Obstructive vs. Restrictive Lung Disease
Respiratory diseases are one of the most common reasons for consultation and one of the first steps to take is to discover if it is an obstructive or restrictive lung disease. Obstructive lung diseases are the most common and include disorders of the airways. Restrictive lung diseases are less common and include those that limit the capacity of the airways to expand.
Obstructive lung diseases include:
- Chronic obstructive pulmonary disease (COPD)
- Bronchiectasis
- Bronchiolitis
- Asthma
- Cystic fibrosis
Restrictive lung diseases include:
- Idiopathic pulmonary fibrosis
- Asbestosis
- Amyotrophic lateral sclerosis (ALS)
- Guillain-Barre syndrome
- Ankylosing spondylitis
While both obstructive and restrictive lung diseases may present similarly, a thorough patient history, physical examination, and specific diagnostic tests will differentiate the two, leading to the correct diagnosis.
Obstructive Lung Disease
Obstructive lung diseases are those caused by an obstruction of the airway. This can occur when inflammation and swelling cause narrowing and blockage of the airway, making it difficult to release air from the lungs and leading to slower and shallower exhalation. Because of this, a large volume of air remains trapped in the lungs, which can worsen symptoms. Here are some examples of obstructive lung diseases:
- Chronic obstructive pulmonary disease (COPD)
- Chronic bronchitis
- Asthma
- Bronchiectasis
- Bronchiolitis
- Cystic fibrosis
These conditions are life-long, so it is important to recognize them early to aid management. The primary risk factor for obstructive lung disease is smoking. It irritates the lining of the lungs and leads to decreased functioning. Other environmental irritants, like dust, fumes, chemicals, and secondhand smoke, also negatively contribute to the health of our lungs.
Restrictive Lung Disease
Unlike constrictive lung diseases, restrictive lung diseases are marked by inhalation that insufficiently fills the lungs. As a result, there is a reduced total lung capacity. Restrictive lung diseases may be intrinsic, extrinsic, or neurologic in origin. Here are examples of each:
Getting a Good History and Physical Examination
Clearly, there are numerous causes of lung disease. Therefore, as physicians, it is important to be thorough but discerning in order to arrive at the correct diagnosis and provide the most appropriate treatment.
Starting with an accurate history and performing a thorough physical examination is essential. These initial pieces of information will:
- Dictate diagnostic tools
- Aid in diagnosis
- Help decide direct treatment
Symptoms
While obstructive and restrictive lung diseases differ in etiology, diagnosis, and treatment, they do have overlapping symptoms:
- Shortness of breath
- Persistent cough
- Tachypnea
- Anxiety
- Unintentional weight loss
Table A below lists symptoms that are unique to obstructive and restrictive lung diseases.
Ultimately, having a keen eye for detail will not only help you note all the patient’s symptoms but also aid in your differential diagnosis, which could be:
- Non-specific interstitial pneumonia
- Pneumoconiosis
- Systemic sclerosis
- Hypersensitivity pneumonitis
- Sarcoidosis
Diagnosis
Obstructive and restrictive lung diseases may present similarly. To differentiate the two, it is necessary to obtain an accurate history and conduct a thorough physical examination. Respiratory diseases often present with dyspnea and cough.
Patients with obstructive lung disease may complain of tightness in the chest or have difficulty catching their breath. Take note of the onset and duration of the patient’s symptoms, as these are helpful diagnostic clues. Obstructive conditions that cause sudden shortness of breath include:
- Myocardial infarction
- Bronchospasm
- Pulmonary embolism
In contrast, obstructions diseases whose symptoms progress gradually include:
- Chronic obstructive pulmonary disease (COPD)
- Idiopathic pulmonary fibrosis (IPF)
Another necessary distinction to make is for asthma, wherein patients mostly breathe normally butand experience sudden short crises with dyspnea triggered by a specific cause. Beyond from these, it is also important to ask the patient about aggravating or alleviating factors.
The timing of the symptoms also gives us an idea of the condition’s location. For example, when accompanied by phlegm, an acute cough often marks an infection of the upper respiratory tract. In contrast, a chronic cough (lasting for more than eight weeks) usually involves obstructive lung diseases of the lower airway or even conditions unrelated to the respiratory system.
A thorough physical examination should complement an accurate history.
When examining a patient with respiratory disease, their vital signs are simple but meaningful clues to the patient’s condition. Their heart rate, respiratory rate, and oxygen saturation all tell us about the patient’s oxygenation status. Additionally, arterial blood gas testing is also helpful as it detects problems with perfusion and oxygenation.
Spirometry is the initial pulmonary function test usually requested and involves asking the patient to blow forcefully through a small tube and measure the indicator’s distance traveled. This test tells us about the patient’s lung volumes. Inspection, percussion, palpation, and auscultation are done systematically. Upon auscultation, the clinician should listen for wheezes, rhonchi, stridor, and crackles, which can give give important clues to the location and extent of the patient’s disease.
Finally, imaging of the chest, using X-ray or CT scan, is useful in assessing the etiology and extent of the disease. These tools help in narrowing down your list of differentials.
Treatment
For obstructive lung diseases, the smooth muscles lining the airways may constrict, thus triggering a bronchospasm. In these conditions, medications like bronchodilators are directed toward opening up the airways. Further treatment options include:
- Formoterol
- Ipratropium
- Tiotropium
- Albuterol
- Salmeterol
- Theophylline
Restrictive lung diseases tend to worsen over time, so treatment is geared towards controlling the symptoms. Options include:
- Cyclophosphamide
- Corticosteroids
- Methotrexate
- Azathioprine
- Oxygen therapy
- Cellular therapy
It is important to counsel patients to not just purchase any over-the-counter anti-cough medication as they cannot accurately diagnose their particular respiratory issue and risk making it worse through the medication’s side-effects or not treating the symptom. They should consult with you the physician immediately for proper assessment and management.
Disclaimer: This article should not be taken as a replacement for medical advice. Comply with current practice guidelines in your area.
