Dead-space reduction and tracheal pressure measurements using a coaxial inner tube in an endotracheal tube.
OBJECTIVE
To evaluate the effects on CO(2) washout of the coaxial double lumen tube (DLT) as compared to a standard endotracheal tube (ETT) and tracheal gas insufflation (TGI). Precision of tracheal pressure monitoring through the DLT and safety issues, including intrinsic PEEP (PEEPi) formation during DLT ventilation, were also evaluated.


METHODS
Lung model study.


METHODS
University research laboratory.


RESULTS
CO(2) washout was analysed in a lung model by measuring single alveolar CO(2) concentration during DLT ventilation as compared to standard ETT ventilation, at different minute ventilation (6-14 l/min) and different CO(2)-output levels (180 ml/min, 240 ml/min, and 300 ml/min). At a CO(2) output level of 240 ml/min the CO(2) washout was also compared to tidal volume-adjusted continuous TGI and expiratory synchronised TGI. Precision of tracheal pressure monitoring and PEEPi formation during DLT ventilation was evaluated by comparing pressure in each limb above the tube to reference tracheal pressure, varying I:E ratios (1:2, 1:1, and 2:1), tidal volumes (300-700 ml), breathing frequencies (15-25), and compliance (20-50 ml/cmH(2)O). DLT ventilation had the same efficacy in removing CO(2) as continuous and expiratory synchronised TGI, reducing single alveolar CO(2) concentration by 9-21% compared to normal ventilation. Tracheal pressure could be measured through the DLT with high precision. There was only marginal formation of PEEPi at tidal volumes <or=600 ml, I:E ratio <or=1:1, and compliance <or=35 ml/cmH(2)O.


CONCLUSIONS
The double lumen tube is as effective as tracheal gas insufflation in reducing CO(2) tension. Tracheal pressure and formation of PEEPi can be monitored with high precision without interrupting ventilation.
Department of Anaesthesia and Intensive Care, Sahlgrenska University Hospital, 413 45 Göteborg, Sweden.
S
S
Lethvall
S
S
Søndergaard
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S
Kárason
S
S
Lundin
O
O
Stenqvist
D002138:Calibration; D006801:Humans; D006935:Hypercapnia / Q000209:etiology / Q000517:prevention & control; D007327:Insufflation / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D007442:Intubation, Intratracheal / Q000295:instrumentation*; D008953:Models, Anatomic; D018467:Positive-Pressure Respiration, Intrinsic / Q000209:etiology / Q000517:prevention & control; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D012126:Respiratory Dead Space; D012128:Respiratory Distress Syndrome / Q000628:therapy; D013990:Tidal Volume; D014132:Trachea / Q000502:physiology*