Respiration Study Guide

Respiratory Mechanics

Respiratory passageway/Chest wall structure & organization

Ventilation  —  Respiratory muscles.

Ventilation  —  pressures; air flow (Flow = ΔP/R)

Measurement & significance of lung volumes: minute volume, Min vol = V_T x f

Work of breathing: Compliance work; Resistance work; Airway resistance work:

Compliance of lung and chest wall

• Compliance, C = ΔV / ΔP.
• Abnormal compliance

Alveolar surface tension  —  tension of fluid film lining alveoli

• Measurement in lung system
• Surfactant and its importance: Laplace, P = 2T/r

Resistance to air flow: Tissue and airway resistance: Poiseuille flow,   Q  =  ΔP  ×  π r⁴ / 8 η L

Dead Space and Uneven Ventilation

• Definitions
• Measurement: Bohr Eqn., V_D = V_T × [(PA_CO2 - PE_CO2)/PA_CO2
• Dead Space and Alveolar Ventilation: V_A = (V_T - V_D) × f

Physical Principles of Gaseous Exchange

Properties of Gases

• Partial pressure
• Gases in Solution
• Diffusion: Fick's law: V_gas = ^dm/_dt = DA(dP × ^S/_dx)

Gas Exchange in the Lung

• Composition of alveolar and expired air
• Diffusion capacity  —  amt of gas crossing alveolar membrane/unit time/mm Hg diff. in press.

Pulmonary circulation vs systemic circulation: comparisons

• Vascular compliance
• Capillary dynamics: Q = kf [(P_c + π_i) - (P_i + π_c)]

Ventilation-Perfusion ratio

Alveolar ventilation equation: PA_CO2 =  _CO2 / _A

Pathological conditions interfering with oxygenation

Carriage of Oxygen

Chemistry of Hemoglobin: complex metallo-protein

• Spectral characteristics

Kinetics of hemoglobin/O₂ interactions: shape of curve; dependence on pH and PCO₂, Temperature & (2,3 DPG)

Carriage of CO₂ by the blood

Forms of CO₂: (CO₂)_d; H₂CO₃; HCO₃^-; carbamino compounds

• Solubility; Hydration reaction:     CO₂ + H₂O  ↔  H₂CO₃  ↔  H⁺ + HCO₃^-

Catalyzed reactions

• carbonic anhydrase:   CO₂ + H₂O  < ^C.A. >  H₂CO₃
• Anion exchange: Cl^-/HCO₃^- shift

Control of Respiration

Location of Respiratory Centers & Control Units

Central or Medullary Chemoreceptors

• Medullary Chemosensitive areas
• Surface H⁺ receptors respond directly to local application of H⁺
• Role of CSF

Peripheral Chemoreceptors: Location and Sensitivity

Interaction between Central & Peripheral Chemoreceptors.

Respiratory Responses to Exercise

Responses to Change in Respiratory Gases

Hypoxia  —  O₂ deficiency at the tissue level

• Hypoxic hypoxia; Anemic hypoxia; Stagnant hypoxia; Histotoxic hypoxia