Artificial Ventilation and Cardiopulmonary Resuscitation

Introduction

Artificial ventilation and cardiopulmonary resuscitation are lifesaving interventions used to restore and maintain adequate oxygenation, ventilation, and circulation during respiratory or cardiac arrest. Effective resuscitation requires prompt initiation, proper technique, and simultaneous supportive measures to improve patient survival.

Artificial Respiration

• Artificial respiration or artificial ventilation is the process of providing ventilation to an individual with respiratory arrest until spontaneous breathing is restored.
• Immediate initiation of artificial ventilation is essential because irreversible brain injury may occur within a few minutes of severe oxygen deprivation.
• Artificial ventilation is most effective when cardiac function and systemic circulation are adequately maintained.

Methods of Artificial Ventilation

• Methods of artificial ventilation are broadly classified into mechanical methods and manual methods.

Instrumental (Mechanical) Methods

• Mechanical ventilation is preferred when ventilatory support is required for prolonged periods.
• Mechanical methods are divided into positive-pressure ventilation and negative-pressure ventilation.

Positive Pressure Method

• In positive-pressure ventilation, air or an oxygen-enriched gas mixture is delivered into the lungs under pressure.
• Positive-pressure ventilation is commonly used during anesthesia, surgery, and intensive care.
• This method ensures effective ventilation but may reduce venous return to the heart because of increased intrathoracic pressure.

Negative Pressure Method

This is achieved by alternate compression and relaxing of chest wall. Some of the negative pressure methods are: 1. Drinker’s method, 2. Braggpaul method, and 3. Other method using Boyle’s apparatus.

Drinker’s Method

• The iron lung is a negative-pressure ventilator that encloses the patient’s body while keeping the head and neck outside the chamber.
• Reduction of pressure within the chamber below atmospheric pressure expands the thorax and produces inspiration.
• Restoration or increase of chamber pressure compresses the chest wall, resulting in passive expiration.

Braggpaul Method

• The chest cuirass ventilator consists of a flexible chamber fitted around the thorax.
• Inflation of the chamber compresses the chest wall and produces expiration.
• Release of external pressure allows passive expansion of the thorax, thereby facilitating inspiration.

Boyle’s Apparatus

• Modern hospital ventilators provide automated artificial ventilation.
• These devices allow precise adjustment of respiratory rate, tidal volume, inspiratory pressure, and the composition of inspired gases according to patient requirements.

Manual Methods

• Common manual techniques include mouth-to-mouth ventilation, mouth-to-nose ventilation, and the back pressure-arm lift method.
• Manual ventilation should be initiated promptly and continued until spontaneous breathing resumes or advanced respiratory support becomes available.

Cardiopulmonary Resuscitation

• Cardiopulmonary resuscitation is an emergency procedure performed to restore circulation and ventilation in individuals with cardiac or respiratory arrest.
• Effective cardiopulmonary resuscitation requires prompt initiation and should ideally be performed by trained healthcare personnel or appropriately trained rescuers.

Indications

• Cardiopulmonary resuscitation is indicated in cardiorespiratory arrest, irrespective of the underlying cause.
• Common causes include severe cardiac arrhythmias, acute myocardial infarction, myocarditis, cardiomyopathy, and cardiac tamponade.
• Other indications include electric shock, poisoning, drowning, pulmonary embolism, anaphylaxis, head injury, major trauma, and airway obstruction.
• Cardiorespiratory arrest may also occur during anesthesia, surgical procedures, or following cardiac surgery.
• The most frequent mechanisms of cardiac arrest are asystole and ventricular fibrillation.
• Cardiac arrest should be suspected when a patient becomes unresponsive and shows no signs of normal breathing.
• Absence of a palpable pulse in major arteries, particularly the carotid artery, strongly suggests cardiac arrest.
• Additional clinical features include pallor, cyanosis, agonal gasping, cessation of effective respiration, and dilated pupils.
• Early recognition of cardiac arrest and immediate initiation of cardiopulmonary resuscitation significantly improve survival outcomes.

Objectives of CPR

• The primary objective of cardiopulmonary resuscitation is to maintain adequate pulmonary ventilation and oxygenation.
• Another major objective is to restore and sustain effective cardiac pumping, thereby ensuring sufficient blood flow to vital organs.

Procedure

Steps of CPR

Cardiopulmonary resuscitation is performed in three sequential phases: initial evaluation with basic life support, advanced life support, and post-resuscitation care.

Initial Evaluation and Basic Life Support

Initial Evaluation

• Initial evaluation includes assessment of consciousness, breathing, skin color, and the presence of a central arterial pulse.
• An unresponsive patient with absent or abnormal breathing should be evaluated immediately for cardiac arrest.
• If airway obstruction due to a foreign body is suspected, appropriate airway-clearing maneuvers, such as abdominal thrusts in adults, should be performed to relieve the obstruction.

Basic Life Support

• Basic life support should be initiated immediately in an unresponsive individual because early intervention improves survival.
• The first step is to assess responsiveness by gently tapping the patient and checking for a response.
• Emergency medical assistance should be activated as soon as cardiac arrest is suspected.
• The patient should be placed on a firm, flat surface to permit effective chest compressions.
• The oral cavity should be inspected, and visible obstructions such as vomitus, blood, mucus, or foreign material should be removed carefully.
• Establishing a patent airway is essential for effective resuscitation.
• In patients without suspected cervical spine injury, the airway is opened using the head tilt-chin lift maneuver.
• When cervical spine injury is suspected, the jaw-thrust maneuver is preferred to minimize neck movement.
• Breathing should be assessed by observing chest movements and determining whether normal breathing is present.
• Rescue ventilation is provided if the patient is not breathing or has only agonal gasps.
• Mouth-to-mouth ventilation is commonly used in adults when barrier devices are unavailable.
• During rescue breathing, the rescuer seals the patient’s mouth, occludes the nostrils, and delivers breaths sufficient to produce visible chest rise.
• Excessive ventilation should be avoided because it may increase intrathoracic pressure and reduce venous return.
• Mouth-to-nose ventilation may be used in infants, young children, or when an adequate mouth seal cannot be achieved.
• Mechanical ventilation using a bag-valve-mask device is preferred whenever trained personnel and equipment are available.
• Manual methods, such as the back pressure-arm lift technique, have largely been replaced by modern ventilation methods and are rarely used in current practice.
• These methods may be considered only when standard ventilation techniques are unavailable.
• Circulation is assessed by checking for signs of life and palpating a central pulse, usually the carotid pulse, for no more than 10 seconds.
• Absence of a definite pulse indicates the need for immediate chest compressions.
• External cardiac massage is performed by placing the heel of one hand on the lower half of the sternum, with the second hand positioned on top.
• The rescuer should keep the arms straight and position the shoulders directly above the patient’s chest.
• In adults, the sternum should be compressed to a depth of at least 5 centimeters, but not more than 6 centimeters.
• Chest compressions should be delivered at a rate of 100 to 120 compressions per minute.
• Complete chest recoil should be allowed after each compression to optimize venous return.
• Interruptions in chest compressions should be minimized.
• For a single rescuer providing adult cardiopulmonary resuscitation, the recommended compression-to-ventilation ratio is 30:2.
• If spontaneous circulation returns, rescue ventilation and supportive care should be continued as required until advanced medical care becomes available.

Advanced Life Support

Advanced life support comprises of primary and adjunctive therapies.

Primary Therapies

• Advanced life support includes interventions that restore effective cardiac rhythm, maintain airway patency, and ensure adequate oxygenation.
• The two principal components of primary therapy are defibrillation and advanced airway management.

Defibrillation:

• Defibrillation is the treatment of choice for ventricular fibrillation and pulseless ventricular tachycardia.
• Early defibrillation is a major determinant of survival in sudden cardiac arrest.
• A fibrillating heart cannot generate effective ventricular contractions and therefore fails to maintain adequate circulation.
• Delivery of an electrical shock depolarizes the myocardium simultaneously, allowing restoration of an organized cardiac rhythm.
• Chest compressions should be continued with minimal interruption before and after defibrillation.
• Medications such as adrenaline may be administered during resuscitation according to current advanced life support guidelines.
• Intravenous sodium bicarbonate is not routinely recommended but may be considered in selected situations, including severe metabolic acidosis, hyperkalemia, or tricyclic antidepressant overdose.

Airway management and oxygen therapy:

• Airway management is essential to ensure adequate ventilation and oxygen delivery.
• High-concentration oxygen should be administered as early as possible during resuscitation.
• Endotracheal intubation should be performed by trained personnel when indicated.
• Attempts at intubation should not significantly interrupt chest compressions.

Adjunctive Therapies

• Certain adjunctive therapies may be useful in selected clinical situations.
• Vigorous coughing may transiently maintain circulation in a conscious patient who develops a monitored arrhythmia, but it is not routinely recommended for cardiac arrest.
• A precordial thump has a limited role and may be considered only in witnessed, monitored, unstable ventricular arrhythmias when a defibrillator is not immediately available.
• Atropine is used for symptomatic bradycardia but is no longer recommended for asystole.
• Temporary cardiac pacing may be beneficial in refractory bradyarrhythmias.
• Older manual ventilation methods, such as the Sylvester, rocking, and negative-pressure techniques, are rarely used in modern resuscitation practice.
• Persistent absence of spontaneous circulation, respiration, brainstem reflexes, and pupillary responses despite prolonged resuscitation may indicate irreversible brain injury and poor prognosis.

Post-Resuscitation Care

• Post-resuscitation care aims to stabilize vital functions and treat the underlying cause of cardiorespiratory arrest.
• Patients should be monitored for complications such as hypoxic brain injury and cerebral edema.
• Maintenance of adequate oxygenation, ventilation, and hemodynamic stability is essential.
• Targeted temperature management may be employed in selected patients to reduce cerebral metabolic demand and limit neurological injury.