Emergency & First Aid: Heimlich Maneuver for Choking

Introduction

Definition and Overview

The Heimlich maneuver, also known as abdominal thrusts, is a first‑aid technique designed to relieve upper airway obstruction caused by a foreign body. It involves a series of rapid compressions of the diaphragm by applying intra‑abdominal pressure, thereby generating a sudden increase in intrathoracic pressure that expels the obstructing material. The maneuver is universally taught in emergency medical curricula and is endorsed by major professional societies for its potential to restore airway patency in adults and, with modifications, in children and pregnant patients.

Historical Background

The origin of the technique is commonly attributed to Dr. Henry Heimlich, who introduced the method in the 1970s after observing the efficacy of abdominal thrusts in patients who had ingested small objects. While anecdotal accounts predate Heimlich, the formalization and widespread dissemination of the maneuver in the 1980s marked a turning point in the standardization of choking first aid. Subsequent revisions by organizations such as the American Heart Association (AHA) and the American Red Cross have refined the algorithm, incorporating evidence‑based adjustments for different patient populations.

Importance in Pharmacology and Medicine

Although the Heimlich maneuver is primarily a mechanical intervention, its relevance extends to pharmacological practice in several ways. First, knowledge of airway management informs the selection of sedatives and neuromuscular blockers in procedural sedation, where inadvertent aspiration or obstruction can occur. Second, certain drug classes (e.g., anticholinergics, antiepileptics) predispose patients to reduced salivary flow or impaired gag reflex, thereby increasing choking risk. Finally, emergency pharmacotherapy following airway obstruction—such as the administration of atropine in severe bradycardia or epinephrine in anaphylaxis—requires a clear airway for effective delivery; thus, quick resolution via the Heimlich maneuver is critical for successful drug action.

Learning Objectives

• Describe the anatomical and physiological basis of airway obstruction and the mechanical principles underlying the Heimlich maneuver.
• Compare the standard protocol for adults, children, and pregnant patients, noting key modifications.
• Identify clinical scenarios in which the Heimlich maneuver is indicated and outline steps for safe implementation.
• Recognize pharmacological factors that may influence choking risk and discuss strategies to mitigate such risks.
• Apply the Heimlich maneuver in simulated case studies, demonstrating effective decision‑making and technique execution.

Fundamental Principles

Core Concepts and Definitions

Airway obstruction is classified as partial or complete based on the degree to which the airway lumen is compromised. A partial obstruction allows limited airflow, often manifesting as inspiratory stridor or coughing, whereas a complete obstruction results in cessation of airflow, leading to apnea and hypoxia. The Heimlich maneuver targets complete obstructions by rapidly increasing intra‑abdominal and intrathoracic pressures to dislodge the foreign body.

Theoretical Foundations

The maneuver exploits the rapid generation of negative intrathoracic pressure during a forced exhalation. By compressing the diaphragm and abdominal cavity, the pressure differential across the glottis is amplified, creating a force capable of propelling the obstruction out of the larynx. The underlying physics can be approximated by the Bernoulli principle, where pressure (P) is related to the velocity (v) of the airflow: P = ½ ρ v², with ρ representing air density. While the true dynamics involve complex fluid‑structure interactions, the simplified model illustrates the necessity of a high velocity exhalation generated by the sudden intra‑abdominal pressure spike.

Key Terminology

• Foreign body aspiration (FBA) – Inhalation of material that obstructs the airway.
• Abdominal thrust – Forceful compression of the diaphragm and abdominal wall.
• Intra‑abdominal pressure (IAP) – Pressure within the abdominal cavity.
• Intrathoracic pressure (ITP) – Pressure within the thoracic cavity.
• Glottis – The opening between the vocal cords.
• Choking episode – Clinical event characterized by sudden airway obstruction.

Detailed Explanation

Mechanisms and Processes

During a Heimlich maneuver, the rescuer positions the patient in a semi‑upright stance, places a firm hand just above the navel, and delivers a series of rapid, upward thrusts. Each thrust elevates the diaphragm, compressing the abdominal contents and forcing a sudden expansion of the thoracic cavity. The resultant pressure differential (ΔP = IAP – ITP) is transmitted to the airway, generating a high‑velocity jet of air that can expel the obstruction. The process can be understood as a series of impulse events: the force applied (F) over a small displacement (Δx) imparts kinetic energy (½ mv²) to the respiratory system, where m is the mass of air displaced.

Mathematical Relationships

Although precise modeling of airway dynamics during the Heimlich maneuver is complex, a simplified relationship can be expressed as:

C(t) = C₀ × e⁻ᵏᵗ

where C(t) represents the concentration of air pressure at time t, C₀ is the initial pressure, and k is the rate constant reflecting rapid pressure decay after each thrust. A more direct representation of pressure change is ΔP ≈ ρ × v² / 2, reinforcing the importance of generating high airflow velocity (v) through rapid thrusts. The required thrust force can be approximated using Newton’s second law: F = m × a, with m being the mass of the abdominal contents and a the acceleration imparted by the rescuer.

Factors Affecting the Process

Several patient‑specific factors influence the success of the Heimlich maneuver:

• Body habitus – Obesity may reduce the effectiveness of abdominal thrusts due to increased tissue thickness.
• Obstruction size and location – Larger or posteriorly positioned obstructions may resist expulsion.
• Age and anatomical differences – Children possess smaller airways and a different diaphragmatic orientation, necessitating modified thrusts.
• Pregnancy – The enlarged uterus increases intra‑abdominal pressure and alters diaphragmatic mechanics; the technique requires lateral positioning and a modified thrust depth.
• Underlying medical conditions – Conditions such as chronic obstructive pulmonary disease (COPD) or kyphoscoliosis can alter thoracic compliance, affecting pressure generation.

Clinical Significance

Relevance to Drug Therapy

In emergency pharmacology, the Heimlich maneuver is pivotal for ensuring effective drug delivery. For instance, in a patient experiencing severe hypoxia secondary to choking, intravenous administration of atropine to counter bradycardia or epinephrine to treat anaphylaxis requires a patent airway; otherwise, systemic absorption is compromised. Additionally, patients receiving sedatives or neuromuscular blocking agents for procedural sedation are at heightened risk of aspiration; rapid airway clearance via the Heimlich maneuver can prevent aspiration pneumonitis and subsequent need for ventilatory support.

Practical Applications

Standard guidelines recommend the following steps for adult patients:

1. Assess responsiveness and breathing.
2. Call emergency services.
3. Position the patient upright and place the rescuer’s fist just above the navel.
4. Deliver 5 quick, upward abdominal thrusts.
5. Alternate between 5 abdominal thrusts and 5 back blows if the obstruction is not expelled.
6. Continue until the patient regains airway patency or until professional help arrives.

In children, the technique involves a combination of abdominal thrusts and back blows, with the rescuer standing behind the child. For pregnant patients, the rescuer places the patient on the left lateral decubitus position and then applies abdominal thrusts, reducing aortocaval compression.

Clinical Examples

Case 1: A 28‑year‑old woman collapses while eating a hotdog. She is unresponsive and apneic. Emergency responders perform the Heimlich maneuver and restore breathing within 12 seconds. Rapid administration of atropine for bradycardia follows, and the patient stabilizes.

Case 2: A 5‑year‑old child ingests a small toy. The child coughs and then becomes unable to breathe. Back blows and abdominal thrusts are performed; the toy is expelled after 7 thrusts. The child is then transferred to a pediatric emergency department for observation.

Clinical Applications/Examples

Case Scenarios and Problem‑Solving Approaches

Scenario A: An elderly male with COPD presents with sudden choking while eating. The rescuer notes a high respiratory rate but no audible stridor. The Heimlich maneuver is initiated, and the obstruction is expelled after 10 thrusts. Post‑intervention, the patient receives nebulized bronchodilator therapy to address underlying COPD exacerbation.

Scenario B: A 32‑year‑old pregnant woman at 32 weeks gestation experiences choking during a meal. The rescuer positions her in a left lateral decubitus posture to avoid aortocaval compression, then performs abdominal thrusts. The obstruction is expelled, and the patient is monitored for fetal heart rate changes during the procedure.

Application to Specific Drug Classes

• Anticholinergics – Patients on drugs such as oxybutynin or scopolamine may have diminished gag reflex and xerostomia, increasing choking risk. Clinicians should educate patients on safe eating practices and consider dose adjustments.
• Calcium channel blockers – These medications can reduce smooth muscle tone, potentially affecting esophageal clearance; monitoring for dysphagia is advised.
• Opioids – Respiratory depression and impaired airway reflexes heighten choking risk; rescue protocols should include immediate airway management and reversal agents (e.g., naloxone) if needed.

Problem‑Solving Approach

When encountering a choking patient, a systematic approach is recommended:

1. Verify patient responsiveness and breathing.
2. Assess for signs of complete obstruction (e.g., inability to speak, coughing, cyanosis).
3. If obstruction is complete, initiate the Heimlich maneuver appropriate for the patient’s age and physiological status.
4. Simultaneously call for emergency assistance.
5. Monitor vital signs and airway status; if the obstruction persists, consider alternative techniques (e.g., back blows, suction, or emergency airway intervention).
6. Once airway patency is restored, evaluate for secondary complications (aspiration, hypoxia) and administer appropriate pharmacologic therapy.

Summary/Key Points

• The Heimlich maneuver is a mechanically driven intervention that generates intra‑abdominal and intrathoracic pressure to expel foreign bodies from the upper airway.
• Success depends on patient factors (age, body habitus, pregnancy) and precise execution of thrusts.
• In pharmacologic practice, rapid airway clearance is essential for effective drug delivery in emergencies such as bradycardia, anaphylaxis, or sedation‑related aspiration.
• Key safety considerations include positioning (upright for adults, lateral for pregnant patients), monitoring for incomplete obstruction, and readiness to transition to advanced airway management if necessary.
• Continuous education and simulation training are recommended to maintain proficiency, given the rarity but high‑stakes nature of choking emergencies.

By integrating knowledge of airway physiology, mechanical principles, and pharmacologic implications, medical and pharmacy students can effectively contribute to the management of choking incidents, ensuring timely restoration of airway patency and optimal patient outcomes.

References

1. Walls RM, Hockberger RS, Gausche-Hill M. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia: Elsevier; 2022.
2. Bennett PN, Brown MJ, Sharma P. Clinical Pharmacology. 12th ed. Edinburgh: Elsevier; 2019.
3. Waller DG, Sampson AP. Medical Pharmacology and Therapeutics. 6th ed. Edinburgh: Elsevier; 2022.
4. Feather A, Randall D, Waterhouse M. Kumar and Clark's Clinical Medicine. 10th ed. London: Elsevier; 2020.
5. Ralston SH, Penman ID, Strachan MWJ, Hobson RP. Davidson's Principles and Practice of Medicine. 24th ed. Edinburgh: Elsevier; 2022.
6. Loscalzo J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL. Harrison's Principles of Internal Medicine. 21st ed. New York: McGraw-Hill Education; 2022.
7. Trevor AJ, Katzung BG, Kruidering-Hall M. Katzung & Trevor's Pharmacology: Examination & Board Review. 13th ed. New York: McGraw-Hill Education; 2022.
8. Rang HP, Ritter JM, Flower RJ, Henderson G. Rang & Dale's Pharmacology. 9th ed. Edinburgh: Elsevier; 2020.