Research ArticleOriginal Research

Performance of Invasive Mode in Different Heated Humidification Systems With High-Flow Nasal Cannula

Gustavo A Plotnikow, Dario S Villalba, Eliana Pérez Calvo, Corina Quiroga and Emiliano Navarro
Respiratory Care December 2022, 67 (12) 1551-1557; DOI: https://doi.org/10.4187/respcare.10170

Abstract

BACKGROUND: Oxygen therapy via high-flow nasal cannula generates physiologic changes that impact ventilatory variables of patients. However, we know that there are detrimental effects on airway mucosa related to inhalation of gases. The objective of this study was to evaluate the performance in terms of absolute humidity, relative humidity, and temperature of different brands of heated humidifiers and circuits in the invasive mode during the use of high-flow oxygen therapy in flows between 30 and 100 L/min.

METHODS: A prospective observational study conducted at the Sanatorio Anchorena equipment analysis laboratory; September 5 to October 20, 2019.

RESULTS: A statistically significant interaction was found among the programmed flows and the different combinations of devices and circuits for the delivery of absolute humidity (P < .001). An effect of flow on delivered absolute humidity was found, regardless of the equipment and circuit combination (P < .001). However, in the invasive mode, the combination of the Fisher&Paykel MR850 heated humidifier with the Medtronic-Dar circuit, the Intersurgical circuit, and the AquaVENT circuit always reached or achieved absolute humidity values > 33 mg/L, even at flows up to 100 L/min. The combination of the Flexicare FL9000 heated humidifier with the Fisher&Paykel RT202 circuit, the Fisher&Paykel Evaqua 2 circuit, the Flexicare circuit, the AquaVENT circuit, and the GGM circuit achieved similar results. The mean (SD) of absolute humidity delivered in the invasive mode (36.2 ± 5.9 mg/L) was higher compared with the noninvasive mode (26.8 ± 7.2 mg/L) (P < .001), regardless of circuit and programmed flows.

CONCLUSIONS: When heated humidifiers were used in the invasive mode for high-flow oxygen therapy, absolute humidity depended not only on the heated humidifiers and the combination of circuits but also on the programmed flow, especially at flows > 50 L/min. Moreover, the heated humidifiers exhibited different behaviors, in some cases inefficient, in delivering adequate humidification. However, some equipment improved performance when set to the invasive mode.

Introduction

Oxygen therapy through high-flow nasal cannula (HFNC) generates physiologic changes that impact ventilatory variables in different populations of patients who are critically ill, which is why its use in various ICUs has become generalized.1-6 There are many devices specifically designed to implement HFNC.7 But in low-to-middle income countries, the availability of such devices is limited. Instead, equipment available in ICUs, such as microprocessor ventilators with software for high-flow oxygen therapy in combination with heated humidifiers and heated-wire circuits, are often used.

We know that there are detrimental effects on airway mucosa related to inhalation of gases, especially poorly conditioned gases.8,9 Clinical tolerance of such flows during HFNC is strongly dependent on the delivery of heated and humidified gas because it substantially reduces dryness of the mouth and throat.10,11 In relation to this, the main difference between the operating modes (invasive or noninvasive) of the heated humidifiers lies in the temperature.12 In the invasive mode, the devices operate in a higher temperature range than in the noninvasive mode, thus their ability to condition gases should be increased. Flow and temperature are key features that condition humidity, a variable that can impact tolerance and hence outcomes of patients who are critically ill.13

In this regard, although the most common HFNC devices can provide adequate humidity under optimal conditions, under-humidification can also occur under particular conditions of use, such as low ambient temperature, high flows, or inadequate temperature programming.14 We also know that the gas delivery condition in terms of absolute humidity during HFNC performed through microprocessed ventilators with heated humidification systems may not be adequate because some devices fail to deliver the recommended minimum absolute humidity.15 The objective of this study was to evaluate the performance in terms of absolute humidity, relative humidity (RH) and temperature of different brands of heated humidifiers and circuits in the invasive mode during the use of high-flow oxygen therapy in conventional (30–60 L/min) and nonconventional (70–100 L/min) flow ranges. Furthermore, to determine whether the variables evaluated are influenced by the operating mode of the heated humidifier (invasive or noninvasive).

QUICK LOOK

Current Knowledge

The use of the heated humidifiers in the noninvasive mode during high-flow nasal cannula therapy to optimize the humidity delivered and to improve patient comfort is recommended.

What This Paper Contributes to Our Knowledge

In this study, the heated humidifiers exhibited different behaviors, being in many cases inefficient in delivering adequate humidification, even at conventional flows. However, some equipment improved the performance when set to the invasive mode, which achieved absolute humidity within recommended limits.

Methods

We performed this prospective observational study in the Sanatorio Anchorena equipment analysis laboratory between September 5 and October 20, 2019. To obtain humidity measurements, an electronic thermohygrometer (605-H1, Testo, West Chester, Pennsylvania) was used (temperature range, 0–50°C, accuracy ± 0.5°C; humidity accuracy up to 95%). A microprocessor ventilator (Savina 300, Dräger, Lübeck, Germany) was used to deliver HFNC. The gaseous mixture used as a ventilator drive consisted of compressed air and oxygen with 24.2°C and absolute humidity of 3.28 mg/L, and with 24.7°C and absolute humidity of 0.44 mg/L respectively. For active humidification, 3 servo-controlled heated humidifiers were tested (MR850, Fisher & Paykel, Auckland, New Zealand; FL9000, Flexicare, Mountain Ash, Wales; and AquaVENT, Armstrong, Coleraine, Ireland), and 7 circuits with a heater-wire (RT202, Fisher & Paykel; Evaqua 2, Fisher & Paykel; Medtronic-Dar, Mirandola, Italy; Flexicare; Intersurgical, Wokingham, United Kingdom; AquaVENT; and GGM, Changhua, Taiwan). Environmental temperature, RH, and absolute humidity were collected from the laboratory during each measurement, and the temperature, RH, and absolute humidity that resulted from the application of each of the flows were recorded at the distal end of the circuit.

The heated humidifier was evaluated in the invasive and noninvasive modes. The 7 heated-wire circuits were randomly combined with each device, and each combination was assessed with flows of 30, 40, 50, 60, 70, 80, 90, and 100 L/min after a random sequence generated online (https://www.randomization.com). During the study, recordings of 42 flow sequences were performed. Each was composed of 9 sets of temperature, RH, and absolute humidity measurements (ie, the environment and each of the 8 flows). Between each measurement, the hygrometer was inspected to assess the presence of condensation that could impact the measurements. The protocol for the measurements during the study was described as follows:

  1. Fill the chambers with distilled water with sufficient volume for the entire duration of testing.

  2. Turn the heated humidifier on in the invasive or the noninvasive mode and attached circuits; turn the device on (no flow and the chamber filled with distilled water) and allow 5 min for device stabilization.

  3. Record the environmental laboratory measurements (temperature, RH, and absolute humidity) at the end of the initial 5 min of stabilization.

  4. Activate the ventilator flow at 20 L/min for 5 min; after 5 min of flow at 20 L/min, set the ventilator flow for the initial measurement according to the randomization sequence; allow the device to stabilize for 10 min at each of the programmed flows before taking the measurements.

  5. Measurements consisted of a series of 3 recordings over min (1 per min); in each minute, temperature, RH, and a calculation of the absolute humidity that corresponded to that measurement were recorded.

  6. Although the system reached its stabilization in 1 min, to avoid the influence of one measurement on the next one, we allowed a period of 3 min between each measurement (ie, zero movements).

  7. At the end of the complete measurement sequence, which required 2 h, the presence or absence of condensation in the circuits was noted (ie, yes or no).

Statistical Analysis

Continuous variables were reported as median (interquartile range) or mean ± SD according to normality checked by using the Shapiro-Wilk test. A linear mixed-effects regression model (for repeated measures) was fitted to assess the interaction between flows and different combinations of brands and circuits. The P values for multiple comparisons were reported with the post hoc Tukey correction. Results with 2-tailed P ≤ .05 were considered statistically significant. Data were analyzed with R4.3 (R Foundation for Statistical Computing, Vienna, Austria).

Results

The mean ± SD environmental temperature in the laboratory was 21.6 ± 1.6°C, with a mean ± SD RH of 45.5 ± 14.1% and a mean ± SD absolute humidity of 8.5 ± 2.4 mg/L. A statistically significant interaction was found between the programmed flows and the different combinations of the devices and circuits for the delivery of absolute humidity (P < .001) (Tables 1–3). That is, the absolute humidity depends on the devices and the programmed flow, the higher the flow, the lower the absolute humidity.

View this table:
Table 1.

Fisher & Paykel MR850 Heated Humidifier Mean Temperature and Humidity at Different Flows in the Invasive Mode for All Circuit Combinations

View this table:
Table 2.

Flexicare FL9000 Heated Humidifier Mean Temperature and Humidity at Different Flows in the Invasive Mode for All Circuit Combinations

View this table:
Table 3.

AquaVENT Armstrong Heated Humidifier Mean Temperature and Humidity at Different Flows in the Invasive Mode for All Circuit Combinations

Among the different circuit and equipment combinations, the Fisher & Paykel MR850 heated humidifier with the Medtronic-Dar heater-wire circuit (heated humidifier 1 circuit 3) was the highest performer in relation to absolute humidity, with no significant differences with the same device and the Intersurgical heated-wire circuit (heated humidifier 2 circuit 5) (P = .92), AquaVENT heated-wire circuit (heated humidifier 1 circuit 6) (P = .14), and the GGM heater-wire circuit (heated humidifier 1 circuit 7) (P = .34) (Fig. 1). An effect of flow on delivered absolute humidity was found, regardless of the equipment and circuit combination (P < .001). However, the mean ± SD absolute humidity delivered in the invasive mode was higher versus the noninvasive mode (36.2 ± 5.9 mg/L vs 26.8 ± 7.2 mg/L; (P < .001), regardless of circuit and programmed flows. Different combinations of circuits and flows between the 2 modes are shown in Figures 2–4.

Fig. 1.
Fig. 1.

Absolute humidity delivered by different combinations of devices and circuits in the invasive mode, regardless of the flow used. Data are presented as median and inter-quartile range (IQR). Dashed red line indicates absolute humidity of 33 mg/L. HH1 = Fisher & Paykel MR850 heated humidifier; HH2 = Flexicare FL9000 heated humidifier; HH3 = AquaVENT Armstrong heated humidifier; Circ1 = Fisher & Paykel RT202 heater-wire circuit; Circ2 = Fisher & Paykel Evaqua 2 heater-wire circuit; Circ3 = Medtronic-Dar heater-wire circuit; Circ4 = Flexicare heater-wire circuit; Circ5 = Intersurgical heater-wire circuit; Circ6 = AquaVENT heater-wire circuit; Circ7 = GGM heater-wire circuit.

Fig. 2.
Fig. 2.

Absolute humidity delivered at different flows in relation to the different combinations of devices and circuits. Fisher & Paykel MR850 Heated Humidifier (HH1). A: Invasive mode; B: Noninvasive mode. Data are presented as mean. Dashed line indicates absolute humidity of 33 mg/L. HH2 = Flexicare FL9000 heated humidifier; HH3 = AquaVENT Armstrong heated humidifier; Circuit 1 = Fisher & Paykel RT202 heater-wire circuit; Circuit 2 = Fisher & Paykel Evaqua 2 heater-wire circuit; Circuit 3 = Medtronic-Dar heater-wire circuit; Circuit 4 = Flexicare heater-wire circuit; Circuit 5 = Intersurgical heater-wire circuit; Circuit 6 = AquaVENT heater-wire circuit; Circuit 7 = GGM heater-wire circuit.

Fig. 3.
Fig. 3.

Absolute humidity delivered at different flows in relation to the different combinations of devices and circuits. Flexicare FL9000 heated humidifier (HH2). A: Invasive mode; B: Noninvasive mode. Data are presented as mean. Dashed line indicates absolute humidity of 33 mg/L. HH1 = Fisher & Paykel MR850 heated humidifier; HH3 = AquaVENT Armstrong heated humidifier; Circuit 1 = Fisher & Paykel RT202 heater-wire circuit; Circuit 2 = Fisher & Paykel Evaqua 2 heater-wire circuit; Circuit 3 = Medtronic-Dar heater-wire circuit; Circuit 4 = Flexicare heater-wire circuit; Circuit 5 = Intersurgical heater-wire circuit; Circuit 6 = AquaVENT heater-wire circuit; Circuit 7 = GGM heater-wire circuit.

Fig. 4.
Fig. 4.

Absolute humidity delivered at different flows in relation to the different combinations of devices and circuits. AquaVENT Armstrong heated humidifier (HH3). A: Invasive mode; B: Noninvasive mode. Data are presented as mean. Dashed line indicates absolute humidity of 33 mg/L. HH1 = Fisher & Paykel MR850 heated humidifier; HH2 = Flexicare FL9000 heated humidifier; Circuit 1 = Fisher & Paykel RT202 heater-wire circuit; Circuit 2 = Fisher & Paykel Evaqua 2 heater-wire circuit; Circuit 3 = Medtronic-Dar heater-wire circuit; Circuit 4 = Flexicare heater-wire circuit; Circuit 5 = Intersurgical heater-wire circuit; Circuit 6 = AquaVENT heater-wire circuit; Circuit 7 = GGM heater-wire circuit.

In the invasive mode, the combination of the Fisher & Paykel MR850 heated humidifier with the Medtronic-Dar heated-wire circuit (heated humidifier 1 circuit 3), with the Intersurgical heater-wire circuit (heated humidifier 1 circuit 5), and with the AquaVENT heated-wire circuit (heated humidifier 1 circuit 6) always achieved absolute humidity values > 33 mg/L, even at flows up to 100 L/min (Fig. 2). The combination of the Flexicare FL9000 heated humidifier with the Fisher & Paykel RT202 heated-wire circuit (Heated humidifier 2 circuit 1), with the Fisher & Paykel Evaqua 2 heated-wire circuit (Heated humidifier 2 circuit 2), with the Flexicare heated-wire circuit (Heated humidifier 2 circuit 4), with the AquaVENT heated-wire circuit (Heated humidifier 2 circuit 6) and with the GGM heated-wire circuit (Heated humidifier 2 circuit 7) achieved similar results (Fig. 3).

A drop in the absolute humidity with increasing flow for the AquaVENT Armstrong heated humidifier, being unable to maintain the delivered absolute humidity > 33 mg/L at flows > 50 L/min is shown in Figure 4. The combination of this device with the Intersurgical heated-wire circuit (Heated humidifier 3 circuit 5) was the lowest performing (mean ± SD absolute humidity, 29.2 ± 6.5 mg/L), with significant differences compared with the combinations with other circuit brands (P < .001). With respect to the presence of circuit condensation, we found 2 different conditions. During the invasive mode, condensation was observed with all the heated humidifiers and their combinations, except for the Dar circuit with the Fisher & Paykel MR850 and the AquaVENT Armstrong heated humidifiers. In contrast, with the noninvasive mode, condensation was only observed when using the Fisher & Paykel MR850 heated humidifier with all heated-wire circuits except for the Dar circuit.

Discussion

This study provides important information about the performance in terms of temperature and delivered humidity of heated humidifier systems used for HFNC and, to our knowledge, the first study to evaluate the performance of these devices in different modes. When comparing the different measurement sequences, an interaction was found between the different devices with their circuits and the programmed flow. In other words, the absolute humidity depended not only on the combination of the heated humidifier with the circuits but also on the programmed flow, with statistically significant differences in the mean absolute humidity for each flow between the different devices and their combinations, in some cases, lower than the recommended (33 mg/L).14,16,17

Although, when using HFNC, the gas flow passes through the upper airway, the use of humidification is recommended in noninvasive techniques to improve comfort and adherence.10,11,13,16,18 Our study published in 2020 showed that many heated humidifiers in noninvasive modes failed to achieve the recommended minimum absolute humidity values even at conventional flows (<60 L/min).15 However, the comparison in this study allowed us to observe that, in the heated humidifiers evaluated, performance improved with the programming of the equipment in the invasive mode and the flow used. In this way, the heated humidifiers that did not reach the recommended absolute humidity managed to do so even when exposed to flows of up to 100 L/min.

In the invasive mode, the heated humidifier that achieved the highest performance in terms of absolute humidity was above the recommended lower limit, regardless of the circuit and flows supplied.14,16 The lowest performing heated humidifier was far from achieving the recommended absolute humidity for flows > 50 L/min, which decreased significantly with increasing flow. However, it was able to achieve, and even exceed, the 33 mg/L absolute humidity at a flow of ≤50 L/min. These results would be of great interest in clinical practice because under-humidification (worsening patients’ comfort) could impair the function of the ciliary epithelium and secretion clearance, even favoring secretion retention.8,9,19 Although this phenomenon of under-humidification caused by decreasing the contact time of the gas with the air-liquid interface of the heated humidifier chamber for equipment that, even in the invasive mode, does not reach 33 mg/L absolute humidity could be mitigated, the way to achieve this in clinical practice could be difficult.20

Two of the three heated humidifiers managed to deliver absolute humidity > 33 mg/L, even at a high flow, of 100 L/min; however, the different combinations did not always achieve these results. This suggests reconsidering the combination of interfaces and equipment and avoiding generalization because not all combinations are useful in clinical practice to deliver absolute humidity > 33 mg/L, with devices that may be unable to sustain adequate absolute humidity at flows > 50 L/m. Although the temperature is higher in the invasive mode than that recorded in the noninvasive mode,12 which largely justifies the better performance of the equipment, in no case did it reach a temperature that, sustained over time, represents a risk of thermal damage.12 According to the International Organization for Standardization, a sustained delivered gas temperature > 41°C represents a potential thermal risk to the patient, and the International Organization for Standardization considers the use of a temperature of 43°C as an extreme over-temperature alarm condition to protect the patient from thermal injury. This finding in our study is of great relevance to the safety of using an invasive mode in a noninvasive therapy such as high-flow oxygen therapy.16,21

According to the study by Chikata et al,22 the ambient temperature has an influence on the amount of condensation recorded in the circuits, being considerably greater at 20°C compared with a temperature of 25°C. In the invasive mode, condensation was evident in all combinations and flows, except for the combination of the Dar circuits with the Fisher & Paykel MR850 heated humidifier or the Armstrong AquaVENT heated humidifier, possibly related to the better ability of the equipment to keep the temperature high in this mode, regardless of the flow used. In addition, the behavior of the Dar circuit may be due to its design, which minimizes the influence of ambient temperature on the circulating gas flow. It should be noted that, during this study, however, the average ambient temperature recorded was above the minimum necessary to reduce the risk of condensation.

The study had certain limitations. Although the study was designed to assess the performance of the equipment in different modalities and at different flows, no simulation of different ventilatory patterns was performed to assess their influence on the performance of the humidification systems, although, in invasive mechanical ventilation, there is evidence to suggest that this may not affect the delivery of absolute humidity.23 Furthermore, the use of a Embedded Image of 0.21 could be questioned. However, from the point of view of thermodynamic characteristics, both compressed air and oxygen (or a mixture of both) behave similarly.24 Also, as a laboratory study, the results obtained should be interpreted with caution in a clinical setting.

Conclusions

When heated humidifiers are used in the invasive mode for high-flow oxygen therapy, absolute humidity depends not only on the heated humidifiers and the combination of circuits but also on the programmed flow, especially at flows > 50 L/min. Moreover, the heated humidifiers exhibit different behavior being, in some cases, inefficient in delivering adequate humidification even at conventional flows. However, although requiring closer monitoring of condensation, some equipment that was inefficient in the noninvasive mode improved performance when set to the invasive mode, achieving absolute humidity within the recommended limits.

Acknowledgments

The authors thank Emiliano Gogniat for his accompaniment and collaboration.

Footnotes

  • Correspondence: Gustavo A Plotnikow PT, 3954 Gral. Manuel Belgrano, Florencio Varela (ZIP 1888), Buenos Aires, Argentina; E-mail: gplotnikow{at}hbritanico.com.ar

  • Mr Plotnikow discloses relationships with Medtronic Argentina and Vapotherm. The remaining authors have disclosed no conflicts of interest.

REFERENCES

  1. 1.↵
    1. Mauri T,
    2. Wang Y-M,
    3. Dalla Corte F,
    4. Corcione N,
    5. Spinelli E,
    6. Pesenti A
    . Nasal high flow: physiology, efficacy and safety in the acute care setting, a narrative review. Open Access Emerg Med 2019;11:109-120.
    OpenUrl
  2. 2.
    1. Sztrymf B,
    2. Messika J,
    3. Bertrand F,
    4. Hurel D,
    5. Leon R,
    6. Dreyfuss D,
    7. Ricard J-D
    . Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study. Intensive Care Med 2011;37(11):1780-1786.
    OpenUrlCrossRefPubMed
  3. 3.
    1. Plotnikow GA,
    2. Accoce M,
    3. Fredes S,
    4. Tiribelli N,
    5. Setten M,
    6. Dorado J,
    7. et al
    . High-flow oxygen therapy application in chronic obstructive pulmonary disease patients with acute hypercapnic respiratory failure: a multicenter study. Crit Care Explor 2021;3(2):e0337.
    OpenUrl
  4. 4.
    1. Parke RL,
    2. Eccleston ML,
    3. McGuinness SP
    . The effects of flow on airway pressure during nasal high-flow oxygen therapy. Respir Care 2011;56(8):1151-1155.
    OpenUrlAbstract/FREE Full Text
  5. 5.
    1. Plotnikow GA,
    2. Thille AW,
    3. Vasquez DN,
    4. Pratto RA,
    5. Quiroga CM,
    6. Andrich ME,
    7. et al
    . Effects of high-flow nasal cannula on end-expiratory lung impedance in semi-seated healthy subjects. Respir Care 2018;63(8):1016-1023.
    OpenUrlAbstract/FREE Full Text
  6. 6.↵
    1. Möller W,
    2. Celik G,
    3. Feng S,
    4. Bartenstein P,
    5. Meyer G,
    6. Oliver E,
    7. et al
    . Nasal high flow clears anatomical dead space in upper airway models. J Appl Physiol (1985) 2015;118(12):1525-1532.
    OpenUrlCrossRefPubMed
  7. 7.↵
    1. Nishimura M
    . High-flow nasal cannula oxygen therapy devices. Respir Care 2019;64(6):735-742.
    OpenUrlAbstract/FREE Full Text
  8. 8.↵
    1. Kilgour E,
    2. Rankin N,
    3. Ryan S,
    4. Pack R
    . Mucociliary function deteriorates in the clinical range of inspired air temperature and humidity. Intensive Care Med 2004;30(7):1491-1494.
    OpenUrlPubMed
  9. 9.↵
    1. Williams R,
    2. Rankin N,
    3. Smith T,
    4. Galler D,
    5. Seakins P
    . Relationship between the humidity and temperature of inspired gas and the function of the airway mucosa. Crit Care Med 1996;24(11):1920-1929.
    OpenUrlCrossRefPubMed
  10. 10.↵
    1. Chanques G,
    2. Constantin J-M,
    3. Sauter M,
    4. Jung B,
    5. Sebbane M,
    6. Verzilli D,
    7. et al
    . Discomfort associated with under humidified high-flow oxygen therapy in critically ill patients. Intensive Care Med 2009;35(6):996-1003.
    OpenUrlCrossRefPubMed
  11. 11.↵
    1. Cuquemelle E,
    2. Pham T,
    3. Papon J-F,
    4. Louis B,
    5. Danin P-E,
    6. Brochard L
    . Heated and humidified high-flow oxygen therapy reduces discomfort during hypoxemic respiratory failure. Respir Care 2012;57(10):1571-1577.
    OpenUrlAbstract/FREE Full Text
  12. 12.↵
    1. Flink RC,
    2. van Kaam AH,
    3. de Jongh FH
    . A humidifier in the invasive mode during noninvasive respiratory support could increase condensation and thereby impair airway patency. Acta Paediatr 2018;107(11):1888-1892.
    OpenUrl
  13. 13.↵
    1. Mauri T,
    2. Galazzi A,
    3. Binda F,
    4. Masciopinto L,
    5. Corcione N,
    6. Carlesso E,
    7. et al
    . Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula. Crit Care 2018;22(1):120.
    OpenUrl
  14. 14.↵
    1. Delorme M,
    2. Bouchard P-A,
    3. Simard S,
    4. Lellouche F
    . Hygrometric performances of different high-flow nasal cannula devices: bench evaluation and clinical tolerance. Respir Care 2021;66(11):1720-1728.
    OpenUrlAbstract/FREE Full Text
  15. 15.↵
    1. Plotnikow GA,
    2. Villalba D,
    3. Gogniat E,
    4. Quiroga C,
    5. Pérez Calvo E,
    6. Scapellato JL
    . Performance of different active humidification systems in high-flow oxygen therapy. Respir Care 2020;65(9):1250-1257.
    OpenUrlAbstract/FREE Full Text
  16. 16.↵
    1. Restrepo RD,
    2. Walsh BK
    American Association for Respiratory Care; Restrepo RD, Walsh BK. Humidification during invasive and noninvasive mechanical ventilation: 2012. Respir Care 2012;57(5):782-788.
    OpenUrlAbstract/FREE Full Text
  17. 17.↵
    1. Plotnikow GA,
    2. Accoce M,
    3. Navarro E,
    4. Tiribelli N
    . Humidification and heating of inhaled gas in patients with artificial airway: a narrative review. Rev Bras Ter Intensiva 2018;30(1):86-97.
    OpenUrl
  18. 18.↵
    1. Roca O,
    2. Riera J,
    3. Torres F,
    4. Masclans JR
    . High-flow oxygen therapy in acute respiratory failure. Respir Care 2010;55(4):408-413.
    OpenUrlAbstract/FREE Full Text
  19. 19.↵
    1. Sottiaux TM
    . Consequences of under- and over-humidification. Respir Care Clin N Am 2006;12(2):233-252.
    OpenUrlPubMed
  20. 20.↵
    1. Chikata Y,
    2. Morinishi K,
    3. Nishimura M
    . Humidification in very-high-flow nasal-cannula therapy in an adult lung model. Respir Care 2019;64(7):809-817.
    OpenUrlAbstract/FREE Full Text
  21. 21.↵
    International Organization for Standardization (1998) Humidifiers for medical use. ISO 1988;8185(E) 60:14. Available at: https://www.iso.org/standard/15275.html. Accessed June 15, 2022.
    OpenUrl
  22. 22.↵
    1. Chikata Y,
    2. Unai K,
    3. Izawa M,
    4. Okuda N,
    5. Oto J,
    6. Nishimura M
    . Inspiratory tube condensation during high-flow nasal cannula therapy: a bench study. Respir Care 2016;61(3):300-305.
    OpenUrlAbstract/FREE Full Text
  23. 23.↵
    1. Lellouche F,
    2. Qader S,
    3. Taillé S,
    4. Lyazidi A,
    5. Brochard L
    . Influence of ambient temperature and minute ventilation on passive and active heat and moisture exchangers. Respir Care 2014;59(5):637-643.
    OpenUrlAbstract/FREE Full Text
  24. 24.↵
    1. Züchner K
    . Humidification: measurement and requirements. Respir Care Clin N Am 2006;12(2):149-163.
    OpenUrlPubMed
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