Distribution of inhaled nitric oxide during sequential and continuous administration into the inspiratory limb of the ventilator.
OBJECTIVE
The concentrations of nitric oxide (NO) in the ventilatory circuits and the patient's airways were compared between sequential (SQA) and continuous (CTA) administration during inspiratory limb delivery.


METHODS
Prospective controlled study.


METHODS
14-bed Surgical Intensive Care Unit of a teaching University hospital.


METHODS
Eleven patients with acute lung injury on mechanical ventilation and two healthy volunteers.


METHODS
A prototype NO delivery device (Opti-NO) and César ventilator were set up in order to deliver 1, 3 and 6 parts per million (ppm) of NO into the bellows of a lung model in SQA and CTA. Using identical ventilatory and Opti-NO settings, NO was administered to the patients with acute lung injury.


RESULTS
NO concentrations measured from the inspiratory limb [INSP-NOMeas] and the trachea [TRACH-NOMeas] using fast response chemiluminescence were compared between the lung model and the patients using controlled mechanical ventilation with a constant inspiratory flow. INSP-NOMeas were stable during SQA and fluctuated widely during CTA (fluctuation at 6 ppm = 61% in the lung model and 58 +/- 3% in patients). In patients, [TRACH-NOMeas] fluctuated widely during both modes (fluctuation at 6 ppm = 55 +/- 3% during SQA and 54 +/- 5% during CTA). The NO flow requirement was significantly lower during SQA than during CTA (74 +/- 0.5 vs 158 +/- 2.2 ml.min-1 to attain 6 ppm, p = 0.0001). INSP-NOMeas were close to the values predicted using a classical formula only during SQA (bias = -0.1 ppm, precision = +/-1 ppm during SQA; bias = 2.93 ppm and precision = +/-3.54 ppm during CTA). During SQA, INSP-NOMeas varied widely in healthy volunteers on pressure support ventilation.


CONCLUSIONS
CTA did not provide homogenous mixing of NO with the tidal volume and resulted in fluctuating INSP-NOMeas. In contrast, SQA delivered stable and predictable NO concentrations during controlled mechanical ventilation with a constant inspiratory flow and was economical compared to CTA. However, SQA did not provide stable and predictable NO concentrations during pressure support ventilation.
Mourgeon
E
E
Département d'Anesthésie, Hôpital de la Pitié, Paris, France.
Gallart
L
L
Rao
G S
GS
Lu
Q
Q
Law-Koune
J D
JD
Puybasset
L
L
Coriat
P
P
Rouby
J J
JJ
D000704:Analysis of Variance; D001711:Biotransformation; D006801:Humans; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects; D009569:Nitric Oxide / Q000008:administration & dosage* / Q000494:pharmacology; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000628:therapy; D015656:Respiratory Mechanics
D009569:Nitric Oxide