CHI335 - Respiratory System - Lecture I.pdf

CHI335 Diagnosis I Respiratory System Lecture I  Describe the components of the respiratory system and their functions  Compare internal and external respiration  Describe the factors that influence breathing  Explain how gases are exchanged in the lungs and tissues, how ox...

CHI335 Diagnosis I Respiratory System Lecture I  Describe the components of the respiratory system and their functions  Compare internal and external respiration  Describe the factors that influence breathing  Explain how gases are exchanged in the lungs and tissues, how oxygen & carbon dioxide are transported  Outline respiratory diseases common signs & symptoms  Outline some relevant diagnostic tests for the system  Identify some common respiratory conditions on X-ray  Describe air volumes, lung capacities, and spirometry findings in obstructive and restrictive lung diseases  Describe the ventilation/perfusion ratio and the common causes for its mismatch  Moving oxygen and carbon dioxide into and out of the body; this is called breathing, respiration, or ventilation  External respiration  Gas exchange between the alveoli and the lungs’ capillaries  Internal/Cellular respiration  Exchange of gases in the tissues  Alveolar cells  Type I – alveolar wall → Gas exchange  Type II – surfactant secreting cells → Reduce surface tension  Macrophages  The respiratory control centre in the brainstem regulates breathing rate, rhythm, and depth by assessing PaO2 & PaCO2 via multiple receptors  Receptors in brain and blood vessels (aorta & carotid arteries) → detect PaO2  Receptors in the lungs (airways & alveoli) → detect irritants and fluid  Receptors in muscles and joints → detect physiological demand for oxygen https://bit.ly/2HA6Ef7  Serosa membrane that surrounds the lungs  The outer membrane is known as the parietal pleura, and the innermost membrane is the visceral pleura  Produces a slippery, serous fluid called pleural fluid  Helps decrease friction as the membranes move against each other during breathing 1. Nerve impulses travel on phrenic nerves to muscle fibres in the diaphragm, contracting them 2. As the dome-shaped diaphragm moves downward, the thoracic cavity expands 3. The intra-alveolar pressure decreases 4. Atmospheric pressure, greater on the outside, forces air into the respiratory tract through the air passages 5. The lungs fill with air  The external intercostal muscles, SCM, and scalenes also contract, raising the ribs and expanding the thoracic cavity further 1. The diaphragm (and external intercostal muscles) relax 2. Elastic tissues of the lungs and thoracic cage, stretched during inspiration, suddenly recoil, and surface tension collapses alveolar walls 3. Tissues recoiling around the lungs increase the intra- alveolar pressure 4. Air is squeezed out of the lungs  External respiration  Exchange of the gases in the lungs  Gases move back and forth between the capillaries and the alveoli  Follows the rule of simple diffusion  Concentration of O2 is greater in the lungs than in the blood  O2 moves towards blood  Concentration of CO2 is greater in the blood than in the lungs  CO2 moves towards alveoli  Intact airways  Enough PO2  Intact alveolar structure  Normal Diffusion distance Oxygen  Almost %99 binds to the haemoglobin in red blood cells  Haemoglobin bound to oxygen is called oxyhemoglobin and is a bright red colour  Approximately %1 stay dissolved in plasma Carbon dioxide  %70 travels as the bicarbonate ion (HCO3-)  %20 is transported bound to haemoglobin  This haemoglobin is called carbaminohemoglobin  %10 travels free or dissolved in the plasma  Internal Respiration  Exchange of gases in the tissues  Gases move back and forth between tissues and capillaries  It also follows the rule of simple diffusion  Concentration of O2 is greater in capillaries than in the tissues  O2 moves to tissues  Concentration of CO2 is greater in the tissues than in the blood  CO2 moves towards the blood  Carbon dioxide level rises   Rate and depth of respiration  pH drops   Rate and depth of respiration  Fear and pain   Breathing rate (generally shallow breaths)  Hyperventilation (i.e. Breathing rapidly and deeply)   Amount of carbon dioxide in the blood →  Rate & depth  “Inflation reflex” (receptors in pleural membranes are activated when the lungs are stretched)   Depth of breathing to prevent over-inflation of the lungs  Examination: Signs & Symptoms  Eupnoea: normal breathing rate  12 – 20 Breath per minute for adults  Tachypnoea: fast breathing  A critical risk factor for deterioration  Bradypnoea: slow breathing  Can also be a sign of impending crisis, especially in the context of narcotic overdose or traumatic brain injury  Apnoea: a total absence of any effective respiratory rate for greater than 20 seconds  Central or obstructive, or a mixture of both  Cough is a common presenting respiratory symptom  It is a reflex explosive expiration when deep inspiration is followed by explosive expiration  Coughing enables the airways to be cleared of secretions and foreign bodies  Acute cough is generally < 3 weeks  ACUTE  Inhaled foreign body  Respiratory tract infection  CHRONIC  PRODUCTIVE  COPD (mucoid mainly)  Pneumonia (purulent)  Pulmonary oedema (pink, frothy)  Lung cancer (bloodstained)  Pulmonary embolism (bloodstained)  TB (bloodstained, common where TB is endemic)  NON-PRODUCTIVE  Asthma  Gastro-oesophageal reflux  Sarcoidosis  Drugs (ACE inhibitors) Not examinable The uncomfortable awareness of breathing  SUDDEN (SECONDS TO MINUTES)  Pneumothorax  Aspiration  Anxiety  Pulmonary oedema  Pulmonary embolism (massive)  Anaphylaxis  ACUTE (HOURS TO DAYS)  Asthma  Respiratory tract infection  Pleural effusion  Metabolic acidosis  CHRONIC (MONTHS TO YEARS)  Chronic airflow limitation (COPD)  Anaemia  Arrhythmia  Valvular heart disease  Cardiac failure  Cystic fibrosis  Idiopathic pulmonary fibrosis  Chest wall deformities  Lung tumours  Pulmonary hypertension  Neuromuscular disorders  CENTRAL CYANOSIS  DECREASED OXYGEN SATURATION  Severe respiratory disease  Pulmonary oedema  Pulmonary embolism  Peripheral cyanosis generally accompanies central cyanosis  Bronchial carcinoma  Chronic suppurative lung disease  Bronchiectasis  Lung abscess  Empyema  Cystic fibrosis  Interstitial lung disease (fibrosing alveolitis, pulmonary fibrosis)  Pleurisy  Pneumonia  Pneumothorax  Pulmonary embolism Coughing up blood can be a sinister sign of lung disease and must always be investigated. It must be distinguished from Haematemesis (vomiting blood – upper GI bleeding) and from nasopharyngeal bleeding  Bronchial carcinoma  Pneumonia  Chronic bronchitis  Bronchiectasis  TB  Pulmonary embolism (infarction)  Pulmonary hypertension (due to mitral stenosis)  Wheezes  Due to vibrations in the bronchial tree when narrowed or obstructed  A continuous, whistling, high-pitched expiratory sound  A very Common finding in asthma and COPD  Foreign body aspiration, laryngeal spasm or irritation, bronchial CA, allergic reactions and bronchitis must be ruled out as DDx  Crackles (Rales)  A brief crackling, discontinuous sounds  Produced by the opening of previously closed bronchioles  Fluid in the small airways or atelectasis  Early inspiratory crackles are associated with diffuse airflow limitation  Late inspiratory crackles are characteristically heard in pulmonary oedema, lung fibrosis and bronchiectasis  Fine crackles are short high-pitched sounds  Coarse crackles are longer-lasting, low-pitched sounds  Think of Congestive heart failure and pulmonary oedema  Rhonchi  Low-pitched, continuous sounds similar to wheeze (expiratory)  Caused by blockage of the main (big) airways by mucous, lesions, or foreign bodies  Coughing can sometimes clear this sound  Stridor  An inspiratory, high-pitched, musical sound heard over the upper airways  It usually indicates a foreign body obstruction of the larger airways (trachea or main bronchi) and requires immediate attention  In children, it is important to differentiate between croup and a foreign body airway obstruction Investigations  This can occur due to insufficient ventilation or perfusion  Alveolar ventilation is affected by  Bronchoconstriction and Atelectasis (alveolar collapse)  Pulmonary oedema  Pneumonia  Alveolar perfusion is affected by  Any condition causing  blood flow to the pulmonary capillaries  Pulmonary artery vasospasm or vasoconstriction (due to hypoxia)  Pulmonary embolism http://www.stritch.luc.edu/lumen/MedEd/Radio/curriculum/Medicine/NM_vq.htm Not examinable  CT scan  MRI  PET scan  Bronchoscopy  US