European Journal of Anaesthesiology

Original Article

Breathing pattern and workload during automatic tube compensation, pressure support and T-piece trials in weaning patients

R. Kuhlen a1c1, M. Max a1, R. Dembinski a1, S. Terbeck a1, E. Jürgens a1 and R. Rossaint a1
a1 University of Aachen Medical School, Department of Anesthesiology, Aachen, Germany

Article author query
kuhlen r   [PubMed][Google Scholar] 
max m   [PubMed][Google Scholar] 
dembinski r   [PubMed][Google Scholar] 
terbeck s   [PubMed][Google Scholar] 
jurgens e   [PubMed][Google Scholar] 
rossaint r   [PubMed][Google Scholar] 


Background and objective: Automatic tube compensation has been designed as a new ventilatory mode to compensate for the non-linear resistance of the endotracheal tube. The study investigated the effects of automatic tube compensation compared with breathing through a T-piece or pressure support during a trial of spontaneous breathing used for weaning patients from mechanical ventilation of the lungs.

Methods: Twelve patients were studied who were ready for weaning after prolonged mechanical ventilation (10.2 ± 8.4 days) due to acute respiratory failure. Patients with chronic obstructive pulmonary disease were excluded. Thirty minutes of automatic tube compensation were compared with 30 min periods of 7 cmH2O pressure support and T-piece breathing. Breathing patterns and workload indices were measured at the end of each study period.

Results: During T-piece breathing, the peak inspiratory flow rate (0.65 ± 0.20 L s−1) and minute ventilation (8.9 ± 2.7 L min−1) were lower than during either pressure support (peak inspiratory flow rate 0.81 ± 0.25 L s−1; minute ventilation 10.2 ± 2.3 L min−1, respectively) or automatic tube compensation (peak inspiratory flow rate 0.75 ± 0.26 L s−1; minute ventilation 10.8 ± 2.7 L min−1). The pressure–time product as well as patients' work of breathing were comparable during automatic tube compensation (pressure–time product 214.5 ± 104.6 cmH2O s−1 min−1, patient work of breathing 1.1 ± 0.4 J L−1) and T-piece breathing (pressure–time product 208.3 ± 121.6 cmH2O s−1 min−1, patient work of breathing 1.1 ± 0.4 J L−1), whereas pressure support resulted in a significant decrease in workload indices (pressure–time product 121.2 ± 64.1 cmH2O s−1 min−1, patient work of breathing 0.7 ± 0.4 J L−1).

Conclusions: In weaning from mechanical lung ventilation, patients' work of breathing during spontaneous breathing trials is clearly reduced by the application of pressure support 7 cmH2O, whereas the workload during automatic tube compensation corresponded closely to the values during trials of breathing through a T-piece.

(Accepted December 2001)

Key Words: RESPIRATION, ARTIFICIAL, ventilator weaning; RESPIRATION, respiratory mechanics, pulmonary ventilation; RESPIRATORY DISORDERS, respiratory insufficiency.

c1 Correspondence to: Ralf Kuhlen, Klinik für Anaesthesiologie, Medizinische Einrichtungen der RWTH Aachen, Pauwelsstrasse 30, D–52074 Aachen, Germany. E-mail:; Tel: +49 241 8088179; Fax: +49 241 8888406