BLS 2721 CPR in Microgravity Environments - SyR

Conflict of Interest Declaration

The following Task Force members and other authors declared an intellectual conflict of interest, and this was acknowledged and managed by the Task Force Chairs and Conflict of Interest Committee: Stevan Gilmore is an employee of National Aeronautics and Space Administration (NASA) and has published a manuscript related to CPR techniques in microgravity conditions which is included in this review. No other COI. His employment and intellectual COIs were managed by prohibiting his participation in hierarchical selection and data abstraction and Task Force meetings.

CoSTR Citation

Norii T, Gilmore S, Ishibashi T, Bolton K, Garcia C, Soar J, Morrison L, Bray J, on behalf of the International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force and Advanced Life Support Task Force. Cardiopulmonary Resuscitation in Microgravity Environments: A Systematic Review, Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force, 2026 November 5.

Background

This nodal review, conducted by the Basic Life Support (BLS) and Advanced Life Support (ALS) Task Forces, is the first systematic review on cardiopulmonary resuscitation (CPR) in microgravity environments undertaken by the International Liaison Committee on Resuscitation (ILCOR).

There was no prior ILCOR review on this topic, and the search strategy was developed in collaboration with an information specialist from Monash University and informed by search strategies used in previous systematic and scoping reviews on similar topics.1,2 The key search terms and complete search strategy are presented in Supplement. The search strategy was peer-reviewed and approved by the ILCOR Basic Life Support Task Force, and the protocol was registered in PROSPERO (CRD420251182213).3

The ILCOR BLS and ALS Task Forces considered all identified evidence when formulating the treatment recommendations. Key discussion points and highlights from the evidence-to-decision process are described below. The data tables and evidence-to-decision framework are provided as attachments.

Review Citation

Norii T, Gilmore S, Ishibashi T, Bolton K, Garcia C, Soar J, Morrison L, Bray J, on behalf of the International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force and Advanced Life Support Task Force. Cardiopulmonary Resuscitation in Microgravity Environments: A Systematic Review “in draft”

PICOST

The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe) 

Population:  Adults and children experiencing cardiac arrest in microgravity environments

Intervention: CPR techniques developed for microgravity (e.g., the Reverse Bear Hug method, Evetts–Russomano method) or mechanical CPR devices

Comparators:  A different CPR technique

Outcomes: Critical outcomes: Survival at 30 days or hospital discharge with a favorable neurological outcome, and survival at 30 days or hospital discharge

Important outcomes: Return of spontaneous circulation (ROSC), any measure of CPR quality (e.g., chest compression depth, rate, recoil), injuries to rescuers, rescuer fatigue

Study Designs:  Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies, and case series with ≥10 patients) are included. Manikin, animal, cadaver studies will only be included if insufficient human studies are identified. Unpublished studies (e.g., conference abstracts, trial protocols) are excluded. All relevant publications in any language are included as long as there is an English abstract.

Timeframe:  All years. The literature search was conducted from database inception to October 26, 2026.

Registration: PROSPERO Registration CRD420251182213

Consensus on Science

The search strategy was executed using MEDLINE, EMBASE, and Cochrane library on January 27 and October 26, 2026. The systematic review search identified 260 records, of which 41 studies were selected for full-text screening.

No clinical studies on patient outcomes were identified. Therefore, manikin-based simulation studies and animal studies were considered for inclusion, as prespecified.4-18 Among the 15 studies that evaluated CPR techniques developed for microgravity or use of mechanical chest compression devices in microgravity, eight did not compare two or more CPR techniques under microgravity conditions and were therefore excluded from this analysis.6,7,9-11,13,14,18 The remaining seven studies included six simulation studies4,8,12,15-17 and one animal study (Table).5

Among the seven included studies, one animal study involved 11 swine5 and six simulation studies involved 63 human participants4,8,12,15-17 The studies evaluated seven CPR techniques, including Handstand or Vertical-Inverted position (Handstand) method (n = 5),4,5,8,12,16 Reverse Bear Hug method (n = 4),4,8,12,17 Evetts–Russomano method (n = 3),8,12,17 Schmitz–Hinkelbein method (n = 2),15,17 Cologne method (n = 2),15,17 Standard Side Straddle or conventional CPR with restrain (Standard Side Straddle) (n = 2),4,5 and Waist Straddling (n = 1)4 and mechanical chest compression devices (n = 1).16 While some techniques (e.g., Evetts–Russomano method) can be performed without patients being restrained, some techniques (e.g., Handstand method) typically require patients restrained on the Crew Medical Restraint System (CMRS) or their equivalent (Table). Among the seven included studies, three used parabolic flight,4,5,16 two used ground-based body-suspension and/or trolley systems,8,12 and two used underwater simulation;15,17 none was conducted aboard an orbiting spacecraft.

Critical outcomes

For the critical outcomes of survival with favorable neurological outcome at 30 days or hospital discharge and overall survival at 30 days or hospital discharge, no clinical evidence was identified.

Return of spontaneous circulation

For the important outcome of return of spontaneous circulation, no clinical evidence was identified.

CPR quality

We identified very-low-certainty evidence (downgraded due to serious risk of bias, inconsistency, indirectness, and imprecision) for the important outcome of CPR compression quality from six simulation studies and one animal study.4,5,8,12,15-17

Standard Side Straddle vs Handstand:

Two studies compared the Standard Side Straddle method with the Handstand method during microgravity produced by parabolic flight.4,5 Overall, the Handstand method produced greater compression depth in the manikin study; however, this was insufficient to meet chest compression depth criteria of 50-60 mm. The animal study suggested that the two methods produced comparable short-term physiological effects:

• In the manikin study, the Handstand method produced substantially greater compression depth than the Standard Side Straddle method (40.1 ± 5.1 vs 19.8 ± 11.2 mm), while compression rates were similar (98.3 ± 6.3 vs 100.0 ± 3.0 compressions/min, respectively).4

• In the swine study, CPR effectiveness was evaluated indirectly using physiological parameters, including end-tidal carbon dioxide (EtCO₂), oxygen saturation, and intra-arterial blood pressure.5 The study found no significant differences in these physiological parameters between the Standard Side Straddle method, and the Handstand method. Both methods maintained EtCO₂ above 25% of prearrest values, the study’s prespecified benchmark for effective CPR.5

Waist Straddling vs Handstand:

One study compared the waist-straddling method with the Handstand method and assessed chest-compression quality.4 During microgravity produced by parabolic flight, the Handstand method produced greater compression depth than the waist-straddling method (40.1 ± 5.1 vs 30.7 ± 11.9 mm), while compression rates were similar (98.3 ± 6.3 vs 102.6 ± 12.1 compressions/min, respectively). The Handstand method was superior for achieving greater compression depth however this was insufficient to meet chest compression depth criteria of 50-60 mm, whereas compression rate was comparable between the two methods and achieved the recommended compression rate of 100-120 compressions/min.

Handstand vs Evetts–Russomano:

Two studies directly compared the Handstand and Evetts–Russomano methods in simulated microgravity.8,12 Overall, the Handstand method consistently generated deeper chest compressions, whereas Evetts–Russomano more consistently achieved the recommended compression rate; neither technique consistently met chest compression depth quality criteria of 50-60 mm:

• In Kordi et al., the Handstand method produced greater compression depth than Evetts–Russomano method (47.3 ± 1.2 vs 42.3 ± 5.6 mm), while compression rates were 124.6 ± 15.2 vs 103.5 ± 4.7/min, respectively.8

• Similarly, Rehnberg et al. found greater “true” compression depth (DT) with the Handstand (49.3 ± 1.2 vs 37.4 ± 1.5 mm). DT was calculated as DMax−DIRecoil, where DMax​ is the maximum compression depth and DIRecoil is the depth remaining because of incomplete recoil between compressions. However, Evetts–Russomano method provided a more guideline-concordant compression rate compared with the Handstand method (105.6 ± 0.8/min vs 91.9 ± 2.2).

Handstand vs Reverse Bear Hug:

Three studies compared the reverse bear hug method with the Handstand method.4,8,12 Overall, the Handstand method consistently produced greater compression depth however this was insufficient to meet quality depth criteria of 50-60 mm, while findings for compression rate for both techniques were inconsistent:

• During microgravity produced by parabolic flight, Jay et al. found greater compression depth (40.1 ± 5.1 vs 36.8 ± 6.4 mm) and rate (98.3 ± 6.3 vs 89.3 ± 4.1 compressions/min) with the Handstand method.4

• In the two ground-based studies, in which microgravity was simulated using body-suspension/trolley systems, the Handstand method similarly produced greater compression depth than the reverse bear hug method (47.3 ± 1.2 vs 41.7 ± 6.2 mm and 49.3 ± 1.2 vs 23.9 ± 1.4 mm); compression rates were 124.6 ± 15.2 vs 98.0 ± 5.6 and 91.9 ± 2.2 vs 101.3 ± 1.5 compressions/min, respectively.8,12

Evetts–Russomano vs Reverse Bear Hug:

Three studies compared the Evetts–Russomano method with the Reverse Bear Hug method in simulated microgravity.8,12,17 Two used ground-based body-suspension systems,8,12 whereas one used underwater simulation.17 Overall, the Evetts–Russomano method generally produced greater compression depth however this was insufficient to meet quality depth criteria of 50-60 mm, in studies using ground-based body-suspension systems. However, this advantage was not reproduced in the underwater-simulation study, in which neither method reliably produced adequate CPR quality under simulated microgravity:

• In the two body-suspension studies, the Evetts–Russomano method produced greater compression depth than the reverse bear hug method (42.3 ± 5.6 vs 41.7 ± 6.2 mm and 37.4 ± 1.5 vs 23.9 ± 1.4 mm) and higher compression rates (103.5 ± 4.7 vs 98.0 ± 5.6 and 105.6 ± 0.8 vs 101.3 ± 1.5 compressions/min).8,12

• In the underwater-simulation study, both methods resulted in less than 5% correct chest compressions.17

Cologne vs Schmitz–Hinkelbein:

Two studies compared the Cologne method with the Schmitz–Hinkelbein method using underwater simulation of microgravity.15,17 Overall, the Schmitz–Hinkelbein method demonstrated better compression performance, although neither method consistently provided adequate CPR quality in simulated microgravity:

• In Schmitz et al., the Schmitz–Hinkelbein method resulted in a greater proportion of compressions with correct depth (65 ± 23% vs 28 ± 27%) and a higher mean compression rate (111.1 ± 6.3 vs 102.0 ± 8.3 compressions/min).15

• In Vanni et al., the Schmitz–Hinkelbein method also achieved a higher compression rate (86 [58–103] vs 73 [71–89] compressions/min); however, correct chest compressions, defined as a depth of 50-60 mm with complete chest recoil, were extremely uncommon with both methods (0 [0–2]% vs 0 [0–1]%, respectively).17

Cologne vs Evetts–Russomano:

One underwater-simulation study compared the Cologne and Evetts–Russomano methods.17 Overall, neither method reliably met chest-compression quality, and both produced compression rates below the guideline-recommended range:

• The median compression rate was higher with the Cologne method than with the Evetts–Russomano method (73 [71–89] vs 59 [56–71] compressions/min). However, the median percentage of correct chest compressions was lower with the Cologne method than with the Evetts–Russomano method (0 [0–1]% vs 1.8 [1–5]%).

Cologne vs Reverse Bear Hug:

One underwater-simulation study compared the Cologne with Reverse Bear Hug.17 The Cologne method produced a higher median compression rate than the Reverse Bear Hug method (73 [71–89] vs 69 [45–92] compressions/min), whereas the median percentage of correct compressions was lower with the Cologne method than with the Reverse Bear Hug method (0 [0–1]% vs 2 [0–5]%). Overall, neither method met adequate chest-compression quality, and both produced compression rates below the guideline-recommended range.

Evetts–Russomano vs Schmitz–Hinkelbein:

The same underwater-simulation study compared the two methods.17 The Evetts–Russomano method produced a lower median compression rate than the Schmitz–Hinkelbein method (59 [56–71] vs 86 [58–103] compressions/min), whereas the median percentage of correct compressions was higher with the Evetts–Russomano method (1.8 [1–5]% vs 0 [0–2]%). Overall, neither method met adequate chest-compression quality, and both produced compression rates below the guideline-recommended range.

Reverse Bear Hug vs Schmitz–Hinkelbein:

The same underwater-simulation study compared the two methods.17 The Reverse Bear Hug method produced a lower median compression rate than the Schmitz–Hinkelbein method (69 [45–92] vs 86 [58–103] compressions/min), whereas the median percentage of correct compressions was higher with the Reverse Bear Hug method (2 [0–5]% vs 0 [0–2]%). Overall, neither method met adequate chest-compression quality, and both produced compression rates below the guideline-recommended range.

Mechanical chest compression device vs Handstand:　

One study compared automatic chest-compression devices with the Handstand method during microgravity produced by parabolic flight.16 Reynette et al. compared three devices with the Handstand method. Compression depths were 53 [53–54] mm with LUCAS 3, 29 [26–32] mm with EASYPULSE, and 29 [27.5–30.7] mm with AUTOPULSE, compared with 34.5 [29.6–43.3] mm with the Handstand method. Corresponding compression rates were 101 [101–101], 100 [100–100], 80 [80–80], and 115 [109–123] compressions/min, respectively. Only LUCAS 3 consistently met the recommended compression depth of ≥50 mm. LUCAS 3, EASYPULSE, and the Handstand method delivered rates within the 100–120 compressions/min guideline range and AUTOPULSE delivered compressions at the preset device rate of 80 compressions/min.

Rescuer fatigue

For the important outcome of rescuer fatigue, we identified very-low-certainty evidence from two ground-based simulation studies, one underwater study and one animal study.5,8,12,17 The evidence was downgraded because of serious risk of bias, inconsistency, indirectness, and imprecision. Three simulation studies assessed perceived exertion using the Borg scale,19 ranging from 6 (no exertion) to 20 (maximal exertion), and measured rescuer heart rate.8,12,17 One study additionally measured oxygen consumption and minute ventilation.12 The animal study qualitatively described rescuer fatigue during the Handstand and Standard Side Straddle methods in the microgravity environment created with parabolic flights.

Standard Side Straddle vs Handstand:

One animal study compared the Standard Side Straddle method, described in the study as “conventional restrained CPR,” with the Handstand method during parabolic flight.5 Rescuer fatigue was assessed only qualitatively, without a validated scale or other formal measurement. The investigators reported that the Standard Side Straddle method required substantial physical effort and was quickly fatiguing, whereas the Handstand method required less effort and was less fatiguing.

Handstand vs Evetts–Russomano:

Two studies compared rescuer fatigue between the Handstand and Evetts–Russomano methods in ground-based simulated microgravity.8,12 In both studies, the Evetts–Russomano method was performed with the rescuer and manikin fully suspended using a body-suspension device, whereas the Handstand method was simulated using a horizontally moving trolley positioned between two fixed walls. Overall, both subjective and physiological measures indicated that the Handstand method imposed less rescuer fatigue and physiological workload than the Evetts–Russomano method:

• In Kordi et al.,8 the mean Borg score was lower with the Handstand method (13.7 vs 15.8); the mean increase from resting heart rate was also lower with the Handstand method (35.7 vs 71.2 beats/min).

• In Rehnberg et al.,12 the corresponding mean Borg scores were 13.7 and 16.3, and the mean heart rates after CPR were 123.3 and 150.6 beats/min, respectively. The same study also reported lower mean oxygen consumption (27.47 vs 35.85 mL/kg/min) and minute ventilation (39.89 vs 58.38 L/min) with the Handstand method.

Evetts–Russomano vs Reverse Bear Hug:

The same two studies compared rescuer fatigue between the Evetts–Russomano and Reverse Bear Hug methods in ground-based simulated microgravity.8,12 Overall, the Evetts–Russomano method was associated with lower perceived exertion but generally greater physiological workload than the Reverse Bear Hug method, indicating that subjective and objective measures of rescuer fatigue were not fully consistent:

• Kordi et al.,8 the mean Borg score was lower with the Evetts–Russomano method than with the Reverse Bear Hug method (15.8 vs 17.1), although the mean increase from resting heart rate was greater with the Evetts–Russomano method (71.2 vs 65.4 beats/min); neither difference was statistically significant.

• In Rehnberg et al. ,12 perceived exertion was also lower with the Evetts–Russomano method (mean Borg score, 16.3 vs 18.2), whereas mean heart rate after CPR was higher (150.6 vs 145.7 beats/min). Mean oxygen consumption was higher with the Evetts–Russomano method than with the Reverse Bear Hug method (35.85 vs 25.45 mL/kg/min), as was mean minute ventilation (58.38 vs 48.24 L/min).

Good Practice Statement

1. We suggest that, for adults in cardiac arrest in a microgravity environment, the patient is restrained on a Crew Medical Restraint System (CMRS) or equivalent fixed surface as soon as possible, and that chest compressions are given using a method proven to provide guideline compliant compression rate and depth in microgravity when the cabin layout permits (good practice statement).
2. We suggest that, until the patient can be restrained, chest compressions are given using a method in which the rescuer stabilizes the patient with their own body and the method has been proven to provide guideline compliant compression rate and depth in microgravity (good practice statement).
3. We suggest that a mechanical chest compression device that has been proven to deliver guideline-compliant compression depth in microgravity may be used when available and when sustained high-quality manual chest compressions are impractical (good practice statement).

Justification and Evidence to Decision Framework Highlights

This topic was prioritized by the BLS and ALS Task Forces based on the recent growth in commercial space tourism, planned crewed missions to the Moon and Mars, and the publication of guidelines by several international organizations, including the European Resuscitation Council (ERC), addressing resuscitation in microgravity environments.20,21

In this systematic review, we identified no eligible clinical studies, thus, manikin simulation and animal studies were included. We identified one animal study and six simulation studies evaluating a total of seven techniques and the use of mechanical chest compression devices in microgravity environments; the certainty of evidence for all CPR techniques was very low. There is insufficient evidence to suggest that one method is superior to another. No studies were identified for chest compressions in children.

The review identified two categories of non-standard CPR techniques that can be performed in the microgravity environments, namely, CPR techniques not requiring Crew Medical Restraint System (CMRS) and CPR techniques requiring CMRS. The major advantage of CPR techniques that do not require the CMRS is that they can be performed without additional equipment. However, these techniques are difficult to sustain for an extended period and are considered temporary measures. In contrast, the Handstand method which requires CMRS provided higher-quality compressions but cannot be initiated until the patient is moved to the area equipped with CMRS. Thus, CPR methods not requiring CMRS would still play a role as a temporary measure until the patient is moved to the area with CMRS.

Regarding CPR quality, we recognized that the currently available evidence is extremely limited and is based on simulation studies, highlighted by the absence of clinical studies. Only a limited number of studies directly compared CPR methods in simulated microgravity settings. None of the methods consistently met current CPR quality metrics for depth and rate across comparisons. The Handstand method, which requires the patient to be stabilized using a CMRS or comparable restraint setup, produced greater compression depths than the other methods, although the findings for compression rate were not consistent. However, a CMRS is not available in many locations; for example, it is installed only in the U.S. laboratory module of the International Space Station (ISS). Among techniques that do not require CMRS, the Evetts–Russomano method generally produced greater compression depths and higher compression rates than the Reverse Bear Hug method in studies using ground-based body-suspension systems.8,12 However, in the underwater-simulation study, neither method reliably produced high-quality CPR in simulated microgravity.17 As such, it might be reasonable to start with Evetts–Russomano method, then transition to Handstand method when the patient is moved to the place where CMRS is available, which is consistent with recommendations in the guideline from the German Society of Aerospace Medicine and the European Society of Aerospace Medicine Space Medicine Group.21

We recognized that the feasibility of the Handstand method depends on cabin configuration. One study conducted during actual spaceflight aboard the Dragon spacecraft, which has less cabin space than the International Space Station, evaluated a technique similar to the Handstand method.18 The study was not included in the analysis because it did not compare different CPR methods. In the study, astronauts were positioned upside down, with their buttocks and legs braced against the cabin ceiling; the precise configuration varied by seat location. Using a CPR Adult Manikin Bellows Piston with Clicker, all four astronauts achieved the target compression rate, with individual rates ranging from 102 to 114 compressions/min. However, one operator stopped after approximately 45 seconds because of an inability to use the legs effectively for force generation and substantial arm fatigue. In the Discussion, the authors noted that shorter astronauts performed compressions with their arms more fully extended above their heads, in a position comparable to a shoulder press, whereas taller astronauts held their arms farther in front of their bodies, in a position comparable to a push-up. These observations suggest that the interaction between operator anthropometry and cabin geometry may influence positioning and fatigue.

Regarding the potential implementation of mechanical chest-compression devices in microgravity environments, the task force discussed the substantial costs associated with transporting such devices to the ISS or installing them in other spacecraft. Nevertheless, given that the ISS is already equipped with resuscitation resources, including an automated external defibrillator (AED) and medications such as epinephrine, the addition of a mechanical chest-compression device may warrant consideration.

The task forces discussed the timing of transferring patients from microgravity to a 1G environment, given that studies have consistently shown that delivering high-quality CPR in microgravity is more difficult and causes greater rescuer fatigue than delivering CPR in a 1G environment.7,9–13 For example, in a 3-minute evaluation of the Evetts–Russomano method, mean Borg scores increased from 13.3 in the first minute to 17.9 in the third minute during simulated microgravity, compared with an increase from 9.1 to 10.8 during terrestrial CPR.7 Mean rescuer heart rate increased concurrently from 153.9 to 174.5 beats/min during simulated microgravity, compared with an increase from 110.9 to 114.8 beats/min during terrestrial CPR. Additionally, Menon et al. evaluated a method similar to the Handstand method during actual spaceflight as discussed above and reported that one of four astronauts was unable to complete the full 2 min of compressions due to significant fatigue.18 Strategies for transferring patients to a 1G environment would differ substantially depending on the spaceflight context, such as short-duration commercial spaceflights versus crewed missions to the Moon or Mars. Each context would therefore require specific logistical considerations.

Regarding rescuer injuries, we identified no evidence from the seven included studies on injuries directly attributable to CPR methods in microgravity environments. The study conducted by Menon et al. during actual spaceflight assessed spacecraft-related effects by measuring cabin carbon dioxide (CO₂) concentrations and vehicle acceleration.18 Cabin CO₂ concentrations peaked above 3.6 mm Hg, triggering a caution threshold, and accelerations were detected along all three axes. No crew members reported symptoms potentially associated with elevated CO₂ concentrations, including headache. Additional research is needed to characterize the safety of CPR methods, potential rescuer injuries, and environmental hazards during resuscitation in microgravity.

The task forces also discussed the need for future reviews of other core components of resuscitation, including, but not limited to, defibrillation and ventilation, as well as the availability of medical equipment and training needs. There was discussion regarding very early use of an AED given the challenges of providing effective chest compressions. In addition, the task forces considered whether specific outcomes applicable to cardiac arrest in microgravity should be developed, such as “survival to Earth.”

Knowledge Gaps

1. There was a lack of clinical studies evaluating different CPR techniques in a microgravity environment. The TF acknowledged that clinical studies may be challenging to complete.
2. No studies of CPR techniques in microgravity in children.
3. Evidence was limited regarding the quality of CPR during prolonged resuscitation in microgravity. Several studies evaluated CPR techniques only briefly because of limitations in sustaining microgravity, restricting the applicability of their findings to prolonged resuscitation.
4. Few studies assessed the duration or clinical impact of interruptions in chest compressions associated with positioning rescuers and configuring equipment during the transition to equipment-assisted resuscitation.
5. The time required to retrieve, deploy, and apply the Crew Medical Restraint System and other resuscitation equipment, and the clinical impact of interruptions in chest compressions in spacecraft with limited cabin space, remain uncertain.

Data Tables

BLS 2721 Evidence to Decision Table EtD_October2026

BLS 2721 Table List of non standard CPR techniques evaluated in the microgravity setting v2 0

References

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