Respiratory mechanics in mechanically ventilated patients with respiratory failure

Abstract

In 11 mechanically ventilated patients, respiratory mechanics were measured 1) during constant flow inflation and 2) following end-inflation airway occlusion, as proposed in model analysis (J. Appl. Physiol. 58: 1840-1848, 1985. During the latter part of inflation, the relationship between driving pressure and lung volume change was linear, allowing determination of static respiratory elastance (Ers) and resistance (RT). The latter represents in each patient the maximum resistance value that can obtain with the prevailing time constant inhomogeneity. Following occlusion, Ers and RT were also obtained along with RT (min) which represents a minimum, i.e., resistance value that would obtain in the absence of time constant inhomogeneity. A discrepancy between inflation and occlusion Ers and RT was found only in the three patients without positive end-expiratory pressure, and could be attributed to recruitment of lung units during inflation. In all instances Ers and RT were higher than normal. RT(min) was lower in all patients than the corresponding values of RT, indicating that resistance was frequency dependent due to time constant inequalities. Changes in inflation rate did not affect Ers, while RT increased with increasing flow.

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients

“…It is important to emphasize that R rsmax is always greater than R init (DP 1 ). In chronic or acute lung diseases this difference tends to be higher owing to R diff (DP 2 ) elevation (20).…”

“…Recently, several methods have been proposed to assess respiratory mechanical properties in artificially ventilated patients (18,20). Respiratory compliance or elastance and airway resistance can be readily calculated using the flow and pressure transducers incorporated into modern mechanical ventilators, if the raw signals can be connected to an external recording device (21).…”

Bronchodilator delivery with metered-dose inhalers in mechanically-ventilated patients

“…The pressure then declines gradually to reach a plateau after 3-5 s (Pplat). The value of Pinit can be determined by curvilinear back extrapolation of the slope of the latter part of the airway pressure tracing to the time of airway occlusion [51][52][53]. This permits inspiratory resistance to be partitioned into a minimal inspiratory resistance (Rrs,min), which reflects the "ohmic" resistance of the airways and the total or maximal inspiratory resistance (Rrs,max).…”

Contemporary Approaches to the Chronic Obstructive Pulmonary Disease Exacerbations in Emergency Department

“…Bununla beraber, akciğer fonksiyonu ve klinik son durum açısından yararları azdır. 26 Bu nedenle intravenöz metilksantinler (teofilin ya da aminofilin) KOAH atağında ikinci sıra tedavi seçeneğidir ve yalnızca kısa etkili bronkodilatörlerle alınan yanıtın yetersiz olduğu seçilmiş bazı hastalarda kullanılmalıdır. 3 Bu nedenle metilksantinlerin acil serviste kullanımları kısıtlıdır.…”