Why does tension pneumothorax cause hypotension

Doctors diagnose tension pneumothorax based on the person's history, symptoms, and examination results. For example, one side of the chest may bulge be distended , and doctors may hear a hollow sound when they tap it.

When they listen to the chest with a stethoscope, they may not hear any air flowing to the lung. Because tension pneumothorax is an emergency, doctors begin treatment immediately rather than doing tests. Doctors immediately insert a large needle into the pleural space to remove the air called needle decompression. Then a chest thoracostomy Chest Tube Insertion Chest tube insertion also called tube thoracostomy is a procedure in which a tube is inserted into the space between the lung and chest wall called the pleural space.

The procedure is done Usually local anesthesia is used. Merck and Co. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world. The Manual was first published in as a service to the community. Learn more about our commitment to Global Medical Knowledge. This site complies with the HONcode standard for trustworthy health information: verify here. Common Health Topics.

Chest Injuries. Test your knowledge. Motion sickness includes symptoms, particularly nausea, that affect people while they ride in a moving object. The object can be a transport vehicle such as a car, boat, train, or airplane, or an amusement park ride. A contributing factor is over-stimulation of a part of the body involved in balance control. Which of the following is that body part? More Content. Tension Pneumothorax By Thomas G. Click here for the Professional Version.

Moreover, possibly because waiting for a chest radiograph has been associated with an increased risk of death among mechanically ventilated patients [ 11 ], most authorities recommend emergent treatment with needle or tube thoracostomy before radiographic confirmation when the condition is first suspected [ 1 , 7 , 10 , 12 — 16 ].

Thus, prehospital providers and physicians utilize classically described clinical manifestations to diagnose tension pneumothorax. These have most frequently been reported to include hemodynamic compromise hypotension or cardiac arrest in conjunction with signs suggestive of a pneumothorax hypoxia, respiratory distress, absent unilateral breath sounds on auscultation and mediastinal shift tracheal deviation and jugular venous distention [ 7 , 17 ].

Unfortunately, although tension pneumothorax is commonly considered to be a clinical diagnosis, available textbooks, narrative review articles, and guidelines differ in their descriptions of its clinical manifestations [ 1 , 7 , 12 — 15 ].

This finding is concerning as delayed or even missed diagnoses have been reported among patients lacking classically described findings of the disorder [ 7 , 18 , 19 ]. Moreover, possibly because the clinical manifestations of tension pneumothorax have never been systematically reviewed, many sources appear to have derived their descriptions of the signs and symptoms of the disorder from the pathophysiologic processes observed in original canine models of the disorder [ 17 , 20 , 21 ].

Although commonly described among the medical literature, the generalizability of the above pathophysiologic mechanisms to humans is challenged by anatomical differences between dogs and humans [ 17 , 21 ]. Instead of being rigid and relatively fixed, the mediastinum of dogs is compliant and does not tolerate development of a pressure gradient between contralateral pleural spaces [ 17 , 21 ].

Thus, subsequent models of tension pneumothorax that utilized animals with a mediastinum similar to that of an adult human goats, pigs, and sheep demonstrated markedly different pathological mechanisms of the disease, which appeared to vary according to the respiratory status and possibly the level of alertness or consciousness of the animal [ 7 , 17 , 22 , 23 ].

Most importantly, these studies demonstrated that because awake or lightly sedated and spontaneously breathing animals utilize a number of compensatory mechanisms during evolution of a tension pneumothorax, they may be relatively protected from development of hypotension until the pre-terminal stages of the disorder [ 17 , 22 ]. These compensatory mechanisms, which may also occur among awake and spontaneously breathing humans, include a progressive tachycardia, an increasing respiratory rate and tidal volume, and increasingly negative contralateral chest excursions [ 7 , 17 , 22 ].

Thus, studies of lightly sedated, spontaneously breathing goats and sheep observed the pathophysiology of tension pneumothorax to involve progressive atelectasis resulting in pulmonary arterial shunting, worsening respiratory failure, and death from progressive hypoxemia rather than cardiovascular causes [ 17 , 22 ]. Interestingly, some authors have recently highlighted that a number of observational studies and case reports and series now exist that appear to suggest that adults with a tension pneumothorax who are breathing unassisted that is, breathing spontaneously and not receiving positive pressure ventilation often develop respiratory symptoms and signs without hemodynamic compromise [ 7 ].

These authors and others have also outlined several additional differences that may have clinical importance for the recognition and subsequent treatment of the disorder. First, rather than the initial development of cardiac arrest among those with a tension pneumothorax, these authors suggest that patients who are breathing unassisted may more frequently first develop respiratory arrest, possibly due to respiratory center depression as a result of hypoxemia [ 25 ].

Second, while hemodynamic decompensation or cardiac arrest may develop within minutes of pneumothorax onset among patients who are receiving positive pressure ventilation as has been classically described for this condition , these authors have also suggested that respiratory arrest may not occur for hours to days among those who are breathing unassisted [ 7 , 26 , 27 ]. If supported by available evidence, these differences could suggest that diagnosis of tension pneumothorax in patients who are breathing unassisted may more appropriately be based on respiratory clinical manifestations, and that earlier diagnosis and more appropriate treatment among these patients may result in improved patient outcomes.

An overview of the hypothesized differences in clinical manifestations of tension pneumothorax according to the presenting respiratory status of the patient that have been suggested based largely on animal study data are presented in Table 1.

While the above suggested differences in clinical manifestations among patients with a tension pneumothorax may have clinical importance, they remain largely based on narrative or non-systematic syntheses of the available clinical data and therefore could be accounted for by selection bias [ 1 , 7 ].

To our knowledge, only six non-systematic or narrative reviews on tension pneumothorax have been published between the years and [ 1 , 7 , 13 , 14 , 28 , 29 ], and only two of these [ 1 , 7 ] suggested that the clinical manifestations of tension pneumothorax may differ according to the respiratory status of the patient.

The absence of a systematic review on this topic may relate to the perceived lack of relevant observational data given that tension pneumothorax is difficult to study given that it presents acutely, is relatively uncommon and life-threatening, and requires immediate treatment.

Observational studies of patients receiving positive-pressure ventilation are likely particularly difficult to conduct as mechanically ventilated patients have been reported to manifest hemodynamic instability within minutes of an observed change in clinical status [ 30 — 35 ]. Likely as a result of these difficulties, although several retrospective observational studies exist that report data on the clinical manifestations of tension pneumothorax [ 4 , 11 , 36 — 41 ], the majority of original information on this topic is contained in published case reports and small case series.

In our initial scout or feasibility searches that were conducted during preparation of this systematic review protocol, we identified over case reports or small case series describing the clinical presentation of patients with a tension pneumothorax.

As tension pneumothorax is frequently a difficult clinical diagnosis encountered in emergent situations [ 42 ], the primary objective of this systematic review and meta-analysis is to utilize the existing world literature including that from published case reports and series on tension pneumothorax to describe and contrast the clinical manifestations of the disorder among patients receiving positive pressure ventilation versus those who are breathing unassisted.

A secondary objective is to determine if a difference exists in the time to arrest or requirement for thoracic decompression between these two groups. The study protocol described herein will demonstrate methods for a systematic review and meta-analysis of clinical manifestations data that could potentially be used in future studies to better characterize the signs and symptoms observed among patients with an uncommon, rare, or acutely life-threatening condition.

Ultimately, results of this work will provide the first systematic description of all currently available, published data on the clinical manifestations of tension pneumothorax.

These data will be used to better inform health care providers and therefore may contribute to an improved understanding of the appropriate clinical diagnosis and treatment of this life-threatening condition. Methods for the inclusion and analysis of articles have been developed according to recommendations from the Meta-analysis of Observational Studies in Epidemiology proposal [ 43 ], the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement [ 44 ], and the Cochrane Collaboration [ 45 ].

We will also query PubMed. Authors of articles will be contacted for additional information as necessary. Searches will be updated to within three months of submission of the results of the systematic review for peer review.

A similar electronic search strategy will be used to investigate all remaining databases see Table 2 for a detailed description of our database search strategies. Independently and in duplicate, two investigators DR, CB will screen citation titles and abstracts and review potentially relevant articles in full.

We will consider published observational cohort, case—control, and cross-sectional studies and case reports and series that report original data on clinical manifestations of tension pneumothorax for inclusion in the systematic review.

Reports of fatal cases will be included if the condition causing death was attributed by the study authors to be a tension pneumothorax and associated with expulsion of air following thoracic decompression or determined by a pathologist to be present on autopsy. As tension pneumothorax is a syndrome diagnosis without an independent reference-standard diagnostic test [ 10 , 16 , 40 ], any systematic review of its clinical manifestations may be limited by incorporation bias whereby the estimation of the frequency of clinical manifestations that may have been incorporated into the diagnosis may bias upward the results [ 46 ].

To reduce the risk of this bias, two investigators DR, CB will independently determine whether the clinical condition of the study patient s presented in each case report aligned with a previously published tension pneumothorax working definition [ 7 , 47 ].

All of the above excluded conditions were selected as they represent special, uncommon, or less relevant associated or principal patient conditions, which have the potential to misrepresent the more common clinical manifestations of tension pneumothorax. Disagreements between investigators regarding the above decisions will be resolved by consensus and, if needed, arbitration by a third investigator.

Independently and in duplicate, two investigators DR, CB will extract data using a pre-designed electronic spreadsheet. Data extracted from individual articles will include:. Study characteristics, including year of publication, country of conduct, and design. The design of the included studies for example, case—control versus cohort will be classified using the scheme developed by Oleckno [ 49 ].

As it may sometimes be difficult to distinguish between cohort studies and case series, a cohort study will be defined according to the definition proposed by Dekkers as a study in which patients are sampled based on exposure and the occurrence of outcomes was assessed as an aggregate measure during a follow-up period [ 50 ]. Characteristics of the study participants, including the number enrolled as well as their age and gender, pneumothorax etiology as suggested by the authors or through consensus between investigators , and ventilation status that is, whether they were receiving positive pressure ventilation or were breathing unassisted , as well as whether a definition of tension pneumothorax was provided and how this condition was specifically defined.

We will define positive pressure ventilation as either invasive for example, via an endotracheal tube and mechanical ventilator or non-invasive for example, bag-valve-mask ventilation. Mechanical ventilator settings will also be collected where available. We will also record the first reported type of cardiac arrest rhythm and the approximate time to cardiac or respiratory arrest or requirement for thoracic decompression where available.

Finally, we will extract values for respiratory and heart rates; systolic, diastolic, and mean arterial blood pressures; and SpO 2 or PaO 2 as well as the accompanying fraction of inspired oxygen FIO 2 that the patient was receiving at baseline that is, before any change in clinical status and before and after thoracic decompression where possible. Whether the following ipsilateral and contralateral chest signs were present before and after thoracic decompression: percussion hyper-resonance, decreased air entry, thoracic hyper- or hypo-expansion, chest wall hyper- or hypo-mobility, and contralateral tracheal deviation [ 1 , 7 ].

The initial and subsequent method of thoracic decompression for treatment of tension pneumothorax needle or tube thoracostomy or another method and whether these were effective. The same two investigators DR, CB will determine risk of bias among the included studies. We will also describe the temporality prospective versus retrospective of the included cohort studies as well as whether their patient enrollment method was consecutive versus non-consecutive.

Case reports and series will be evaluated as to whether authors provided absolute numbers rather than narrative or subjective descriptions when reporting the presence or absence of hypotension among patients with a tension pneumothorax [ 52 , 53 ]. Disagreements in methodological assessments will be resolved by consensus or arbitration by a third investigator HS.

An overview of the planned data synthesis strategy is presented in Figure 1. We will first conduct a narrative synthesis of the systematic review results [ 54 , 55 ]. Where appropriate, this will be followed by a meta-analysis of observational studies and then a separate meta-analysis of case reports and series.

Overview of the planned strategy for synthesis of data on the clinical manifestations of tension pneumothorax among observational studies and case reports and series. All clinical manifestations reported among observational studies of patients with a tension pneumothorax who were receiving positive pressure ventilation will be compared to those reported for patients breathing unassisted either indirectly if only non-comparative studies of patients with one versus another type of ventilation status were available or directly if patients with both types of ventilation status existed within studies.

This will be done qualitatively and, where possible, quantitatively through use of meta-analysis. Subsequently, summary statistics will be calculated describing the frequency of clinical manifestations reported among case reports and series of patients with a tension pneumothorax stratified by patient ventilatory status. Finally, a meta-analysis of the data reported by case reports and series will be conducted in order to examine whether differences exist in clinical manifestations, including decreases in arterial blood pressures or lower presenting arterial blood pressure values, hypotension, and cardiac arrest, among patients receiving positive pressure ventilation versus those who were breathing unassisted.

After studies have been appropriately grouped, the principal characteristics of the observational studies including their design that is, cohort, case—control, or cross-sectional , year of publication, setting, and a description of the clinical manifestations of the included patients stratified by ventilation status will be presented in one or more summary tables before any statistical combination of their results is contemplated.

Similarly, for case reports and series, the details of the reported patients, including their baseline characteristics for example, age, gender, and the etiology of their pneumothorax ; whether two investigators independently agreed that the diagnosis satisfied the tension pneumothorax working definition; potential confounding conditions or treatments; and clinical, radiological, and invasive hemodynamic or respiratory clinical manifestations will first be presented in summary tables stratified by ventilatory status before any meta-analyses are conducted.

We will also present the reported times to cardiac or respiratory arrest or, where these are unavailable, the time to requirement for thoracic decompression among patients according to their ventilatory status. Stata MP version We will begin our observational study data meta-analysis by calculating individual study estimates of the occurrence rate [ 56 ] of clinical manifestations among patients receiving positive pressure ventilation versus those that are breathing unassisted.

The occurrence rate will be defined according to Feinstein [ 56 ] using the following formula:. Among studies with a similar design involving patient populations with similar baseline characteristics, individual study estimates of the occurrence rate of clinical manifestations will be pooled separately stratified by patient ventilatory status.

Where possible, we will also determine a pooled estimate of the weighted or standardized mean difference in continuously measured clinical manifestations such as systolic or mean arterial pressures between these two patient populations or the difference in these values between baseline and presentation, where available [ 58 ]. As variability in our pooled estimates beyond chance is expected across studies, these estimates will be calculated using random effects models according to the method proposed by DerSimonian and Laird [ 58 , 59 ].

Although we believe that it would be unlikely that any of the available observational studies will report adjusted odds or risk ratios relating the frequency of occurrence of clinical manifestations between patients receiving positive pressure ventilation versus those breathing unassisted, where available these will also be pooled using random effects models [ 59 ]. Normally distributed data will be summarized using means with standard deviations and compared using t-tests with an unequal variance option where appropriate while skewed data will be summarized using medians with interquartile ranges and compared using Mann—Whitney U-tests.

As stepwise regression procedures [ 62 ] may result in biased estimated coefficients and optimistic fits especially with small sample sizes , our analyses will test the a priori hypothesis that patients who are receiving positive pressure ventilation have a higher reported risk of adverse hemodynamic complications.

We will also examine whether these reported complications may be confounded or modified by patient age, administration of antihypertensive or vasopressor medications before the onset of tension pneumothorax or chronic use of antihypertensives ; past history of hypertension, heart failure, or chronic pulmonary disease; and presence of a hemothorax or other pleural effusion, acute pulmonary disease for example, pulmonary contusions , or pre-existing shock. Although we will also test whether differences exist in the reported risk of other clinical manifestations between patients of varying respiratory status, these analyses will be largely exploratory and more susceptible to type I error.

As the reported clinical manifestations of patients with a tension pneumothorax may be clustered within hospitals or treatment locations and are expected to occur relatively commonly, all dichotomous associations will be examined using generalized estimating equations with a log link, a binomial distributional family, and an independent within-group correlation structure [ 63 ]. These equations are a valid method for the analysis of common outcomes among correlated data, and can be used to adjust for the influence of data clustering when fitting multivariable binomial, logistic, and linear regression models [ 63 ].

Potential modifying or confounding variables included in the regression models will include those described above. If these models are unable to converge as may occur when modeling the risk of an outcome , we will attempt to model the log of the odds using clustered logistic regression [ 63 ].

Finally, any potential differences in presenting systolic, diastolic, or mean arterial blood pressures or differences in presenting systolic, diastolic, or mean arterial blood pressures from baseline will be examined using generalized estimating equations with an identity link, a Gaussian distributional family, and a similar modeling strategy.

In order to determine the robustness of our findings, we will also conduct a series of sensitivity analyses, which will be reported alongside our principal results upon submission of the study findings for peer review. First, we will assess whether our observed associations are sensitive to incorporation bias or the classification of tension pneumothorax.

After conducting analyses using the data extracted from all reported cases, this will be done by recalculating all outcomes using only those cases where two investigators independently agreed that the clinical condition of the study patient s aligned with the tension pneumothorax working definition described above [ 7 , 47 ].

Outcomes will also be recalculated using only those case reports and series where study authors gave absolute numbers rather than narrative or subjective descriptions when reporting the presence or absence of hypotension.

Multiple imputation is a method that may be used to perform a series of imputations for each missing observation by conducting random draws from the conditional distribution of the outcome variable given the values of the other variables [ 64 ].

After performing these imputations, regression analyses will then be conducted on each of the imputed data sets. The estimated associations and standard errors obtained from these analyses will then be combined to obtain point estimates and standard errors that account for the missing information.

Simple imputation will then be used in order to provide an estimate of the extremes of influence of the missing values on the estimated outcomes between groups. This study will provide the first systematic compilation of the world literature regarding the clinical manifestations of tension pneumothorax.

As delayed or even missed diagnoses may result in poor outcomes and have been reported among patients lacking classically-described clinical manifestations of the disorder [ 7 , 18 , 19 ], an evidence-informed description of the clinical manifestations of tension pneumothorax may allow for creation of a list of evidence-based criteria for its diagnosis. Further, if our results support the pathophysiologic differences observed among animal studies of tension pneumothorax, it may also allow for the creation of separate definitions for the condition according to the presenting respiratory status of the patient.

As delay in treatment of tension pneumothorax may adversely affect outcomes, and some clinicians may delay thoracic decompression among those suspected of having the condition as their hemodynamics are stable [ 65 ], this study could also potentially assist in identifying patients who may be appropriate candidates for treatment with needle or tube thoracostomy.

We also aim to demonstrate our methods for the conduct of a narrative synthesis of systematic review results alongside a meta-analysis of observational studies and then a separate meta-analysis of case reports and series where appropriate. Although methods for the systematic review and meta-analysis of case reports and series have not yet been fully developed, these have been suggested [ 66 , 67 ], and are reportedly scheduled to be discussed for use in assessing the risk of rare adverse medication events at the next International Congress on Peer Review and Biomedical Publication [ 68 ].

However, in addition to their potential role in assessing the association between medications and rare adverse events [ 69 , 70 ], systematic reviews of case reports and series have also been utilized to evaluate the type, frequency of use, and effectiveness and safety of surgical interventions for conditions infrequently encountered in clinical practice [ 71 , 72 ].

As few other methods of study are sometimes feasible, these types of systematic reviews are also increasingly being used to evaluate the clinical manifestations or prognosis of rare, unusual, or difficult-to-study conditions [ 73 — 75 ].

In this study, using a rationale similar to that used by many of the above authors, we chose to include case reports and series as tension pneumothorax is a condition infrequently encountered in clinical practice and therefore difficult to study using an observational design.

However, while the Cochrane Collaboration and the Evidence-based Practice Center Program recognizes the usefulness of systematic reviews of case reports in select instances, the Cochrane Collaboration also expresses that several considerations must be made before their use in assessing adverse medication events [ 45 , 68 ].

As no consensus definition for tension pneumothorax yet exists, it may be unclear as to the quality of the predictive value of the included case reports [ 45 ]. However, while it may be possible that we may somewhat over select for patients with less common etiologies of tension pneumothorax, we believe it would be less likely that their clinical manifestations would be substantially different than those with more common etiologies.

Further, as tension pneumothorax is an uncommon yet catastrophic clinical diagnosis, its occurrence may be more likely to be reported regardless of cause, resulting in numerous case reports of tension pneumothorax among patients with more common etiologies for example, central venous access punctures or lung disease. As was also suggested by the Cochrane Collaboration, an adverse event or in this case, clinical manifestation is more plausible when a biological mechanism exists linking it to an intervention or exposure [ 45 , 68 ].

We believe our work to align with this consideration, as there now exists a considerable amount of preclinical data in support of a difference in pathophysiology between animals receiving positive pressure ventilation versus those who are breathing unassisted [ 7 , 17 , 22 , 23 ]. Moreover, although not outlined by the report from the Cochrane Collaboration, any association between the risk of certain clinical manifestations and the ventilatory status of the patient could be due to the presence of confounding factors.

This outcome could also be influenced by the potential for clustering of clinical manifestations data in case series, a limitation that appears to have been relatively ignored by many previous meta-analyses of case reports and series data.

In an attempt to address these issues, we outlined those factors that we felt a priori would be most likely to confound our relationships, and will attempt to adjust for the influence of these variables, and for any influence of data clustering, in our analyses. This systematic review will compile the world literature on tension pneumothorax and provide the first systematic description of its associated clinical manifestations to clinicians and other end users.

As tension pneumothorax is frequently a difficult diagnosis that may be encountered in emergent situations [ 42 ], these data will be used to better inform health care providers on the clinical manifestations of the condition, and may contribute to an improved understanding of its appropriate definition, clinical diagnosis, and treatment. It will also demonstrate methods for the conduct of a narrative synthesis of systematic review results alongside a meta-analysis of observational studies and a meta-analysis of case reports and series.

Results are expected to be publicly available in DR is a surgery and Clinician Investigator Program resident who is currently conducting a Doctor of Philosophy degree at the University of Calgary with a specialization in epidemiology. SL-S works as an Emergency Physician in the United Kingdom and has an interest in the pathophysiology and clinical manifestations of tension pneumothorax.