Fletcher, Margaret Elizabeth; (1993) Respiratory compliance in sedated and anaesthetised infants. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

The primary aims of this thesis were to investigate the effects of halothane anaesthesia on total respiratory compliance (Crs) in infants and young children, and to determine whether measurements obtained during anaesthesia were influenced by paralysis or inflation volume. Sequential measurements of Crs in 20 infants, anaesthetised with halothane and nitrous oxide, demonstrated that no significant difference in Crs occurred following paralysis providing ventilation mimicked that observed in the same infant during spontaneous breathing, suggesting that paralysis per se had a minimal influence on the results. However, when tidal volumes were increased approximately twofold, there was an immediate and highly significant increase in Crs, with individual changes ranging from 17% to 101% (mean 53%) greater than that observed during ventilation with smaller tidal volumes (p < 0.0001). Paired measurements during spontaneous breathing in 17 infants before and after induction of anaesthesia demonstrated that, as in adults, halothane anaesthesia is associated with a highly significant reduction in Crs in infants. The mean reduction compared with pre anaesthetic values was 34.7% (range 0% to 58.3%), with a significant reduction in tidal volume also occurring (mean 42.5%, range 26.7% to 61.4%). Results from 7 of these infants, in whom additional measurements during anaesthesia paralysis were possible, demonstrated that the reduction in Crs during anaesthesia could be reversed by paralysing and ventilating the infant with larger tidal volumes, approximating those observed during spontaneous breathing prior to induction of anaesthesia. These results may have important implications for the interpretation of Crs measurements obtained from ventilated infants. Furthermore, they demonstrate that results from anaesthetised infants should not be used as reference values for conscious infants. In addition to achieving the primary aims, work performed during the execution of this thesis resulted in 1. development of an improved method of measuring Crs in sedated infants with unstable end expiratory levels. 2. application of these techniques to infants with respiratory disease. 3. development of an interactive operator controlled system for computerised data collection and analysis.

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