Respiratory Physiology.pdf

3/15/23 Respiratory Physiology Lab #7 1 Volume and Capacity Spirometer measures respiratory volume • Can be used to assess respiratory health • Standard values are available (e.g., for people of different ages) • Four volumes measured by spirometry • Tidal volume: amount of air inhaled or exhale...

3/15/23 Respiratory Physiology Lab #7 1 Volume and Capacity Spirometer measures respiratory volume • Can be used to assess respiratory health • Standard values are available (e.g., for people of different ages) • Four volumes measured by spirometry • Tidal volume: amount of air inhaled or exhaled per breath during quiet breathing • Inspiratory reserve volume (IRV): amount of air that can be forcibly inhaled beyond the tidal volume • Measure of compliance • Expiratory reserve volume (ERV): amount that can be forcibly exhaled beyond tidal volume • Measure of elasticity • Residual volume: amount of air left in the lungs after the most forceful expiration 2 1 3/15/23 Volume and Capacity Four capacities calculated from respiratory volumes • Inspiratory capacity (IC) • Tidal volume + inspiratory reserve volume • Functional residual capacity (FRC) • Expiratory reserve volume + residual volume • Volume left in the lungs after a quiet expiration • Vital capacity • Tidal volume + inspiratory and expiratory reserve volumes • Total amount of air a person can exchange through forced breathing • Sometimes referred to as the Forced Vital Capacity (FVC) • Total lung capacity (TLC) • Sum of all volumes, including residual volume • Maximum volume of air that the lungs can hold 3 Pulmonary Ventilation (VE) Pulmonary ventilation • Process of moving air into and out of the lungs • Amount of air moved between atmosphere and alveoli in 1 minute Tidal volume = amount of air per breath Respiration rate = number of breaths per minute Tidal volume × Respiration rate = Pulmonary ventilation 500 mL × 12 breaths/min = 6000 mL/minute (typical amount) 4 2 3/15/23 Respiratory Volumes and Capacities Spirogram Figure 23.24 5 Generating Sample Spirogram • Log into computer (using bb login and pw) • Power on black box leads go into (green light is on) • Open program (BMS applications on desktop -> lab files -> BMS 251 -> Spirogram -> teaching -> English) • Hit “record” • Autoscale to make it look clear: 6 3 3/15/23 Tidal Volume 7 Respiratory Rate 8 4 3/15/23 Pulmonary Ventilation (VE) Pulmonary Ventilation (VE) in mL/min or L/min = TV (in mL/breath) x RR (breaths/minute); Convert to L/min if asked. (Use TV from last slide 5: 782 mL) 30 seconds 9 Inspiratory Reserve Volume 10 5 3/15/23 Expiratory Reserve Volume 11 Vital Capacity Sometimes referred to as the Forced Vital Capacity (FVC) 12 6 3/15/23 Forced Expiratory Volume (FEV) FEV is the percentage of vital capacity that can be expelled in specific period of time 13 Forced Expiratory Volume in 1 second (FEV1) Airway resistance ratio (FEV1.0/FVC ratio) x 100 = % of vital capacity expired in 1 second. In this example, (3.013L / 3.504L) X 100 = 85.98% Healthy individual should expel 75%-85% of vital capacity in 1 second, and indicates normal airway resistance. The lower the %, the higher the resistance. 14 7 3/15/23 Nervous Control of Breathing H2O + CO2 H2CO3 H+ + HCO3- Chemoreceptors monitor changes in concentrations of H+, PCO2 and PO2 • Central chemoreceptors in medulla monitor pH (specifically H+) of CSF • CSF pH changes are caused by changes in blood PCO2 • CO2 diffuses from blood to CSF where carbonic anhydrase is present • Carbonic anhydrase builds carbonic acid from CO2 and water • More CO2 in the blood means more H+ in the CSF • Peripheral chemoreceptors are in aortic and carotid bodies • Stimulated by changes in CO2 or O2 in blood • Unlike central receptors, they can respond to H+ produced independently of CO2 • E.g., H+ from ketoacidosis (from fatty acid metabolism) 15 Regulation of Breathing chemoreceptors !!!!! How would breathing rate change? H2O + CO2 H2CO3 H+ + HCO3- 16 8 3/15/23 17 Effects of Hyperventilation and Hypoventilation on Cardiovascular Function Hyperventilation: breathing rate or depth above body’s demand • PO2 rises and PCO2 fall in the air of alveoli • Additional oxygen does not enter blood because hemoglobin is already 98% saturated • Hyperventilation will allow longer breath holding time because we exhale more CO2 during faster and deeper breathing. 18 9 3/15/23 Respiratory Volumes and Capacities Figure 23.24 19 Respiratory Volumes and Capacities Figure 23.24 20 10 3/15/23 Respiratory Volumes and Capacities Figure 23.24 21 11