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Inhaled nitric oxide delivery by anesthesia machines
P Ceccarelli1, L M Bigatello, D Hess
1Department of Anesthesia and Critical Care and the Respiratory Care Services, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
Anesthesia and Analgesia
|January 29, 2000
Summary
Intraoperative inhaled nitric oxide (NO) delivery via anesthesia machines is accurate when fresh gas flow exceeds minute ventilation. Both nitrous oxide (N2O) flowmeters and INOvent devices ensure precise NO concentrations, preventing rebreathing complications.
Area of Science:
- Anesthesiology
- Pulmonary Medicine
- Medical Devices
Background:
- Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used for intraoperative hypertension and hypoxemia.
- Delivery of NO via anesthesia machines can lead to rebreathing, unlike critical care ventilators.
- Accurate NO delivery is crucial for patient safety during surgery.
Purpose of the Study:
- To evaluate the accuracy of two intraoperative inhaled NO delivery methods: a nitrous oxide (N2O) flowmeter and the INOvent device.
- To determine if fresh gas flow (FGF) rate relative to minute ventilation (VE) affects NO delivery accuracy.
- To assess the impact of simulated lung NO uptake on NO delivery accuracy.
Main Methods:
- A lung model was used to simulate intraoperative conditions.
- Two systems, N2O flowmeter and INOvent, were tested for NO delivery.
- Fresh gas flow (FGF) rates were varied (higher and lower than VE) and simulated NO uptake was applied to assess rebreathing.
Main Results:
- Both systems delivered accurate inspired NO concentrations ([NO]) within 10% of the set value when FGF >= VE (6 L/min).
- When FGF < VE, the N2O flowmeter delivered lower [NO] (70% and 40% of set at 4 and 2 L/min, respectively), while INOvent delivered higher [NO] (10% and 23% higher).
- Decreasing NO uptake increased inspired [NO] similarly for both systems across different FGF rates.
Conclusions:
- Intraoperative inhaled NO administration is accurate using either an anesthesia machine's N2O flowmeter or the INOvent device, provided FGF >= VE.
- Guidelines for safe intraoperative NO delivery are provided based on these findings.
- This study confirms reliable NO delivery methods for managing pulmonary hypertension and hypoxemia during surgery.