Y khoa, y dược - Chapter 3: The respiratory system

Chapter 3 The Respiratory SystemRespiratory Disease In the UK respiratory diseases are responsible for more emergency hospital admissions than diseases of any other origin. Many respiratory conditions are easy to assess and treat and despite a continual reduction in mortality rates over recent years. One of the most prevalent diseases affecting the respiratory system is chronic obstructive pulmonary disease (COPD) - affecting 900,000 individuals within the UK and accounting for in excess of 30,000 deaths per year.The Respiratory System The initial structures of the respiratory system are the mouth, or oropharynx, and the nose.The nose is lined with special types of tissue cells and hair to filter and moisten air and is the primary route for the conveyance of air.The mouth can also relay air into the upper airway passages leading to the lungs. The Respiratory SystemThe Passageway A continuous link exists between the air entry points and the beginning of the lungs. The 12.5cm passageway that forms the pharynx leads from the back of the mouth and nose, dividing into the oesophagus at the rear of the throat, and the larynx at the front. At the rear of the pharynx, at the base of the nose, sits the adenoids and the palatine tonsils at the junction of the mouth and throat, they combine to filter invading bacteria. The Larynx The larynx begins at the back of the mouth leading down the neck towards the trachea The larynx and trachea are composed of rings of cartilage attached by membranes and ligaments. The thyroid cartilage surrounding the larynx forms the Adams’s apple. The Trachea is around 10cms long with incomplete hyaline cartilage rings running its outside length. The trachea is lined with a rich supply of mucus secreting goblet cells. The LungsThe bronchi are where the single passageway splits in two, one leading to the right lung and one leading to the left. The inside of the bronchi are lined with ciliated epithelium. These increasingly fine tubes are composed of elastic, fibrous and muscular tissue. The lungs lay either side of the heart; the left lung consists of two lobes (superior and inferior), the right lung has an additional lobe (the middle lobe). Lung tissue is the combination of bronchioles, blood vessels, elastic and connective tissue, nerves and alveoli. A double-layered membrane, named the pleura, individually surrounds the lungs. The Muscles of Respiration Muscles that enable the act of respiration are as essential as the organs or structures that enable the passage of air to the alveoli. The main muscle of respiration is the diaphragm, a large muscular sheet that separates the chest cavity from the abdominal contents.Lying beneath the lungs, the diaphragm resembles a dome and stretches across the base of the chest, attaching at various points to bone for stabilisation. The sternocleidomastoid and intercostal muscles all assist in respiration. The Act of Respiration A constant process that does not require conscious effort as it is driven by both voluntary and involuntary control mechanisms. In combination with the muscles of respiration, air is drawn in by active contraction of the thorax, during inhalation the diaphragm contracts downward and away from the lungs, creating more space in the chest cavity. This lowers the air pressure in the chest cavity relative to the pressure outside the body, subsequently air moves into the lungs.Transportation of Oxygen and Carbon Dioxide within the Blood Oxygen TransportMost of the O2 is transported in combination with haemoglobin to form oxyhaemoglobin. When the body is active the tissues produce excessive CO2 and heat oxygen is released from its bound state with the haemoglobin. This intrinsic prioritisation process allows cells with the greatest need to receive O2 first.Carbon Dioxide TransportThis waste product of metabolism is mainly carried as bicarbonate ions in the plasma (70%). In addition around 7% is carried in a dissolved state within the blood plasma and the remaining 23% loosely combined with haemoglobin as carbaminohaemoglobin (Waugh & Grant 2007). Central Control of Respiration The act of respiration is predominately under involuntary control otherwise when asleep an individual would lose the governing stimulus to breath. The rate and depth of inspiration are under the control of the respiratory centre situated within the medulla oblongata within the brain stem. Airway Assessment & Intervention (Management) Without an adequate constant and ‘clean’ supply of oxygen an individual will soon demonstrate the clinical signs of hypoxia. If a patient has an obstructed airway, or fails to maintain airway patency, oxygen will not reach the lungs leading to asphyxia. Within the lungs it is also essential that a constant supply of blood reaches the alveoli. This balance between circulating oxygen levels and the presence of sufficient blood is referred to as the perfusion/ventilation ratio. Airway CompromiseCan occur at any level between the nose/mouth down to the bronchi. In the unconscious patient the most common cause of airway obstruction is by the posterior displacement of the tongue at the level of the pharynx (RCUK, 2006). Vomit, blood, and foreign bodies commonly obstruct airflow at the site of the soft palate and epiglottis resulting in aspiration of particles into the lungs. Obstruction can also occur at the larynx, resulting from the inflammation associated with burns and anaphylaxis. Obstruction below the larynx is also possible, but less common.Airway Assessment The initial assessment can be achieved by applying the look, listen, feel approach; Look for chest and abdominal movementsListen and feel for airflow at the mouth and nose To assess effectively put the side of your face, and ear, above the patient’s nose and mouth, with your eyes facing the patient’s feet for up to 10 seconds, this allows for rapid assessment of all three descriptors in one action. Recognising Airway CompromiseMake a list identifying the signs and symptoms an individual may make demonstrate if their airway is becoming compromised.An example being:Inspiratory stridor - Obstruction at laryngeal level or above Making a DifferenceIf you identify possible airway obstruction immediate action must be taken. There are three basic manoeuvres that can be used to relieve upper airway obstruction; head tilt, chin lift and jaw thrust. These simple re-positional methods of expanding the airway are frequently successful when the cause of the obstruction is a loss of muscle tone within the pharynx. NB following any manoeuvre the patient’s ability to ventilate must be reassessed again by reapplying the look, listen and feel approach. Basic Airway Adjuncts The oropharyngeal/Guedel airway is inserted into the mouth behind the tongueThe nasopharyngeal airway can be utilised in conscious patients, as it is not associated with initiating the gag reflex or vomiting. Oxygen Delivery DevicesIdentify what types of oxygen delivery devices are available within clinical areas.Would the administration of oxygen help a patient who is unable to ventilate?What action would this patient require?Asthma Asthma can be defined as a chronic condition with acute exacerbations resulting in a hypersensitivity reaction. Asthma is the result of a combination of complex interactions, including the hypersecretion of mucus, constriction of smooth muscle within the bronchioles, and localised inflammation.The Global Initiative for Asthma (GINA, 2004) estimate that 300 million people, of all ages and races experience asthma, the annual incidence is increasing in all age groups. PathophysiologyThe pathophysiology or pathogenesis of asthma can be seen as a multidimensional phenomenon in which a series of internal reactions combine or accumulate to produce increasing inflammation and hyper responsiveness of the airways. Resulting in varying levels of bronchoconstriction via smooth muscle contraction, mucus production and increased vascular permeability. Bronchial Hypertrophy & Excessive Mucus Production Chronic Obstructive Pulmonary DiseaseCOPD can be defined as a chronic and debilitating disease continuum in which localised irritation of the bronchioles and lungs results in increasing airflow obstruction which is usually progressive. COPD is a collective term for three separate disease processes;chronic bronchitisEmphysemachronic asthma. Approx 900,000 individuals are diagnosed with COPD in the UK alone and accounts for around 30,000 deaths each year (NICE, 2004). Signs & SymptomsSymptoms are insidious and usually begin to appear in the mid thirties proliferating with increasing age. The early warning signs or symptoms are the excessive production of phlegm and a chronic or persistent cough generally lasting in excess of three months. The diagnosis of COPD should be considered in all patients over 35 who have a chronic history of smoking, and who present with external breathlessness, a chronic cough, and regular sputum production (NICE, 2004). The formal diagnosis of COPD is confirmed by spirometry. Spirometry plays a pivotal role in the identification and modern management of COPD. Treatment Plan As with all serious presentations high-flow oxygen should be administered, regardless of whether the patient may have a history of COPD. The application of high flow supplementary oxygen is essential until proven otherwise (RCUK, 2006).The patient should be assisted to sit upright to reduce the work of breathing.The effectiveness of treatments should be closely monitored and evaluated; this will involve continually monitoring the patient’s oxygen saturation level via a pulse oximeter, counting their respiratory rate and assessing their level of consciousness. MedicationThe initial management of exacerbations of COPD centre on the use of nebulised bronchodilatorsantibiotics if infective causesteroids Maintenance of the patient’s oxygen saturation above 90% is essentialIf the patient fails to respond there will be a need for more aggressive therapy such a non-invasive ventilation therapy or intubationConclusionThere are many conditions affecting the respiratory system and therefore potentially compromising the ability to breathe.The quick assessment and use of basic interventions can prove life-saving.Familiarise yourself with these basic techniques and the devices available within your clinical areas.