Chest
Volume 97, Issue 2, February 1990, Pages 430-434
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Are Low Tidal Volumes Safe?

https://doi.org/10.1378/chest.97.2.430Get rights and content

High airway pressure may be injurious to lung parenchyma, but lowering airway pressure using conventional mechanical ventilation necessitates lowering tidal volume (VT). Intubated patients in the surgical intensive care unit (SICU) were randomly assigned to group 1 (VT=12 ml/kg, n=56) or group 2 (VT = 6 ml/kg, n=47). Variables recorded included acute physiology and chronic health evaluation (APACHE II) score, mean peak airway pressure (MPAP), mean PaO2/FIo2, incidence of pulmonary infectious complications (PIC), duration of intubation (DOI), and duration of SICU stay (DOS). Results in the table are means ± SE.

Empty CellGroup 1Group 2p value
APACHE-II score13.3 ±0.813.3 ±0.8.776
MPAP, cm H2O35.1 ±0.226.0 ±1.1<.001
PaO2/FIo2294 ±11260±11.031
PIC, %17.94.3.061
DOI, days3.9 ±0.82.3 ±0.5.066
DOS, days4.6±1.02.7±0.5.064

The incidence of pulmonary infection tended to be lower and DOI and DOS tended to be shorter for nonneurosurgical and noncardiac surgical patients randomized to low VT, suggesting that morbidity may be decreased. The use of low VT was associated with a statistically significant but clinically irrelevant decrease in oxygenation. The routine use of low VT appeared to be safe in a selected population of patients in the SICU.

(Chest 1990; 97:425–29)

Section snippets

METHODS

This study was approved by the Committee on the Protection of Human Subjects in Research at the University of Massachusetts Medical Center, Worcester. Verbal informed consent was obtained from patients or responsible third parties within 24 h of entry into the trial.

All patients requiring mechanical ventilation in the surgical intensive care unit (SICU), except those recovering from cardiac surgery, were eligible for entry into the trial. Excluded after the trial was already under way were 33

RESULTS

One hundred three patients were entered into the trial from October 1987 through February 1988. As shown in Table 1 and Figure 1, the groups were quite comparable in terms of age, sex, and severity of illness (as estimated by APACHE-II score). Age was bimodally distributed in both groups, the younger peak representing primarily patients admitted to the SICU after major trauma. The primary diagnoses necessitating admission to the SICU were similar in both groups (Table 1).

Pulmonary function data

DISCUSSION

The data presented herein support the idea that routine use of low VT is safe in SICU patients. Furthermore, our results suggest that the incidence of pulmonary infections may be decreased by using low VT, although this somewhat surprising observation needs to be confirmed in a larger study designed to specifically address this issue.

Questioning the necessity for moderate to large VT (10 to 15 ml/kg) is somewhat heretical. Why were our results different from those obtained by Bendixen et al?4

ACKNOWLEDGMENTS

We gratefully acknowledge the support of the Surgical Intensive Care Unit nurses at the University of Massachusetts Medical Center. Stephen O. Heard, M.D., reviewed the manuscript and provided us with insightful and informative guidance. Carol Powers retrieved dozens of charts from medical records. Sandy Hinson, Penny Lucier, and Michelle Tremblay assisted in preparation of the manuscript.

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Manuscript received December 16; revision accepted July 13.

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