Respiratory System


Respiratory System
The respiratory system or the ventilator system is a kind of biological system that is useful for respiration. It is the oxygen delivery system that takes place through specific organs of respiratory system. The oxygen supply to the blood is through the process of breathing, which is the primary function of the respiratory system. In the process of breathing, there is exchange of gases in the respiratory tract. The respiration is the process of inspiration and expiration. A person inhales oxygen and exhales carbon dioxide, during respiration.

What is oxygen?
In a human body, oxygen plays an important role in the process of breathing and metabolism. Our body is made up of infinite minute cells that need oxygen to survive and function properly. A cell is a compound structure that requires constant nutrition in the form of oxygen. The cells are oxidized due to complex enzymatic processes. In short, cells are damaged due to oxidation. To overcome this problem, a cell needs oxygen in some or the other form to survive.
During inhalation, the oxygen enters into the lungs and diffuses through membranes, and then enters into red blood cells (RBCs). The iron component (heme) of the blood i.e. hemoglobin binds oxygen, which is then taken up by the body tissue. After entering the tissue the enzyme called as monooxygenase uses oxygen for metabolism of oxidation reactions that occur in the human body. After this process, a waste product, carbon monoxide is released from the cell and is expelled out in the form expiration through bloodstream and lungs.

  • Parts of respiratory system

  • What are the functions of lungs?

  • How to measure lung function

  • Examination of lung function

  • What is a respiratory rate (RR)?

  • Respiratory diseases

  • Examinations of respiratory system

  • Treatments used in respiratory diseases

  • Alternative therapies for respiratory disorders

Respiratory system is a complex system and made up of different organs, and usually referred as respiratory tract. The respiratory tract is composed of upper respiratory tract, lower respiratory tract and lungs. Following are the organs associated with different tracts –

  • Upper respiratory tract
    • Nasal cavity
    • Paranasal sinuses
    • Pharynx – There are three parts of pharynx –
      • Nasopharynx
      • Oropharynx
      • Laryngopharynx
    • Larynx – This part of the upper respiratory tract is also called as “voice box” and is associated with a cartilage that helps in producing sound.
  • Lower respiratory tract
    The lower airway or lower respiratory tract is a vital part of respiratory system,  consisting of –
    • The trachea (windpipe)
      It is a cartilage and the largest tube of the respiratory system.
    • Bronchi – After the completion of trachea, bronchi starts that is further classified, as follows –
      • Primary bronchi
      • Secondary bronchi (Lobar bronchi)
      • Tertiary bronchi (Segmental bronchi)
      • Smaller division of bronchi
      • Bronchioles – Smaller sections inside the lungs, that holds the air sacs in the lungs
  • Lungs
    Lungs are the largest organs of the respiratory system. The lungs are set aside within the pleural cavity and are surrounded by the thorax or the chest. There are two layers of the pleura viz. visceral pleura and parietal pleura. The layer that envelops the lungs is called as visceral pleura and the one that lines the inner surface of the chest wall is called as parietal pleura. A small quantity of fluid is secreted by pleura for free movements of the lungs within the pleural cavity and help lungs in process of breathing by contraction and expansion.
    The right lung is slightly larger than the left lung due to anatomical position of the heart in the left side of the midline.
    1. Right lung – It has three lobes
      • Upper (superior)
      • Middle
      • Lower (inferior)
    2. Left lung – It has two lobes, and a tongue-shaped part called as lingual.
      • Upper (superior)
      • Lower (inferior)

Each lung is further divided into segments, and has costal surfaces, which is near to ribcage, mediastinum, heart, diaphragm and great vessels.
The alveoli or the alveolus are tiny air spaces that are situated in the lungs. The process of gas exchange takes place in these tiny little air spaces. There are numerous alveoli in the lungs, approximately 150 million in each lung. The air rushes in the alveolar sacs (inhalation of oxygen) making the lung expand, due to negative pressure in the thorax, which is caused due to contraction of diaphragm. The air rushes out of the alveolar sacs by expelling carbon monoxide due to positive pressure in the thorax, which is caused due to relaxation of diaphragm. The alveoli is made up of capillaries, hence they are called as alveolar capillaries.
Respiratory tree
The respiratory tree is the branching system of the respiratory tract starting from the trachea to the alveolus in the lungs.
The tracheobronchial tree is used to indicate the structural part of the airways that supplies air to the lungs i.e. the trachea, bronchus or bronchi and bronchioles.

Breathing action
The two important stages of breathing are inhalation and exhalation. The process of inhalation and exhalation is an involuntary process and to control them one requires an effort.

  • Inhalation – It is the expansion of chest volume due to intake of air into the vital respiratory organ (lungs).
  • Exhalation – It is the contraction of chest volume due to expulsion of air from the respiratory organ (lungs).

The muscles involved during the process of inhalation and exhalation are –

  • Intercostal muscles or rib muscles – the muscles that are situated between the ribs
  • Diaphragm or thoracic diaphragm muscles

The chest cavity continuously increases and decreases due to constant contraction and relaxation of intercostal muscles and diaphragm muscle. The duration of contraction and relaxation of muscles is approximately sixteen times per minute.

Inhalation/Inspiration – The muscles contract

  • Contraction of diaphragm – Flattens diaphragm and enlarges the chest cavity
  • Contraction of rib muscles – Rises the ribs and increases the volume of chest

Hence, there is an expansion of the chest cavity, and reduces the air pressure, thereby air being drawn into the lungs.

Exhalation/Expiration – The muscles relax

  • Diaphragm curves and rises
  • The ribs descend – decreases the volume of chest

Hence, there is contraction of the chest cavity, and raises the air pressure, thereby causing air to be expelled from the lungs.

The respiratory tract includes the respiratory apertures i.e. mouth and nose, the trachea, branching section of bronchi, bronchioles and ends in the lungs as pulmonary alveoli in the form of sacs. The measuring of the functions of the lungs is of utmost important in diagnosing respiratory diseases. Hence, measuring lung function is a vital medical diagnostic tool.

Air volume – It is the maximum lung volume that is also known as total lung capacity (TLC). It is usually measured in liters. It is measured by using maximum strenuous inspiration or inhalation. The normal range of maximum lung volume is approximately 5 to 6 liters for a healthy adult. In children the total lung capacity is up to 2 to 3 liters, whereas in infants it is around 600 to 1000 milliliters.

Vital Capacity – It is also known as essential air volume and it is the maximum volume of the air a human being can expel from the lungs, after the strenuous inhalation. In healthy adult, the vital capacity is approximately 3.5 to 4.5 liters.

Residual volume – It is the amount of air that remains in the lungs after maximum expiration. In residual volume measurement, the alveoli and the broncheoli does not stick to each other.

Tidal volume – It is the lung volume of air that is displaced between normal breathing process i.e. inspiration and expiration. The normal range of tidal volume in a healthy adult is 500 milliliters.

The examination of lungs helps in diagnosing obstructive diseases of respiratory system. The most efficient procedure of measuring the function of lung is done through a “spirometer”. It is a main apparatus used in pulmonary function tests (PFTs). It is usually measured in liter per minute and represents the reading in the form of graphical diagram. It is used in measuring the volume of air expired and inspired in a given time.
Generally, the spirometer indicates the rate of air expelled from the respiratory organ (lungs). In case of obstruction in air passages the rate of airflow decreases, which is shown on the graphical diagram, thereby indicating problems in the airways. It is helpful in detecting patients suffering from asthma, chronic obstructive pulmonary diseases (COPD).
It takes only few seconds to examine a patient, and it is considered the safest way of detecting a respiratory trouble.

Steps involved in examination

  • The person is asked to inspire or inhale deeply
  • Then the person is asked to exhale with maximum strenuous effort in the spirometer
  • The person is asked to expel the air as much as possible for few seconds, until he or she feels the strong urge to inhale
  • This procedure is repeated twice or thrice

The respiratory rate is also called as ventilation rate, pulmonary ventilation rate, breathing frequency. It is the rate of ventilation i.e. the number of inhalation-exhalation cycles taken in a specific time (60 seconds). Medically, the normal respiratory rate is termed as eupnea.

  • Bradypnea – The respiratory rate lower than the normal range
  • Tachypnea – The respiratory rate higher than the normal range

The respiratory rate is different for different age groups, which are as follows

  • Newborn to 6 weeks – 30 to 60 breathes/minute
  • 6 months – 25 to 40 breathes/minute
  • 3 years – 20 to 30 breathes/minute
  • 6 years – 18 to 25 breathes/minute
  • 10 years – 12 to 15 breathes/minute
  • Adults – 12 to 25 breathes/minute

The affection of respiratory tract is one of the most troublesome problems. Due to breathing difficulties a person gets irritated with cough many such symptoms of respiratory conditions.
Below are the respiratory conditions with their signs and symptoms –

  • Upper respiratory tract infections (URTI)
    It is an acute respiratory illness that involves the infection of upper respiratory tract i.e. nose, sinuses, larynx and pharynx. Respiratory affections such as rhinitis, tonsillitis, laryngitis, pharyngitis, sinusitis, otitis media and common cold are included under URTI.
    • Rhinitis – Inflammation of mucosal lining of nose
    • Nasopharyngitis – Inflammation of nasal mucosa, pharynx, uvula and tonsils
    • Pharyngitis – Inflammation of pharynx, hypopharynx, uvula, tonsils
    • Laryngitis – Inflammation of larynx
    • Epiglottitis – Inflammation of upper portion of larynx and supraglottic region
    • Laryngotracheitis – Inflammation of larynx, trachea, subglottic area
    • Tracheitis – Inflammation of subglottic area and trachea
  • Chronic obstructive pulmonary diseases (COPD)
    It is also called as chronic obstructive airway disease (COAD) or chronic obstructive lung disease (COLD). COPD is a group of respiratory diseases characterized by poor or blocked airflow and difficulty in breathing. Chronic bronchitis and Emphysema are the two prevalent diseases that come under COPD. Other type of COPD is Bronchiectasis. Smoking is the primary cause in both the types of COPD. In COPD, the damaged lungs cannot be reversed, but proper treatment can prevent the further damage and controls symptoms.
    • Chronic bronchitis – It is the inflammation of the mucus membranes of bronchial tubes that carry air from and to the lungs. It is the presence of frequent productive cough, which occurs for three months and more in a year for two consecutive years.

    • Emphysema – It is a type of COPD that is characterized by destruction of alveoli (air sacs) present in lungs wherein the exchange of gases takes place. In this condition, the air spaces are enlarged leading to shortness of breath and cough.
  • Bronchiectasis
    It is a respiratory disease that is characterized by permanent enlargement of airways in the lung(s). The characteristic feature of bronchiectasis is chronic cough with yellow/green offensive sputum associated with breathing difficulty, chest pain, clubbing of nails and coughing of blood. On auscultation your doctor may notice wheezing in chest area. People suffering from this COPD are often prone to severe lung infections.
  • Bronchial asthma
    Bronchial asthma is one of the leading respiratory diseases that includes chronic inflammation of the airways (bronchi) characterized by spasm of bronchus and reversible airflow obstruction. The clinical features of bronchial asthma are chest congestion, cough, shortness of breath and wheezing. There are several internal and external factors that can trigger attack of asthma, such as air pollution, viral infections, dust, molds, pet dander, pollen, etc.
  • Pneumonia
    Pneumonia is a common respiratory illness characterized by inflammation of lung(s) that mainly affects the air sacs or alveoli. The inflammation is caused due to pathogenic bacteria agent (Streptococcus pneumoniae), viruses and other microbes. Sometimes pneumonia can occur due to certain drug reactions and autoimmune diseases. The sign and symptoms of pneumonia are chest pain, cough, fever with chills, and difficulty in breathing, and increased respiratory rate. Pneumonia is treated with broad spectrum antibiotics, usually with hospitalization. The diagnosis of this respiratory illness is done by sputum culture and chest X-rays.
  • Tuberculosis
    Tuberculosis (TB) is a leading respiratory disease that affects many people, as it is one of the communicable diseases that spread easily. It is the inflammation of lung(s) caused by Mycobacterium tuberculosis. The infection can spread through air droplets, sneezing, cough, etc. The classical signs and symptoms of active tuberculosis are chronic cough, hemoptysis (coughing of bloody sputum), fever with rigors, night sweats, and anorexia with weight loss. The diagnosis is done on the basis of chest X-rays, sputum culture and microscopic examination. Tuberculin skin test is the confirmation of latent TB. Multiple antibiotics are given to treat TB for a longer period.
  • Acute respiratory distress syndrome (ARDS)
    ARDS was previously known as RDS (respiratory distress syndrome), shock lung, adult respiratory distress syndrome. It is a severe and serious life-threatening illness that is characterized by sudden injury or inflammation of the lungs. It is usually triggered by pneumonia and sepsis that ultimately causes ARDS. Due to impaired gases exchanges, a person suffers from dyspnea (breathlessness), tachypnea (increased respiratory rate) and hypoxemia (low oxygen saturation). A person requires life support with the help of mechanical ventilation until the lungs recover.
  • Pleural effusion
    Pleural effusion is the accumulation of excess fluid in the pleural cavity that surrounds the lungs. There are different types of fluid that accumulates pleural cavity viz. hydrothorax (serous fluid), pyothorax (pus), hemothorax (blood), chylothorax (chyle), and air in pleural cavity is called as pneumothorax. It limits the expansion of the lungs during the process of breathing, thereby causing breathing troubles. In case of severe pleural effusion, physicians or surgeons drain the excess fluid by intercostal drainage procedure.
  • Pleurisy
    It is also called as pleuritis that is characterized by inflammation of pleura i.e. the lining of the lungs. It can be caused due to infections, pulmonary embolism and autoimmune diseases. The classical symptom of pleurisy is cutting or sharp pain in chest while breathing.
  • Pulmonary fibrosis
    It is type of interstitial lung disease characterized by fibrosis formation and development of connective tissue in the lungs. There is scarring of lung tissue that makes lungs stiff leading to shortness of breath. Other symptoms of pulmonary fibrosis are chronic-dry and hacking cough, chest discomfort, generalized weakness and weight loss.
  • Sarcoidosis
    It is a disease characterized by abnormal collection of granulomas (inflammatory cells) that forms a nodule in multiple organs, especially lungs and lymph nodes. Sarcoidosis is associated with interstitial lung disease. In few cases this condition clears up without any medical assistance, but some patients require medical evaluation with long term medications.
  • Pertusis
    It is a contagious infection of bronchi caused due to pathogenic bacteria – Bordetella Pertusis. The classical symptom of Pertusis is persistent whooping cough, which can lead to vomiting and fainting due to constant coughing.
  • Pulmonary embolism
    In this respiratory condition, there is a blockage of the artery that supplies blood to the lung(s) or its branches. A blood clot (emboli) blocks the main artery that travels through the bloodstream from other organs of the body. It is usually seen in the patients suffering from deep vein thrombosis (DVT), a condition that occurs in deep veins of legs. The clinical features of pulmonary embolism are palpitations, pain in chest while breathing, difficulty in respiration, increased heart rate, cyanosis (bluish discoloration of skin), and low oxygen saturation. In severe cases, a person may collapse due to sudden lowering of blood pressure and ultimately death.
  • Pulmonary hypertension
    It is a serious respiratory illness that is characterized by increase blood pressure in lung vasculature i.e. pulmonary artery, pulmonary vein and pulmonary capillaries. The signs and symptoms of pulmonary hypertension are breathlessness, giddiness, fainting and leg swelling, and often associated with heart failure.
  • Lung Cancer
    It is also known as carcinoma of lung(s). It is characterized by uncontrolled growth of malignant cells in the tissue of lung(s). The most common cause of lung cancer is prolonged, excessive smoking. The symptoms of lung cancer are coughing up blood (hemoptysis), chest congestion, breathlessness, fatigue, weight loss, etc. The management of lung cancer is done by chemotherapy, radiotherapy, or surgery.
  • Mesothelioma
    It is a rare form of cancer that develops from mesothelium (protective lining that covers organs) cells. It is usually caused due to continuous exposure to asbestos. It is a kind of occupational disease that affects industrial workers.

Examination of lung(s) plays a vital role in diagnosing various respiratory conditions. It is usually done by various equipments and laboratory tests that determine the functioning of respiratory tract. You physician may advise you to get your lungs test in case of any respiratory complaints such as cough, difficulty in breathing, chest congestion, etc.
Few common examination of lungs

  • Chest X-ray:
    The most common test to assess any lung problems is a plain chest X-ray that is done in different positions such as posterio-anterior view, anterio-posterior view, lateral views, etc. This examination can identify fluid in lung, air or fluid in chest, foreign bodies, pneumonia, tuberculosis, bronchitis and many such respiratory problems.
  • Pulmonary function tests (PFTs):
    It is usually done with the help of Spirometer (mentioned earlier). PFT is to evaluate the working of lungs by measuring the air exhaled and inhaled in a given time. Your pulmonologist will advise you this test for various respiratory diseases.
  • Sputum tests:
    Microscopic evaluation of sputum for abnormal cells helps in diagnosing carcinoma of lung and other lung conditions. Acid-Fast Bacilli (AFB) is a specific sputum test done for TB with the help of early morning sputum or cough. Sputum culture is done to detect the micro-organisms that are responsible for respiratory infection such as bronchitis and pneumonia. Hence, sputum test plays an important role in detecting and assessing various respiratory diseases.
  • Lung biopsy:
    It is usually done for histopathological evaluation that is performed in laboratory set-up. A small piece of affected tissue is taken from the lungs through a bronchoscopy or surgery. This tissue is then examined by a well-qualified pathologist under the microscope that helps in diagnosing lung conditions.
  • CT (Computed Tomography) Scan and Magnetic Resonance Imaging (MRI) Scan:
    Your pulmonologist may advise your CT or MRI scan to assess your lung condition. High-resolution images are taken through radio waves to analyze the structures of respiratory tract.
  • Flexible bronchoscopy:
    A flexible tube with small camera (endoscope) is passed through the mouth or nose into the bronchi (airways). A pulmonology specialist will perform this procedure to assess the internal organs of respiratory system and a sample of affected tissue is taken for biopsy.
  • Rigid bronchoscopy:
    A rigid tube made up of metal is inserted through mouth into the respiratory tract under general anesthesia. It is more effective than flexible bronchoscopy.

Your physician or pulmonologist will suggest you a suitable treatment after considering the type of respiratory disease through physical examination, laboratory tests, scans, etc.

  • Antibiotics:
    Medicines (antibiotics) that kill pathogenic bacteria are used to treat respiratory infections such as acute bronchitis, pneumonia, etc. However, antibiotics are not effective against respiratory infections caused due to viruses. Antibiotics such as Azithromycin, Erythromycin, Doxycycline, Levofloxacin, Ceftriaxone, Cefotaxime, Penicillin, etc. are used in treating respiratory infections.
  • Antiviral drugs:

    Respiratory infections such as influenza caused due to viruses are treated with the help of antiviral drugs.

  • Bronchodilators:
    People suffering from bronchial asthma or COPD are treated by using bronchodilators to reduce their symptoms of shortness of breath and wheezing. Bronchodilators are given in the form of tablets or inhalers to expand the bronchi (airways). Medicines such as Montair, Generic Singulair, Generic Albuterol, etc. are used in treatment of asthma.
  • Corticosteroids:
    Oral or inhaled steroids are used to reduce inflammation in respiratory diseases such as COPD and asthma. It improves the symptoms of COPD and asthma such as cough, breathlessness, etc.
  • Vasodilators:
    Vasodilators are often given through veins to lower the pressure in the lungs. They are usually used in pulmonary hypertension.
  • Surgical interventions:

    • Thoracotomy – To obtain a lung biopsy a surgeon performs a surgery that enters the thorax or chest wall in case of serious respiratory conditions.
    • Lung Transplant – It is the surgical removal of affected lung and replacement with donor’s lung. Serious respiratory diseases such as pulmonary fibrosis, pulmonary hypertension and severe COPD are treated by lung transplant.
    • Lung resection – In case of lung cancer, a diseased portion of the lung is removed through surgical procedure.
    • Thoracostomy – A chest tube is inserted by making an incision in the chest wall to drain the fluid or air around the lung.
    • Pleurocentesis – A sterile needle is placed into the cavity of chest to drain fluid around the lung.
    • Video-assisted thoracoscopic surgery (VATS) – A surgical procedure with the help of endoscope used in various respiratory conditions.
  • Chemotherapy and Radiation Therapy:

    Chemotherapy and Radiation therapy are effective treatments used in carcinoma of lung. In chemotherapy, cytotoxic agents are used to kill the cancer cells. On the other hand, radiation therapy is given by using ionizing radiation to kill malignant cells on a specific targeted organ. There are two types of radiation therapy, internal and external radiation therapy.
  • Mechanical Ventilation:
    A tube is inserted into the mouth or the neck that is attached to a machine called as ventilator with a ventilator pump. It is used in ARDS and other lung diseases.

Few respiratory tract affections such as allergies, asthma, acute respiratory infections and COPD can be treated by using alternative and complementary methods. The treatments range from herbal remedies to breathing exercises. Though, many health care experts are investigating the effectiveness of alternative treatments for respiratory affections. In many asthma cases people got relieved by using alternative therapies under the supervision of health care practitioners.
Few alternatives for asthma

  • Acupuncture – It is an alternative therapy that involves the insertion of thin needles into the skin at specific points on the body. Few studies are not clear how acupuncture works on asthma. However, if you decide to get your asthma relieved from acupuncture, you should do so under a well-qualified, licensed acupuncturist.
  • Herbal remedies – Natural herbal remedies are used by many alternative therapists, as they are been used since thousands of years to treat respiratory disorders. Primarily they are used in treating asthma in many countries. Different types of herbs are used in combinations to get the desired effect, rather than using a single herb. If you are planning to take herbal remedies for your asthma, you should consult your doctor or alternative medicine specialist. You should ask all the benefits and risks involved in taking herbal remedies for asthma and allergies.
    Few herbal remedies such as butterbur, ginkgo extract, French maritime pine-bark extract, dried ivy, choline, tylophora indica, etc. are used in treating asthma. Home remedies such as figs, ginger, mustard oil, coffee, garlic, eucalyptus oil, onions, honey, lemon, salmon, etc. are used in managing asthma and allergies.
    Coltsfoots, Elecampane, Horehound, Lobelia, Mullein, Lungwort, and Sea Buckthorn are few natural lung-healing remedies that help in treating respiratory affections.
  • Breathing exercises – Many health care specialist advice asthma patients to practice breathing techniques. Number of asthmatics practiced breathing exercises and reported improved signs and symptoms. You should consult your doctor to know about the various breathing techniques.
    Breathing exercises that helps in treating asthma are as follows –
    • Take slower breaths
    • Take breaths less often during meditation
    • Breathing through nose rather than mouth
    • During deep breaths (belly breaths) use your abdominal muscles
    • Yoga breathing (pranayama)
    • Buteyko breathing technique

There are other breathing exercises that should be done under the supervision of your doctor. One should follow other healthy lifestyle such as healthy diet, meditation, stress reduction techniques, and quit smoking, etc. to improve general health.

  • Other therapies such as massage and chiropractic treatment, inspiratory muscle training and relaxation therapy are also useful in managing asthma symptoms. One should improve their immunity by consuming diet rich in vitamins and minerals. This will help you fight against respiratory infections.

Hence, you should take care of your respiratory system by implementing few preventive measures, and timely medication in case of respiratory disorders to avoid further complications.

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