Exercising was started on low flow oxygen first after another period of rest, the patients repeated exercising using the high-flow oxygen system, set at 20 L/min and matched to deliver the same FiO 2 as that of low flow oxygen delivery. After a period of rest and baseline recordings, patients were asked to exercise on a cycle ergometer for up to 12 min.
9 These investigators have conducted a prospective, nonrandomized, nonblinded study aimed at comparing the effects of high flow of humidified oxygen to conventional low-flow oxygen delivery at rest and during exercise in ten patients with COPD. The dead space washout also has some beneficial effects in terms of oxygenation as observed by Chatila et al. This study shows that the use of high-flow oxygen via both transtracheal catheter and nasal prongs significantly increased exercise tolerance in COPD patients when compared to low-flow oxygen. Interestingly, there was no significant difference in exercise distance and dyspnea scores with HFTTO as compared with high-flow NP and LFTTO versus low-flow NP. The average distance with HFTTO was 2.5 times greater than with LFTTO, and high-flow NP was 2.38 times higher compared with low-flow NP. The flows were adjusted to provide equivalent oxygen saturation in the respective groups. Two tests were performed with patients receiving low-flow transtracheal oxygen (LFTTO) and high flow transtracheal oxygen (HFTTO), and the other group received low and high flow oxygen by nasal prongs (NP). Each subject underwent a total of four modified progressive treadmill tests in a single-blind randomized fashion on two separate days. For this study, ten COPD patients who were already receiving transtracheal oxygen were recruited. These properties have some clinical benefits for exercise tolerance, dyspnea reduction and better oxygenation.Ī few years ago, Dewan and Bell, 8 studied the clinical impact of high flow oxygen on exercise tolerance and the sensation of dyspnea. This allows the dead space to decrease and increases alveolar ventilation over minute ventilation ratio. The main effect of delivering high flow oxygen directly into the nasopharynx is to wash CO 2 and reduce CO 2 rebreathing. In this article we review the existing evidence of HFNC oxygen therapy in adult patients, its advantages, limitations and the current literature on clinical applications. 4 There are no established guidelines or decision-making pathways to guide use of the HFNC therapy for adults. HFNC has been widely studied in pediatric patients where it is increasingly used, however, the evidence in adults is limited. 3 This therapeutic alternative is mainly characterized by the fact that the patient is given a heated, humidified high flow above its maximum inspiratory flow and we can have increased confidence about the real FiO 2 being delivered to the patient. 1 and 2), the “high flow nasal cannulas”. The gas is heated and humidified through an active heated humidifier and delivered via a single limb heated inspiratory circuit (to avoid heat loss and condensation) to the patient through nasal cannula of large diameter ( Figs. This system basically works with an air oxygen blender allowing from 21% to 100% FiO 2 and generates up to 60 L/min flow rates. We refer to the heated, humidified high flow nasal cannula oxygen therapy (HFNC). Recently growing attention has been paid to an alternative to conventional oxygen therapy. 2 One direct consequence is that the fraction of inspired oxygen (FiO 2) is not constant during conventional oxygen therapy and it is also unknown. 1–3 This means that the proportion of humidified and oxygenated inspired gas can be very small (below 10%) depending on the extent of oxygen dilution with room air. Another drawback of conventional oxygen devices is the difference between the oxygen flow delivered and that the exact amount of the patient's inspiratory flow is not precise it can vary between 30 and 120 L/min during respiratory failure. For example, poor tolerance because of insufficient humidification and heating of the oxygen flow or the fact that the oxygen flow supplied by these devices generally is no more than 15 L/min (the maximum flow delivered by facemasks). However, in some patients there can be serious problems. These limitations do not usually have clinical consequences because the delivered oxygen flow is sufficient to correct the hypoxemia. However the oxygen provided by these conventional systems has several limitations.
For years supplemental oxygen administration provided by different devices (such as nasal prongs, nose masks and face masks), has been the first line treatment for hypoxemic respiratory failure.
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