Airway resistance in patients with healthy lungs undergoing general anaesthesia Respiratory Airway resistance in patients with healthy lungs undergoing general anaesthesia
Conditions
Interventions
Two different induction agents (propofol and thiopental) and three different inhaled anaesthetics (isoflurane, desflurane and sevoflurane) at two different concentrations.
In first g
Hans Rudolph, Kansas City, MO) and a pressure transducer will be inserted between the endotracheal tube and the Y piece of the respiratory circuit, for the measurement of flow and tidal volume and ins
Sponsors
Department of Anaesthesiology, University Hospital of Heraklion (Greece)
Eligibility
Sex/Gender
All
Inclusion criteria
Inclusion criteria: All patients aged 18 to 75 years old, scheduled for elective non abdominal, non thoracic surgery under general anaesthesia
Exclusion criteria
Exclusion criteria: History of asthma, chronic obstructive pulmonary disease (COPD) or malignant hyperthermia, as well as previous treatment with bronchoactive drugs (ß-agonists or antagonists, theophylline, anticholinergics and corticosteroids).
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| Effects on: 1. Total inspiratory resistance (Rrs) and its components 2. Minimal resistance (Rmin) 3. Effective resistance (DRrs) Total inspiratory resistance (Rrs) will be calculated every 5 min using the inspiratory hold maneuver. During the end - inspiration flow pause, the static airway pressure waveform has a characteristic trend, with the highest peak at end-inspiration [Pmax], followed by a rapid drop after the zeroing of flow [P1] and a slow decay until a plateau is reached [Pplat]. The accuracy of the results requires passive conditions therefore all patients were paralysed under deep anaesthesia. Total inspiratory resistance (Rrs) and its components, minimal resistance (Rmin) and effective resistance (DRrs) were calculated according to the equations: Rrs = [Pmax ? Pplat] / V?, Rmin = [Pmax ? P1] / V?, DRrs = [P1- Pplat] / V?, where V? denotes flow. Rmin reflects mainly airway and endotracheal tube resistance and denotes the flow dependent component of Rrs. DRrs represents two phenomena, time - constant inhomogeneities within the lung and the viscoelastic behaviour of the pulmonary tissues and chest wall. Respiratory values will be expressed as the mean of five consecutive breaths. | — |
Secondary
| Measure | Time frame |
|---|---|
| 1. The baseline total inspiratory resistance (Rrs) and its components, minimal resistance (Rmin) and effective resistance (DRrs), between the two groups, propofol and thiopental groups to examine whether the induction with thiopental is associated with increased respiratory resistance 2. In the propofol group: the effects of the three different agents at two different concentrations on respiratory resistance and its components 3. In the propofol group: the effect of the duration of the administration of the aforementioned agents (time effect) 4. In the thiopental group: the effects of the three different agents at two different concentrations on respiratory resistance and its components. 5. In the thiopental group: the effect of the duration of the administration of the aforementioned agents (time effect) | — |
Countries
Greece
Outcome results
None listed