Chapter

Dyspnea, Orthopnea, and Paroxysmal Nocturnal Dyspnea

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In book: Clinical Methods: The History, Physical, and Laboratory Examinations, Edition: 3rd, Chapter: Chapter 11, Publisher: Butterworths, Editors: H Kenneth Walker, W Dallas Hall, J Willis Hurst
Source: PubMed
ABSTRACT
Dyspnea refers to the sensation of difficult or uncomfortable breathing. It is a subjective experience perceived and reported by an affected patient. Dyspnea on exertion (DOE) may occur normally, but is considered indicative of disease when it occurs at a level of activity that is usually well tolerated. Dyspnea should be differentiated from tachypnea, hyperventilation, and hyperpnea, which refer to respiratory variations regardless of the patients" subjective sensations. Tachypnea is an increase in the respiratory rate above normal; hyperventilation is increased minute ventilation relative to metabolic need, and hyperpnea is a disproportionate rise in minute ventilation relative to an increase in metabolic level. These conditions may not always be associated with dyspnea. Orthopnea is the sensation of breathlessness in the recumbent position, relieved by sitting or standing. Paroxysmal nocturnal dyspnea (PND) is a sensation of shortness of breath that awakens the patient, often after 1 or 2 hours of sleep, and is usually relieved in the upright position. Two uncommon types of breathlessness are trepopnea and platypnea. Trepopnea is dyspnea that occurs in one lateral decubitus position as opposed to the other. Platypnea refers to breathlessness that occurs in the upright position and is relieved with recumbency.

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11
Dyspnea, Orthopnea, and
Paroxysmal Nocturnal Dyspnea
VASKAR MUKERJI
Definition
Dyspnea
refers to the sensation of difficult or uncomfortable
breathing
. It is a subjective experience perceived and re-
ported by an affected patient
. Dyspnea on exertion (DOE)
may occur normally, but is considered indicative of disease
when it occurs at a level of activity that is usually well tol-
erated
. Dyspnea should be differentiated from tachypnea,
hyperventilation, and hyperpnea, which refer to respiratory
variations regardless of the patients' subjective sensations
.
Tachypnea
is an increase in the respiratory rate above nor-
mal
;
hyperventilation
is increased minute ventilation relative
to metabolic need, and
hyperpnea
is a disproportionate rise
in minute ventilation relative to an increase in metabolic
level
. These conditions may not always be associated with
dyspnea
.
Orthopnea
is the sensation of breathlessness in the recum-
bent position, relieved by sitting or standing
.
Paroxysmal
nocturnal dyspnea
(PND) is a sensation of shortness of breath
that awakens the patient, often after 1 or 2 hours of sleep,
and is usually relieved in the upright position
.
Two uncommon types of breathlessness are trepopnea
and platypnea
.
Trepopnea is
dyspnea that occurs in one lat-
eral decubitus position as opposed to the other
.
Platypnea
refers to breathlessness that occurs in the upright position
and is relieved with recumbency
.
Technique
A patient with dyspnea may say
: "I feel short of breath,"
"I'm having difficulty breathing," "I can't catch my breath,"
"I feel like I'm suffocating ." Because it is a subjective phe-
nomenon, the perception of dyspnea and its interpretation
vary from patient to patient
. Begin with a nonleading ques-
tion
: Do you have any difficulty breathing? If the response
is affirmative and dyspnea is established as a problem, it
should be characterized in detail
. When did it begin? Has
the onset been sudden or insidious? Inquire about the fre-
quency and duration of attacks
. The conditions in which
dyspnea occurs should be ascertained
. Response to activity,
emotional state, and change of body position should be
noted
. Ask about associated symptoms
: chest pain, palpi-
tations, wheezing, or coughing
. Sometimes a nonproductive
cough may be present as a "dyspnea equivalent
." What other
significant medical problems does the patient have, and
what medications has he been taking? How much has he
smoked?
Dyspnea on exertion is by no means always indicative of
disease
. Normal persons may feel dyspneic with strenuous
exercise . The level of activity tolerated by any individual
depends on such variables as age, sex, body weight, physical
conditioning, attitude, and emotional motivation
. Dyspnea
on exertion would be abnormal if it occurred with activity
that is normally well tolerated by the patient
. It is helpful
to ask if he has noticed any recent or progressive limitation
in his ability to conduct specific tasks that he was able to
perform without difficulty in the past
(e
.g
.,
walking, climb-
ing stairs, performing household chores)
. The degree of
functional impairment can be assessed in this manner
.
Additional questions should be aimed at ascertaining
whether the patient has orthopnea or paroxysmal nocturnal
dyspnea
. Inquire about the number of pillows he uses under
his head at night and whether he has ever had to sleep
sitting up
. Does he develop coughing or wheezing in the
recumbent position? Did he ever wake up at night with
shortness of breath? How long after lying down did the
episode occur, and what did he do to relieve his distress?
Characteristically, the patient with left ventricular failure
sits up at bedside, dangles his feet, and refrains from am-
bulation or other activity that is likely to worsen his symp-
toms
.
Basic Science
Spontaneous respiration is controlled by neural and chem-
ical mechanisms
. At rest, an average 70 kg person breathes
12 to 15 times a minute with a tidal volume of about 600
ml
. A normal individual is not aware of his or her respi-
ratory effort until ventilation is doubled, and dyspnea is not
experienced until ventilation is tripled
. An abnormally in-
creased muscular effort is now needed for the process of
inspiration and expiration
. Because dyspnea is a subjective
experience, it does not always correlate with the degree of
physiologic alteration
. Some patients may complain of se-
vere breathlessness with relatively minor physiologic change
;
others may deny breathlessness even with marked cardio-
pulmonary deterioration
.
There is no universal theory that explains the mechanism
of dyspnea in all clinical situations
. Campbell and Howell
(1963) have formulated the "length-tension inappropriate-
ness theory," which states that the basic defect in dyspnea
is a mismatch between the pressure (tension) generated by
respiratory muscles and the tidal volume (change of length)
that results
. Whenever such disparity occurs, the muscle
spindles of the intercostal muscles transmit signals that bring
the act of breathing to the conscious level
. Additionally,
juxtacapillary receptors U-receptors), located in the alveolar
interstitium and supplied by unmyelinated fibers of the va-
gus nerve, are stimulated by pulmonary congestion
. This
activates the Hering-Breuer reflex whereby inspiratory ef-
fort is terminated before full inspiration is achieved, re-
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