Continuous on-line measurements of respiratory system, lung and chest wall mechanics during mechanic ventilation.
OBJECTIVE
We present a concept of on-line, manoeuvre-free monitoring of respiratory mechanics during dynamic conditions, displaying calculated alveolar pressure/volume curves continuously and separating lung and chest wall mechanics.


METHODS
Prospective observational study.


METHODS
Intensive care unit of a university hospital.


METHODS
Ten ventilator-treated patients with acute lung injury.


METHODS
Different positive end-expiratory pressure (PEEP) and tidal volumes, low flow inflation.


RESULTS
Previously validated methods were used to present a single-value dynostatic compliance for the whole breath and a dynostatic volume-dependent initial, middle and final compliance within the breath. A high individual variation of respiratory mechanics was observed. Reproducibility of repeated measurements was satisfactory (coefficients of variations for dynostatic volume-dependent compliance: < or =9.2% for total respiratory system, < or =18% for lung). Volume-dependent compliance showed a statistically significant pattern of successively decreasing compliance from the initial segment through the middle and final parts within each breath at all respiratory settings. This pattern became more prominent with increasing PEEP and tidal volume, indicating a greater distension of alveoli. No lower inflection point (LIP) was seen in patients with respiratory rate 20/min and PEEP at 4 cmH2O. A trial with low flow inflation in four of the patients showed formation of a LIP in three of them and an upper inflection in one.


CONCLUSIONS
The monitoring concept revealed a constant pattern of successively decreasing compliance within each breath, which became more prominent with increasing PEEP and tidal volume. The monitoring concept offers a simple and reliable method of monitoring respiratory mechanics during ongoing ventilator treatment.
Kárason
S
S
Department of Anaesthesia and Intensive Care, Sahlgrenska University Hospital, 413 45 Göteborg, Sweden. sigge.karason@molndal.mail.telia.com
Søndergaard
S
S
Lundin
S
S
Stenqvist
O
O
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007442:Intubation, Intratracheal; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000628:therapy*; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics