Normal respiratory pattern

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 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.


Breath holding time is known as apnea time. It is about 40 to 60 seconds in a normal person, after a deep



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.


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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