Nose/nasal cavity → pharynx → larynx → trachea → main bronchi → smaller bronchi → bronchioles → alveolar ducts/sacs → alveoli. Conducting passages move/condition air; respiratory zones participate in gas exchange.
During quiet inspiration the diaphragm contracts and descends, increasing thoracic volume and lowering intrapulmonary pressure so air moves inward. Quiet expiration is largely passive elastic recoil. Forced breathing recruits additional muscles.
Oxygen and carbon dioxide diffuse down partial-pressure gradients across the thin respiratory membrane. Pulmonary ventilation brings air to alveoli; perfusion brings blood to pulmonary capillaries. Efficient exchange requires both.
Most oxygen is transported bound to hemoglobin. Carbon dioxide is transported in several forms, with bicarbonate being the largest fraction. Breathing is regulated by brainstem centers and chemoreceptor feedback, especially responses related to CO2/pH.
Visceral pleura covers lungs; parietal pleura lines thoracic cavity. The thin fluid-filled pleural space reduces friction and contributes to mechanical coupling during breathing.
Position clients so they can breathe comfortably. Acute severe dyspnea is not something to treat with deeper chest massage. Contagious respiratory illness may require postponement. COPD/asthma clients may need pacing, positioning and symptom-aware modifications.