COPD: Emphysema (폐기종)

종말 세기관지(terminal bronchiole) 원위부 공기공간(airspace)의 파괴로 인하여 비정상적이며 영구적인 말초 기도 및 폐포의 확장상태를 말한다. 섬유화에 의한 파괴가 아니며 기도의 파괴 없이 나타나는 확장은 과팽창(overinflation)이라고 하여 폐기종과는 구분되어야 한다. 폐기종은 질병명이라기 보다는 병리학적인 용어이며, 만성 기관지염(chronic bronchitis)과 함께 만성 폐쇄성 폐질환(COPD)이라는 병명으로 불리는 만성적이며 비가역적인 기류 폐쇄를 특징으로 하는 폐질환군의 구분에 해당한다.과거에는 폐기종과 만성 기관지염이라는 용어들이 진단명과 혼용되어 임상적으로 흔히 사용되었으나, 최근에는 임상적으로는 사용되지 않고 병리학적인 용어로만 사용하고 있으며 임상적으로는 만성 폐쇄성 폐질환(COPD)이라는 병명으로 진단하고 치료한다.

원인
유해 입자와 가스의 흡입에 의하여 발생하며 임상적으로 가장 의미있는 위험인자는 흡연이다. 파이프나 시가 등 다른 형태의 흡연도 모두 위험인자이며 간접흡연도 원인이 될 수 있다.그 외 직업적으로 분진이나 화학물질, 대기오염 등에 지속적으로 노출되는 것이 만성 폐쇄성 폐질환(COPD)의 원인이 될 수 있다. 이러한 유해 가스의 흡입이 폐의 비정상적인 염증 반응을 유발하여 질병을 일으키게 되지만, 이러한 위험인자에 노출되었다고 모두 다 만성 폐쇄성 폐질환이 발생하는 것은 아니며, 개인별 요인이 위험인자에의 노출과 복합적으로 작용하여 질병이 발생하는 것으로 여겨진다.

증상
만성적인 기침과 가래, 호흡곤란 등이 주요 증상이다.만성 기침과 객담은 만성 기관지염 우세형 만성 폐쇄성 폐질환에서 더 흔히 나타나며 호흡곤란은 폐기종 우세형 만성 폐쇄성 폐질환에서 흔하다. 호흡곤란은 초기에는 운동 시에만 발생하나 질환이 진행되면서 안정 시에도 발생한다.그 외 숨쉴 때 천명음(쌕쌕거림)과 흉부 압박감 등의 증상도 있을 수 있지만 만성 폐쇄성 폐질환에 특이적인 증상은 아니다.

Diagnostic Tests of Emphysema : Assiggnment of Sept 11, 2009

To diagnose emphysema, the physician takes a complete patient and family medical history and performs a physical examination and diagnostic tests. The medical history includes important information about previous and current cigarette smoking and a history of symptoms. In patients who have a family history of emphysema, a blood test may be performed to detect alpha-1 antitrypsin deficiency.
During physical examination, the physician listens to the lungs with a stethoscope and looks for signs of emphysema (e.g., barrel chest, decreased breath sounds). If the medical history and physical examination suggest a diagnosis of emphysema,diagnostic tests may be performed.

Tests used to diagnose emphysema include the following:
* Blood tests (e.g., complete blood cell count [CBC], arterial blood gas [ABG])
* Imaging tests (e.g., chest x-ray, computed tomography [CT scan])
* Oximetry (noninvasive method to measure levels of oxygen in the blood)
* Pulmonary function tests (e.g., peak flow, spirometry)

Blood Tests
Blood tests can be used to rule out other conditions.
For example, high levels of white blood cells may indicate infection (e.g., pneumonia).
An arterial blood gas (ABG), which involves drawing blood from an artery instead of a vein, measures levels of oxygen and carbon dioxide in the blood.
This test can be used to determine if oxygen therapy is needed.

Imaging Tests
In some cases, imaging tests are used to help diagnose or rule out other lung conditions (e.g., pneumonia, lung cancer) and to detect inflammation in the lungs. Chest x-rays often are performed when the medical history and physical examination suggest a diagnosis of emphysema.
Computed tomography (CT scan), also called computerized axial tomography (CAT scan), can detect inflammation in lung tissue earlier than standard chest x-rays. In CT scan, x-rays are taken from many different angles and processed through a computer to produce cross-sectional images of the lungs.

Oximetry
In oximetry, an electronic device called a pulse oximeter is attached to a part of the body (e.g., finger tip, ear lobe, forehead) and used to measure oxygen (O2) levels in the blood. Oxygenated blood is brighter red than oxygen-deprived blood, which is bluish-purple in color.
The pulse oximeter transmits beams of light through blood vessels (capillaries), measures differences in color, and calculates blood oxygen levels.
The blood oxygen level then is displayed on an electronic screen as O2 saturation (O2 sat) rate. Normal rates are greater than 90%.
Lower rates indicate a decrease in lung function.

Pulmonary Function Tests
Pulmonary function tests (PFTs) are used to measure air flow within the lungs and evaluate lung function. These tests can help to confirm a diagnosis of emphysema and determine the severity of the condition.
Pulmonary function tests include peak flow, spirometry, lung volumes, and diffusion capacity.
Peak flow, also called peak expiratory flow rate (PEFR), uses a device that consists of a tube and a gauge to measure the maximum force with which a patient can exhale. Normal peak flow rates vary from person to person and low rates can indicate decreased lung function.
Spirometry measures the air capacity of the lungs. In this test, the patient inhales as deeply as possible, places a tube into the mouth that is attached to an apparatus called a spirometer (spirometry machine), and exhales as quickly and with as much force as possible.
In most cases, this test is repeated three times to get an accurate measurement.
Spirometry measures a number of different values including the forced expiratory volume after one second (FEV1), the forced vital capacity (FVC), and the forced expiratory flow at 25?75% of maximum lung volume. If these rates are lower than expected for the patient's age, sex, height, and weight, decreased lung function is indicated.
Lung volume tests also may be performed to measure lung capacity and function.
In these tests, the patient inhales and exhales into a machine that measures the total lung capacity (TLC) and residual volume following exhalation.
Rates that are higher than normal can indicate emphysema.