ABSTRACT
Two main functions of the respiratory system are ventilation (inspiration and expiration of air down to the level of the alveoli) and gas exchange.a In support of these functions, the mucociliary system produces mucus. This tenacious fluid captures inhaled particles and transports them to the nasal and oral mucosa by ciliary action of epithelial cells of the URT and LRT. The cough reflex then acts to expectorate the sequestered mucus. Together, these innate reflex responses cooperate in the clearance mechanism of pulmonary function. For effective gas exchange, therefore, ventilation and perfusion must match closely (calculated as the V/Q ratio). Consequently, any alteration of the V/Q ratio, or interference with the clearance mechanism due to the presence of toxic gases, results in altered lung mechanics. This explains the ensuing clinical effects.
