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Pulmonary uptake and modes of administration of inhaled nitric oxide in mechanically-ventilated patients.

Puybasset L, Rouby JJ - Crit Care (1998)

View Article: PubMed Central - HTML - PubMed

Affiliation: Surgical Intensive Care Unit, Department of Anesthesiology, La Pitié-Salpêtrière Hospital, 47-89, Boulevard de I'Hôpital, 75013 Paris, France. louis.puybasset@psl.ap-hop-paris.fr

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Inhaled nitric oxide (NO) is a selective pulmonary vasodilator which reduces pulmonary artery pressure and increases arterial oxygenation in patients with adult respiratory distress syndrome (ARDS)... Despite these beneficial effects, inhaled NO has not yet been shown to improve outcome... During artificial ventilation, it can be administered in the downstream of the ventilator into the inspiratory limb of the ventilatory circuit, or can be mixed with oxygen and nitrogen in the upstream part of the system... There is no risk of overdose due to momentary interruption of ventilation during tracheal suctioning or acute reduction of minute ventilation when the ventilator is in partial-support mode... Similarly, an accidental interruption of the power supply to the ventilator does not result in an overdose after the restoration of power... It is necessary to evaluate each system before its clinical usage and to monitor the actual concentrations of NO delivered after the absorber... Another potential problem is that the passage of NO through a humidification chamber results in the dissolution of the gas in water with the formation of nitric acid (a phenomenon that does not occur with heat moisture exchangers) and in a decrease in the NO concentration actually delivered to the patient... The magnitude of the bolus effect is also inversely related to the NO concentration in the cylinder... Changing from a 22.5 ppm cylinder to a 900 ppm cylinder results in a 50-fold reduction in the volume of the bolus... Continuous monitoring of the fluctuation of tracheal NO concentrations in a given patient could thus be a reliable 'marker' of pulmonary function during the course of ARDS... A display of tracheal NO concentration on the monitor screen is available on the latest chemiluminescence apparatus (EVA 4000, Sérès, Aix-en-Provence, France) giving the possibility of continuously monitoring the fluctuations in tracheal NO concentration as an index of 'pulmonary function' during the course of ARDS... In 1998, inhaled NO should be administered in such a way that stable and predictable concentrations in the inspiratory limb are obtained... It can, therefore, be considered as an index of ventilatory perfusion ratio mismatch, and can be continuously monitored in ARDS... In contrast, the continuous delivery of NO in the inspiratory limb leads to unpredictable and fluctuating concentrations of NO and must be considered as an unsafe mode of administration, unless fast-response chemiluminescence apparatus is used for monitoring.

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Nitric oxide concentrations recorded from the inspiratory limb and trachea in a lung model and a patient on artificial ventilation during continuous administration. Panel A represents the variation in NO concentration in the inspiratory limb of the lung model; panel B shows the variations in NO concentration at simulated tracheal level in the lung model; panel C shows the variations of NO concentration in the inspiratory limb in the ventilated patient; panel D shows the variations of NO concentration in the trachea of the ventilated patient. In panels A and B the lower trace represents the respiratory gas flow. In panels C and D the two lower traces represent expired CO2 curves (end-tidal CO2 is equal to 25 mmHg) and respiratory gas flow. Nitric oxide concentrations were measured by fast-response chemiluminescence apparatus (NOX 4000 Sérès, Aix-en-Provence, France). The time delay of the apparatus was 2.4 s. Accordingly, the beginning of inspiration and expiration (represented by arrows) is shifted 2.4 s to the right compared to the respiratory flow recording. Published with permission [10].
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Figure 3: Nitric oxide concentrations recorded from the inspiratory limb and trachea in a lung model and a patient on artificial ventilation during continuous administration. Panel A represents the variation in NO concentration in the inspiratory limb of the lung model; panel B shows the variations in NO concentration at simulated tracheal level in the lung model; panel C shows the variations of NO concentration in the inspiratory limb in the ventilated patient; panel D shows the variations of NO concentration in the trachea of the ventilated patient. In panels A and B the lower trace represents the respiratory gas flow. In panels C and D the two lower traces represent expired CO2 curves (end-tidal CO2 is equal to 25 mmHg) and respiratory gas flow. Nitric oxide concentrations were measured by fast-response chemiluminescence apparatus (NOX 4000 Sérès, Aix-en-Provence, France). The time delay of the apparatus was 2.4 s. Accordingly, the beginning of inspiration and expiration (represented by arrows) is shifted 2.4 s to the right compared to the respiratory flow recording. Published with permission [10].

Mentions: As shown in Fig 3, the concentration of NO fluctuates in the inspiratory limb. This fluctuation, which can be detected only by fast-response chemiluminescence apparatus results from the passage of the bolus past the sampling site for the inspired gas. As recently suggested, even fast-response chemiluminescence may underestimate rapid changes in NO concentrations [11]. If the NO bolus is small and moves with a high velocity, chemiluminescence apparatus with a response time between 0.5 and 1.5 s may be unable to provide accurate measurements of the true peak NO concentration. By using CO2 as a tracer gas and infrared capnography with a response time of 350 ms, Stenqvist et al demonstrated that fast-response chemiluminescence (response time of 1.5 s) underestimates true peak NO concentrations when sampling at the Y piece during the inspiratory phase [11]. If this fluctuation is measured at different sites in the inspiratory limb, the peak concentration and its phase in relation to the respiratory cycle vary significantly. As previously mentioned, this is because the phase and the peak of the fluctuation are influenced by the progressive mixing of the bolus with the inspired gas, and depend on the location of the sampling site in relation to the position of the bolus at the end of inspiration. As a result of the bolus, peak concentrations of NO are created within the inspiratory circuit which can generate high levels of NO2 [2]. It is likely that for the same mean intratracheal NO concentration, continuous administration generates higher NO2 levels than sequential administration where the inspired NO concentrations are stable.


Pulmonary uptake and modes of administration of inhaled nitric oxide in mechanically-ventilated patients.

Puybasset L, Rouby JJ - Crit Care (1998)

Nitric oxide concentrations recorded from the inspiratory limb and trachea in a lung model and a patient on artificial ventilation during continuous administration. Panel A represents the variation in NO concentration in the inspiratory limb of the lung model; panel B shows the variations in NO concentration at simulated tracheal level in the lung model; panel C shows the variations of NO concentration in the inspiratory limb in the ventilated patient; panel D shows the variations of NO concentration in the trachea of the ventilated patient. In panels A and B the lower trace represents the respiratory gas flow. In panels C and D the two lower traces represent expired CO2 curves (end-tidal CO2 is equal to 25 mmHg) and respiratory gas flow. Nitric oxide concentrations were measured by fast-response chemiluminescence apparatus (NOX 4000 Sérès, Aix-en-Provence, France). The time delay of the apparatus was 2.4 s. Accordingly, the beginning of inspiration and expiration (represented by arrows) is shifted 2.4 s to the right compared to the respiratory flow recording. Published with permission [10].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC137224&req=5

Figure 3: Nitric oxide concentrations recorded from the inspiratory limb and trachea in a lung model and a patient on artificial ventilation during continuous administration. Panel A represents the variation in NO concentration in the inspiratory limb of the lung model; panel B shows the variations in NO concentration at simulated tracheal level in the lung model; panel C shows the variations of NO concentration in the inspiratory limb in the ventilated patient; panel D shows the variations of NO concentration in the trachea of the ventilated patient. In panels A and B the lower trace represents the respiratory gas flow. In panels C and D the two lower traces represent expired CO2 curves (end-tidal CO2 is equal to 25 mmHg) and respiratory gas flow. Nitric oxide concentrations were measured by fast-response chemiluminescence apparatus (NOX 4000 Sérès, Aix-en-Provence, France). The time delay of the apparatus was 2.4 s. Accordingly, the beginning of inspiration and expiration (represented by arrows) is shifted 2.4 s to the right compared to the respiratory flow recording. Published with permission [10].
Mentions: As shown in Fig 3, the concentration of NO fluctuates in the inspiratory limb. This fluctuation, which can be detected only by fast-response chemiluminescence apparatus results from the passage of the bolus past the sampling site for the inspired gas. As recently suggested, even fast-response chemiluminescence may underestimate rapid changes in NO concentrations [11]. If the NO bolus is small and moves with a high velocity, chemiluminescence apparatus with a response time between 0.5 and 1.5 s may be unable to provide accurate measurements of the true peak NO concentration. By using CO2 as a tracer gas and infrared capnography with a response time of 350 ms, Stenqvist et al demonstrated that fast-response chemiluminescence (response time of 1.5 s) underestimates true peak NO concentrations when sampling at the Y piece during the inspiratory phase [11]. If this fluctuation is measured at different sites in the inspiratory limb, the peak concentration and its phase in relation to the respiratory cycle vary significantly. As previously mentioned, this is because the phase and the peak of the fluctuation are influenced by the progressive mixing of the bolus with the inspired gas, and depend on the location of the sampling site in relation to the position of the bolus at the end of inspiration. As a result of the bolus, peak concentrations of NO are created within the inspiratory circuit which can generate high levels of NO2 [2]. It is likely that for the same mean intratracheal NO concentration, continuous administration generates higher NO2 levels than sequential administration where the inspired NO concentrations are stable.

View Article: PubMed Central - HTML - PubMed

Affiliation: Surgical Intensive Care Unit, Department of Anesthesiology, La Pitié-Salpêtrière Hospital, 47-89, Boulevard de I'Hôpital, 75013 Paris, France. louis.puybasset@psl.ap-hop-paris.fr

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Please rate it.

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator which reduces pulmonary artery pressure and increases arterial oxygenation in patients with adult respiratory distress syndrome (ARDS)... Despite these beneficial effects, inhaled NO has not yet been shown to improve outcome... During artificial ventilation, it can be administered in the downstream of the ventilator into the inspiratory limb of the ventilatory circuit, or can be mixed with oxygen and nitrogen in the upstream part of the system... There is no risk of overdose due to momentary interruption of ventilation during tracheal suctioning or acute reduction of minute ventilation when the ventilator is in partial-support mode... Similarly, an accidental interruption of the power supply to the ventilator does not result in an overdose after the restoration of power... It is necessary to evaluate each system before its clinical usage and to monitor the actual concentrations of NO delivered after the absorber... Another potential problem is that the passage of NO through a humidification chamber results in the dissolution of the gas in water with the formation of nitric acid (a phenomenon that does not occur with heat moisture exchangers) and in a decrease in the NO concentration actually delivered to the patient... The magnitude of the bolus effect is also inversely related to the NO concentration in the cylinder... Changing from a 22.5 ppm cylinder to a 900 ppm cylinder results in a 50-fold reduction in the volume of the bolus... Continuous monitoring of the fluctuation of tracheal NO concentrations in a given patient could thus be a reliable 'marker' of pulmonary function during the course of ARDS... A display of tracheal NO concentration on the monitor screen is available on the latest chemiluminescence apparatus (EVA 4000, Sérès, Aix-en-Provence, France) giving the possibility of continuously monitoring the fluctuations in tracheal NO concentration as an index of 'pulmonary function' during the course of ARDS... In 1998, inhaled NO should be administered in such a way that stable and predictable concentrations in the inspiratory limb are obtained... It can, therefore, be considered as an index of ventilatory perfusion ratio mismatch, and can be continuously monitored in ARDS... In contrast, the continuous delivery of NO in the inspiratory limb leads to unpredictable and fluctuating concentrations of NO and must be considered as an unsafe mode of administration, unless fast-response chemiluminescence apparatus is used for monitoring.

No MeSH data available.


Related in: MedlinePlus