Pressure-Dependent Pneumothorax and Air Leak: Physiology and Clinical Implications.

Pressure-dependent pneumothorax is a common clinical event, often occurring after pleural drainage in patients with visceral pleural restriction, partial lung resection, or lobar atelectasis from bronchoscopic lung volume reduction or an endobronchial obstruction. This type of pneumothorax and air leak is clinically inconsequential. Failure to appreciate the benign nature of such air leaks may result in unnecessary pleural procedures or prolonged hospital stay. This review suggests that identification of pressure-dependent pneumothorax is clinically important because the air leak that results is not related to a lung injury that requires repair but rather to a physiological consequence of a pressure gradient. A pressure-dependent pneumothorax occurs during pleural drainage in patients with lung-thoracic cavity shape/size mismatch. It is caused by an air leak related to a pressure gradient between the subpleural lung parenchyma and the pleural space. Pressure-dependent pneumothorax and air leak do not need any further pleural interventions.

Association between Drainage-Dependent Prolonged Air Leak after Partial Lung Resection and Clinical Outcomes: A Prospective Cohort Study.

Rationale: Prolonged air leak (PAL) after partial lung resection can occur owing to surgical complications or in the presence of residual thoracic space. The former type results in drainage-independent PAL (DIPAL), whereas the latter type results in drainage-dependent PAL (DDPAL). DDPAL is described after thoracentesis in patients with nonexpandable lung, where the thoracostomy tube can be discontinued safely despite an ongoing air leak. This distinction is clinically relevant, as in the presence of DDPAL, tube thoracostomy can be safely discontinued without the need for further interventions. Objectives: To determine the frequency and clinical relevance of DDAPL and DIPAL in patients with PAL after partial lung resection. Methods: We prospectively identified consecutive patients with PAL after partial lung resection. Pleural manometry was performed 3-5 days after surgery. Pleural pressure was measured for 20 minutes after clamping the thoracostomy tube. DDPAL was diagnosed if the end-expiratory pleural pressure remained stable after plateauing in the absence of respiratory symptoms. Results: Of 225 patients who underwent lung resection, we identified 22 (10%) who had PAL. Twenty patients had adequate pleural manometry readings. The majority, 16/20 (80%), had DDPAL and had lower median hospital length of stay than those with DIPAL (6.9 vs. 11 days; P = 0.02). All patients with DIPAL required reexploration surgery, whereas only one patient with DDPAL underwent reexploration surgery. Conclusions: Most PALs after partial lung resection are DDPAL. Patients with DDPAL have lower hospital length of stay and less need for reexploration surgery than those with DIPAL.

The Relationship of Pleural Manometry With Postthoracentesis Chest Radiographic Findings in Malignant Pleural Effusion.

BACKGROUND: Both elevated pleural elastance (E-PEL) and radiographic evidence of incomplete lung expansion following thoracentesis have been used to exclude patients with a malignant pleural effusion (MPE) from undergoing pleurodesis. This article reports on a cohort of patients with MPE in whom complete drainage was attempted with pleural manometry to determine the frequency of E-PEL and its relation with postthoracentesis radiographic findings. METHODS: Seventy consecutive patients with MPE who underwent therapeutic pleural drainage with pleural manometry were identified. The pressure/volume curves were constructed and analyzed to determine the frequency of E-PEL and the relation of PEL to the postthoracentesis chest radiographic findings. RESULTS: E-PEL and incomplete lung expansion were identified in 36 of 70 (51.4%) and 38 of 70 (54%) patients, respectively. Patients with normal PEL had an OR of 6.3 of having complete lung expansion compared with those with E-PEL (P = .0006). However, 20 of 70 (29%) patients exhibited discordance between postprocedural chest radiographic findings and the pleural manometry results. Among patients who achieved complete lung expansion on the postdrainage chest radiograph, 9 of 32 (28%) had an E-PEL. In addition, PEL was normal in 11 of 38 (34%) patients who had incomplete lung expansion as detected according to the postthoracentesis chest radiograph. CONCLUSIONS: E-PEL and incomplete lung expansion postthoracentesis are frequently observed in patients with MPE. Nearly one-third of the cohort exhibited discordance between the postprocedural chest radiographic findings and pleural manometry results. These findings suggest that a prospective randomized trial should be performed to compare both modalities (chest radiograph and pleural manometry) in predicting pleurodesis outcome.

Defining a Ventilation Strategy for Flexible Bronchoscopy on Mechanically Ventilated Patients in the Medical Intensive Care Unit.

BACKGROUND: Flexible bronchoscopy (FB) in intubated patients on mechanical ventilation increases airway resistance. During FB, two ventilatory strategies are possible: maintaining tidal volume (VT) while maintaining baseline CO2 or allowing reduction of VT. The former strategy carries risk of hyperinflation due to expiratory flow limitation with FB. The aim of the authors was too study end expiratory lung volume (EELV) during FB of intubated subjects while limiting VT. METHODS: We studied 16 subjects who were intubated on mechanical ventilation and required FB. Changes in EELV were measured by respiratory inductance plethysmography. Ventilator mechanics, EELV, and arterial blood gases, were measured. RESULTS: FB insertions decreased EELV in 64% of cases (-325±371 mL) and increased it in 32% of cases (65±59 mL). Suctioning decreased EELV in 76% of cases (-120±104 mL) and increased it in 16% of cases (29±33 mL). Respiratory mechanics were unchanged. Pre-FB and post-FB, PaO2 decreased by 61±96 mm Hg and PaCO2 increased by 15±7 mm Hg. CONCLUSIONS: There was no clinically significant increase in EELV in any subject during FB. Decreases in EELV coincided with FB-suctioning maneuvers. Peak pressure limiting ventilation protected the subject against hyperinflation with a consequent, well-tolerated reduction in VT, and hypercapnea. Suctioning should be limited, especially in patients vulnerable to derecruitment effect.

Management of Prolonged Pulmonary Air Leaks With Endobronchial Valve Placement.

BACKGROUND: Prolonged pulmonary air leaks (PALs) are associated with increased morbidity and extended hospital stay. We sought to investigate the role of bronchoscopic placement of 1-way valves in treating this condition. METHODS: We queried a prospectively maintained database of patients with PAL lasting more than 7 days at a tertiary medical center. Main outcome measures included duration of chest tube placement and hospital stay before and after valve deployment. RESULTS: Sixteen patients were eligible to be enrolled from September 2012 through December 2014. One patient refused to give consent, and in 4 patients, the source of air leak could not be identified with bronchoscopic balloon occlusion. Eleven patients (9 men; mean age, 65 ± 15 years) underwent bronchoscopic valve deployment. Eight patients had postoperative PAL and 3 had a secondary spontaneous pneumothorax. The mean duration of air leak before valve deployment was 16 ± 12 days, and the mean number of implanted valves was 1.9 (median, 2). Mean duration of hospital stay before and after valve deployment was 18 and 9 days, respectively (P = .03). Patients who had more than a 50% decrease in air leak on digital monitoring had the thoracostomy tube removed within 3-6 days. There were no procedural complications related to deployment or removal of the valves. CONCLUSIONS: Bronchoscopic placement of 1-way valves is a safe procedure that could help manage patients with prolonged PAL. A prospective randomized trial with cost-efficiency analysis is necessary to better define the role of this bronchoscopic intervention and demonstrate its effect on air leak duration.

Point-of-Care Echocardiography Improves Assessment of Volume Status in Cirrhosis and Hepatorenal Syndrome.

The management of patients with cirrhosis along with acute kidney injury is complex and depends in large part on accurate assessment of intravascular volume status. Assessment of intravascular volume status by point-of-care echocardiography often relies solely on inferior vena cava size and variability evaluation; however, this parameter should be interpretated with an understanding of right ventricular function integrated with stroke volume and flow. Attempts to optimize intra-abdominal hemodynamics favorably are clearly problematic when physical examination findings or rudimentary assessments of central venous pressure or change in central venous pressure are used. Here, we have demonstrated the potential utility of point-of-care echocardiography to optimize the hemodynamic state in patients with decompensated cirrhosis along with acute kidney injury. This case is very unique and describes how this technique may have great promise in optimizing the intra-abdominal hemodynamics and predict the timing of large-volume paracentesis in patients with decompensated cirrhosis, which in turn can aid in promoting favorable renal recovery.

Pleural Fluid Analysis in Chronic Hemothorax: A Mimicker of Infection.

OBJECTIVES: Timing to video-assisted thoracoscopic surgery (VATS) in hemothorax is based on preventing acute and long-term complications of retained blood products in the pleural space, including pleural space infection. We propose that the persistence of blood in the pleural space induces a proinflammatory state, independent of active infection. METHODS: We identified six patients with a hemothorax by clinical history, radiographic imaging, and pleural fluid analysis from a database of 1133 patients undergoing thoracentesis from 2002 to 2010 at the Medical University of South Carolina. RESULTS: In four of the six patients identified, the time from injury to thoracentesis was one, four, four, and five days, respectively. The fluid pH range was 7.32-7.41. The lactate dehydrogenase (LDH) range was 210-884 IU/L (mean 547 IU/L), and the absolute neutrophil count (ANC) range was 1196-3631 cells/µL. In two patients, the time from injury to thoracentesis was 7 and 60 days. In these two patients, the pH was 7.18 and 6.91, LDH was 1679 and 961 IU/L, and the ANC was 8134 and 5943 cells/µL. Microbiology and pathology were negative in all patients. CONCLUSIONS: The persistence of blood outside the vascular compartment, and within the pleural space, biochemically mirrors infection. We will explore the multiple mechanisms that account for development of pleural fluid acidosis, inflammation, and neutrophil recruitment.

Safety of Propofol as an Induction Agent for Urgent Endotracheal Intubation in the Medical Intensive Care Unit.

PURPOSE: Propofol is known to provide excellent intubation conditions without the use of neuromuscular blocking agents. However, propofol has adverse effects that may limit its use in the critically ill patients, particularly in the hemodynamically unstable patient. We report on the safety and efficacy of propofol for use as an agent for urgent endotracheal intubation (UEI) in the critically ill patients. METHODS: We reviewed the outcomes of 472 consecutive UEIs performed by a medical intensive care unit (ICU) team at a tertiary care hospital from November 2008 through November 2012. Outcome data were collected prospectively as part of an ongoing quality improvement project. RESULTS: Propofol was used as the sole sedative agent in 409 (87%) of the 472 patients. In 18 (4%) of the 472 patients, other agents (midazolam, lorazepam, or etomidate) were used in addition to propofol. Of the 472, 10 (2%) intubations were performed with a sedative agent other than propofol, and 35 (7%) of the 472 intubations were performed without any sedating agent. Endotracheal tube insertion was successful in all 472 patients. Complications of UEI in those patients who received propofol were as follows: desaturation (Sao 2 < 80%) 30 (7%) of the 427, hypotension (systolic blood pressure < 70 mm Hg) 19 (4%) of the 427, difficult intubation (>2 attempts) 44 (10%) of the 427, esophageal intubation 24 (6%) of the 427, aspiration 6 (1%) of the 427, and oropharyngeal injury 4 (1%) of the 427. There were no deaths. Average dose of propofol was 99 mg (standard deviation 7.39) per person. CONCLUSIONS: Our results compare favorably with the complication rate of UEI reported in the critical care and anesthesiology literature and indicate that propofol is a useful agent for airway management in the ICU.

Improving the predictive accuracy of identifying exudative effusions.

BACKGROUND: Application of Light's criteria results in misclassification of some transudative effusions as exudative, particularly because of congestive heart failure (CHF). We sought to determine if the serum to pleural fluid albumin (SF-A) and serum to pleural fluid protein (SF-P) gradients increased the predictive accuracy to correctly identify exudative effusions. METHODS: We retrospectively analyzed 1,153 consecutive patients who underwent a diagnostic thoracentesis at the Medical University South Carolina. Univariable logistic regression analyses were used to determine the statistical significance of pleural fluid tests that correctly identified exudative effusions. Tests with significant diagnostic accuracy were combined in multivariable logistic regression models, with calculation of areas under the curve (AUCs) to determine their predictive accuracy. The predictive capability of the best model was compared with Light's criteria and other test combinations. RESULTS: Pleural fluid lactate dehydrogenase (LDH), SF-A gradient, and SF-P gradient had a significant effect on the probability of identifying exudative pleural effusions. When combined together in a multivariable logistic regression, LDH (OR, 14.09 [95% CI, 2.25-85.50]), SF-A gradient (OR, 7.16 [95% CI, 1.24-41.43]), and SF-P gradient (OR, 6.83 [95% CI, 1.56-27.88]) had an AUC of 0.92 (95% CI, 0.85-0.98). CONCLUSIONS: Application of Light's criteria, not uncommonly, misclassifies CHF transudative effusions as exudates. In cases where no cause for an exudative effusion can be identified or CHF is suspected, the sequential application of the fluid LDH, followed by the SF-P and then the SF-A gradients, may assist in reclassifying pleural effusions as transudates.

Effects of coexisting pneumonia and end-stage renal disease on pleural fluid analysis in patients with hydrostatic pleural effusion.

BACKGROUND: In individual patients, especially those who are hospitalized, several conditions often coexist that may be responsible for the development of a pleural effusion and may affect the pleural fluid analysis (PFA). The objective of this study was to investigate the effects of end-stage renal disease and pneumonia on PFA in patients with hydrostatic pleural effusion. METHODS: In a retrospective analysis of 1,064 consecutive patients who underwent thoracentesis at a university hospital, cell counts and pleural fluid protein, lactate dehydrogenase, pH, and glucose levels were examined in those (n = 300) with clinical evidence of hydrostatic pleural effusion. RESULTS: The 300 patients (28.1%) with pleural effusions had congestive heart failure (CHF), circulatory overload (CO), or both. Expert consensus was achieved in 66 (22%) for CHF as the sole diagnosis (SCHF), 30 (10%) for CHF and coexisting pneumonia (PCHF), and 26 (8.7%) for end-stage renal disease (ESRD) with coexisting CO or CHF. The remaining 178 patients were excluded because of complicating conditions. There were minor, but statistically significant differences in pleural fluid/serum protein ratios in patients with ESRD with coexisting CO or CHF compared with SCHF. Compared with SCHF, there were statistically significant tendencies for higher protein and lactate dehydrogenase concentrations and lower pH levels in those with PCHF. The total nucleated cell count and the absolute neutrophil count were significantly higher in PCHF. CONCLUSIONS: ESRD in patients with hydrostatic pleural effusions has a minimal effect on the PFA. Coexisting pneumonia most often results in an exudative effusion in patients with CHF.

Validation of simulated difficult bag-mask ventilation as a training and evaluation method for first-year internal medicine house staff.

INTRODUCTION: The past decade has witnessed the increased use of patient simulation in medical training as a method to teach complex bedside skills. Although effective bag-mask ventilation (BMV) is a critical part of airway management, the quality of training in this skill has been questioned. METHODS: First-year internal medicine house staff (novices) were used to evaluate a computerized patient simulator as a tool to teach difficult BMV. A novice group and an expert group (certified registered nurse anesthetists and anesthesiologists) were tested to validate the simulator's ability to distinguish between these 2 skill levels. RESULTS: The difference between the novice and expert groups in the ability to perform difficult BMV was statistically significant (P < 0.0001). Brief training for novices led to a 100% pass rate and competence as measured by the simulator. Simulation training was effective in increasing the ability to ventilate a simulated difficult-to-ventilate patient (P < 0.0001). CONCLUSIONS: This study suggests that this computerized patient simulator was validated as a simulation model for teaching difficult BMV and differentiating skill levels in BMV. Using the simulator with brief training on difficult BMV allowed new internal medicine house staff to successfully ventilate a simulated difficult patient.

Intrapleural therapy.

Numerous intrapleural therapies have been adopted to treat a vast array of pleural diseases. The first intrapleural therapies proposed focused on the use of fibrinolytics and DNase to promote fluid drainage in empyema. Numerous case series and five randomized controlled trials have been published to determine the outcomes of fibrinolytics in empyema treatment. In the largest randomized trial, the use of streptokinase had no reduction in mortality, decortication rates or hospital days compared with placebo in the treatment of empyema. Criticism over study design and patient selection may have potentially affected the outcomes in this study. The development of dyspnoea is common in the setting of malignant pleural effusions. Pleural fluid evacuation followed by pleurodesis is often attempted. Numerous sclerosing agents have been studied, with talc emerging as the most effective agent. Small particle size of talc should be avoided because of increased systemic absorption potentiating toxicity, such as acute lung injury. Over the past several years, the use of chronic indwelling pleural catheters have emerged as the preferred modality in the treating a symptomatic malignant pleural effusion. For patients with malignant-related lung entrapment, pleurodesis often fails due to the presence of visceral pleural restriction; however, chronic indwelling pleural catheters are effective in palliation of dyspnoea. Finally, the use of staphylococcal superantigens has been proposed as a therapeutic model for the treatment of non-small lung cancer. Intrapleural instillation of staphylococcal superantigens increased median survival by 5 months in patients with non-small cell lung cancer with a malignant pleural effusion.

Pleural fluid analysis and radiographic, sonographic, and echocardiographic characteristics of hepatic hydrothorax.

BACKGROUND: There are limited published data defining complete pleural fluid analysis, echocardiographic characteristics, or the presence or absence of ascites on sonographic or CT imaging in patients with hepatic hydrothorax. METHODS: We reviewed pleural fluid analysis and radiographic, sonographic, and echocardiographic findings in 41 consecutive patients with hepatic hydrothorax referred to the Pleural Procedure Service for thoracentesis. RESULTS: Ascites was detected on sonographic or CT imaging in 38 of 39 patients (97%). Diastolic dysfunction was found in 11 of 21 patients (52%). Contrast echocardiography with agitated saline demonstrated an intrapulmonary shunt in 18 of 23 cases (78%). Solitary hepatic hydrothorax had a median pleural fluid pH of 7.49 (fifth to 95th percentile, 7.40-7.57), total protein level of 1.5 g/dL (0.58-2.34), and lactate dehydrogenase (LDH) level of 65 IU/L (36-138). The median pleural fluid/serum protein ratio and pleural LDH/upper limit of normal serum LDH ratio were 0.25 (0.10-0.43) and 0.27 (0.14-0.57), respectively. The median absolute neutrophil count (ANC) was 26 cells/µL (1-230). Only a single patient had a protein discordant exudate despite 83% of patients receiving diuretics. When comparing solitary hepatic hydrothorax and spontaneous bacterial pleuritis, there was no statistically significant difference among pleural fluid total protein (P = .99), LDH (P = .33), and serum albumin (P = .47). ANC was higher in patients with spontaneous bacterial pleuritis (P < .0001). CONCLUSIONS: Hepatic hydrothorax virtually always presents with ascites that is detectable on sonographic or CT imaging. The development of an "exudate" from diuretic therapy is a rare phenomenon in hepatic hydrothorax. In contrast, diastolic dysfunction and intrapulmonary shunting are common in patients with hepatic hydrothorax. There was no statistically significant change in pleural fluid parameters with spontaneous bacterial pleuritis, except an increased ANC.

A program to improve the quality of emergency endotracheal intubation.

OBJECTIVE: To assess the results of a quality improvement (QI) project designed to improve safety of emergency endotracheal intubation (EEI). DESIGN: Single center prospective observational. SETTING: 16-bed intensive care unit. PARTICIPANTS: Nine pulmonary/critical care fellows. INTERVENTIONS: For 3 years, EEI performed by the medical intensive care unit team were analyzed to identify interventions that would improve quality of the procedure. By segmental process analysis, the procedure of EEI was subjected to iterative change. Major components of process improvement were development of a combined team approach, a mandatory checklist, use of crew resource management (CRM) tactics, and postevent debriefing. Quality analysis and improvement included training of fellows using scenario-based training (SBT) with computerized patient simulator (CPS) to improve mechanical skills of intubation and team leadership. Fellows received 15 sessions of SBT with CPS using a combined checklist and team approach before assuming team leadership position during real-life EEI. MEASUREMENTS: For a 10-month period, fellows carried digital voice recorders to EEI; which, when combined with recording of continuous oximetry and BP monitoring were used to assess the quality of EEI. MAIN RESULTS: 128 EEI were performed of which 101 had full data recorded. Complications were 14% severe hypoxemia (<80% saturation), 6% severe hypotension (SBP<70 mm Hg), 1% death, 20% difficult EEI (≥ 3 attempts), 11% esophageal intubations, 2% aspiration, and 1% dental injury; 62% EEI were successfully achieved on first attempt, 11% required >3 attempts. CONCLUSIONS: EEI may be performed by pulmonary/critical medicine (PCCM) fellows with safety comparable to that described in other studies on EEI. Important parts of the program included the use of formal iterative QI approach, the use of intensive SBT with CPS, basic CRM, a comprehensive checklist, and a combined team approach. A key benefit of the program was to make the process of EEI fully transparent for ongoing quality and safety improvement.

The unexpandable lung.

Unexpandable lung is the inability of the lung to expand to the chest wall allowing for normal visceral and parietal pleural apposition. It is the direct result of either pleural disease, endobronchial obstruction resulting in lobar collapse, or chronic atelectasis. Unexpandable lung occurring as a consequence of active or remote pleural disease may present as a post-thoracentesis hydropneumothorax or an effusion that cannot be completely drained because of the development of anterior chest pain. Pleural manometry is useful for identifying unexpandable lung during initial pleural drainage. Unexpandable lung occurring as a consequence of active or remote pleural disease may be separated into two distinct clinical entities termed trapped lung and lung entrapment. Trapped lung is a diagnosis proper and is caused by the formation of a fibrous visceral pleural peel (in the absence of malignancy or active pleural inflammation). The mechanical effect of the pleural peel constitutes the primary clinical problem. Lung entrapment may result from a visceral pleural peel secondary to active pleural inflammation, infection, or malignancy. In these cases, the underlying malignant or inflammatory condition is the primary clinical problem, which may or may not be complicated by unexpandable lung due to visceral pleural involvement. The recognition of trapped lung and lung entrapment as related, but distinct, clinical entities has direct consequences on clinical management. In our practice, pleural manometry is routinely performed during therapeutic thoracentesis and is useful for identification of unexpandable lung and has allowed us to understand the mechanisms surrounding a post-thoracentesis pneumothorax.

Empiric auto-titrating CPAP in people with suspected obstructive sleep apnea.

OBJECTIVE: Efficient diagnosis and treatment of obstructive sleep apnea (OSA) can be difficult because of time delays imposed by clinic visits and serial overnight polysomnography. In some cases, it may be desirable to initiate treatment for suspected OSA prior to polysomnography. Our objective was to compare the improvement of daytime sleepiness and sleep-related quality of life of patients with high clinical likelihood of having OSA who were randomly assigned to receive empiric auto-titrating continuous positive airway pressure (CPAP) while awaiting polysomnogram versus current usual care. METHODS: Serial patients referred for overnight polysomnography who had high clinical likelihood of having OSA were randomly assigned to usual care or immediate initiation of auto-titrating CPAP. Epworth Sleepiness Scale (ESS) scores and the Functional Outcomes of Sleep Questionnaire (FOSQ) scores were obtained at baseline, 1 month after randomization, and again after initiation of fixed CPAP in control subjects and after the sleep study in auto-CPAP patients. RESULTS: One hundred nine patients were randomized. Baseline demographics, daytime sleepiness, and sleep-related quality of life scores were similar between groups. One-month ESS and FOSQ scores were improved in the group empirically treated with auto-titrating CPAP. ESS scores improved in the first month by a mean of -3.2 (confidence interval -1.6 to -4.8, p < 0.001) and FOSQ scores improved by a mean of 1.5, (confidence interval 0.5 to 2.7, p = 0.02), whereas scores in the usual-care group did not change (p = NS). Following therapy directed by overnight polysomnography in the control group, there were no differences in ESS or FOSQ between the groups. No adverse events were observed. CONCLUSION: Empiric auto-CPAP resulted in symptomatic improvement of daytime sleepiness and sleep-related quality of life in a cohort of patients awaiting polysomnography who had a high pretest probability of having OSA. Additional studies are needed to evaluate the applicability of empiric treatment to other populations.