The remainder of the lungs is made up of pulmonary connective tissue, much of which is elastic McGeown, Gaseous exchange takes place inside the lungs in an environment that is warm, moist and protected. The outer surfaces of the lungs are covered with a membrane called the pleura. The pleural membrane is thin, moist, slippery and has two layers. The outer, or parietal, pleura lines the inside of the rib cage and the diaphragm while the inner, visceral or pulmonary, layer covers the lungs.
Between the two layers is the intrapleural space, which normally contains fluid secreted by the membranes. This allows the two layers to slide easily over one another as the lungs inflate and deflate during respiration. It is difficult to compress or expand liquids so the two layers of pleura normally remain tightly adherent to one another.
This enables the lungs, which do not contain any skeletal muscle, to be expanded and relaxed by movements of the chest wall. In their normal, relaxed, resting position the lungs are considerably smaller than the thoracic cage in which they sit.
The seal of the pleura prevents the lungs from separating from the rib cage but the natural tendency of the thorax to spring out and the lungs to collapse produces forces pulling in opposite directions. This produces a negative pressure relative to atmospheric pressure inside the intrapleural space of about 0.
During inspiration this pressure becomes increasingly negative. Pleurisy is an inflammation of the pleural membrane, which causes pain when the membranes rub together.
Pleural effusion occurs when excess pleural fluid is formed through Law and Watson, :. If the pleural layers are ruptured, for example by a spontaneous rupture of the membrane or by a stab wound, air is sucked into the intrapleural space creating a real air-containing space between the lungs and chest wall - a pneumothorax. This abolishes the negative intrapleural pressure and the lung in the affected area will collapse.
Gas exchange will be seriously impaired because movement of the chest wall will no longer expand the lung. Protecting the delicate gas exchange surfaces in the lung is essential for health and the respiratory system has a number of ways of filtering incoming air:. Smoking is the most common cause. Learn more…. Popcorn lung is a rare condition marked by damage to the lung's smallest airways. The tissue becomes scarred and narrow, which leads to breathing….
Lung nodules are small growths on the lungs. They are very common, can be benign or malignant, and often do not cause symptoms. They usually show up…. A look at interstitial lung disease, a group of diseases that make it difficult to get enough oxygen. Included is detail on types and complications.
Scars on the lung tissue can cause shortness of breath, fever, and night sweats. Learn more about how scarring occurs and what to do about it here. What you should know about a punctured lung. Medically reviewed by Adithya Cattamanchi, M.
Overview Symptoms Treatment Recovery time Outlook A punctured lung involves air escaping from the lung into the space between it and the chest wall. How does a punctured lung occur? Share on Pinterest A punctured lung, which can cause a lung to collapse, may be caused by a violent injury. Treatment for a punctured lung. Share on Pinterest When there are no symptoms, a doctor may monitor the lungs with repeated X-rays.
Recovery time. Pulmonary System Respiratory Emergency Medicine. Latest news Adolescent depression: Could school screening help? Exposure to air pollutants may amplify risk for depression in healthy individuals. Light et al [13] measured pleural fluid pH in patients, including 39 with heart failure.
Pleural fluid pH Of these, esophageal rupture is associated with the lowest pleural fluid pH, usually in the range of 5. Although as noted above some patients whose pleural effusion is caused by pneumonia and malignancy have a pleural fluid pH of 7. The significance of pleural fluid pH in pneumonia and malignancy warrants more detailed consideration. The second most common cause of pleural effusion after heart failure is pneumonia.
Three stages in the progression of PPE are recognized [16]. The first is the exudative stage, which begins around days after the first symptoms of pneumonia. This is characterized by a rapid outpouring of fluid into the pleural space.
In the absence of effective antibiotic treatment during the subsequent days this progresses to the second so-called fibrinopurulent stage in which bacteria gain access and multiply within the pleural space. Large numbers of neutrophils are recruited to the pleural space and fibrin forms due to the entry of intravascular clotting proteins to the pleural space. Pleural fluid, increasingly rich with bacteria and neutrophils, may become "loculated" within compartments of the pleural space formed by accumulating fibrin strands.
Effective treatment at this stage depends on draining the accumulating pleural fluid therapeutic thoracentesis. In the absence of such treatment there is progression over the following weeks to the final organizational or empyema stage, which is defined by frank pus within the pleural space and characterized by the growth of a thick fibrous peel over the visceral pleura that ultimately prevents lung expansion.
Surgical removal of the peel is necessary for survival. The metabolic activity of accumulating cells and bacteria within the pleural space causes a progressive fall in pleural fluid pH [17] as PPE progresses from the uncomplicated PPE of the exudative phase through the complicated PPE of the fibrinopurulent stage to empyema.
In a separate study, 22 patients with empyema had a mean pleural fluid pH of 6. The observation that the lowest pleural fluid pH is associated with the most advanced stage of PPE has led to the widespread use of pleural fluid pH to guide treatment. All PPE patients require antibiotic therapy, but as the disease progresses to the second fibrinopurulent stage it becomes increasingly necessary to remove drain the effusion. The choice of pH 7.
This study also demonstrated that pleural fluid pH was better able to predict the need for tube drainage than either pleural fluid LDH activity or glucose concentration. An exception to the general rule that pleural fluids are increasingly acidotic in cases of PPE occurs when the causative bacteria is one of the Proteus species. Only rarely a cause of PPE, these bacteria elaborate the enzyme urease that converts urea to ammonium, rendering pleural fluid markedly alkaline.
In these rare cases pleural fluid pH is diagnostically useful as few, if any, conditions are associated with pH greater than that of normal pleural fluid. However, it would clearly be inappropriate to use the 7.
Another problem that might confound the interpretation of pleural fluid pH in cases of PPE was highlighted by Maskell et al [24] who demonstrated that the pH of pleural fluid can vary between locules in some patients with complicated "loculated" PPE. Malignant disease is a common cause of pleural effusion. Except in the rare case of mesothelioma primary tumor of the pleural mesothelium , MPE is a consequence of metastatic spread of tumor cells from a primary site lungs, breast, etc.
Median survival following diagnosis of MPE is just 5 months although there is variation between cancer type; breast cancer, for example, is associated with much longer survival 13 months than lung cancers 2 months [26].
Palliative treatment for cancer patients with MPE includes therapeutic thoracentesis, but recurring MPE is treated by pleurodesis, a more invasive procedure in which the pleural space is first drained of all pleural fluid, then obliterated by inducing an inflammatory reaction that fuses parietal and visceral pleura.
Successful pleurodesis prevents the formation of pleural fluid, thereby providing permanent relief from the debilitating breathlessness associated with MPE. Pleural fluid pH has prognostic significance in cases of MPE that has proved useful in guiding treatment. Good et al [19] determined that the pH of pleural fluid recovered from 44 patients with MPE ranged from 7.
A number of studies [] have demonstrated that low pleural fluid pH This relative acidosis is assumed to be the result of the metabolic activity of an ever-growing tumor cell mass. In a retrospective study [26] of patients with MPE, pleural fluid pH ranged from 6. The observed correlation between pleural fluid pH and survival outlined above has led to the recommendation that pleural fluid pH measurement be used in selecting patients for pleurodesis. The value of pleural fluid pH in this context is given further credence by studies that have demonstrated that low pleural fluid pH is associated with increased risk of pleurodesis failure [29].
Some authorities [30] have suggested that pleurodesis should not be considered in those with a pleural fluid pH Despite widespread recommendation that pleural fluid pH should only be determined using a blood gas analyzer [20,21], two other methods, pH meter and pH indicator stick or litmus paper are commonly used. A recent survey conducted in North Carolina [32] revealed that of 11 hospital laboratories measuring pleural fluid pH, just two reported using blood gas analyzers; the rest used either pH indicator stick or more rarely pH meter.
The results of this survey are broadly consistent with two previous studies [33,34] that suggest that only a third of laboratories use blood gas analyzers. The evidence that pH meters, pH indicator sticks and litmus paper are insufficiently accurate for measuring pleural fluid pH is contained in a number of studies [33,35,36]. The reluctance of laboratorians to use blood gas analyzers is attributed in part to the fear that pleural fluids may block or damage electrodes because they may contain pus and fibrin clots.
There is no clinical indication for measuring the pH of pleural fluids that contain visible pus because all such effusions require draining, irrespective of the pH.
Collecting pleural fluid into heparin-containing syringes prevents clot formation [37]. There is no clearly defined standard method for the collection of pleural fluid for pH measurement.
A recent study [37] investigating preanalytical factors that might affect results suggests that pleural fluid should be collected anaerobically into a preheparinized blood gas syringe, ensuring that all air is expelled.
Care should be taken that the sample is not contaminated with even a trace of local anesthetic lidnocaine used to prepare the patient for thoracentesis. Analysis should not be delayed beyond an hour after collection. May contain information that is not supported by performance and intended use claims of Radiometer's products.
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