Abstract
Objective
To investigate the role played by the endotracheal tube (ETT) in the correct evaluation of respiratory system mechanics with the end inflation occlusion method during constant flow controlled mechanical ventilation.
Setting
General ICU, university of Rome “La Sapienza”.
Patients
12 consecutive patients undergoing controlled mechanical ventilation.
Methods
We compared the values of minimal resistance of the respiratory system (i.e. airway resistance) (RRS min) obtained: i) subtracting the theoretical value of ETT resistance from the difference between P max and P1, measured on airway pressure tracings obtained from the distal end of the ETT; ii) directly measuring airway pressure 2 cm below the ETT, thus automatically excluding ETT resistance from the data.
Results
The values of RRS min obtained by measuring airway pressure below the ETT were significantly lower than those obtained by measuring airway pressure at the distal end of the ETT and subtracting the theoretical ETT resistance (4.5±2.8 versus 2.5±1.6 cm H2O/l/s,p<0.01).
Conclusion
When precise measurements of ohmic resistances are required in mechanically ventilated patients, the measurements must be obtained from airways pressure data obtained at tracheal level. The “in vivo” positioning of ETT significantly increases the airflow resistance of the ETT.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Rossi A, Gottfried SB, Higgs BD, Zocchi O, Grassino A, Milic-Emili J (1985) Respiratory mechanics in mechanically ventilated patients with respiratory failure. J Appl Physiol 58:1849–1858
Broseghini C, Brandolese R, Poggi G, Polese G, Manzin E, Milic-Emili J, Rossi A (1988) Respiratory mechanics during the first day of mechanical ventilation in patients with pulmonary edema and chronic airway obstruction. Am Rev Respir Dis 138:355–361
Conti G, Dell'Utri D, Vilardi V, De Blasi AR, Pelaia P, Antonelli M, Bufi M, Rosa G, Gasparetto A (1992) Propofol induces bronchodilation in mechanically ventilated chronic obstructive pulmonary disease (COPD) patients. Acta Anaesthesiol Scand 36: 105–109
D'Angelo E, Robatto FM, Calderini E, Tavola M, Bono D, Torri G, Milic-Emili J (1991) Pulmonary and chest wall mechanics in anesthetized paralyzed humans. J Appl Physiol 70:2602–2610
Poggi R, Brandolese R, Bernasconi M, Manzin E, Rossi A (1989) Doxofylline and respiratory mechanics; short-term effects in mechanically ventilated patients with airflow obstruction and respiratory failure. Chest 96:772–778
Berhakis PK, Higgs BD, Baydur A, Zin WA, Milic-Emili J (1983) Respiratory mechanics during halothane anesthesia and anesthesia-paralysis in humans. J Appl Physiol 55:1085–1092
Gottfried SB, Rossi A, Higgs BD, Calverley PMA, Zocchi L, Bozic C, Milic-Emili J (1985) Noninvasive determination of respiratory system mechanics during mechanical ventilation for acute respiratory failure. Am Rev Respir Dis 131:414–420
Wright PE, Marini JJ, Bernard GR (1989) In vitro versus in vivo comparison of endotracheal tube airflow resistances. Am Rev Respir Dis 140:10–16
De Blasi RA, Conti G, Antonelli M, Bufi M, Gasparetto A (1992) A fibre optics system for the evaluation of airways pressure in mechanically ventilated patients. Intensive Care Med 18:405–409
Pesenti A, Pelosi A, Rossi N, Virtuani A, Brazzi L, Rossi A (1991) The effects of positive end-expiratory pressure on respiratory resistance in patients with the adult respiratory distress syndrome and in normal anesthetized subjects. Am Rev Respir Dis 144:101–107
Eissa NT, Ranieri VM, Corbeil C, Chasse M, Braidy J, Milic-Emili J (1991) Effects of positive end-expiratory pressure, lung volume and inspiratory flow on interrupter resistance in patients with adult respiratory distress syndrome. Am Rev Respir Dis 144:538–543
Kochi T, Okubo S, Zin WA, Milic-Emili J (1988) Flow and volume dependence of pulmonary mechanics in anesthetized cats. J Appl Physiol 64:441–450
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Conti, G., De Blasi, R.A., Lappa, A. et al. Evaluation of respiratory system resistance in mechanically ventilated patients: The role of the endotracheal tube. Intensive Care Med 20, 421–424 (1994). https://doi.org/10.1007/BF01710652
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01710652