Respiratory Physiology (LEC 4) Past Paper PDF 2024

Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 Lung Physiology Page|1  Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 By the end of lecture 4; you will be able...

Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 Lung Physiology Page|1  Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 By the end of lecture 4; you will be able to: ▪ Define different lung volumes and capacities ▪ Explain the methods used for determination of FRC,RV,TLC ▪ Know the types of Lung dead spaces and their importance Work of Breathing During normal quiet breathing, all respiratory muscle contraction occurs during inspiration; expiration is almost entirely a passive process caused by elastic recoil of the lungs and chest cage. Thus, under resting conditions, the respiratory muscles normally perform “work” to cause inspiration but not to cause expiration. The work of inspiration can be divided into three fractions: (1) that required to expand the lungs against the lung and chest elastic forces, called compliance work or elastic work (2) that required to overcome the viscosity of the lung and chest wall structures, called tissue resistance work (3) that required to overcome airway resistance to movement of air into the lungs, called airway resistance work. Energy Required for Respiration During normal quiet respiration, only 3 to 5 per cent of the total energy expended by the body is required for pulmonary ventilation. But during heavy exercise, the amount of energy required can increase as much as 50-fold, especially if the person has any degree of increased airway resistance or decreased pulmonary compliance. Therefore, one of the major limitations on the intensity of exercise that can be performed is the person’s ability to provide enough muscle energy for the respiratory process alone. Pulmonary Volumes and Capacities A simple method for studying pulmonary ventilation is to record the volume movement of air into and out of the lungs, a process called spirometry. Pulmonary Volumes 1. The tidal volume is the volume of air inspired or expired with each normal breath; it amounts to about 500 milliliters in the adult male. Page|2  Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 2. The inspiratory reserve volume is the extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force; it is usually equal to about 3000 milliliters. 3. The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; this normally amounts to about 1100 milliliters. 4. The residual volume is the volume of air remaining in the lungs after the most forceful expiration; this volume averages about 1200 milliliters. Pulmonary Capacities In describing events in the pulmonary cycle, it is sometimes desirable to consider two or more of the volumes together. Such combinations are called pulmonary capacities. 1. The inspiratory capacity equals the tidal volume plus the inspiratory reserve volume. This is the amount of air (about 3500 milliliters) a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount. 2. The functional residual capacity equals the expiratory reserve volume plus the residual volume. This is the amount of air that remains in the lungs at the end of normal expiration (about 2300 milliliters). 3. The vital capacity equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume. This is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent expiring to the maximum extent (about 4600 milliliters). 4. The total lung capacity is the maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800 milliliters); it is equal to the vital capacity plus the residual volume. All pulmonary volumes and capacities are about 20 to 25 per cent less in women than in men, and they are greater in large and athletic people than in small and asthenic people. VC = IRV + VT + ERV VC = IC + ERV TLC = VC + RV TLC = IC + FRC FRC = ERV + RV Page|3 Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 Page|4  Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 Dead Space and Its Effect on Alveolar Ventilation Some of the air a person breathes never reaches the gas exchange areas but simply fills respiratory passages where gas exchange does not occur, such as the nose, pharynx, and trachea. This air is called dead space air because it is not useful for gas exchange. On expiration, the air in the dead space is expired first, before any of the air from the alveoli reaches the atmosphere. Normal Dead Space Volume. The normal dead space air in a young adult is 150 milliliters Anatomic Versus Physiologic Dead Space On occasion, some of the alveoli themselves are nonfunctional or only partially functional because of absent or poor blood flow through the adjacent pulmonary capillaries. Therefore, from a functional point of view, these alveoli must also be considered dead space. When the alveolar dead space is included in the total measurement of dead space, this is called the physiologic dead space, in contradistinction to the anatomic dead space. In a normal person, the anatomic and physiologic dead spaces are nearly equal because all alveoli are functional in the normal lung, but in a person with partially functional or nonfunctional alveoli in some parts of the lungs, the physiologic dead space may be as much as 10 times the volume of the anatomic dead space, or 1 to 2 liters. Page|5  Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 FORCED EXPIRATORY VITAL CAPACITY AND In the pulmonary function laboratory, information about airway resistance in a patient with lung disease can be obtained by measuring the flow rate during a maximal expiration. the spirometer record obtained when a subject inspires maximally and then exhales as hard and as completely as he or she can. FEV1.0 is called the forced expiratory volume: is The volume exhaled in the first second. FVC is the forced vital capacity : is the total volume exhaled, (this is often slightly less than the vital capacity measured on a slow exhalation) Normally, the FEV1.0 is about 80% of the FVC. Page|6  Respiratory Physiology.LEC.4 Dr.Zainab Ali Altufailie \2024 **Home work: Q:what is the differences between anatomical Vs Physiological Dead spaces??? Q:define spirometry ? can you write about normal spirogram? Q:give an example of abnormal spirogram reading? Q:what are the lung volumes that cant be measured by spirometry? Q:differentiate between obstructive and restrictive lung disease? Good Luck Page|7