[Decreased inspiratory time during ventilation of an unprotected airway. Effect on stomach inflation and lung ventilation in a bench model].
BACKGROUND
In an unprotected airway during cardiopulmonary resuscitation, two ventilations with an inspiratory time of 2 s after 15 chest compressions are recommended. Therefore, approximately 30% of the resuscitation attempt is spent on ventilation. Since survival rates did not decrease sharply when minute ventilation levels were relatively low, and uninterrupted chest compressions with a constant rate of approximately 100/min have been shown to be lifesaving, it may be beneficial to decrease the time spent on ventilation and instead, increase the time for chest compressions.


METHODS
In an established bench model of a simulated, unprotected airway with increased airway resistance, we evaluated if inspiratory time can be decreased from 2 to 1 s at different lower oesophageal sphincter pressure (LOSP) levels during ventilation with a bag-valve-mask device.


RESULTS
An inspiratory time of 2 vs. 1 s resulted in significantly lower peak airway pressure, while lung tidal volume was significantly higher at an inspiratory time of 2 s and a LOSP of 5 cm H(2)O (480+/-20 vs. 380+/-30 ml) and 10 cm H(2)O (630+/-50 vs. 440+/-20 ml) and significantly lower at a LOSP of 15 cm H(2)O (470+/-70 vs. 540+/-20 ml). While neither ventilation strategy produced stomach inflation at 20 cm H(2)O LOSP, 1 vs. 2 s inspiratory time produced significantly higher stomach inflation at 15 cm H(2)O LOSP (8+/-11 vs. 0 ml) and significantly lower stomach inflation at a LOSP of 5 cm H(2)O (359+/-31 vs. 375+/-29 ml) and 10 cm H(2)O (28+/-13 vs. 36+/-12 ml) per breath.


CONCLUSIONS
In this model of a simulated, unprotected airway, a reduction of inspiratory time from 2 to 1 s resulted in a significant increase of peak airway pressure, while lung tidal volumes and stomach inflation volumes were statistically different but clinically comparable.
von Goedecke
A
A
Univ.-Klinik für Anaesthesie und Allgemeine Intensivmedizin, Medizinische Universität Innsbruck, Osterreich. achim.von-goedecke@uibk.ac.at
Bowden
K
K
Keller
C
C
Voelckel
W G
WG
Jeske
H-C
HC
Wenzel
V
V
D000403:Airway Resistance; D016887:Cardiopulmonary Resuscitation; D049630:Esophageal Sphincter, Lower / Q000502:physiology; D008953:Models, Anatomic; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology*; D013270:Stomach / Q000502:physiology*; D013990:Tidal Volume; D012122:Ventilators, Mechanical