Effects of tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury and acute respiratory distress syndrome.
OBJECTIVE
To assess the effects of step-changes in tidal volume on work of breathing during lung-protective ventilation in patients with acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS).


METHODS
Prospective, nonconsecutive patients with ALI/ARDS.


METHODS
Adult surgical, trauma, and medical intensive care units at a major inner-city, university-affiliated hospital.


METHODS
Ten patients with ALI/ARDS managed clinically with lung-protective ventilation.


METHODS
Five patients were ventilated at a progressively smaller tidal volume in 1 mL/kg steps between 8 and 5 mL/kg; five other patients were ventilated at a progressively larger tidal volume from 5 to 8 mL/kg. The volume mode was used with a flow rate of 75 L/min. Minute ventilation was maintained constant at each tidal volume setting. Afterward, patients were placed on continuous positive airway pressure for 1-2 mins to measure their spontaneous tidal volume.


RESULTS
Work of breathing and other variables were measured with a pulmonary mechanics monitor (Bicore CP-100). Work of breathing progressively increased (0.86 +/- 0.32, 1.05 +/- 0.40, 1.22 +/- 0.36, and 1.57 +/- 0.43 J/L) at a tidal volume of 8, 7, 6, and 5 mL/kg, respectively. In nine of ten patients there was a strong negative correlation between work of breathing and the ventilator-to-patient tidal volume difference (R = -.75 to -.998).


CONCLUSIONS
: The ventilator-delivered tidal volume exerts an independent influence on work of breathing during lung-protective ventilation in patients with ALI/ARDS. Patient work of breathing is inversely related to the difference between the ventilator-delivered tidal volume and patient-generated tidal volume during a brief trial of unassisted breathing.
Kallet
Richard H
RH
Critical Care Division, Department of Anesthesia, University of California, San Francisco at San Francisco General Hospital, San Francisco, CA 94110, USA. richkallet@earthlink.net
Campbell
Andre R
AR
Dicker
Rochelle A
RA
Katz
Jeffrey A
JA
Mackersie
Robert C
RC
D000208:Acute Disease; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016638:Critical Illness; D005260:Female; D005500:Follow-Up Studies; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011336:Probability; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods; D012128:Respiratory Distress Syndrome / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D012131:Respiratory Insufficiency / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D018570:Risk Assessment; D015996:Survival Rate; D013990:Tidal Volume / Q000502:physiology*; D016896:Treatment Outcome; D014939:Work of Breathing / Q000502:physiology*