A: Scanning electron microscopy image of Bivona TTS silicone tube after 3 months of use. B: Scanning electron microscopy images of Shiley polyvinyl chloride tracheostomy tube after 3 months of use. C: Scanning electron microscopy images of Tracoe Twist polyurethane tracheostomy tube after 30 d of use. From Reference 23 with permission.
Blom speech cannula. Inspiratory pressure opens the flap valve and closes (expands) the bubble valve, sealing the fenestration so that all of the tidal volume goes to the lungs. As inspiration ends, the flap valve closes. Expiratory pressure collapses the bubble valve, which unblocks the fenestration and directs all of the exhaled air to the upper airway to allow phonation. From Reference 45.
Air flow during ventilator-supported speech production. The black circles represent occlusions, and the gray circle represents higher than usual impedance. A: During inspiration, air flows both toward the lungs and through the larynx. B: During usual expiration, almost all air flows toward the ventilator. This is because the impedance of the ventilator pathway is much lower than that of the laryngeal pathway during speech production. C: During expiration with PEEP, the impedance of the ventilator pathway is higher than usual, so more air flows through the larynx. D: During expiration with a one-way valve, all air flows through the larynx. From Reference 46 with permission.