The clinical effect of oxygen supply by different lengths of nasal cannula from oxygen concentrator

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The clinical effect of oxygen supply by different lengths of nasal cannula from oxygen concentrator


Author: Chan, Choi-wah
Title: The clinical effect of oxygen supply by different lengths of nasal cannula from oxygen concentrator
Degree: M.Sc.
Year: 1998
Subject: Oxygen therapy
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Rehabilitation Sciences
Pages: xi, 107 leaves : ill. ; 30 cm
Language: English
InnoPac Record:
Abstract: Long nasal cannulae can increase physical boundary of patients receiving domiciliary oxygen therapy. The tubing may be coiled when the patient is near to the oxygen concentrator or hanged up on the wall to prevent tripping hazard. Some patients may complain of a decrease in gas flow when long nasal cannula is attached. A study was carried out to address some of these technical and clinical issues. Oxygen flow rate, concentration and outlet pressure through 2.1 to 12 meters (m) nasal cannulae were measured with a Timeter RT-200 Calibration Analyzer and an oxygen analyzer. The effectiveness of kink-resistant tubing was investigated by measuring oxygen output from a bent tubing. Nasal cannulae were arranged: straight, coiled and hanging 2.1 m from the floor. Two main types of oxygen concentrators fitted with adjustable restrictor (Mark 5) and compensated flowmeter (Alliance and Companion 492a) were studied. Results showed that the concentrators were reliable means of oxygen supply, providing flow rate within 10% of accuracy and higher than 85% oxygen concentration at allowed flow rates with nasal cannulae from 2.1 to 12 m long. There was no significant difference in the flow rate (p = 0.98) and oxygen concentration (p = 0.99) for nasal cannulae from 2.1 to 12 m long. The three arrangements of nasal cannula did not affect the flow rate (p = 0.99). The distal pressure measured before the bifurcation of head band of the nasal cannula from these 3 different brands of oxygen concentrators and the wall oxygen did not show significant difference (p = 0.49). There was barely any flow from a bent round bore tubing, while some flow (0.65 to 2.05 L/min) passed through a bent kink-resistant tubing when the proximal flow was set at 1-5 L/min. The clinical performance of Mark 5 was studied with 30 patients. They were hypoxic when breathing room air and required 1 L/min oxygen through nasal cannula. They received oxygen therapy from the oxygen concentrator through nasal cannula (2.1 m straight, 6 m straight and 12 m coiled) for 15 minutes. The patient's level of shortness of breath and anxiety were measured by visual analogue scales. The result showed that Mark 5, oxygen concentrator was as effective oxygen supply as wall oxygen with same level of oxygenation. Patient's mean pulse rate, mean respiratory rate, mean anxiety level and mean level of shortness of breath did not show statistical difference (p = 0.87, 0.70, 0.95 & 0.57 respectively) with oxygen concentrator, wall oxygen and room air. Oxygen concentrator installed with compensated flowmeter was better than adjustable flow restrictor in overcoming back pressure, maintaining more stable flow rate. Mark 5 oxygen concentrator provided quite stable oxygen supply at 1-3 L/min. At a flow rate of 4 or 5 L/min, the drop in flow rate was proportional to the amount of resistance encountered. Therefore long (12 m) nasal cannula is not recommended at these flow rates. Further research is required to address the clinical effectiveness of concentrator fitted with flow restrictor at 4 or 5 L/min flow rate with long nasal cannula.

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