Pulmonary barotrauma in mechanical ventilation. Patterns and risk factors

Unraveling Ventilator-Induced Diaphragmatic Dysfunction: A Comprehensive Narrative Review on Pathogenesis, Diagnosis and Management of Ventilator-Induced Diaphragmatic Dysfunction

INTRODUCTION

Mechanical ventilation (MV) is a crucial intervention for patients with respiratory failure to ensure optimal gas exchange. However, there is strong evidence that MV exerts significant structural and functional alterations on the diaphragm, leading to a notable decline in its contractile force and the consequent atrophy of its muscle fibers. This condition, referred to as ventilator-induced diaphragmatic dysfunction (VIDD), is an integral factor contributing to challenges in weaning patients off MV, a reduction in their quality of life, and escalated Mortality Risks.

OBJECTIVES

This review highlights the complications of MV, with a focus on VIDD and its clinical implications. It explores bedside diagnostic tools for VIDD and examines exercise-based interventions aimed at preventing or reversing daiphragmatic weakness.

DISCUSSION

Rehabilitation programs, including early mobilization and inspiratory muscle training (IMT) for critically ill patients, have the potential to prevent or mitigate the adverse effects of prolonged Mechanical ventilator and improve clinical outcomes. Numerous studies have demonstrated that these interventions are both safe and feasible, offering benefits such as enhanced physical functioning, reduced duration of mechanical ventilation, and shorter stays in intensive care and hospital settings. However, despite these demonstrated advantages, the implementation of rehabilitation programs remains infrequent in routine clinical practice, often hindered by various perceived barriers.

CONCLUSION

Recognizing and addressing respiratory muscle weakness is crucial, as it represents a reversible and treatable factor that can significantly improve patient outcomes.

Pneumothorax in acute respiratory distress syndrome on extracorporeal membrane oxygenation support

INTRODUCTION

Pneumothorax is associated with poor prognosis in patients with acute respiratory distress syndrome (ARDS). We sought to examine the outcomes of patients who are supported on veno-venous extracorporeal membrane oxygenation (VV ECMO) and develop a pneumothorax.

METHODS

We retrospectively reviewed all adult VV ECMO patients supported for ARDS between 8/2014-7/2020 at our institution, excluding patients with recent lung resection and trauma. Clinical outcomes were compared between patients with a pneumothorax to those without a pneumothorax.

RESULTS

Two hundred eighty patients with ARDS on VV ECMO were analyzed. Of those, 213 did not have a pneumothorax and 67 did. Patients with a pneumothorax had a longer duration of ECMO support (30 days [16-55] versus 12 [7-22], p < 0.001) and hospital length of stay (51 days [27-93] versus 29 [18-49], p < 0.001), and lower survival-to-discharge (58.2% versus 77.5%, p = 0.002) compared to patients without a pneumothorax. Controlling for age, BMI, sex, RESP score and pre-ECMO ventilator days, the odds ratio of survival-to-discharge was 0.41 (95% CI 0.22-0.78) in patients with a pneumothorax compared to those without. There was a lower incidence of significant bleeding when chest tubes were placed by proceduralist services (2.4% versus 16.2%, p = 0.03). Removal of the chest tube prior to ECMO decannulation compared to removal after decannulation was associated with need for replacement (14.3% versus 0%, p = 0.01).

CONCLUSION

Patients who develop a pneumothorax and are supported with VV ECMO for ARDS have longer duration on ECMO and decreased survival. Further studies are needed to assess risk factors for development of pneumothorax in this patient population.

Lung, Pleura, and Diaphragm Point-of-Care Ultrasound

Thoracic Ultrasonography involves the ultrasonographic examination of the lungs, pleura, and diaphragm. This provides a plethora of clinical information during the point of care assessment of patients. The air filled lungs create consistent artifacts and careful examination and understanding of these artefactual signs can provide useful information on underlying clinicopathologic states. This review aims to provide a review of the ultrasound signs and features that can be seen in horacic ultrasonography and summarize the clinical evidence to support its use.

Incidence, outcomes and risk factors of barotrauma in veno-venous extracorporeal membrane oxygenation for acute respiratory distress syndrome

BACKGROUND

Although acute respiratory distress syndrome (ARDS) patients are provided a lung rest strategy during extracorporeal membrane oxygenation (ECMO) treatment, the exact conditions of barotrauma is unclear. Therefore, we analyzed the epidemiology and risk factors for barotrauma in ARDS patients using ECMO in a single, large ECMO center in China.

METHODS

A retrospective analysis was performed on 127 patients with ARDS received veno-venous (VV) ECMO who met the Berlin definition. The epidemiology and risk factors for barotrauma during ECMO were analyzed.

RESULTS

Among 127 patients with ARDS treated with ECMO, barotrauma occurred in 24 (18.9%) during ECMO and 9 (7.1%) after ECMO decannulation, mainly in the late stage of ARDS (75%) and ≥8 days during ECMO (54.2%). Univariate and multivariate analyses showed that younger ARDS patients (OR = 0.953, 95%CI 0.923-0.983, p = 0.003) and those with pneumocystis jirovecii pneumonia (PJP) (OR = 3.15, 95%CI 1.070-9.271, p = 0.037), elevated body temperature after establishing ECMO (OR = 2.997, 95%CI 1.325-6.779, p = 0.008) and low platelet count after establishing ECMO (OR = 0.985, 95%CI 0.972-0.998, p = 0.02) had an increased risk of barotrauma during ECMO. There was no difference in ventilator parameters between patients with and without barotrauma. Barotrauma during ECMO was mainly related to the etiology of the disease and disease state.

CONCLUSION

There is a high incidence of barotrauma in ARDS patients during ECMO, even after ECMO decannulation. Young age, PJP, elevated body temperature and low platelet count after establishing ECMO are risk factors of barotrauma, and those patients should be closely monitored by imaging, especially in the late stage of ARDS.

Risk factors of pneumothorax and pneumomediastinum in COVID-19: a matched case-control study

BACKGROUND

During the novel coronavirus disease-2019 pandemic, a considerable number of pneumothorax (PNX)/pneumomediastinum (PNM) associated with COVID-19 have been reported, and the incidence is higher in critically ill patients. Despite using a protective ventilation strategy, PNX/PNM still occurs in patients on invasive mechanical ventilation (IMV). This matched case-control study aims to identify the risk factors and clinical characteristics of PNX/PNM in COVID-19.

METHODS

This retrospective study enrolled adult patients with COVID-19, admitted to a critical care unit from March 1, 2020, to January 31, 2022. COVID-19 patients with PNX/PNM were compared, in a 1-2 ratio, to COVID-19 patients without PNX/PNM, matched for age, gender, and worst National Institute of Allergy and Infectious Diseases ordinal scale. Conditional logistic regression analysis was performed to assess the risk factors for PNX/PNM in COVID-19.

RESULTS

427 patients with COVID-19 were admitted during the period, and 24 patients were diagnosed with PNX/PNM. Body mass index (BMI) was significantly lower in the case group (22.8 kg/m2 and 24.7 kg/m2; P = 0.048). BMI was statistically significant risk factor for PNX/PNM in univariate conditional logistic regression analysis [odds ratio (OR), 0.85; confidence interval (CI), 0.72-0.996; P = 0.044]. For patients on IMV support, univariate conditional logistic regression analysis showed the statistical significance of the duration from symptom onset to intubation (OR, 1.14; CI, 1.006-1.293; P = 0.041).

CONCLUSIONS

Higher BMI tended to show a protective effect against PNX/PNM due to COVID-19 and delayed application of IMV might be a contributive factor for this complication.

Incidence and Outcome of Pneumomediastinum in Non-ICU Hospitalized COVID-19 Patients

OBJECTIVES

Pneumomediastinum (PNM) is a rare complication of mechanical ventilation, but its reported occurrence in patients with acute respiratory distress syndrome secondary to COVID-19 is significant. The objective is to determine the incidence, risk factors, and outcome of PNM in non-ICU hospitalized patients with severe-to-critical COVID-19 pneumonia.

DESIGN

Retrospective observational study.

SETTING

Population-based, single-setting, tertiary-care level COVID treatment center.

PATIENTS

Individuals hospitalized with a diagnosis of COVID-19 pneumonia and severe to critical illness were included. Those hospitalized without respiratory failure, observed for less than 24 hours, or admitted from an ICU were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients underwent a complete clinical assessment and chest CT scan, and were followed up from hospitalization to discharge or death. The outcome was the number of cases of PNM, defined as the presence of free air in the mediastinal tissues diagnosed by chest CT scan, in non-ICU hospitalized patients and the subsequent risk of intubation and mortality. PNM occurred in 48 out of 331 participants. The incidence was 14.5% (95% CI, 10.9-18.8%). A CT-Scan Severity score greater than 15 was positively associated with PNM (odds ratio [OR], 4.09; p = 0.002) and was observed in 35.2% of the participants (95% CI, 26.2-44.9%). Noninvasive ventilation was also positively associated with PNM (OR, 4.46; p = 0.005), but there was no positive association with airway pressures. Fifty patients (15%) were intubated, and 88 (27%) died. Both the risk for intubation and mortality were higher in patients with PNM, with a hazard ratio of 3.72 ( p < 0.001) and 3.27 ( p < 0.001), respectively.

CONCLUSIONS

Non-ICU hospitalized patients with COVID-19 have a high incidence of PNM, increasing the risk for intubation and mortality three- to four-fold, particularly in those with extensive lung damage. These findings help define the risk and outcome of PNM in severe-to-critical COVID-19 pneumonia in a non-ICU setting.

Imaging in the Intensive Care Unit

Radiology plays an important role in the management of the most seriously ill patients in the hospital. Over the years, continued advances in imaging technology have contributed to an improvement in patient care. However, even with such advances, the portable chest radiograph (CXR) remains one of the most commonly requested radiographic examinations. While they provide valuable information, CXRs remain relatively insensitive at revealing abnormalities and are often nonspecific. Chest computed tomography (CT) can display findings that are occult on CXR and is particularly useful at identifying and characterizing pleural effusions, detecting barotrauma including small pneumothoraces, distinguishing pneumonia from atelectasis, and revealing unsuspected or additional abnormalities which could result in increased morbidity and mortality if left untreated. CT pulmonary angiography is the modality of choice in the evaluation of pulmonary emboli which can complicate the hospital course of the ICU patient. This article will provide guidance for interpretation of CXR and thoracic CT images, discuss some of the invasive devices routinely used, and review the radiologic manifestations of common pathologic disease states encountered in ICU patients. In addition, imaging findings and complications of more specific clinical scenarios in which the incidence has increased in the ICU setting, such as patients who are immunocompromised, have interstitial lung disease, or COVID-19, will also be discussed. Communication between the radiologist and intensivist, particularly on complicated cases, is important to help increase diagnostic accuracy and leads to an improvement in the management of the most critically ill patients.

One-year experience after adoption of an on-table extubation protocol following pediatric cardiac surgery

OBJECTIVE

To report our initial experience with on-table extubation following cardiac surgery for congenital heart disease, assessing its efficacy and safety, and the potential for fast-tracking these patients through the intensive care unit (ICU).

METHODS

We decided to implement a multidisciplinary protocol aiming toward on-table extubation following congenital cardiac surgery at our hospital. Between December 2018 and January 2020, 376 patients underwent congenital cardiac surgery. The management strategy involved choosing the patients preoperatively, a specific anesthetic technique, application of a standard extubation protocol, multidisciplinary team approach, and perioperative echocardiogram for assessment of surgical repair. Relevant data were collected and analyzed.

RESULTS

Out of the 376 patients who underwent congenital cardiac surgery during the study period, 44 patients were extubated on-table. Although a majority of these patients belonged to Risk Adjustment for Congenital Heart Surgery-1 score (RACHS-1) 1 and 2 categories, 18% of the patients who were extubated on-table were of RACHS-3 category. This included a wide spectrum of anatomical substrates such as endocardial cushion defects, pulmonary venous anomalies, single ventricle physiology, valvular defects, and others such as cor triatriatum and sinus of Valsalva aneurysm. There was no in-hospital mortality related to on-table extubation. Only one patient was reintubated following on-table extubation resulting in a reintubation rate of 2.27% among those patients extubated on-table. The patients extubated on-table had a shorter ICU stay (25.89 ± 7.20 h) compared with those patients who underwent delayed extubation (59.30 ± 6.80 h). The duration of the hospital stay was also significantly reduced in these patients (91.09 ± 20.40 h) leading to an earlier discharge compared with those patients who underwent delayed extubation (134.40 ± 16.20 h).

CONCLUSION

On-table extubation is an attractive alternative in limited-resource environments to enhance recovery in patients following congenital cardiac malformations. Owing to the lack of significant comorbidities such as Chronic Obstructive Pulmonary Disease (COPD) in this patient population, corrective surgery for cardiac malformation usually optimizes the cardiorespiratory status. This results in more chances of successful extubation immediately following surgery. However, this requires proper perioperative planning, a careful discussion about the choice of patients, adoption of an extubation protocol, and most importantly, a multidisciplinary team approach. It is associated with low morbidity and mortality, with reduced length of stay in the ICU and hospital. This preliminary study demonstrated that on-table extubation is feasible following congenital cardiac surgery at our center and greatly reduces the intensive care requirements. This article focuses mainly on the decision-making process which determines the ideal candidates for on-table extubation and the anesthetic protocol implemented in a low-resource environment to enable the same.

Pneumomediastinum as patient self-inflicted lung injury in patients with acute respiratory distress syndrome due to COVID-19: a case series

Background

In patients with coronavirus disease (COVID-19) due to severe acute respiratory syndrome coronavirus 2 infection, pneumomediastinum has been increasingly reported in cases of noninvasive oxygen therapy, including high-flow nasal cannula, and invasive mechanical ventilation. However, its pathogenesis is still not understood.

Case Presentation

We report two cases of pneumomediastinum in acute respiratory distress syndrome (ARDS) caused by COVID-19. In both cases, control of spontaneous breathing with neuromuscular blocking agents resulted in resolution of pneumoperitoneum.

Conclusion

The improvement of pneumomediastinum with control of spontaneous breathing suggested patient self-inflicted lung injury as a possible mechanism in this case series. In ARDS cases with pneumomediastinum, in addition to controlling plateau pressure with conventional lung protective ventilation, spontaneous breathing should be controlled if the patient's inspiratory effort is suspected to be strong.

Incidence and management of pneumothorax, pneumomediastinum, and subcutaneous emphysema in COVID-19

Objective

The coronavirus disease 2019 (COVID-19) pandemic reached New York City in March 2020, leading to a state of emergency that affected many lives. Patients who contracted the disease presented with different phenotypes. Multiple reports have described the findings of computed tomography scans of these patients, several with pneumothoraces, pneumomediastinum, and subcutaneous emphysema. Our aim was to describe the incidence and management of pneumothorax, pneumomediastinum, and subcutaneous emphysema related to COVID-19 found on radiologic imaging.

Methods

A retrospective chart review was conducted of all confirmed COVID-19 patients admitted between early March and mid-May to two hospitals in New York City. Patient demographics, radiological imaging, and clinical courses were documented.

Results

Between early March and mid-May, a total of 1866 patients were diagnosed with COVID-19 in the two hospitals included in the study, of which 386 were intubated. The majority of these patients were men (1090, 58.4%). The distribution of comorbidities included the following: hypertension (1006, 53.9%), diabetes (544, 29.6%), and underlying lung disease (376, 20.6%). Among the 386 intubated patients, 65 developed study-specific complications, for an overall incidence of 16.8%; 36 developed a pneumothorax, 2 developed pneumomediastinum, 1 had subcutaneous emphysema, and 26 had a combination of both. The mean time of invasive ventilation was 14 days (0-46, interquartile range = 6-19, median 11). The average of highest positive end expiratory pressure within 72 h of study complication was 11 (5-24) cmH20. The average of the highest peak inspiratory pressure within 72 h of complication was 35.3 (17-52) cmH2O. In non-Intubated patients, 9/1480 had spontaneous pneumothorax, for an overall incidence of 0.61 %.

Conclusion

Intubated patients with COVID-19 pneumonia are at high risk of pneumothorax, pneumomediastinum, and subcutaneous emphysema. These should be considered in differential diagnosis of shortness of breath or hypoxia in a patient with a new diagnosis of COVID-19 or worsening hemodynamics or respiratory failure in an intensive care unit setting.

Barotrauma and its complications in COVID-19 patients: a retrospective study at tertiary care hospital of Eastern India

BACKGROUND

The development of barotrauma in COVID-19 patients who were ventilated and admitted to the intensive treatment unit seemed to have been a problematic issue in the COVID era. This study aimed to explore the possibility of developing the barotrauma-related issues with mechanical ventilation in the cases of individuals suffering from COVID-19.

RESULTS

Out of 48 patients who developed barotrauma, 30 (62.5%) presented with pneumothorax, 22 (45.8%) with pneumomediastinum, 10 (20.8%) with subcutaneous emphysema, and 2 (4.1%) with pneumopericardium. Of those that developed barotrauma, 45 (93.7%) patients were in acute respiratory distress syndrome. In patients with and without barotrauma, significant factors were white blood cell count (p = 0.001), neutrophil percentage (p = 0.012), and lymphocyte percentage (p = 0.014). There were no statistically significant differences in CRP, procalcitonin, d-dimer test, LDH, or ferritin.

CONCLUSIONS

Patients infected with COVID-19 have a high risk of barotrauma when on mechanical ventilation. As a result, the death rate in this patient group is higher.

Clinical Profile of Patients with Severe Acute Respiratory Syndrome Coronavirus 2 Infection Developing Pulmonary Barotrauma on Mechanical Ventilation

Background

There is limited information on clinical profile and outcomes of patients on mechanical ventilation (MV) who developed pulmonary barotrauma (PBT) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Patients and methods

In a retrospective observational study, all SARS-CoV-2 pneumonia patients admitted from March 28, 2020, to August 31, 2020, at Sir HN Reliance Foundation Hospital and Research Center and Seven Hills Hospital (Reliance Facility), Mumbai, India, of 18 years and above on MV and developed PBT, were included.

Results

A total of 14 SARS-CoV-2 patients of 45 on MV (31.0%) developed PBT of 1,029 hospitalized. All patients were male and divided as per admission into PaO₂/FiO₂ (P/F) ≤100 (median 80) and P/F >100 (median 222) group. Pneumothorax developed in seven and six cases of P/F ≤100 and P/F >100 groups, respectively. Three patients in each group developed subcutaneous emphysema, while four developed pneumomediastinum in P/F >100 group. Twelve patients (7, P/F ≤100, and 5, P/F >100) were on invasive, while two (P/F >100) were on noninvasive MV. The mean P/F on the day of PBT was reduced by 27.5 and 65.3%, while peak inspiratory pressure was elevated with a median of 36 and 28 cm H₂O in P/F ≤100 and P/F >100 groups, respectively. The median highest tidal volume (420 mL), positive-end expiratory pressure (8 vs 6 cm H₂O) on the day of PBT, and length of hospital stay (11 vs 25 days) did not differ between two groups. Survival was 28.6% (4/14).

Conclusion

SARS-CoV-2 patients requiring MV with PBT had poor outcomes. Clinicians should be vigilant about the diagnosis of PBT.

How to cite this article

Kargirwar KV, Rathod D, Kumar V, Patel M, Shah M, Choudhury H, et al. Clinical Profile of Patients with Severe Acute Respiratory Syndrome Coronavirus 2 Infection Developing Pulmonary Barotrauma on Mechanical Ventilation. Indian J Crit Care Med 2022;26(5):613–618.

Spontaneous pneumothorax, pneumomediastinum and subcutaneous emphysema in non-ventilated COVID-19 patients

Aim:

Pneumothorax (PNX), pneumomediastinum (PMD) and subcutaneous emphysema (SCE) are COVID-19 complications related to positive-pressure ventilation. We analyzed the pathophysiology of these complications without ventilation.

Patients & methods:

Out of 1845 admitted COVID-19 patients, we retrospectively collected data for 15 patients, from a tertiary medical center, from 1 October 2020 to 31 March 2021.

Results:

Five patients suffered from spontaneous PNX, 8/15 developed PMD and 8/15 developed SCE. The mean BMI was 29.7, as most patients were obese or overweight. Most patients had lymphocytopenia and increased C-reactive protein, ferritin and lactate dehydrogenase levels. Eleven patients succumbed to the disease.

Conclusion:

Risk factors of spontaneous PNX, PMD and SCE in COVID-19 patients need further investigations by conducting more comprehensive case–control studies.

We have investigated spontaneous alveolar rupture as a complication in 15 COVID-19 patients. Manifested as pneumothorax, pneumomediastinum and subcutaneous emphysema, these complications are less common in patients without mechanical ventilation. Management of these patients was either conservative or by insertion of a chest tube. Eventually, 11 out of 15 patients have passed away due to respiratory failure.

Complications associated with long-term positive-pressure ventilation in dogs and cats: 67 cases

OBJECTIVES

To determine the complications associated with positive-pressure ventilation (PPV) in dogs and cats.

DESIGN

Retrospective study from October 2009 to September 2013.

SETTING

University Teaching Hospital.

ANIMALS

Fifty-eight dogs and 9 cats.

MEASUREMENTS AND MAIN RESULTS

Medical records were retrospectively reviewed; signalment, complications associated with PPV, duration of PPV, and outcome were recorded. Complications most commonly recorded during PPV included hypothermia 41/67 (61%), hypotension 39/67 (58%), cardiac arrhythmias 33/67 (49%), a positive fluid balance 31/67 (46%), oral lesions 25/67 (37%), and corneal ulcerations 24/67 (36%). A definition of ventilator-associated events (VAE) extrapolated from the Center of Disease Control's criteria was applied to 21 cases that received PPV for at least 4 days in this study. Ventilator-associated conditions occurred in 5 of 21 (24%) of cases with infection-related ventilator-associated conditions and ventilator-associated pneumonia identified in 3 of 21 (14%) cases.

CONCLUSIONS

Complications are common and diverse in dogs and cats receiving long-term PPV and emphasizes the importance of intensive, continuous patient monitoring and appropriate nursing care protocols. Many of the complications identified could be serious without intervention and suggests that appropriate equipment alarms could improve patient safety. Development of veterinary specific surveillance tools such as the VAE criteria would aid future investigations and allow for effective multicenter studies.

Clinical impact of pneumothorax in patients with Pneumocystis jirovecii pneumonia and respiratory failure in an HIV-negative cohort

Background

Pneumocystis jirovecii pneumonia (PCP) with acute respiratory failure can result in development of pneumothorax during treatment. This study aimed to identify the incidence and related factors of pneumothorax in patients with PCP and acute respiratory failure and to analyze their prognosis.

Methods

We retrospectively reviewed the occurrence of pneumothorax, including clinical characteristics and results of other examinations, in 119 non-human immunodeficiency virus patients with PCP and respiratory failure requiring mechanical ventilator treatment in a medical intensive care unit (ICU) at a tertiary-care center between July 2016 and April 2019.

Results

During follow up duration, twenty-two patients (18.5%) developed pneumothorax during ventilator treatment, with 45 (37.8%) eventually requiring a tracheostomy due to weaning failure. Cytomegalovirus co-infection (odds ratio 13.9; p = 0.013) was related with occurrence of pneumothorax in multivariate analysis. And development of pneumothorax was not associated with need for tracheostomy and mortality. Furthermore, analysis of survivor after 28 days in ICU, patients without pneumothorax were significantly more successful in weaning from mechanical ventilator than the patients with pneumothorax (44% vs. 13.3%, p = 0.037). PCP patients without pneumothorax showed successful home discharges compared to those who without pneumothorax (p = 0.010).

Conclusions

The development of pneumothorax increased in PCP patient with cytomegalovirus co-infection, pneumothorax might have difficulty in and prolonged weaning from mechanical ventilators, which clinicians should be aware of when planning treatment for such patients.

A Case of Complicated Traumatic Generalized Surgical Emphysema, Pneumomediastinum, Pneumopericardium, Pneumothorax, and Pneumoperitoneum Due to Accidental Dislodgement of Tracheostomy Tube

A tracheostomy tube (TT) is usually taken out in a well-planned and coordinated manner after the underlying condition that necessitated the procedure is resolved. The inadvertent removal or dislodgement of the TT from the stroma is known as accidental extubation or decannulation. This event may prove fatal in a stable patient. Like other respiratory procedures, tracheostomy with the long-term placement of tracheal tube comes with several risks, including scarring of the trachea, pneumothorax, tracheal rupture, and tracheoesophageal fistula. Other complications may include pneumomediastinum (PM) or the escape of air into the surrounding tissue. This may be attributed to several reasons, including mispositioning of the tracheal tube, barotrauma, or tracheal rupture. In some cases, PM presents with free air into cavities such as the thorax, peritoneum, or subcutaneous tissue. Although not fatal, it may require complex treatments such as ventilator management, high-flow oxygen, or, in some cases, surgical intervention. In this article, we describe a rare case of PM and generalized surgical emphysema due to mispositioning of the tracheal tube.

Incidence and risk factors for pneumomediastinum in COVID-19 patients in the intensive care unit

 

OBJECTIVES

The incidence of pneumomediastinum (PNMD), its causes of development and its effect on prognosis in the coronavirus disease 2019 (COVID-19) are not clear.

METHODS

Between March 2020 and December 2020, 427 patients with real-time reverse transcriptase-polymerase chain reaction-confirmed COVID-19 admitted to the intensive care unit were analysed retrospectively. Using receiver operating characteristic analysis, the area under the curve (AUC) for initial invasive mechanical ventilation (MV) variables such as initial peak inspiratory pressure (PIP), PaO₂/FiO₂ (P/F ratio), tidal volume, compliance and positive end-expiratory pressure was evaluated regarding PNMD development.

RESULTS

The incidence of PNMD was 5.6% (n = 24). PNMD development rate was 2.7% in non-invasive MV and 6.2% in MV [odds ratio (OR) 2.352, 95% confidence interval (CI) 0.541–10.232; P = 0.400]. In the multivariate analysis, the independent risk factors affecting the development of PNMD were PIP (OR 1.238, 95% CI 1.091–1.378; P < 0.001) and P/F ratio (OR 0.982, 95% CI 0.971–0.994; P = 0.004). P/F ratio (AUC 0.815, 95% CI 0.771–0.854), PIP (AUC 0.780, 95% CI 0.734–0.822), compliance (AUC 0.735, 95% CI 0.677–0.774) and positive end-expiratory pressure (AUC 0.718, 95% CI 0.668–0.764) were the best predictors for PNMD development. Regarding the multivariate analysis, independent risk factors affecting mortality were detected as age (OR 1.015, 95% CI 0.999–1.031; P = 0.04), comorbidity (OR 1.940, 95% CI 1.100–3.419; P = 0.02), mode of breathing (OR 48.345, 95% CI 14.666–159.360; P < 0.001), PNMD (OR 5.234, 95% CI 1.379–19.857; P = 0.01), positive end-expiratory pressure (OR 1.305, 95% CI 1.062–1.603; P = 0.01) and tidal volume (OR 0.995, 95% CI 0.992–0.998; P = 0.004).

CONCLUSIONS

PNMD development was associated with the initial P/F ratio and PIP. Therefore, it was considered to be related to both the patient and barotrauma. PNMD is a poor prognostic factor for COVID-19.

Pneumothorax in patients with respiratory failure in ICU

Pneumothorax is not an uncommon occurrence in ICU patients. Barotrauma and iatrogenesis remain the most common causes for pneumothorax in critically ill patients. Patients with underlying lung disease are more prone to develop pneumothorax, especially if they require positive pressure ventilation. A timely diagnosis of pneumothorax is critical as it may evolve into tension physiology. Most occurrences of pneumothoraces are readily diagnosed with a chest X-ray. Tension pneumothorax is a medical emergency, and managed with immediate needle decompression followed by tube thoracostomy. A computed tomography (CT) scan of the chest remains the gold standard for diagnosis; however, getting a CT scan of the chest in a critically ill patient can be challenging. The use of thoracic ultrasound has been emerging and is proven to be superior to chest X-ray in making a diagnosis. The possibility of occult pneumothorax in patients with thoracoabdominal blunt trauma should be kept in mind. Patients with pneumothorax in the ICU should be managed with a tube thoracostomy if they are symptomatic or on mechanical ventilation. The current guidelines recommend a small-bore chest tube as the first line management of pneumothorax. In patients with persistent air leak or whose lungs do not re-expand, a thoracic surgery consultation is recommended. In non-surgical candidates, bronchoscopic interventions or autologous blood patch are other options.

Noninvasive respiratory support and patient self-inflicted lung injury in COVID-19: a narrative review

COVID-19 pneumonia is associated with hypoxaemic respiratory failure, ranging from mild to severe. Because of the worldwide shortage of ICU beds, a relatively high number of patients with respiratory failure are receiving prolonged noninvasive respiratory support, even when their clinical status would have required invasive mechanical ventilation. There are few experimental and clinical data reporting that vigorous breathing effort during spontaneous ventilation can worsen lung injury and cause a phenomenon that has been termed patient self-inflicted lung injury (P-SILI). The aim of this narrative review is to provide an overview of P-SILI pathophysiology and the role of noninvasive respiratory support in COVID-19 pneumonia. Respiratory mechanics, vascular compromise, viscoelastic properties, lung inhomogeneity, work of breathing, and oesophageal pressure swings are discussed. The concept of P-SILI has been widely investigated in recent years, but controversies persist regarding its mechanisms. To minimise the risk of P-SILI, intensivists should better understand its underlying pathophysiology to optimise the type of noninvasive respiratory support provided to patients with COVID-19 pneumonia, and decide on the optimal timing of intubation for these patients.

Pneumomediastinum in COVID-19: A series of three cases and review of literature

Coronavirus disease-19 caused by severe acute respiratory syndrome Corona virus-2 is characterised by wide heterogeneity in clinical presentation. The typical radiographic findings in COVID-19 include bilateral ground-glass opacities and/or consolidations predominantly affecting the lower lobes and posterior segments of lungs. Other rare abnormal radiographic findings include pneumothorax, pneumomediastinum and pneumopericardium. There has been an increased incidence of pneumomediastinum, a rare but potentially life-threatening complication during this pandemic. It may be spontaneous or secondary. Pneumomediastinum may be due to barotrauma, cytokine storm induced diffuse alveolar injury or direct viral infection of type I and type II pneumocytes. The presence of pneumomediastinum in COVID-19 patients may indicate extensive alveolar membrane destruction and those patients need close monitoring. There are no consensus guidelines in managing COVID-19 patients with pneumomediastinum. Higher mortality rates (70.58%) are reported in intubated COVID-19 patients with pneumomediastinum. The development of pneumomediastinum in COVID-19 should be considered as a poor prognostic factor.

Dexamethasone and transdehydroandrosterone significantly reduce pulmonary epithelial cell injuries associated with mechanical ventilation

Many patients who suffer from pulmonary diseases cannot inflate their lungs normally, as they need mechanical ventilation (MV) to assist them. The stress associated with MV can damage the delicate epithelium in small airways and alveoli, which can cause complications resulting in ventilation-induced lung injuries (VILIs) in many cases, especially in patients with acute respiratory distress syndrome (ARDS). Therefore, efforts were directed to develop safe modes for MV. In our work, we propose a different approach to decrease injuries of epithelial cells (EpCs) upon MV. We alter EpCs' cytoskeletal structure to increase their survival rate during airway reopening conditions associated with MV. We tested two anti-inflammatory drugs dexamethasone (DEX) and transdehydroandrosterone (DHEA) to alter the cytoskeleton. Cultured rat L2 alveolar EpCs were exposed to airway reopening conditions using a parallel-plate perfusion chamber. Cells were exposed to a single bubble propagation to simulate stresses associated with mechanical ventilation in both control and study groups. Cellular injury and cytoskeleton reorganization were assessed via fluorescence microscopy, whereas cell topography was studied via atomic force microscopy (AFM). Our results indicate that culturing cells in media, DEX solution, or DHEA solution did not lead to cell death (static cultures). Bubble flows caused significant cell injury. Preexposure to DEX or DHEA decreased cell death significantly. The AFM verified alteration of cell mechanics due to actin fiber depolymerization. These results suggest potential beneficial effects of DEX and DHEA for ARDS treatment for patients with COVID-19. They are also critical for VILIs and applicable to future clinical studies.NEW & NOTEWORTHY Preexposure of cultured cells to either dexamethasone or transdehydroandrosterone significantly decreases cellular injuries associated with mechanical ventilation due to their ability to alter the cell mechanics. This is an alternative protective method against VILIs instead of common methods that rely on modification of mechanical ventilator modes.

Acute overventilation does not cause lung damage in moderately hemorrhaged swine

Airway management is important in trauma and critically ill patients. Prolonged mechanical ventilation results in overventilation-induced lung barotrauma, but few studies have examined the consequence of acute (1 h or less) overventilation. We hypothesized that acute hyperventilation, as might inadvertently be performed in prehospital settings, would elevate systemic inflammation and cause lung damage. Female Yorkshire pigs (40-50 kg, n = 10/group) were anesthetized, instrumented for hemodynamic measurements and blood sampling, and underwent a 25% controlled hemorrhage followed by 1 h of 1) spontaneous breathing, 2) "normal" bag ventilation (4.8 L·min volume, ∼400 mL tidal volume, 12 breaths/minute), 3) bag hyperventilation (9 L·min volume, ∼750 mL tidal volume, 12 breaths/minute), 4) maximum hyperventilation (15 L·min volume, ∼750 mL tidal volume, 20 breaths/minute), or 5) mechanical ventilation. Pigs then regained consciousness and recovered for 24 h, followed by euthanasia and collection of blood and tissue samples. No level of manual ventilation had any significant impact on hemodynamic variables. Blood markers of tissue damage and plasma cytokines were not statistically different between groups with the exception of a transient increase in IL-1β; all values returned to baseline by 24 h. On pathological review, severity and distribution of lung edema or other gross pathologies were not significantly different between groups. These data indicate hyperventilation causes no adverse effects, to include inflammation and tissue damage, and that acute overventilation, as could be seen in the prehospital phase of trauma care, does not produce evidence of adverse effects on the lungs following moderate hemorrhage.NEW & NOTEWORTHY Appropriate airway management is essential in trauma and critically ill patients. Prolonged mechanical ventilation can result in overventilation-induced lung barotrauma, but few studies have examined the consequence of acute overventilation. We investigated the outcome of hemorrhage followed by 1 h of overventilation in swine. We found that acute overventilation, as could be seen in the prehospital phase of trauma care, does not produce evidence of adverse effects on otherwise healthy lungs following moderate hemorrhage.

Prevalence and risk factors of barotrauma in Covid-19 patients admitted to an intensive care unit in Kuwait; a retrospective cohort study

BACKGROUND

The development of barotrauma has been suggested to complicate the management of mechanically ventilated COVID-19 patients admitted to the intensive care unit (ICU). This study aims to identify potential risk factors associated with the development of barotrauma related complications in COVID-19 patients receiving mechanical ventilation.

METHODS

A retrospective cohort study was carried out in a single COVID-19 designated center in Kuwait. Three hundred and forty-three confirmed COVID-19 patients transferred and/or admitted to our institution between February 26, 2020 and June 20, 2020 were included in the study. All patients were admitted into the ICU with the majority being mechanically ventilated (81.3%).

RESULTS

Fifty-four (15.4%) patients developed barotrauma, of which 49 (90.7%) presented with pneumothorax, and 14.8% and 3.7% due to pneumomediastinum and pneumopericardium respectively. Of those that developed barotrauma, 52 (96.3%) patients were in acute respiratory distress syndrome (ARDS). Biochemically, the white blood cells (p = 0.001), neutrophil percentage (p = 0.012), lymphocyte percentage (p = 0.014), neutrophil: lymphocyte ratio (NLR) (p=<0.001) and lactate dehydrogenase (LDH) (p = 0.002) were found to be significantly different in patients that developed barotrauma. Intubation due to low level of consciousness (p = 0.007), a high admission COVID-GRAM score (p = 0.042), and a positive-end expiratory pressure (PEEP) higher than the control group (p = 0.016) were identified as potential risk factors for the development of barotrauma.

CONCLUSION

Patients infected with COVID-19 have a significant risk of developing barotrauma when receiving invasive mechanical ventilation. This poses a substantial impact on the hospital course of the patients and clinical outcome, correlating to a higher mortality rate in this cohort of patients.

Pulmonary Barotrauma Resulting from Mechanical Ventilation in 2 Patients with a Diagnosis of COVID-19 Pneumonia

BACKGROUND Invasive mechanical ventilation can cause pulmonary barotrauma due to elevated transpulmonary pressure and alveolar rupture. A significant proportion of COVID-19 patients with acute respiratory distress syndrome (ARDS) will require mechanical ventilation. We present 2 interesting cases that demonstrate the possibility of COVID-19-associated ARDS manifesting with pulmonary barotrauma at acceptable ventilatory pressures. CASE REPORT The first patient was a 71-year-old man who was intubated and placed on mechanical ventilation due to hypoxemic respiratory failure from SARS-CoV-2 infection. His partial pressure of O2 to fraction of inspired oxygen ratio (PaO2/FiO2) was 156. He developed subcutaneous emphysema (SE) and pneumomediastinum on day 5 of mechanical ventilation at ventilatory settings of positive end-expiratory pressure (PEEP) ≤15 cmH₂O, plateau pressure (Pplat) ≤25 cmH₂O and pulmonary inspiratory pressure (PIP) ≤30 cmH₂O. He was managed with 'blow-hole' incisions, with subsequent clinical resolution of subcutaneous emphysema. The second patient was a 58-year-old woman who was also mechanically ventilated due to hypoxemic respiratory failure from COVID-19, with PaO2/FiO2 of 81. She developed extensive SE with pneumomediastinum and pneumothorax while on mechanical ventilation settings PEEP 13 cmH₂O and PIP 28 cmH₂O, Pplat 18 cmH₂O, and FiO2 90%. SE was managed with blow-hole incisions and pneumothorax with chest tube. CONCLUSIONS Clinicians should be aware of pulmonary barotrauma as a possible complication of COVID-19 pulmonary disease, even at low ventilatory pressures.

Pneumothorax in Mechanically Ventilated Patients with COVID-19 Infection

Data on patient-related factors associated with pneumothorax among critically ill patients with COVID-19 pneumonia is limited. Reports of spontaneous pneumothorax in patients with coronavirus disease 2019 (COVID-19) suggest that the COVID-19 infection could itself cause pneumothorax in addition to the ventilator-induced trauma among mechanically ventilated patients. Here, we report a case series of five mechanically ventilated patients with COVID-19 infection who developed pneumothorax. Consecutive cases of intubated patients in the intensive care unit with the diagnosis of COVID-19 pneumonia and pneumothorax were included. Data on their demographics, preexisting risk factors, laboratory workup, imaging findings, treatment, and survival were collected retrospectively between March and July 2020. Four out of five patients (4/5; 80%) had a bilateral pneumothorax, while one had a unilateral pneumothorax. Of the four patients with bilateral pneumothorax, three (3/4; 75%) had secondary bacterial pneumonia, two had pneumomediastinum and massive subcutaneous emphysema, and one of these two had an additional pneumoperitoneum. A surgical chest tube or pigtail catheter was placed for the management of pneumothorax. Three out of five patients with pneumothorax died (3/5; 60%), and all of them had bilateral involvement. The data from these cases suggest that pneumothorax is a potentially fatal complication of COVID-19 infection. Large prospective studies are needed to study the incidence of pneumothorax and its sequelae in patients with COVID-19 infection.

Pneumomediastinum and subcutaneous emphysema in COVID-19: barotrauma or lung frailty?

Background

In mechanically ventilated acute respiratory distress syndrome (ARDS) patients infected with the novel coronavirus disease (COVID-19), we frequently recognised the development of pneumomediastinum and/or subcutaneous emphysema despite employing a protective mechanical ventilation strategy. The purpose of this study was to determine if the incidence of pneumomediastinum/subcutaneous emphysema in COVID-19 patients was higher than in ARDS patients without COVID-19 and if this difference could be attributed to barotrauma or to lung frailty.

Methods

We identified both a cohort of patients with ARDS and COVID-19 (CoV-ARDS), and a cohort of patients with ARDS from other causes (noCoV-ARDS).

Patients with CoV-ARDS were admitted to an intensive care unit (ICU) during the COVID-19 pandemic and had microbiologically confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. NoCoV-ARDS was identified by an ARDS diagnosis in the 5 years before the COVID-19 pandemic period.

Results

Pneumomediastinum/subcutaneous emphysema occurred in 23 out of 169 (13.6%) patients with CoV-ARDS and in three out of 163 (1.9%) patients with noCoV-ARDS (p<0.001). Mortality was 56.5% in CoV-ARDS patients with pneumomediastinum/subcutaneous emphysema and 50% in patients without pneumomediastinum (p=0.46).

CoV-ARDS patients had a high incidence of pneumomediastinum/subcutaneous emphysema despite the use of low tidal volume (5.9±0.8 mL·kg⁻¹ ideal body weight) and low airway pressure (plateau pressure 23±4 cmH₂O).

Conclusions

We observed a seven-fold increase in pneumomediastinum/subcutaneous emphysema in CoV-ARDS. An increased lung frailty in CoV-ARDS could explain this finding more than barotrauma, which, according to its etymology, refers to high transpulmonary pressure.

Pneumomediastinum is more frequent in #COVID19 patients with ARDS despite the use of a protective ventilatory approach. Lung frailty, and not barotrauma, appears to be the main cause of this finding.https://bit.ly/36FQe03

Pneumothorax in COVID-19 disease- incidence and clinical characteristics

Background

Spontaneous pneumothorax is an uncommon complication of COVID-19 viral pneumonia. The exact incidence and risk factors are still unknown. Herein we review the incidence and outcomes of pneumothorax in over 3000 patients admitted to our institution for suspected COVID-19 pneumonia.

Methods

We performed a retrospective review of COVID-19 cases admitted to our hospital. Patients who were diagnosed with a spontaneous pneumothorax were identified to calculate the incidence of this event. Their clinical characteristics were thoroughly documented. Data regarding their clinical outcomes were gathered. Each case was presented as a brief synopsis.

Results

Three thousand three hundred sixty-eight patients were admitted to our institution between March 1st, 2020 and June 8th, 2020 for suspected COVID 19 pneumonia, 902 patients were nasopharyngeal swab positive. Six cases of COVID-19 patients who developed spontaneous pneumothorax were identified (0.66%). Their baseline imaging showed diffuse bilateral ground-glass opacities and consolidations, mostly in the posterior and peripheral lung regions. 4/6 cases were associated with mechanical ventilation. All patients required placement of a chest tube. In all cases, mortality (66.6%) was not directly related to the pneumothorax.

Conclusion

Spontaneous pneumothorax is a rare complication of COVID-19 viral pneumonia and may occur in the absence of mechanical ventilation. Clinicians should be vigilant about the diagnosis and treatment of this complication.

On some factors determining the pressure drop across tracheal tubes during high-frequency percussive ventilation: a flow-independent model

To provide an in vitro estimation of the pressure drop across tracheal tubes (ΔP_TT) in the face of given pulsatile frequencies and peak pressures (P_work) delivered by a high-frequency percussive ventilator (HFPV) applied to a lung model. Tracheal tubes (TT) 6.5, 7.5 and 8.0 were connected to a test lung simulating the respiratory system resistive (R = 5, 20, 50 cmH₂O/L/s) and elastic (C = 10, 20, and 50 mL/cmH₂O) loads. The model was ventilated by HFPV with a pulse inspiratory peak pressure (work pressure P_work) augmented in 5-cmH₂O steps from 20 to 45 cmH₂O, yielding 6 diverse airflows. The percussive frequency (f) was set to 300, 500 and 700 cycles/min, respectively. Pressure (Paw and Ptr) and flow (V’) measurements were performed for all 162 possible combinations of loads, frequencies, and work pressures for each TT size, thus yielding 486 determinations. For each respiratory cycle ΔP_TT was calculated by subtracting each peak Ptr from its corresponding peak Paw. A non-linear model was constructed to assess the relationships between single parameters. Performance of the produced model was measured in terms of root mean square error (RMSE) and the coefficient of determination (r²). ΔP_TT was predicted by P_work (exponential Gaussian relationship), resistance (quadratic and linear terms), frequency (quadratic and linear terms) and tube diameter (linear term), but not by compliance. RMSE of the model on the testing dataset was 1.17 cmH₂O, r² was 0.79 and estimation error was lower than 1 cmH₂O in 68% of cases. As a result, even without a flow value, the physician would be able to evaluate ΔP_TT pressure. If the present results of our bench study could be clinically confirmed, the use of a nonconventional ventilatory strategy as HFPV, would be safer and easier.

Pneumomediastinum following intubation in COVID-19 patients: a case series

The number of patients requiring tracheal intubation rose dramatically in March and April 2020 with the COVID-19 outbreak. Our thoracic surgery department has seen an increased incidence of severe pneumomediastinum referred for surgical opinion in intubated patients with COVID-19 pneumonitis. Here we present a series of five patients with severe pneumomediastinum requiring decompression therapy over a 7-day period in the current COVID-19 outbreak. We hypothesise that the mechanism for this is the aggressive disease pathophysiology with an increased risk of alveolar damage and tracheobronchial injury, along with the use of larger-bore tracheal tubes and higher ventilation pressures. We present this case series in order to highlight the increased risk of this potentially life-threatening complication among the COVID-19 patient cohort and offer guidance for its management to critical care physicians.

Descriptive Analysis of Extubations Performed in an Emergency Department-based Intensive Care Unit

Introduction

Extubation of appropriate patients in the emergency department (ED) may be a strategy to avoid preventable or short-stay intensive care unit (ICU) admissions, and could allow for increased ventilator and ICU bed availability when demand outweighs supply. Extubation is infrequently performed in the ED, and a paucity of outcome data exists. Our objective was to descriptively analyze characteristics and outcomes of patients extubated in an ED-ICU setting.

Methods

We conducted a retrospective observational study at an academic medical center in the United States. Adult ED patients extubated in the ED-ICU from 2015–2019 were retrospectively included and analyzed.

Results

We identified 202 patients extubated in the ED-ICU; 42% were female and median age was 60.86 years. Locations of endotracheal intubation included the ED (68.3%), outside hospital ED (23.8%), and emergency medical services/prehospital (7.9%). Intubations were performed for airway protection (30.2%), esophagogastroduodenoscopy (27.7%), intoxication/ingestion (17.3%), respiratory failure (13.9%), seizure (7.4%), and other (3.5%). The median interval from ED arrival to extubation was 9.0 hours (interquartile range 6.2–13.6). One patient (0.5%) required unplanned re-intubation within 24 hours of extubation. The attending emergency physician (EP) at the time of extubation was not critical care fellowship trained in the majority (55.9%) of cases. Sixty patients (29.7%) were extubated compassionately; 80% of these died in the ED-ICU, 18.3% were admitted to medical-surgical units, and 1.7% were admitted to intensive care. Of the remaining patients extubated in the ED-ICU (n = 142, 70.3%), zero died in the ED-ICU, 61.3% were admitted to medical-surgical units, 9.9% were admitted to intensive care, and 28.2% were discharged home from the ED-ICU.

Conclusion

Select ED patients were safely extubated in an ED-ICU by EPs. Only 7.4% required ICU admission, whereas if ED extubation had not been pursued most or all patients would have required ICU admission. Extubation by EPs of appropriately screened patients may help decrease ICU utilization, including when demand for ventilators or ICU beds is greater than supply. Future research is needed to prospectively study patients appropriate for ED extubation.

Detection and Management of Intraoperative Pneumothorax during Laparoscopic Cholecystectomy

Intraoperative pneumothorax is a rare but potentially lethal complication during general anesthesia. History of lung disease, barotrauma, and laparoscopic surgery increase the risk of developing intraoperative pneumothorax. The diagnosis during surgery could be difficult because the signs are often nonspecific. We report a case of a middle-aged gentleman who developed right pneumothorax during an elective laparoscopic cholecystectomy. The patient had no risk factors for adverse events during the preoperative assessment (ASA1). The patient underwent general anesthesia and was put on mechanical ventilation. The first signs of abnormality immediately after surgical port insertion were tachycardia and low oxygen saturation in addition to sings of airway obstruction. The diagnosis of pneumothorax was made clinically by chest auscultation and later confirmed by intraoperative chest radiograph. Supportive treatment was started immediately through halting the surgery and manually ventilating the patient using 100% oxygen. Definitive treatment was then done by inserting an intercostal tube. After stabilizing the patient, the surgery was completed; then, the patient was extubated and shifted to the surgical ward. Postoperative computed tomography (CT) scan was done and showed only minimal liver laceration. The patient was discharged after removing the intercostal tube and was stable at the follow-up visit. Therefore, it is important to have a high index of suspicion to early detect and treat such complication. In addition, good communication with the surgeon and use of available diagnostic tools will aid in the proper management of such cases.

Temporal Changes in Ventilator Settings in Patients With Uninjured Lungs: A Systematic Review

In patients with uninjured lungs, increasing evidence indicates that tidal volume (VT) reduction improves outcomes in the intensive care unit (ICU) and in the operating room (OR). However, the degree to which this evidence has translated to clinical changes in ventilator settings for patients with uninjured lungs is unknown. To clarify whether ventilator settings have changed, we searched MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for publications on invasive ventilation in ICUs or ORs, excluding those on patients <18 years of age or those with >25% of patients with acute respiratory distress syndrome (ARDS). Our primary end point was temporal change in VT over time. Secondary end points were changes in maximum airway pressure, mean airway pressure, positive end-expiratory pressure, inspiratory oxygen fraction, development of ARDS (ICU studies only), and postoperative pulmonary complications (OR studies only) determined using correlation analysis and linear regression. We identified 96 ICU and 96 OR studies comprising 130,316 patients from 1975 to 2014 and observed that in the ICU, VT size decreased annually by 0.16 mL/kg (-0.19 to -0.12 mL/kg) (P < .001), while positive end-expiratory pressure increased by an average of 0.1 mbar/y (0.02-0.17 mbar/y) (P = .017). In the OR, VT size decreased by 0.09 mL/kg per year (-0.14 to -0.04 mL/kg per year) (P < .001). The change in VTs leveled off in 1995. Other intraoperative ventilator settings did not change in the study period. Incidences of ARDS (ICU studies) and postoperative pulmonary complications (OR studies) also did not change over time. We found that, during a 39-year period, from 1975 to 2014, VTs in clinical studies on mechanical ventilation have decreased significantly in the ICU and in the OR.

Unexpected Tension Pneumothorax-Hemothorax during Induction of General Anaesthesia

Tension pneumothorax during general anaesthesia is a rare but possibly deleterious event, especially where predisposing factors are absent or unknown, making diagnosis even challenging. We describe a case of a healthy middle-aged woman, who was planned to receive general anaesthesia for total thyroidectomy. After intubation, the patient experienced marked hypoxemia (SpO2=75%), hypotension, and tachycardia. Manual positive pressure ventilation seemed to worsen hypoxemia and tachycardia, while apnoeic oxygenation through circle system with valve open slightly improved cardiorespiratory collapse. The effect of positive ventilation, along with the absence of breath sounds in the right hemithorax and cardiorespiratory collapse, established the diagnosis of tension pneumothorax, managed immediately with emergency thoracentesis and placement of a thoracostomy tube. The patient was improved and pneumothorax was confirmed with chest X-ray and CT. The latter also confirmed the presence of bilateral multiple bullae. The operation was postponed and the patient was extubated a few hours later, in good condition. After thorough evaluation for any systemic disease, which was negative, the patient underwent two-stage thoracotomy for bullectomy.

Predictive Virtual Patient Modelling of Mechanical Ventilation: Impact of Recruitment Function

Mechanical ventilation is a life-support therapy for intensive care patients suffering from respiratory failure. To reduce the current rate of ventilator-induced lung injury requires ventilator settings that are patient-, time-, and disease-specific. A common lung protective strategy is to optimise the level of positive end-expiratory pressure (PEEP) through a recruitment manoeuvre to prevent alveolar collapse at the end of expiration and to improve gas exchange through recruitment of additional alveoli. However, this process can subject parts of the lung to excessively high pressures or volumes. This research significantly extends and more robustly validates a previously developed pulmonary mechanics model to predict lung mechanics throughout recruitment manoeuvres. In particular, the process of recruitment is more thoroughly investigated and the impact of the inclusion of expiratory data when estimating peak inspiratory pressure is assessed. Data from the McREM trial and CURE pilot trial were used to test model predictive capability and assumptions. For PEEP changes of up to and including 14 cmH₂O, the parabolic model was shown to improve peak inspiratory pressure prediction resulting in less than 10% absolute error in the CURE cohort and 16% in the McREM cohort. The parabolic model also better captured expiratory mechanics than the exponential model for both cohorts.

Fatal bilateral pneumothorax and generalized emphysema following contraindicated speaking-valve application

We report a case of a contraindicated attachment of a speaking valve to a tracheal tube with an inflated cuff, which rapidly resulted in the patient's death. The attached one-way valve allowed unrestrained inspiration through the tracheal tube but prevented physiological expiration. The increased pulmonary pressure resulted in alveolar rupture and replaced expiration with a steady release of air into the peribronchial sheaths and the mediastinum, resulting in what is commonly known as the Macklin effect. From the mediastinum, air inflated both pleural cavities, the peritoneum, and the subcutaneous tissue of the entire body. No gas was found in the blood vessels, the brain, the bones, or in the inner organs. The entire air volume was estimated by radiological segmentation to be more than 25 l. This implies continuous inspiration, while expiration turned into an aberrant pulmonary decompression by whole-body gas-enclosure. Death ultimately resulted from asphyxia following bilateral (tension) pneumothorax.

Bilateral pneumothorax after general anesthesia in patient with pleomorphic sarcoma of soft tissue

The occurrence of a pneumothorax using supraglottic device is a rare complication during general anesthesia. Moreover, less than 2% of pneumothoraxes can be related to lung metastases, most due to soft tissue sarcoma. We present the case of a 45-year-old female diagnosed with metastatic sarcoma who developed a bilateral pneumothorax after general anesthesia with supraglottic device. Different causes of pneumothorax were discussed.

What links ventilator driving pressure with survival in the acute respiratory distress syndrome? A computational study

Background

Recent analyses of patient data in acute respiratory distress syndrome (ARDS) showed that a lower ventilator driving pressure was associated with reduced relative risk of mortality. These findings await full validation in prospective clinical trials.

Methods

To investigate the association between driving pressures and ventilator induced lung injury (VILI), we calibrated a high fidelity computational simulator of cardiopulmonary pathophysiology against a clinical dataset, capturing the responses to changes in mechanical ventilation of 25 adult ARDS patients. Each of these in silico patients was subjected to the same range of values of driving pressure and positive end expiratory pressure (PEEP) used in the previous analyses of clinical trial data. The resulting effects on several physiological variables and proposed indices of VILI were computed and compared with data relating ventilator settings with relative risk of death.

Results

Three VILI indices: dynamic strain, mechanical power and tidal recruitment, showed a strong correlation with the reported relative risk of death across all ranges of driving pressures and PEEP. Other variables, such as alveolar pressure, oxygen delivery and lung compliance, correlated poorly with the data on relative risk of death.

Conclusions

Our results suggest a credible mechanistic explanation for the proposed association between driving pressure and relative risk of death. While dynamic strain and tidal recruitment are difficult to measure routinely in patients, the easily computed VILI indicator known as mechanical power also showed a strong correlation with mortality risk, highlighting its potential usefulness in designing more protective ventilation strategies for this patient group.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-0990-5) contains supplementary material, which is available to authorized users.

A Case of Pneumomediastinum and Pneumoperitoneum with Concurrent Massive Subcutaneous Emphysema due to Repositioning of a Tracheostomy Tube

Tracheostomy is a common procedure seen in critically ill patients that require long term ventilatory support. As with all airway access procedures, tracheotomy with prolonged tracheal tube placement comes with possible risks such as tracheal scarring, tracheal rupture, pneumothorax, tracheoesophageal fistula among others. Another possible complication, though rare, is escape of free air into the surrounding tissue, as well as pneumomediastinum (PM). This may occur due to various reasons, some of them being tracheal rupture, barotrauma or tracheal tube mispositioning. Pneumomediastinum may present with concurrent free air in other body cavities such as the peritoneum, thorax or subcutaneous tissue. Though often not life-threatening it may require treatment including high flow oxygen, ventilator management or occasionally, surgical intervention. Herein we describe a rare case of PM with communicating pneumoperitoneum and massive subcutaneous emphysema due to tracheal tube mispositioning along with a review of the literature.

A successful surgical repair of intraoperative pneumothorax and the diffuse dissection of visceral pleura during liver transplantation surgery via trans-diaphragmatic approach

BACKGROUND

Pneumothorax during surgery under general anesthesia is a life-threatening situation for the patient because it can progress easily to the tension pneumothorax due to positive pressure ventilation unless appropriate treatments such as inserting a drainage tube in the thoracic cavity are initiated. The authors experienced a case of intraoperative pneumothorax and the diffuse dissection of visceral pleura during liver transplantation surgery, and achieved successful repair by a trans-diaphragmatic approach without changing patient's body position.

CASE PRESENTATION

A 66-year-old male with multiple liver and renal cysts caused by autosomal dominant polycystic kidney disease (ADPKD) was admitted to the authors' hospital for treating the infection of the liver cysts. The infection was unable to be controlled by conservative treatments. Therefore, the patient was planned to undergo living-donor liver transplantation. Intraoperatively, the liver was found to swell markedly and to firmly adhere to the right diaphragm. After the extraction of the liver, because the right diaphragm swelled markedly, pneumothorax was suspected. Chest tube was inserted immediately, and the small incision was made in the right diaphragm. Thoracoscopic observation revealed that (1) the visceral pleura of the bottom of the right lung widely expanded like a giant cyst due to the dissection from the lung parenchyma and (2) a large air leakage from a pin hole appeared in the dissected pleura. After the completion of the liver transplantation, the thoracoscopic leakage-closing operation was performed through the right diaphragm incision. Because the dissection of visceral pleura was too wide to perform plication or cystectomy by a stapler or sutures, the dissected pleura was opened, and absorbable fibrin sealant patches and fibrin glue were put or injected between the lung parenchyma and the pleura. Although, after being observed postoperatively, prolonged minor air leakage disappeared by a conservative drainage treatment, and the cyst on the bottom of the right lung disappeared on chest computed tomography (CT).

CONCLUSIONS

Although intraoperative pneumothorax and broad dissection of visceral pleura during laparotomy is a complicated situation, the authors successfully repaired air leakage via a trans-diaphragmatic approach without changing the patient's body position.

The future of mechanical ventilation: lessons from the present and the past

The adverse effects of mechanical ventilation in acute respiratory distress syndrome (ARDS) arise from two main causes: unphysiological increases of transpulmonary pressure and unphysiological increases/decreases of pleural pressure during positive or negative pressure ventilation. The transpulmonary pressure-related side effects primarily account for ventilator-induced lung injury (VILI) while the pleural pressure-related side effects primarily account for hemodynamic alterations. The changes of transpulmonary pressure and pleural pressure resulting from a given applied driving pressure depend on the relative elastances of the lung and chest wall. The term ‘volutrauma’ should refer to excessive strain, while ‘barotrauma’ should refer to excessive stress. Strains exceeding 1.5, corresponding to a stress above ~20 cmH₂O in humans, are severely damaging in experimental animals. Apart from high tidal volumes and high transpulmonary pressures, the respiratory rate and inspiratory flow may also play roles in the genesis of VILI. We do not know which fraction of mortality is attributable to VILI with ventilation comparable to that reported in recent clinical practice surveys (tidal volume ~7.5 ml/kg, positive end-expiratory pressure (PEEP) ~8 cmH₂O, rate ~20 bpm, associated mortality ~35%). Therefore, a more complete and individually personalized understanding of ARDS lung mechanics and its interaction with the ventilator is needed to improve future care. Knowledge of functional lung size would allow the quantitative estimation of strain. The determination of lung inhomogeneity/stress raisers would help assess local stresses; the measurement of lung recruitability would guide PEEP selection to optimize lung size and homogeneity. Finding a safety threshold for mechanical power, normalized to functional lung volume and tissue heterogeneity, may help precisely define the safety limits of ventilating the individual in question. When a mechanical ventilation set cannot be found to avoid an excessive risk of VILI, alternative methods (such as the artificial lung) should be considered.

Driving pressure and mechanical power: new targets for VILI prevention

Several factors have been recognized as possible triggers of ventilator-induced lung injury (VILI). The first is pressure (thus the 'barotrauma'), then the volume (hence the 'volutrauma'), finally the cyclic opening-closing of the lung units ('atelectrauma'). Less attention has been paid to the respiratory rate and the flow, although both theoretical considerations and experimental evidence attribute them a significant role in the generation of VILI. The initial injury to the lung parenchyma is necessarily mechanical and it could manifest as an unphysiological distortion of the extracellular matrix and/or as micro-fractures in the hyaluronan, likely the most fragile polymer embedded in the matrix. The order of magnitude of the energy required to break a molecular bond between the hyaluronan and the associated protein is 1.12×10^-16 Joules (J), 70-90% higher than the average energy delivered by a single breath of 1L assuming a lung elastance of 10 cmH₂O/L (0.5 J). With a normal statistical distribution of the bond strength some polymers will be exposed each cycle to an energy large enough to rupture. Both the extracellular matrix distortion and the polymer fractures lead to inflammatory increase of capillary permeability with edema if a pulmonary blood flow is sufficient. The mediation analysis of higher vs. lower tidal volume and PEEP studies suggests that the driving pressure, more than tidal volume, is the best predictor of VILI, as inferred by increased mortality. This is not surprising, as both tidal volume and respiratory system elastance (resulting in driving pressure) may independently contribute to the mortality. For the same elastance driving pressure is a predictor similar to plateau pressure or tidal volume. Driving pressure is one of the components of the mechanical power, which also includes respiratory rate, flow and PEEP. Finding the threshold for mechanical power would greatly simplify assessment and prevention of VILI.

Rapid Reduction of Oxygenation Index by Employment of a Recruitment Technique in Patients with Severe ARDS

Mechanical ventilation of patients with acute respiratory distress syndrome (ARDS) may contribute to pulmonary injury and systemic inflammation. The objective of this study was to examine the safety and efficacy of a recruitment maneuver that rapidly improves atelectasis and oxygenation, and in so doing may reduce the potential for ventilator-induced lung injury. Nineteen patients with severe ARDS (defined as PaO2: FiO2 ≤ 150) from diverse etiologies were turned prone and a positive pressure of 40 cmH2O was applied for a period of 90 seconds. This pressure was increased in 5 cmH2O increments in subsequent maneuvers to a maximum of 50 cmH2O if there was an inadequate initial response. Subsequently pressure-limited mechanical ventilation with a PEEP of 15 cmH2O was instituted to prevent derecruitment. Peak pressures were maintained at ≤35 cmH2O. Outcome measures were oxygenation index, PaO2: FiO2 ratio, and alveolar-arterial oxygen difference. The oxygenation index decreased from a median of 31 cmH2O/mmHg to 14 cmH2O/mmHg immediately after recruitment and to 11 cmH2O/mmHg (p < 0.0001) 24 hours later. The A-aDO2 improved from 454 mmHg to 128 mmHg (p < 0.0001) and the PaO2:FiO2 ratio from 75 to 218 (p < 0.0001) 24 hours later. Twenty-five percent of patients had PaO2:FiO2 ratios of more than 300 mmHg at 24 hours. Mean airway pressure increased by 3 cmH2O initially, from 23 cmH2O to 26 cmH2O as a consequence of the increase in PEEP, but this had decreased to 25 cmH2O after 24 hours. There were no significant complications. Rapid reductions in FiO2 can be achieved safely by the implementation of a relatively simple recruitment technique.

Development of an integrated model of cardiovascular and pulmonary physiology for the evaluation of mechanical ventilation strategies

We describe the development of an integrated cardiovascular and pulmonary model for use in the investigation of novel mechanical ventilation strategies in the intensive care unit. The cardiac model includes the cardiac chambers, the pulmonary circulation and the systemic circulation. The modeling of complex mechanisms for vascular segments, time varying elastance functions of cardiovascular components and the effect of vascular resistances, in health and disease under the influence of mechanical ventilation is investigated. The resulting biomedical simulator can aid in understanding the underlying pathophysiology of critically-ill patients and facilitate the development of more effective therapeutic strategies for evaluation in clinical trials.

Radiology in the Intensive Care Unit (Part 2)

This review of intensive care unit (ICU) radiology has been divided into two sections. In Part 1, previously published, the discussion focused on the role of the portable radiograph in the evaluation of the critically ill patient and the impact of the introduction of digital radiography and picture-archiving communications systems on patient care. Part 2 of this review will emphasize the role of computed tomography and the increasing contribution of image-guided interventional procedures in patient management. The deleterious effects of mechanical ventilation due to barotrauma will also be discussed.

Mechanical Power and Development of Ventilator-induced Lung Injury

Background

The ventilator works mechanically on the lung parenchyma. The authors set out to obtain the proof of concept that ventilator-induced lung injury (VILI) depends on the mechanical power applied to the lung.

Methods

Mechanical power was defined as the function of transpulmonary pressure, tidal volume (TV), and respiratory rate. Three piglets were ventilated with a mechanical power known to be lethal (TV, 38 ml/kg; plateau pressure, 27 cm H2O; and respiratory rate, 15 breaths/min). Other groups (three piglets each) were ventilated with the same TV per kilogram and transpulmonary pressure but at the respiratory rates of 12, 9, 6, and 3 breaths/min. The authors identified a mechanical power threshold for VILI and did nine additional experiments at the respiratory rate of 35 breaths/min and mechanical power below (TV 11 ml/kg) and above (TV 22 ml/kg) the threshold.

Results

In the 15 experiments to detect the threshold for VILI, up to a mechanical power of approximately 12 J/min (respiratory rate, 9 breaths/min), the computed tomography scans showed mostly isolated densities, whereas at the mechanical power above approximately 12 J/min, all piglets developed whole-lung edema. In the nine confirmatory experiments, the five piglets ventilated above the power threshold developed VILI, but the four piglets ventilated below did not. By grouping all 24 piglets, the authors found a significant relationship between the mechanical power applied to the lung and the increase in lung weight (r2 = 0.41, P = 0.001) and lung elastance (r2 = 0.33, P &lt; 0.01) and decrease in Pao2/Fio2 (r2 = 0.40, P &lt; 0.001) at the end of the study.

Conclusion

In piglets, VILI develops if a mechanical power threshold is exceeded.