Effect of low flow and high flow oxygen delivery on exercise tolerance and sensation of dyspnea. A study comparing the transtracheal catheter and nasal prongs by Dewan NA & Bell CW (Chest. 1994 105:1)

Dewan and Bell describe the effectiveness of high flow nasal cannula in maintaining oxygenation and work tolerance. This paper shows that high flow oxygen delivery by nasal cannula is more effective at maintaining blood oxygen saturation and work performance than low flow oxygen cannula. Furthermore, the data indicate that high flow nasal cannula therapy is similar in efficacy to transtracheal catheters, which are intended to attenuate the effects of anatomical dead space on breathing efficiency. This paper therefore supports the proposed mechanism of action for high flow nasal cannula related to dead space washout.

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http://chestjournal.org/cgi/content/abstract/105/4/1061

Heated humidified high-flow nasal cannula: use and a neonatal early extubation protocol by Holleman-Duray, Loyola University, D, Kaupie, D, & Weiss, MG.(Journal of Perinatol 2007: 27, 776-81)

Holleman-Duray et al describe how the use of high flow therapy (HFT; Vapotherm 2000i) support infants post extubation. The patient data, compared to historical control where CPAP was used prior to their adoption of HFT, resulted in extubation from higher ventilator rates (p < 0.01), fewer days on ventilators (p < 0.05). These data support Vapotherms proposed mechanisms of action for HFT with respect to CO2 elimination and improved alveolar oxygen concentrations. In addition, this study showed that incidence of ventilator-associated pneumonia was reduced (p < 0.05), and infants were discharged with greater weights (p < 0.05) despite similar lengths of stay and time to full feeds. The decrease in pneumonia is likely associated with reduction in ventilator time, while the greater discharge weights may be indicative of a reduced respiratory work effort (caloric consumption).

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http://www.ncbi.nlm.nih.gov/pubmed/17855805?dopt=Citation

Research in high flow therapy: Mechanisms of action by Dysart, K, Miller, TL, Wolfson, MR, & Shaffer, TH (Respiratory Medicine. 2009)

Dysart et al summarizes the mechanisms of action behind the efficacy of HFT via nasal cannula. The mechanisms discussed include washout of nasopharyngeal dead space, reduction of inspiratory resistance in the nasopharynx, improvement in airway and lung mechanics, mild distending pressure and a reduction in energy expenditure associated with inspiratory gas conditioning.

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http://www.ncbi.nlm.nih.gov/pubmed/19467849?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_R

Respiratory effects of tracheal gas insufflation in spontaneously breathing COPD patients,Nakos G,Lachana A,Prekates A,Pneumatikos J, Guillaume M, Pappas K, & Tsagaris H Intensive Care Med, 95 21:904

Nakos et al shows that flushing anatomical dead space of the upper airway in humans during spontaneous breathing improves respiratory work indices while reducing blood carbon dioxide.

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http://www.ncbi.nlm.nih.gov/pubmed/8636522?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_Re

The effects of high-flow vs low-flow oxygen on exercise in advanced obstructive airways disease by Chatila, W, Nugent, T, Vance, G, Gaughan, J, & Criner, GJ (CHEST 2004: 126, 1108-15)

Chatila et al showed that adult patients with airflow restriction were able to exercise longer (p < 0.05) on high flow oxygen therapy (HFT; 20 l/min) than on conventional low flow oxygen (< 6 l/min) despite matched FIO2. In addition to the overall longer performance, during HFT patients demonstrated lower dyspnea scores (p < 0.03), improved breathing patterns (RR, RR/Vt; p < 0.05), and lower arterial pressure (p < 0.05) and better oxygenation (p < 0.001). This study supports Vapotherm’s proposed mechanisms of action with respect to improving both oxygen and CO2 composition of alveolar gas by way of dead space elimination. The patients oxygenation indices were reported as significantly improved, plus the improvement in exercise time while demonstrating a lower breathing rate would indicate an effect on CO2 (CO2 was not different despite differences in work). Furthermore, the patients’ Ti/Ttotal was lower (p < 0.05) on HFT which may be indicative of reduced airway resistance.

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http://www.ncbi.nlm.nih.gov/pubmed/15486371?dopt=Citation

Use of a high-flow oxygen delivery system in a critically ill patient with dementia by Calvano, TP, Sill, JM, Kemp, KR, & Chung, KK. (Respiratory Care 2008: 53(12), 1739-43)

Calvano et al describe how they used High Flow Therapy (HFT; Vapotherm 2000i) to comfort and provide high oxygen fractions to an end-stage multi-lobar pneumonia patient who would not tolerate a mask to receive her prescribed non-invasive ventilation (this patient could not be intubated as per a DNR order). The paper describes how HFT improved not only oxygenation, but also work of breathing, comfort and nutrition.

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http://www.vtherm.com/_pdfs/Calvano_Demnetia.pdf

Use of high flow nasal cannula on a pediatric burn patient with inhalation injury and post-extubation stridor by Byerly FL, Haithcock JA, Buchanan IB, Short KA, Cairns BA, Burns (2006) 32: 121-5

Byerly et al demonstrate and discuss the impact of HFT on a pediatric burn patient in respiratory distress with respect to the mechanisms of action associated with humidification and potentially a mild distending pressure.

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http://www.ncbi.nlm.nih.gov/pubmed/16019146?ordinalpos=9&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_R

Nasal and oral flow-volume loops in normal subjects and patients with obstructive sleep apnea by Shepard JW & Burger CD (Am Rev Respir Dis. 1990 142: 1288-93)

Shepard and Burger evaluated the variations in nasopharyngeal flow resistance between inspiratory and expiratory phases of the breathing cycle. This study demonstrates that in normal subjects, inspiratory resistance through the nasopharynx is greater than expiratory resistance as a result of the distensibility of nasopharyngeal tissues. This information supports the concept that HFT via nasal cannula can reduce inspiratory work of breathing by reducing resistance normally associated with the encroachment of nasal tissues secondary to a negative nasopharyngeal pressure.

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http://www.ncbi.nlm.nih.gov/pubmed/2252246?ordinalpos=20&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_R

Airway Responsiveness to Low Inspired Gas Temperature in Preterm Neonates by Greenspan, JJ, Wolfson, MR & Shaffer, TH. (Journal of Pediatrics. 1991 118(3):443-445.)

Greenspan et al show that without warming and humidification of breathing gas, there is a statistically significant and clinically relevant adverse effect on dynamic compliance, airway conductance and elastic work of breathing. The implication is that better warming and humidification (to body temperature and saturated with water vapor) of respiratory gases alone can have a substantial impact on respiratory mechanics.

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http://www.ncbi.nlm.nih.gov/pubmed/1999789?ordinalpos=11&itool=EntrezSystem2.PEn

An Evaluation of 2 New Devices for Nasal High-Flow Gas Therapy by Waugh JB & Granger WM (Respiratory Care. 2004 49(8): 902-6)

Waugh and Granger describe the ability of the Vapotherm technology to accurately condition breathing gases. This report is an independent bench analysis that demonstrates Vapotherm technology delivers gas to the patient interface that is saturated with water vapor and at precisely controlled temperature at flows up to 40 lpm.

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http://www.rcjournal.com/contents/08.04/08.04.0902.pdf

Changes in airway resistance induced by nasal inhalation cold dry, dry, or moist air in normal individuals,Fontanari P, Burnet H, Zattara-Hartmann MC, Jammes Y Journal of Applied Physiology 96,81:1739

Fontanari et al evaluated the impact of gas conditioning on airway resistance in normal participants though the impact on the receptors in the nasal mucosa. This paper shows breathing warm, humid gas versus cool, dry gas results in a significant improvement in airway resistance. Furthermore, these authors demonstrate that the resistance change is due to stimulation of receptors in the nose because this response is eliminated when mouth breathing or when receptors in the nose are blocked. The results of this study support the proposition that HFT via nasal cannula should be done with optimal temperature and humidification to reduce resistive work of breathing.

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http://jap.physiology.org/cgi/content/full/81/4/1739

Comparing Two Methods of High Flow Delivery by Nasal Cannula Following Extubation by DD Woodhead (Journal of Perinatol 2006: 26,481-5)

Woodhead et al performed a crossover design study showing that when using optimal warming and humidification for nasal gas flows above 1 l/min (i.e., Vapotherm technology), nasal mucosa appeared more normal (p < 0.001) and patients had less pronounced indices of labored respiratory effort (p < 0.05). Additionally, some patients failed on conventional high flow cannula therapy and needed to be rescued to Vapotherm or reintubation; no infants failed on Vapotherm. These findings support Vapotherm’s proposed mechanisms that optimal warming and humidification not only preserves nasal tissue architecture but also have a positive impact on pulmonary mechanics, thus enhancing ease of breathing.

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http://www.ncbi.nlm.nih.gov/pubmed/16724119?log$=activity

Relationship between the humidity and temperature of inspired gas and the function of the airway mucosa by Williams R, Rankin N, Smith T, Galler D, & Seakins P (Critical Care Medicine. 1996 24(11):19)

Williams and colleagues review the impact of respiratory gas temperature and humidification on airway mucosal cell function. This report reviews peer-reviewed manuscripts and other valuable information sources to construct a model for optimal gas conditioning and show the effects, both acute and chronic of inadequate gas conditioning. This paper emphasizes the importance of precise respiratory gas warming and absolute humidification to protect airway cell function during respiratory support efforts.

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http://www.ncbi.nlm.nih.gov/pubmed/8917046?ordinalpos=6&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_Re

Resuscitation of Preterm Neonates by Using Room Air or 100% Oxygyen by Wang, CL; Anderson, C; Leone, TA; Wade, R; Govindaswami, B & Finer, NN. (Pediatrics. 2008 (121): 1083-1089)

Wang et al identify that the ideal oxygen percentage for use in resuscitation in newborns is between room air (21%) and 100%. Therefore there is a need for oxygen blending in the delivery room.

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http://www.ncbi.nlm.nih.gov/pubmed/18519476?ordinalpos=3&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_R

What is optimal humidity? by Rankin N (Respir Care Clin N Am. 1998 4(2): 321-8)

Dr. Rankin reviews the factors that determine optimal humidification for respiratory gases. This paper examines the relationship between water content of the inspired gas and mucosal function to determine that the optimal conditioning for inspired gas is 37ºC and 100% relative humidity.

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http://www.ncbi.nlm.nih.gov/pubmed/9648190?ordinalpos=13&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_R

Y-Piece Temperature and Humidification During Mechanical Ventilation by Solomita M, Daroowalla F, LeBlanc DS, & Smaldone GC (Respiratory Care. 2009 54(4): 480-6)

Williams and colleagues describe the shortcomings of heated wire circuit technologies for maintaining humidification during delivery of conditioned breathing gases. Although the emphasis behind this bench protocol is with regard to mechanical ventilation, the study demonstrates that heated wire circuit systems do not accurately maintain humidity of the conditioned gases. The study data show that while heated wire circuits can affect the temperature of the gas at the patient end, these systems allow for substantial water vapor loss within the patient circuit.

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http://www.rcjournal.com/contents/04.09/04.09.0480.pdf

Observ. Study of Humidified High-Flow Nasal Cannula Compared with Nasal Cont. Pos. Airway Pressure by Lampland, AL, MD, Plumm, B, Meyers, PA, Worwa, CT & Mammel, MC. (Pediatrics. 2009: 154, 177-182)

Despite the negative conclusion that is based on the false belief that pressure needs to be more substantial, the data show that the patients are quite stable on High Flow Therapy despite lower pressure.

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http://www.ncbi.nlm.nih.gov/pubmed/18760803?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_R

Work of breathing using high-flow nasal cannula in preterm infants by Saslow, JG, Aghai, ZH, Nakhla, TA, Lawrysh, R, Stahl, GE, & Pyon, KH (Journal of Perinatol 2006: 26, 476-80)

Saslow et al evaluate the use of high flow therapy (HFT; Vapotherm 2000i) with respect to breathing effort and airway pressure development. The most intriguing findings in this paper are that HFT up to 5 l/min does not produce more airway pressure than CPAP set to 6 cmH2O. In fact, these authors demonstrate that at 5 l/min airway pressure is significantly less that with a CPAP of 6. Although complex, this finding may have an explanation based on the concepts of gas flow properties where greater flow currents in the nasopharyngeal cavity may actually unload pressure forces to the airways.

To view paper click here:
http://www.ncbi.nlm.nih.gov/pubmed/16688202?dopt=Citation