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Original ArticleOpen Access
Effect of Severity of Pulmonary Disease on Nitrous Oxide Washin and Washout Characteristics
Vichitvejpaisal P 
,
Joshi GP ,
Liu l ,
White PF
,
Joshi GP ,
Liu l ,
White PF The influence of chronic obstructive pulmonary disease (COPD) on the nitrous oxide (Np)
washin and washout characteristics was evaluated in 90 (ASA II-III) males undergoing elective
peripheral surgery under general anaesthesia with controlled ventilation. Patients were classified by
preoperative bedside pulmonary function testing into three groups. Group I (n=30), patients
without COPD (FEVJFVC > 80% predicted values; control group); Group II (n=30), patients with
mild COPD (FEVJFVC = 65-79% of predicted values); and Group III (n=30), patients with
moderate COPD (FEVJFVC = 50-64% of predicted values).
The anaesthetic technique was standardized for all patients. The Datex Capnomac Ultimaâ„¢
monitor was used to measure the inspired and expired concentrations of nitrous oxide (N,O),
carbon dioxide (C02), and isoflurane. The duration of both Np washin (time from start of :Np
administration to equilibrium of inspired and expired Np concentrations) and 5 per cent washout
(time from discontinuation of Np to an expired Np concentration of 5 per cent of the equilibrium
value) were recorded. The duration of N20 washin and washout were significantly prolonged in
Groups II and III (P < 0.001) as compared to the control group (Group I). The end-tidal C02 concentration
decreased significantly during Np washout without causing oxygen desaturation (Sp02
< 90%). We conclude that the duration of N20 washin and washout were significantly prolonged
in anaesthetized patients with COPD which may delay the induction and recovery from Np
anaesthesia.
washin and washout characteristics was evaluated in 90 (ASA II-III) males undergoing elective
peripheral surgery under general anaesthesia with controlled ventilation. Patients were classified by
preoperative bedside pulmonary function testing into three groups. Group I (n=30), patients
without COPD (FEVJFVC > 80% predicted values; control group); Group II (n=30), patients with
mild COPD (FEVJFVC = 65-79% of predicted values); and Group III (n=30), patients with
moderate COPD (FEVJFVC = 50-64% of predicted values).
The anaesthetic technique was standardized for all patients. The Datex Capnomac Ultimaâ„¢
monitor was used to measure the inspired and expired concentrations of nitrous oxide (N,O),
carbon dioxide (C02), and isoflurane. The duration of both Np washin (time from start of :Np
administration to equilibrium of inspired and expired Np concentrations) and 5 per cent washout
(time from discontinuation of Np to an expired Np concentration of 5 per cent of the equilibrium
value) were recorded. The duration of N20 washin and washout were significantly prolonged in
Groups II and III (P < 0.001) as compared to the control group (Group I). The end-tidal C02 concentration
decreased significantly during Np washout without causing oxygen desaturation (Sp02
< 90%). We conclude that the duration of N20 washin and washout were significantly prolonged
in anaesthetized patients with COPD which may delay the induction and recovery from Np
anaesthesia.
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