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Respiratory volumes - alveolar dead space in...

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Respiratory volumes & pulmonary function tests Respiratory volumes: - respiratory volumes measured with spirometer - tidal volume (TV): air volume that moves into & out of the lungs with each breath (~ 500 ml) - inspiratory reserve volume (IRV): air volume that can be forcibly inspired beyond tidal volume (~ 1900-3100 ml) - expiratory reserve volume (ERV): air volume that can be forcibly expired beyond tidal volume (~ 700-1200 ml) - residual volume (RV): air remaining in lungs after forced exhalation (~ 1200 ml) Respiratory capacities: - inspiratory capacity (IC): TV + IRV - functional residual capacity (FRC): RV + ERV - vital capacity (VC): TV + IRV + ERV - total lung capacity (TLC): VC + RV Dead Space: portions of the respiratory passageways where air remains & does not take part in gas exchange in the lungs (~ 30% or 150 ml of 500 ml tidal volume ) - anatomical dead space: in nose, pharynx, larynx, trachea, bronchi, bronchioles
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Unformatted text preview: - alveolar dead space: in alveoli & respiratory zone- total dead space: anatomic + alveolar dead space Pulmonary Function Tests:- minute or total ventilation: total amount of gas that flows into or out of the respiratory tract in 1 minute o during normal quiet breathing, ~ 6 L/min. (500 ml/breath x 12 breaths/min.)- forced vital capacity (FVC): measures amount of gas expelled following deep breath & forceful exhalation o forced expiratory volume (FEV) : determines amount of air expelled during specific intervals or FVC test Alveolar ventilation: AVR = frequency (breaths/min.) x (TV dead space)- measures respiratory efficiency taking dead space into account- normally ~ 4200 ml/min. Nonrespiratory air movements: processes other than breathing that affect air entrance or exit from lungs- examples: laughing, sneezing, coughing- mostly reflex, sometimes voluntary PAGE6...
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