We studied 15 subjects with spinal cord injuries or neuromuscular diseases, who lived in extended-care facilities or at home. Thirteen subjects received ventilation with volume-controlled positive pressure and produced speech with the tracheostomy tube cuff deflated or with a cuffless tracheostomy tube (either fenestrated or unfenestrated). All but one subject routinely maintained a deflated cuff throughout the waking hours. Four subjects routinely used one-way inspiratory valves for speaking. Five subjects actively triggered the ventilator to increase breathing frequency when speaking with their usual ventilator settings. The remaining two subjects had used volume-controlled, positive-pressure ventilators in past years, but at the time of the study were routinely using phrenic nerve pacers (combined with one-way valves) for ventilation and speech production HQ Pharmacy Canada. The study protocol was approved by all appropriate human subjects committees, and informed consent was obtained from all subjects.
Subjects were studied using a standard ventilator with settings matched as closely as possible with those on the subject’s own ventilator. These settings are termed the usual condition. Next, ventilator adjustments were made (with one-way valves removed), including the following: (1) lengthening inspiratory time (Ti), (2) applying positive end-expiratory pressure (PEEP), and (3) combining lengthened Ti and PEEP.
Lengthened Ti can improve speech produced during the inspiratory phase of the ventilator cycle. With lengthened Ti, air flows through the larynx longer so that Pt remains above the voicing threshold longer during inspiration Kamagra shop. Also, the flow is lower so that the rate of rise of Pt is reduced.
When speaking during usual expiration, nearly all the air in the lungs flows toward the ventilator because the ventilator pathway offers much lower impedance (ie, primarily resistance) to flow than does the laryngeal pathway . PEEP impedes expiratory flow and adds a threshold occlusion pressure to the ventilator expiratory line so that more air flows through the larynx than toward the ventilator . Thus, Pt stays above the voicing threshold longer during expiration than without PEEP (as long as the impedance offered by the larynx is adequately high, the usual case during speech production). A one-way valve shunts all expired air through the larynx by occluding the ventilator line.