Normal respiratory pattern is called eupnea. Respiratory pattern is altered by many ways. Altered patterns of respiration are:
1. Tachypnea: Increase in the
rate of respiration
2. Bradypnea: Decrease in the
rate of respiration
3. Polypnea: Rapid,
shallow breathing resembling panting in dogs. In this type of breathing, only
the
rate of respiration increases but the
force does not increase significantly.
4. Apnea: Temporary
arrest of breathing
5. Hyperpnea: Increase in
pulmonary ventilation due to increase in rate or force of respiration. Increase
in rate and force of respiration
occurs after exercise. It also occurs in abnormal conditions like fever or
other disorders.
6. Hyperventilation: Abnormal
increase in rate and force of respiration, which often leads to dizziness
and sometimes chest pain
7. Hypoventilation: Decrease in
rate and force of respiration
8. Dyspnea: Difficulty
in breathing
9. Periodic breathing: Abnormal
respiratory rhythm.
APNEA
Apnea is defined as
the temporary
arrest of breathing. Literally, apnea means absence of breathing. Apnea can also be produced
voluntarily, which is called breath
holding or voluntary apnea.
APNEA TIME
Breath holding time is
known as apnea time. It is about 40 to 60 seconds in a normal person, after a
deep
inspiration.
CONDITIONS WHEN APNEA
OCCURS
1. Voluntary
Effort
Arrest of breathing by
voluntary effort is known as voluntary apnea or breath holding. Breath
holding time
can be increased beyond 40 to 60
seconds by practice, exercise, willpower and yoga.
At the end of voluntary apnea, the
subject is forced to breathe, which is called the breaking point. It is because of the
accumulation of carbon dioxide in blood, which stimulates the respiratory
centers. Besides
increased carbon dioxide content in
blood, hypoxia and increased hydrogen ion concentration are also
responsible for stimulation of
respiratory centers. Apnea is always followed by hyperventilation.
2. Apnea after
Hyperventilation
Apnea occurs after hyperventilation.
It is due to lack of carbon dioxide. During hyperventilation, more
carbon dioxide is washed out. So,
partial pressure of carbon dioxide in the blood decreases and the number of
stimuli to the respiratory centers also decreases, leading
to apnea. During apnea, carbon dioxide accumulates in the blood. When partial
pressure of carbon dioxide increases, the respiratory centers are stimulated
and respiration starts.
3. Deglutition
Apnea
Arrest of breathing
during deglutition is known as deglutition (swallowing) apnea.
It occurs reflexly during
pharyngeal stage of
deglutition. When the bolus is pushed into esophagus from pharynx during
pharyngeal stage of deglutition, there is possibility for bolus to enter the
respiratory passage through larynx, causing serious consequences like choking.
This is prevented by deglutition apnea, during which the larynx is closed by
backward movement of epiglottis. breathing
4. Vagal Apnea
Vagal apnea is an experimental apnea, which is produced
by the stimulation of vagus nerve in animals.
Stimulation of vagus nerve
causes apnea by inhibiting the inspiratory center.
5. Adrenaline
Apnea
Adrenaline apnea is the apnea that
occurs after injection of adrenaline. Administration of adrenaline
produces marked increase in arterial
blood pressure. It stimulates the baroreceptors, which in turn
reflexly
inhibit vasomotor center and the
respiratory centers, causing fall in blood pressure and apnea.
CLINICAL
CLASSIFICATION OF APNEA
Clinically, apnea is
classified into three types:
1. Obstructive apnea
2. Central apnea
3. Mixed apnea.
1. Obstructive
Apnea
Obstructive apnea occurs because of
obstruction in the respiratory tract. Respiratory tract obstruction is mainly due
to excess tissue growth like tonsils and adenoids. Common obstructive
apnea is the sleep apnea.
Sleep apnea
Sleep apnea is the
temporary stoppage of breathing that occurs repeatedly during sleep. It is also
called sleep
disordered breathing (SDB).
It commonly affects overweight people. Major cause for sleep apnea is
obstruction of upper respiratory tract by excess tissue growth in
airway, like
enlarged tonsils and large tongue. Characteristic feature of sleep apnea is
loud snoring.
Snoring without sleep apnea is called simple or primary snoring. But
snoring with sleep apnea is serious and it may become life threatening. If left
unnoticed,
it may lead to hypertension, heart failure and stroke (refer Chapter
160 for sleep apnea syndrome).
2. Central Apnea
Central apnea occurs due to brain
disorders, especially when the respiratory centers are affected. It is seen in
premature babies. Typical feature of central apnea is a
short pause in between breathing.
3. Mixed Apnea
Mixed apnea is a combination of
central and obstructive apnea. It is usually seen in premature babies and in full-term born
infants. Main
reason for mixed apnea is the abnormal control of breathing due to
immature or
underdeveloped brain or respiratory system.
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