A pleural effusion refers to an excess accumulation of fluid in the pleural cavity, which is the space between the parietal and visceral pleura. Normally, this cavity contains a small amount of lubricating fluid, around 5-10 ml, that allows the pleurae to slide smoothly over each other. This fluid also creates surface tension, bringing the two membranes together and ensuring that as the thorax expands, the lungs expand and fill with air. However, when there is too much fluid in the pleural cavity, it hinders breathing by limiting lung expansion.

Percutaneous pleural aspiration is commonly performed for two main reasons. Firstly, it is used to investigate pleural effusion, particularly when it is unilateral and exudative in nature. Secondly, it provides symptomatic relief for breathlessness caused by pleural effusion. However, the British Thoracic Society (BTS) guidelines recommend that pleural aspiration should not be carried out if there is suspicion of unilateral or bilateral transudative effusion, unless there are atypical features or failure of response to therapy. In urgent cases where respiratory distress is caused by pleural effusion, pleural aspiration can also be used to quickly decompress the pleural space.

During the procedure, the patient is typically seated upright with a pillow supporting their arms and head. It is important for the patient not to lean too far forward, as this increases the risk of injury to the liver and spleen. The conventional site for aspiration is in the mid-scapular line, about 10 cm lateral to the spine, and one or two spaces below the upper level of the fluid. To avoid damaging the intercostal nerves and vessels that run just below the rib, the needle should be inserted just above the upper border of the chosen rib.

Currently, there is no evidence to support the use of nebulised magnesium sulphate in the treatment of adults with asthma. For adults experiencing acute asthma, the recommended drug doses are as follows:

– Salbutamol: 5 mg administered through an oxygen-driven nebuliser.
– Ipratropium bromide: 500 mcg delivered via an oxygen-driven nebuliser.
– Prednisolone: 40-50 mg taken orally.
– Hydrocortisone: 100 mg administered intravenously.
– Magnesium sulphate: 1.2-2 g given intravenously over a period of 20 minutes.

Intravenous salbutamol may be considered (250 mcg administered slowly) only when inhaled therapy is not possible, such as when a patient is receiving bag-mask ventilation.

According to the current ALS guidelines, IV aminophylline can be considered in cases of severe or life-threatening asthma, following senior advice. If used, a loading dose of 5 mg/kg should be given over 20 minutes, followed by an infusion of 500-700 mcg/kg/hour. It is important to maintain serum theophylline levels below 20 mcg/ml to prevent toxicity.

For more information, please refer to the BTS/SIGN Guideline on the Management of Asthma.

One of the diagnostic criteria for ARDS is the presence of hypoxemia. Other criteria include the onset of symptoms within 7 days of a clinical insult or new/worsening respiratory symptoms, bilateral opacities on chest X-ray that cannot be fully explained by other conditions, and respiratory failure that cannot be fully attributed to cardiac failure or fluid overload.

Further Reading:

ARDS is a severe form of lung injury that occurs in patients with a predisposing risk factor. It is characterized by the onset of respiratory symptoms within 7 days of a known clinical insult, bilateral opacities on chest X-ray, and respiratory failure that cannot be fully explained by cardiac failure or fluid overload. Hypoxemia is also present, as indicated by a specific threshold of the PaO2/FiO2 ratio measured with a minimum requirement of positive end-expiratory pressure (PEEP) ≥5 cm H2O. The severity of ARDS is classified based on the PaO2/FiO2 ratio, with mild, moderate, and severe categories.

Lung protective ventilation is a set of measures aimed at reducing lung damage that may occur as a result of mechanical ventilation. Mechanical ventilation can cause lung damage through various mechanisms, including high air pressure exerted on lung tissues (barotrauma), over distending the lung (volutrauma), repeated opening and closing of lung units (atelectrauma), and the release of inflammatory mediators that can induce lung injury (biotrauma). These mechanisms collectively contribute to ventilator-induced lung injury (VILI).

The key components of lung protective ventilation include using low tidal volumes (5-8 ml/kg), maintaining inspiratory pressures (plateau pressure) below 30 cm of water, and allowing for permissible hypercapnia. However, there are some contraindications to lung protective ventilation, such as an unacceptable level of hypercapnia, acidosis, and hypoxemia. These factors need to be carefully considered when implementing lung protective ventilation strategies in patients with ARDS.

The BTS guidelines for managing acute asthma in adults provide the following recommendations:

Oxygen:
– It is important to give supplementary oxygen to all patients with acute severe asthma who have low levels of oxygen in their blood (hypoxemia). The goal is to maintain a blood oxygen saturation level (SpO2) between 94-98%. Even if pulse oximetry is not available, oxygen should still be administered.

β2 agonists therapy:
– High-dose inhaled β2 agonists should be used as the first-line treatment for patients with acute asthma. It is important to administer these medications as early as possible.
– Intravenous β2 agonists should be reserved for patients who cannot reliably use inhaled therapy.
– For patients with life-threatening asthma symptoms, nebulized β2 agonists driven by oxygen are recommended.
– In cases of severe asthma that does not respond well to an initial dose of β2 agonist, continuous nebulization with an appropriate nebulizer may be considered.

Ipratropium bromide:
– Nebulized ipratropium bromide (0.5 mg every 4-6 hours) should be added to β2 agonist treatment for patients with acute severe or life-threatening asthma, or those who do not respond well to initial β2 agonist therapy.

Steroid therapy:
– Steroids should be given in adequate doses for all cases of acute asthma attacks.
– Prednisolone should be continued at a dose of 40-50 mg daily for at least five days or until the patient recovers.

Other therapies:
– Nebulized magnesium is not recommended for the treatment of acute asthma in adults.
– A single dose of intravenous magnesium sulfate may be considered for patients with acute severe asthma (peak expiratory flow rate <50% of the best or predicted value) who do not respond well to inhaled bronchodilator therapy. However, this should only be done after consulting with senior medical staff.
– Routine prescription of antibiotics is not necessary for patients with acute asthma.

For more information, please refer to the BTS/SIGN Guideline on the Management of Asthma.

The most probable diagnosis in this situation is Goodpasture’s syndrome, a rare autoimmune vasculitic disorder characterized by three main symptoms: pulmonary hemorrhage, glomerulonephritis, and the presence of anti-glomerular basement membrane (Anti-GBM) antibodies. Goodpasture’s syndrome is more prevalent in men, particularly in smokers. It is also associated with HLA-B7 and HLA-DRw2.

The clinical manifestations of Goodpasture’s syndrome include constitutional symptoms like fever, fatigue, nausea, and weight loss. Patients may also experience hemoptysis or pulmonary hemorrhage, chest pain, breathlessness, and inspiratory crackles at the lung bases. Anemia due to bleeding within the lungs, arthralgia, rapidly progressive glomerulonephritis, hematuria, hypertension, and rarely hepatosplenomegaly may also be present.

Blood tests will reveal iron deficiency anemia, an elevated white cell count, and renal impairment. Elisa for Anti-GBM antibodies is highly sensitive and specific, but it is not widely available. Approximately 30% of patients may also have circulating antineutrophilic cytoplasmic antibodies (ANCAs), although these are not specific for Goodpasture’s syndrome and can be found in other conditions such as Wegener’s granulomatosis, which also cause renal impairment and pulmonary hemorrhage.

Diagnosis is typically confirmed through a renal biopsy, which can detect the presence of anti-GBM antibodies. This would be the most appropriate investigation to confirm the diagnosis in this case.

The management of Goodpasture’s syndrome involves a combination of plasmapheresis to remove circulating antibodies and the use of corticosteroids or cyclophosphamide.

The recommended daily oral dose for adults is 900 mg, which should be taken in 2-3 divided doses. For severe asthma or COPD, the initial intravenous dose is 5 mg/kg and should be administered over 10-20 minutes. This can be followed by a continuous infusion of 0.5 mg/kg/hour. In the case of a 60 kg patient, the appropriate infusion rate would be 30 mg/hour. It is important to note that the therapeutic range for aminophylline is narrow, ranging from 10-20 microgram/ml. Therefore, it is beneficial to estimate the plasma concentration of aminophylline during long-term treatment.

The most likely diagnosis in this case is Goodpasture’s syndrome, which is a rare autoimmune vasculitic disorder. It is characterized by a triad of symptoms including pulmonary hemorrhage, glomerulonephritis, and the presence of anti-glomerular basement membrane (Anti-GBM) antibodies. Goodpasture’s syndrome is more commonly seen in men, particularly in smokers. There is also an association with certain HLA types, specifically HLA-B7 and HLA-DRw2.

The clinical features of Goodpasture’s syndrome include constitutional symptoms such as fever, fatigue, nausea, and weight loss. Patients may also experience haemoptysis or pulmonary hemorrhage, chest pain, breathlessness, and inspiratory crackles at the lung bases. Anemia due to intrapulmonary bleeding, arthralgia, rapidly progressive glomerulonephritis, haematuria, hypertension, and hepatosplenomegaly (rarely) may also be present.

Blood tests will reveal an iron deficiency anemia, elevated white cell count, and renal impairment. Elisa for Anti-GBM antibodies is highly sensitive and specific, but it is not widely available. Approximately 30% of patients may also have circulating antineutrophilic cytoplasmic antibodies (ANCAs), although these are not specific for Goodpasture’s syndrome and can be found in other conditions such as Wegener’s granulomatosis.

Diagnosis is typically confirmed through renal biopsy, which can detect the presence of anti-GBM antibodies. The management of Goodpasture’s syndrome involves a combination of plasmapheresis to remove circulating antibodies and the use of corticosteroids or cyclophosphamide.

It is important to note that this patient’s history is inconsistent with a diagnosis of pulmonary embolism, as renal impairment, haematuria, and the presence of ANCAs and anti-GBM antibodies would not be expected. While pulmonary hemorrhage and renal impairment can occur in systemic lupus erythematosus, these are uncommon presentations, and the presence of ANCAs and anti-GBM antibodies would also be inconsistent with this diagnosis.

Churg-Strauss syndrome can present with pulmonary hemorrhage, and c-ANCA may be present, but patients typically have a history of asthma, sinusitis, and eosinophilia. Wegener’s granulomatosis can present similarly to Goodpasture’s syndrome,

The recommended daily oral dose for adults is 900 mg, which should be taken in 2-3 divided doses. For severe asthma or COPD, the initial intravenous dose is 5 mg/kg and should be administered over 10-20 minutes. This can be followed by a continuous infusion of 0.5 mg/kg/hour. In the case of a 50 kg individual, the appropriate infusion rate would be 25 mg/hour. It is important to note that the therapeutic range for aminophylline is narrow, ranging from 10-20 microgram/ml. Therefore, it is beneficial to estimate the plasma concentration of aminophylline during long-term treatment.

Based on the clinical features of this individual, it is highly likely that they have pulmonary fibrosis. The key to determining the correct diagnosis is to differentiate between extrinsic allergic alveolitis (EAA) and idiopathic pulmonary fibrosis (IPF), also known as cryptogenic fibrosing alveolitis (CFA).

In this case, the gentleman does not have any occupational risk factors for EAA and exhibits digital clubbing. While clubbing is not commonly seen in EAA, it is a frequent occurrence in IPF. Therefore, based on these factors, IPF is the more probable diagnosis.

Spirometry results in IPF can either be normal or show a restrictive pattern, whereas an obstructive pattern would be expected in COPD. The history and clinical features presented do not align with the other diagnoses mentioned in this question.

This man is experiencing an acute asthma episode. His initial peak flow is 55% of his best, indicating a moderate exacerbation according to the BTS guidelines. Acute asthma can be classified as moderate, acute severe, life-threatening, or near-fatal.

Moderate asthma is characterized by increasing symptoms and a peak expiratory flow rate (PEFR) between 50-75% of the individual’s best or predicted value. There are no signs of acute severe asthma in this case.

Acute severe asthma is identified by any one of the following criteria: a PEFR between 33-50% of the best or predicted value, a respiratory rate exceeding 25 breaths per minute, a heart rate over 110 beats per minute, or the inability to complete sentences in one breath.

Life-threatening asthma is indicated by any one of the following: a PEFR below 33% of the best or predicted value, oxygen saturation (SpO2) below 92%, arterial oxygen pressure (PaO2) below 8 kPa, normal arterial carbon dioxide pressure (PaCO2) between 4.6-6.0 kPa, a silent chest, cyanosis, poor respiratory effort, arrhythmia, exhaustion, altered conscious level, or hypotension.

Near-fatal asthma is characterized by elevated PaCO2 levels and/or the need for mechanical ventilation with increased inflation pressures.

The recommended drug doses for adult acute asthma are as follows:

– Salbutamol: Administer 5 mg using an oxygen-driven nebulizer.
– Ipratropium bromide: Deliver 500 mcg via an oxygen-driven nebulizer.
– Prednisolone: Take orally at a dose of 40-50 mg.
– Hydrocortisone: Administer 100 mg intravenously.
– Magnesium sulphate: Infuse 1.2-2 g intravenously over a period of 20 minutes.

Terbutaline can be used as an alternative to salbutamol, with a dose of 10 mg via an oxygen-driven nebulizer. Intravenous salbutamol may be considered (250 mcg IV slowly) only when inhaled therapy is not possible, such as when a patient is receiving bag-mask ventilation.

According to the current ALS guidelines, IV aminophylline may be considered in severe or life-threatening asthma, following senior advice. If used, a loading dose of 5 mg/kg should be given over 20 minutes, followed by an infusion of 500-700 mcg/kg/hour. It is important to maintain serum theophylline levels below 20 mcg/ml to prevent toxicity.

For more information, please refer to the BTS/SIGN Guideline on the Management of Asthma.

This patient is displaying symptoms and signs that are in line with community-acquired pneumonia (CAP). The most frequent cause of CAP in an adult patient who is otherwise in good health is Streptococcus pneumoniae.

According to the current NICE guidelines on febrile illness in children under the age of 5, there are certain symptoms and signs that may indicate the presence of pneumonia. These include tachypnoea, which is a rapid breathing rate. For infants aged 0-5 months, a respiratory rate (RR) of over 60 breaths per minute is considered suggestive of pneumonia. For infants aged 6-12 months, an RR of over 50 breaths per minute is indicative, and for children older than 12 months, an RR of over 40 breaths per minute may suggest pneumonia.

Other signs that may point towards pneumonia include crackles in the chest, nasal flaring, chest indrawing, and cyanosis. Crackles are abnormal sounds heard during breathing, while nasal flaring refers to the widening of the nostrils during breathing. Chest indrawing is the inward movement of the chest wall during inhalation, and cyanosis is the bluish discoloration of the skin or mucous membranes due to inadequate oxygen supply.

Additionally, a low oxygen saturation level of less than 95% while breathing air is also considered suggestive of pneumonia. These guidelines can be found in more detail in the NICE guidelines on the assessment and initial management of fever in children under 5, as well as the NICE Clinical Knowledge Summary on the management of feverish children.

The BTS guidelines categorize acute asthma into four classifications: moderate, acute severe, life-threatening, and near-fatal.

Moderate asthma is characterized by increasing symptoms and a peak expiratory flow rate (PEFR) between 50-75% of the best or predicted value. There are no signs of acute severe asthma present in this classification.

Acute severe asthma is identified by any one of the following criteria: a PEFR between 33-50% of the best or predicted value, a respiratory rate exceeding 25 breaths per minute, a heart rate over 110 beats per minute, or the inability to complete sentences in one breath.

Life-threatening asthma is determined by any one of the following indicators: a PEFR below 33% of the best or predicted value, a blood oxygen saturation level (SpO2) below 92%, a partial pressure of oxygen (PaO2) below 8 kilopascals (kPa), a normal partial pressure of carbon dioxide (PaCO2) between 4.6-6.0 kPa, a silent chest, cyanosis, poor respiratory effort, arrhythmia, exhaustion, altered conscious level, or hypotension.

Near-fatal asthma is characterized by elevated PaCO2 levels and/or the need for mechanical ventilation with increased inflation pressures.

Bronchiolitis is a respiratory infection that primarily affects infants aged 2 to 6 months. It is typically caused by a viral infection, with respiratory syncytial virus (RSV) being the most common culprit. RSV infections are most prevalent during the winter months, from November to March. In fact, bronchiolitis is the leading cause of hospitalization among infants in the UK.

The symptoms of bronchiolitis include poor feeding (consuming less than 50% of their usual intake in the past 24 hours), lethargy, a history of apnea, a respiratory rate exceeding 70 breaths per minute, nasal flaring or grunting, severe chest wall recession, cyanosis (bluish discoloration of the skin), and low oxygen saturation levels. For children aged 6 weeks and older, oxygen saturation levels below 90% indicate a need for medical attention. For babies under 6 weeks or those with underlying health conditions, oxygen saturation levels below 92% require medical attention.

To confirm the diagnosis of bronchiolitis, a nasopharyngeal aspirate can be taken for rapid testing of RSV. This test is useful in preventing unnecessary further testing and allows for the isolation of the infected infant.

Most infants with bronchiolitis experience a mild, self-limiting illness that does not require hospitalization. Treatment primarily focuses on supportive measures, such as ensuring adequate fluid and nutritional intake and controlling the infant’s temperature. The illness typically lasts for 7 to 10 days.

However, hospital referral and admission are recommended in cases of poor feeding, lethargy, a history of apnea, a respiratory rate exceeding 70 breaths per minute, nasal flaring or grunting, severe chest wall recession, cyanosis, and oxygen saturation levels below 94%. If hospitalization is necessary, treatment involves supportive measures, supplemental oxygen, and nasogastric feeding as needed. There is limited or no evidence supporting the use of antibiotics, antivirals, bronchodilators, corticosteroids, hypertonic saline, or adrenaline nebulizers for the treatment of bronchiolitis.

The BTS guidelines for acute asthma in children recommend administering oral steroids early in the treatment of asthma attacks. It is advised to give a dose of 20 mg prednisolone for children aged 2–5 years and a dose of 30–40 mg for children over 5 years old. If a child is already taking maintenance steroid tablets, they should receive 2 mg/kg prednisolone, up to a maximum dose of 60 mg. If a child vomits after taking the medication, the dose of prednisolone should be repeated. In cases where a child is unable to keep down orally ingested medication, intravenous steroids should be considered. Typically, treatment for up to three days is sufficient, but the duration of the course should be adjusted based on the time needed for recovery. Tapering off the medication is not necessary unless the steroid course exceeds 14 days. For more information, refer to the BTS/SIGN Guideline on the Management of Asthma.

Arterial blood gases (ABG) are an important diagnostic tool used to assess a patient’s acid-base status and respiratory function. When obtaining an ABG sample, it is crucial to prioritize safety measures to minimize the risk of infection and harm to the patient. This includes performing hand hygiene before and after the procedure, wearing gloves and protective equipment, disinfecting the puncture site with alcohol, using safety needles when available, and properly disposing of equipment in sharps bins and contaminated waste bins.

To reduce the risk of harm to the patient, it is important to test for collateral circulation using the modified Allen test for radial artery puncture. Additionally, it is essential to inquire about any occlusive vascular conditions or anticoagulation therapy that may affect the procedure. The puncture site should be checked for signs of infection, injury, or previous surgery. After the test, pressure should be applied to the puncture site or the patient should be advised to apply pressure for at least 5 minutes to prevent bleeding.

Interpreting ABG results requires a systematic approach. The core set of results obtained from a blood gas analyser includes the partial pressures of oxygen and carbon dioxide, pH, bicarbonate concentration, and base excess. These values are used to assess the patient’s acid-base status.

The pH value indicates whether the patient is in acidosis, alkalosis, or within the normal range. A pH less than 7.35 indicates acidosis, while a pH greater than 7.45 indicates alkalosis.

The respiratory system is assessed by looking at the partial pressure of carbon dioxide (pCO2). An elevated pCO2 contributes to acidosis, while a low pCO2 contributes to alkalosis.

The metabolic aspect is assessed by looking at the bicarbonate (HCO3-) level and the base excess. A high bicarbonate concentration and base excess indicate alkalosis, while a low bicarbonate concentration and base excess indicate acidosis.

Analyzing the pCO2 and base excess values can help determine the primary disturbance and whether compensation is occurring. For example, a respiratory acidosis (elevated pCO2) may be accompanied by metabolic alkalosis (elevated base excess) as a compensatory response.

The anion gap is another important parameter that can help determine the cause of acidosis. It is calculated by subtracting the sum of chloride and bicarbonate from the sum of sodium and potassium.

Whooping cough is a respiratory infection caused by the bacteria Bordetella pertussis. It is highly contagious and can be transmitted to about 90% of close household contacts. The Health Protection Agency has identified two priority groups for public health action in managing whooping cough contacts.

Group 1 consists of individuals who are at a higher risk of severe or complicated infection. This includes infants under one year old who have received less than three doses of the pertussis vaccine.

Group 2 consists of individuals who are at a higher risk of transmitting the infection to those in Group 1. This includes pregnant women who are at or beyond 32 weeks of gestation, healthcare workers who work with infants and pregnant women, individuals who work with infants too young to be vaccinated (under 4 months old), and individuals who share a household with infants too young to be vaccinated.

According to current guidance, antibiotic prophylaxis with a macrolide antibiotic, like erythromycin, should only be offered to close contacts if two criteria are met. First, the index case (the person with whooping cough) must have developed symptoms within the past 21 days. Second, there must be a close contact in one of the two priority groups.

If both criteria are met, all contacts, regardless of their vaccination status and age, should be offered chemoprophylaxis. In this case, the mother is in Group 2, so the current recommendation is that all household contacts, including the mother, father, and brother, should receive chemoprophylaxis.

Additionally, immunization or a booster dose should be considered for those who have been offered chemoprophylaxis, depending on their current vaccination status.

A PaO2/FiO2 ratio ranging from 100 mmHg to 200 mmHg indicates the presence of moderate Acute Respiratory Distress Syndrome (ARDS).

Further Reading:

ARDS is a severe form of lung injury that occurs in patients with a predisposing risk factor. It is characterized by the onset of respiratory symptoms within 7 days of a known clinical insult, bilateral opacities on chest X-ray, and respiratory failure that cannot be fully explained by cardiac failure or fluid overload. Hypoxemia is also present, as indicated by a specific threshold of the PaO2/FiO2 ratio measured with a minimum requirement of positive end-expiratory pressure (PEEP) ≥5 cm H2O. The severity of ARDS is classified based on the PaO2/FiO2 ratio, with mild, moderate, and severe categories.

Lung protective ventilation is a set of measures aimed at reducing lung damage that may occur as a result of mechanical ventilation. Mechanical ventilation can cause lung damage through various mechanisms, including high air pressure exerted on lung tissues (barotrauma), over distending the lung (volutrauma), repeated opening and closing of lung units (atelectrauma), and the release of inflammatory mediators that can induce lung injury (biotrauma). These mechanisms collectively contribute to ventilator-induced lung injury (VILI).

The key components of lung protective ventilation include using low tidal volumes (5-8 ml/kg), maintaining inspiratory pressures (plateau pressure) below 30 cm of water, and allowing for permissible hypercapnia. However, there are some contraindications to lung protective ventilation, such as an unacceptable level of hypercapnia, acidosis, and hypoxemia. These factors need to be carefully considered when implementing lung protective ventilation strategies in patients with ARDS.

The key initial management for tension pneumothorax is needle thoracocentesis. This procedure is crucial as it rapidly decompresses the tension and allows for more definitive management to be implemented. It is important to note that according to ATLS guidelines, needle thoracocentesis should no longer be performed at the second intercostal space midclavicular line. Studies have shown that the fourth or fifth intercostal space midaxillary line is more successful in reaching the thoracic cavity in adult patients. Therefore, ATLS now recommends this location for needle decompression in adult patients.

Further Reading:

A pneumothorax is an abnormal collection of air in the pleural cavity of the lung. It can be classified by cause as primary spontaneous, secondary spontaneous, or traumatic. Primary spontaneous pneumothorax occurs without any obvious cause in the absence of underlying lung disease, while secondary spontaneous pneumothorax occurs in patients with significant underlying lung diseases. Traumatic pneumothorax is caused by trauma to the lung, often from blunt or penetrating chest wall injuries.

Tension pneumothorax is a life-threatening condition where the collection of air in the pleural cavity expands and compresses normal lung tissue and mediastinal structures. It can be caused by any of the aforementioned types of pneumothorax. Immediate management of tension pneumothorax involves the ABCDE approach, which includes ensuring a patent airway, controlling the C-spine, providing supplemental oxygen, establishing IV access for fluid resuscitation, and assessing and managing other injuries.

Treatment of tension pneumothorax involves needle thoracocentesis as a temporary measure to provide immediate decompression, followed by tube thoracostomy as definitive management. Needle thoracocentesis involves inserting a 14g cannula into the pleural space, typically via the 4th or 5th intercostal space midaxillary line. If the patient is peri-arrest, immediate thoracostomy is advised.

The pathophysiology of tension pneumothorax involves disruption to the visceral or parietal pleura, allowing air to flow into the pleural space. This can occur through an injury to the lung parenchyma and visceral pleura, or through an entry wound to the external chest wall in the case of a sucking pneumothorax. Injured tissue forms a one-way valve, allowing air to enter the pleural space with inhalation but prohibiting air outflow. This leads to a progressive increase in the volume of non-absorbable intrapleural air with each inspiration, causing pleural volume and pressure to rise within the affected hemithorax.