In addition to respiratory functions such as gas exchange and regulation of hydrogen ion concentration, the lungs also:
 
¨ Influence the concentration of biologically active substances and drugs used in medicine in arterial blood.
¨ Filter out small blood clots formed in the systemic veins.
¨ Serve as a physical layer of soft, shock-absorbent protection for the heart, which the lungs flank and nearly enclose.
 
The lungs of mammals have a spongy texture and are honeycombed with epithelium having a much larger surface area in total than the outer surface area of the lung itself. The lungs of humans are typical of this type of lung. The environment of the lung is very moist, which makes it a hospitable environment for bacteria. Many respiratory illnesses are the result of bacterial or viral infection of the lungs.
 
Breathing is largely driven by the diaphragm below, a muscle that by contracting expands the cavity in which the lung is enclosed. The rib cage itself is also able to expand and contract to some degree.
 
As a result, air is sucked into and pushed out of the lungs through the trachea and the bronchial tubes or bronchi; these branch out and end in alveoli which are tiny sacs surrounded by capillaries filled with blood. Here oxygen from the air diffuses into the blood, where it is carried by hemoglobin.
 
The deoxygenated blood from the heart reaches the lungs via the pulmonary artery and, after having been oxygenated, returns via the pulmonary veins.
 
 
ANATOMY
 
The lungs are located inside the thoracic cavity, protected by the bony structure of the rib cage and enclosed by a double-walled sac called pleura. The inner layer of the sac (visceral pleura) adheres tightly to the lungs and the outer layer (parietal pleura) is attached to the wall of the chest cavity. The two layers are separated by a thin space called the pleural cavity that is filled with pleural fluid; this allows the inner and outer layers to slide over each other, and prevents them from being separated easily. The left lung is smaller than the right one to give way for the heart.

The lungs attach to the heart and trachea through structures that are called the "roots of the lungs." The roots of the lungs are the bronchi, pulmonary vessels, bronchial vessels, lymphatic vessels, and nerves. These structures enter and leave at the hilus of the lung.
 
The lungs are divided into lobes by the horizontal and oblique fissures. The right lung has three lobes and the left lung has two. A unique feature of the left lung is the cardiac notch, which helps create the lingula (Latin for "tongue") of the left lung.
 
The lungs are connected to the upper airway by the trachea and bronchi. The trachea runs down the neck and divides into left and right bronchi behind the sternal angle. The right main bronchus is shorter and runs more vertically than the left. For this reason, it is more common to aspirate foreign objects into the right lung. The bronchi enter the lung and branch out to form the bronchial tree. The bronchi divide into smaller bronchioles, which terminate into alveoli. An alveolus is composed of respiratory tissue and is the site of gas exchange in the lung.
 
The blood supply to the lungs is from two sources: the pulmonary vessels and the bronchial vessels. The bronchial vessels support the nonrespiratory tissue and the pulmonary vessels provide support to the respiratory tissue.
 
The pulmonary arteries carry deoxygenated blood that has returned to the heart from the venous system to the lungs to be reoxygenated. The pulmonary veins carry oxygenated blood back to the heart to go to the arterial system. The right and left pulmonary arteries arise from the pulmonary trunk and carry "venous" blood to their respective lungs. The pulmonary veins, two on each side, carry "arterial" blood to the left atrium of the heart.
 
The bronchial arteries that supply the nonrespiratory tissue of the lung arise from different sources. The left bronchial arteries come off of the thoracic aorta, however, the right bronchial artery has a variable source.
 
Lecture II
 
RESPIRATORY SYSTEM
 
The respiratory system is the biological system of any organism that engages in gas exchange. Even trees have respiratory systems, taking in carbon dioxide and emitting oxygen during the day, consuming carbon dioxide and producing oxygen constantly.
 
In humans and other mammals, the respiratory system consists of the airways, the lungs, and the respiratory muscles that mediate the movement of air into and out of the body. Within the alveolar system of the lungs, molecules of oxygen and carbon dioxide are passively exchanged between the gaseous environment and the blood. Thus, the respiratory system facilitates oxygenation of the blood with a concomitant removal of carbon dioxide and other gaseous metabolic wastes from the circulation.
 
Organization
The respiratory system can be conveniently subdivided into a conducting zone and a respiratory zone.
 
The conducting zone comprises:

¨ The nose
¨ The nasopharynx
¨ The larynx, or voicebox
¨ The trachea, an air tube that connects with the bronchi
¨ The right main bronchus and the left main bronchus tubes that carry air to and from the lungs
¨ The bronchioles, branches of the bronchi which distribute air to the alveoli
¨ The terminal bronchioles

The respiratory zone comprises:
 
¨ The respiratory bronchioles
¨ The alveolar ducts
¨ The alveoli, terminal sacs in which gas exchange occurs
 
Muscles used for inspiration include:
 
¨ The diaphragm, which mediates intrathoracic pressure to initiate inspiration.
¨ The external intercostal muscles, during vigorous inspiration
 
Although expiration is generally a passive process, muscles aiding forced expiration include:
 
¨ The abdominal muscles
¨ The internal intercostal muscles 
 

Other:
The right and left bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, and alveoli form the right and left lungs respectively.
 
The pulmonary blood vessels generally accompany the airways and also undergo numerous branchings. The pulmonary circulation has a very low resistance compared to the systemic circulation, and for this reason, all the pressures within the pulmonary blood vessels are low.
 
Functions:
The major function of the respiratory system is gas exchange. Respiration consists of a mechanical cycle of inspiration and expiration, with gaseous exchange occurring in between.
 
Inspiration is driven primarily by the diaphragm. When the diaphragm contracts, the ribcage expands and the contents of the abdomen are moved downward. This results in a larger thoracic volume, which in turn causes a decrease in intrathoracic pressure. As the pressure in the chest falls, air moves into the conducting zone. Here, the air is filtered, warmed and humidified as it flows to the lungs.
 
Expiration, on the other hand, is typically a passive process. The lungs have a natural elasticity; as they recoil from the stretch of inspiration, air flows back out until the pressures in the chest and the atmosphere reach equilibrium.
 
During forced inspiration, as when taking a deep breath, the external intercostal muscles and accessory muscles further expand the thoracic cavity.
 
During forced expiration, as when blowing out a candle, expiratory muscles including the abdominal muscles and internal intercostal muscles, generate abdominal and thoracic pressure, which forces air out of the lungs.
 
Upon inspiration, gas exchange occurs at the alveoli, the tiny sacs which are the basic functional component of the lungs. The alveolar walls are extremely thin (approx. 0.2 micrometers), and are permeable to gases. The alveoli are lined with pulmonary capillaries, the walls of which are also thin enough to permit gas exchange. Oxygen diffuses from the alveolar air to the blood in the pulmonary capillaries, as carbon dioxide diffuses in the opposite direction, from capillary blood to alveolar air. At this point, the pulmonary blood is oxygen-rich, and the lungs are holding carbon dioxide. Expiration follows, thereby ridding the body of the carbon dioxide and completing the cycle of respiration.
 
Oxygen Delivery System
 
The primary function of the respiratory system is to supply the blood with oxygen in order for the blood to deliver oxygen to all parts of the body. The respiratory system does this through breathing. When we breathe, we inhale oxygen and exhale carbon dioxide. This exchange of gases is the respiratory system's means of getting oxygen to the blood.

Respiration is achieved through the mouth, nose, trachea, lungs, and diaphragm. Oxygen enters the respiratory system through the mouth and the nose. The oxygen then passes through the larynx (where speech sounds are produced) and the trachea which is a tube that enters the chest cavity. In the chest cavity, the trachea splits into two smaller tubes called the bronchi. Each bronchus then divides again forming the bronchial tubes. The bronchial tubes lead directly into the lungs where they divide into many smaller tubes, which connect to tiny sacs, called alveoli. The average adult's lungs contain about 600 million of these spongy, air-filled sacs that are surrounded by capillaries. The inhaled oxygen passes into the alveoli and then diffuses through the capillaries into the arterial blood. Meanwhile, the waste-rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide follows the same path out of the lungs when you exhale.
 
The diaphragm's job is to help pump the carbon dioxide out of the lungs and pull the oxygen into the lungs. The diaphragm is a sheet of muscles that lies across the bottom of the chest cavity. As the diaphragm contracts and relaxes, breathing takes place. When the diaphragm contracts, oxygen is pulled into the lungs. When the diaphragm relaxes, carbon dioxide is pumped out of the lungs.
 
Other Important facts:
 
In an average resting adult, the lungs take up about 250ml of oxygen every minute while excreting about 200ml of carbon dioxide.
 
The movement of gas through the larynx, pharynx and mouth allows us to speak, or phonate.
 
The respiratory tract is constantly exposed to microbes due to the extensive surface area, which is why the respiratory system includes many mechanisms to defend itself and prevent pathogens from entering the body.
 
Virtually all the body's blood travels through the lungs every minute. The lungs add and remove many chemical messengers from the blood as it flows through pulmonary capillary bed. The fine capillaries also trap blood clots that have formed in systemic veins.
 
Diseases
Diseases of the respiratory system can be classified into four general areas:
 
Obstructive Diseases (e.g., Emphysema, Bronchitis, Asthma)
Restrictive Diseases (e.g., Fibrosis, Sarcoidosis, Alveolar Damage, Pleural Effusion)
Vascular Diseases (e.g., Pulmonary Edema, Pulmonary Embolism, Pulmonary Hypertension)
Infectious, Environmental and Other Diseases (e.g., Pneumonia, Tuberculosis, Asbestosis, Particulate Pollutants)
 
Lecture III
 
NOSE
 
Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for respiration. In most mammals, it also houses the nosehairs, which catch airborne particles and prevent them from reaching the lungs. Within and behind the nose is the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes through the pharynx, shared with the digestive system, and then into the rest of the respiratory system. In humans, the nose is located centrally on the face; on most other mammals, it is on the upper tip of the snout. Nose as a term may be used to designate the leading end of anything, such as an airplane.
 
As an interface between the body and the external world, the nose and associated structures frequently perform additional functions concerned with conditioning entering air (for instance, by warming and/or humidifying it) and by reclaiming moisture from the air before it is exhaled (as occurs most efficiently in camels).
 
In most mammals, the nose is the primary organ for smelling. As the animal sniffs, the air flows through the nose and over structures called turbinates in the nasal cavity. The turbulence caused by this disruption slows the air and directs it toward the olfactory epithelium. At the surface of the olfactory epithelium, odor molecules carried by the air contact olfactory receptor neurons which transduce the features of the molecule into electrical impulses in the brain.
 
In cetaceans, the nose has been reduced to the nostrils, which have migrated to the top of the head, producing a more streamlined body shape and the ability to breathe while mostly submerged. Conversely, the elephant's nose has become elaborated into a long, muscular, manipulative organ called the trunk.
 
Due to the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain. For this reason, the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla, is known to doctors as the danger triangle of the face.
 
All humans have a trace amount of magnetite in their noses, found in the ethmoid bone (between the eyes), possibly part of a rudimentary compass to allow direction finding relative to the earth's magnetic field. The human magnetoception is still very controversial, but some studies show that some people have the ability to orient themselves-even when blindfolded and removed from such external clues as sunlight-to within a few degrees of the North Pole, exactly as a compass does.
 
Sneeze

A sneeze is the semi-autonomous, convulsive expulsion of air from the nose and mouth. An unimpeded sneeze sends two to five thousand bacteria-filled droplets into the air. The medical name for sneezing is sternutation.
 
Sneezing is generally caused by irritation in the passages of the nose. Pollens, house dust, and other particles are usually harmless, but when they irritate the nose the body responds by expelling them from the nasal passages. The nose mistakes strong odors, sudden chills, bright lights (see photic sneeze reflex), and even orgasms in some people for nasal irritants, and it tries to defend itself with a sneeze.
 
It is almost impossible for a person to keep their eyelids open during a sneeze. The reflex of shutting the eyes serves no obvious purpose: the nerves serving the eyes and the nose are closely related, and stimuli to the one often trigger some response in the other.
 
Nose-picking

Nose-picking is the act of extracting mucus or foreign bodies from the nose with a finger. Compulsive nose-picking is known as rhinotillexomania
 
A nosebleed or nose bleed, medically known as epistaxis, is the relatively common occurrence of hemorrhage (bleeding) from the nose, usually noticed when it drains out through the nostrils. There are two types: anterior (the most common), and posterior (less common, and more severe).
 
All nosebleeds are due to tears in the mucosal lining and the many small blood vessels it contains. Fragility or injury may cause the tears, while inflammation, coagulation problems and other disorders may make the injury harder to repair.
 
Little's area

Little's area is an area within the nose near the nasal septum that is richly infiltrated with small capillaries. Inflammation of this area is a common cause of epistaxis (nasal bleeding).
 
Mucus

Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). Mucus aids in the protection of the lungs by trapping foreign particles that enter the nose during normal breathing. Additionally, it prevents tissues from drying out.
 
Mucus is made by goblet cells in the mucous membranes that cover the surfaces of the membranes. It is made up of mucins and inorganic salts suspended in water.
 
In the digestive system, mucus is used as a lubricant for materials which must pass over membranes, e.g. food passing down the esophagus. In the respiratory system, it catches unknown matter and tries to prevent it from entering the body, especially in the nose. In the reproductive system, mucus aids the penis in entering the vagina during intercourse.
 
Mucus is a viscous colloid containing antiseptic enzymes (such as lysozyme) and immunoglobulins.
 
Increased mucus production in the respiratory tract is a symptom of many common diseases, such as the common cold. The presence of mucus in the nose and throat is normal, but increased quantities can impede comfortable breathing and must be cleared by blowing the nose or expectorating phlegm from the throat. Among the components of nasal mucus are tears.
 
 
NASAL CAVITY
 
The nasal cavity is a large air-filled space above and behind the nose in the middle of the face. The nasal cavity is important in warming and cleaning the air as it is inhaled. The nasal cavity also contains organs involved in olfaction.
 
The nasal cavity is enclosed by the nasal bone above and by the maxilla and ethmoid bone on the sides. The palate separates the nasal cavity from the mouth. To the front of the nasal cavity is the nose, while the back is continuous with the pharynx. The paranasal sinuses are connected to the nasal cavity through small orifices called ostia.
 
The nasal cavity is divided in two by a vertical fin called the nasal septum. On the sides of the nasal cavity are three horizontal outgrowths called turbinates or conchae (singular "concha"). These turbinates disrupt the airflow, directing air toward the olfactory epithelium on the surface of the turbinates and the septum. The vomeronasal organ is located at the back of the septum and has a role in pheromone detection.
 
Cilia and mucus along the inside wall of the nasal cavity trap and remove dust and germs from the air as it flows through the nasal cavity. The cilia move the mucus down the nasal cavity to the pharynx, where it can be swallowed.
 
There is a rich blood supply to the nasal cavity. In some animals, such as dogs, the capillary beds flowing through the nasal cavity help cool the blood flow to the brain.
 
Diseases of the nasal cavity include viral infections and nasal cavity cancer.
 
Lecture IV
 
PHYSICAL ASSESSMENT

Evaluation of the respiratory system, espe­cially of the lungs, is carried out by the pro­cess of auscultation and percussion. While diagnosing the ailments of the respiratory system, a physician inspects the symmetry, color and movements of the thoracic cavity. He determines the respiratory rate which, in normal case, should range from 16 to 20. The physician also uses a stethoscope and listens for any extra sound like rales, rhon­chi, or wheezes. He palpates the back and checks for the presence of fremitus. Percus­sion of the chest allows the physician to find out if there is any dull sound or edema present. The physician asks the patient if he/she experiences any shortness of breath or dyspnea.
 
PATHOLOGY

Bronchiectasis
Bronchiectasis is characterized by the dila­tion of the bronchi, especially the lower lungs. Mucopurulent sputum (sputum mixed with mucus and pus) and hemoptysis are the associated symptoms. Treatment includes mucolytics, bronchodilators, antibiot­ics, and postural drainage.
 
 
Bronchopneumonia
Bronchopneumonia is an infectious inflam­matory condition of the lungs, caused by a variety of agents. Bronchopneumonia affect­ing only one side of the lung is referred to as lobar pneumonia, while that affecting both sides of the lungs is called bilateral or double pneumonia. Due to the pathological engorgement, the lungs may develop solidi­fication or consolidation. The condition is characterized by chest pain, mucopurulent sputum, and hemoptysis.
 
Pneumocystis carinii pneumonia (PCP) is an important consideration in this regard. The causative fungus resides in the normal flora and causes no harm as long as the individual remains healthy. However, with the compromise of the immune system, the or­ganism becomes opportunistic. Physicians diagnose the condition with the help of a biopsy and lavage.
 
COPD

COPD stands for chronic ob­structive pulmonary disease or it can be also termed as COLD (chronic obstructive lung disease) and are also used as synonyms. However, COLD should not be mistaken for common cold that we usually get infect with. Hence, generally, COPD term is used. This is a respiratory disorder characterized by cough and dyspnea due to the obstruction in the air passages. The three major diseases, which come in this category are asthma, chronic bronchitis, and emphysema.
 
Asthma is characterized by the spasms of the bronchus. These bronchospasms can by paroxysmal (sudden and violent in nature) causing dyspnea. They can also be characterized by productive cough and thickening of the epithelial cells of the bronchial passages. Causes of this disease can be exposure to al­lergens and irritants, stress, cold, and exer­cise. Treatment includes administration of mucolytics and bronchodilators.
 
Chronic bronchitis, as is evident from the name itself, is the chronic inflammation of the bronchi. It is primarily caused by the smoking and air pollution, though viruses and bacteria can also be the contributing fac­tors. This is characterized by swelling of the mucosa, heavy and productive cough, chest pain, exercise intolerance, wheezing, and shortness of breath. Bronchodilators and ex­pectorants are required to expand the air passages.
 
Long-term heavy smoking or other dis­ease, such as asthma, tuberculosis, or chronic bronchitis, may cause the alveoli to lose its elasticity. The air sacs expand, but they are unable to contract, and the residual air gets trapped inside. This results in a 'barrel chest' appearance and is referred as emphysema. People afflicted with emphysema often suf­fer from another condition called orthopnea, i.e. they find it easier to breathe while sitting or standing.
 
CROUP

Croup refers to an acute obstruction of the lungs caused by allergens, infection, foreign body, or new growth. It is characterized by a resonant, barking cough, laryngeal spasms, suffocation or difficulty in breathing, and the formation of a membrane.
 
Cystic fibrosis
Cystic fibrosis is a hereditary and systemic disorder, which affects the exocrine glands. The condition is characterized by the pro­duction of viscous mucus, which blocks the bronchioles. The treatment includes use of aerosols and postural drainage. This is a very fatal disease and almost results in loss of life.
 
Lung cancer
Smoking is the leading cause of lung cancer, and the most commonly affected site is the epithelium of the bronchial passage. The lung cancer of the bronchial passage is called bronchogenic carcinoma. This is character­ized by the rapid division of the basal cells located at the base of the epithelium and metastasis to the other areas of the body. Treatment includes surgery, radiation, and chemotherapy.
 
Pleural effusions
Pleural effusions refer to the excessive accu­mulation of the fluid in the pleural cavity. Congestive heart failure, ascites, and infec­tious lung diseases can be conducive to pleu­ral effusions. Physicians generally diagnose the pleural effusions with the help of what we call auscultation and percussion. Auscul­tation is listening to the sounds of the chest cavity with the help of a stethoscope, while percussion refers to tapping the chest with the fingers to determine the size position, and consistency of the underlying structures. Different types of pleural effusions are:
 
1.      Empyema: Pus in the pleural space
2.      Hydrothorax: serum in the pleural space
3.      Hemothorax: blood in the pleural space
4.      Pneumothorax: air in the pleural space
5.      Pyopneumothorax: pus and air in the pleural space
 
Treatment often includes thoracocentesis or thoracentesis to remove the excess fluid.
 
Rales, rhonchi, and wheezes:
Rales are abnormal crackling sounds heard on inspiration produced by the passage of air that contains moisture. Rales are noted by a stethoscope and indicate a pneumonia like condition.
 
Accumulation of fluids in the airways pro­duces this abnormal chest sound, which resembles snoring. These snoring sounds are known as rhonchi.
 
Partially obstructed airways produce a whistling musical sound during breathing called wheezing. It may be caused by gen­eral obstruction of the airways (as in asthma and COPD) or local obstruction (as in tu­mors).
 
Respiratory distress syndrome

Lungs require surfactants in order to fill with air and expand, also known as compliance. Surfactants assist in decreasing the surface tension of the alveoli. Deficiency or impairment of the surfactants may cause the col­lapse of the alveoli and inhalation becomes difficult. When this condition is found in the infants, this is known as IROS (infant respi­ratory distress syndrome) or HMO (hyaline membrane disease). IROS or HMO is com­mon among the premature infants or the in­fants born of the diabetic mothers. ARDS (adult respiratory distress syndrome) is caused by the impairment of the surfactants or accidental inhalation of foreign substan­ces, water, smoke, or chemical fumes.
 
Stridor

Blockages of the throat, voice box, and wind­pipe produce a crowing sound during breathing, especially during inhalation, which is known as stridor. The sound is caused by a turbulent airflow through a narrowed air­way. It may be due to the epiglottitis, tumor, or edema.
 
Tuberculosis

Aerosol transmission or particles of dry spu­tum containing the tuberculosis (TB) organism, Mycobacterium tuberculosis cause the spread of the disease. These organisms can remain viable and infectious for a period of 6 to 8 months even when they arc outside the body. This disease develops into three stages: primary tuberculosis, formation of granulomas, and the immunocompromised state of full-blown disease. This lung disease can infect even the meninges, bones, genital tract, and the peritoneum. 
 
Lecture V
 
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.
 
 
AFB Acid fast bacillus.
ARDS Acute/adult respiratory distress syndrome.
COPD Chronic obstructive pulmonary disease.
CPR Cardiopulmonary resuscitation.
CTA Clear to auscultation (about lungs).
CXR Chest X-ray.
DPT Diphtheria, pertussis, tetanus immunization.
FVC Forced vital capacity.

 
 
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