SLOPE OF THE PRESSURE-TIME WAVEFORM PREDICTS RESPIRATORY SYSTEM RESISTANCE AND COMPLIANCE IN MECHANICALLY VENTILATED PATIENTS

CHEST Journal ◽  
2007 ◽  
Vol 132 (4) ◽  
pp. 572A
Author(s):  
Nicole D. Collett ◽  
Gregory A. Schmidt
Keyword(s):  
Respiratory System ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Pressure Time ◽  
Respiratory System Resistance ◽  
Time Waveform ◽  
Ventilated Patients

Poor Correlation between Diaphragm Thickening Fraction and Transdiaphragmatic Pressure in Mechanically Ventilated Patients and Healthy Subjects

2021 ◽  
Author(s):  
Thomas Poulard ◽  
Damien Bachasson ◽  
Quentin Fossé ◽  
Marie-Cécile Niérat ◽  
Jean-Yves Hogrel ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Healthy Subjects ◽  
Healthy Individuals ◽  
Transdiaphragmatic Pressure ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Diaphragm Function ◽  
Pressure Time ◽  
Pressure Time Product ◽  
Ventilated Patients

Background The relationship between the diaphragm thickening fraction and the transdiaphragmatic pressure, the reference method to evaluate the diaphragm function, has not been clearly established. This study investigated the global and intraindividual relationship between the thickening fraction of the diaphragm and the transdiaphragmatic pressure. The authors hypothesized that the diaphragm thickening fraction would be positively and significantly correlated to the transdiaphragmatic pressure, in both healthy participants and ventilated patients. Methods Fourteen healthy individuals and 25 mechanically ventilated patients (enrolled in two previous physiologic investigations) participated in the current study. The zone of apposition of the right hemidiaphragm was imaged simultaneously to transdiaphragmatic pressure recording within different breathing conditions, i.e., external inspiratory threshold loading in healthy individuals and various pressure support settings in patients. A blinded offline breath-by-breath analysis synchronously computed the changes in transdiaphragmatic pressure, the diaphragm pressure-time product, and diaphragm thickening fraction. Global and intraindividual relationships between variables were assessed. Results In healthy subjects, both changes in transdiaphragmatic pressure and diaphragm pressure-time product were moderately correlated to diaphragm thickening fraction (repeated measures correlation = 0.40, P < 0.0001; and repeated measures correlation = 0.38, P < 0.0001, respectively). In mechanically ventilated patients, changes in transdiaphragmatic pressure and thickening fraction were weakly correlated (repeated measures correlation = 0.11, P = 0.008), while diaphragm pressure-time product and thickening fraction were not (repeated measures correlation = 0.04, P = 0.396). Individually, changes in transdiaphragmatic pressure and thickening fraction were significantly correlated in 8 of 14 healthy subjects (ρ = 0.30 to 0.85, all P < 0.05) and in 2 of 25 mechanically ventilated patients (ρ = 0.47 to 0.64, all P < 0.05). Diaphragm pressure-time product and thickening fraction correlated in 8 of 14 healthy subjects (ρ = 0.41 to 0.82, all P < 0.02) and in 2 of 25 mechanically ventilated patients (ρ = 0.63 to 0.66, all P < 0.01). Conclusions Overall, diaphragm function as assessed with transdiaphragmatic pressure was weakly related to diaphragm thickening fraction. The diaphragm thickening fraction should not be used in healthy subjects or ventilated patients when changes in diaphragm function are evaluated. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

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.

scholarly journals Accuracy of chest auscultation in detecting abnormal respiratory mechanics in the immediate postoperative period after cardiac surgery

2019 ◽  
Vol 45 (5) ◽  
Author(s):  
Glaciele Xavier ◽  
César Augusto Melo-Silva ◽  
Carlos Eduardo Ventura Gaio dos Santos ◽  
Veronica Moreira Amado
Keyword(s):  
Cardiac Surgery ◽  
Sensitivity And Specificity ◽  
Respiratory System ◽  
Postoperative Period ◽  
Respiratory Mechanics ◽  
Mechanically Ventilated ◽  
Mechanically Ventilated Patients ◽  
Breath Sounds ◽  
Chest Auscultation ◽  
Ventilated Patients

ABSTRACT Objective: To investigate the accuracy of chest auscultation in detecting abnormal respiratory mechanics. Methods: We evaluated 200 mechanically ventilated patients in the immediate postoperative period after cardiac surgery. We assessed respiratory system mechanics - static compliance of the respiratory system (Cst,rs) and respiratory system resistance (R,rs) - after which two independent examiners, blinded to the respiratory system mechanics data, performed chest auscultation. Results: Neither decreased/abolished breath sounds nor crackles were associated with decreased Cst,rs (≤ 60 mL/cmH2O), regardless of the examiner. The overall accuracy of chest auscultation was 34.0% and 42.0% for examiners A and B, respectively. The sensitivity and specificity of chest auscultation for detecting decreased/abolished breath sounds or crackles were 25.1% and 68.3%, respectively, for examiner A, versus 36.4% and 63.4%, respectively, for examiner B. Based on the judgments made by examiner A, there was a weak association between increased R,rs (≥ 15 cmH2O/L/s) and rhonchi or wheezing (ϕ = 0.31, p < 0.01). The overall accuracy for detecting rhonchi or wheezing was 89.5% and 85.0% for examiners A and B, respectively. The sensitivity and specificity for detecting rhonchi or wheezing were 30.0% and 96.1%, respectively, for examiner A, versus 10.0% and 93.3%, respectively, for examiner B. Conclusions: Chest auscultation does not appear to be an accurate diagnostic method for detecting abnormal respiratory mechanics in mechanically ventilated patients in the immediate postoperative period after cardiac surgery.

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