The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

Nasopharyngeal Oxygen Concentration in Normal Subjects Wearing Low Flow and High Flow Nasal Cannula


Richard B. Wettstein, BS, RRT; Claudia Cantu, BS, CRT; Lizzette Benavidez, BS, CRT; Janna Rodriguez, BS, CRT; Jay I. Peters, MD; David C. Shelledy, PhD, RRT. The University of Texas Health Science Center at San Antonio, Texas.

INTRODUCTION: Nasal Cannulas (NC) are often used to deliver oxygen in the acute and chronic care settings. We measured the pharyngeal oxygen concentrations (OC) delivered by adult NC (Salter Labs REF1600) and high flow NC (Salter Labs REF 1600HF) at 1-6 liters (L) and 6-15 Ls in 10 normal subjects receiving O2 by these two devices.

METHOD:
O2 by NC was initiated at 1 L, with the subject at rest. Gas samples were aspirated from a nasal catheter positioned with the tip in the nasopharynx. Three samples were obtained while the subject was breathing nasally, three with the subject breathing orally, and a final sample was obtained while the subject was hyperventilating. This process was repeated at each L flow.

RESULTS: 
The mean (SD) and range for OC at prescribed flow rates were: 

  Nasopharyngeal Oxygen Concentration (%)
Resting Breathing Hyperventilating
Flow (L/min) Mean (SD) Range Mean (SD) Range
Low Flow Nasal Cannula  1 25.6 (5.1) 20-45 24.0 (3.5) 21-31
2 33.7 (7.7) 22-53 27.7 (3.8) 23-36
3 39.0 (9.5) 27-69 32.2 (5.3) 24-40
4 44.8 (10.8) 22-74 36.8 (7.3) 28-48
5 50.6 (12.5) 32-83 45.2 (11.2) 34-70
6 53.8 (11.4) 36-86 45.3 (8.0) 32-58
High Flow Nasal Cannula 6 54.4 (13.0) 35-89 48.9 (9.7) 34-68
7 57.7 (12.9) 35-85 52.4 (11.3) 39-77
8 58.0 (13.6) 33-87 50.5 (11.1) 32-67
9 63.3 (13.5) 38-89 55.6 (13.4) 39-75
10 65.7 (12.9) 40-88 58.5 (11.3) 38-73
11 67.3 (14.5) 36-91 63.0 (11.6) 40-77
12 68.7 (13.4) 37-93 67.2 (11.5) 48-82
13 70.9 (13.6) 42-96 69.4 (10.3) 55-88
14 73.3 (12.5) 41-89 70.9 (12.8) 46-88
15 75.2 (13.0) 39-98 71.7 (9.0) 55-84


CONCLUSION:
FIO2 delivered by NC varied widely between subjects. The evidence suggests increasing flow does increase FIO2. Clinicians should be aware of device limitations when using nasal cannulae to deliver expected oxygen concentrations.

Departmental Funding

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