Nitric oxide and nitrogen dioxide concentrations during in vitro high-frequency oscillatory ventilation

Area of Science:

• Critical care medicine
• Pulmonary medicine
• Biomedical engineering

Background:

• Inhaled nitric oxide (iNO) therapy is used to treat pulmonary hypertension.
• High-frequency oscillatory ventilation (HFOV) is a mode of mechanical ventilation.
• Combining iNO with HFOV requires careful monitoring of gas concentrations.

Purpose of the Study:

• To measure nitric oxide (NO) and nitrogen dioxide (NO2) concentrations.
• To assess these concentrations at various ventilatory settings and sampling sites.
• To evaluate gas concentrations during in vitro inhaled NO and HFOV therapy (iNO-HFOV).

Main Methods:

• Utilized a high-frequency oscillatory ventilator and a test lung.
• Employed a nitric oxide delivery and NO/NO2 monitoring system.
• Systematically varied ventilator frequency, amplitude, and inspired oxygen concentration.
• Measured NO and NO2 concentrations at four distinct sampling sites.

Main Results:

• NO concentration decreased from the inspiratory limb to the test lung bellows.
• NO2 concentration significantly increased from the inspiratory limb to the test lung bellows.
• NOx (NO + NO2) concentrations remained constant.
• Increased ventilator frequency, amplitude, and inspired oxygen significantly altered NO and NO2 levels.
• High NO and oxygen concentrations led to significantly increased NO2 levels at the lung bellows.

Conclusions:

• NO and NO2 concentrations vary by sampling site and are influenced by HFOV settings.
• NO2 concentrations can exceed safe levels during iNO-HFOV with high NO and oxygen.
• Further in vivo studies are needed to confirm these findings in a living model.