patients with OSA often report daytime sleepiness, concentration problems, memory loss, and less commonly studied but noteworthy anxiety and depression. There are many contributors to OSA such as obesity, altitude, gender, age, anatomic features, genetics, smoking status, and other lung diseases (2).

Diagnosis of lung disorders is similar in restrictive and obstructive disorders. A person presenting with symptoms of cough, wheezing, and shortness of breath would have spirometry testing. Spirometry is relatively quick and inexpensive. Spirometers measure how much air someone can breathe out and how quickly. How well the lungs deliver oxygen to the blood can also be measured by simply breathing into a spirometer. Other means of diagnosing and marking the severity of lung disorders are by checking arterial blood gases or by performing a chest x-ray or computed tomography of the chest to evaluate signs of damage and determine from where these are originating. In cases of severe restrictive disorders such as cystic fibrosis, genetic testing may reveal a gene mutation resulting in the disorder.

Sleep-related hypoventilation is described as insufficient sleep-related ventilation that results in hypercapnia or increased partial pressure of carbon dioxide (PaCO₂). This is the result of slow and shallow breaths that are inadequate for proper gas exchange. Sleep-related hypoventilation is not always in association with other lung or airway diseases and does not require associated disorders for diagnosis. Sleep-related hypoventilation is diagnosed by monitoring PaCO₂ during a PSG using transcutaneous or end-tidal CO₂ monitoring. OSA is often present in these situations, and treatment of OSA can reduce the severity of sleep-related hypoventilation. Because of the presence of hypercapnia and hypoxia, these patients commonly develop pulmonary hypertension, heart failure, cardiac arrhythmias, and neurocognitive dysfunction. Sleep-related hypoventilation is worsened by the use of sedatives, alcohol, and depressants (3).

COPD can increase the severity of OSA in patients because of the decrease in cardiopulmonary function during sleep. Both diseases result in insufficient exchange of oxygen and CO₂. Patients with COPD have increased severity of oxygen desaturations and they typically occur more frequently, thus resulting in increased work on the heart (4). Unlike patients with OSA alone, those who are diagnosed with OSA and COPD show effects on the respiratory system during the day as well. Approximately 1% of adults have been diagnosed with overlapping OSA and COPD (5).