Measurement of oxygen concentration delivered via nasal cannulae by tracheal sampling. Issue 4 (24th March 2014)

• Record Type: Journal Article
• Authors: O'Reilly Nugent, Andrew; Kelly, Paul T.; Stanton, Josh; Swanney, Maureen P.; Graham, Bruce; Beckert, Lutz
• Is Part Of: Respirology. Volume 19:Issue 4(2014)
• Page Start: 538
• Page End: 543
• Publication Date: 2014-03-24
• Subjects: Respiratory organs -- Diseases -- Periodicals; Respiratory organs -- Periodicals; 612.2
• DOI: 10.1111/resp.12268
• Languages: English
• ISSNs: 1323-7799

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <sec id="resp12268-sec-0001" sec-type="section"> <title>Background and objective</title> <p>Oxygen is used in many clinical scenarios, however the variable performance of nasal cannulae makes determining the precise fraction of inspired oxygen (FiO<sub>2</sub>) difficult. We developed a novel method for measurement of the tracheal FiO<sub>2</sub> using a catheter placed via bronchoscopy. We investigate the effects of oxygen delivery, respiratory rate, mouth position and estimated minute ventilation (<italic>V<sub>E</sub></italic>) on the FiO<sub>2</sub> delivered by nasal cannulae.</p> </sec> <sec id="resp12268-sec-0002" sec-type="section"> <title>Methods</title> <p>The catheter was placed in 20 subjects. Tracheal gas concentrations were analysed during six 5‐min treatments controlling for oxygen delivery rate, respiratory rate and mouth position. Ventilation was monitored with respiratory inductive plethysmography (RIP). The FiO<sub>2</sub> delivered by nasal cannulae was compared between treatments, and we investigated the relationships among the FiO<sub>2</sub>, alveolar partial pressure of oxygen (P<sub>A</sub>O<sub>2</sub>) and <italic>V<sub>E</sub></italic>.</p> </sec> <sec id="resp12268-sec-0003" sec-type="section"> <title>Results</title> <p>The FiO<sub>2</sub> increased by 0.038/L/min of oxygen. Respiratory rate had a significant effect on the FiO<sub>2</sub>. A normal respiratory rate of 15 breaths/min and oxygen supplementation via nasal cannula at 2 L/min resulted in an FiO<sub>2</sub> of 0.296; however, FiO<sub>2</sub> decreased by 0.012 at 20 breaths/min and 0.004 at 10 breaths/min. The mean FiO<sub>2</sub> decreased by 0.024 with the mouth open. The FiO<sub>2</sub> and P<sub>A</sub>O<sub>2</sub> were observed to decrease with increasing <italic>V<sub>E</sub></italic>.</p> </sec> <sec id="resp12268-sec-0004" sec-type="section"> <title>Conclusions</title> <p>Continuous measurement of the FiO<sub>2</sub> using a transtracheal catheter provides detailed insight into inspiratory changes of the FiO<sub>2</sub> delivered by nasal cannulae. Our study confirms that respiratory rate, <italic>V<sub>E</sub></italic> and mouth position significantly influence the inspired oxygen concentration. These parameters should be accounted for when prescribing oxygen.</p> </sec> </abstract>