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A simple method to reduce the inspiratory oxygen fraction for high pulmonary blood flow patients in an operating room
Author(s) -
ASAKURA AYAKO,
MIYASHITA TETSUYA,
FUJIMOTO JUNICHI,
MORIMURA NAOTO,
KURAHASHI KIYOYASU,
YAMADA YOSHITSUGU
Publication year - 2007
Publication title -
pediatric anesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.704
H-Index - 82
eISSN - 1460-9592
pISSN - 1155-5645
DOI - 10.1111/j.1460-9592.2007.02317.x
Subject(s) - medicine , tidal volume , fraction of inspired oxygen , anesthesia , fresh gas flow , oxygen saturation , heart rate , vascular resistance , ventilation (architecture) , intubation , oxygen , respiratory rate , mechanical ventilation , respiratory system , hemodynamics , blood pressure , sevoflurane , mechanical engineering , engineering , chemistry , organic chemistry
Summary Background: Low inspired oxygen acutely increases pulmonary vascular resistance and decreases pulmonary‐systemic blood flow ratio. We present a simple method to lower inspired oxygen fraction (F I O 2 < 0.21) without supplemental nitrogen, during mechanical ventilation by an anesthesia machine. Methods: After institutional approval, seven healthy adult volunteers and three infants (0–12 month old) scheduled for congenital heart surgery were enrolled in this study. All the infants were diagnosed with congestive heart failure because of high pulmonary blood flow and were thought to benefit from low F I O 2 . The volunteers performed spontaneous ventilation (fresh air flow rate = 10 l·min −1 , tidal volume = 600 ml, frequency = 10 br·min −1 ). The infants were mechanically ventilated with air (fresh air flow rate = 6 l·min −1 , tidal volume = 10 ml·kg −1 , 15 < frequency < 30 br·min −1 to adjust P a CO 2 between 5.8 kPa and 6.5 kPa (45–50 mmHg), after induction of general anesthesia and tracheal intubation. The fresh gas flow rates were determined by the following formula. Fresh gas flow rate = (F I O 2 − F E O 2 ) EVE/(0.21 + F I O 2 − F E O 2 − target F I O 2 ). We recorded F I O 2 every 5 min for 30 min. When arterial oxygen saturation decreased >15%, fresh gas flow rates were increased to adjust F I O 2 to 0.21. Results: In all of the seven volunteers and three infants target F I O 2 was achieved in <10 min. F I O 2 was kept at 0.18 ± 0.01 (SD) by calculated fresh air flow rates. In one infant, SpO 2 decreased >15% 20 min after lowering F I O 2 , we had to discontinue this study, and increase fresh gas flow to ventilate the infant with F I O 2 0.21. In the other two infants, F I O 2 was maintained throughout the study. Conclusions: This simple and convenient method to decrease F I O 2 , has a utility in clinical situations, in which pulmonary vascular resistance is to be increased to improve systemic oxygen delivery in patients with high pulmonary blood flow during cardiac surgery.