Difficulty breathing (dyspnea) may also be described as shortness of breath, breathlessness, uncomfortable breathing or labored breathing. It is the sensation of not being able to get sufficient air despite trying hard to breathe in deeply or rapidly. It is not uncommon to experience this sensation during periods of strenuous activity or when anxious, nervous or during emotional shock. The shortness of breath in these instances are transient and will settle within a short period of time. It can however, be considered abnormal when there is shortness of breath with minimal activity, or even at rest, when lying down or sleeping.
What is orthopnea and paroxysmal nocturnal dyspnea?
Breathlessness when lying down flat is known as orthopnea and patients will report relief upon sitting or standing up. Paroxysmal nocturnal dyspnea (PND) is shortness of breath that occurs at night while asleep and awakens a person sometimes with gasping and choking. Like orthopnea, PND is often relived by sitting up.
Patients with orthopnea, and even those who frequently experience PND, tend to use extra pillows and prop themselves up at night in order to prevent the shortness of breath or attacks. Some patients may be unaware that their change in sleeping behavior, i.e. using more pillows, is a a result of breathing difficulty. Orthopnea can be graded by the number of extra pillows a person uses – more pillows signifies a more severe orthopnea.
Ann uncommon type of breathing difficulty when lying down is known as trepopnea. Here a patient reports shortness of breath when lying on one side (lateral decubitus position) but not when lying on the opposite side.
Pathophysiology of Orthopnea and Paroxysmal Nocturnal Dyspnea
Orthopnea and paroxysmal nocturnal dyspnea occurs primarily in cardiovascular disease but is also prominent with certain respiratory diseases like COPD (chronic obstructive pulmonary disease) and bronchiectasis. When lying flat, there is a larger degree of fluid reabsorption from parts of the body that are edematous (fluid swelling). The greater venous return leads to pulmonary congestion and pulmonary edema (fluid in the lungs). This reduces the surface area in the lung available for gas exchange. Shortness of breath or breathlessness then arises. Lying flat also requires a slightly greater effort when breathing and this is leads to breathlessness in patients with COPD, in pregnancy and those with significant abdominal obesity.
Causes of Difficulty Breathing when Lying Flat or Sleeping
In some conditions, the difficulty breathing becomes evident within seconds or minutes of lying flat, while in other cases it may only become apparent after hours. PND tends to arise within 1 to 2 hours after sleeping while orthopnea is prominent even when lying down for a short period of time hence the need for extra pillows.
- Chronic obstructive pulmonary disease (COPD) – emphysema, chronic bronchitis
- Diaphragmatic paralysis
- Heart failure
- Heart valve disease
- Ischemic heart disease (coronary heart disease / coronary artery disease)
- Chronic hypertension
- Sleep apnea
Other symptoms that may be present with orthopnea or PND