Hypotension Secondary to Air Trapping Treated with Expiratory Flow Retard

Weng, J. T.; Smith, Debbie E.; Graybar, Gwendolyn B.; Kirby, Robert R.

doi:10.1097/00000542-198404000-00012

Cited by 17 publications

(8 citation statements)

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“…During this critical period, dynamic overinflation and air trapping are major challenges for clinicians (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). Besides the associated hemodynamic impairment, patients with obstructive pulmonary disease frequently experience dyssynchrony during assisted ventilation and difficulty triggering mechanical breaths (2)(3)(4)6,9,10,13,14).…”

Section: Introductionmentioning

confidence: 99%

“…The explanation for this response is based on the dynamic flow-limitation theory and its hydraulic analogue: the waterfall model (15)(16)(17). Contrary to these recognized benefits of external-PEEP during assisted ventilation, there are only anecdotal data suggesting benefit from external-PEEP during controlled mechanical ventilation of patients with obstructive lung disease (10,11,18,19). Qvist et al (18) reported two patients with severe asthma in whom external-PEEP levels of 17-25 cm H 2 O during controlled ventilation resulted in reduced peak airway pressures, improvement of blood pressure, and returning of the diaphragm to normal position These effects were interpreted as paradoxic lung deflation promoted by PEEP.…”

Section: Introductionmentioning

confidence: 99%

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Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation*

Caramez

Borges

Tucci

et al. 2005

Critical Care Medicine

116

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Objective-To reevaluate the clinical impact of external positive end-expiratory pressure (external-PEEP) application in patients with severe airway obstruction during controlled mechanical ventilation. The controversial occurrence of a paradoxic lung deflation promoted by PEEP was scrutinized.Design-External-PEEP was applied stepwise (2 cm H 2 O, 5-min steps) from zero-PEEP to 150% of intrinsic-PEEP in patients already submitted to ventilatory settings minimizing overinflation. Two commonly used frequencies during permissive hypercapnia (6 and 9/min), combined with two different tidal volumes (V T : 6 and 9 mL/kg), were tested. Setting-A hospital intensive care unit.Patients-Eight patients were enrolled after confirmation of an obstructive lung disease (inspiratory resistance, >20 cm H 2 O/L per sec) and the presence of intrinsic-PEEP (≥5 cm H 2 O) despite the use of very low minute ventilation.Interventions-All patients were continuously monitored for intra-arterial blood gas values, cardiac output, lung mechanics, and lung volume with plethysmography. Measurements and MainResults-Three different responses to external-PEEP were observed, which were independent of ventilatory settings. In the biphasic response, isovolume-expiratory flows and lung volumes remained constant during progressive PEEP steps until a threshold, beyond which overinflation ensued. In the classic overinflation response, any increment of external-PEEP caused a decrease in isovolume-expiratory flows, with evident overinflation. In the paradoxic response, a drop in functional residual capacity during external-PEEP application (when compared to zeroexternal-PEEP) was commonly accompanied by decreased plateau pressures and total-PEEP, with increased isovolume-expiratory flows. The paradoxic response was observed in five of the eight patients (three with asthma and two with chronic obstructive pulmonary disease) during at least one ventilator pattern.Conclusions-External-PEEP application may relieve overinflation in selected patients with airway obstruction during controlled mechanical ventilation. No a priori information about disease, mechanics, or ventilatory settings was predictive of the response. An empirical PEEP trial investigating plateau pressure response in these patients appears to be a reasonable strategy with minimal side effects.* See also p. 1652.The authors have no financial interest to disclose. -12). Besides the associated hemodynamic impairment, patients with obstructive pulmonary disease frequently experience dyssynchrony during assisted ventilation and difficulty triggering mechanical breaths (2)(3)(4)6,9,10,13,14). This difficulty is caused by the large difference between alveolar and upstream pressures at end-expiration (intrinsic positive end-expiratory pressure, or intrinsic-PEEP), imposing an increased load on inspiratory muscles. NIH Public AccessUnder such conditions, external-PEEP application minimizes pressure differences across obstructed airways, reducing the effort to trigger the ventilator (2-4,9,10). ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Paradoxical responses to positive end-expiratory pressure in patients with airway obstruction during controlled ventilation*

Caramez

Borges

Tucci

et al. 2005

Critical Care Medicine

116

View full text Add to dashboard Cite

show abstract

“…This only occurs if the intrapleural pressure is positive, as during forced expiration, or in case of marked hyperinflation during passive expiration (21, 22). Airway compression can be explained on the basis of the equal pressure point (EPP) concept (23–25). Alveolar pressure (Palv) is the sum of elastic recoil pressure (Pell) and pleural pressure (Ppl) (23, 25).…”

Section: Discussionmentioning

confidence: 99%

“…Airway compression can be explained on the basis of the equal pressure point (EPP) concept (23–25). Alveolar pressure (Palv) is the sum of elastic recoil pressure (Pell) and pleural pressure (Ppl) (23, 25). During expiration a pressure gradient exists within the airways; in the bronchioles pressures are almost equal to alveolar pressure and decrease to atmospheric pressure at the mouth.…”

Section: Discussionmentioning

confidence: 99%

“…A way to decrease iPEEP and to improve gas‐exchange should be to counteract flow limitation in patients with COPD. It has been suggested that increasing the airway opening pressure will move the EPP more downstream to the non‐collapsible airways (3, 25). To achieve this, some spontaneously breathing COPD patients purse their lips, which has been suggested to decrease airways compression.…”

Section: Discussionmentioning

confidence: 99%

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