Effect of decreased inspiratory times on tidal volume. Bench model simulating cardiopulmonary resuscitation.
BACKGROUND
During cardiopulmonary resuscitation (CPR) with a chest compression rate of 60-100/min the time for secure undisturbed ventilation in the chest decompression phase is only 0.3-0.5 s and it is unclear which tidal volumes could be delivered in such a short time.


OBJECTIVE
Attempts were made to assess the tidal volumes that can be insufflated in such a short time window.


METHODS
In a bench model tidal volumes were compared in simulated non-intubated and intubated patients employing an adult self-inflating bag-valve with inspiratory times of 0.25, 0.3, and 0.5 s. Respiratory system compliance values were 60 mL/cmH(2)O being representative for respiratory system conditions shortly after onset of cardiac arrest and 20 mL/cmH(2)O being representative for conditions after prolonged cardiac arrest.


RESULTS
With a respiratory system compliance of 60 mL/cmH(2)O, tidal volumes (mean+/-SD) in non-intubated versus intubated patients were 144+/-13 mL versus 196+/-23 mL in 0.25 s (p<0.01), 178+/-10 versus 270+/-14 mL in 0.3 s (p<0.01), and 310+/-12 mL versus 466+/-20 mL in 0.5 s (p<0.01). With a respiratory system compliance of 20 mL/cmH(2)O, tidal volumes in non-intubated patient versus intubated patients were 128+/-10 mL versus 186+/-20 mL in 0.25 s (p<0.01), 158+/-17 versus 250+/-14 mL in 0.3 s (p<0.01) and 230+/-21 mL versus 395+/-20 mL in 0.5 s (p<0.01).


CONCLUSIONS
Ventilation windows of 0.25, 0.3, and 0.5 s were too short to provide adequate tidal volumes in a simulated non-intubated cardiac arrest patient. In a simulated intubated cardiac arrest patient, ventilation windows of at least 0.5 s were necessary to provide adequate tidal volumes.
Herff
H
H
Department of Anesthesiology and Critical Care Medicine, Innsbruck Medical University, Anichstr. 35, 6020, Innsbruck, Osterreich. holger.herff@i-med.ac.at
Bowden
K
K
Paal
P
P
Mitterlechner
T
T
von Goedecke
A
A
Lindner
K H
KH
Wenzel
V
V
D000328:Adult; D000399:Air Pressure; D016887:Cardiopulmonary Resuscitation; D003198:Computer Simulation; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D007442:Intubation, Intratracheal; D015233:Models, Statistical; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D013990:Tidal Volume / Q000502:physiology*