Obstructive vs Restrictive
This is the hallmark spirometry finding in obstructive lung disease.
decreased FEV1/FVC ratio (<0.7)
This lung zone is considered dead space due to lack of perfusion.
Zone 1 (PA > Pa > Pv)
This region of the brain sets the basic respiratory rhythm.
dorsal respiratory group in the medulla
This type of sleep apnea is caused by upper airway collapse.
OSA
Shock is defined as this physiologic state.
inadequate tissue perfusion and oxygen delivery
This pathophysiologic mechanism causes airway collapse in COPD.
loss of elastic recoil and decreased bronchiolar support
This physiologic change occurs in chronic hypoxemia to improve oxygen delivery.
increased RBC production (polycythemia)
These receptors are most sensitive to CO₂ changes.
central chemoreceptors
This is the key physiologic mechanism causing airway collapse during sleep.
decreased pharyngeal muscle tone
This metabolic change occurs when tissues switch to anaerobic metabolism.
Lactic acidosis
This structural change explains increased mucus production in chronic bronchitis.
goblet cell hyperplasia and submucosal gland hypertrophy
This mechanism explains why V/Q mismatch leads to hypoxemia despite normal ventilation in some lung regions.
uneven distribution of ventilation and perfusion causing inefficient gas exchange
This is the primary stimulus that increases ventilation via central chemoreceptors.
increased hydrogen ion concentration in CSF (from CO₂)
This pressure dynamic contributes to airway collapse during inspiration.
negative intraluminal pressure pulling airway inward
This type of shock is caused by decreased preload and blood volume.
Hypovolemic Shock
This is why patients with emphysema have increased lung compliance.
destruction of alveolar elastin fibers
This V/Q condition is characterized by a ratio approaching infinity, where ventilation is present but perfusion is absent.
Dead Space
These receptors are responsible for detecting hypoxemia.
peripheral chemoreceptors (carotid/aortic bodies)
This major cardiovascular consequence results from chronic OSA.
pulmonary hypertension (or systemic HTN, RV failure)
This type of shock is characterized by decreased SVR and relative hypovolemia.
distributive shock
This is the key physiologic difference in restrictive lung disease compared to obstructive disease.
decreased lung compliance with normal or increased FEV1/FVC ratio
This is why increasing FiO₂ has minimal effect on improving oxygenation in true shunt physiology.
Blood bypassing ventilated alveoli, preventing oxygen from reaching circulation
This explains why chronic CO₂ retainers rely more on hypoxic drive.
desensitization of central chemoreceptors to CO₂
This differentiates central sleep apnea from OSA.
lack of respiratory drive instead of airway obstruction?
This distinguishes early septic shock from hypovolemic shock in terms of cardiac output.
increased (or normal) cardiac output in early septic shock vs decreased in hypovolemic shock