Dynamic and Quasi-Static Lung Mechanics System for Gas-Assisted and Liquid-Assisted Ventilation

• Published in: IEEE transactions on biomedical engineering 2009-07, Vol.56 (7), p.1938-1948
• Main Authors: Alvarez, Francisco J., Gastiasoro, Elena, Rey-Santano, M. Carmen, Gomez-Solaetxe, Miguel A., Publicover, Nelson G., Larrabe, Juan L.
• Format: Article
• Language: English
• Subjects: Airway Resistance - physiology; Algorithms; Animals; Biomechanical Phenomena; Cardiology; Compliance; Computer errors; Computerized monitoring; dynamic lung mechanics; Electric resistance; Equipment Design; Frequency; inertance; Linear Models; Liquid Ventilation - methods; Lung - physiology; Lung Compliance - physiology; Lung Injury - physiopathology; Lung Volume Measurements; Lungs; Mechanical variables measurement; quasi-static lung mechanics; Rats; Rats, Wistar; Real time systems; resistance; Respiration, Artificial - methods; Respiratory Physiological Phenomena; Respiratory system; total liquid ventilation (TLV); Ventilation
• ISSN: 0018-9294; 1558-2531
• DOI: 10.1109/TBME.2009.2017275

Our aim was to develop a computerized system for real-time monitoring of lung mechanics measurements during both gas and liquid ventilation. System accuracy was demonstrated by calculating regression and percent error of the following parameters compared to standard device: airway pressure difference (DeltaP aw ), respiratory frequency (f R ), tidal volume (V T ), minute ventilation (V' E ), inspiratory and expiratory maximum flows (V' ins,max , V' exp,max ), dynamic lung compliance (C L,dyn ), resistance of the respiratory system calculated by method of Mead-Whittenberger (R rs,MW ) and by equivalence to electrical circuits (R rs,ele ), work of breathing (W OB ), and overdistension. Outcome measures were evaluated as function of gas exchange, cardiovascular parameters, and lung mechanics including mean airway pressure (mP aw ). DeltaP aw , V T , V' ins,max , V' exp,max , and V' E measurements had correlation coefficients r = 1.00, and %error < 0.5%. f R , C L,dyn , R rs,MW , R rs,ele , and W OB showed r ges 0.98 and %error < 5%. Overdistension had r = 0.87 and %error < 15%. Also, resistance was accurately calculated by a new algorithm. The system was tested in rats in which lung lavage was used to induce acute respiratory failure. After lavage, both gas- and liquid-ventilated groups had increased mP aw and W OB , with decreased V T , V' E , C L,dyn , R rs,MW , and R rs,ele compared to controls. After 1-h ventilation, both injured group had decreased V T , V' E , and C L,dyn , with increased mP aw , R rs,MW , R rs,ele , and W OB . In lung-injured animals, liquid ventilation restored gas exchange, and cardiovascular and lung functions. Our lung mechanics system was able to closely monitor pulmonary function, including during transitions between gas and liquid phases.