Page 123 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

Purification of Respiratory Air rated by a valve (close to the patient’s mouth as
possible) to prevent enlargement of dead space (!
Inhaled foreign particles are trapped by mucus p. 114). Ventilation frequency, tidal volume, inspira-
in the nose, throat, trachea, and bronchial tree. tory flow, as well as duration of inspiration and ex-
The entrapped particles are engulfed by mac- piration can be preselected at the respirator. The
drawback of this type of ventilation is that venous re-
rophages and are driven back to the trachea by turn to the heart is impaired to some extent (!
the cilia lining the bronchial epithelium. Cilial p. 204). Today, the standard technique of mechanical
escalator: The cilia move at a rate of 5–10 s –1 respiration is continuous positive pressure ventilation
and propel the mucus towards the mouth at a (CPPV). In contrast to IPPV, the endexpiratory pressure
rate of 1 cm/min on a film of fluid secreted by is kept positive (PEEP) in CPPV. In any case, all venti-
the epithelium. Heavy smoking, mucoviscido- lated patients should be continuously monitored (ex-
sis genetic defects can impair cilial transport. A piratory gas fraction; blood gas composition, etc.).
The iron lung (Drinker respirator) makes use of
volume of 10–100 mL of mucus is produced negative-pressure respiration (! A2). The patient’s
each day, depending on the type and frequency body is enclosed from the neck down in a metal tank.
of local irritation (e.g., smoke inhalation) and To achieve inhalation, pressure in the tank is
vagal stimulation. Mucus is usually swallowed, decreased to a level below ambient pressure and,
and the fluid fraction is absorbed in the thus, below alveolar pressure. This pressure differ-
ence causes the chest to expand (inspiratory phase),
gastrointestinal tract.
Respiration Artificial Respiration and the cessation of negative pressure in the tank al-
lows the patient to breathe out (expiratory phase).
This type of respirator is used to ventilate patients
paralytic diseases, such as polio.
5 Mouth-to-mouth resuscitation is an emer- who require long-term mechanical ventilation due to
gency measure performed when someone
stops breathing. The patient is placed flat on Pneumothorax
the back. While pinching the patient’s nostrils
shut, the aid-giver places his or her mouth on Pneumothorax occurs when air enters the pleural
the patient’s mouth and blows forcefully into space and P pl falls to zero (! p. 108), which can lead
the patient’s lungs (! A3). This raises the alve- to collapse of the affected lung due to elastic recoil
olar pressure (! p. 108) in the patient’s lungs and respiratory failure ( ! B). The contralateral lung
is also impaired because a portion of the inspired air
relative to the atmospheric pressure outside travels back and forth between the healthy and col-
the chest and causes the lungs and chest to ex- lapsed lung and is not available for gas exchange.
pand (inspiration). The rescuer then removes Closed pneumothorax, i.e., the leakage of air from the
his or her mouth to allow the patient to exhale. alveolar space into the pleural space, can occur spon-
Expulsion of the air blown into the lungs (ex- taneously (e.g., lung rupture due to bullous emphy-
piration) occurs due to the intrinsic elastic re- sema) or due to lung injury (e.g., during mechanical
coil of the lungs and chest (! p. 109 A2). This ventilation = barotrauma; ! p. 134). Open pneumo-
process can be accelerated by pressing down thorax (! B2) can be caused by an open chest
wound or blunt chest trauma (e.g., penetration of
on the chest. The rescuer should ventilate the the pleura by a broken rib). Valvular pneumothorax
patient at a rate of about 16 min . The exspira- (! B3) is a life-threatening form of pneumothorax
–1
tory O 2 fraction (! p. 107 A) of the the rescuer that occurs when air enters the pleural space with
is high enough to adequately oxygenate the every breath and can no longer be expelled. A flap of
patient’s blood. The color change in the acts like a valve. Positive pressure develops in the
patient’s skin from blue (cyanosis; ! p. 130) to pleural space on the affected side, as well as in the
pink indicates that a resuscitation attempt was rest of the thoracic cavity. Since the tidal volume in-
creases due to hypoxia, high pressure levels (4 kPa =
successful. 30 mmHg) quickly develop. This leads to increasing
Mechanical ventilation. Mechanical intermittent impairment of cardiac filling and compression of the
positive pressure ventilation (IPPV) works on the same healthy contralateral lung. Treatment of valvular
principle. This technique is used when the respiratory pneumothorax consists of slow drainage of excess
muscles are paralyzed due to disease, anesthesia, pressure and measures to prevent further valvular
etc. The pump of the respirator drives air into the action.
110 patient’s lung during inspiration (! A1). The exter-
nal inspiratory and expiratory pathways are sepa-
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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