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AACNCriticalCareNursingExamQuestionsand Answers. Cellular respiration cannot be directly measured but is estimated by the amount of - > CO2 produced (V̇ CO2) and the amount of O2 consumed (V̇ O2). V̇ CO2 - > CO2 produced in celluar respiration V̇ O2 - > and the amount of O2 consumed in cellular respiration external respiration - > The Exchange of O2 and CO2 at the alveolar-capillary level. It is the ratio of the CO2 produced to the O2 taken up per minute. V̇ CO2/min : V̇ O2/min Proper functioning of the respiratory circuit requires efficient interaction of the - > 1. respiratory 2. circulatory 3. neuromuscular system
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Cellular respiration cannot be directly measured but is estimated by the amount of - > CO2 produced (V̇CO2) and the amount of O2 consumed (V̇O2). V̇CO2 - > CO2 produced in celluar respiration V̇O2 - > and the amount of O2 consumed in cellular respiration external respiration - > The Exchange of O2 and CO2 at the alveolar-capillary level. It is the ratio of the CO2 produced to the O2 taken up per minute. V̇CO2/min : V̇O2/min Proper functioning of the respiratory circuit requires efficient interaction of the - > 1. respiratory
Lobes are divided into bronchopulmonary segments - > 10 - RIGHT 9 - LEFT Bronchopulmonary segments are subdivided into - > secondary lobules Secondary Lobules - > Independent respiratory units of lung each bronchopulmonary segment is supplied independently by: a (tertiary) segmental bronchus a tertiary branch of pulmonary artery - carry low oxygen ("venous") blood to lungs for oxygenation a branch of bronchial artery What does a a tertiary branch of pulmonary artery do for secondary lobules? - > - carries low oxygen ("venous") blood to lungs for oxygenation Smallest gross anatomic units of lung tissue; contain the primary functional units of the lung - > Lobule: Lobule (the smallest gross anatomic units of lung tissue) consists of - > 1. terminal bronchioles
anatomic dead space. - > The entire area from the nose to the terminal bronchioles where gas flows, but is not exchanged, is called Approx 150 mL but varies with patient size and position. Nose - > a) Serves as a passageway for air movement into the lungs b) Preconditions air by the mucosal cells and turbinate bones
Thickness of the respiratory membrane is about 0.6 μm. The large surface area distributes a large quantity of perfused blood into a very thin film to ensure near equalization of O2 and CO2. Alveolar cells - Type I: - > 1) Squamous epithelium, adapted for gas exchange, sensitive to injury by inhaled agents, structured to prevent fluid transudation into the alveoli Alveolar cells - Type II: - > Large secretory, highly active metabolically; origin of surfactant synthesis and type I cell genesis Alveolar macrophages: - > Phagocytize foreign materials A Phospholipid monolayer at the alveolar air-liquid interface; able to vary surface tension with alveolar volume - > Pulmonary surfactant Pulmonary Surfactant Enables surface tension to decrease as - > alveolar volume decreases during expiration, which prevents alveolar collapse Decreases the work of breathing, permits the alveoli to remain inflated at low distending pressures, reduces net forces causing tissue fluid accumulation - > Pulmonary Surfactant Reduction in surfactant production makes - > lung expansion more difficult; the greater the surface tension, the greater the pressure needed to overcome it Detoxifies inhaled gases and traps inhaled and deposited particles - > Surfactant Alveolar-capillary membrane - > 1. alveolar epithelium
Alveolar ventilation (V̇A): That part of total ventilation taking part in gas exchange and, therefore, the only part useful to the body - > (a) Alveolar ventilation is one component of minute ventilation Minute ventilation (V̇E): - > Amount of air exhaled in 1 minute. Equal to exhaled tidal volume (VT) multiplied by respiratory rate (RR or f). - > Minute Ventilation (VE) Normal resting minute ventilation in an adult is about - > 6 L/min: VT - > Exhaled Tidal Volume VT * RR = VE - > Exhaled Tidal Vol (VT) * Resp Rate (RR) = Minute Ventilation (VE) Tidal volume is easily measured at the bedside by hand-held devices or a mechanical ventilator. - > spirometers (measure tidal vol) Exhaled minute ventilation is a routinely measured parameter for patients on ventilators. Minute ventilation is composed of both - > 1. alveolar ventilation (V̇A)
Ratio of dead space to tidal volume (VD/VT) measured to determine - > how much of each breath does not contribute to gas exchange. Normal values for spontaneously breathing patients range from - > 20% to 40% of VT. Alveolar ventilation is not measured directly; it is inversely related to arterial CO pressure (PaCO2) in a steady state by the following formula: - > VA = VCO2 * 0.863 / PaCO where 0.863 = correction factor for differences in measurement units and conversion to standard temperature [0° C] and pressure [760 torr], dry (STPD). (c) Since V̇CO2 remains the same in a steady state, measurement of the patient's PaCO2 reveals the status of the alveolar ventilation. To assess ventilation, PaCO2 must be measured. - > PaCO2 is the only adequate indicator of effective matching of alveolar ventilation to metabolic demand. If PaCO2 is low, alveolar ventilation is high; - > hyperventilation is present If PaCO2 is within normal limits, - > alveolar ventilation is adequate If PaCO2 is high, alveolar ventilation is low and - > hypoventilation is present often leads to ventilator dependency. - > Injury at or above C3 to C5 level