23-Jan-16lung functions1 Lung Function Tests Ventilatory Functions Gas Exchange

23-Jan-16lung functions2 Ventilatory Assessed by determination of –Static lung volumes Elastic resistance Distensibility of lung & thoracic –Dynamic lung volumes Reflection of non elastic resistance

23-Jan-16lung functions3 Determination of Lung Volumes Mouth piece Recoding drum

23-Jan-16lung functions4 Lung Volumes Volume of air in the lungs can be subdivided into 8 components –Tidal volume –Residual volume –Inspiratory reserve vol –Expiratory reserve vol –Inspiratory capacity –Vital capacity –Functional residual capacity –Total lung capacity IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions5 Tidal Volume Vol. Of air inspired or expired during quite breathing –=500 ml –One of the determinant of minute ventilation (pulmonary ventilation) MV = TV * RR IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions6 Inspiratory Reserve Volume IRV Volume of air –That can be taken in by maximal inspiratory effort –Over and above TV –It is about 3000 ml IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions7 Expiratory Reserve Volume ERV Volume of air –That can be expelled by most powerful expiratory effort –After tidal air has been expelled –It is about 1100 ml IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions8 Vital Capacity Vol of air expelled by maximal voluntary expiration following maximal inspiration (IRV + TV + ERV) = 4600 ml Great variation Varies according to –Age, posture –Gender –Body size IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions9 Vital Capacity Related to compliance of the lung –  Compliance leads to a  vital capacity Pulmonary fibrosis Pul. Congestion Obesity Kyphoscoliosis Paralysis of resp muscles IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions10 Vital Capacity Vital capacity is also reduced in –Obstructive lung diseases Asthma –Trapping of air –  RV –Restrictive lung diseases Pleural thickenig IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions11 Functional Residual Capacity Vol. Of gas in the lung at the end of normal expiration (ERV + RV) IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions12 Residual Volume Volume of gas in lungs at end of maximal voluntary effort (1200 ml) Will increase if –Force required to decrease lung vol. Becomes greater Decrease in elasticity - emphysema Stiffer chest wall - pleural thickening, oesteoarthritis IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions13 Residual Volume Voluntary muscular force decreases –Pain, neuromuscular weakness Will increase –Presence of airway obstruction Air trapping IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions14 Inspiratory Capacity Volume of air that can be inspired from the end of expiration –IRV + Vt –It is about IRV Vt ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions15 Total Lung Capacity Vital capacity + residual volume –5800 ml All pulmonary volumes are 20 to 25% less in females IRV TV ERV RV VC FRC IC TLC Inspiration Expiration

23-Jan-16lung functions16 Dynamic Lung Volumes Give information about the non elastic resistance By estimation of the rates at which –Inspiratory & expiratory vital capacity takes place TV Inspiration 1230 Time in seconds

23-Jan-16lung functions17 Forced Expiratory Volume FEV t or Timed vital capacity Subject inspires to TLC –Then exhales as rapidly as possible to RV TV Inspiration 1230 Time in seconds

23-Jan-16lung functions18 Forced Expiratory Volume The spirometer record both –Volume expired over –Preset time interval It is a measurement of the –Rate at which a maximal inspiration can be completely exhaled TV Inspiration 1230 Time in seconds

23-Jan-16lung functions19 Forced Expiratory Volume Measure evaluates –Muscle power –Pulmonary & thoracic compliance –Overall resistance TV Inspiration 1230 Time in seconds

23-Jan-16lung functions20 Forced Expiratory Volume Normal person can exhale –68% of VC at 0.5 sec –77% of VC at 0.75 sec –84% of VC at 1 sec –94% of VC at 2 sec –97% of VC at 3 sec Ratio known as FEV1/FVC % TV Inspiration 1230 Time in seconds FEV1 FVC

23-Jan-16lung functions21 Forced Expiratory Volume In obstructive pulmonary diseases –The rate at which air is exhaled is slower –Total volume exhaled is lower FEV1/FVC =< 80% –Value as low as 42% TV Inspiration 1230 Time in seconds FEV1 FVC FEV1 FVC

23-Jan-16lung functions22 Forced Expiratory Volume In restrictive pulmonary diseases –Total volume(FVC) exhaled is lower –But 90% of FVC Exhaled in 1 sec FEV1/FVC => 80% TV Inspiration 1230 Time in seconds FEV1 FVC FEV1 FVC FEV1

23-Jan-16lung functions23 Peak Flow Rate Maximum rate in liters/ min –At which air can be expired Forces tending to narrow the airways –Peribronchial pressure, pleural –Contraction of bronchial smooth muscles P> Atmos Atmos Forces tending to widen airways Forces tending to narrow airways

23-Jan-16lung functions24 Peak Flow Rate Forces tending to widen the airways –Intra-luminal pressure –Tethering action of connective tissue P> Atmos Atmos Forces tending to widen airways Forces tending to narrow airways

23-Jan-16lung functions25 Blood Gases Normal respiration maintain –PaO 2 = 96 mm Hg, PCO 2 = 40 mm Hg Analysis of blood gases –Can be done Quickly & efficiently Sophisticated machines available Blood PO 2, PCO 2, pH –Can easily be estimated

23-Jan-16lung functions26 Blood Gases Analysis –Indicate the presence of respiratory failure –Provided that CVS, renal system are normal Usually respiratory failure –Defined in terms of  PaO 2 &  PaCO 2