Articles: closed-circuit-anesthesia.
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Anesthesia and analgesia · Feb 1997
Randomized Controlled Trial Clinical TrialUptake of desflurane and isoflurane during closed-circuit anesthesia with spontaneous and controlled mechanical ventilation.
Although theoretical models predict uptake of inhaled anesthetics during closed-circuit anesthesia (CCA), clinical data for most anesthetics are conflicting or non-existent. In addition, the effects of patient characteristics and mode of ventilation on anesthetic uptake are unclear. Forty-one ASA physical status I or II adult patients undergoing a variety of 1-1.5 h surgical procedures were randomly allocated to receive CCA with desflurane or isoflurane with ventilation being either spontaneous or controlled. ⋯ Patient characteristics (age, height, weight, weight3/4, and body surface area) were comparable between groups and did not correlate with uptake. The virtually constant uptake after wash-in of desflurane and isoflurane contrasts with the square root of time model of Lowe and Ernst. These findings may greatly simplify CCA.
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Randomized Controlled Trial Clinical Trial
The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system.
The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 21.min-1) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (51.min-1) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 51.min-1 fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. ⋯ Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l-1) but at a fresh gas flow of 51.min-1 there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.
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J. Tongji Med. Univ. · Jan 1997
Randomized Controlled Trial Clinical TrialMultiple respiratory gas monitoring causes changes of inspired oxygen concentration in closed anesthesia system.
Effect of multiple respiratory gas monitoring (MRGM) on inspired concentration of oxygen in circuit system during closed anesthesia was studied in 51 adult patients scheduled for abdominal surgery. Required flow rate of fresh oxygen (OFR), inspired oxygen concentration (FiO2) and oxygen saturation of pulse oximeter (SpO2) were measured continuously. Patients were equally divided into three groups at random, group C (no MRGN used), group M1 (using MRGM with its tail gas returned to circuit system), group M2 (using MRGM without tail gas returned). ⋯ In group M1, FiO2 decreased by 16% at 60 min and 34% at 180 min and the decrease was significantly greater than that in group C (P < 0.01). In group M2, FiO2 remained constant during closed anesthesia, which was much higher than those in group C and M1. The tail gas of Capnomac Ultima MRGM contained less oxygen than its sample gas drawn from circuit system simultaneously.
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Randomized Controlled Trial Clinical Trial
Gas leakage and the laryngeal mask airway. A comparison with the tracheal tube and facemask during spontaneous ventilation using a circle breathing system.
The ability of the laryngeal mask airway, tracheal tube and facemask to provide a leak free seal in a clinical setting was assessed by measuring the minimal fresh gas flows needed in a closed circle system during spontaneous ventilation on 60 subjects. The fresh gas flow was reduced until no spillage occurred from the pop-off valve. This fresh gas flow was taken to represent the sum of gas uptake by the subject and gas leakage from the circuit. ⋯ The fresh gas flow required for the facemask group was significantly higher than that for the laryngeal mask airway or tracheal tube groups (p < 0.01). There was no significant difference between the fresh gas flows required for the tracheal tube and laryngeal mask airway group. We conclude that the laryngeal mask airway provides as good a gas tight seal as a tracheal tube in this context and would be of benefit in reducing anaesthetic gas pollution.
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Randomized Controlled Trial Clinical Trial
[Adaptive lung ventilation (AVL). Evaluation of new closed loop regulated respiration algorithm for operation in the hyperextended lateral position].
The lateral decubitus position is the standard position for nephrectomies. There is a lack of data about the effects of this extreme position upon respiratory mechanics and gas exchange. In 20 patients undergoing surgery in the nephrectomy position, we compared a new closed-loop-controlled ventilation algorithm, adaptive lung ventilation (ALV), which adapts the breathing pattern automatically, to the respiratory mechanics with conventionally controlled mandatory ventilation (CMV). ⋯ However, an adaptation to individual respiratory mechanics was clearly evident with ALV. In conclusion, we found that the effects of positioning for nephrectomy are minor and may give rise to problems only in patients with restrictive lung disease. The novel ALV controller automatically selects ventilatory parameters that are clinically sound and are better adapted to the respiratory mechanics of ventilated patients than the standardized settings of CMV are.