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Assessment of respiratory system compliance by a flow recording method
Author(s) -
Darowski M.,
GottliebInacio I.,
Ludwigs U.,
Hedenstierna G.
Publication year - 1995
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1995.tb04100.x
Subject(s) - medicine , respiratory system , anesthesia , compliance (psychology) , airway , pulmonary compliance , significant difference , flow (mathematics) , mechanics , psychology , social psychology , physics
Standard methods for the assessment of the compliance of the respiratory system require recordings of both airway pressure and ventilatory volume. A method based on the recording of respiratory flow only, with no need of measuring airway pressure was reported some years ago. The purpose of the present study was to test a modification of this flow‐recording technique. The technique is based on the measurement of inspiratory flow with and without the addition of a source of external compliance added to the inspiratory circuit. The difference in inspiratory flow between these two situations can be used to derive the compliance of the respiratory system. The method was tested in model experiments and in patients with acute respiratory failure, and compared with a standard method based on airway pressure and inspiratory gas flow recording. Model experiments showed strong correlation between the new flow‐recording method and the standard method (r—0.99, P <0.001) with a coefficient of variation of less than 2% with both methods. In patients with acute respiratory failure, the flow and standard methods gave similar results when no end‐inspiratory pause was applied (mean difference 5±40 ml/kPa (x±s.d.)). The standard method gave significandy higher compliance values, different from the flow method, when an end‐inspiratory pause of 10% was applied (mean difference 53 ±2 ml/kPa, P <0.01). The flow method was not influenced by the use of an end‐inspiratory pause. In conclusion, the flow method measures dynamic compliance and is not influenced by end‐inspiratory or end‐expiratory flow. It requires only a flow‐sensor for the measurement of relative values, reducing the need for calibration procedures. However, the flow method cannot replace conventional technique for assessment of static compliance.