scholarly journals On-line monitoring of intrinsic PEEP in ventilator-dependent patients

2000 ◽  
Vol 89 (3) ◽  
pp. 985-995 ◽  
Author(s):  
G. Nucci ◽  
M. Mergoni ◽  
C. Bricchi ◽  
G. Polese ◽  
C. Cobelli ◽  
...  
Keyword(s):  
Least Squares Method ◽  
Recursive Least Squares ◽  
Intrinsic Peep ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
On Line ◽  
Highly Correlated ◽  
Ventilated Patients

Measurement of the intrinsic positive end-expiratory pressure (PEEPi) is important in planning the management of ventilated patients. Here, a new recursive least squares method for on-line monitoring of PEEPi is proposed for mechanically ventilated patients. The procedure is based on the first-order model of respiratory mechanics applied to experimental measurements obtained from eight ventilator-dependent patients ventilated with four different ventilatory modes. The model PEEPi (PEEPi,mod) was recursively constructed on an inspiration-by-inspiration basis. The results were compared with two well-established techniques to assess PEEPi: end-expiratory occlusion to measure static PEEPi (PEEPi,st) and change in airway pressure preceding the onset of inspiratory airflow to measure dynamic PEEPi (PEEPi,dyn). PEEPi,mod was significantly correlated with both PEEPi,dyn( r = 0.77) and PEEPi,st ( r= 0.90). PEEPi,mod (5.6 ± 3.4 cmH2O) was systematically >PEEPi,dyn and PEEPi,st(2.7 ± 1.9 and 8.1 ± 5.5 cmH2O, respectively), in all the models without external PEEP. Focusing on the five patients with chronic obstructive pulmonary disease, PEEPi,mod was significantly correlated with PEEPi,st ( r = 0.71), whereas PEEPi,dyn ( r = 0.22) was not. When PEEP was set 5 cmH2O above PEEPi,st, all the methods correctly estimated total PEEP, i.e., 11.8 ± 5.3, 12.5 ± 5.0, and 12.0 ± 4.7 cmH2O for PEEPi,mod, PEEPi,st, and PEEPi,dyn, respectively, and were highly correlated (0.97–0.99). We interpreted PEEPi,mod as the lower bound of PEEPi,st and concluded that our method is suitable for on-line monitoring of PEEPi in mechanically ventilated patients.

Partitioning of respiratory mechanics in mechanically ventilated patients

1991 ◽  
Vol 71 (6) ◽  
pp. 2425-2433 ◽  
Author(s):  
G. Polese ◽  
A. Rossi ◽  
L. Appendini ◽  
G. Brandi ◽  
J. H. Bates ◽  
...  
Keyword(s):  
Pulmonary Edema ◽  
Chest Wall ◽  
Respiratory System ◽  
Lung Mechanics ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Respiratory System Mechanics ◽  
Ventilated Patients

In ten mechanically ventilated patients, six with chronic obstructive pulmonary disease (COPD) and four with pulmonary edema, we have partitioned the total respiratory system mechanics into the lung (l) and chest wall (w) mechanics using the esophageal balloon technique together with the airway occlusion technique during constant-flow inflation (J. Appl. Physiol. 58: 1840–1848, 1985). Intrinsic positive end-expiratory pressure (PEEPi) was present in eight patients (range 1.1–9.8 cmH2O) and was due mainly to PEEPi,L (80%), with a minor contribution from PEEPi,w (20%), on the average. The increase in respiratory elastance and resistance was determined mainly by abnormalities in lung elastance and resistance. Chest wall elastance was slightly abnormal (7.3 +/- 2.2 cmH2O/l), and chest wall resistance contributed only 10%, on the average, to the total. The work performed by the ventilator to inflate the lung (WL) averaged 2.04 +/- 0.59 and 1.25 +/- 0.21 J/l in COPD and pulmonary edema patients, respectively, whereas Ww was approximately 0.4 J/l in both groups, i.e., close to normal values. We conclude that, in mechanically ventilated patients, abnormalities in total respiratory system mechanics essentially reflect alterations in lung mechanics. However, abnormalities in chest wall mechanics can be relevant in some COPD patients with a high degree of pulmonary hyperinflation.

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