First aid knowledge can be lifesaving in emergencies. For an unresponsive adult requiring CPR, the rescuer should call emergency services, place the person on a firm surface, position hands on the center of the chest, and perform compressions at least 5 cm (2 inches) deep at 100–120 per minute, giving two rescue breaths after every 30 compressions if trained. For a choking person who cannot cough or speak, the rescuer should perform abdominal thrusts (the Heimlich maneuver) by standing behind the person, placing a fist just above the navel, grasping it with the other hand, and applying quick upward thrusts; for infants, back blows and chest thrusts replace abdominal thrusts. Severe bleeding is controlled by applying firm direct pressure with a clean cloth, layering more material without removing soaked-through layers, elevating the injured limb above the heart when possible, and using a tourniquet only as a last resort for life-threatening limb bleeding. For burns, cool water should run over the area for at least 10–20 minutes; ice, butter, and toothpaste should be avoided. Anaphylaxis, a severe allergic reaction with throat swelling and blood pressure drop, requires immediate epinephrine (EpiPen) injection into the outer thigh and a call to emergency services. For suspected fractures, the injured area should be immobilized without attempting realignment, ice applied to reduce swelling, and immediate medical attention sought. The recovery position, with the person on their side, top leg bent for stability, and head tilted back, keeps the airway clear in unconscious but breathing individuals.
Medical ethics guides clinical decisions through four core principles: autonomy (respecting the patient's right to make informed decisions), beneficence (acting in the patient's best interest), non-maleficence ("first, do no harm"), and justice (fair distribution of healthcare resources). Informed consent requires that patients understand the purpose, benefits, risks, and alternatives of a procedure before agreeing. Patient confidentiality, protected by laws such as HIPAA, restricts sharing of health information without consent. Advance directives (living wills and healthcare power of attorney) document patient wishes when they cannot make decisions. A do-not-resuscitate (DNR) order specifies that CPR should not be attempted if the heart or breathing stops. Palliative care focuses on relieving symptoms and improving quality of life in serious illness and can be provided alongside curative treatment, while hospice care provides end-of-life comfort for patients with a prognosis of six months or less who forgo curative therapy. Brain death, defined as irreversible cessation of all brain function including the brainstem, is the legal definition of death in most jurisdictions.
Public health and epidemiology examine disease patterns in populations. Epidemiology uses incidence (new cases over time) and prevalence (total existing cases) to track disease burden, while randomized controlled trials (RCTs) remain the gold standard for evaluating treatments through random assignment and double-blinding. Evidence-based medicine integrates the best research evidence with clinical expertise and patient values, with systematic reviews and meta-analyses providing the highest level of evidence. Health outcomes are strongly influenced by social determinants of health, including income, education, employment, housing, food security, and access to care, accounting for 30–55% of health outcomes. The World Health Organization coordinates international public health efforts, including pandemic response. Quarantine separates exposed individuals to observe for symptoms, while isolation separates those who are already sick. Vaccination schedules provide protection at optimal ages, and childhood milestones such as APGAR scores (assessed at 1 and 5 minutes after birth) evaluate newborn health. Vaccine hesitancy remains a top global health threat, addressed through respectful conversation, evidence sharing, and trust-building. Burnout among healthcare workers, characterized by emotional exhaustion and depersonalization, affects roughly half of physicians and is addressed through systemic workplace changes and peer support.