Mechanics of Respiration II Notes PDF

Mechanics of respiration II Surfactant is a mixture of Phospholipids and Ca++. It is secreted by alveolar type II cells. ✓ SURFACE TENSION- Force exerted by fluid in alveoli to resist distension. ✓ Lungs secrete and absorb fluid, leaving a very thin film of fluid, This film of fl...

Mechanics of respiration II Surfactant is a mixture of Phospholipids and Ca++. It is secreted by alveolar type II cells. ✓ SURFACE TENSION- Force exerted by fluid in alveoli to resist distension. ✓ Lungs secrete and absorb fluid, leaving a very thin film of fluid, This film of fluid causes surface tension Function of surfactant: 1. Prevents pulmonary edema by decreasing the filtration forces. 2. Prevents collapse of alveoli during expiration. 3. Decrease work of breathing. Deficiency of surfactant- Causes hyaline disease or respiratory distress syndrome Pulmonary Compliance: overall distensibility and expansibility of the lungs and the thorax Compliance formula C= ∆V/ ∆P (ratio between change in volume and change in pressure). Hysteresis: Compliance is greater during expiration than inspiration. Conditions affecting compliance: Increased: Emphysema. Decreased: Pulmonary fibrosis, edema, or congestion. Sympathetic nervous system: causes relaxation of the bronchial smooth muscle. It is also called bronchial dilatation Parasympathetic nervous system: causes contraction of the bronchial smooth muscle. It is also called bronchial constriction and increases mucus secretion Airflow resistance- resistance produced for airflow during breathing Flow= ∆P pressure/resistance R Bronchodilation → increases radius → decreases resistance → increases air flow. Bronchoconstriction → decreases radius → increases resistance → decreases air flow increased work of breathing is seen in conditions like pneumonia, fibrosis, or bronchial asthma. A 22-year-old man presents to the emergency department with a gunshot wound to the right lower chest. He is hemodynamically stable on arrival but complains of increasing work of breathing. Auscultation of the right chest reveals increased tympany with percussion. A tube thoracostomy is inserted to reduce the intrapleural pressure. Which of the following muscles of respiration reduces the intrapleural pressure?  A. External intercostals B. Intercostalis intimi C. Internal intercostals D. Transversus abdominis A 14-year-old child experiencing an acute asthma attack is treated with albuterol, a sympathetic β2-agonist that relaxes the bronchial smooth muscles. This treatment results in a two-fold increase in the diameter of the child’s airways. Which of the following best describes the resistance in the patient’s airway after treatment compared with that before receiving albuterol? A. Resistance decreases by a factor of 4 B. Resistance decreases by a factor of 16 C. Resistance decreases by a factor of 32 D. Resistance increases by a factor of 4 E. Resistance increases by a factor of 16 Solution- R ∝ 1/r4 In question the diameter is increased two fold means r=2 so; [1/2] ⁴= 1/16 so resistance decreased by a factor of 16