الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Summary
The respiratory system is comprised of several
elements including the central nervous system, the chest
wall, the pulmonary circulation, and the respiratory tract. The
physiological action of the lungs maintains the delicate
balance between these disparate anatomic entities. Total lung
capacity is defined as the volume of gas in the lungs
following maximal inspiration. Functional residual capacity
is the volume of gas in the lungs at the end of normal
expiration.
The three main physiological functions of the
respiratory tract are ventilation, perfusion, and diffusion.
Ventilation is the process of procuring air from the external
environment via inspiration to supply the alveolus, after
which it is subsequently returned to the outside of the body
through expiration.
Chronic Obstructive Pulmonary Disease (COPD) is
chronic bronchitis and emphysema, a pair of commonly coexisting
diseases of the lungs in which the airways narrow
over time.
This limits airflow to and from the lungs, causing
shortness of breath (dyspnea). COPD is defined by its
characteristically low airflow on lung function tests. In
Summary
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contrast to asthma, this limitation is poorly reversible and
usually gets increasingly worse over time. COPD is caused
by noxious particles or gas, most commonly from tobacco
smoking, which triggers an abnormal inflammatory response
in the lung.
COPD is a type of obstructive lung disease. It is not
fully understood how tobacco smoke and other inhaled
particles damage the lungs to cause COPD. The most
important processes causing lung damage are:
· Oxidative stress produced by the high concentrations of
free radicals in tobacco smoke.
· Cytokine release due to inflammation as the body
responds to irritant particles such as tobacco smoke in the
airway.
· Tobacco smoke and free radicals impair the activity of
antiprotease enzymes such as alpha 1-antitrypsin,
allowing protease enzymes to damage the lung.
The diagnosis of COPD should be considered in
anyone who has dyspnea, chronic cough or sputum
production, and/or a history of exposure to risk factors for the
disease such as regular tobacco smoking. No single symptom
or sign can adequately confirm or exclude the diagnosis of
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COPD, although COPD is uncommon under the age of
40 years.
General principles guide the management of COPD
patients presenting acutely to the ICU: treat precipitating
factors (e.g. infection); increase expiratory flow (e.g. with β
agonist); reduce pulmonary inflammation (e.g. with
corticosteroid); and manage gas exchange (e.g. improve
oxygenation). The administration of high FiO2 to these
patients may result in hypercapnia.
The reasons for this effect have been debated for many
years: There is a reduction in respiratory drive from the
carotid chemoreceptors or a worsened ventilation-perfusion
matching is the cause. Noninvasive Ventilation (NIV)
benefits patients with COPD, and it seems reasonable to
expect that NIV would increase Tidal Volume (VT) and
improve CO2 elimination .
CO2-retaining COPD patients following a period of
non invasive mechanical ventilation with PaO2 in the
normal range can safely receive supplemental oxygen
without retaining CO2 or a depression of respiratory drive. A
new ventilation-perfusion relationship is established during
ventilation to normoxia, and it is not altered by further
increasing the FiO2.