Dead space is reduced in tracheostomy by: (A) 5-10%, (B) 15-20%, (C) 20-30%, (D) 30 - 50%
Answer is D. Airflow resistance of the normal upper airway is substantial, constituting up to 80% of total airway resistance during nose breathing and 50% during mouth breathing.Theoretically, tracheostomy tubes should decrease airflow resistance, but in fact, this does not occur because of the smaller radius (inner diameter 7-8 mm) of the tubes. Tracheostomy tubes may reduce dead space by up to 100 mL -150 mL, 30-50% when compared to spontaneous breathing. This occurs because the tubes are small and bypass the glottic and supraglottic spaces.