Use of the impedance threshold device in cardiopulmonary resuscitation

Impedance threshold device as a countermeasure for spaceflight associated neuro-ocular syndrome (SANS): Mitigating mechanisms in proposed pathophysiology

Long-duration spaceflight (LDSF) is associated with unique hazards and linked with numerous human health risks including Spaceflight Associated Neuro-ocular Syndrome (SANS). The proposed mechanisms for SANS include microgravity induced cephalad fluid shift and increased Intracranial Pressure (ICP). SANS is a disorder seen only after LDSF and has no direct terrestrial pathologic counterpart as the zero G environment cannot be completely replicated on Earth. Head-down tilt, bed rest studies however have been used as a terrestrial analog and produce the cephalad fluid shift. Some proposed countermeasures for SANS include vasoconstrictive thigh cuffs and lower body negative pressure. Another potential researched countermeasure is the impedance threshold device (ITD) which can reduce ICP. We review the mechanisms of the ITD and its potential use as a countermeasure for SANS.

Devices to enhance organ perfusion during cardiopulmonary resuscitation

INTRODUCTION

The recommended method of cardiopulmonary resuscitation (CPR) has been closed-chest cardiac compressions, but the development of CPR adjunctive devices has called into question the efficacy and role of these adjunctive devices. In this review, we provide a comprehensive evaluation and discussion on the commercially available noninvasive CPR adjuncts used during out-of-hospital cardiac arrest (OHCA).

AREAS COVERED

We review the three most common CPR adjunctive devices: the piston mechanism, the load distributing band, and the impedance threshold device. All three CPR adjunctive devices have preclinical data to support their use during cardiac arrest. In clinical trials, limited data show improvement in survival and neurologic recovery for these devices, and there is insufficient high-level evidence to support their use over manual chest compressions. However, there is a role for them when adequate manual chest compressions are not feasible.

EXPERT OPINION

The commercially available CPR adjuncts do not consistently show improved outcomes in the literature. There is still a need for research and development into innovative solutions to improve OHCA survival and neurologic recovery. Efforts focused on increasing the speed of CPR initiation and increasing perfusion to the cerebral and coronary vasculature have the potential to advance resuscitative practices.

Mathematical model of modified hybrid pump mechanism for cardiopulmonary resuscitation

BACKGROUND AND OBJECTIVE

The "Cardiac pump theory" and "Thoracic pump theory" are representative theories of cardiopulmonary resuscitation (CPR) mechanisms. Based on these theories, many studies on mathematical modeling have been performed to help understand hemodynamics during CPR. However, there are parts that do not yet properly reflect the physiology of CPR. Therefore, this study aims to develop a lumped parameter model of CPR that can more accurately reflect the current CPR physiology.

METHODS

By adding compartments of the superior and inferior vena cava of the thoracic cavity to the existing CPR model, and the "Hybrid pump" mechanism was applied to simulate CPR. To compare the hemodynamics of the conventional CPR model and the developed CPR model, various conditions, such as active compression-decompression CPR with an impedance threshold valve device (ACD-CPR+ITV), head-up-tilt (HUT), and head-down-tilt (HDT), were simulated. The coronary perfusion pressure (CPP) was compared by modulating the compression ratio of the atrium and ventricle with the thoracic pump factor.

RESULTS

The result for the comparison of coronary blood flow showed that the existing model is predominant in the compression phase, whereas the developed model is dominant in the relaxation phase. ACD-CPR + ITV results showed that the CPP decreased by 5 % in the existing model, and increased by about 46 % in the developed model, revealing a distinct hemodynamic difference between the two models. Likewise, as a result of comparing the hemodynamic differences of the two models according to the changes in tilt angle, the HUT showed similar trends, while the HDT showed slightly different results. The CPP varied accordingly with the ratio of the ventricular and atrial thoracic pump factor.

CONCLUSION

Comparison of the hemodynamics with the existing model by simulating various conditions showed that the developed CPR model reflects the CPR physiology better. The model suggests that the hemodynamics may vary depending on the ventricle and atrium compression ratio. This study may provide an important basis for helping understand various situations and patient-specific hemodynamic characteristics during CPR through in-depth research, such as patient-specific model and parameter optimization.

Oxygenation, ventilation, and airway management in out-of-hospital cardiac arrest: a review

Recently published evidence has challenged some protocols related to oxygenation, ventilation, and airway management for out-of-hospital cardiac arrest. Interrupting chest compressions to attempt airway intervention in the early stages of OHCA in adults may worsen patient outcomes. The change of BLS algorithms from ABC to CAB was recommended by the AHA in 2010. Passive insufflation of oxygen into a patent airway may provide oxygenation in the early stages of cardiac arrest. Various alternatives to tracheal intubation or bag-mask ventilation have been trialled for prehospital airway management. Simple methods of airway management are associated with similar outcomes as tracheal intubation in patients with OHCA. The insertion of a laryngeal mask airway is probably associated with worse neurologically intact survival rates in comparison with other methods of airway management. Hyperoxemia following OHCA may have a deleterious effect on the neurological recovery of patients. Extracorporeal oxygenation techniques have been utilized by specialized centers, though their use in OHCA remains controversial. Chest hyperinflation and positive airway pressure may have a negative impact on hemodynamics during resuscitation and should be avoided. Dyscarbia in the postresuscitation period is relatively common, mainly in association with therapeutic hypothermia, and may worsen neurological outcome.

An updated systematic review and meta-analysis on impedance threshold devices in patients undergoing cardiopulmonary resuscitation

INTRODUCTION

Uncertainty persists on the clinical impact of impedance threshold devices in out-of-hospital cardiac arrest. We conducted an updated systematic review on impedance threshold devices.

METHODS

Several databases were searched for studies testing the effectiveness of impedance threshold devices in patients with cardiac arrest. The primary endpoint was long-term survival.

RESULTS

Seven trials (11,254 patients) were included. In 4 studies (2,284 patients) impedance threshold devices were used with active compression-decompression-cardiopulmonary resuscitation, and in the others alone. Overall, impedance threshold devices did not impact on the rate of return of spontaneous circulation (odds ratio=1.17 [0.96-1.43], p=0.114), favorable neurologic outcome (odds ratio=1.56 [0.97-2.50], p=0.065), or long-term survival (odds ratio=1.22 [0.94-1.58], p=0.127). These analyses were fraught with heterogeneity (respectively, p=0.055, p=0.236, and p=0.011) and inconsistency (respectively, I-squared=51% , I-squared=27% , and I-squared=67%). Exploratory analysis showed that combined use of impedance threshold devices with active compression-decompression significantly increased the likelihood of return of spontaneous circulation (odds ratio=1.19 [1.00-1.40], p=0.045), favorable neurologic outcome (odds ratio=1.60 [1.14-2.25], p=0.006), and long-term survival (odds ratio=1.52 [1.11-2.08], p=0.009). The favorable impact of the interaction between impedance threshold devices and active compression-decompression was also confirmed at meta-regression analysis (respectively, b=0.195 [0.004-0.387], p=0.045, b=0.500 [0.079-0.841], p=0.018, b=0.413 [0.063-0.764], p=0.021).

CONCLUSIONS

The evidence base on impedance threshold devices is apparently inconclusive, with a neutral impact on clinically relevant outcomes. However, exploratory analysis focusing on the combined use of impedance threshold devices with active compression-decompression suggests that this combo treatment may be useful to improve patient prognosis.

Passive leg raising during cardiopulmonary resuscitation results in improved neurological outcome in a swine model of prolonged ventricular fibrillation

OBJECTIVE

The objective was to evaluate whether passive leg raising during cardiopulmonary resuscitation in a porcine model of prolonged ventricular fibrillation improves hemodynamics, return of spontaneous circulation, 24-hour survival, and neurological outcome.

METHODS

Ventricular fibrillation was induced in 20 healthy Landrace/Large White piglets, which were subsequently left untreated for 8 minutes. Ten animals were randomly assigned into the control group and were resuscitated according to the 2005 European Resuscitation Council guidelines, and 10 piglets were assigned into the passive leg raising group and were resuscitated with the legs passively raised at 45° with the aid of a special purpose-made metallic device. End points were either return of spontaneous circulation or asystole.

RESULTS

Return of spontaneous circulation was observed in 6 and 9 animals from the control and the passive leg raising group, respectively (P = .121; odds ratio = 0.16; 95% confidence interval, 0.01-1.87). Just prior to the first defibrillation attempt, coronary perfusion pressure was significantly higher in the passive leg raising group (22.8 ± 9.5 vs 10.6 ± 6.5 mm Hg, P < .004); but no subsequent significant differences were observed. Although all animals that restored spontaneous circulation survived for 24 hours, neurologic alertness score was significantly better in the animals treated with passive leg raising (90 ± 10 vs 76.6 ± 12.1, P = .037).

CONCLUSIONS

Passive leg raising during cardiopulmonary resuscitation significantly increased coronary perfusion pressure in the minute prior to the first shock. Return of spontaneous circulation and 24-hour survival rate were comparable between groups. However, the animals in the passive leg raising group exhibited significantly higher neurological scores.

Use of the impedance threshold device improves survival rate and neurological outcome in a swine model of asphyxial cardiac arrest*

OBJECTIVE

To assess whether intermittent impedance of inspiratory gas exchange improves hemodynamic parameters, 48-hr survival, and neurologic outcome in a swine model of asphyxial cardiac arrest treated with active compression-decompression cardiopulmonary resuscitation.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Laboratory investigation.

SUBJECTS

Thirty healthy Landrace/Large-White piglets of both sexes, aged 10 to 15 wks, whose average weight was 19 ± 2 kg.

INTERVENTIONS

At approximately 7 mins following endotracheal tube clamping, ventricular fibrillation was induced and remained untreated for another 8 mins. Before initiation of cardiopulmonary resuscitation, animals were randomly assigned to either receive active compression-decompression cardiopulmonary resuscitation plus a sham impedance threshold device (control group, n = 15), or active compression-decompression cardiopulmonary resuscitation plus an active impedance threshold device (experimental group, n = 15). Electrical defibrillation was attempted every 2 mins until return of spontaneous circulation or asystole.

MEASUREMENTS AND MAIN RESULTS

Return of spontaneous circulation was observed in six (40%) animals treated with the sham valve and 14 (93.3%) animals treated with the active valve (p = .005, odds ratio 21.0, 95% confidence interval 2.16-204.6). Neuron-specific enolase and S-100 levels increased in the ensuing 4 hrs post resuscitation in both groups, but they were significantly elevated in animals treated with the sham valve (p < .01). At 48 hrs, neurologic alertness score was significantly better in animals treated with the active valve (79.1 ± 18.7 vs. 50 ± 10, p < .05) and was strongly negatively correlated with 1- and 4-hr postresuscitation neuron-specific enolase (r = -.86, p < .001 and r = -.87, p < .001, respectively) and S-100 (r = -.77, p < .001 and r = -0.8, p = .001) values.

CONCLUSIONS

In this model of asphyxial cardiac arrest, intermittent airway occlusion with the impedance threshold device during the decompression phase of active compression-decompression cardiopulmonary resuscitation significantly improved hemodynamic parameters, 24- and 48-hr survival, and neurologic outcome evaluated both with clinical and biochemical parameters (neuron-specific enolase, S-100).

Evaluation of Greek high school teachers' knowledge in basic life support, automated external defibrillation, and foreign body airway obstruction: implications for nursing interventions

INTRODUCTION

The aim of this study was to evaluate the theoretic knowledge of high school teachers regarding cardiopulmonary resuscitation, automated external defibrillation, and foreign body airway obstruction.

METHODS

Three hundred ten respondents were tested prospectively by use of a scoring system. Data were obtained by use of a questionnaire that included 24 questions. Data were collected between April 9 and June 16, 2009.

RESULTS

Only 21.03% of the teachers had ever participated in life support courses, and most of them did not possess adequate theoretic knowledge in the management of adult cardiac arrest or foreign body airway obstruction. As the age of the teachers increases, the ratio of correct answers decreases. Life support course attendance has a positive effect on their theoretic knowledge. The majority of the teachers would welcome an emergency nurse to educate them and their students on basic life support and foreign body airway obstruction.

DISCUSSION

This study shows that most of the respondents had a mediocre level of knowledge in basic life support, automated external defibrillation, and foreign body airway obstruction. Given that emergency nurses regularly practice resuscitation in the emergency department in which they are working, they have the motivation to be kept updated with the current guidelines on resuscitation, because guidelines on resuscitation are revised every 5 years. Teachers, on the other hand, are less motivated to be kept updated; thus emergency nurses may be the key component in educating teachers and school students. Therefore we believe that emergency nurses should take on the responsibility and act as school educators regarding cardiopulmonary resuscitation.