Ventilation-perfusion Studies Research Articles

A Technical Overview of Technegas as a Lung Ventilation Agent.

Technegas is a carbon-based nanoparticle developed in Australia in 1984 and has been in widespread clinical use, including SPECT imaging, since 1986. Although 81mKr offers the ideal ventilation properties of a true gas, Technegas is considered preferred in more than 60 countries for ventilation imaging yet has limited adoption in the United States. In March 2020, a new U.S. Food and Drug Administration application was lodged for Technegas, and the impending approval warrants a detailed discussion of the technical aspects of the technology for those for whom it is new. Technegas is a simple yet versatile system for producing high-quality 99mTc-based ventilation studies. The design affords safety to patients and staff, including consideration of radiation and biologic risks. Technegas is the gold standard for the ventilation portion of SPECT-based ventilation-perfusion studies in pulmonary embolism and several respiratory pathologies. When approved by the U.S. Food and Drug Administration, Technegas will extend advantages to workflow, safety, and study quality for departments that adopt the technology.

A narrative review of red blood cell distribution width as a marker for pulmonary embolism.

Red blood cell distribution width (RDW) is a marker of variability in red blood cell size, and is routinely reported as part of a patient's complete blood count. RDW has been shown to be associated with the prediction, severity and prognosis of pulmonary embolism (PE) in recent studies. The underlying biomolecular mechanism of the relationship of RDW to PE is largely unknown, but is thought to be due to the relationship of RDW with acute inflammatory markers and variations in blood viscosity. This review substantiates that a high RDW level, defined using either an arbitrary number or according to receiver operator curve statistics, is associated with a higher risk of acute PE, increased severity (massive vs. submassive) of PE and increased mortality in patients with PE. Nevertheless, the comparison of current studies is limited due to the definition of high RDW (each study uses a different RDW cutoff level), the broad range of exclusion criteria and the inclusion of differing modalities used to diagnose a PE (computed tomography angiogram, ventilation-perfusion study, or clinical diagnosis). Despite the above limitations, these studies provide a promising future clinical use for RDW as a marker of PE.

Ventilation-perfusion SPECT/CT in Diagnosing Swyer-James (MacLeod) Syndrome

We present the characteristics of a ventilation-perfusion scan correlating to both planar and single photon emission computed tomography and computed tomography (SPECT/CT) images of the lungs in a patient with Swyer-James (MacLeod) syndrome. A Tc-99m MAA lung perfusion scan was recorded with multiple projections and SPECT/CT. In the ventilation scan, initially dynamic acquisition of aerosol Tc-99m DTPA was obtained with an interval of 0.4 seconds per frame, followed by multiple static projections and SPECT/CT. Anatomically co-registered SPECT/CT of perfusion images demonstrated diffusely decreased perfusion without CT chest lesions over the affected radiolucent left lung. The SPECT/CT of ventilation scan showed heterogeneous radiotracer distribution and multiple defects resembling airflow obstruction over the left lung. A dynamic ventilation scan revealed diminished inhaled radioisotope in the left lung compared with the normal right lung. In contrast to over aeration of the left lung observed in the same area on CT, the dynamic hypoventilation implies the presence of air trapping. The SPECT/CT of ventilation-perfusion study showed matched defects in the left lung excluding a residual area of normal density, and permitted a specific reconstructive display to exhibit the pathophysiology of Swyer-James (MacLeod) syndrome with anatomic and functional co-registration.

Ventilation-Perfusion Scintigraphy in Children and Adolescents Is Associated With a Low Rate of Indeterminate Studies

In selected populations, ventilation-perfusion (V/Q) studies are nearly as accurate as CT angiography (CTA) for the diagnosis of pulmonary emboli (PE). This study was performed to determine the percentage of V/Q studies in children and adolescents that are indeterminate for the presence of PE. V/Q studies performed over a period of 2 years were reviewed. Studies from children and adolescents with chronic lung disease or recent documented severe PE were excluded. There were 37 V/Q studies and 3 perfusion only (Q) studies in 35 patients. Studies were evaluated using modified Biello criteria. Effective doses (EDs) for V/Q and CTA studies of the lung were calculated from administered activities and CT exposure parameters used. Eighteen studies were normal, 4 studies had a very low probability of PE, 6 were low probability, and 2 were high probability for PE. Four studies were negative for new PE when compared with a previous study. Five V/Q studies and 1 Q only study were indeterminate for PE (15%), only slightly higher than the reported percentage of indeterminate CTA in adults. ED from V/Q was about half the ED from CT angiography. Breast dose from V/Q was less than 3% of the breast dose from CT. In this selected group of children and adolescents, the percentage of indeterminate V/Q studies is low. V/Q has considerably lower absorbed breast and effective radiation doses than CTA, and is still appropriate for imaging children who are suspected of having PE.

Acute Pulmonary Thromboembolism: A Historical Perspective

639 diographic features of acute pulmonary thromboembolism are insensitive and nonspecific. The Westermark sign—oligemia of the lung beyond the occluded vessel—did not live up to early enthusiasm [10]. Similarly, elevation of the ipsilateral hemidiaphragm, enlargement of the proximal pulmonary artery, atelectasis, and pleural effusion are all nonspecific. The most common radiographic findings in the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study were atelectasis and patchy pulmonary opacity [11]. However, the prevalence of these findings in patients who did not have pulmonary thromboembolism was not significantly different. Radionuclide imaging (scintigraphy) became the mainstay of noninvasive imaging but had limitations. A normal ventilation–perfusion scan reliably excluded acute pulmonary thromboembolism, and a high-prob ability scan made this diagnosis with reasonable accuracy. However, a substantial proportion of ventilation–perfusion studies were nondiagnostic [12]. Over the years, the introduction of newer, safer, and quicker investigations has led to a progressive decrease in mortality from acute pulmonary thromboembolism [13]. In the early 1990s, the value of CT in the diagnosis of central pulmonary thromboembolism was documented by Remy-Jardin et al. [14]. CT was 90% sensitive and 96% specific for detection of central and lobar pulmonary thromboembolism, but segmental and subsegmental pulmonary thromboembolism was not assessed. In 1995, Goodman et al. [2] significantly advanced the field by comparing helical CT angiography (CTA) with pulmonary angiography in patients with unresolved suspicion for pulmonary thromboembolism and addressing the issue of segmental and subsegmental pulmonary thromboembolism. Acute Pulmonary Thromboembolism: A Historical Perspective

Guidelines for lung scintigraphy in children

The purpose of this set of guidelines is to help the nuclear medicine practitioner perform a good quality lung isotope scan. The indications for the test are summarised. The different radiopharmaceuticals used for the ventilation and the perfusion studies, the technique for their administration, the dosimetry, the acquisition of the images, the processing and the display of the images are discussed in detail. The issue of whether a perfusion-only lung scan is sufficient or whether a full ventilation-perfusion study is necessary is also addressed. The document contains a comprehensive list of references and some web site addresses which may be of further assistance.

Advances in Prostacyclin Therapy for Pulmonary Arterial Hypertension

Advances in Prostacyclin Therapy for Pulmonary Arterial Hypertension

Clinical oxygen-enhanced magnetic resonance imaging of the lung.

Oxygen-enhanced magnetic resonance (MR) ventilation imaging is a new technique, and the full extent of its physiologic significance has not been elucidated. This review article includes (1) theory of oxygen enhancement; (2) respiratory physiology; (3) oxygen-enhanced MR imaging (MRI) sequence design; (4) basic study of oxygen-enhanced MRI in animal models and humans; (5) clinical study of oxygen-enhanced MRI; and (6) merits and demerits of the technique in comparison with hyperpolarized noble gas MR ventilation imaging. Oxygen-enhanced MRI provides not only ventilation-related information but also respiration-related information. Although application of oxygen-enhanced MR ventilation imaging to patients with pulmonary diseases has been limited, oxygen-enhanced MRI offers the possibility of demonstrating regional pulmonary function and substituting for nuclear medicine ventilation-perfusion study, when combined with MR perfusion imaging. We believe that further basic studies and clinical applications of this new technique will define the real significance of oxygen-enhanced MR ventilation imaging in the future of pulmonary functional imaging and its usefulness for diagnostic radiology.

Functional MR imaging of pulmonary ventilation using hyperpolarized noble gases.

The current status of experimental and clinical applications for functional MR imaging of pulmonary ventilation using hyperpolarized noble gases are reviewed. 3-helium (3He) and 129-xenon (129Xe) can be hyperpolarized by optical pumping techniques such as spin exchange or metastability exchange in sufficient amounts. This process leads to an artificial, non-equilibrium increase of the density of excited nuclei which represents the source of the MR signal. Those hyperpolarized gases are administered mostly via inhalation, and will fill airways and airspaces allowing for ventilation imaging. Recent human studies concentrate on imaging the airways and airspaces with high spatial resolution. Normal ventilation is reflected by an almost complete and homogeneous distribution of the hyperpolarized gas represented by the signal detected. Loss of signal or inhomogeneous signal distribution represent mass effects and ventilatory abnormalities. Even healthy subjects with seasonal allergies without pulmonary symptoms have been observed to exhibit transient ventilation defects. Real-time imaging of ventilation has become feasible for 3He MR imaging and allows for assessment of ventilation-distribution. Furthermore, functional oxygen-sensitive 3He MR imaging opens the field of non-invasive assessment of regional intrapulmonary oxygen concentrations in vivo. Knowing that the diffusion of gas is affected by the geometry and nature of its environment, diffusion measurements are under investigation as a sensitive marker of diseases that involve structural changes of lung parenchyma, such as emphysema and fibrosis. Whereas 3He is not absorbed and is restricted to the airspaces, 129Xe is soluble in blood and lipid-rich tissue. This presents the opportunity for additional dissolved-phase imaging, providing a step towards simultaneous ventilation-perfusion studies.

24. Poor concordance of spiral CT (SCT) and high probability ventilation-perfusion (V/Q) studies in the diagnosis of pulmonary embolism (PE)

s: Abstracts of the 30th Annual Scientific Meeting of the Australian and New Zealand Society of Nuclear Medicine

Microbiological and radioactive contamination from radioaerosol ventilation scanning: is there a problem?

Radioaerosol lung imaging may result in (a) microbiological contamination of nebulizer circuits (a potential hazard to patients if the circuit is re-used), and (b) radioaerosol contamination of the atmosphere (a hazard to staff, particularly if inhaled, ingested or both). Altogether, 138 circuits were assessed for bacteriological contamination, 93 of which had been used for ventilation perfusion studies and 45 for lung permeability studies in human immunodeficiency virus (HIV) positive patients. The circuits used for ventilation/perfusion (V/Q) studies were re-used over a period of 1-5 days. The mouthpiece and Y-piece were changed between patients. The circuits used for permeability studies were changed in toto for each patient. Organisms belonging to normal respiratory flora were isolated from the Y-piece, mouthpiece or both in 9 of 138 cases. An additional case (from one of the HIV-positive patients) demonstrated a growth of methicillin-resistant Staphylococcus. We also demonstrated bacteriological growth, most likely of patient origin, in circuit tubing in 11 cases at the end of the first day's use and 9 cases by day 5. None of the circuits used for HIV-positive cases were culture-positive. Airborne radioactive contamination was assessed during radioaerosol inhalation with and without an air extractor device (Nederman) during 40 ventilation studies. The 20 studies with air extraction showed a large decrease in room air contamination. Nebulizer circuits can, and occasionally do, become contaminated with patients' organisms; this represents a potential infection control hazard and therefore re-use is contraindicated. The use of an air extractor will significantly reduce airborne radioaerosol contamination.

Mismatch on Tc-99m DTPA Aerosol Ventilation-Perfusion Lung Scan Caused by Achalasia

Tc-99m DTPA aerosol ventilation in conjunction with Tc99m MAA perfusion scintigraphy is widely used in the evaluation of pulmonary embolism. The authors describe a case that demonstrates the importance of comparing any ventilation-perfusion study to the chest radiograph and clinical history to accurately evaluate the probability of pulmonary emboli

Hypoxia and Cyanosis in Alpha-1-Antitrypsin Deficiency: Cirrhosis as an Unusual Etiologic Factor

A patient with type PiZZ α-1-antitrypsin deficiency was found to have severe hypoxia despite normal pulmonary function testing and a normal chest radiograph. A nuclear medicine ventilation-perfusion study revealed a right-to-left shunt. Computed tomography showed minimal bleb formation, no diffuse changes, and hepatic changes of cirrhosis with portal hypertension. No nodular pulmonary masses or enlarged peripheral pulmonary vessels were found. The diagnosis of diffuse intrapulmonic arteriovenous shunts (“pulmonary spiders of cirrhosis”) was suggested and then confirmed with a dynamic radionuclide flow study. A patient with type PiZZ α-1-antitrypsin deficiency was found to have severe hypoxia despite normal pulmonary function testing and a normal chest radiograph. A nuclear medicine ventilation-perfusion study revealed a right-to-left shunt. Computed tomography showed minimal bleb formation, no diffuse changes, and hepatic changes of cirrhosis with portal hypertension. No nodular pulmonary masses or enlarged peripheral pulmonary vessels were found. The diagnosis of diffuse intrapulmonic arteriovenous shunts (“pulmonary spiders of cirrhosis”) was suggested and then confirmed with a dynamic radionuclide flow study.

Multiple Coarctatlons of the Pulmonary Artery: Scintigraphic Appearance

A case of angiography-proven multiple coarctations of the pulmonary arteries is presented. The patient had a history of long-standing exertional dyspnea and intranasal cocaine use. A chest radiograph suggested oligemia in the left lung and enlargement of the right pulmonary artery, prompting ventilation and perfusion radionuclide lung imaging. The combined scintigraphic and radiographic findings were indistinguishable from those caused by pulmonary emboli. Although rare, this entity should be included in the differential diagnosis of multiple unmatched perfusion defects on pulmonary ventilation-perfusion studies.

Clinical features and history of the destructive lung disease associated with alpha-1-antitrypsin deficiency of adults with pulmonary symptoms.

Alpha-1-antitrypsin (alpha 1AT) deficiency is a hereditary disorder characterized in adults by a high risk for the development of severe destructive lung disease at an early age. The present study was designed to draw conclusions concerning the characteristics of a referral population of 124 patients with alpha 1AT deficiency and symptomatic emphysema. Typically, the alpha 1AT level was 30 mg/dl, and the alpha 1AT phenotype was almost always PiZZ. The individuals in this population were most often male, caucasian, and ex-smokers, and they had become dyspneic between 25 and 40 yr of age. Most routine blood tests were normal. The chest radiographs and ventilation-perfusion studies typically showed abnormalities with a lower zone distribution, and about one third of the study population had evidence suggestive of pulmonary hypertension. Lung function tests were typical for emphysema; the FEV1 and DLCO were the parameters most dramatically reduced, and the annual rate of decline of those parameters was greater than that of the general population. The cumulative probability of survival of this population indicated a significantly shortened lifespan with a mean survival of 16% at 60 yr of age compared with 85% for normal persons.

けい肺症(I型, II型)における<sup>133</sup>Xe-換気,血流シンチグラフィーの検討

けい肺症(I型, II型)における<sup>133</sup>Xe-換気,血流シンチグラフィーの検討

Lung Scintigraphy

Our statement that “the approach of ruling against pulmonary embolism by a ‘low probability’ scan pattern is incorrect” stands. In his letter, Dr. Silberstein failed to provide the conclusions of Biello et al; 1 Biello DR Mattar AG McKnight RC Siegel BA Ventilation-perfusion studies in suspected pulmonary embolism. AJR. 1979; 133: 1033-1037 Crossref PubMed Scopus (273) Google Scholar based on the findings of their retrospective study, Biello and colleagues conclude, “Matched V-Q abnormalities in lung regions that were radiographically normal were infrequently due to PE (4.8 percent),” and they state further, “Earlier studies have shown that perfusion defects that correspond to areas of abnormal ventilation are infrequently due to pulmonary embolism.” Our prospective study refutes this conclusion. In performing the prospective comparison of ventilation perfusion lung scanning and pulmonary angiography, we took special care to avoid bias in both performing the protocol and evaluating the test findings. Because of their retrospective nature, the previous studies were unable to avoid potentially serious error due to bias. 2 Ransohoff DF Feinstein AR Problems of spectrum and bias in evaluating the efficacy of diagnostic tests. N Engl J Med. 1978; 299: 926-930 Crossref PubMed Scopus (1316) Google Scholar , 3 Sacket DL Bias in analytic research. J Chron Dis. 1979; 32: 51-63 Abstract Full Text PDF PubMed Scopus (1632) Google Scholar Indeed, Dr. Biello and colleagues state:

Diagnosis of pulmonary embolism

The clinical diagnosis of pulmonary embolism is highly nonspecific because none of the symptoms or signs of pulmonary embolism is unique and all may be caused by other cardiorespiratory disorders. Thus, objective testing is mandatory to either confirm or exclude a diagnosis of pulmonary embolism. Based on current available information, a diagnostic approach for the management of clinically suspected pulmonary embolism is proposed. After a history and physical examination, electrocardiogram and chest X-ray film, all patients should undergo perfusion lung scanning. The finding of a normal perfusion lung scan rules out clinically significant pulmonary embolism, and anticoagulant therapy is withheld. The management of patients with an abnormal perfusion lung scan is more complex. If this scan demonstrates one or more segmental (or greater) perfusion defects, ventilation lung scanning should be performed because the probability of pulmonary embolism is markedly increased if a mismatch is found, with a high probability scan (positive predictive value 86%) providing an end point for commencing anticoagulant therapy in the majority of patients. In an abnormal ventilation-perfusion study, the presence of a ventilation-perfusion match does not rule out the possibility of pulmonary embolism, and further objective testing is required in these patients with nonhigh probability scans. Similarly, in patients with small perfusion defects (one or more subsegmental defects) or indeterminate lung scan findings (in which the perfusion scan defects correspond to a defect on a chest X-ray film), the predictive values obtained from these ventilation-perfusion scan patterns are not sufficiently high or low to confirm or exclude the presence of pulmonary embolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary thromboembolism: Current status report on the role of nuclear medicine

The normal perfusion study continues indisputably to rule out the presence of pulmonary embolism (PE) with reasonable certainty. However, the abnormal perfusion study requires additional specificity. Many retrospective and one prospective correlation of contrast pulmonary angiography (CPA) have largely substantiated the efficacy of ventilation imaging and increasing specificity, especially with a high-probability (HP) interpretation to approximately a 90% predictive value. In most studies, the predictive value of a low-probability (LP) interpretation also approaches 90%. Intermediate-probability (IP) ventilation-perfusion (V-P) studies are the most frequent reason for performing pulmonary angiography, although LP studies with a stated prior clinical HP should also have CPA. Ventilation imaging technique is not as uniformly established as for perfusion studies, leading to some continued variability in interpretative criteria; yet criteria proposed by Biello and his colleagues have begun to be widely adopted. Aerosol inhalation imaging is developing, but has not been widely used, while problems continue with central airways deposition. The importance of contemporary correlative chest x-rays (CXR) especially when normal, have been emphasized, as well as new findings of the import of serial post-V-P CXRs, especially in HP studies without CPA or negative CPA. CPA continues to be the most specific diagnostic test for PE when properly performed, and is complimented and enhanced by use of prior V-P findings; although it is clear that too few CPAs are being performed. Consequently, there has been too much clinical dependence on V-P imaging. The value of prospective clinical probability estimates in patient management has been better substantiated. Reemphasis on thromboembolism as a systemic disease with use of some objective evaluation of the presence of peripheral thrombosis is becoming a part of clinical rationale, with the integrated long-leg radionuclide venograms (RNV) being one of the reasonable approaches. Multicenter studies have demonstrated, contrary to prior contentions, that V-P imaging leads to a significant net reduction and use of anticoagulants, as well as having overall significant efficacy in effecting patient management in suspected PE. Some of the controversies surrounding V-P imaging are expected to be resolved with the completion of the ongoing multiinstitute Prospective Investigation of Pulmonary Embolic Diagnosis (PIOPED) study.(ABSTRACT TRUNCATED AT 400 WORDS)

The Diagnosis of Clinically Suspected Pulmonary Embolism: Practical Approaches

Pulmonary embolism is a common complication of venous thrombosis that usually originates in the deep veins of the legs. It is now well recognized that the clinical diagnosis of pulmonary embolism is highly nonspecific. 1 Urokinase Pulmonary Embolism TrialA national co-operative study. Circulation. 1973; 47: 1-108 Google Scholar , 2 Hull R Hirsh J Carter C et al. Pulmonary angiography, ventilation lung scanning, and venography for clinically suspected pulmonary embolism with abnormal perfusion lung scan. Ann Intern Med. 1983; 98: 891-899 Crossref PubMed Scopus (563) Google Scholar , 3 McNeil BJ Ventilation-perfusion studies and the diagnosis of pulmonary embolism: concise communication. J Nucl Med. 1980; 21: 319-323 PubMed Google Scholar , 4 Biello DR Mattar AC McKnight RC et al. Ventilation perfusion studies in suspected pulmonary embolism. Am J Radiol. 1979; 133: 1033-1037 Google Scholar , 5 Bell WR Simon TL Demets DL The clinical features of submassive and massive pulmonary emboli. Am J Med. 1977; 62: 355-360 Abstract Full Text PDF PubMed Scopus (212) Google Scholar , 6 Bell WR Simon TL A comparative analysis of pulmonary perfusion scans with pulmonary angiograms: from a national cooperative study. Am Heart J. 1976; 92: 700-706 Abstract Full Text PDF PubMed Scopus (82) Google Scholar , 7 Szucs MM Brooks HL Grossman W et al. Diagnostic sensitivity of laboratory findings in acute pulmonary embolism. Ann Intern Med. 1971; 74: 161-166 Crossref PubMed Scopus (129) Google Scholar Clinical diagnosis is nonspecific because none of the symptoms or signs of pulmonary embolism is unique, and all may be caused by a variety of other cardiorespiratory disorders. The common symptoms and signs of pulmonary embolism and the associated differential diagnoses are listed in Table 1. The nonspecificity of the clinical diagnosis of pulmonary embolism was strikingly demonstrated in the Urokinase/Streptokinase Pulmonary Embolism Study (UPET) in which more than 60% of over 2,500 patients entered with clinically suspected pulmonary embolism had this diagnosis excluded by the finding of a negative perfusion lung scan. 1 Urokinase Pulmonary Embolism TrialA national co-operative study. Circulation. 1973; 47: 1-108 Google Scholar , 5 Bell WR Simon TL Demets DL The clinical features of submassive and massive pulmonary emboli. Am J Med. 1977; 62: 355-360 Abstract Full Text PDF PubMed Scopus (212) Google Scholar , 6 Bell WR Simon TL A comparative analysis of pulmonary perfusion scans with pulmonary angiograms: from a national cooperative study. Am Heart J. 1976; 92: 700-706 Abstract Full Text PDF PubMed Scopus (82) Google Scholar The results of the UPET study are consistent with the findings of other studies, 2 Hull R Hirsh J Carter C et al. Pulmonary angiography, ventilation lung scanning, and venography for clinically suspected pulmonary embolism with abnormal perfusion lung scan. Ann Intern Med. 1983; 98: 891-899 Crossref PubMed Scopus (563) Google Scholar , 3 McNeil BJ Ventilation-perfusion studies and the diagnosis of pulmonary embolism: concise communication. J Nucl Med. 1980; 21: 319-323 PubMed Google Scholar , 4 Biello DR Mattar AC McKnight RC et al. Ventilation perfusion studies in suspected pulmonary embolism. Am J Radiol. 1979; 133: 1033-1037 Google Scholar , 7 Szucs MM Brooks HL Grossman W et al. Diagnostic sensitivity of laboratory findings in acute pulmonary embolism. Ann Intern Med. 1971; 74: 161-166 Crossref PubMed Scopus (129) Google Scholar all of which indicate that more than half of all patients with clinically suspected pulmonary embolism do not have this diagnosis confirmed by objective testing. Thus, objective testing is mandatory either to confirm or to exclude a diagnosis of pulmonary embolism. Table 1Differential Diagnosis of the Clinical Features of Pulmonary Embolism Dyspnea Atelectasis Pneumothorax Acute pulmonary edema Acute bronchitis Acute bronchiolitis Acute bronchial obstruction Hemoptysis Pneumonia Bronchial neoplasm Bronchiectasis Acute bronchitis Mitral stenosis Tuberculosis Acute right heart failure Myocardial infarction Myocarditis Cardiac tamponade Acute respiratory infection complicating chronic lung disease Pleuritic chest pain Pneumonia Pneumothorax Pericarditis Pulmonary neoplasm Bronchiectasis Subdiaphragmatic inflammation Myositis Muscle strain Rib fracture Cardiovascuiar collapse Myocardial infarction Acute massive hemorrhage Gram-negative septicemia Cardiac tamponade Spontaneous pneumothorax Open table in a new tab