Delivery of titrated oxygen via a self-inflating resuscitation bag

doi:10.1016/j.resuscitation.2012.08.330

Resuscitation

Volume 84, Issue 3, March 2013, Pages 391-394

https://doi.org/10.1016/j.resuscitation.2012.08.330 Get rights and content

Abstract

Aim

To investigate whether titration of inspired oxygen can be achieved through adjustment of oxygen flow into a self-inflating resuscitation bag with a reservoir of a type used in standard ambulance practice.

Methods

In a series of bench experiments, oxygen was delivered via a flow metre to a 1500 ml self-inflating resuscitation bag with a 2500 ml reservoir bag and connected to a test lung. The oxygen concentration delivered to the test lung by manual inflation of the resuscitation bag was measured using an anaesthetic machine while the delivered tidal volume was measured using a respirometer. The delivered oxygen concentration was measured at flows of 0.5, 2, 6, 12 and 15 l min⁻¹ for tidal volumes of 300, 600, and 900 ml with bag inflation rates of 10, 20 and 30 min⁻¹.

Results

A wide range of delivered oxygen concentrations ranging between 24% and 99.5% were achieved with different oxygen flows, tidal volumes, and inflation rates. Overall, the mean delivered oxygen concentration increased significantly with each of the increments of oxygen flow tested (p < 0.001 for all comparisons).

Conclusions

Effective titration of oxygen delivery can be achieved using adjustment of oxygen flow with a standard self-inflating resuscitation bag and reservoir.

Introduction

In animal models, exposure to 100% oxygen around the time of cardiac arrest leads to significantly worse neurological outcomes than oxygen administered at lower concentrations.¹ In adult human cardiac arrest, the effect of hyperoxia has been examined in three large retrospective studies and while two studies reported that hyperoxia was associated with an increased mortality risk,2, 3, 4 a third study found no association after adjustment for illness severity.⁴ The need for a prospective randomised clinical trial to establish the efficacy and safety of controlled reoxygenation in the context of post-cardiac arrest management has been highlighted.⁵ However, with the exception of one small trial which was not powered to detect differences in clinical outcomes,⁶ no prospective study of different oxygen regimes in patients resuscitated from cardiac arrest has been performed. One impediment to the conduct of a large scale randomised trial is that standard ambulances only carry bottled oxygen and do not have the capacity to deliver specific inspired oxygen concentrations of less than 100% to ventilated patients. Typically, patients who require ventilation after resuscitation from cardiac arrest are ventilated en route to hospital with a self-inflating resuscitation bag with a reservoir connected to high flow oxygen. One potential method to achieve reduced concentrations of oxygen in these patients is through reductions in oxygen flow into the self-inflating resuscitation bag. This study evaluates the hypothesis that titration of inspired oxygen from 21% to 100% can be delivered through adjustment of oxygen flow into a self-inflating resuscitation bag with a reservoir of a type used in standard ambulance practice.

Section snippets

Study design

We performed a series of bench experiments to determine the effect of changing oxygen flow on inspired oxygen concentration using a self-inflating resuscitation bag at different tidal volumes and resuscitation bag inflation rates.

Technical information

Oxygen was delivered via an FM-1510-F4 oxygen flow metre (Amvex Corporation, Ontario, Canada) connected to a disposable 1500 ml Hsiner Manual Resuscitator with a 2500 ml reservoir bag (Hinser Ltd., Taichung City, Taiwan). This resuscitator (self-inflating resuscitation

Results

A wide range of delivered oxygen concentrations ranging between 24% and 99.5% were achieved using standard ambulance equipment (Table 2). For each combination of tidal volume and inflation rate, progressive increases in oxygen flow rate led to progressive rises in delivered oxygen concentration up until a ceiling where a percentage of delivered oxygen in the high 90 s was consistently achieved. The mean delivered oxygen concentration increased significantly with each of the increments of oxygen

Discussion

We have shown that using ambulance equipment, delivered oxygen concentration can be titrated using adjustments of oxygen flow into a self-inflating resuscitation bag with a reservoir. While particular rates of oxygen flow did not deliver fixed inspired oxygen concentrations, our data provide an estimation of likely delivered concentration that would be achieved for particular flow rates after resuscitation. For example, for a tidal volume of 600 ml and an inflation rate of 10 breaths min⁻¹, a flow

Conclusion

Effective titration of oxygen delivery can be achieved using adjustment of oxygen flow with a standard self-inflating resuscitation bag and reservoir. Adjustment of oxygen flow may be an appropriate method of titrating oxygen to avoid exposure to hyperoxia in patients who are intubated and ventilated after cardiac arrest in the pre-hospital setting.

Conflicts of interest statement

The authors have no conflicts of interest to report.

Acknowledgements

The authors would like to acknowledge Mr Andrew Ditchburn (Anaesthetic Technician, Wellington Hospital) for providing technical support.

References (8)

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A.C. de Godoy et al.
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European Resuscitation Council and European Society of Intensive Care Medicine Guidelines 2021: Post-resuscitation care
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Oxygenation measured early after ROSC is highly variable, varying from hypoxaemia to extreme hyperoxaemia.81 Thus, it is appropriate to titrate the inspired oxygen by adjusting either the oxygen flow if using bag-mask ventilation or the fraction inspired oxygen (FiO2) if using a mechanical ventilator.82 Prolonged use of 100% inspired oxygen, for example during transport, will lead commonly to extreme hyperoxaemia.83
The European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM) have collaborated to produce these post-resuscitation care guidelines for adults, which are based on the 2020 International Consensus on Cardiopulmonary Resuscitation Science with Treatment Recommendations. The topics covered include the post-cardiac arrest syndrome, diagnosis of cause of cardiac arrest, control of oxygenation and ventilation, coronary reperfusion, haemodynamic monitoring and management, control of seizures, temperature control, general intensive care management, prognostication, long-term outcome, rehabilitation, and organ donation.
The EXACT protocol: A multi-centre, single-blind, randomised, parallel-group, controlled trial to determine whether early oxygen titration improves survival to hospital discharge in adult OHCA patients
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Experimental and observational research suggests hyperoxia following resuscitation from cardiac arrest is associated with neurological injury and worse clinical outcomes. This paper describes the rationale and design of the EXACT trial. EXACT aims to determine whether reducing oxygen in the acute phase of post-resuscitation care for out-of-hospital cardiac arrest (OHCA) improves survival.
EXACT is a multi-centre, randomised (1:1), single-blind, parallel trial. Presumed cardiac OHCA cases who achieve a return of spontaneous circulation will be eligible if they are comatose, with an advanced airway and have an oxygen saturation (SpO₂) ≥95% on >10 L/min (or 100% oxygen). Paramedics will randomise 1416 eligible cases to receive oxygen therapy targeting an SpO₂ of 90–94% (intervention) or 98–100% (control). Study treatment will continue until admission to an intensive care unit or hospital ward. The primary outcome is survival to hospital discharge. Secondary outcomes include 12-month survival and quality of life.
The study has commenced in the Australian states of Victoria and South Australia, and has enrolled 167 eligible cases to date (80 intervention and 87 control). Further sites are due to commence in 2019, recruitment is expected to take three years.
This study will determine if early reduction of oxygen leads to improved outcomes in OHCA. Such a finding may potentially change clinical practice with implications on future OHCA survival outcomes.
Trial registration number: NCT03138005.
Oxygen titration after resuscitation from out-of-hospital cardiac arrest: A multi-centre, randomised controlled pilot study (the EXACT pilot trial)
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In the titrated arm of our original protocol, oxygen was titrated to 2 L/min and delivered by a BVR device. This level was based on bench tests which found that 2 L/min via a BVR provides oxygen at an FiO2 of approximately 50% when delivered at a rate of 14/min and a tidal volume of 600 mL [17]. However, our results showed that titration of oxygen to 2 L/min in practice resulted in a significant number of patients desaturating below the initially acceptable oxygen saturation level of 94%.
Recent studies suggest the administration of 100% oxygen to hyperoxic levels following return-of-spontaneous-circulation (ROSC) post-cardiac arrest may be harmful. However, the feasibility and safety of oxygen titration in the prehospital setting is unknown. We conducted a multi-centre, phase-2 study testing whether prehospital titration of oxygen results in an equivalent number of patients arriving at hospital with oxygen saturations SpO2 ≥ 94%.
We enrolled unconscious adults with: sustained ROSC; initial shockable rhythm; an advanced airway; and an SpO2 ≥ 95%. Initially (Sept 2015–March 2016) patients were randomised 1:1 to either 2 L/minute (L/min) oxygen (titrated) or >10 L/min oxygen (control) via a bag-valve reservoir. However, one site experienced a high number of desaturations (SpO2 < 94%) in the titrated arm and this arm was changed (April 2016) to an initial reduction of oxygen to 4 L/min then, if tolerated, to 2 L/min, and the desaturation limit was decreased to <90%.
We randomised 61 patients to titrated (n = 37: 2L/min = 20 and 2–4 L/min = 17) oxygen or control (n = 24). Patients allocated to titrated oxygen were more likely to desaturate compared to controls ((SpO2 < 94%: 43% vs. 4%, p = 0.001; SpO2 < 90%: 19% vs. 4%, p = 0.09). The majority of desaturations (81%) occurred at 2L/min. On arrival at hospital the majority of patients had a SpO2 ≥ 94% (titrated: 90% vs. control: 100%) and all patients had a SpO2 ≥ 90%. One patient (control) re-arrested. Survival to hospital discharge was similar.
Oxygen titration post-ROSC is feasible in the prehospital environment, but incremental titration commencing at 4L/min oxygen flow may be needed to maintain an oxygen saturation >90% (NCT02499042).
Ventilator Management and Respiratory Care After Cardiac Arrest: Oxygenation, Ventilation, Infection, and Injury
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There are several studies that have evaluated prehospital respiratory interventions after cardiac arrest. As a prelude to the HOT or NOT trial discussed earlier, Young et al102 demonstrated that predictable Fio2 can be delivered through standard manual resuscitators by simply decreasing the oxygen flow rate. Another study involving a university-based air medical transport service that included post-arrest patients demonstrated that low tidal volume ventilation was rare during air medical transport, and transport ventilator settings influenced subsequent hospital-based ventilator settings, highlighting the potential impact of prehospital care on subsequent in-hospital events.103
Return of spontaneous circulation after cardiac arrest results in a systemic inflammatory state called the post-cardiac arrest syndrome, which is characterized by oxidative stress, coagulopathy, neuronal injury, and organ dysfunction. Perturbations in oxygenation and ventilation may exacerbate secondary injury after cardiac arrest and have been shown to be associated with poor outcome. Further, patients who experience cardiac arrest are at risk for a number of other pulmonary complications. Up to 70% of patients experience early infection after cardiac arrest, and the respiratory tract is the most common source. Vigilance for early-onset pneumonia, as well as aggressive diagnosis and early antimicrobial agent administration are important components of critical care in this population. Patients who experience cardiac arrest are at risk for the development of ARDS. Risk factors include aspiration, pulmonary contusions (from chest compressions), systemic inflammation, and reperfusion injury. Early evidence suggests that they may benefit from ventilation with low tidal volumes. Meticulous attention to mechanical ventilation, early assessment and optimization of respiratory gas exchange, and therapies targeted at potential pulmonary complications may improve outcomes after cardiac arrest.
HyperOxic Therapy OR NormOxic Therapy after out-of-hospital cardiac arrest (HOT OR NOT): A randomised controlled feasibility trial
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Citation Excerpt :
Once patients arrived in hospital, the FiO2 on the ventilator was adjusted as required. In the event that, in the judgement of the attending paramedic, reliable pulse oximetry recordings were not possible in the pre-hospital period, the protocol initially specified that oxygen should be delivered at 1 litre per minute which corresponds to an FiO2 of approximately 0.40.10 After enrolment of six patients, the study protocol was amended because of a reported adverse event where a patient assigned to the titrated oxygen group had an unrecognised tension pneumothorax in the pre-hospital period and reliable pulse oximetry recordings could not be obtained.
To investigate the feasibility of delivering titrated oxygen therapy to adults with return of spontaneous circulation (ROSC) following out-of-hospital cardiac arrest (OHCA) caused by ventricular fibrillation (VF) or ventricular tachycardia (VT).
We used a multicentre, randomised, single blind, parallel groups design to compare titrated and standard oxygen therapy in adults resuscitated from VF/VT OHCA. The intervention commenced in the community following ROSC and was maintained in the emergency department and the Intensive Care Unit. The primary end point was the median oxygen saturation by pulse oximetry (SpO₂) in the pre-hospital period.
159 OHCA patients were screened and 18 were randomised. 17 participants were analysed: nine in the standard care group and eight in the titrated oxygen group. In the pre-hospital period, SpO₂ measurements were lower in the titrated oxygen therapy group than the standard care group (difference in medians 11.3%; 95% CI 1.0–20.5%). Low measured oxygen saturation (SpO₂ < 88%) occurred in 7/8 of patients in the titrated oxygen group and 3/9 of patients in the standard care group (P = 0.05). Following hospital admission, good separation of oxygen exposure between the groups was achieved without a significant increase in hypoxia events. The trial was terminated because accumulated data led the Data Safety Monitoring Board and Management Committee to conclude that safe delivery of titrated oxygen therapy in the pre-hospital period was not feasible.
Titration of oxygen in the pre-hospital period following OHCA was not feasible; it may be feasible to titrate oxygen safely after arrival in hospital.

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^☆: A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2012.08.330.

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Short communicationDelivery of titrated oxygen via a self-inflating resuscitation bag☆

Abstract

Aim

Methods

Results

Conclusions

Introduction

Section snippets

Study design

Technical information

Results

Discussion

Conclusion

Conflicts of interest statement

Acknowledgements

Resuscitation

Resuscitation

Resuscitation

Rev Bras Anestesiol

Short communication
Delivery of titrated oxygen via a self-inflating resuscitation bag☆