Method of delivering constant nitric oxide concentrations during full and partial ventilatory support

Area of Science:

• Critical care medicine
• Respiratory physiology
• Biomedical engineering

Background:

• Nitric oxide (NO) therapy is used in respiratory support.
• Accurate delivery of NO during mechanical ventilation is crucial for patient safety and treatment efficacy.
• Understanding delivery methods is essential for optimizing NO therapy.

Purpose of the Study:

• To evaluate the precision and safety of NO administration during full and partial ventilatory support.
• To compare two different NO delivery systems: a servo ventilator and a constant flow system.
• To assess the formation of byproducts like nitrogen dioxide (NO2) and nitrous and nitric acid (HNOx).

Main Methods:

• NO was administered using a microprocessor-controlled servo ventilator and a constant flow system.
• Measurements were taken in a respiratory system model under various ventilatory support modes.
• Quantification of NO, NO2, and HNOx was performed using chemiluminescence analysis.

Main Results:

• The servo ventilator system precisely controlled NO concentrations during both full and partial ventilatory support.
• The constant flow system showed significant variability (3.6%–44.1%) in NO delivery during partial support due to irregular inspiratory flow.
• No NO2 was detected; however, small amounts of HNOx were observed under specific conditions (80 ppm NO, humid, 37°C, 90% O2).

Conclusions:

• Electronically controlled servo valve systems ensure accurate NO delivery during mechanical ventilation.
• Constant flow administration poses risks of inaccurate NO dosing, particularly with spontaneous breathing.
• Potential for HNOx formation exists at high NO and oxygen concentrations in humid conditions.