Background: Tracheostomy is associated with negative effects on voice, speech, and feeding/swallowing. Speaking valves have beneficial effects in these areas but are often contra-indicated in children with airway problems due to high transtracheal pressure (TTP). Valves are modified by drilling to reduce excessive TTP. We hypothesized that a standardized approach to assessment and valve modification by drilling improves valve tolerance and allows widespread successful use.Methods: Following development of a standardized multidisciplinary protocol for patient selection, valve modification and valve prescription at our center, we retrospectively collected information from clinical notes relating to clinical indication and medical history of all children undergoing speaking valve assessment from February 2014 to June 2017. We designed a questionnaire which was delivered to the parents of children receiving both modified and standard valves enquiring about voice, feeding, communication, and suctioning.Results: Data on 45 children were collected. Thirteen had normal TTP and were given standard valves and 32 had high TTP, all of whom had their valves modified resulting in good tolerance. 17 Children were on positive pressure ventilation at the time of placement. The survey response rate was 83%. Parents report a high degree of satisfaction with modified valves and report positive effects in terms of voice, speech, and feeding/swallowing similar to those reported for standard valves.Conclusions: Speaking valves can be successfully and safely modified in children, providing valves to many patients previously deemed unsuitable. We report positive parental experiences of these modified valves in line with those reported with standard valves.
The effects of the withdrawal of nitrous oxide from the inspired gas mixture were studied in 10 spontaneously breathing children during nitrous oxide-halothane anaesthesia, before and during surgery, using a computerized system for the measurement, recording and analysis of data. Before surgery the decline in the alveolar nitrous oxide concentration was associated with an increase in minute ventilation (32.7%, P less than 0.05), and a decrease in alveolar carbon dioxide concentration (8.4%, P less than 0.05). These effects were produced solely by an increase in tidal volume (42.7%, P less than 0.001), as no significant change in respiratory rate was observed. The hypoventilation produced by an alveolar mixture of 60% nitrous oxide and 0.9% halothane, a reduction of VE by 50%, exceeded the hypoventilation caused by 0.9% halothane alone, which reduced VE by 36.6%; and the hypoventilation produced by nitrous oxide and halothane was rapidly reversed by the withdrawal of nitrous oxide from the inspired gas mixture. During surgery all indices of ventilation were stimulated, and there was greater variability of response, but the pattern and degree of change in response to nitrous elimination, VE increased by 33.3%, VT by 33.8%, closely resembled the changes before surgery. Five children had received papaveretum as premedication, and five thiopentone per rectum; the depression of carbon dioxide responsiveness was more severe in the group who received papaveretum, and their responses to nitrous oxide elimination were less than, and occurred later than the responses in the group given thiopentone.
The accuracy of tidal volume measurements made with a Wright Haloscale infant respirometer in children breathing spontaneously during general anaesthesia was assessed by a bench test. The tidal volumes and peak flow rates of 20 spontaneously breathing, anaesthetised children were measured with a pneumotachograph before and during surgery, and similar volumes, at the same flow rates, were delivered by a calibrated syringe simultaneously to the respirometer and a pneumotachograph. The results reveal that the mean (+/- s.d.) peak gas flow rates of children aged 6 years and less, 7.5 (+/- 1.6) and 9.3 (+/- 0.1) l/min before surgery and during surgery respectively, are significantly less than the peak flow rates, 11.3 (+/- 1.0) and 11.9 (+/- 1.5) before and during surgery, respectively, of children aged more than 6 years; and that the respirometer underestimates tidal volume by 10% when the peak flow rate is 11 l/min, and the percentage error in tidal volume estimation by the respirometer increases as the peak gas flow declines below 10 l/min.
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