Dyspnea can be thought of as difficulty in breathing of which the individual
is aware. Thus it is a subjective sensation that is difficult to measure and
somewhat poorly understood.
Production of Dyspnea |
Primary Causes |
Dyspnea occurs when ventilatory demand cannot be met by
the body's ability to respond.
Dyspnea develops when there is a mismatch between central respiratory
motor activity and incoming afferent information from receptors in the
airways, lungs and chest wall structures. (Concept of "length-tension
inappropriateness" termed by Campbell
and Howell in 1963)
The perception of respiratory effort increases whenever the central motor
command to the respiratory muscles must be increased; i.e. increase mechanical
load or weakened muscles and the increased work of breathing. (See: Corollary
Discharge). |
CHF |
The sense of air hunger, as described in patients with congestive
heart failure, has been shown to be associated with increases in ventilatory
drive, particularly in the presence of hypoxemia or hypercapnia. |
Bronchial Asthma |
The sensation of chest tightness is associated with bronchoconstriction.
It develops early in the process with mild airway obstruction. With progressive
decline in the lung function, increased respiratory effort follows and
lastly, air hunger develops. |
Perception of Dyspnea
|
Temporary dyspnea in healthy persons |
Healthy persons may perceive dyspnea due to exercise, but it is short
lived and well tolerated.
|
Chronic dyspnea secondary to illness |
Dyspnea occurs in patients with chronic disease when ventilatory
demands exceed supply. It is multifactorial.
|
Mood, Stress and Fatigue |
Fatigue and mood changes such as anxiety, depression, somatization, and
hostility significantly increase with high intensity of dyspnea in asthma
(Gift 1991). In an epidemiologic study
of healthy individuals, increase in anxiety, anger, depression associated
with increase of respiratory symptoms including dyspnea (Dales
1989). Anxiety has been shown to significantly correlate with the intensity
of dyspnea, as in cancer patients (Bruera
2000). |
Personality |
Personality influences perception of dyspnea:
- in emphysema, nervousness and cyclic tendency are the determinants
for dyspnea, in addition to anxiety (Kawakami 1992).
- in asthma, the severity of disease is linked to psychological disturbances
and poor perception of breathlessness, and
- in hypochondriacs dyspnea is related to severity. (Chetta 1998).
|
