Hyperventilation following aero-medical rapid sequence intubation may be a deliberate response to hypoxemia

Efficacy of endotracheal intubation in helicopter cabin vs. ground: a systematic review and meta-analysis

BACKGROUND

Pre-hospital endotracheal intubation (ETI) is a sophisticated procedure with a comparatively high failure rate. Especially, ETI in confined spaces may result in higher difficulty, longer times, and a higher failure rate. This study analyses if Helicopter Emergency Medical Services (HEMS) intubation (time-to) success are influenced by noise, light, and restricted space in comparison to ground intubation. Available literature reporting these parameters was very limited, thus the reported differences between ETI in helicopter vs. ground by confronting parameters such as time to secure airway, first pass success rate and Cormack-Lehane Score were analysed.

METHODS

A systematic review and meta-analysis were conducted using PUBMED, EMBASE, Cochrane Library, and Ovid on October 15th, 2022. The database search provided 2322 studies and 6 studies met inclusion and quality criteria. The research was registered with the International Prospective Register of Systematic Reviews (CRD42022361793).

RESULTS

A total of six studies were selected and analysed as part of the systematic review and meta-analysis. The first pass success rate of ETI was more likely to fail in the helicopter setting as compared to the ground (82,4% vs. 87,3%), but the final success rate was similar between the two settings (96,8% vs. 97,8%). The success rate of intubation in literature was reported higher in physician-staffed HEMS than in paramedic-staffed HEMS. The impact of aircraft type and location inside the vehicle on intubation success rates was inconclusive across studies. The meta-analysis revealed inconsistent results for the mean duration of intubation, with one study reporting shorter intubation times in helicopters (13,0s vs.15,5s), another reporting no significant differences (16,5s vs. 16,8s), and a third reporting longer intubation times in helicopters (16,1s vs. 15,0s).

CONCLUSION

Further research is needed to assess the impact of environmental factors on the quality of ETI on HEMS. While the success rate of endotracheal intubation in helicopters vs. on the ground is not significantly different, the duration and time to secure the airway, and Cormack-Lehane Score may be influenced by environmental factors. However, the limited number of studies reporting on these factors highlights the need for further research in this area.

Paramedic Endotracheal Intubation Success Rates Before and After an Intensive Airway Management Education Session

Introduction

Advanced airway management by paramedics is potentially life-saving, but carries a significant risk to patient safety and can be associated with poor clinical outcome if performed incorrectly. Previously, our team had found that an intensive education intervention demonstrated an improvement in paramedic performance on a written exam and increased confidence in airway skills. This study measured intubation success and the number of attempts per patient before and after intensive paramedic airway management education intervention.

Methods

A 10-hour mandatory course was taken by all advanced life support (ALS) paramedics in a provincial system (2009/04-07, n=~395). The course was done during semi-annual continuing education Emergency Health Services (EHS) in-services. These day-long courses were held in person over four months. The electronic charting database was queried for intubation attempts and successful placements 12 months before the training, during the four months of training, and 12 months post-training. The primary outcome is the difference in success rates between the before (pre-intervention) and after (post-intervention) periods. The secondary outcome is the number of attempts per patient. Stationarity of success in pre- and post-periods was tested. The model was fit tested using Maximum Likelihood regression, and variables were tested using the Wald test.

Results

A sample size of 476 intubation attempts in each of the pre- and post-periods was required to detect a 10% improvement with the pre-intervention success of 60%. A total of 1421 intubation attempts occurred; 674 pre-intervention, 604 post-intervention, and 143 during teaching. Seven attempts were excluded (success unknown). Intubation success rates improved, from 0.68 (95% CI 0.64-0.71) to 0.75 (95% CI 0.72-0.78); a difference of 0.076 (95% CI 0.03-0.12) (p = 0.001). Intubation success rates in the pre-intervention and post-intervention periods were found to be static. A significant decrease was found in the number of attempts per patient in the post-period (p = 0.005).

Conclusion

Intubation success increased from 68% to 75% and was maintained over the 12-month post-period. There is a potential that judgment may also have improved, based on the decreased number of attempts per patient. Limitations include missing values, paramedics’ self-reported number of attempts, and the definition of what is considered to be an attempt. In addition to previously demonstrated improvements in paramedic exam and scenario performance, this airway education intervention appears to have made a significant improvement to patient outcomes. These findings support the value of such education interventions to improve performance.

Mechanical Ventilation of Severe Traumatic Brain Injury Patients in the Prehospital Setting

OBJECTIVE

Suboptimal ventilation may impact outcomes in patients with traumatic brain injury (TBI). This study compares the incidence of eucapnia between manually and mechanically ventilated patients with severe TBI during helicopter transport.

METHODS

This retrospective chart review included consecutive intubated adults with severe TBI (Glasgow Coma Scale score < 9) transported by helicopter from the scene of injury to a level 1 trauma center between 2009 and 2015. The primary outcome was the first venous partial pressure of carbon dioxide obtained in the emergency department. Hypocapnia, eucapnia, and hypercapnia were defined based on the normal range for the testing instrument. The Fisher exact test was used to compare groups.

RESULTS

Of 1,070 trauma patients intubated and transported, 93 met the inclusion criteria with full data. The mean age was 43 years, 81 of 93 were white, and 70 of 93 were men. The mean Injury Severity Score was 29, and 26 of 93 were mechanically ventilated. Hypocapnia occurred in 4 of 93 and hypercapnia in 56 of 93. There was no difference in the rate of eucapnia in manually ventilated compared with mechanically ventilated patients (36% vs. 35%, P = 1.00).

CONCLUSION

Eucapnia at emergency department arrival occurred in 36% of patients and was unaffected by whether ventilation was manually or mechanically controlled. Few patients were hypocapnic, indicating a low incidence of hyperventilation during helicopter transport.

A descriptive analysis of endotracheal intubation in a South African Helicopter Emergency Medical Service

Introduction

Helicopter Emergency Medical Services (HEMS) exists to supplement the operations of ground-based emergency care providers, mainly in high acuity cases. One of the important procedures frequently carried out by HEMS personnel is endotracheal intubation. Several HEMS providers exist in South Africa, with a mix of advanced life support personnel, however intubation success rates and adverse events have not been described in any local HEMS operation.

Methods

This was a retrospective chart review of intubation-related data collected by a HEMS operation based in Johannesburg over a 16-month period. First-pass and overall success rates were described, in addition to perceived airway difficulty, adverse events and other data.

Results

Of the 49 cases recorded in the study period, one was excluded leaving 48 cases for analysis. Most cases (n = 34, 71%) involved young male trauma patients who were intubated with rapid sequence intubation. The first pass success rate was 79% (n = 38) with an overall success rate of 98% (n = 47). At least one factor suggesting airway difficulty was present in 29% (n = 14) of cases, with most perceived airway difficulty related to the high prevalence of trauma cases. At least one adverse event occurred in 27% (n = 13) of cases with hypoxaemia, hypotension and bradycardia most prevalent.

Discussion

In this small sample of South African HEMS intubation cases, we found overall and first-pass success rates comparable to those reported in similar contexts.

Implementation of a Clinical Bundle to Reduce Out-of-Hospital Peri-intubation Hypoxia

STUDY OBJECTIVE

Peri-intubation hypoxia is an important adverse event of out-of-hospital rapid sequence intubation. The aim of this project is to determine whether a clinical bundle encompassing positioning, apneic oxygenation, delayed sequence intubation, and goal-directed preoxygenation is associated with decreased peri-intubation hypoxia compared with standard out-of-hospital rapid sequence intubation.

METHODS

We conducted a retrospective, before-after study using data from a suburban emergency medical services (EMS) system in central Texas. The study population included all adults undergoing out-of-hospital intubation efforts, excluding those in cardiac arrest. The before-period intervention was standard rapid sequence intubation using apneic oxygenation at flush flow, ketamine, and a paralytic. The after-period intervention was a care bundle including patient positioning (elevated head, sniffing position), apneic oxygenation, delayed sequence intubation (administration of ketamine to facilitate patient relaxation and preoxygenation with a delayed administration of paralytics), and goal-directed preoxygenation. The primary outcome was the rate of peri-intubation hypoxia, defined as the percentage of patients with a saturation less than 90% during the intubation attempt.

RESULTS

The before group (October 2, 2013, to December 13, 2015) included 104 patients and the after group (August 8, 2015, to July 14, 2017) included 87 patients. The 2 groups were similar in regard to sex, age, weight, ethnicity, rate of trauma, initial oxygen saturation, rates of initial hypoxia, peri-intubation peak SpO₂, preintubation pulse rate and systolic blood pressure, peri-intubation cardiac arrest, and first-pass and overall success rates. Compared with the before group, the after group experienced less peri-intubation hypoxia (44.2% versus 3.5%; difference -40.7% [95% confidence interval -49.5% to -32.1%]) and higher peri-intubation nadir SpO₂ values (100% versus 93%; difference 5% [95% confidence interval 2% to 10%]).

CONCLUSION

In this single EMS system, a care bundle encompassing patient positioning, apneic oxygenation, delayed sequence intubation, and goal-directed preoxygenation was associated with lower rates of peri-intubation hypoxia than standard out-of-hospital rapid sequence intubation.

Preliminary report of a mathematical model of ventilation and intrathoracic pressure applied to prehospital patients with severe traumatic brain injury

BACKGROUND

Inadvertent hyperventilation is associated with poor outcomes from traumatic brain injury (TBI). Hypocapnic cerebral vasoconstriction is well described and causes an immediate and profound decrease in cerebral perfusion. The hemodynamic effects of positive-pressure ventilation (PPV) remain incompletely understood but may be equally important, particularly in the hypovolemic patient with TBI.

OBJECTIVE

Preliminary report on the application of a previously described mathematical model of perfusion and ventilation to prehospital data to predict intrathoracic pressure.

METHODS

Ventilation data from 108 TBI patients (76 ground transported, 32 helicopter transported) were used for this analysis. Ventilation rate (VR) and end-tidal carbon dioxide (PetCO2) values were used to estimate tidal volume (VT). The values for VR and estimated VT were then applied to a previously described mathematical model of perfusion and ventilation. This model allows input of various lung parameters to define a pressure-volume relationship, then derives mean intrathoracic pressure (MITP) for various VT and VR values. For this analysis, normal lung parameters were utilized. Separate analyses were performed assuming either fixed or variable PaCO2-PetCO2 differences. Ground and air medical patients were compared with regard to VR, PetCO2, estimated VT, and predicted MITP.

RESULTS

A total of 10,647 measurements were included from the 108 TBI patients, representing about 13 minutes of ventilation per patient. Mean VR values were higher for ground patients versus air patients (21.6 vs. 19.7 breaths/min; p < 0.01). Estimated VT values were similar for ground and air patients (399 mL vs. 392 mL; p = NS) in the fixed model but not the variable (636 vs. 688 mL, respectively; p < 0.01). Mean PetCO2 values were lower for ground versus air patients (30.6 vs. 33.8 mmHg; p < 0.01). Predicted MITP values were higher for ground versus air patients, assuming either fixed (9.0 vs. 8.1 mmHg; p < 0.01) or variable (10.9 vs. 9.7 mmHg; p < 0.01) PaCO2-PetCO2 differences.

CONCLUSIONS

Predicted MITP values increased with ventilation rates. Future studies to externally validate this model are warranted.

Evaluation of the impact of implementing the emergency medical services traumatic brain injury guidelines in Arizona: the Excellence in Prehospital Injury Care (EPIC) study methodology

Traumatic brain injury (TBI) exacts a great toll on society. Fortunately, there is growing evidence that the management of TBI in the early minutes after injury may significantly reduce morbidity and mortality. In response, evidence-based prehospital and in-hospital TBI treatment guidelines have been established by authoritative bodies. However, no large studies have yet evaluated the effectiveness of implementing these guidelines in the prehospital setting. This article describes the background, design, implementation, emergency medical services (EMS) treatment protocols, and statistical analysis of a prospective, controlled (before/after), statewide study designed to evaluate the effect of implementing the EMS TBI guidelines-the Excellence in Prehospital Injury Care (EPIC) study (NIH/NINDS R01NS071049, "EPIC"; and 3R01NS071049-S1, "EPIC4Kids"). The specific aim of the study is to test the hypothesis that statewide implementation of the international adult and pediatric EMS TBI guidelines will significantly reduce mortality and improve nonmortality outcomes in patients with moderate or severe TBI. Furthermore, it will specifically evaluate the effect of guideline implementation on outcomes in the subgroup of patients who are intubated in the field. Over the course of the entire study (~9 years), it is estimated that approximately 25,000 patients will be enrolled.

Hemodynamic consequences of ketamine vs etomidate for endotracheal intubation in the air medical setting

OBJECTIVE

Recent drug shortages have required the occasional replacement of etomidate for endotracheal intubation (ETI) by helicopter emergency medical services (HEMS), with ketamine. The purpose of this study was to assess whether there was an association between ketamine vs etomidate use as the main ETI drug, with hemodynamic or clinical (airway) end points.

METHODS

This retrospective study used data entered into medical records at the time of HEMS transport. Subjects, 50 ketamine and 50 etomidate, were accrued from 3 US HEMS programs. The study period was from August 2011 through May 2012. Data collection included demographics, diagnostic category, ETI drugs use, ETI success, and complications. Hemodynamic parameters were assessed for up to 2 sets of vital signs before airway management and up to 5 sets of post-ETI vital signs. Significance was defined at the P < .05 level.

RESULTS

Patients on ketamine and etomidate were similar (P > .05) with respect to age, sex, scene/interfacility mission type, trauma vs nontrauma, neuromuscular blocking agent use, and rates of coadministration of fentanyl or midazolam. All patients had successful airway placement. Peri-ETI hypoxemia was seen in 10% of etomidate and 16% of ketamine cases (P = .55). The pre-ETI and post-ETI were similar between the ketamine and etomidate groups with respect to systolic blood pressure and heart rate at every vital signs assessment after ETI.

CONCLUSION

Initial assessment of ETI success and complication rates, as well as peri-ETI hemodynamic changes, suggests no concerning complications associated with large-scale replacement of etomidate with ketamine as the major airway management drug for HEMS.

Association of out-of-hospital advanced airway management with outcomes after traumatic brain injury and hemorrhagic shock in the ROC hypertonic saline trial

OBJECTIVE

Prior studies suggest adverse associations between out-of-hospital advanced airway management (AAM) and patient outcomes after major trauma. This secondary analysis of data from the Resuscitation Outcomes Consortium Hypertonic Saline Trial evaluated associations between out-of-hospital AAM and outcomes in patients suffering isolated severe traumatic brain injury (TBI) or haemorrhagic shock.

METHODS

This multicentre study included adults with severe TBI (GCS ≤8) or haemorrhagic shock (SBP ≤70 mm Hg, or (SBP 71-90 mm Hg and heart rate ≥108 bpm)). We compared patients receiving out-of-hospital AAM with those receiving emergency department AAM. We evaluated the associations between airway strategy and patient outcomes (28-day mortality, and 6-month poor neurologic or functional outcome) and airway strategy, adjusting for confounders. Analysis was stratified by (1) patients with isolated severe TBI and (2) patients with haemorrhagic shock with or without severe TBI.

RESULTS

Of 2135 patients, we studied 1116 TBI and 528 shock; excluding 491 who died in the field, did not receive AAM or had missing data. In the shock cohort, out-of-hospital AAM was associated with increased 28-day mortality (adjusted OR 5.14; 95% CI 2.42 to 10.90). In TBI, out-of-hospital AAM showed a tendency towards increased 28-day mortality (adjusted OR 1.57; 95% CI 0.93 to 2.64) and 6-month poor functional outcome (1.63; 1.00 to 2.68), but these differences were not statistically significant. Out-of-hospital AAM was associated with poorer 6-month TBI neurologic outcome (1.80; 1.09 to 2.96).

CONCLUSIONS

Out-of-hospital AAM was associated with increased mortality after haemorrhagic shock. The adverse association between out-of-hospital AAM and injury outcome is most pronounced in patients with haemorrhagic shock.

The need for standardized data reporting for prehospital airway management

Despite a widespread belief in the value of aggressive prehospital airway management, the therapeutic benefits of early tracheal intubation (TI) remain unclear. In fact, most attempts to elucidate the benefits of prehospital TI on outcome from traumatic brain injury and cardiopulmonary arrest have documented an increase in mortality associated with the procedure. While some degree of selection bias is likely present in these studies, the inherent adverse physiological effects of intubation and a high incidence of desaturation and subsequent hyperventilation may indicate a harmful effect of the procedure. This uncertainty regarding such a fundamental resuscitation procedure as TI underscores the need for standardized data reporting in prehospital airway management research. To this end, the Utstein prehospital airway conference proposed a set of variables that would move us in that direction. However, the present article by Lossius and colleagues documents how far we still have to travel before such standardization can be achieved. Only through these efforts can we elucidate the true benefits - or harm - of advanced airway management during critical resuscitation.

Latency and loss of pulse oximetry signal with the use of digital probes during prehospital rapid-sequence intubation

BACKGROUND

Prehospital personnel rely on timely and accurate pulse oximetry data when performing critical skills, such as rapid-sequence intubation (RSI). However, loss of signal may be a frequent occurrence in patients with poor peripheral perfusion. In addition, a delay or latency period in the timeliness of pulse oximetry data may exist with probes placed on the fingers.

OBJECTIVE

To define the incidence of pulse oximetry signal loss or a latent period during prehospital RSI.

METHODS

Patients with severe traumatic brain injury (TBI) (Glasgow Coma Scale score [GCS] 3-8) undergoing prehospital RSI by air medical crews were enrolled. Data from hand-held oximetry-capnometry units were analyzed for either the loss of a pulse oximetry tracing (≥ 30 seconds) during the RSI procedure or the presence of a latent period, defined by the saturation of peripheral oxygen (SpO(2)) nadir occurring after intubation in patients undergoing desaturation (SpO(2) ≤ 93%) during the procedure.

RESULTS

A total of 98 of 124 patients (79%, 95% confidence interval [CI] 71-85%) had pulse oximetry failure during critical points in the RSI procedure. In the 49 patients with a desaturation during RSI, a latent period was observed in 27 patients (55%, 95% CI 41-68%).

CONCLUSIONS

A high incidence of pulse oximetry failure was observed with the use of a digital pulse oximetry probe during prehospital RSI. In addition, a latent period appears to exist in the majority of patients undergoing desaturation.

Prehospital endotracheal intubation in patients with severe traumatic brain injury: guidelines versus reality

The international Brain Trauma Foundation guidelines recommend prehospital endotracheal intubation in all patients with traumatic brain injury (TBI) and a Glasgow Coma Scale (GCS)< or =8. Close adherence to these guidelines is associated with improved outcome, but not all severely injured TBI patients receive adequate prehospital airway support. Here we hypothesized that guideline adherence varies when skills are involved that rely on training and expertise, such as endotracheal intubation. We retrospectively studied the medical records of CT-confirmed TBI patients with a GCS< or =8 who were referred to a level 1 trauma centre in Amsterdam (n=127). Records were analyzed for demographic parameters, prehospital treatment modalities, involvement of an emergency medical service (EMS) and respiratory and metabolic parameters upon arrival at the hospital. Patients were mostly male, aged 45+/-21 years with a median injury severity score (ISS) of 26. Of all patients for whom guidelines recommend endotracheal intubation, only 56% were intubated. In 21 out of 106 severe cases an EMS was not called for, suggesting low guideline adherence. Especially those TBI patients treated by paramedics tended to develop higher levels of stress markers like glucose and lactate. We observed a low degree of adherence to intubation guidelines in a Dutch urban area. Main reasons for low adherence were the unavailability of specialized care, scoop and run strategies and absence of a specialist physician in cases where intubation was recommended. The discrepancy between guidelines and reality warrants changing practice to improve guideline compliance and optimize outcome in TBI patients.

Early ventilation in traumatic brain injury

While airway and ventilatory compromise are significant concerns following traumatic brain injury (TBI), there is little data supporting an aggressive approach to airway management by prehospital personnel, and a growing number of reports suggesting an association between early intubation and increased mortality. Recent clinical and experimental data suggest that hyperventilation is an important contributor to these adverse outcomes in TBI patients. Various mechanisms appear to be responsible for the worsened outcomes, including hemodynamic, cerebrovascular, immunologic and cellular effects. Here, relevant experimental and clinical data regarding the impact of ventilation on TBI are reviewed. In addition, experimental data regarding potential mechanisms for the adverse effects of hyperventilation and hypocapnia on the injured brain are presented. Finally, the limited data regarding the impact of hypoventilation and hypercapnia on outcome from TBI are discussed.

Does pre-hospital ventilation effect outcome after significant brain injury?

Traumatic brain injury has a devastating impact on society, utilizing many resources and disproportionately affecting the young. Recent evidence demonstrates the early care of the brain injured patient impacts patient outcomes. While prevention of systolic hypotension and hypoxia are mainstays of prehospital management of the injured patient ventilatory management performed in the prehospital environment has recently been shown to impact outcomes. Hypocapnea from hyperventilation has been shown in several trials to cause deleterious effects from cerebral vasoconstriction and ischemia. The importance of balancing the prevention of both hypocapnea and hypercapnea has led to the idea of a target ventilation range for arterial carbon dioxide tension, the ideal way to achieve this balance in the prehospital setting remains elusive. This article reviews the background, physiologic effects, impact on outcomes, and implications for prehospital care of prehospital ventilation.