Lung stretchability is a measure of elastic draught, and also an elastic resistance of a pulmonary tissue, which is overcome during breathing. In other words, lung stretchability is a measure of elasticity of a pulmonary tissue, or its compliance.
True lung stretchability is termed «static compliance» ( Cst), measured in a "static" state of lungs when in the end of inspiration a locomotion of air flow is temporarily stopped in large airways.
The dynamic compliance ( Cdyn) is measured while an air flow is passing through airways. C dyn depends also from resistance of respiratory paths, therefore it lesser reflects a lung stretchability. |
First reason is breathing by a atmospheric gas mixture with the low percent of oxygen. Concentration of oxygen in an inhaled mixture <17% (for an unexercised organism) leads to clinical demonstration
of Acute Respiratory Failure. A typical example is lifting on the big heights (> 3 km) without pre-award acclimatisation and additional oxygen supply
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Here is only short description of mask anaesthesia by dripping volatile anesthetics as nowadays it is still applied only in developing countries. Special schimmelbusch mask, covered with several beds of gauze is applied at the patient's face. Then high-volatility anaesthetic is dripped on it (as a rule - aether or halothanum). During an inspiration air transits through a gauze and, having sated with anaesthetic pairs, arrives in respiratory airways. Transpiration of an anaesthetic decreases mask temperature that leads to condensation of moisture. This also decreases the pressure of a saturated anaesthetic gas (saturation pressure is directly proportional to temperature).
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The work of breathing is made mainly by inspiratory muscles during inhalation; the expiration almost always is passive. At the same time in case of acute bronchospasm or a mucosal oedema an expiration also becomes active that considerably increases the general work of airways ventilation.
Only 2—3% of all oxygen consumed by an organism are spent for work of a respiratory musculature. At a pathology (especially restrictive one) more than 30-40% from all consumed oxygen can be spent for work of respiratory muscles. That is why at a certain stage, the essential increasing of breathing work is the direct indication to beginning lung ventilation.
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The Pathology of impulse conduction by neurotransmitter system arises at traumas and spinal cord diseases (especially cervical vertebrae) and abducent nerves: - traumatic intersection
- tumours
- ischemic problems
- inflammation of the bacterial or virus origin
- amyotrophic lateral sclerosis
- traumas
- demyelination
- poliomyelitis
- polyneuropathy (Guillain-Barré Syndrome).
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Depression of a respiratory center can be a result of: - medical drug action (opioids, sedatives and etc.)
- sudden cessation of blood circulations in brain
- heavy brain trauma
- sharp neiroinfections
- brain tumors
- damage of a brainstem
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Obstructive form of Acute Respiratory Failure is connected with sharp violation of passableness of respiratory airways. It is one of most often frequent and at the same time one of the most dangerous kind of Acute Respiratory Failure. Various causes can lead to obstruction of the upper or lower airways. No matter what's the cause of obstructive pathology, the resistance of respiratory airways increases dramatically (according to Poiseuille's law).
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Restrictive form of Acute Respiratory Failure is connected with heavy and acute violation of a pulmonary tissue compliance, atelectasis, blockage of alveocapillary membranes. Etiological causes of Restrictive Acute Respiratory Failure are following: - polysegmental pneumonia, fibrous processes at lungs, non-obturative atelectasis
- respiratory distress-syndrome of adults, Mendelson's syndrome
- cardiogenic and non-cardiogenic lungs hypostasis
- some life-threatening complication of pregnancy (pre-eclampsia, eclampsia, etc.)
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Perfusive form of Acute Respiratory Failure is connected with some blood flow restriction in the branches of pulmonary artery and increasing of physiological dead space. Main causes of Perfusive Acute Respiratory Failure are: - thromboembolism of a pulmonary artery
- significant hypovolemia (blood loss, dehydration).
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