Lung Volumes 17-Apr-19 Lung Volumes

Lung Volumes Tidal volume 500 ml Total ventilation 7500 ml/min Anatomical dead space 150 ml Frequency = 15 per min Alveolar gas 3000 ml Alveolar ventilation 5250 ml/min Pulmonary blood flow 5000 ml/min Pulmonary capillary blood 70 ml 17-Apr-19 Lung Volumes

Determination of Lung Volumes Recoding drum Mouth piece Water filled spirometer 17-Apr-19 Lung Volumes

Lung Volumes Inspiration Volume of air in the lungs can be subdivided into 8 components Most important Tidal volume Vital capacity Functional residual capacity Residual volume Total lung capacity 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Tidal Volume Volume of air It is about 500 ml Inspiration Volume of air Inspired or expired during breathing It is about 500 ml One of the determinants of minute ventilation Pulmonary ventilation MV = TV * RR 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

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 Inspiration 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Expiratory Reserve Volume ERV Inspiration Volume of air That can be expelled by most powerful expiratory effort After tidal air has been expelled It is about 1100 ml 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Residual Volume Inspiration 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 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Residual Volume Will increase Voluntary muscular force decreases Inspiration Voluntary muscular force decreases Pain, neuromuscular weakness Will increase Presence of airway obstruction Air trapping 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Vital Capacity Vol of air expelled by maximal voluntary expiration following maximal inspiration (IRV + Vt + ERV) = 4600 ml Great variation Depends on height & age Inspiration 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Vital Capacity Reduction in vital capacity Decrease lung gas volume Inspiration Reduction in vital capacity Decrease lung gas volume Space occupying lesion Decreased ability to expire or inspire maximally decrease muscular force, pain, neurological diseases 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Vital Capacity Increase resistance to chest cage expansion Inspiration Increase resistance to chest cage expansion Increase resistance to expansion of lung Pleural thickening, asthma 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Inspiratory Capacity Volume of air that can be inspired from the end of expiration IRV + Vt It is about 3500 Inspiration 6 IRV VC IC TLC 1.7 Vt 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Functional Residual Capacity Volume of gas in the lungs At the end of normal expiration (ERV + RV) Position at which tendency of Lung to collapse is equal to Elastic and muscular force of chest cavity causing it to expand Affected by Body position, anxiety, pregnancy Inspiration 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Functional Residual Capacity FRC is the lung volume Gas exchange takes place With each tidal breath Fresh gas mixes with alveolar gas Small fluctuation of Alveolar & arterial gas tensions Inspiration 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Functional Residual Capacity FRC acts as a buffer Maintain relative constant Alveolar & arterial gas tension Prevent rapid change in alveolar gas When there is change in ventilation or inspired gas ↑ Lung volume during quiet breathing ↓Work of breathing Inspiration 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Total Lung Capacity Vital capacity + Residual volume Inspiration Vital capacity + Residual volume 5800 ml All pulmonary volumes are 20 to 25% less in females 6 IRV VC IC TLC 1.7 TV 1.2 ERV FRC 1.1 RV Expiration 17-Apr-19 Lung Volumes

Forced Expiratory Volume FEVt or Timed vital capacity Subject inspires to TLC Then exhales as rapidly as possible to RV Inspiration 6 1.7 TV 1.2 1.1 1 2 3 Time in seconds 17-Apr-19 Lung Volumes

Forced Expiratory Volume Inspiration 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 6 1.7 TV 1.2 1.1 1 2 3 Time in seconds 17-Apr-19 Lung Volumes

Forced Expiratory Volume Inspiration 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 % 6 FEV1 FVC 1.7 TV 1.2 1.1 1 2 3 Time in seconds 17-Apr-19 Lung Volumes

Forced Expiratory Volume Inspiration Measure evaluates Muscle power Pulmonary, thoracic compliance Overall resistance 6 1.7 TV 1.2 1.1 1 2 3 Time in seconds 17-Apr-19 Lung Volumes