Anatomy of the Lung ◦Trachea ◦Bronchi ◦Upper lobe ◦Middle lobe ◦Lower lobe ◦Diaphragm
Anatomy of the Lung ◦Terminal bronchiole ◦Respiratory bronchiole ◦Pulmonary vein ◦Pulmonary artery ◦Alveoli ◦Capillary bed
Surfactant ◦A detergent-like complex of lipids and proteins produced by alveolar cells. ◦Decreases the surface tension of the fluid that lines the walls of the alveoli. ◦Less energy is required for breathing. ◦Prevents alveoli from collapsing.
Blood Circulation ◦The heart pumps deoxygenated blood to the pulmonary capillaries for gas exchange to occur between blood and alveoli – air sacs in the lungs. ◦This is known as the pulmonary circulation. ◦Oxygenated blood returns to the heart, where it is pumped out through the aorta by the left ventricle to the rest of the body (systemic circulation). ◦Red blood cells transport oxygen in the body. ◦RBC concentration is known to increase due to living at high altitudes.
Inspiration and Expiration ◦During inspiration, the diaphragm and external intercostals contract to make the thoracic cavity larger. ◦Active process – requires muscle action. ◦During quiet expiration, the diaphragm and external intercostals relax and the thoracic cavity becomes smaller. ◦Passive process, when at rest.
Respiratory Volumes ◦Tidal Volume (V T ) – the amount of air that moves into and out of the lungs during normal, quiet breathing (~500 ml). ◦Inspiratory Reserve Volume (IRV) – the amount of air that can be inspired forcibly beyond the tidal volume ( ml). ◦Expiratory Reserve Volume (ERV) – the amount of air that can be expelled from the lungs after a normal tidal volume expiration ( ml). ◦Residual Volume (RV) – the amount of air that remains in the lungs even after the most strenuous expiration (1200 ml).
Respiratory Capacities ◦Inspiratory Capacity (IC) – the amount of air that can be inspired after a normal tidal volume expiration. ◦IC = TV + IRV ◦Functional Residual Capacity (FRC) – the amount of air remaining in the lungs after a normal tidal volume expiration. ◦FRC = RV + ERV ◦Vital Capacity (VC) – the total amount of exchangeable air (~4800 ml). ◦VC = TV + IRV + ERV ◦Total Lung Capacity (TLC) – the sum of all lung volumes (~6000 ml). ◦TLC = TV + IRV + ERV + RV
Spirogram ◦Note: these values will change acutely with exercise. ◦Rate of breathing and tidal volume increase.
Dead Space ◦Dead Space – some of the inspired air fills the conducting respiratory passageways and never contribute to gas exchange in the alveoli. ◦Anatomical Dead Space (V D )– volume in conducting zone (~150 ml). ◦Alveolar Dead Space – volume of air in alveoli that have ceased to act in gas exchange (due to alveolar collapse or obstruction by mucus, for example). ◦Total Dead Space = anatomical dead space plus alveolar dead space.
Additional Terms ◦Alveolar Volume (V A ) – volume of gas in the alveoli that participates in gas exchange. ◦V A = V T – V D ◦Breathing Frequency (f) – number of breaths per minute. ◦Minute Ventilation/Expired Ventilation ( E ) – total volume of air expired per minute. ◦ E = f x V T ◦Alveolar Ventilation ( A ) – volume of air that reaches the alveoli every minute. ◦ A = f x V A = f x ( V T – V D )
Spirometry ◦Measurement of pulmonary function that is common in clinical medicine ◦Involves measurement of the volume and rate of expired airflow ◦FVC – forced vital capacity – amount of gas expelled when a person takes a deep breath and then forcefully exhales maximally and as rapidly as possible. ◦FEV 1 (forced expired volume in one second) – the amount of air exhaled in the first second of a maximal exhalation. ◦Normally 75-85% of VC ◦FEV 1 /FVC ratio – used to assess and diagnose airway disorders ◦Clinically significant when <0.75 https://www.nhlbi.nih.gov/health/health-topics/images/spirometry.jpg
Why do spirometry? ◦It is used to diagnose airway disorders. ◦Obstructive airway diseases – asthma, chronic bronchitis, emphysema, chronic obstructive pulmonary disease (COPD), etc. ◦FVC normal, FEV 1 below normal. ◦The ratio FEV 1 /FVC ratio is also below normal. ◦Restrictive airway diseases – kyphoscoliosis, neuromuscular disease, pulmonary fibrosis, etc. ◦FVC and FEV 1 are both below normal. ◦The ratio FEV 1 /FVC is approximately normal.
Experiment 1 ◦Using the handheld spirometers, ONE person from each group will be the subject, who will wear a nose piece to prevent air from escaping through the nasal passages. ◦Subject will take a maximal inspiration, then quickly place their mouth around the mouthpiece creating a tight seal, and then exhale AS QUICKLY AND AS FORCEFULLY AS POSSIBLE until he/she cannot exhale anymore. ◦The subject will perform 3 trials, allowing rest time between trials. ◦Record your FVC, FEV 1, and peak flow values in the data sheet. ◦Calculate your FEV 1 /FVC ratio
Spirometry Reference Value Calculator ◦Go to the following website: ◦Select “Hankinson 1999” as your reference source. ◦Enter your gender, race, age, and height and the highest numbers you recorded for FVC and FEV 1 (leave the other boxes blank). ◦Click calculate. ◦Fill in the table in the lab packet. ◦Answer and turn in the lab questions – either before the end of lab or next week.