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Ventilation - The mechanical movement of air into and out of the airways in a cycle fashion - Alveolar ventilation-ventilation of alveoli that are being perfused and adequate gas exchange is taking place - Dead Space Ventilation-volume of gas that is ventilated, but not physiologically effective (Anotomic, Alveolar, and Physiologic) Anatomic Dead Space - The volume of air contained in the pulmonary conducting system that is not involved in gas exchange - Rule of Thumb-1ml/lb body weight - Abbreviated as VDanat Alveolar Dead Space - The ventilation of an alveoli that is not being perfused (the passing of blood or fluid through a vascular bed) via the pulmonary capillary bed therefore has no gas exchange - If significant it indicates a pulmonary pathological disease - Abbreviated VDalv Physiologic Dead Space - The portion of inhaled air that does not take part in pulmonary gas exchange - Combination of anatomic and alveolar dead space - Abbreviated VDphy Clinical Terms Associated with Ventilation - Normal Ventilation-the amount of minute ventilation (also referred to as respiratory rate or tidal volume) to provide adequate alveolar ventilation and fulfill the body's gas exchange needs - Hypoventilation-the state of impaired breathing where the alveoli are inadequately ventilated to fulfill the body's gas exchange needs - Hyperventilation-an over-aeration of the alveoli beyond gas exchange needs (may be voluntary or involuntary) Volumes and Capacities - Vital Capacity (VC)-the amount of air that is maximally exhaled after a maximal inhalation - Residual Volume (RV)-the amount of air remaining in the lungs at the end of a maximal exhalation - Total Lung Capacity (TLC)-the amount of air remaining in the lungs after a maximal inhalation - Functional Residual Capacity (FRC)-the amount of air remaining in the lungs at the end of a normal resting exhalation Respiration - Refers to the molecular gas exchange of oxygen and carbon dioxide - External Respiration-exchange of gases between the alveoli and the pulmonary capillaries - Internal Respiration-the exchange of gases between systemic capillaries and tissue cells Pulmonary Blood Volume - The volume of blood between the beginning of the pulmonary artery and the end of the pulmonary veins About 900 to 1000ml (healthy adult) - 30% (p) arteries - 10% (p) capillaries - 60% (p) veins Pulmonary Capillary Blood Volume - The volume of blood in the capillary bed at any given moment - Contains about 100ml at any given time (healthy adult) - At rest, complete oxidation of the RBC takes 0.75 seconds - During exercise oxidation of the RBC takes 0.35 seconds - About 95% of the diffusion of O2 takes place before the blood has passed halfway along the pulmonary capillaries Pulmonary Blood Flow - 100ml/sec Effected by gravity - Supine or Prone-close to uniform blood flow - Erect Position-non uniform blood flow Pulmonary Vessels - In general are shorter, thinner, and more distensible and contain less smooth muscle than systemic blood vessels - Hold a larger volume in relation to their systemic counterparts, due to the smaller amount of muscle tissue Pulmonary Artery Pressures - Systolic-25mmHg - Diastolic-8mmHg - Reflect right ventricular systolic pressures - Hypoxia is a potent constrictor