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R E S P I R A T O R Y A N A T O M Y A N D P H Y S I O L O G Y N I A M H C L A R K E Let’s start with an SBA… How many lobes does the right lung have? A- 1 B- 4 C- 3 D- 2 E- 5 Let’s orientate ourselves… • The lungs are black on x-ray as they are filled with air • The lungs are located within the thorax • The hilum of the lung is labelled- it is on the medial https://www.lecturio.com/concepts/pulmonary-radiology/ aspect of each lung • It provides an entry and exit point for structures from the mediastinum • Each root contains… • A bronchus • 1 pulmonary artery • 2 pulmonary veins • Pulmonary nerve plexus • Lymphatic vessels Lung anatomy- • Right lung- 3 lobes separated by horizontal and oblique fissure • Left lung- 2 lobes separated by an oblique fissure • The lungs are lined by visceral pleura • The thoracic cavity is lined with parietal pleura • The space between the 2 is the pleural cavity and is a potential space for fluid to accumulate Teach Me Anatomy Blood supply!! • Paired pulmonary arteries leave the right side of the heart and carry deoxygenated blood to each lung • ARTERIES carry blood AWAY from the heart • Blood is oxygenated in the lungs via the alveolar capillary network • Oxygenated blood leaves the lungs via the pulmonary veins which drain into the left atrium Right ventricle-> pulmonary artery-> capillary network at respiratory bronchioles-> oxygenated blood-> pulmonary venules-> pulmonary veins-> left atrium Nervous supply!! Parasympathetic activity-> Ach release-> acts on M3 receptors-> smooth muscle contraction Sympathetic activity-> noradrenaline release-> acts on Beta 2 adrenergic receptors-> smooth muscle relaxation https://link.springer.com/chapter/10.1007/978-981-13-5895-1_16 parasympathetic-and-sympathetic-nervous-systems_fig1_233889549er-by- Let’s see who was listening… The parasympathetic supply to the lung is derived from which nerve? A- Phrenic nerve B- Intercostal nerves T5-7 C- Superior cervical ganglion D- Vagus nerve E- Parasympathetic trunks Histology of the respiratory tract!! • Conducting zone- gas molecules move by bulk flow towards the gas exchange surfaces • Respiratory bronchioles are the first component that take part in gas exchange • Trachea- respiratory epithelium- pseudostratified ciliated columnar epithelium with goblet cells • Ciliated epithelium create muco-ciliary escalator which removes foreign bodies • Bronchus- tall columnar epithelium • Bronchioles- ciliated columnar epithelium https://www.researchgate.net/figure/Airway-generations- adapted-from-ref-1_fig1_280768837 Histology of the respiratory tract!! • Conducting zone- gas molecules move by bulk flow towards the gas exchange surfaces • Respiratory bronchioles are the first component that take part in gas exchange • Respiratory bronchioles- ciliated cuboidal epithelium with clara cells • Alveoli- squamous epithelium. Made up of type 1 and type 2 pneumocytes. Surrounded by capillary network for gas exchange • Type 1- squamous cells with a very thin diffusion barrier • Type 2- secrete surfactant to reduce surface tension and stop alveoli from collapsing https://www.researchgate.net/figure/Airway-generations- adapted-from-ref-1_fig1_280768837Good website to use for histology- https://www.histology.leeds.ac.uk/ Definitions… Compliance- how easily a system can expand. Volume/pressure. If something is not very compliant- requires a much greater pressure to reach a given volume. Elastance- the resistance of a system to expand. Pressure/volume. Due to presence of elastin- creates elastic recoil which allows for passive expiration.Changes in the balance between compliance and elastance occur in lung disease… Compliance of the lungs decreases as elastance increases in… • Pulmonary fibrosis. • Pulmonary hypertension. • Increased surface tension. https://slidetodoc.com/rspt-1060-module-c-applied/physics-lesson-1 Elastance of the lungs decreases as compliance increases in… • Normal ageing. • Emphysema- break down in elastic fibres-> less elastic recoil-> less resistant to expand-> more compliant. Obstructive vs Restrictive lung disease in Spirometry… • RESTRICTIVE- conditions that make it difficult to EXPAND their lungs during INHALATION. • The lungs are restricted from fully expanding- can occur due to stiffening within the chest wall, weakened muscles or damaged nerves. • Lung volume is reduced. • OBSTRUCTIVE- conditions that make it hard to EXHALE. • Due to- fibrosis- laying down of scar tissue. • Muscular diseases. • Amyloidosis. • Airways are obstructed. • Obesity. • Build-up of air in the lungs- large, overinflated lungs. • COPD- mucus build up/ loss of elastic recoil. • Asthma- the airways spasm and temporarily close, preventing air from getting out. • Increase in total lung capacity- less air can be exhaled. • Patients with COPD can appear barrel chested. Spirometry enables us to differentiate between obstructive and restrictive diseases- FEV1/FVC- • FEV1- forced expiratory volume in one second- volume of air expelled in the first second of a forced expiration. • FVC- forced vital capacity- largest amount of air that can be expired following maximum inspiration. • Obstructive- FEV1/FVC ratio less than 70%. FEV1 is reduced, FVC stays the same/ slightly reduces. • FVC can still be reached but it will take the patient longer. • Restrictive- FEV1/FVC ratio remains the same- as the total lung capacity has been reduced. YouTube video explaining it very well- https://www.youtube.com/watch?v=YwcNbVnHNAo SBA- Which of the following conditions is a restrictive lung disease? A- chronic bronchitis B- asthma C- cystic fibrosis D- pulmonary fibrosis E- emphysema Gas Exchange!! V= ventilation- the exchange of air between the atmosphere and the lungs https://twitter.com/pa_maday/status/643509752828399621?lang=ga Q= perfusion- the passage of blood through vessels to the respiratory tissue for gas exhange Gas exchange can occur most efficiently when ventilation and perfusion are equal Diffusion of oxygen and carbon dioxide are driven by their partial pressure gradients Gas Exchange!! When V=Q the V/Q ratio will be 1 ➢ V/Q= 0 if there is perfusion without ventilation. V=0. 0 divided by any number is 0. https://twitter.com/pa_maday/status/643509752828399621?lang=ga ➢ For example- localised inflammation of the airways. ➢ V/Q= infinity if there is ventilation without perfusion. Q=0. Any number can be divided by 0 to give that number= infinity. ➢ For example- pulmonary embolus.https://www.rcontrols-various-components_fig1_345322590ion-a-The-respiratory-center-in-the-brain- The control of breathing… • Breathing is a subconscious activity that arises in the medulla. • Within the medulla- • Dorsal respiratory group- contains inspiratory neurones. • Ventral respiratory group- contains expiratory neurones. • The pons can modify breathing- • Apneustic centre- sends signals for inspiration for long and deep breaths. • Pneumotaxic centre- sends signals to inhibit inspiration- for fine control. PonsMedulla->Spinal Cord->Respiratory Muscles https://www.researchgatfactors_fig1_278667995-of-factors-affecting-the-control-of-breath-hold-duration-Many- Receptor control… • Central chemoreceptors- sensitive to changes in pH due to changes in CO2- CO2 removal is our drive to breathe. • Peripheralchemoreceptors- found in the aortic arch and carotid bodies. Sensitive to a decrease in PaO2= increased firing. • Hering-Breur reflex- Stretch receptors in the visceral pleura in the walls of the bronchi and bronchioles send signals via the vagus nerve to stop inspiration. Respiratory failure… A condition in which the respiratory system fails to maintain its function. A failure in oxygenation +/- carbon dioxide removal. Reference ranges- pH- 7.35 – 7.45. PaO2- 11 – 13kPa. PaCO2- 4.7– 6kPa. SaO2- greater than 94%. HCO3- 22 – 26mEq/l. o Hypoxaemia- lack of oxygen in arterial blood. PaO2 less than 8kPa. Normal is 11-13kPa. o (Hypoxia- lack of oxygen in the tissues) o Hypercapnia- too much carbon dioxide in arterial blood. PaCO2 greater than 6kPa. Normal- 4.7-6kPa. Respiratory failure… Type 1- oxygenation failure. Low PaO2 with a normal or low PaCO2. • There is damage to the lung that disrupts the diffusion of oxygen into the alveoli. • The remaining functioning tissue is need to excrete CO2 as this is out drive to breath. • Carbon dioxide excretion occurs, oxygenation does not. Type 2- ventilatory failure. Low PaO2 and a high PaCO2. • Examples- pulmonary embolus, pneumonia, acute respiratory distress • The whole lung is affected. syndrome. • There is inadequate ventilation and CO2 levels build up. • Examples- neuromuscular disease, drug overdose, chest wall dysfunction, severely restricted airways- eg. in COPD. Interpreting ABG!! • Reference ranges- • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • BE- -2 to +2 mmol/l. • SaO2- 94-98%. • Reference ranges- • pH- 7.35 – 7.45. Assess oxygenation… • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • PaO2 should be 11-13kPa. • HCO3- 22 – 26mEq/l. • In a normal patient breathing room air. • BE- -2 to +2 mmol/l. • If PaO2- patient is hypoxic-> respiratory failure. • SaO2- 94-98%. Assess pH… • pH should be between 7.35 and 7.45. • Below 7.35 indicates acidaemia. • Above 7.45 indicates alkalaemia. • Reference ranges- Is the pH explained by the • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. PaCO2? • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • PaCO2- 4.7-6.0kPa. • BE- -2 to +2 mmol/l. • Carbon dioxide is an ACIDIC gas. • SaO2- 94-98%. • If CO2 high- above 6.0kPa-> acidotic pH. • If CO2 low- below 4.7kPa- alkalotic pH. Therefore… • Low pH and High CO2= respiratory acidosis. • High pH and Low CO2= respiratory alkalosis. • Reference ranges- If not, is the pH explained by the • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. HCO3-? • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • HCO3- 22-26mEq/l. • BE- -2 to +2 mmol/l. • SaO2- 94-98%. • Bicarbonate makes solutions more alkalotic. • Below 22-> acidotic pH. • Above 26- alkalotic pH. Therefore… • Low pH and Low HCO3-= metabolic acidosis. • High pH and High HCO3-= metabolic alkalosis. • Reference ranges- Base Excess… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • Calculate base excess- the amount of acid required to • HCO3- 22 – 26mEq/l. • BE- -2 to +2 mmol/l. return the pH to normal at normal PaCO2. • SaO2- 94-98%. • Indicates what is happening metabolically. • Normal range base excess- -2 to +2. • BE < -2 is a metabolic acidosis. If acidic- negative as won’t want to add more acid. • BE > +2 is a metabolic alkalosis. • Reference ranges- Let’s recap… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • Assess PaO2. • HCO3- 22 – 26mEq/l. • BE- -2 to +2 mmol/l. • Assess pH of the blood. • SaO2- 94-98%. • Assess PaCO2. • If PaCO2 is not the cause of the change in pH= metabolic cause. • Use Base Excess to confirm it is a metabolic cause. • Reference ranges- Example… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • PaO2: 12.2kPa in room air NORMAL • BE- -2 to +2 mmol/l. • pH: 7.28 LOW • SaO2- 94-98%. • PaCO2: 8.1kPa HIGH • HCO3: 24mEq/L NORMAL Diagnosis- Respiratory Acidosis • Reference ranges- When in ROME… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. Respiratory = Opposite • BE- -2 to +2 mmol/l. Acidosis: Low pH + High PaCO2 • SaO2- 94-98%. Alkalosis: High pH + Low PaCO2 Metabolic = Equal Acidosis: Low pH + Low HCO3 Alkalosis: High pH + High HCO3 • Reference ranges- SBA… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. An acutely unwell patient presents to the • HCO3- 22 – 26mEq/l. emergency department and an ABG is performed • BE- -2 to +2 mmol/l. showing the following… • SaO2- 94-98%. PaO2: 28kPa (on 35% supplementary O2) pH: 7.52 PaCO2: 2.0kPa HCO3: 25.7mmol/L BE: 1.7mmol/L What does their ABG show? A- respiratory alkalosis B- metabolic acidosis C- metabolic alkalosis D- respiratory acidosis E- normal results • Reference ranges- Compensation… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • The body will attempt to compensate for a pH • HCO3- 22 – 26mEq/l. abnormality. • BE- -2 to +2 mmol/l. • Respiratory compensation occurs FASTER than • SaO2- 94-98%. metabolic compensation. • If the pH is normal but the PaCO2 or HCO3- look abnormal- full compensation. • If the pH is slightly abnormal but the PaCO2 or HCO3- does not fit the pattern- partial compensation. • Reference ranges- Compensation… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. Example 1- • HCO3- 22 – 26mEq/l. • pH: 7.35 NORMAL • BE- -2 to +2 mmol/l. • SaO2- 94-98%. • PaCO2: 4.0 LOW • HCO3: 15 LOW Explanation- • pH is on the LOW side. • CO2 is LOW- the body is trying to blow off CO2 to remove acid. • Bicarbonate is LOW- metabolic acidosis. Diagnosis- • Acute metabolic acidosis with respiratory compensation. • Reference ranges- Compensation… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. Example 2- • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • pH: 7.35 NORMAL • BE- -2 to +2 mmol/l. • SaO2- 94-98%. • PaCO2: 8.0 HIGH • HCO3: 32 HIGH Explanation- • pH is on the LOW side. • PaCO2 is HIGH. • HCO3- is HIGH. Diagnosis- • Chronic respiratory acidosis with metabolic compensation. • Reference ranges- SBA… • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. An ABG is performed. The results are as follows- is acutely unwe• PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • BE- -2 to +2 mmol/l. PaO2: 9.2kPa • SaO2- 94-98%. pH: 7.48 PaCO2: 8.4kPa HCO3: 38mmol/L BE: 13.8mmol/L What does their ABG show? A- metabolic alkalosis B- metabolic alkalosis with full respiratory compensation C- respiratory alkalosis D- metabolic acidosis E- metabolic alkalosis with partial respiratory compensation • Reference ranges- Anion Gap … • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaCO2- 4.7– 6kPa. • HCO3- 22 – 26mEq/l. • BE- -2 to +2 mmol/l. • SaO2- 94-98%. • Useful in trying to work out the cause in patients with metabolic acidosis. • In patients with metabolic acidosis and a high anion gap may have DKA or lactic acidosis. • In patients with metabolic acidosis and a normal anion gap it may be due to diarrhoea. • You will be able to work this out from the patient’s history too!! • Reference ranges- SBA … • pH- 7.35 – 7.45. • PaO2- 11 – 13kPa. • PaO2: 13.2kPa • PaCO2- 4.7– 6kPa. • pH: 7.3 • HCO3- 22 – 26mEq/l. • PaCO2: 4.1kPa • BE- -2 to +2 mmol/l. • HCO3: 18 • SaO2- 94-98%. • Na+: 134 • K+: 4.2 • Cl-: 102 Calculate the anion gap in this patient… A- 36.2 B- 14.0 C- 116.0 D- 18.2 E- 36.4