Should Intermittent Mandatory Ventilation Be Abolished?

Intrathoracic Pressure Regulator Performance in the Setting of Hemorrhage and Acute Lung Injury

INTRODUCTION

Intrathoracic pressure regulation (ITPR) can be utilized to enhance venous return and cardiac preload by inducing negative end expiratory pressure in mechanically ventilated patients. Previous preclinical studies have shown increased mean arterial pressure (MAP) and decreased intracranial pressure (ICP) with use of an ITPR device. The aim of this study was to evaluate the hemodynamic and respiratory effects of ITPR in a porcine polytrauma model of hemorrhagic shock and acute lung injury (ALI).

METHODS

Swine were anesthetized and underwent a combination of sham, hemorrhage, and/or lung injury. The experimental groups included: no injury with and without ITPR (ITPR, Sham), hemorrhage with and without ITPR (ITPR/Hem, Hem), and hemorrhage and ALI with and without ITPR (ITPR/Hem/ALI, Hem/ALI). The ITPR device was initiated at a setting of -3 cmH2O and incrementally decreased by 3 cmH2O after 30 minutes on each setting, with 15 minutes allowed for recovery between settings, to a nadir of -12 cmH2O. Histopathological analysis of the lungs was scored by blinded, independent reviewers. Of note, all animals were chemically paralyzed for the experiments to suppress gasping at ITPR pressures below -6 cmH2O.

RESULTS

Adequate shock was induced in the hemorrhage model, with the MAP being decreased in the Hem and ITPR/Hem group compared with Sham and ITPR/Sham, respectively, at all time points (Hem 54.2 ± 6.5 mmHg vs. 88.0 ± 13.9 mmHg, p < 0.01, -12 cmH2O; ITPR/Hem 59.5 ± 14.4 mmHg vs. 86.7 ± 12.1 mmHg, p < 0.01, -12 cmH2O). In addition, the PaO2/FIO2 ratio was appropriately decreased in Hem/ALI compared with Sham and Hem groups (231.6 ± 152.5 vs. 502.0 ± 24.6 (Sham) p < 0.05 vs. 463.6 ± 10.2, (Hem) p < 0.01, -12 cmH2O). Heart rate was consistently higher in the ITPR/Hem/ALI group compared with the Hem/ALI group (255 ± 26 bpm vs. 150.6 ± 62.3 bpm, -12 cmH2O) and higher in the ITPR/Hem group compared with Hem. Respiratory rate (adjusted to maintain pH) was also higher in the ITPR/Hem/ALI group compared with Hem/ALI at -9 and - 12 cmH2O (32.8 ± 3.0 breaths per minute (bpm) vs. 26.8 ± 3.6 bpm, -12 cmH2O) and higher in the ITPR/Hem group compared with Hem at -6, -9, and - 12 cmH2O. Lung compliance and end expiratory lung volume (EELV) were both consistently decreased in all three ITPR groups compared with their controls. Histopathologic severity of lung injury was worse in the ITPR and ALI groups compared with their respective injured controls or Sham.

CONCLUSION

In this swine polytrauma model, we demonstrated successful establishment of hemorrhage and combined hemorrhage/ALI models. While ITPR did not demonstrate a benefit for MAP or ICP, our data demonstrate that the ITPR device induced tachycardia with associated increase in cardiac output, as well as tachypnea with decreased lung compliance, EELV, PaO2/FIO2 ratio, and worse histopathologic lung injury. Therefore, implementation of the ITPR device in the setting of polytrauma may compromise pulmonary function without significant hemodynamic improvement.

Caring for Critically Ill Adults With Coronavirus Disease 2019 in a PICU: Recommendations by Dual Trained Intensivists

OBJECTIVE

In the midst of the severe acute respiratory syndrome coronavirus 2 pandemic, which causes coronavirus disease 2019, there is a recognized need to expand critical care services and beds beyond the traditional boundaries. There is considerable concern that widespread infection will result in a surge of critically ill patients that will overwhelm our present adult ICU capacity. In this setting, one proposal to add "surge capacity" has been the use of PICU beds and physicians to care for these critically ill adults.

DESIGN

Narrative review/perspective.

SETTING

Not applicable.

PATIENTS

Not applicable.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The virus's high infectivity and prolonged asymptomatic shedding have resulted in an exponential growth in the number of cases in the United States within the past weeks with many (up to 6%) developing acute respiratory distress syndrome mandating critical care services. Coronavirus disease 2019 critical illness appears to be primarily occurring in adults. Although pediatric intensivists are well versed in the care of acute respiratory distress syndrome from viral pneumonia, the care of differing aged adult populations presents some unique challenges. In this statement, a team of adult and pediatric-trained critical care physicians provides guidance on common "adult" issues that may be encountered in the care of these patients and how they can best be managed in a PICU.

CONCLUSIONS

This concise scientific statement includes references to the most recent and relevant guidelines and clinical trials that shape management decisions. The intention is to assist PICUs and intensivists in rapidly preparing for care of adult coronavirus disease 2019 patients should the need arise.

Mechanical ventilation in Spain, 1998-2016: Epidemiology and outcomes

PURPOSE

To evaluate changes in the epidemiology of mechanical ventilation in Spain from 1998 to 2016.

DESIGN

A post hoc analysis of four cohort studies was carried out.

SETTING

A total of 138 Spanish ICUs.

PATIENTS

A sample of 4293 patients requiring invasive mechanical ventilation for more than 12h or noninvasive ventilation for more than 1h.

INTERVENTIONS

None.

VARIABLES OF INTEREST

Demographic variables, reason for mechanical ventilation, variables related to ventilatory support (ventilation mode, tidal volume, PEEP, airway pressures), complications during mechanical ventilation, duration of mechanical ventilation, ICU stay and ICU mortality.

RESULTS

There was an increase in severity (SAPSII: 43 points in 1998 vs. 47 points in 2016), changes in the reason for mechanical ventilation (decrease in chronic obstructive pulmonary disease and acute respiratory failure secondary to trauma, and increase in neurological disease and post-cardiac arrest). There was an increase in noninvasive mechanical ventilation as the first mode of ventilatory support (p<0.001). Volume control ventilation was the most commonly used mode, with increased support pressure and pressure-regulated volume-controlled ventilation. A decrease in tidal volume was observed (9ml/kg actual b.w. in 1998 and 6.6ml/kg in 2016; p<0.001) as well as an increase in PEEP (3cmH₂O in 1998 and 6cmH₂O in 2016; p<0.001). In-ICU mortality decreased (34% in 1998 and 27% in 2016; p<0.001), without geographical variability (median OR 1.43; p=0.258).

CONCLUSIONS

A significant decrease in mortality was observed in patients ventilated in Spanish ICUs. These changes in mortality could be related to modifications in ventilation strategy to minimize ventilator-induced lung injury.

Invasive Mechanical Ventilation

Invasive mechanical ventilation is a potentially lifesaving intervention for acutely ill patients. The goal of this review is to provide a concise, clinically focused overview of basic invasive mechanical ventilation for the many clinicians who care for mechanically ventilated patients. Attention is given to how common ventilator modes differ in delivering a mechanical breath, evaluation of respiratory system mechanics, how to approach acute changes in airway pressure, and the diagnosis of auto-positive end-expiratory pressure. Waveform interpretation is emphasized throughout the review.

Quantification of critical care medicine: An ICU survey

BACKGROUND

The shortage in intensivist workforce has been long recognized but no solution has been identified. Meanwhile, fellowships in pulmonary and critical care medicine (PCCM) are expanding, other critical care medicine (CCM) programs are contracting. No explanation exists for this contradictory trend, although understanding contributory factors may lead to a solution for the shortage. The fundamental difference between PCCM and other CCM programs lies in the residency training of trainees. We tested the hypothesis that the nature of CCM practice determines its attractiveness to potential candidates.

METHODS

A questionnaire-based survey was administered recording all daily activities in four different kinds of ICUs at two teaching hospitals one was public, and one was private. Activities were categorized into conventional CCM, respiratory, medical, and surgical interventions.

RESULTS

The average daily census was 17.6 ± 6.6. Across two MICU, one trauma/surgical and one cardiothoracic ICU the average daily activity ranged from 152 to 203 of these CCM formed 27%-36%, respiratory 10%-13%, medical 43%-59%, and surgical 1%-15%. The combination of medical and respiratory interventions represented >50% of daily activities among all the ICUs.

CONCLUSIONS

Quantitative description of ICU activities indicates that the majority of the ICU daily practice relies on medical and respiratory interventions, which may explain why PCCM remains popular.

Modes of mechanical ventilation vary between hospitals and intensive care units within a university healthcare system: a retrospective observational study

Objective

As evidence-based guidance to aid clinicians with mechanical ventilation mode selection is scant, we sought to characterize the epidemiology thereof within a university healthcare system and hypothesized that nonconforming approaches could be readily identified. We conducted an exploratory retrospective observational database study of routinely recorded mechanical ventilation parameters between January 1, 2010 and December 31, 2016 from 12 intensive care units. Mode epoch count proportions were examined using Chi squared and Fisher exact tests as appropriate on an inter-unit basis with outlier detection for two test cases via post hoc pairwise analyses of a binomial regression model.

Results

Final analysis included 559,734 mode epoch values. Significant heterogeneity was demonstrated between individual units (P < 0.05 for all comparisons). One unit demonstrated heightened utilization of high-frequency oscillatory ventilation, and three units demonstrated frequent synchronized intermittent mandatory ventilation utilization. Assist control ventilation was the most commonly recorded mode (51%), followed by adaptive support ventilation (23.1%). Volume-controlled modes were about twice as common as pressure-controlled modes (64.4% versus 35.6%). Our methodology provides a means by which to characterize the epidemiology of mechanical ventilation approaches and identify nonconforming practices. The observed variability warrants further clinical study about contributors and the impact on relevant outcomes.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3534-z) contains supplementary material, which is available to authorized users.