Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1432-1238
    Keywords: Key words Aged ; Functional residual capacity ; Lung volume measurement ; Mechanical ventilation ; Critical care ; Chronic obstructive pulmonary disease ; Acute lung injury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: Validation of an open-circuit multibreath nitrogen washout technique (MBNW) for measurement of functional residual capacity (FRC). The accuracy of FRC measurement with and without continuous viscosity correction of mass spectrometer delay time (TD) relative to gas flow signal and the influence of baseline FIO2 was investigated. Design: Laboratory study and measurements in mechanically ventilated patients. Setting: Experimental laboratory and anesthesiological intensive care unit of a university hospital. Patients: 16 postoperative patients with normal pulmonary function (NORM), 8 patients with acute lung injury (ALI) and 6 patients with chronic obstructive pulmonary disease (COPD) were included. Interventions: Change of FIO2 from baseline to 1.0. Measurements and main results: FRC was determined by MBNW using continuous viscosity correction of TD (TDdyn), a constant TD based on the viscosity of a calibration gas mixture (TD0) and a constant TD referring to the mean viscosity between onset and end of MBNW (TDmean). Using TDdyn, the mean deviation between 15 measurements of three different lung model FRCs (FRCmeasured) and absolute volumes (FRCmodel) was 0.2 %. For baseline FIO2 ranging from 0.21 to 0.8, the mean deviation between FRCmeasured and FRCmodel was −0.8 %. However, depending on baseline FIO2, the calculation of FRC using TDmean and TD0 increased the mean deviation between FRCmeasured and FRCmodel to 2–4 % and 8–12 %, respectively. In patients (n = 30) the average repeatability coefficient was 6.0 %. FRC determinations with TDmean and TD0 were 0.8–13.3 % and 4.2–23.9 % (median 2.7 % and 8.7 %) smaller than those calculated with TDdyn. Conclusion: A dynamic viscosity correction of TD improves the accuracy of FRC determinations by MBNW considerably, when gas concentrations are measured in a sidestream. If dynamic TD correction cannot be performed, the use of constant TDmean might be suitable. However, in patient measurements this can cause an FRC underestimation of up to 13 %.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-1238
    Keywords: Key words Mechanical ventilation ; Critical care ; Chronic obstructive pulmonary disease ; Patient-ventilator interaction ; Proportional assist ; Pressure support ; Work of breathing physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective: To investigate the breathing pattern and the inspiratory work of breathing (WOBI) in patients with chronic obstructive pulmonary disease (COPD) assisted with proportional assist ventilation (PAV) and conventional pressure support ventilation (PSV). Design: Prospective controlled study. Setting: Intensive care unit of a university hospital. Patients: Thirteen COPD patients being weaned from mechanical ventilation. Interventions: All patients were breathing PSV and two different levels of PAV. Measurements and main results: During PAV (EVITA 2 prototype, Dräger, Germany), the resistance of the endotracheal tube (Ret) was completely compensated while the patients' resistive and elastic loads were compensated for by approximately 80 % and 50 % (PAV80 and PAV50), respectively. PSV was adjusted to match the same mean inspiratory pressure (Pinspmean) as during PAV80. Airway pressure, esophageal pressure and gas flow were measured over a period of 5 min during each mode. Neuromuscular drive (P0.1) was determined by inspiratory occlusions. Mean tidal volume (VT) was not significantly different between the modes. However, the coefficient of variation of VT was 10 ± 4.%, 20 ± 13 % and 15 ± 8 % during PSV, PAV80 and PAV50, respectively. Respiratory rate (RR) and minute ventilation (VE) were significantly lower during PAV80 as compared with both other modes, but the differences did not exceed 10 %. PAV80 and PSV had comparable effects on WOBI and P0.1, whereas WOBI and P0.1 increased during PAV50 compared with both other modes. Conclusion: Mean values of breathing pattern did not differ by a large amount between the investigated modes. However, the higher variability of VT during PAV indicates an increased ability of the patients to control VT in response to alterations in respiratory demand. A reduction in assist during PAV50 resulted in an increase in WOB and indices of patient effort.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...