Chapter V - Respiratory System

PROCEDURES

Arterial blood gas analysis
This analysis measures the concentration of oxygen and carbon dioxide in the art­erial blood. These concentrations explain how well the lungs are getting oxygen into the blood and carbon dioxide out of it. Oxy­gen concentration is generally measured by oximetry. when the measurement of the car­bon dioxide is also required, a blood sample from the radial artery is taken, generally from the wrist. with this sample in the labo­ratory, oxygen and carbon dioxide concen­trations are measured along with the acidity of blood.

Bronchoscopy
A flexible bronchoscope is inserted through the mouth into the trachea and bronchial tubes in order to visually examine the bron­chi. This is also used for suctioning, biopsy, and removal of foreign bodies. Bronchoscopy also helps in collection of fluid or sputum for examination and diagnosis.

Chest radiographs
Chest radiographs refers to a series of x-ray images used to evaluate the chest, heart, lungs, and rib cage. Chest x-rays provide a good outline of the heart and major blood vessels and can usually reveal serious, dis­eases of the chest in different spaces. Chest x-rays can clearly show pneumonia, lung tu­mors, pneumothorax, pleural effusions, and emphysema.

CT Scan
CT scan of the thoracic area provides a cross­-sectional view of the chest. This is used primarily to highlight the blood vessels and tissue masses.

Flow volume testing
Flow volume testing is conducted with the help of advanced spirometers, which continuously display lung volumes and flow rates during a forced breathing ma­neuver.

Laryngoscopy
A laryngoscope is used for the visual exami­nation of the larynx. The image of the larynx is viewed by transmitting the image via a la­ryngeal mirror. This helps in the diagnosis by collecting sputum samples, performing biopsies, identifying tumors, and accounting for the changes in the voice.

Lung volume and flow rate measurements
In order to diagnose respiratory distress, the physician measures the volume of the air that the lungs can hold. He also checks the speed at which the amount of air can be ex­haled. These measurements are made with the help of a spirometer, which comprise a mouthpiece and tubing connected to a re­cording device. The volume of air inhaled or exhaled and the length of time each breath takes are recorded and analyzed. Often these tests are repeated before and after the ad­ministration of the drug.

Peak flow meter is also used for measuring the speed at which air can be exhaled. This device helps asthmatic patients moni­tor the severity of their disease at home.

Lung volume measurements demonstrate the stiffness and elasticity of the lungs and the rib cage,. Flow rate measurements reflect the degree of narrowing or obstruction of the airways.

Magnetic resonance imaging
Magnetic Resonance Imaging produces highly detailed pictures that are especially helpful when a doctor suspects blood vessel abnor­malities in the chest, such as aortic aneurysm.

Mediastinoscopy
Mediastinoscopy is very helpful in the early diagnosis of the bronchogenic carcinoma. This allows direct visualization of the struc­tures located in the mediastinum.

Muscle strength assessment
The strength of the respiratory muscles is measured when a person forcibly exhales and inhales against a pressure gauge. A disease like muscular dystrophy weakens the muscles and exerts less expiratory and inspiratory pressures.

Sleep studies
Breathing is an automatic process that is controlled by the centers in the brain, which respond to the changing levels of the oxygen and carbon dioxide in the blood. Breathing may stop temporarily, especially during sleep (a condition called sleep apnea). The test for sleep apnea consists of placing an elec­t rode on a finger or an earlobe to measure t he oxygen concentration in the blood, plac­ing an electrode in one nostril to measure airflow, and placing an electrode or gauge on the chest to measure the motion of breath­ing.

PHARMACOLOGY
Antihistamines
Histamines cause swelling and inflammation of the nasal passages. Antihistamines counteract that effect. Antihistamines are the pri­mary agents used to relieve allergic rhinitis symptoms. These products dry the respira­tory tract and are effective in treating the cough caused by the allergens and the com­mon cold at its early stages, Some commonly prescribed antihistamines are brompheniramine, carbinoxamine and pseudoephedrine, cetirizine, and chlorpheniramine.

Antitussives
Antitussive drugs suppress cough. Codeine, a narcotic, is a painkiller that suppresses the cough by acting on the cough center in the brain. However, codeine may cause drowsi­ness, nausea, vomiting, and constipation. Dextromethorphan, which is not an analge­sic, can effectively suppress the cough center in the brain. Demulcents form a protective covering over the irritated lining. Local anesthetics, such as benzocaine, inhibit the cough reflex. Steam inhalation helps reduce or stop cough by reducing irritation in the pharynx and airways. Some commonly prescribed antitussives are dextromethorphan, guaifenesin and codeine, and guaifenesin and hydrocodone.

Bronchodilators
Bronchodilators such as inhaled sympatho­mimetic agents or oral theophylline are prescribed when cough occurs with airway narrowing. They open up the breathing passages and dilate the bronchi. Albuterol, epinephrine, ipratropium (Atrovent), and theophyl­line are commonly used as bronchodilators.

Decongestants
Decongestants such as phenylephrine relieve stuffy noses, reduce the congestion of swell­ing in the nasal passages, especially by con­stricting blood vessels and limiting the blood supply to the area. Phenylpropanolamine (Acutrim), pseudoephedrine, and diphenhy­dramine are a few decongestants,

Expectorants
Expectorants help loosen the mucus by mak­ing bronchial secretions thinner and easier to cough up, Iodides are commonly used ex­pectorants, and guaifenesin and terpin hydrate are ingredients in many over-the-counter preparations.

Mucolytics
Mucolytics liquify or break down the obsti­nate mucus so that it can be expectorated more easily. Acetylcysteine is the most com­monly used mucolytic.