Pneumothorax Short Notes

Pneumothorax Notes • • • • • • • • • • In pneumothorax the pressure in the pleural cavity (intra-pleural pressure) is greater than the pressure in the lungs (intra-pulmonary pressure) Since pressure likes to go from areas of high pressure to areas of low pressure, the pleural pressure will be pushing on the lungs causing them to collapse. Because the lungs will be collapsing this will cause the alveoli within to collapse rendering them dysfunctional or at least decreases their function. Because the alveoli function decreases there will be impaired oxygen and carbon dioxide exchange. This means that oxygen will not be able to diffuse into the blood, and carbon dioxide will not be diffusing out of the lungs to be exhaled. This will result in hypoxemia and hypercapnia. The increased CO2 levels will increase the concentration of H+ in the CSF, which will be detected by CCRs in the CSF This will stimulate the pre-Boz to stimulate DRG which will stimulate VRG which will increase action potentials in CN IX and CN X to innervate intercoastal muscles and diaphragm respectively, thereby increase the rate and depth of respiration. The low hypoxemic conditions are detected by peripheral chemoreceptors on the aortic and carotid arteries which contain glomus cells. The glomus cells will be exposed to low levels of oxygen which will cause the closure of oxygen dependant K+ channels. This will increase mV within the cells causing the opening of voltage gated Ca2+ channels which will cause dopamine vesicles to fuse with the cell membrane and exocytosis dopamine on nerve terminals of CIX and CX which will increase repo rate and depth through the pre-Boz pathway like mentioned above Practice Question on Pneumothroax 1. Meredith is a 30-year-old female with tension pneumothorax. She presents with elevated JVP, low blood pressure and shortness of breath. a. Based on the information given, is it likely that she has right deviation or left deviation? (0.5) b. List FOUR things you expect to see on an X-ray (2 marks) c. Explain why she has elevated JVP and low blood pressure (2 marks) d. Upon performing an ABG it is found she has very low levels of oxygen. The consultant asks you to place her on ventilation. What would the oxygen saturation you give be and why? (2 marks) e. Chest tube to drain air is one possible treatment. Where would it be inserted and what is ONE safety precaution you should be attention to. (1.5 marks) f. Name and briefly explain TWO other treatment options (2 marks) Answer: a. b. • • • • c. Right deviation X-ray findings: SVC and IVC compressed and in wrong space Heart deviated to the right More white seen -> indicative of air Trachea deviation to the right JVP is elevated because the SVC is compressed, so venous blood can’t return to the heart and will back into the jugular vein -> elevated JVP. The low blood pressure is because the SVC and IVC are compressed -> can’t return blood -> decreased preload and filling -> decreased cardiac output -> low blood pressure d. I would give her oxygen at 88 -92% saturation, not at 100% because this will reduce the ventilation drive. This is because the CCR become unstimulated to CO2 because it is the H+ that causes ventilation not the CO2 itself. The H+ in this case will be buffered by the kidney as the kidney will increase HCO3- which will buffer H+. So, the only drive for ventilation is hypoxemia. If we give them 100% then there will no breathing drive. e. The chest tube needle will be inserted at the 4th intercoastal space between the 4th and 5th rib. It will be inserted on the superior boarder of the 5th rib, rather than the inferior boarder of the 4th rib. This is because on the inferior boarder of the 4th rib there is the intercoastal neurovascular bundle and we want to avoid taking the risk of damaging them. f. Other treatment options • Chemical chest tube ->chemicals e.g., sulphur nitrate -> fibrotic reaction -> stick pleura together • Partial occlusive dressing (adhesion sticky tape on three out of the four sides, the one left, when inhale sucks towards defect and prevents air to come in, but when you exhale air sweeps out