The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

Incidenceof respiratory distress or patient-ventilator dyssynchrony during low VTventilation in patients with acute lung injury (ALI)

rhKallet, MS RRT, JA Alonso RRT, L Martin RRT, M Eisner MD, JM Luce MD. NHLBI ARDS Clinical Trials Networkat San Francisco General Hospital (SFGH)

Background: Theincidence of respiratory distress and/or patient-ventilator dyssynchrony (distress/dyssynchrony)during low VT ventilation is unknown. We gathered preliminary informationby reviewing the medical records of all 43 patients enrolled into the ARDS Networklow VT study at SFGH and randomized to low VT (6mL/kg)or traditional VT (12 mL/kg) ventilation.

Methods: Protocol-directedventilator adjustments were made with the intention of minimizing inspiratoryflow rate yI and inspiratory-phase dyssynchrony. The ventilator flowsheets and nursing notes were reviewed retrospectively for all documented incidencesof distress/dyssynchrony during the first 24 h of protocol management. Datawas expressed as mean (± standard deviation) and comparisons were made usingMann-Whitney tests. The relative risk for distress/ dyssynchrony was assessedby two-sided Fisher?s Exact test. Alpha was set at 0.05.

Results: Distress/dyssynchrony was documented in 67% (14/21) of the patients in the low VTgroup, and in 36% (8/22) of the patients randomized to traditional VT.The risk of developing distress/dyssynchrony during low VT ventilationwas 1.83, but failed to achieve statistical significance (p = 0.069).

VariableLow VTTraditionalVTp
VT6.8 ± 0.9mL/kg 11.8 ± 1.1mL/kg< 0.0001

yE

16.0± 3.3L/min12.7 ± 2.9L/min 10.001

yI

86.1 ±20.1L/min 65.1 ± 20.1L/min0.0017

Set f

29.2 ± 5.314.3 ± 4.8 <0.0001

Assist f >set f

1.2 ± 2.40.6 ± 0.9 0.46

Psens

-1.2 ± 0.5cmH2O -1.4 ± 0.5cmH2O0.10

pH

7.35 ± .077.39 ± .060.09

PaCO2

36.1 ± 7.4mm Hg35.7 ± 6.6mm Hg 0.80

PaO2

79.9 ± 13.5mm Hg91.3 ± 22.9mm Hg0.09

BE

-5.0 ± 5.9mEq/dL -3.3 ± 4.9mEq/dL 0.33

 

Conclusion: Therewas a trend toward increased distress/dyssynchrony during low VTventilation despite a high peak yI, low trigger sensitivity(Psens) and a set f close to total f. This implies that traditionalventilator adjustments to optimize patient comfort may not be sufficient duringlow VT ventilation. However, the distress/dyssynchrony trend maybe influenced by the fact that patients in the low VT group alsohad a higher minute ventilation yE demand and a trend towards a lowerpH, which may suggest more severe illness.

NIH R01-HL51856

OF-01-112

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