Changes in chest wall compartment volumes on induction of anaesthesia with eltanolone, propofol and thiopentone

Abstract

Changes in the expiratory dimensions of the rib cage and abdomen on induction of anaesthesia with eltanolone, propofol and thiopentone were measured in 76 patients using respiratory inductance bands. Calibration of the respiratory inductance plethysmograph was by simultaneous flow measurement with a pneumotachograph. Movement of the vertebral column was restrained with a rigid mattress to allow volume change to be estimated more accurately from rib cage and abdominal dimensions. Rib cage volumes decreased by a median of 125 ml, while the median change in the abdominal compartment was 0. These findings suggest that a reduction in rib cage volume may contribute to the decrease in functional residual capacity after induction of anaesthesia, but that changes in the diaphragmatic-abdominal compartment are not important.

The effect of propofol on airway pressures generated by magnetic stimulation of the phrenic nerves

“…Spens [31], used inductive plethysmography, while supporting the spine to reduce skeletal movements and found a fall in rib cage volume of 307 ml after induction of anaesthesia with propofol. Previous studies have detected a reduction in REEP of 189-285 ml [8,32].…”

New induction agents

“…After breathing 35% ox-ygen for three minutes, subjects received the iv hypnotic agent over 30 sec and tidal volume and respiratory rate were continuously recorded by respiratory inductance plethysmography and a pneumotachograph. 19 The overall incidences of apnoea were 57% for eltanolone, 74% for thiopentone and 100% for propofol. Apnoea ofgreater than 30 sec occurred in 30% of patients receiving eltanolone, 39% with thiopentone and 74% with propofol.…”

Non-invasive ventilation during surgery under neuraxial anaesthesia: a pathophysiological perspective on application and benefits and a systematic literature review

“…The detrimental reduction of FRC toward the closing volume promotes atelectasis formation in dependent lung areas, with lowering of the ventilation to perfusion ratio (V A /Q); in particular, as reported by Froese and Bryan [7], the cranial displacement of the diaphragm is the major cause of FRC drop during GA (regardless of the route of general anaesthetics), with a minor contribution by a decrease of the transverse area of the thorax. However, other authors suggest that the role of the diaphragmatic-abdominal compartment is minor compared to the role of the ribcage muscles (primarily intercostal muscles) in the lowering of FRC during GA: Spens et al [8] compared the effects of three intra-venous induction agents on ribcage and abdominal dimensions of 76 patients without respiratory diseases scheduled for elective surgery; although abdominal volumes remained unchanged, ribcage volumes decreased (median value 136 mL).…”