Effects of thoraco-pelvic supports during prone position in patients with acute lung injury/acute respiratory distress syndrome: a physiological study.
BACKGROUND
This study sought to assess whether the use of thoraco-pelvic supports during prone positioning in patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) improves, deteriorates or leaves unmodified gas exchange, hemodynamics and respiratory mechanics.


METHODS
We studied 11 patients with ALI/ARDS, sedated and paralyzed, mechanically ventilated in volume control ventilation. Prone positioning with or without thoraco-pelvic supports was applied in a random sequence and maintained for a 1-hour period without changing the ventilation setting. In four healthy subjects the pressures between the body and the contact surface were measured with and without thoraco-pelvic supports. Oxygenation variables (arterial and central venous), physiologic dead space, end-expiratory lung volume (helium dilution technique) and respiratory mechanics (partitioned between lung and chest wall) were measured after 60 minutes in each condition.


RESULTS
With thoraco-pelvic supports, the contact pressures almost doubled in comparison with those measured without supports (19.1 +/- 15.2 versus 10.8 +/- 7.0 cmH2O, p < or = 0.05; means +/- SD). The oxygenation-related variables were not different in the prone position, with or without thoraco-pelvic supports; neither were the CO2-related variables. The lung volumes were similar in the prone position with and without thoraco-pelvic supports. The use of thoraco-pelvic supports, however, did lead to a significant decrease in chest wall compliance from 158.1 +/- 77.8 to 102.5 +/- 38.0 ml/cmH2O and a significantly increased pleural pressure from 4.3 +/- 1.9 to 6.1 +/- 1.8 cmH2O, in comparison with the prone position without supports. Moreover, when thoraco-pelvic supports were added, heart rate increased significantly from 82.1 +/- 17.9 to 86.7 +/- 16.7 beats/minute and stroke volume index decreased significantly from 37.8 +/- 6.8 to 34.9 +/- 5.4 ml/m2. The increase in pleural pressure change was associated with a significant increase in heart rate (p = 0.0003) and decrease in stroke volume index (p = 0.0241).


CONCLUSIONS
The application of thoraco-pelvic supports decreases chest wall compliance, increases pleural pressure and slightly deteriorates hemodynamics without any advantage in gas exchange. Consequently, we stopped their use in clinical practice.
Chiumello
Davide
D
Dipartimento di Anestesia e Rianimazione, Fondazione IRCCS-Ospedale Maggiore Policlinico, Mangiagalli, Regina Elena, Via F, Sforza 35, 20122 Milan, Italy.
Cressoni
Massimo
M
Racagni
Milena
M
Landi
Laura
L
Li Bassi
Gianluigi
G
Polli
Federico
F
Carlesso
Eleonora
E
Gattinoni
Luciano
L
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000502:physiology*; D011312:Pressure; D003668:Pressure Ulcer / Q000209:etiology; D016684:Prone Position / Q000502:physiology*; D012121:Respiration, Artificial / Q000379:methods; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology; D013909:Thorax / Q000502:physiology*