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Table of Contents
Artificial Respiration: current concepts, particularly during Covid-19 infection
Topic 5 - Team M - Franziska Tittel, Afra Salman, Fanshuang Meng, Ehsan Amini
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Upper Respiratory Tract
The nose consists of three parts: external nose, nasal cavity and sinuses.( Dion MC, Jafek BW, Tobin CE. The Anatomy of the Nose: External Support. Arch Otolaryngol. 1978;104(3):145–150. doi:10.1001/archotol.1978.00790030031007) It is the beginning of respiratory tract. The nasal cavity has the effects of warming, moistening, and cleaning the air.
nose is the first organ of respiratory system. Its function is to warm and moister the inhaled air. Moreover, nose can also filter particles in the air. Nose is also a part of olfactory system. It contains an area responsible for sense of smell.( Stanisław Betlejewski, Andrzej Betlejewski, Wpływ aerodynamiki przepływu powietrza przez nos na fizjologię nosa, Otolaryngologia Polska, Volume 62, Issue 3, 2008, Pages 321-325, https://doi.org/10.1016/S0030-6657(08)70263-4.)
Throat contains pharynx and larynx. 1. pharynx The pharynxis a muscular tube. It consists of nasopharynx, oropharynx and laryngopharynx. The nasopharynx communicates with the nasal cavity and oral cavity, and the laryngopharynx communicates with the larynx and trachea. The pharynx is a common channel for food and gas.( Donner, M.W., Bosnia, J.F. & Robertson, D.L. Anatomy and physiology of the pharynx. Gastrointest Radiol 10, 197–212 (1985). https://doi.org/10.1007/BF01893103) 2. larynx The larynx is both a respiratory organ and a pronunciation organ. The larynx is based on cartilage and is connected by joints, ligaments and muscles. The larynx is located in the middle of the front of the neck. The upper boundary of the adult larynx is between the fourth and fifth cervical vertebral bodies, and the lower boundary is near the lower edge of the sixth cervical vertebral body.( Niv Mor, Andrew Blitzer, Functional Anatomy and Oncologic Barriers of the Larynx, Otolaryngologic Clinics of North America, Volume 48, Issue 4, 2015, Pages 533-545. doi.org/10.1016/j.otc.2015.04.002.)
The pharynx is a channel of food and air, and a resonance cavity for pronunciation (Donner, M.W., Bosnia, J.F. & Robertson, D.L. Anatomy and physiology of the pharynx. Gastrointest Radiol 10, 197–212 (1985). https://doi.org/10.1007/BF01893103) The larynx is used to generate sound. It can control pitch and volum. Moreover, the larynx can prevent foreign material from entering the lung. (DOI:https://doi.org/10.1016/S0002-9343(97)00314-8)
Lower Respiratory Tract
Lower respiratory tract consists of trachea and bronchus(including bronchioles) and alveoli(book: https://reference.medscape.com/article/1898852-overview#a1).
The trachea is composed of dozens of “C” shaped cartilage rings and smooth muscles in between. The cartilage keeps the trachea open and keeps ventilation. (Beate E.M. Brand-Saberi, Thorsten Schäfer, Trachea: Anatomy and Physiology, Thoracic Surgery Clinics, Volume 24, Issue 1, 2014, Pages 1-5. doi.org/10.1016/j.thorsurg.2013.09.004. )Smooth muscle can change the diameter of the trachea, which is conducive to the expansion of the esophagus behind it and facilitates the downward movement of food.
The trachea is used to connect the larynx and the bronchus, and has the functions of defense, removal of foreign objects, and adjustment of air temperature and humidity. The inner surface of the trachea and bronchus have cilia, which can filter bacteria. Mucous secretions contain immunoglobulins, which can inhibit bacteria and resist viruses
Bronchial Tubes (Meng)
Bronchus is divided into two parts: left principal bronchus and right principal bronchus. They are connected with left lung and right lung. The left principal bronchus is thin and long, with an average length of 4 to 5cm. The right principal bronchus is short and thick, with an average length of 2 to 3cm.( Otoch JP, Minamoto H, Perini M, Carneiro FO, de Almeida Artifon EL. Is there a correlation between right bronchus length and diameter with age? J Thorac Dis. 2013 Jun;5(3):306-9. doi: 10.3978/j.issn.2072-1439.2013.03.12. PMID: 23825764; PMCID: PMC3698291.)
A person has two lungs: the left lung and the right lung.( Tomashefski, J. F.; Cagle, P. T.; Farver, C. F. & Fraire, A. E. (Eds.) Anatomy and Histology of the Lung, Dail and Hammar's Pulmonary Pathology: Volume I: Nonneoplastic Lung Disease, Springer New York, 2008, 20-48) They are located in the chest cavity of the human body, on the left and right sides of the heart, and are protected by the rib cage. An area called the mediastinum separates the left and right lungs. Below the lungs is the diaphragm. The left and right lungs are divided into several lung lobes, of which the right lung has three lung lobes (upper lobe, middle lobe and lower lobe), and the left lung has only two lung lobe (upper lobe and lower lobe). Each lung lobe is composed of millions or more small air sacs. These small air cells are called alveoli. The alveoli are connected by extremely small tubes–small bronchi. Small bronchi gather together to form bronchi.
For respiratory system, the main function of the lungs is to transport oxygen from the air to the blood and expel carbon dioxide from the blood to the atmosphere. The gas exchange process is completed by the alveoli.
Genetic Information by DNA and RNA
Introduction to Genetics
Genetics deals with the study of genes, variation, and heredity in all organisms. It was first studied in 19th century by Gregor Mendel.
A gene is the basic physical and functional unit of heredity present inside the chromosomes in nucleus of a cell. It is a set of instruction that determines the traits and characteristics of an organism. It is made up of a substance called deoxyribonucleic acid (DNA). Some genes work as instructions for protein synthesis whereas others do not. The size of genes vary from a few hundred to a few million DNA bases. There are 20,000 to 25,000 genes in a person, according to the estimation of human genome project. There are two copies of a gene in every person has two copies of each gene, each inherited from a parent. Where most genes are common in every person, a few vary, and the variant forms of genes is called an allele. Alleles determine the unique features in each person.
Structure & Function of DNA:
DNA molecule is made up of two chains of polynucleotide that are coiled around each other to form a double helix shape. The Polynucleotide chains consist of a phosphate group, a sugar group, and a nitrogenous base. There are four types of nitrogen bases named Adenine (A), Thymine (T), Guanine (G) and Cytosine (C). The order in which they are attached to the gene determines the instructions by DNA or the genetic code. The function of DNA is to store information that is required for an organism to develop, reproduce and function. Information that is transferred from parent cell to daughter cell is known as vertical gene transfer and is occurred through DNA replication. DNA replication is the most important part of bio-inheritance and occurs in four steps.
- Double helix structure is unzipped with the help of an enzyme called helicase
- Primer, that is a short piece of DNA is bound to the leading strand and acts as the starting point for DNA replication
- New strand is formed through elongation process
- Primers are terminated from the original band and replaced by suitable bases
Structure & Function of RNA:
RNA or ribonucleic acid is a ribose nucleotide based complex molecule that helps in protein synthesis. It is a single stranded biopolymer structure with nitrogenous bases attached to the ribose sugar by phosphodiester bond. Nitrogen bases of RNA differ from DNA in that thymine is replaced by uracil. RNA is found to be the genetic material of some viruses. Three types of RNA are commonly known
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
These RNA types are directly involved in the synthesis of proteins through the process of translation. Message from DNA is carried out by mRNA. For the synthesis of the required protein, mRNA is formed through transcription process. For the synthesis of a certain protein by the cell, the gene for this protein is and the mRNA is synthesized through the process of transcription (see RNA Transcription). It then interacts with ribosomes for the synthesis of protein through translation.
Physiology of Gas Conduction and Exchange
Pathegenesis of Infects
Even after the isolation of pathogenic bacteria that caused diseases such as cholera, tuberculosis, and tetanus etc., infectious diseases such as small pox, flu, measles, and mumps etc. remained resistant to any kind of treatment. The microbes that caused these diseases were so small that they passed through filters that restricted bacteria to enter, and hence were called ‘filterable agents’. In 1989 Martinus Beijerinck showed that these agents grew in dividing cells and regained their full strength every time they infected the tobacco plant. He then concluded that these agents might be a living microbes, and was the first to coin the name virus, from the Latin meaning a poison, venom, or slimy fluids.
A virus is a small parasite that cannot duplicate or grow without a host. However, when it affects a susceptible cell, it controls the cell mechanism to produce more viruses.
Morphology and Classification
Viruses do not have a cell structure and therefore are classified as non-cellular particles. They have either DNA or RNA as their genetic material which can be double stranded or single stranded. The genetic material of the particle is surrounded by a protective protein coat. The entire structure of the virus is called varion and the outer layer is called capsid. Different shapes and sizes of capsids determine the virus family they belong to. Caspids are made up of subunits of proteins which are called caspomeres. Their arrangement around the genetic material determines the shape of the virus. For example, adenovirus has a polyhedral shape, and tobacco mosaic virus is long and thin like a rod. Some viruses have an outer membrane surrounding the capsid called an envelope which comprises of mostly phospholipid bilayer but also has one or two types of virus-encoded glycoproteins, like influenza virus.
Classification factors of the viruses include the DNA/RNA center, capsid structure, outer envelope, and the way mRNA is produced. Most common current method for classification is the Baltimore classification scheme, which describes how (mRNA) is generated in every specific virus. Both scanning and transmission electron microscopes can be used to study the surface and internal structures of varions.
The word pathogenesis refers to the bio-mechanism that is involved in the development of a disease. It occurs when an infectious pathogen interacts with the immune system. It also describes where the disease originated from, the events that lead to the disease and if the disease is chronic, acute, or recurrent.
Pathogenesis of Virus:
Pathogenesis of a virus or viral pathogenesis gives the details about how a virus causes disease in a host. Transmission of the virus, its multiplication and spreading in the host are factors describe the complex interaction between the virus and the host.
Stages of pathogenesis include:
- Entrance or implantation of virus in the host
- Its replication in the host
- Its spread to the target disease site in the host
- Its spread to the sites from where it can be transmitted into the environment such as nose and mouth
- Host’s response to the virus
- Virulence, which is the virus’s ability damage to the target cells of the host
- Acting against the immune response of the host
- Effects on the organisms that include either being eliminated from the host, developing persistent infection
- Causing death of the host cell which is called apoptosis or necrosis.
- Killing the host.
Protection (general hygiene, masks, isolation) (Ehsan)
The new coronavirus disease, Covid-19, was declared to be a public health emergency of international concern by the World Health Organization (WHO) in January 2020.
As this virus progresses around the world, there has been a question for people whether it is vital to use face masks. Yet, WHO has not suggested the mass use of masks for healthy individuals to prevent the infection. People tend to wear masks to protect themselves from the infection. However, the point is to wear masks not only to protect ourselves but also to avoid the act of spreading this virus by sneezing or cough.
Here are some hygiene notes to reduce the chances of being infected:
1. Washing the hands regularly during the day and at least for 20 seconds each time can help effectively to kill this virus. If the soap and water would not be available, alcohol-based hand rub is a good alternative.
2. As mentioned above, sneezing and cough can spread the virus easily since the droplets carry the virus. Consequently keeping the distance to people for at least 3 meters is necessary. Furthermore, avoid going to a crowded place.
3. Virus can enter our bodies from eyes, nose and mouth. In addition, hands touch many surfaces during the day and may carry the virus. So avoid touching your eyes, nose and mouth.
4. Using the face masks can not help us not be infected by the virus but it is a respiratory hygiene and can help to restrain the virus to spread. So society should wear face masks more importantly in public areas including supermarkets, Banks, etc.
5. Symptoms of the Covid-19 are as follows: • fever • dried cough • tiredness • difficulty breathing • chess pain or pressure If you face the first three symptoms above stay at home and self-isolated yourself until you recover. But if you face the other symptoms you should apply for medical services immediately.
Insufflation has been used in many medical kinds which will be described shortly. Insufflation is the act of blowing gas into the body. 1. Surgeries: The gas that is used should have some important features. Firstly, it should well dissolve in blood and secondly it must be non-flammable and colorless. Consequently the most common gas that is used is Carbon dioxide. Gases usually are insufflated to body cavity. In the image bellow we can see that it is used in the Laparoscopy surgery.
2.Diagnostics: Here the gasses could help us to improve the quality of Imaging or to gain access to the areas (e.g. in the colonoscopy). 3.Respiratory assistance: To assist patients to breathe better, the gas will be in insufflated into the nose by nasal cannulae. In order to oxygen therapy and a “supplemental” act a nasal cannula used without rigid control of respiration. Most cannulae can only provide oxygen at low flow rates—up to 5 litres per minute (L/min)—delivering an oxygen concentration of 28–44%. Rates above 5 L/min can result in discomfort to the patient, drying of the nasal passages, and possibly nose bleeds (epistaxis).
4. Anesthesia and critical care: In order to assist or maintain general anesthesia insufflated gases and vapors are used to ventilate and oxygenate patients.