The crucial aspect to note is that the phrenic nerve travels behind the inner side of the first rib. Towards the top, it is situated on the exterior of scalenus anterior.

The Phrenic Nerve: Origin, Path, and Supplies

The phrenic nerve is a crucial nerve that originates from the cervical spinal nerves C3, C4, and C5. It supplies the diaphragm and provides sensation to the central diaphragm and pericardium. The nerve passes with the internal jugular vein across scalenus anterior and deep to the prevertebral fascia of the deep cervical fascia.

The right phrenic nerve runs anterior to the first part of the subclavian artery in the superior mediastinum and laterally to the superior vena cava. In the middle mediastinum, it is located to the right of the pericardium and passes over the right atrium to exit the diaphragm at T8. On the other hand, the left phrenic nerve passes lateral to the left subclavian artery, aortic arch, and left ventricle. It passes anterior to the root of the lung and pierces the diaphragm alone.

Understanding the origin, path, and supplies of the phrenic nerve is essential in diagnosing and treating conditions that affect the diaphragm and pericardium.

Benign paroxysmal positional vertigo (BPPV) is suspected based on the patient’s history. To confirm the diagnosis, the Dix-Hallpike manoeuvre can be performed, which involves quickly moving the patient from a sitting to supine position and observing for nystagmus.

If BPPV is confirmed, the Epley manoeuvre can be used for treatment. This manoeuvre aims to dislodge otoliths by promoting fluid movement in the inner ear’s semicircular canals.

Carpal tunnel syndrome can be diagnosed by a positive Tinel’s sign. This involves tapping the median nerve over the flexor retinaculum, causing paraesthesia in the median nerve’s distribution.

The Trendelenburg test is used to assess venous valve competency in patients with varicose veins.

Benign paroxysmal positional vertigo (BPPV) is a common cause of vertigo that occurs suddenly when there is a change in head position. It is more prevalent in individuals over the age of 55 and is less common in younger patients. Symptoms of BPPV include dizziness and vertigo, which can be accompanied by nausea. Each episode typically lasts for 10-20 seconds and can be triggered by rolling over in bed or looking upwards. A positive Dix-Hallpike manoeuvre, which is indicated by vertigo and rotatory nystagmus, can confirm the diagnosis of BPPV.

Fortunately, BPPV has a good prognosis and usually resolves on its own within a few weeks to months. Treatment options include the Epley manoeuvre, which is successful in around 80% of cases, and vestibular rehabilitation exercises such as the Brandt-Daroff exercises. While medication such as Betahistine may be prescribed, it tends to have limited effectiveness. However, it is important to note that around half of individuals with BPPV may experience a recurrence of symptoms 3-5 years after their initial diagnosis.

The most likely diagnosis for this patient is granulomatosis with polyangiitis, as indicated by the presence of cANCA and the involvement of multiple organs including the lungs, skin, kidneys, and upper respiratory tract. This condition is known to cause inflammation in the glomeruli, leading to renal impairment. Churg-Strauss disease and Alport’s syndrome are unlikely due to normal eosinophil levels and cANCA positivity, respectively. Goodpasture’s syndrome is also unlikely as the patient does not present with haematuria or haemoptysis.

Granulomatosis with Polyangiitis: An Autoimmune Condition

Granulomatosis with polyangiitis, previously known as Wegener’s granulomatosis, is an autoimmune condition that affects the upper and lower respiratory tract as well as the kidneys. It is characterized by a necrotizing granulomatous vasculitis. The condition presents with various symptoms such as epistaxis, sinusitis, nasal crusting, dyspnoea, haemoptysis, and rapidly progressive glomerulonephritis. Other symptoms include a saddle-shape nose deformity, vasculitic rash, eye involvement, and cranial nerve lesions.

To diagnose granulomatosis with polyangiitis, doctors perform various investigations such as cANCA and pANCA tests, chest x-rays, and renal biopsies. The cANCA test is positive in more than 90% of cases, while the pANCA test is positive in 25% of cases. Chest x-rays show a wide variety of presentations, including cavitating lesions. Renal biopsies reveal epithelial crescents in Bowman’s capsule.

The management of granulomatosis with polyangiitis involves the use of steroids, cyclophosphamide, and plasma exchange. Cyclophosphamide has a 90% response rate. The median survival rate for patients with this condition is 8-9 years.

When a patient presents with unilateral foul smelling discharge and deafness, it is important to consider the possibility of a cholesteatoma. If this is suspected during examination, it is necessary to refer the patient to an ENT specialist.

Pain is a common symptom of otitis media, while otitis externa typically causes inflammation and swelling of the ear canal. Impacted wax can lead to deafness, but it is unlikely to cause a discharge with a foul odor. It is also improbable for a woman of 45 years to have a foreign object in her ear for three weeks.

Understanding Cholesteatoma

Cholesteatoma is a benign growth of squamous epithelium that can cause damage to the skull base. It is most commonly found in individuals between the ages of 10 and 20 years old. Those born with a cleft palate are at a higher risk of developing cholesteatoma, with a 100-fold increase in risk.

The main symptoms of cholesteatoma include a persistent discharge with a foul odor and hearing loss. Other symptoms may occur depending on the extent of the growth, such as vertigo, facial nerve palsy, and cerebellopontine angle syndrome.

During otoscopy, a characteristic attic crust may be seen in the uppermost part of the eardrum.

Management of cholesteatoma involves referral to an ear, nose, and throat specialist for surgical removal. Early detection and treatment are important to prevent further damage to the skull base and surrounding structures.

In summary, cholesteatoma is a non-cancerous growth that can cause significant damage if left untreated. It is important to be aware of the symptoms and seek medical attention promptly if they occur.

The maxillary sinus is susceptible to infections due to its drainage from the top. This sinus is the most frequently affected in cases of sinusitis. While frontal sinusitis can lead to intracranial complications, it is still less common than maxillary sinusitis.

The petrosal sinus is not a bone cavity, but rather a venous structure situated beneath the brain.

Acute sinusitis is a condition where the mucous membranes of the paranasal sinuses become inflamed. This inflammation is usually caused by infectious agents such as Streptococcus pneumoniae, Haemophilus influenzae, and rhinoviruses. Certain factors can predispose individuals to this condition, including nasal obstruction, recent local infections, swimming/diving, and smoking. Symptoms of acute sinusitis include facial pain, nasal discharge, and nasal obstruction. Treatment options include analgesia, intranasal decongestants or nasal saline, and intranasal corticosteroids. Oral antibiotics may be necessary for severe presentations, but they are not typically required. In some cases, an initial viral sinusitis can worsen due to secondary bacterial infection, which is known as double-sickening.

If multiple individuals in an air conditioned space develop pneumonia, Legionella pneumophila should be considered as a possible cause. Legionella pneumophila is often associated with hyponatremia and lymphopenia. Haemophilus influenzae is a frequent cause of lower respiratory tract infections in patients with COPD. Klebsiella pneumoniae is commonly found in patients with alcohol dependence. Pneumocystis jiroveci is typically observed in HIV-positive patients and is characterized by a dry cough and desaturation during exercise.

Pneumonia is a common condition that affects the alveoli of the lungs, usually caused by a bacterial infection. Other causes include viral and fungal infections. Streptococcus pneumoniae is the most common organism responsible for pneumonia, accounting for 80% of cases. Haemophilus influenzae is common in patients with COPD, while Staphylococcus aureus often occurs in patients following influenzae infection. Mycoplasma pneumoniae and Legionella pneumophilia are atypical pneumonias that present with dry cough and other atypical symptoms. Pneumocystis jiroveci is typically seen in patients with HIV. Idiopathic interstitial pneumonia is a group of non-infective causes of pneumonia.

Patients who develop pneumonia outside of the hospital have community-acquired pneumonia (CAP), while those who develop it within hospitals are said to have hospital-acquired pneumonia. Symptoms of pneumonia include cough, sputum, dyspnoea, chest pain, and fever. Signs of systemic inflammatory response, tachycardia, reduced oxygen saturations, and reduced breath sounds may also be present. Chest x-ray is used to diagnose pneumonia, with consolidation being the classical finding. Blood tests, such as full blood count, urea and electrolytes, and CRP, are also used to check for infection.

Patients with pneumonia require antibiotics to treat the underlying infection and supportive care, such as oxygen therapy and intravenous fluids. Risk stratification is done using a scoring system called CURB-65, which stands for confusion, respiration rate, blood pressure, age, and is used to determine the management of patients with community-acquired pneumonia. Home-based care is recommended for patients with a CRB65 score of 0, while hospital assessment is recommended for all other patients, particularly those with a CRB65 score of 2 or more. The CURB-65 score also correlates with an increased risk of mortality at 30 days.

Haemophilus influenzae is a frequent culprit behind bacterial otitis media, a common ear infection.

The majority of cases of acute bacterial otitis media are caused by Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella.

Genital gonorrhoeae is caused by N. gonorrhoeae, a sexually transmitted infection that presents with discharge and painful urination.

Meningococcal sepsis, a life-threatening condition, is caused by N. meningitides.

Staph. aureus is responsible for superficial skin infections like impetigo.

Syphilis, which typically manifests as a painless genital sore called a chancre, is caused by T. pallidum.

Acute otitis media is a common condition in young children, often caused by bacterial infections following viral upper respiratory tract infections. Symptoms include ear pain, fever, and hearing loss, and diagnosis is based on criteria such as the presence of a middle ear effusion and inflammation of the tympanic membrane. Antibiotics may be prescribed in certain cases, and complications can include perforation of the tympanic membrane, hearing loss, and more serious conditions such as meningitis and brain abscess.

It is unlikely that direct injury would result in the elevation of the left hemidiaphragm, especially since there is no history of trauma or surgery. However, damage to the long thoracic nerve could cause winging of the scapula due to weakened serratus anterior muscle. On the other hand, injury to the thoracodorsal nerve, which innervates the latissimus dorsi muscle, can lead to weakened shoulder adduction and is a common complication of axillary surgery.

The Phrenic Nerve: Origin, Path, and Supplies

The phrenic nerve is a crucial nerve that originates from the cervical spinal nerves C3, C4, and C5. It supplies the diaphragm and provides sensation to the central diaphragm and pericardium. The nerve passes with the internal jugular vein across scalenus anterior and deep to the prevertebral fascia of the deep cervical fascia.

The right phrenic nerve runs anterior to the first part of the subclavian artery in the superior mediastinum and laterally to the superior vena cava. In the middle mediastinum, it is located to the right of the pericardium and passes over the right atrium to exit the diaphragm at T8. On the other hand, the left phrenic nerve passes lateral to the left subclavian artery, aortic arch, and left ventricle. It passes anterior to the root of the lung and pierces the diaphragm alone.

Understanding the origin, path, and supplies of the phrenic nerve is essential in diagnosing and treating conditions that affect the diaphragm and pericardium.

Both the lungs and vertebral bodies are located outside of the mediastinum.

The mediastinum is the area located between the two pulmonary cavities and is covered by the mediastinal pleura. It extends from the thoracic inlet at the top to the diaphragm at the bottom. The mediastinum is divided into four regions: the superior mediastinum, middle mediastinum, posterior mediastinum, and anterior mediastinum.

The superior mediastinum is the area between the manubriosternal angle and T4/5. It contains important structures such as the superior vena cava, brachiocephalic veins, arch of aorta, thoracic duct, trachea, oesophagus, thymus, vagus nerve, left recurrent laryngeal nerve, and phrenic nerve. The anterior mediastinum contains thymic remnants, lymph nodes, and fat. The middle mediastinum contains the pericardium, heart, aortic root, arch of azygos vein, and main bronchi. The posterior mediastinum contains the oesophagus, thoracic aorta, azygos vein, thoracic duct, vagus nerve, sympathetic nerve trunks, and splanchnic nerves.

In summary, the mediastinum is a crucial area in the thorax that contains many important structures and is divided into four regions. Each region contains different structures that are essential for the proper functioning of the body.

The patient is exhibiting symptoms and ABG results consistent with respiratory alkalosis. However, it is important to conduct a thorough history and physical examination to rule out any underlying pulmonary pathology or infection. Based on the patient’s history, anxiety-induced hyperventilation is the most probable cause of her condition.

Respiratory Alkalosis: Causes and Examples

Respiratory alkalosis is a condition that occurs when the blood pH level rises above the normal range due to excessive breathing. This can be caused by various factors, including anxiety, pulmonary embolism, CNS disorders, altitude, and pregnancy. Salicylate poisoning can also lead to respiratory alkalosis, but it may also cause metabolic acidosis in the later stages. In this case, the respiratory centre is stimulated early, leading to respiratory alkalosis, while the direct acid effects of salicylates combined with acute renal failure may cause acidosis later on. It is important to identify the underlying cause of respiratory alkalosis to determine the appropriate treatment. Proper management can help prevent complications and improve the patient’s overall health.

To calculate the total lung capacity, one can add the vital capacity and residual volume. For example, if the vital capacity is 3300 mL and the residual volume is 1200 mL, the total lung capacity would be 4500 mL. It is important to note that tidal volume, inspiratory capacity, and the FEV1/FVC ratio are other measurements related to lung function. Residual volume refers to the amount of air left in the lungs after a maximal exhalation, while total lung capacity refers to the volume of air in the lungs after a maximal inhalation.

Understanding Lung Volumes in Respiratory Physiology

In respiratory physiology, lung volumes can be measured to determine the amount of air that moves in and out of the lungs during breathing. The diagram above shows the different lung volumes that can be measured.

Tidal volume (TV) refers to the amount of air that is inspired or expired with each breath at rest. In males, the TV is 500ml while in females, it is 350ml.

Inspiratory reserve volume (IRV) is the maximum volume of air that can be inspired at the end of a normal tidal inspiration. The inspiratory capacity is the sum of TV and IRV. On the other hand, expiratory reserve volume (ERV) is the maximum volume of air that can be expired at the end of a normal tidal expiration.

Residual volume (RV) is the volume of air that remains in the lungs after maximal expiration. It increases with age and can be calculated by subtracting ERV from FRC. Speaking of FRC, it is the volume in the lungs at the end-expiratory position and is equal to the sum of ERV and RV.

Vital capacity (VC) is the maximum volume of air that can be expired after a maximal inspiration. It decreases with age and can be calculated by adding inspiratory capacity and ERV. Lastly, total lung capacity (TLC) is the sum of vital capacity and residual volume.

Physiological dead space (VD) is calculated by multiplying tidal volume by the difference between arterial carbon dioxide pressure (PaCO2) and end-tidal carbon dioxide pressure (PeCO2) and then dividing the result by PaCO2.

COPD is typically found in older smokers, but non-smokers with A-1 antitrypsin deficiency may also develop the condition. This genetic condition is tested for with genetic and blood tests, as the protein it affects would normally protect lung cells from damage caused by neutrophil elastase. C1 inhibitor is not related to early onset COPD, but rather plays a role in hereditary angioedema. Plasminogen activator inhibitor-1 deficiency increases the risk of fibrinolysis, while surfactant protein D deficiency is associated with a higher likelihood of bacterial lung infections due to decreased ability of alveolar macrophages to bind to pathogens. Emphysema is primarily caused by uninhibited action of neutrophil elastase due to a1- antitrypsin deficiency, rather than elastin destruction.

Alpha-1 antitrypsin (A1AT) deficiency is a genetic condition that occurs when the liver does not produce enough of a protein called protease inhibitor (Pi). This protein is responsible for protecting cells from enzymes like neutrophil elastase. A1AT deficiency is inherited in an autosomal recessive or co-dominant manner and is located on chromosome 14. The alleles are classified by their electrophoretic mobility, with M being normal, S being slow, and Z being very slow. The normal genotype is PiMM, while heterozygous individuals have PiMZ. Homozygous PiSS individuals have 50% normal A1AT levels, while homozygous PiZZ individuals have only 10% normal A1AT levels.

A1AT deficiency is most commonly associated with panacinar emphysema, which is a type of chronic obstructive pulmonary disease (COPD). This is especially true for patients with the PiZZ genotype. Emphysema is more likely to occur in non-smokers with A1AT deficiency, but they may still pass on the gene to their children. In addition to lung problems, A1AT deficiency can also cause liver issues such as cirrhosis and hepatocellular carcinoma in adults, and cholestasis in children.

Diagnosis of A1AT deficiency involves measuring A1AT concentrations and performing spirometry to assess lung function. Management of the condition includes avoiding smoking and receiving supportive care such as bronchodilators and physiotherapy. Intravenous alpha1-antitrypsin protein concentrates may also be used. In severe cases, lung volume reduction surgery or lung transplantation may be necessary.

During a median sternotomy, the interclavicular ligament is typically cut to allow access. However, it is important to avoid intentionally cutting the pleural reflections, as this can lead to the accumulation of fluid in the pleural cavity and require the insertion of a chest drain. The pectoralis major muscles may also be encountered, but if the incision is made in the midline, they should not need to be formally divided. It is crucial to be mindful of the proximity of the brachiocephalic vein and avoid injuring it, as this can result in significant bleeding.

Sternotomy Procedure

A sternotomy is a surgical procedure that involves making an incision in the sternum to access the heart and great vessels. The most common type of sternotomy is a median sternotomy, which involves making a midline incision from the interclavicular fossa to the xiphoid process. The fat and subcutaneous tissues are then divided to the level of the sternum, and the periosteum may be gently mobilized off the midline. However, it is important to avoid vigorous periosteal stripping. A bone saw is used to divide the bone itself, and bleeding from the bony edges of the cut sternum is stopped using roller ball diathermy or bone wax.

Posteriorly, the reflections of the parietal pleura should be identified and avoided, unless surgery to the lung is planned. The fibrous pericardium is then incised, and the heart is brought into view. It is important to avoid the left brachiocephalic vein, which is an important posterior relation at the superior aspect of the sternotomy incision. More inferiorly, the thymic remnants may be identified. At the inferior aspect of the incision, the abdominal cavity may be entered, although this is seldom troublesome.

Overall, a sternotomy is a complex surgical procedure that requires careful attention to detail and a thorough understanding of the anatomy of the chest and heart. By following the proper techniques and precautions, surgeons can safely access the heart and great vessels to perform a variety of life-saving procedures.

The tensor tympani muscle is located in a bony canal above the pharyngotympanic tube and originates from the cartilaginous portion of the tube, the bony canal, and the greater wing of the sphenoid bone. Its function is to reduce the magnitude of vibrations transmitted into the middle ear by pulling the handle of the malleus medially when contracted. This muscle is innervated by the nerve to tensor tympani, which arises from the mandibular nerve.

The middle ear contains three ossicles, which are the malleus, incus, and stapes. The malleus is the most lateral and attaches to the tympanic membrane, while the incus lies between and articulates with the other two ossicles. The stapes is the most medial and is connected to the oval window of the cochlea. The stapedius muscle is associated with the stapes. The lunate and trapezium are not bones of the middle ear but are carpal bones.

A patient with ear pain, difficulty hearing, dizziness, and fever may have otitis media, which is confirmed on otoscopy by a bulging tympanic membrane and visible fluid level.

Anatomy of the Ear

The ear is divided into three distinct regions: the external ear, middle ear, and internal ear. The external ear consists of the auricle and external auditory meatus, which are innervated by the greater auricular nerve and auriculotemporal branch of the trigeminal nerve. The middle ear is the space between the tympanic membrane and cochlea, and is connected to the nasopharynx by the eustachian tube. The tympanic membrane is composed of three layers and is approximately 1 cm in diameter. The middle ear is innervated by the glossopharyngeal nerve. The ossicles, consisting of the malleus, incus, and stapes, transmit sound vibrations from the tympanic membrane to the inner ear. The internal ear contains the cochlea, which houses the organ of corti, the sense organ of hearing. The vestibule accommodates the utricule and saccule, which contain endolymph and are surrounded by perilymph. The semicircular canals, which share a common opening into the vestibule, lie at various angles to the petrous temporal bone.

Hypercapnia causes a shift in the oxygen dissociation curve to the right. This means that for the same partial pressure of oxygen, the hemoglobin saturation will be less. Other factors that can cause a right shift in the curve include high altitudes, anaerobic metabolism resulting in the production of lactic acid, physical activity, and an increase in temperature. These shifts allow the body tissues to extract more oxygen from the blood, resulting in a lower hemoglobin saturation of the blood leaving the body tissues. Carbon dioxide is also known to produce a right shift in the curve, further contributing to this effect.

Understanding the Oxygen Dissociation Curve

The oxygen dissociation curve is a graphical representation of the relationship between the percentage of saturated haemoglobin and the partial pressure of oxygen in the blood. It is not influenced by the concentration of haemoglobin. The curve can shift to the left or right, indicating changes in oxygen delivery to tissues. When the curve shifts to the left, there is increased saturation of haemoglobin with oxygen, resulting in decreased oxygen delivery to tissues. Conversely, when the curve shifts to the right, there is reduced saturation of haemoglobin with oxygen, leading to enhanced oxygen delivery to tissues.

The L rule is a helpful mnemonic to remember the factors that cause a shift to the left, resulting in lower oxygen delivery. These factors include low levels of hydrogen ions (alkali), low partial pressure of carbon dioxide, low levels of 2,3-diphosphoglycerate, and low temperature. On the other hand, the mnemonic ‘CADET, face Right!’ can be used to remember the factors that cause a shift to the right, leading to raised oxygen delivery. These factors include carbon dioxide, acid, 2,3-diphosphoglycerate, exercise, and temperature.

Understanding the oxygen dissociation curve is crucial in assessing the oxygen-carrying capacity of the blood and the delivery of oxygen to tissues. By knowing the factors that can shift the curve to the left or right, healthcare professionals can make informed decisions in managing patients with respiratory and cardiovascular diseases.

An accumulation of pus in the pleural space, known as empyema, is a possible complication of pneumonia and is responsible for the patient’s pleurisy. Streptococcus pneumoniae, the most frequent cause of pneumonia, is also the leading cause of empyema.

Pneumonia is a common condition that affects the alveoli of the lungs, usually caused by a bacterial infection. Other causes include viral and fungal infections. Streptococcus pneumoniae is the most common organism responsible for pneumonia, accounting for 80% of cases. Haemophilus influenzae is common in patients with COPD, while Staphylococcus aureus often occurs in patients following influenzae infection. Mycoplasma pneumoniae and Legionella pneumophilia are atypical pneumonias that present with dry cough and other atypical symptoms. Pneumocystis jiroveci is typically seen in patients with HIV. Idiopathic interstitial pneumonia is a group of non-infective causes of pneumonia.

Patients who develop pneumonia outside of the hospital have community-acquired pneumonia (CAP), while those who develop it within hospitals are said to have hospital-acquired pneumonia. Symptoms of pneumonia include cough, sputum, dyspnoea, chest pain, and fever. Signs of systemic inflammatory response, tachycardia, reduced oxygen saturations, and reduced breath sounds may also be present. Chest x-ray is used to diagnose pneumonia, with consolidation being the classical finding. Blood tests, such as full blood count, urea and electrolytes, and CRP, are also used to check for infection.

Patients with pneumonia require antibiotics to treat the underlying infection and supportive care, such as oxygen therapy and intravenous fluids. Risk stratification is done using a scoring system called CURB-65, which stands for confusion, respiration rate, blood pressure, age, and is used to determine the management of patients with community-acquired pneumonia. Home-based care is recommended for patients with a CRB65 score of 0, while hospital assessment is recommended for all other patients, particularly those with a CRB65 score of 2 or more. The CURB-65 score also correlates with an increased risk of mortality at 30 days.

In acidosis, the oxyhaemoglobin dissociation curve shifts to the right, indicating a decrease in affinity of haemoglobin for oxygen. This is due to an increase in the number of [H+] ions, reflecting greater metabolic activity. Low [H+] levels cause a shift to the left. The low HCO3- in this patient can be explained by metabolic acidosis, but it does not cause a shift in the oxyhaemoglobin dissociation curve. Hypokalaemia may be a result of treatment for diabetic ketoacidosis, but it does not cause a shift in the oxygen dissociation curve. When temperature increases, the oxyhaemoglobin dissociation curve also shifts to the right, causing a decrease in haemoglobin affinity for oxygen. Hypothermia causes a shift to the left, indicating an increased affinity of haemoglobin for oxygen.

Understanding the Oxygen Dissociation Curve

The oxygen dissociation curve is a graphical representation of the relationship between the percentage of saturated haemoglobin and the partial pressure of oxygen in the blood. It is not influenced by the concentration of haemoglobin. The curve can shift to the left or right, indicating changes in oxygen delivery to tissues. When the curve shifts to the left, there is increased saturation of haemoglobin with oxygen, resulting in decreased oxygen delivery to tissues. Conversely, when the curve shifts to the right, there is reduced saturation of haemoglobin with oxygen, leading to enhanced oxygen delivery to tissues.

The L rule is a helpful mnemonic to remember the factors that cause a shift to the left, resulting in lower oxygen delivery. These factors include low levels of hydrogen ions (alkali), low partial pressure of carbon dioxide, low levels of 2,3-diphosphoglycerate, and low temperature. On the other hand, the mnemonic ‘CADET, face Right!’ can be used to remember the factors that cause a shift to the right, leading to raised oxygen delivery. These factors include carbon dioxide, acid, 2,3-diphosphoglycerate, exercise, and temperature.

Understanding the oxygen dissociation curve is crucial in assessing the oxygen-carrying capacity of the blood and the delivery of oxygen to tissues. By knowing the factors that can shift the curve to the left or right, healthcare professionals can make informed decisions in managing patients with respiratory and cardiovascular diseases.

Extrinsic compression causes an increase in intrapleural pressure during a Valsalva manoeuvre.

Understanding Pleural Pressure

Pleural pressure refers to the pressure surrounding the lungs within the pleural space. The pleura is a thin membrane that invests the lungs and lines the walls of the thoracic cavity. The visceral pleura covers the lung, while the parietal pleura covers the chest wall. The two sides are continuous and meet at the hilum of the lung. The size of the lung is determined by the difference between the alveolar pressure and the pleural pressure, or the transpulmonary pressure.

During quiet breathing, the pleural pressure is negative, meaning it is below atmospheric pressure. However, during active expiration, the abdominal muscles contract to force up the diaphragm, resulting in positive pleural pressure. This may temporarily collapse the bronchi and cause limitation of air flow.

Gravity affects pleural pressure, with the pleural pressure at the base of the lung being greater (less negative) than at its apex in an upright individual. When lying on the back, the pleural pressure becomes greatest along the back. Alveolar pressure is uniform throughout the lung, so the top of the lung generally experiences a greater transpulmonary pressure and is therefore more expanded and less compliant than the bottom of the lung.

In summary, understanding pleural pressure is important in understanding lung function and how it is affected by various factors such as gravity and muscle contraction.

Compression of the subclavian artery by a cervical rib can result in an absent radial pulse, which is a common symptom of thoracic outlet syndrome. Adson’s test can be used to diagnose this condition, which can be mistaken for cervical radiculopathy. Flapping tremors are typically observed in patients with encephalopathy caused by liver failure or carbon dioxide retention. An irregular pulse may indicate an arrhythmia like atrial fibrillation or heart block. Aortic stenosis, which is characterized by an ejection systolic murmur, often causes older patients to experience loss of consciousness during physical activity. A bounding pulse, on the other hand, is a sign of strong myocardial contractions that may be caused by heart failure, arrhythmias, pregnancy, or thyroid disease.

Cervical ribs are a rare anomaly that affects only 0.2-0.4% of the population. They are often associated with neurological symptoms and are caused by an anomalous fibrous band that originates from the seventh cervical vertebrae and may arc towards the sternum. While most cases are congenital and present around the third decade of life, some cases have been reported to occur following trauma. Bilateral cervical ribs are present in up to 70% of cases. Compression of the subclavian artery can lead to absent radial pulse and a positive Adsons test, which involves lateral flexion of the neck towards the symptomatic side and traction of the symptomatic arm. Treatment is usually only necessary when there is evidence of neurovascular compromise, and the traditional operative method for excision is a transaxillary approach.

Insertion of a chest drain poses a risk of damaging the long thoracic nerve, which runs from the neck to the serratus anterior muscle. This can result in weakness or paralysis of the muscle, causing a winged scapula that is noticeable along the medial border of the scapula. It is important to use aseptic technique during the procedure to prevent hospital-acquired pleural infection. Chylothorax, pneumothorax, and pyothorax are all conditions that may require chest drain insertion, but they are not known complications of the procedure. Therefore, these options are not applicable.

Anatomy of Chest Drain Insertion

Chest drain insertion is necessary for various medical conditions such as trauma, haemothorax, pneumothorax, and pleural effusion. The size of the chest drain used depends on the specific condition being treated. While ultrasound guidance is an option, the anatomical method is typically tested in exams.

It is recommended that chest drains are placed in the safe triangle, which is located in the mid axillary line of the 5th intercostal space. This triangle is bordered by the anterior edge of the latissimus dorsi, the lateral border of pectoralis major, a line superior to the horizontal level of the nipple, and the apex below the axilla. Another triangle, known as the triangle of auscultation, is situated behind the scapula and is bounded by the trapezius, latissimus dorsi, and vertebral border of the scapula. By folding the arms across the chest and bending forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for auscultation.

References:
– Prof Harold Ellis. The applied anatomy of chest drains insertions. British Journal of hospital medicine 2007; (68): 44-45.
– Laws D, Neville E, Duffy J. BTS guidelines for insertion of chest drains. Thorax, 2003; (58): 53-59.

To access the ansa cervicalis, one must cut through the pretracheal fascia on the posterolateral side of the thyroid gland. This nerve is located in front of the carotid sheath. However, it should be noted that the pre vertebral fascia is situated further back and cannot be reached by dividing the investing layer of fascia.

The ansa cervicalis is a nerve that provides innervation to the sternohyoid, sternothyroid, and omohyoid muscles. It is composed of two roots: the superior root, which branches off from C1 and is located anterolateral to the carotid sheath, and the inferior root, which is derived from the C2 and C3 roots and passes posterolateral to the internal jugular vein. The inferior root enters the inferior aspect of the strap muscles, which are located in the neck, and should be divided in their upper half when exposing a large goitre. The ansa cervicalis is situated in front of the carotid sheath and is an important nerve for the proper functioning of the neck muscles.

The internal laryngeal nerve is responsible for providing sensory information to the supraglottis and branches off from the superior laryngeal nerve. It is important to note that the cervical plexus, external laryngeal nerve, recurrent laryngeal nerve, and superior laryngeal nerve do not perform the same function as the internal laryngeal nerve.

Anatomy of the Larynx

The larynx is located in the front of the neck, between the third and sixth cervical vertebrae. It is made up of several cartilaginous segments, including the paired arytenoid, corniculate, and cuneiform cartilages, as well as the single thyroid, cricoid, and epiglottic cartilages. The cricoid cartilage forms a complete ring. The laryngeal cavity extends from the laryngeal inlet to the inferior border of the cricoid cartilage and is divided into three parts: the laryngeal vestibule, the laryngeal ventricle, and the infraglottic cavity.

The vocal folds, also known as the true vocal cords, control sound production. They consist of the vocal ligament and the vocalis muscle, which is the most medial part of the thyroarytenoid muscle. The glottis is composed of the vocal folds, processes, and rima glottidis, which is the narrowest potential site within the larynx.

The larynx is also home to several muscles, including the posterior cricoarytenoid, lateral cricoarytenoid, thyroarytenoid, transverse and oblique arytenoids, vocalis, and cricothyroid muscles. These muscles are responsible for various actions, such as abducting or adducting the vocal folds and relaxing or tensing the vocal ligament.

The larynx receives its arterial supply from the laryngeal arteries, which are branches of the superior and inferior thyroid arteries. Venous drainage is via the superior and inferior laryngeal veins. Lymphatic drainage varies depending on the location within the larynx, with the vocal cords having no lymphatic drainage and the supraglottic and subglottic parts draining into different lymph nodes.

Overall, understanding the anatomy of the larynx is important for proper diagnosis and treatment of various conditions affecting this structure.

The oblique and horizontal fissures are present in the right lung. The lower lobe is separated from the middle and upper lobes by the upper oblique fissure. The superior and middle lobes are separated by the short horizontal fissure.

Anatomy of the Lungs

The lungs are a pair of organs located in the chest cavity that play a vital role in respiration. The right lung is composed of three lobes, while the left lung has two lobes. The apex of both lungs is approximately 4 cm superior to the sternocostal joint of the first rib. The base of the lungs is in contact with the diaphragm, while the costal surface corresponds to the cavity of the chest. The mediastinal surface contacts the mediastinal pleura and has the cardiac impression. The hilum is a triangular depression above and behind the concavity, where the structures that form the root of the lung enter and leave the viscus. The right main bronchus is shorter, wider, and more vertical than the left main bronchus. The inferior borders of both lungs are at the 6th rib in the mid clavicular line, 8th rib in the mid axillary line, and 10th rib posteriorly. The pleura runs two ribs lower than the corresponding lung level. The bronchopulmonary segments of the lungs are divided into ten segments, each with a specific function.

Side Effects of Buproprion

Buproprion is a medication that can cause aggression and hallucination in some patients. However, the more common side effects are gastrointestinal disturbances such as diarrhoea, nausea, and dry mouth. These side effects are often experienced by patients taking buproprion. It is important to be aware of the potential side effects of any medication and to speak with a healthcare provider if any concerns arise. Additional information on buproprion and its potential side effects can be found in the electronic Medicines Compendium and Medicines Complete.

The patient’s prolonged smoking history and current symptoms suggest a diagnosis of chronic bronchitis and possibly emphysema, both of which are obstructive lung diseases. These conditions cause air to become trapped in the lungs, making it difficult to breathe out. Pulmonary function tests typically show a greater decrease in FEV1 than FVC in obstructive lung diseases, resulting in a lower FEV1/FVC ratio (also known as the Tiffeneau-Pinelli index). This is different from restrictive lung diseases, which may sometimes show an increase in the FEV1/FVC ratio due to a larger decrease in FVC than FEV1. Chest X-rays may reveal hyperinflated lungs in patients with obstructive lung diseases. An increase in FEV1 may occur in healthy individuals after exercise training or in patients with conditions like asthma after taking medication. Restrictive lung diseases, such as pneumoconioses, hypersensitivity pneumonitis, and idiopathic pulmonary fibrosis, are typically associated with a decrease in the FEV1/FVC ratio.

Understanding Pulmonary Function Tests

Pulmonary function tests are a useful tool in determining whether a respiratory disease is obstructive or restrictive. These tests measure various aspects of lung function, such as forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). By analyzing the results of these tests, doctors can diagnose and monitor conditions such as asthma, COPD, pulmonary fibrosis, and neuromuscular disorders.

In obstructive lung diseases, such as asthma and COPD, the FEV1 is significantly reduced, while the FVC may be reduced or normal. The FEV1% (FEV1/FVC) is also reduced. On the other hand, in restrictive lung diseases, such as pulmonary fibrosis and asbestosis, the FEV1 is reduced, but the FVC is significantly reduced. The FEV1% (FEV1/FVC) may be normal or increased.

It is important to note that there are many conditions that can affect lung function, and pulmonary function tests are just one tool in diagnosing and managing respiratory diseases. However, understanding the results of these tests can provide valuable information for both patients and healthcare providers.

The diaphragm of patients with COPD often appears flattened on a chest X-ray due to the chronic expiratory airflow obstruction causing dynamic hyperinflation of the lungs. Pleural effusions are commonly associated with infection, malignancy, or heart failure, while empyema is a result of pus accumulation in the pleural space caused by an infection.

Understanding COPD: Symptoms and Diagnosis

Chronic obstructive pulmonary disease (COPD) is a common medical condition that includes chronic bronchitis and emphysema. Smoking is the leading cause of COPD, and patients with mild disease may only need occasional use of a bronchodilator, while severe cases may result in frequent hospital admissions due to exacerbations. Symptoms of COPD include a productive cough, dyspnea, wheezing, and in severe cases, right-sided heart failure leading to peripheral edema.

To diagnose COPD, doctors may recommend post-bronchodilator spirometry to demonstrate airflow obstruction, a chest x-ray to check for hyperinflation, bullae, and flat hemidiaphragm, and to exclude lung cancer. A full blood count may also be necessary to exclude secondary polycythemia, and body mass index (BMI) calculation is important. The severity of COPD is categorized using the FEV1, with a ratio of less than 70% indicating airflow obstruction. The grading system has changed following the 2010 NICE guidelines, with Stage 1 – mild now including patients with an FEV1 greater than 80% predicted but with a post-bronchodilator FEV1/FVC ratio of less than 0.7. Measuring peak expiratory flow is of limited value in COPD, as it may underestimate the degree of airflow obstruction.

In summary, COPD is a common condition caused by smoking that can result in a range of symptoms and severity. Diagnosis involves various tests to check for airflow obstruction, exclude lung cancer, and determine the severity of the disease.

At this location, the phrenic nerve is situated in front. The vagus nerve runs in front and then curves backwards just above the base of the left bronchus, releasing the recurrent laryngeal nerve as it curves.

Anatomy of the Lungs

The lungs are a pair of organs located in the chest cavity that play a vital role in respiration. The right lung is composed of three lobes, while the left lung has two lobes. The apex of both lungs is approximately 4 cm superior to the sternocostal joint of the first rib. The base of the lungs is in contact with the diaphragm, while the costal surface corresponds to the cavity of the chest. The mediastinal surface contacts the mediastinal pleura and has the cardiac impression. The hilum is a triangular depression above and behind the concavity, where the structures that form the root of the lung enter and leave the viscus. The right main bronchus is shorter, wider, and more vertical than the left main bronchus. The inferior borders of both lungs are at the 6th rib in the mid clavicular line, 8th rib in the mid axillary line, and 10th rib posteriorly. The pleura runs two ribs lower than the corresponding lung level. The bronchopulmonary segments of the lungs are divided into ten segments, each with a specific function.

Types of Pneumocytes and Their Functions

Pneumocytes are specialized cells found in the lungs that play a crucial role in gas exchange. There are two main types of pneumocytes: type 1 and type 2. Type 1 pneumocytes are very thin squamous cells that cover around 97% of the alveolar surface. On the other hand, type 2 pneumocytes are cuboidal cells that secrete surfactant, a substance that reduces surface tension in the alveoli and prevents their collapse during expiration.

Type 2 pneumocytes start to develop around 24 weeks gestation, but adequate surfactant production does not take place until around 35 weeks. This is why premature babies are prone to respiratory distress syndrome. In addition, type 2 pneumocytes can differentiate into type 1 pneumocytes during lung damage, helping to repair and regenerate damaged lung tissue.

Apart from pneumocytes, there are also club cells (previously termed Clara cells) found in the bronchioles. These non-ciliated dome-shaped cells have a varied role, including protecting against the harmful effects of inhaled toxins and secreting glycosaminoglycans and lysozymes. Understanding the different types of pneumocytes and their functions is essential in comprehending the complex mechanisms involved in respiration.

Hypoxia causes vasoconstriction of pulmonary arteries, leading to a diagnosis of right heart failure secondary to hypoxic lung disease, also known as cor pulmonale.

The Effects of Hypoxia on Pulmonary Arteries

When the partial pressure of oxygen in the blood decreases, the pulmonary arteries undergo vasoconstriction. This means that the blood vessels narrow, allowing blood to be redirected to areas of the lung that are better aerated. This response is a natural mechanism that helps to improve the efficiency of gaseous exchange in the lungs. By diverting blood to areas with more oxygen, the body can ensure that the tissues receive the oxygen they need to function properly. Overall, hypoxia triggers a physiological response that helps to maintain homeostasis in the body.

Trismus, which is difficulty in opening the mouth, is a common symptom of peritonsillar abscess (also known as quinsy). It is important to note that quinsy is a complication of tonsillitis, not acute tonsillitis itself. Epiglottitis may present with muffled voice, drooling, and difficulty in breathing, while infectious mononucleosis is associated with other symptoms such as weight loss, fatigue, and enlarged lymph nodes and organs.

Peritonsillar Abscess: Symptoms and Treatment

A peritonsillar abscess, also known as quinsy, is a complication that can arise from bacterial tonsillitis. This condition is characterized by severe throat pain that is localized to one side, along with difficulty opening the mouth and reduced neck mobility. Additionally, the uvula may be deviated to the unaffected side. It is important to seek urgent medical attention from an ENT specialist if these symptoms are present.

The treatment for a peritonsillar abscess typically involves needle aspiration or incision and drainage, along with intravenous antibiotics. In some cases, a tonsillectomy may be recommended to prevent recurrence of the abscess. It is important to follow the recommended treatment plan and attend all follow-up appointments to ensure proper healing and prevent complications.