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Crit Care Med. 2011 Oct;39(10):2283-9. doi: 10.1097/CCM.0b013e3182227fce.

Effect of pressure support on end-expiratory lung volume and lung diffusion for carbon monoxide.

Author information

1
Réanimation Médicale, AP-HP, Centre Hospitalier Albert Chenevier-Henri Mondor, INSERM Unité 955, Université Paris EST, Créteil, France. nathalia.pintodacosta@rdb.aphp.fr

Abstract

OBJECTIVES:

The level of pressure-support ventilation can affect mean airway pressure and potentially lung volume, but its increase is usually associated with a reduced respiratory rate, and the net effects on the gas exchange process and its components, including end-expiratory lung volume, have not been carefully studied. We measured pulmonary conductance for gas exchange based on lung diffusion for carbon monoxide in patients receiving pressure-support ventilation.

DESIGN:

Prospective, randomized, crossover study.

SETTING:

Medical intensive care unit of a university hospital.

PATIENTS:

Sixteen patients mechanically ventilated in pressure-support ventilation mode and free from chronic obstructive pulmonary disease.

INTERVENTIONS:

Two pressure-support ventilation levels (5 cm H2O difference) at the same level of positive end-expiratory pressure.

MEASUREMENTS AND MAIN RESULTS:

End-expiratory lung volume, lung diffusion for carbon monoxide, and SpO2/Fio2 were evaluated. Increasing pressure-support ventilation by 5 cm H2O significantly increased the mean tidal volume from 6.8 to 8.5 mL/kg of predicted body weight and decreased the mean respiratory rate by 6.6 breaths per minute. Although SpO2/Fio2 did not change significantly, there was a slight but significant decrease in lung diffusion for carbon monoxide (average decay rate of 4.5%) at high pressure-support ventilation. The pressure-support ventilation level did not significantly affect end-expiratory lung volume (1737±629 mL at 9.6±2.5 cm H2O pressure-support ventilation level vs. 1749±657 mL at 14.9±2.1 cm H2O pressure-support ventilation level).

CONCLUSIONS:

A 5-cm H2O increase in pressure-support ventilation neither affected end-expiratory lung volume nor increased the pulmonary volume participating in gas exchange. A target tidal volume closer to 6 mL/kg of predicted body weight than to 8 mL/kg during pressure-support ventilation was associated with better gas exchange.

PMID:
21666442
DOI:
10.1097/CCM.0b013e3182227fce
[Indexed for MEDLINE]

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