Ventilation-perfusion relationships (V/Q) in animals For optimal gas transfer to occur in the lung, ventilation and perfusion must be matched. In man for the whole lung, alveolar ventilation and pulmonary blood flow are both about 5 L/min. Therefore, for the whole lung V/Q is about 0.8 – 1.2. Local airway responses and hypoxic pulmonary vasoconstriction […]

Physiology of gas exchange Alveolar gas exchange Usually, gas pressure is considered in terms of ­ total pressure, regardless of whether it is a single gas or a mixture of gases. However each gas in the mixture separately contributes to the total pressure. It is defined as the pres­sure exerted by a particular gas in

Pulmonary blood flow Dual circulation of the lung Bronchial circulation – arterial supply of tracheobronchial tree (as far as the terminal bronchioles), and other thoracic structures. About 2% of cardiac output. Pulmonary circulation – site of gas exchange between alveolar air and capillary blood. Mixed venous blood in pulmonary artery. Main pulmonary artery is much

Pulmonary passageway and pulmonary vascular resistance Respiratory passageway resistance Upper respiratory passageways – relatively large, very little resistance to airflow (unless obstruction such as from food lodging or cancer) Lower respiratory passageways – from medium-sized bronchioles on down, can alter diameter based on autonomic stimulation Parasympathetic – causes bronchoconstriction Sympathetic – inhibits bronchoconstriction Epinephrine – used to treat life-threatening bronchoconstriction

Artificial respiration in animals Artificial respiration is resorted to in cases of cessation of respiration while under general anaesthesia drowning where the animal has been rescued from water – mainly applicable for small animals; poisoning by narcotics or paralytic substances asphyxia from fumes, smoke, gases etc. Method of administration In large animals The animal is

Respiratory Frequency in animals Respiratory frequency refers to the number of respiratory cycles each minute. Respiratory rate is an excel­lent indicator of health status, respiratory frequency can be affected by other factors, such as- body size, age, exercise, excitement, environmental temperature, pregnancy, and, breed. Pregnancy and digestive tract filling increase frequency because they limit the

Mechanism of Respiration Boyle’s law states that at constant temperature and pressure, there is an inverse relationship between volume and pressure of a gas- P1V1 = P2V2 where P is the pressure of the gas (mm of Hg), and V is the volume of gas (ml). Therefore, the pressure inside a closed container will decrease as

Gas laws useful in gas exchange Avogadro’s hypothesis Equal volumes of different gases at equal temperature contain the same number of molecules. Equal numbers of molecules in the same volumes at the same temperature will exert the same pressure. (One mole of any gas will contain 6.02×1023 molecules and will occupy a volume of 22.4 L

Pulmonary Volumes and Capacities Pulmonary volumes and capacities are recorded by Spirometer. The recordings are known as Spirogram. Pulmonary Volumes Tidal Volume (VT)  the volume of air entering or leaving the nose or mouth per breath. It accounts 70% of the total lung capacity. If an animal inhales more forcefully, it can increase the volume of

Trachea and Alveoli Trachea The lungs are paired organs located within the thorax. In general, the left and right lungs have two and four lobes, respectively.  Trachea is the primary passageway of air to the lungs. It is located between larynx and bronchi. The tracheal wall contains cartilaginous rings to prevent collapse of the tracheal airway.