Respiratory System Functions
Gas exchange: Oxygen enters blood and carbon dioxide leaves
Regulation of blood pH: Altered by changing blood carbon dioxide levels
Voice production: Movement of air past vocal folds makes sound
Speech Olfaction: Smell occurs when airborne molecules drawn into nasal cavity
Protection: Against microorganisms by preventing entry and removing them
Non-Respiratory Lung Functions :
Reservoir of blood available for circulatory compensation Filter for circulation: thrombi, microaggregates etc
Metabolic activity: activation: angiotensin III inactivation: noradrenaline bradykinin 5 H-T some prostaglandins Immunological: IgA secretion into bronchial mucus.
The Respiratory Defense System :
The Respiratory Defense System Consists of a series of filtration mechanisms Removes particles and pathogens * Components of the Respiratory Defense System Goblet cells and mucous glands: produce mucus that bathes exposed surfaces Cilia: sweep debris trapped in mucus toward the pharynx (mucus escalator) Filtration in nasal cavity removes large particles Alveolar macrophages engulf small particles that reach lungs.
Pulmonary Function Testing :
Pulmonary Function Testing Tests can be divided into categories: Airway Function Lung Volumes and Gas Distribution Diffusing Capacity Blood Gas and Exchange Tests Cardiopulmonary Exercise Tests.
Indications :
Detect disease Evaluate extent and monitor course of disease
Evaluate treatment
Measure effects of exposures Assess risk for surgical procedures
Contraindications of PFTs :
Patient with poor coordination or lack of ability
Patient with severe dyspnea
Very old or very young patient Those who cannot follow specific instructions
Patients with contagious diseases, i.e., TB Patients with aneurysms, hernias, pulm. emboli, or arrhythmias
Ventilation: Movement of air into and out of lungs
External respiration: Gas exchange between air in lungs and blood Transport of oxygen and carbon dioxide in the blood
Internal respiration: Gas exchange between the blood and tissues
Intrapulmonary Pressure : Intrapulmonary Pressure Also called intra-alveolar pressure Is relative to Patm In relaxed breathing, the difference between Patm and intrapulmonary pressure is small: about —1 mm Hg on inhalation or +1 mm Hg on expiration
Intrapleural Pressure : Pressure in space between parietal and visceral pleura Averages —4 mm Hg Maximum of —18 mm Hg Remains below Patm throughout respiratory cycle
- Transpulmonary Pressure = Alveolar pressure* – Pleural pressure *With no air movement and an open upper airway, mouth pressure equals alveolar pressure
by
Akshaya Srikanth
Pharm.D Resident
Hyderabad, India
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