Where do the lungs sit? Lungs: Mid-clavicular line: 6 th rib, Mid axillary line: 8 th rib and Scapular line 10 th rib Tip: For pleural location, add 2 to each of the above!
LOGO Describe the respiratory system Divide it neatly into two parts: –Upper respiratory tract (what parts does this involve?) has a rich blood supply and its epithelium is covered by a mucus secretion.. It’s function it to warm, moisten and filter so the air is suitable for gases exchange. –Lower RT (what parts?) Two main bronchi divide into smaller airways until the end respiratory portion is reached distally.
LOGO An overview of the Respiratory tree ContractileAre lined by? TracheaResp. Epithelium Bronchi 1,2 and 3 (B- receptors here!) ✔ Resp. Epithelium Bronchiole ✔ Simple ciliated cuboidal + clara cells Respiratory Bronchiole ✔ Simple ciliated cuboidal + clara cells Alveolar Duct ✔ Flat non-ciliated epithelium, no glands AlveolusPneumocytes 1 and 2 Question: What three layers must the gas diffuse across to reach the red blood cell at the Alveolus? Answer:The type 1 pneumocyte, the basement membrane and the endothelium
LOGO Bohr and Haldane effects This is a good mnemonic for remembering what causes the Haemoglobin to disassociate with O2: CADET face right, and release! Question: what do the letters in CADET stand for? Answer: CO2, Acid, 2,3-DPG, Exercise and Temperature
LOGO What three key steps are involved in gas exchange? Ventilation (The amount of air reaching the respiratory portion = V) Perfusion (The amount of blood reaching the respiratory potion = Q) Diffusion (The process of gas transport across the separating barrier) V/Q = 0 V/Q = 1 V/Q = infinity Total block in the airway/alveolar Ventilation/perfusion are matched, ideal! Lung unit is ventilated, but not perfused (apex) Can we help the patient with oxygen therapy? Question: What do the following V/Q ratio mean? What is the V/Q ratio in a normal, healthy lung?
LOGO Compliance Compliance is the change in alveoli volume you get for a change in pressure (C=V/P) –It goes down in lung fibrosis (More effort needed to inflate the lungs) –Up in emphysema (Lungs inflate easily, but with a loss of surface area) –Surfactant prevents alveolar collapse because it lowers surface tension. This increases lung compliance. Question: Why might a runner or patient with COPD purse their lips to Increase the resistance to breathing out?
LOGO Sensory control of breathing Describe the chemical feedback mechanism we use in breathing? 1.Chemoreceptors are located on the brainstem (80% of drive – vital!) medulla region which respond to Hydrogen Ions (although it is CO2 which crosses the BBB, this increases the number of H+ ions) 2.Peripheral chemoreceptors are located in the carotid sinus and aortic arch – these respond to PaO2, PaCO2, pH, Blood flow, Temperature Tip- Don’t confuse these with Baroreceptors, also located in the Carotid Sinus and Aortic Arch!
LOGO MCQs Which of the following is not true? –L–Lung expansion is greatest inferiorly –P–Presence of hysteresis demonstrates lung compliance –P–Pulmonary fibrosis and emphysema both result in low lung compliance –T–The main function of surfactant is to reduce surface tension
LOGO Regarding the dorsal respiratory group, which would increase inspiratory rate? –L–Low O 2 at the central chemoreceptors –S–Stretching of airways (Hering-Brewer reflex) –M–Metabolic acidosis –I–Increased breathing intensity (from ventral respiratory group)
Case 1 Santa Claus visits his local GP complaining of shortness of breath. On questioning he reveals that he has had a productive cough for at least 4 months every year since forever. What microscopic changes are seen in chronic bronchitis? (2) –Hypersecretion of mucus –Goblet cell hyperplasia You realise this has affected his ability to transport gas (and presents). What is the rate of diffusion dependent on? –Area/thickness x concentration difference
LOGO You discover that Mr Claus lives in a very cold environment and wonder whether that could be also be affecting his oxygen dissociation curve. Does it? –Yes, low temp results in a shift to the left What else can shift the O 2 curve? –pH and 2,3 BPG. Is this the Bohr or the Haldane effect? –Bohr
LOGO Mr Claus tells you that he is planning a trip that will involve travelling at altitude for significant periods of time. Which type of respiratory failure would you be most worried about? –T–Type 1 – (hypoxaemic without hypercapnia) as very low P I O 2. Mr Claus wants antibiotics to help him get better. Which of the following is the most appropriate response? –T–Tell santa he’s on your naughty list for inhaling so many irritants so he can’t get what he wants. –G–Given that santa is a people pleaser you endeavour to copy and set him up for CT, CXR, FBC, PET scan etc. –C–Carry out a FEV1/FVC test and spirometry to help diagnose. –T–Tell santa that you know best and give him COPD meds
Case 2 Santa’s little helper walks through the door (imagine he’s human). He is breathing very quickly and his lips look blue. He says he has just inhaled a peanut. Where is it likely to have gone? –Right lung as right bronchus is more vertical What condition is He likely to be experiencing (remember it’s acute) –Atelectasis (partial collapse of the lung) What will happen to the alveoli distal to the peanut? –All their air will be taken into the blood and they will collapse
LOGO Santa’s little helper wonders why your alveoli don’t collapse all the time. Can you help him out? (2) –Surfactant released from type II pneumocytes interact with fluid in the lung to reduce surface tension and so reduces the likelihood of collapse. Does surfactant have any other roles? –Antioxidant effect –Immune function Atelectasis will also result in changes to the V/Q ratio. How will it change? –V/Q = 0
LOGO Can you explain why 100% O 2 won’t help him? –Regardless of how much O 2 he receives, no air is reaching the collapsed part and so there will be no improvement. The peanut is removed via bronchoscopy but his stats stay <88%. What treatment could you use to open his alveoli? –CPAP (continuous positive airway pressure)
LOGO After a long scuba diving session on a Caribbean reef, Carl boards a plane to Coventry. He begins to feel pain in his elbow on the flight back. What is happening to him? Carl is experiencing the bends due to several problems: 1.Applying Boyle's law, a lot of gas was forced into Carl's bloodstream during the dive to prevent his lung’s from collapsing and there was not sufficient time to decompress the excess before he boarded the plane. 2.The plane is not pressurized to sea level, which further reduced atmospheric pressure holding the gases in suspension (Henry's law). Carl will have to be transported to a hyperbaric chamber to be repressurized. This will reduce the volume of the gas bubbles in his arm so that normal circulation can resume.