PSL301 — Cardiovascular & Respiratory Study Materials Study Guide

🫀 Cardiovascular Overview

Cardiovascular disease (CVD) refers to a range of disorders of the heart and blood vessels, including coronary heart disease, cerebrovascular disease, peripheral arterial disease, rheumatic heart disease, congenital heart disease, deep vein thrombosis, and pulmonary embolism. CVD is a leading cause of death worldwide and affects both younger and older populations as lifestyle risk factors rise.

⚠️ Risk Factors (modifiable vs non-modifiable)

Non-modifiable risk factors include age, sex, and family history. Modifiable risk factors include smoking, obesity, sedentary lifestyle, untreated hypertension, untreated high cholesterol, diabetes mellitus, and stress. Elevated blood lipids—especially high LDL-C and low HDL-C—contribute strongly to atherosclerosis.

🧱 Atherosclerosis & Plaque Formation

Atherosclerosis is the build-up of fatty material (mainly cholesterol) beneath the endothelial lining of arteries, forming plaques. Plaque evolution typically progresses through stages: a fatty streak (LDL deposition and macrophage infiltration), a stable fibrous plaque (lipid core with fibrous cap and calcification), and a vulnerable plaque (heterogeneous, prone to rupture). When plaques rupture they can trigger thrombus formation that may occlude blood flow or embolize.

💔 Ischemic Heart Disease & Myocardial Infarction

Ischemic heart disease arises when myocardial oxygen supply does not meet demand, producing ischemia. Clinical manifestations range from asymptomatic to stable angina, myocardial infarction (MI), arrhythmia, heart failure, and sudden death. MI diagnosis relies on typical chest pain, elevation of myocardial enzymes (e.g., CK-MB, troponin), and ECG changes such as ST elevation.

🩺 Medical & Surgical Treatments

Acute MI management includes rest, oxygen, analgesia, aspirin, thrombolysis (e.g., t-PA converting plasminogen to plasmin), and primary angioplasty. Long-term therapies include beta-blockers, ACE inhibitors, and lifestyle modification. Revascularization options include percutaneous coronary intervention (angioplasty with balloon ± stent) and coronary artery bypass grafting (CABG). Advanced heart failure may require LV assist devices or heart transplant.

📈 Blood Pressure: Hypertension & Hypotension

Hypertension is sustained elevated arterial pressure and is a major cause of heart failure, vascular disease, renal failure, and stroke. Most cases are essential hypertension (unknown cause ~90%); others are secondary to identifiable disease processes. Baroreceptor adaptation can shift homeostatic setpoints, making sustained hypertension harder to correct. Hypotension includes orthostatic, chronic (nutritional or endocrine causes), and acute (e.g., shock) forms.

🩻 Clinical Consequences & Physiology Notes

Chronic high blood pressure damages cerebral vessels (stroke risk), increases cardiac workload (hypertrophy), and promotes endothelial damage and atherogenesis. Management aims to reduce peripheral resistance, limit remodeling, and protect organ perfusion.

🫁 Respiratory System Functions

The respiratory system performs gas exchange between air and blood (external respiration), regulates body pH, defends against inhaled pathogens and particles, and enables vocalization. Efficient function depends on integrated airway structure, alveolar architecture, and circulatory delivery.

🏗️ Anatomy: Conducting & Respiratory Zones

The airway begins at the nasal and oral cavities, passes the pharynx, larynx, and trachea, and branches into primary bronchi then repeatedly until terminal bronchioles and alveolar sacs. The conducting zone conditions, warms, humidifies, and filters air; the respiratory zone (alveoli) is the site of gas exchange. Cartilage supports larger airways; smaller bronchioles rely on smooth muscle.

🧹 Airway Defense & Mucociliary Escalator

The mucociliary escalator traps particles in mucus produced by goblet cells and moves them out by coordinated ciliary beating. Alveolar macrophages and secreted IgA help neutralize pathogens. Smoking increases mucus production but impairs ciliary clearance, reducing defense.

🌬️ Alveoli & Gas Exchange

Humans have ~300 million alveoli that provide large cross-sectional area and minimal diffusion distance. Type I alveolar cells form the thin barrier for diffusion; Type II cells secrete pulmonary surfactant, which reduces surface tension and prevents alveolar collapse.

💓 Pulmonary Circulation & Pressures

Pulmonary circulation carries the entire cardiac output at low pressure (approximate normal values are low compared to systemic pressure) to allow gas exchange without disrupting alveolar-capillary matching. Blood flows from the right ventricle → pulmonary trunk → pulmonary arteries → arterioles → capillaries → venules → pulmonary veins → left atrium.

🫙 Mechanics of Breathing

Breathing follows Boyle’s Law: changes in thoracic volume create pressure gradients that move air. The diaphragm is the principal inspiratory muscle (innervated by C3–C5 via the phrenic nerve). At rest, expiration is passive due to elastic recoil; active expiration recruits abdominal and internal intercostal muscles. Intrapleural pressure is subatmospheric and the pleural fluid couples lungs to chest wall.

🚑 Pneumothorax First Aid

A pneumothorax may arise when the pleural space is breached. First-aid includes applying a wet dressing as a one-way valve and providing positive-pressure ventilation at the mouth if trained, to prevent progressive lung collapse until definitive care.