Prone Cardiopulmonary Resuscitation

Anatomy and Physiology

The cardiovascular, respiratory, and cerebrovascular systems are primarily impacted during cardiac arrest. CPR aims to restore these systems' functions as soon as possible after cardiac arrest.

Cardiovascular System

The cardiovascular system comprises the heart and blood vessels. The heart receives de-oxygenated blood from body tissues through the inferior and superior vena cava and transfers it to the lungs for oxygenation through the pulmonary arteries. Oxygenated blood is transferred to the heart through the pulmonary veins and pumped to the body through the aorta. The coronary arteries supply the heart with blood, oxygen, and nutrients.

Cardiac arrest may result from myocardial infarction due to the obstruction of blood supply to the heart or medical conditions that alter the heart's normal function. Arrhythmias such as pulseless ventricular tachycardia and ventricular fibrillation (VT/VF) cause fatal abnormal electrical activity of the heart, significantly compromising the cardiac output and leading to cardiac arrest.

CPR aims to restore and ensure circulation and coronary blood flow through chest compressions and defibrillation with electric shock in the case of VT/VF. Successful cardioversion in cases of VT/VF in the prone position has been reported, and the need to turn the patient to a supine position may not be necessary.[5]

Few studies have suggested that prone CPR may be more effective than standard CPR in the supine position. In a pilot feasibility study, six adult ICU patients who had failed a 45-minute-long standard CPR were switched to prone CPR prone. There was a significant improvement in systolic and mean arterial blood pressures. However, none of the patients had a return of spontaneous circulation.[6] 

Wei et al., using cadavers, also demonstrated that prone CPR generated greater systolic (79.4mmhg vs. 55.4 mmHg) and diastolic (16.7 mmHg vs. 13.0 mmHg) blood pressures compared with CPR in the supine position.[7] In addition, reports suggest that prone CPR may provide higher end-tidal CO2 (ETCO2) pressure than supine position CPR.[8][9] 

The less forward movement of the abdomen and its structures due to the contact with a dense surface during prone CPR may improve the effectiveness of chest compressions compared with CPR in the supine position.[10] However, more research is warranted to generate more substantial evidence.

Respiratory System

The respiratory system encompasses the upper and lower airways, the lungs, and the muscles of respiration. The respiratory system's primary function is to bring oxygen into the body for tissue oxygenation and eliminate carbon dioxide (CO2). Any condition that impairs the ability of the respiratory system to perform these functions efficiently may cause cardiac arrest.[11] 

If tissue hypoxia and gaseous exchange are not managed effectively during CPR, metabolic acidosis ensues, which impairs the effectiveness of chemical and electrical therapy. Therefore, 100% inspired oxygen is recommended during CPR to maximize arterial blood oxygen saturation and systemic oxygen delivery. Well-fitting masks and bag valve devices can achieve ventilation during prone CPR.[12] 

The prone position is associated with better ventilation-perfusion match, reduced shunts and increased airway patency, and intra-thoracic variations with improved oxygenation and ventilation, which may contribute to favorable CPR outcomes. Regurgitation and aspiration of abdominal contents are well-known complications of CPR in the supine position, which are minimized in the prone position CPR.[10]

Cerebrovascular System

The cerebrovascular system includes the brain and the spinal cord. The medulla is a part of the brain stem that controls essential survival functions, including breathing, regulation of oxygen and CO2 exchange, heart rate, rhythm, and circulatory blood pressure.[13][14]

The nucleus of the solitary tract (NTS) in the medulla receives neuronal signals from stretch receptors in the lungs and aortic baroreceptors in the carotid bodies. Information is relayed from the NTS to respiratory and cardiovascular centers in the medullary reticular formation for appropriate breathing and blood pressure regulation.

Dysregulation of this mechanism by any condition can cause cardiac arrest. During CPR, blood and oxygen are inefficiently delivered to the brain, causing anoxic brain injury that worsens with CPR duration. Therefore, prompt initiation of CPR in prone patients is necessary to improve survival and prevent irreversible neurological damage in patients that survive.[15][4]

Indications

Prone CPR is indicated in patients with cardiac arrest while in the prone position for oxygenation, ventilation, or surgical procedures.

Scientific Guideline Recommendations

The 2010 AHA guidelines for CPR and ECC recommend that in hospitalized patients with an advanced airway, CPR in the prone position may be reasonable when the patient cannot be placed in the supine position.[4] However, this was not included in the updated 2015 and 2020 guidelines.[16] 

The 2014 United Kingdom Resuscitation council guidelines recommend that chest compressions be started on patients with cardiac arrest during neurosurgery without changing their position from prone to supine. However, the patient should be turned supine if chest compressions are ineffective based on the ETCO2 and capnography waveforms.[17]

The current COVID-19 pandemic has brought prone CPR to the front because many patients with COVID-19 ARDS require ventilation in the prone position and are at risk of cardiac arrest.[18]

Several scientific societies released interim guidance and joint statements on prone CPR recommendations in COVID-19 patients. The AHA recommends resuscitation in the supine position for non-sedated COVID-19 patients with no advanced airway in a prone position (awake-prone ventilation). In patients with an advanced airway present before cardiac arrest, the AHA recommends that it may be reasonable to perform prone CPR unless able to turn the patient supine without the risk of aerosolization or disconnection from the mechanical ventilator and other equipment.[19] 

The European Resuscitation Council (ERC) has similar recommendations in its COVID-19 guidelines with additional suggestions to turn patients supine if unable to effectively perform chest compressions, presence of airway complications, or delay in achieving ROSC.[20] 

The Brazilian societies of cardiology, intensive care medicine, anesthesiology, and emergency medicine, in a joint position statement on resuscitation of COVID-19 patients, recommends turning patients into the supine position once it is safely possible due to limited evidence on prone CPR. Additionally, the effectiveness of CPR should be monitored using goal diastolic pressure > 20 mmHg and ETCO2 pressure  > 15 mmHg.[21]

Contraindications

There are no contraindications to performing CPR in the prone position. However, most providers are trained to perform CPR in the conventional supine position and might be reluctant to perform prone CPR due to a relative lack of knowledge and experience of the procedure.

Equipment

The types of equipment required for prone CPR include:

1. Oxygen masks and bag valve devices
2. Defibrillators with electrodes and pads
3. A crash cart containing medications such as epinephrine/adrenaline, atropine, amiodarone, naloxone, and other resuscitation drugs. Other equipment that should be included in the cart are tapes, gloves, scissors, an intravenous cannula, syringes and needles, saline flush, and intravenous fluids.
4. Suction system
5. Endotracheal tubes
6. Mechanical ventilators

Personnel

Prone CPR in the hospital setting is usually performed by an interdisciplinary healthcare team that includes physicians, pharmacists, nurses, respiratory therapists, laboratory staff, and other ancillary staff. Prone CPR in the operating room during surgery should not be delayed while waiting for the cardiac arrest team to arrive. Instead, CPR should be initiated immediately by the healthcare staff present during surgery which usually includes the surgeon, anesthesiologist, nurses, and surgical assistants.

Preparation

Patients treated in the prone position are at risk of cardiac arrest. Therefore, the bedside nurses, primary physicians, and the cardiac arrest team should be well prepared. The necessary equipment for CPR should be available inside or close to the patient's room. Defibrillation pads can be placed in the recommended positions on the prone patient and connected to the electrical rhythm monitor before cardiac arrest occurs.

The patient's room should be cleared of any materials that may obstruct the smooth flow of the CPR process. Cardiac arrest team members and healthcare staff involved in managing patients in prone positions should be trained to perform prone CPR.

Technique or Treatment

The CPR algorithm in prone and supine positions is similar. The significant differences are the position of the hands for compressions and the placement of defibrillation pads in the prone position. Most available evidence guiding the CPR technique in the prone position is from case reports.[22][23][24][25] 

The patient is positioned with the chest, and anterior abdominal wall laying on a solid surface and arms under the forearm with the elbows flexed at 90 degrees. The provider performing chest compressions will place the hypothenar region of one hand above the patient's thoracic vertebrae, and the other is placed over the first in an interlocking position (Figure 1a). External counterpressure on the chest is generally recommended for effective chest compressions. Sternal counter pressure may be achieved with sandbags and 1-liter fluid bags under the patient's chest or by a second provider placing a hand on the patient's chest (Figure 1b).

Effective chest compression is an essential component of CPR algorithms. Thoracic compressions should be focused on the area located 0-2 vertebra segments below the inferior angle of the scapula corresponding to T8-T9 (figure 1b). A 2017 study of 100 people in the prone position using a computerized tomography scan showed that this region ensured direct access to the largest left ventricular cross-sectional area in more than 80% of people.[26] 

It is important to note that prone-position CPR should be similar to conventional CPR, with a compression rate of 100 to 120 per minute and a depth of at least 2 inches in adults and at least one-third of the anteroposterior dimension of the chest in infants.[27][28] In addition, an end-tidal CO2 (ETCO2) goal of at least 10 to 15 mmHg should be used to assess the effectiveness of compressions.[16]

In the absence of an advanced airway, two breaths should be delivered via face masks or bag valve devices after every cycle of 30 compressions if one person is performing the CPR and every 15 compressions if there are two or more rescuers.[29] The aim is to minimize interruptions in chest compressions during CPR. If there is an advanced airway like an endotracheal tube, 8 to 10 breaths can be delivered every minute without pausing chest compressions.[29]

Defibrillation is recommended in patients with shockable rhythms (pulseless ventricular tachycardia and ventricular fibrillation).[16] Defibrillator pads should be placed in locations that expose the myocardium to sufficient energy. The pads can be placed in the anterior-posterior position (figure 2a), bi-axillary (figure 2b), or in the posterolateral position (figure 2c), with one pad in the left or right mid-axillary line and the second one over the right or left scapula.[5][30]

Complications

During prone CPR, pressure injuries to the ribs, clavicles, scapula, shoulder joints, spine, and eyeballs are common. In addition, accidental endotracheal or tracheostomy tube dislodgements could occur during prone CPR, and the patient may have to be turned for re-intubation, which will adversely impact the quality of the CPR process. During surgical procedures, chest compressions may be challenging to perform in an open surgical field, and a counterforce on the sternum may be needed.

Clinical Significance

Cardiac arrest in the prone position is not uncommon and likely to increase because of the COVID-19 pandemic, as ventilation in the prone position is increasingly being used for critically ill intubated and sedated patients as well as in non-sedated patients receiving non-invasive ventilation. Initiating CPR in the prone position is feasible and may improve outcomes, particularly when turning the patient to a supine position is impossible.[30][31][32]

Enhancing Healthcare Team Outcomes

Despite improvements in the resuscitative care of IHCA over the past decade, survival outcome is still poor, with only about 22-25% surviving to hospital discharge.[33] This outcome may be worse in prone cardiac arrest patients because they tend to be sicker, and there is no standard guideline on prone CPR.[10] 

Hospitals with dedicated cardiac arrest response teams have been shown to have better survival cardiac arrest outcomes.[34][35] Sometimes, the team works with other healthcare personnel to identify patients at risk of IHCA early and initiate life-saving treatment modalities.[34][35]

The AHA Guidelines for CPR and ECC have consistently recommended the formation of cardiac arrest teams at hospitals to prevent and respond to IHCA based on evidence from systematic reviews and cohort studies.[12][36]

Though no clinical trials have evaluated cardiac arrest response teams, there are published assessments of IHCA response teams at top-performing hospitals.[34][35][37] Below are some of the recommended qualities of successful teams.

1. Teams should include diverse disciplines across all levels of expertise
2. Team members should have clearly defined roles and responsibilities focusing on the components of CPR, including intravenous access, administration of drugs, chest compressions, and airway management.
3. Team members should undergo periodic training on prone CPR and practice mock codes in actual patient rooms and high-risk wards.
4. Teams should conduct post-resuscitation debriefings to identify any problems with the response and areas for improvement.
5. Emphasize and reinforce best practices

Future Research and Considerations

1. Though clinical trials to assess the efficacy of prone CPR are limited by ethical concerns, adequately designed cohort and feasibility studies are needed to provide evidence-based guidance, particularly on controversial aspects such as the decisional algorithm for supination and the best sternal counterpressure.
2. Randomized trials are needed to provide robust evidence on the long-term outcome of patients that underwent prone CPR. Unfortunately, most current evidence is from case reports/series and nonrandomized studies.
3. There is a need for scientific societies to standardize their guidelines and recommendations on the protocol for performing CPR in the prone position.
4. Without a standard national guideline, hospitals could develop institution-specific protocols for prone CPR based on the available evidence to support clinical practice.
5. Multidisciplinary healthcare personnel caring for prone patients would benefit from periodic training on prone CPR.