Human cytomegalovirus seropositivity is associated with reduced patient survival during sepsis

BACKGROUND

Sepsis is one of the leading causes of death. Treatment attempts targeting the immune response regularly fail in clinical trials. As HCMV latency can modulate the immune response and changes the immune cell composition, we hypothesized that HCMV serostatus affects mortality in sepsis patients.

METHODS

We determined the HCMV serostatus (i.e., latency) of 410 prospectively enrolled patients of the multicenter SepsisDataNet.NRW study. Patients were recruited according to the SEPSIS-3 criteria and clinical data were recorded in an observational approach. We quantified 13 cytokines at Days 1, 4, and 8 after enrollment. Proteomics data were analyzed from the plasma samples of 171 patients.

RESULTS

The 30-day mortality was higher in HCMV-seropositive patients than in seronegative sepsis patients (38% vs. 25%, respectively; p = 0.008; HR, 1.656; 95% CI 1.135-2.417). This effect was observed independent of age (p = 0.010; HR, 1.673; 95% CI 1.131-2.477). The predictive value on the outcome of the increased concentrations of IL-6 was present only in the seropositive cohort (30-day mortality, 63% vs. 24%; HR 3.250; 95% CI 2.075-5.090; p < 0.001) with no significant differences in serum concentrations of IL-6 between the two groups. Procalcitonin and IL-10 exhibited the same behavior and were predictive of the outcome only in HCMV-seropositive patients.

CONCLUSION

We suggest that the predictive value of inflammation-associated biomarkers should be re-evaluated with regard to the HCMV serostatus. Targeting HCMV latency might open a new approach to selecting suitable patients for individualized treatment in sepsis.

[Application of artificial intelligence systems in the emergency room : Do the communication patterns give indications for possible starting points? An observational study]

BACKGROUND

High expectations are currently attached to the application of artificial intelligence (AI) in the resuscitation room treatment of trauma patients with respect to the development of decision support systems. No data are available regarding possible starting points for AI-controlled interventions in resuscitation room treatment.

OBJECTIVE

Do information request behavior and quality of communication indicate possible starting points for AI applications in the emergency room?

MATERIAL AND METHODS

A 2‑stage qualitative observational study: 1. Development of an observation sheet based on expert interviews that depicts the following six relevant topics: situational factors (course of accident, environment), vital parameters, treatment-specific Information (treatment carried out). trauma-specific factors (injury patterns), medication, special features of the patient (anamnesis, etc.) 2. Observational study Which topics were inquired about during emergency room treatment? Was the exchange of information complete?

RESULTS

There were 40 consecutive observations in the emergency room. A total of 130 questions: 57/130 inquiries about medication/treatment-specific Information and vital parameters, 19/28 of which were inquiries about medication. Questions about injury-related parameters 31/130 with 18/31 regarding injury patterns, course of accident (8/31) and type of accident (5/31). Questions about medical or demographic background 42/130. Within this group, pre-existing illnesses (14/42) and demographic background (10/42) were the most frequently asked questions. Incomplete exchange of information was found in all six subject areas.

CONCLUSION

Questioning behavior and incomplete communication indicate a cognitive overload. Assistance systems that prevent cognitive overload can maintain decision-making abilities and communication skills. Which AI methods can be used requires further research.

A New Approach in Airway Management for Tracheal Resection and Anastomosis: A Single-Center Prospective Study

OBJECTIVES

The evaluation of the use of laryngeal mask airways (LMA) as an alternative form of airway management for surgical tracheal reconstruction.

DESIGN

A prospective case series.

SETTING

At a single German university hospital.

PARTICIPANTS

Ten patients.

INTERVENTIONS

The use of LMA for airway management in surgical reconstruction of the trachea.

MEASUREMENTS AND MAIN RESULTS

Ten patients with tracheal stenosis of 50% to 90% were enrolled prospectively during the study period. The airway management consisted of the insertion of an LMA. During resection and reconstruction, high-frequency jet ventilation was used. Several arterial blood gas analyses (ABG) were performed before, during, and after the tracheal resection and reconstruction. All values were presented as median and interquartile ranges or as absolute and relative values, and no emergency change to cross-field intubation was necessary. The lowest PaO₂ was 93 mmHg in 1 patient after 20 minutes of jet ventilation, whereas PaO₂ increased after the induction phase and remained stable in 9 patients. There were no intraoperative complications related to anesthetic management apart from transient hypercarbia during and after jet ventilation. Preoperative and postoperative ABG were comparable. One patient required immediate postoperative ventilatory support. Two patients developed postoperative pneumonia, leading to their admission to the intensive care unit. One patient was operated with a palliative approach due to massive dyspnea and died in the next postoperative course.

CONCLUSIONS

The use of LMA is an alternative option in airway management for tracheal reconstruction, even in patients with significant tracheal stenosis. Potential advantages compared to tracheal intubation are unimpaired access to the operative field and the lack of stress on the fresh anastomosis.

Anesthesia for tracheal and carinal resection and reconstruction

PURPOSE OF REVIEW

The aim of this review is to provide an overview of current anesthetic management of tracheal and carinal resection and reconstruction.

RECENT FINDINGS

In addition to the traditional anesthetic approach using conventional tracheal intubation after induction of general anesthesia and cross-field intubation or jet-ventilation once the airway has been surgically opened, there is a trend toward less invasive anesthetic procedures. Regional anesthetic techniques and approaches focusing on the maintenance of spontaneous respiration have emerged. Especially for cervical tracheal stenosis, laryngeal mask airways appear to be an advantageous alternative to tracheal intubation.Extracorporeal support can ensure adequate gas exchange and/or perfusion during complex resections and reconstructions without interference of airway devices with the operative field. It also serves as an effective rescue technique in case other approaches fail.

SUMMARY

The spectrum of available anesthetic techniques for major airway surgery is immense. To find the safest approach for the individual patient, comprehensive interdisciplinary planning is essential. The location and anatomic consistency of the stenosis, comorbidities, the functional status of respiratory system, as well as the planned reconstructive technique need to be considered. Until more data is available, however, a reliable evidence-based comparison of different approaches is not possible.

Current practice of thoracic anaesthesia in Europe - a survey by the European Society of Anaesthesiology Part I - airway management and regional anaesthesia techniques

Background

The scientific working group for “Anaesthesia in thoracic surgery” of the German Society of Anaesthesiology and Intensive Care Medicine (DGAI) has performed an online survey to assess the current standards of care and structural properties of anaesthesia workstations in thoracic surgery.

Methods

All members of the European Society of Anaesthesiology (ESA) were invited to participate in the study.

Results

Thoracic anaesthesia was most commonly performed by specialists/board-certified anaesthetists and/or senior/attending physicians. Across Europe, the double lumen tube (DLT) was most commonly chosen as the primary device for lung separation (461/ 97.3%). Bronchial blockers were chosen less frequently (9/ 1.9%).

Throughout Europe, bronchoscopy was not consistently used to confirm correct double lumen tube positioning. Respondents from Eastern Europe (32/ 57.1%) frequently stated that there were not enough bronchoscopes available for every intrathoracic operation. A specific algorithm for difficult airway management in thoracic anaesthesia was available to only 18.6% (n = 88) of the respondents. Thoracic epidural analgesia (TEA) is the most commonly used form of regional analgesia for thoracic surgery in Europe. Ultrasonography was widely available 93,8% (n = 412) throughout Europe and was predominantly used for central line placement and lung diagnostics.

Conclusions

While certain „gold standards “are widely met, there are also aspects of care requiring substantial improvement in thoracic anaesthesia throughout Europe.

Our data suggest that algorithms and standard operating procedures for difficult airway management in thoracic anaesthesia need to be established. A European recommendation for the basic requirements of an anaesthesia workstation for thoracic anaesthesia is expedient and desirable, to improve structural quality and patient safety.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01480-w.

Most patient conditions do not a priori debilitate the sensitivity of thoracic ultrasound in thoracic surgery-a prospective comparative study

Background

The few existing studies on the accuracy of lung ultrasound in the detection of a postoperative pneumothorax after thoracic surgery differ in the sonographic technique and the inclusion criteria. Several conditions are considered unfavourable in the sonographic examination of the lung. We aim to test these conditions for their impact on the diagnostic accuracy of lung ultrasound.

Methods

We compared lung ultrasound and chest roentgenograms for the detection of a pneumothorax after lung-resecting surgery in two prospective trials (register ID DRKS00014557 and DRKS00020216). The ultrasound examiners and radiologists were blinded towards the corresponding findings. We performed posthoc subgroup analyses to determine the influence of various patient or surgery related conditions on the sensitivity and specificity of ultrasound in the detection of pneumothorax.

Results

We performed 340 examinations in 208 patients. The covariates were age, gender, body mass index, smoking status, severity of chronic obstructive pulmonary disease, previous ipsilateral operation or irradiation, thoracotomy, postoperative skin emphysema, indwelling chest tube and X-ray in supine position. In univariate analysis, an indwelling chest-tube was associated with a higher sensitivity (58%, p = 0.04), and a postoperative subcutaneous emphysema with a lower specificity (73% vs. 88%, p = 0.02). None of the other subgroups differed in sensitivity or specificity from the total population .

Conclusions

Most of the patient- or surgery related conditions usually considered unfavourable for lung ultrasound did not impair the sensitivity or specificity of lung ultrasound. Further studies should not excluce patients with these conditions, but test the accuracy under routine conditions.

Trial registration

DRKS, DRKS00014557, registered 06/09/2018, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00014557 and DRKS00020216, registered 03/12/2019, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00020216

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-021-01454-6.

Use of Extracorporeal Membrane Oxygenation for Major Cardiopulmonary Resections

BACKGROUND

In thoracic surgery, utilization of extracorporeal membrane oxygenation (ECMO) is mainly established for patients undergoing lung transplantation. The aim of our study was to summarize our single-center experience with intraoperative use of veno-venous- or veno-arterial-ECMO in patients undergoing complex lung surgery involving the main carina, or the left atrium or the descending aorta.

METHODS

A total of 24 patients underwent combined complex lung, carinal, aortal, or left atrial resections. In cases of carinal resection, percutaneous veno-venous, jugular-femoral cannulation was considered suitable. For combined resection of lung and descending aorta, a percutaneous femoral veno-arterial cannulation was used. In cases of extended left atrial resection, a percutaneous jugular-femoral veno-venous-arterial cannulation was favored.

RESULTS

Procedures were divided into three groups: carinal resections and reconstruction (n = 8), resections of the descending aorta and left lung (n = 7), resections of lung and left atrium (n = 9). No intraoperative complications occurred. Overall 30-day mortality was 25%. A complete resection was achieved in 18 patients. Median survival was 12 months. One- and 5-year survival were 48.1 and 22.7%, respectively.

CONCLUSION

The present study shows that intraoperative use of ECMO for extended carinal, aortic, or atrial resections is feasible with minimal intraoperative complications allowing surgeons increased operating-field safety. Perioperative mortality is high, but this is rather an attribute of local extended disease and patient comorbidities.

Impact of blunt chest trauma on outcome after traumatic brain injury- a matched-pair analysis of the TraumaRegister DGU®

Background

Traumatic brain injury (TBI) is associated with high rates of long-term disability and mortality. Our aim was to investigate the effects of thoracic trauma on the in-hospital course and outcome of patients with TBI.

Methods

We performed a matched pair analysis of the multicenter trauma database TraumaRegisterDGU® (TR-DGU) in the 5-year period from 2012 to 2016. We included adult patients (≥18 years of age) with moderate to severe TBI (abbreviated injury scale (AIS)= 3–5). Patients with isolated TBI (group 1) were compared to patients with TBI and varying degrees of additional blunt thoracic trauma (AIS_Thorax= 2–5) (group 2). Matching criteria were gender, age, severity of TBI, initial GCS and presence/absence of shock. The χ²-test was used for comparing categorical variables and the Mann-Whitney-U-test was chosen for continuous parameters. Statistical significance was defined by a p-value < 0.05.

Results

A total of 5414 matched pairs (10,828 patients) were included. The presence of additional thoracic injuries in patients with TBI was associated with a longer duration of mechanical ventilation and a prolonged ICU and hospital length of stay. Additional thoracic trauma was also associated with higher mortality rates. These effects were most pronounced in thoracic AIS subgroups 4 and 5. Additional thoracic trauma, regardless of its severity (AIS_Thorax ≥2) was associated with significantly decreased rates of good neurologic recovery (GOS = 5) after TBI.

Conclusions

Chest trauma in general, regardless of its initial severity (AIS_Thorax= 2–5), is associated with decreased chance of good neurologic recovery after TBI. Affected patients should be considered “at risk” and vigilance for the maintenance of optimal neuro-protective measures should be high.

Continuous lateral rotational therapy in thoracic trauma--A matched pair analysis

INTRODUCTION

Given the lack of reliable evidence on the utility of continuous lateral rotational therapy (CLRT) in chest trauma, we performed a single-centre retrospective matched-pair analysis of patients treated either with CLRT or non-continuous manual turning after blunt thoracic trauma.

METHODS

We included adult patients that were admitted to our level 1 trauma centre from 2010-2014 and presented with severe thoracic injuries (AISThorax ≥3) within 24 h after the injury and required at least 72 h of mechanical ventilation. Patients were either treated with manual turning every 2-4 h or CLRT. To ensure comparable injury severity and a similar risk for posttraumatic respiratory complications, we matched for thoracic injury severity, age, additional injuries (head, abdomen, extremities) and need for massive transfusion.

RESULTS

A total of 22 pairs (n = 44 patients) were successfully matched and analysed. The use of CLRT did not have a statistically significant impact on respiratory function, gas exchange, duration of mechanical ventilation, ICU or hospital length of stay, or overall patient outcomes (e.g. pneumonia, sepsis, ARDS, mortality). During active rotation the level of sedation was lower compared to manual turning (Richmond Agitation Sedation Scale; manual turning: -3.6; CLRT: -4.0; p = 0.01). Patient agitation was noticed more frequently in the CLRT group (manual turning: n = 2 (9%); CLRT: n = 9 (41%); p = 0.02).

DISCUSSION

In this well-matched sample, the use of CLRT did not seem to translate into relevant clinical benefits in patients with thoracic trauma in the setting of modern ICU care with the widespread implementation of lung protective ventilation. However, statistical power and generalisability were limited by the small sample size and single centre design. A large RCT is required to provide conclusive results.

Comparison of forces acting on maxillary incisors during tracheal intubation with different laryngoscopy techniques: a blinded manikin study

Dental trauma is a common complication of tracheal intubation. As existing evidence is insufficient to validly assess the impact of different laryngoscopy techniques on the incidence of dental trauma, the force exerted onto dental structures during tracheal intubation was investigated. An intubation manikin was equipped with hidden force sensors in all maxillary incisors. Dental force was measured while 104 anaesthetists performed a series of tracheal intubations using direct laryngoscopy with a Macintosh blade, and videolaryngoscopy with a C-MAC^® , or the hyperangulated GlideScope^® or KingVision^® laryngoscopes in both normal and difficult airway conditions. A total of 624 tracheal intubations were analysed. The median (IQR [range]) peak force of direct laryngoscopy in normal airways was 21.1 (14.0-32.8 [2.3-127.6]) N and 29.3 (17.7-44.8 [3.3-97.2]) N in difficult airways. In normal airways, these were lower with the GlideScope and KingVision hyperangulated laryngoscopes, with a reduction of 4.6 N (p = 0.006) and 10.9 N (p < 0.001) compared with direct laryngoscopy, respectively. In difficult airways, these were lower with the GlideScope and KingVision hyperangulated laryngoscopes, with a reduction of 9.8 N (p < 0.001) and 17.6 N (p < 0.001) compared with direct laryngoscopy, respectively. The use of the C-MAC did not have an impact on the median peak force. Although sex of anaesthetists did not affect peak force, more experienced anaesthetists generated a higher peak force than less experienced providers. We conclude that hyperangulated videolaryngoscopy was associated with a significantly decreased force exerted on maxillary incisors and might reduce the risk for dental injury in clinical settings.

Anterior Chest Wall Reconstruction Using Polypropylene Mesh: A Retrospective Study

Background Anterior chest wall resection for oncological purposes is usually combined with a form of reconstruction. Most surgeons are convinced that ventrally located defects more than 4 to 5 cm require adequate reconstruction to minimize the risk of lung herniation and respiratory distress through paradox motion. We describe our in-house results of ventral chest wall reconstruction using polypropylene mesh without the use of metallic or biological implants regardless of the extent of chest wall resection.

Methods Patient selection involved ventral chest wall resection and reconstruction by polypropylene mesh for all indications such as primary tumors, metastasis, or infiltration by lung cancer from January 2008 to December 2016. Primary end point was the difference between both sides. Secondary end points were postoperative complications such as infection, surgical revision, and pulmonary complications.

Results Forty-five cases of isolated anterior reconstruction could be identified. In 34 cases, postoperative computed tomography scan of the thorax was available. Fifteen males and 19 females with a median age of 70.5 years were operated. The evaluation of maximum hemithorax diameter between operated and nonoperated sides was documented in centimeters, and the difference was documented in percentage. The mean percentage difference was 11.1% (minimum: 0.3, maximum: 44.4). In one case, wound infection with positive culture could not be treated conservatively and required operative revision and removal of the polypropylene mesh.

Conclusion Polypropylene mesh, though not rigid, can safely be used for anterior chest wall reconstruction.

Impact of body mass index on outcomes after thoracic trauma-A matched-triplet analysis of the TraumaRegister DGU®

INTRODUCTION

Chest trauma and obesity are both associated with increased risks for respiratory complications (e.g. hypoxia, hypercarbia, pneumonia), which are frequent causes of posttraumatic morbidity and mortality. However, as there is only limited and inconsistent evidence, the aim of our study was to analyse the effect of body mass index (BMI) on patient outcomes after thoracic trauma.

PATIENTS AND METHODS

We screened 50.519 patients entered in TraumaRegister DGU^®, between 2004-2009, when the BMI was part of the standardized dataset. After matching for injury patterns and severity of trauma we performed a matched tripled analysis with regard to the BMI (group 1: <25.0 kg/m²; group 2: 25.0-29.9 kg/m²; group 3: >30.0 kg/m²). Data are shown as percentages and mean values with standard deviation.

RESULTS

The matching process yielded a cohort of 828 patients with serious blunt thoracic trauma, evenly distributed over the 3 BMI groups (276 triplets). BMI did not have an impact on the need for prehospital or emergency department interventions. There was a trend towards more liberal use of whole-body-CT scanning with increasing BMI (group 1: 68.8%; group 2: 73.2%; group 3: 75.0%). Additional abdominal injuries were more common in normal weight patients (Group 1: 28.3%; Group 2: 14.9%; Group 3: 17.8%). Obesity (BMI > 30.0 kg/m²) had a significant impact on the duration of mechanical ventilation (in days; group 1: 6.5 (9.4); group 2: 6.4 (8.9); group 3: 9.1 (14.4); p = 0.002), ICU days (in days; group 1: 11.5 (11.5); group 2: 10.9 (9.6); group 3: 14.1 (16.7); p = 0.005) and hospital length of stay (in days; group 1: 27.8 (19.3); group 2: 27.4 (19.2); group 3: 32.2 (25.9); p = 0.009). There were no significant differences regarding overall mortality (group 1: 3.6%; group 2: 1.8%; group 3: 4.0%; p = 0.26).

CONCLUSIONS

Obesity has a negative impact on outcomes after blunt chest trauma, as it is associated with prolonged duration of mechanical ventilation, ICU and hospital length of stay. Mortality did not seem to be affected, yet, further research is required to confirm these results in a larger cohort.

[Anesthesia problem cards-indispensable yet problematic : Nationwide survey on experiences from clinical practice]

BACKGROUND

Anesthetic procedures may lead to severe and potentially life-threatening complications (e. g. difficult airway, allergic reactions, malignant hyperthermia). Most complications can be avoided in future anesthetic procedures with adequate preparation (e. g. awake intubation, trigger-free anesthesia). In Germany, anesthesia problem cards were introduced two decades ago to identify patients at risk and to increase patient safety by creating a standardized documentation system for anesthesia-related complications. The purpose of our study was to evaluate the utility and problems of anesthesia problem cards in clinical practice.

MATERIAL AND METHODS

All registered members of the German Society of Anesthesiology and Intensive Care Medicine (DGAI) and the Professional Association of German Anesthesiologists (BDA) (n = 19,042) were invited to participate in an online survey on patient safety. A subsection of the survey focused specifically on anesthesia problem cards and their utility in clinical practice (e. g. field of application, issuing procedures, benefits and problems).

RESULTS

The survey subsection on anesthesia problem cards was completed by 1783 participants. Most agreed that anesthesia problem cards are a useful tool to increase patient safety (n = 1502; 84.2%) and that they are routinely issued after the occurrence of anesthesia-related complications (n = 1664, 93.4%). One of the major problems noted was that patients frequently forget to bring their anesthesia problem cards when presenting for the preanesthetic assessment. This was observed by 1457 participants (81.7%). Furthermore, the information provided on anesthesia problem cards may be inadequately phrased (n = 874; 49.0%) or illegible (n = 833; 46.7%). In addition, the space for individual comments or problem solutions is insufficient (n = 811; 45.5%). Replacements for lost anesthesia problem cards with identical informational content can be issued in only 41.9% (n = 747) of the participants' departments.

CONCLUSION

Anesthesia problem cards are considered a useful tool to increase patient safety and are frequently issued in clinical practice; however, in the document's current form its full potential for risk minimization cannot be exploited. Structural changes are required to increase documentation quality and reproducibility. Concerning its informational content, the spectrum of included complications and their individual solutions need to be expanded to meet the requirements of modern anesthetic practice.

New Approaches to Airway Management in Tracheal Resections-A Systematic Review and Meta-analysis

OBJECTIVES

Although endotracheal intubation, surgical crossfield intubation, and jet ventilation are standard techniques for airway management in tracheal resections, there are also reports of new approaches, ranging from regional anesthesia to extracorporeal support. The objective was to outline the entire spectrum of new airway techniques.

DESIGN

The literature databases PubMed/Medline and the Cochrane Library were searched systematically for prospective and retrospective trials as well as case reports on tracheal resections.

SETTING

No restrictions applied to hospital types or settings.

PARTICIPANTS

Adult patients undergoing surgical resections of noncongenital tracheal stenoses with end-to-end anastomoses.

INTERVENTIONS

Airway management techniques were divided into conventional and new approaches and analyzed regarding their potential risks and benefits.

MEASUREMENTS AND MAIN RESULTS

A total of 59 publications (n = 797 patients) were included. The majority of publications (71.2%) describe conventional airway techniques. Endotracheal tube placement after induction of general anesthesia and surgical crossfield intubation after incision of the trachea were used most frequently without major complications. A total of 7 new approaches were identified, including 4 different regional anesthetic techniques (25 cases), supraglottic airways (4 cases), and new forms of extracorporeal support (25 cases). Overall failure rates of new techniques were low (1.8%). Details on patient selection and procedural specifics are provided.

CONCLUSIONS

New approaches have several theoretical benefits, yet further research is required to establish criteria for patient selection and evaluate procedural safety. Given the low level of evidence, it currently is impossible to compare methods of airway management regarding outcome-related risks and benefits.

Successful treatment of severe Clostridium difficile infection by administration of crushed fidaxomicin via a nasogastric tube in a critically ill patient

OBJECTIVE

To report the successful use of crushed fidaxomicin via a nasogastric tube for treatment of a severe Clostridium difficile infection in a critically ill patient.

DATA SOURCES

Clinical observation of a patient, images of abdominal computed tomography, antimicrobial therapy and course of infection parameters.

DATA EXTRACTION

Relevant information contained in the medical observation of the patient and selection of image and laboratory parameters performed in the patient.

DATA SYNTHESIS

We report a case of a 79-year old patient who developed septic shock with an increasing need for norepinephrine and acute renal failure due to a severe Clostridium difficile infection. Antimicrobial therapy with vancomycin via a nasogastric tube and metronidazole i.v. did not lead to improvement, infection parameters further increased, and the clinical condition became increasingly impaired. After 10 days, antimicrobial therapy was changed to fidaxomicin, crushed and administered via nasogastric tube. Within 24hours, infection parameters decreased. Further diarrhoea ceased and stool samples were negative for Clostridium difficile antigen.

CONCLUSIONS

Our case confirms that administration of fidaxomicin via a nasogastric tube was safe and effective in this patient. Further studies are needed to evaluate the efficacy of this strategy in critically ill patients systematically.

Spontaneous breathing improves lung aeration in oleic acid-induced lung injury

BACKGROUND

Experimental and clinical studies have shown reduction in intrapulmonary shunt with improved oxygenation by spontaneous breathing with airway pressure release ventilation (APRV) in acute lung injury. The mechanisms of these findings are not clear. The authors hypothesized that spontaneous breathing results in better aeration of lung tissue and that improvement in oxygenation can be explained by these changes. This hypothesis was studied in a porcine model of oleic acid-induced lung injury.

METHODS

Two hours after induction of lung injury, 24 pigs were randomly assigned to APRV with or without spontaneous breathing at a positive end-expiratory pressure of 5 cm H(2)O. Hemodynamics, spirometry, and end-expiratory lung volume by nitrogen washout were measured at baseline, after 2 h of lung injury, and after 2 and 4 h of mechanical ventilation in the specific mode. Finally, spiral computed tomography of the chest was performed at end-expiratory lung volume in 22 pigs.

RESULTS

Arterial carbon dioxide tension and mean and end-inspiratory airway pressures were comparable between settings. Four hours of APRV with spontaneous breathing resulted in improved oxygenation compared with APRV without spontaneous breathing (arterial oxygen tension, 144 +/- 65 vs. 91 +/- 50 mmHg, P < 0.01 for interaction time x mode), higher end-expiratory lung volume (786 +/- 320 vs. 384 +/- 148 ml, P < 0.001), and better aeration. End-expiratory lung volume and venous admixture were both correlated with the amount of lung reaeration (r(2) = 0.62 and r(2) = 0.61, respectively).

CONCLUSIONS

The results support the hypothesis that spontaneous breathing during APRV improves oxygenation mainly by recruitment of nonaerated lung and improved aeration of the lungs.