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Delivery of heliox with a semi-closed circuit during spontaneous breathing: a comparative economic theoretical study
© Jurickova et al. 2015
Received: 3 November 2014
Accepted: 27 May 2015
Published: 10 June 2015
Heliox is a mixture of oxygen and helium which reduces airway resistance in patients with airway obstruction. In clinical practice, patients breathing spontaneously receive heliox via an open circuit. Recently, a semi-closed circuit for heliox administration has been proposed which minimizes consumption of heliox and therefore cost of the heliox therapy; although, the semi-closed circuit is associated with additional costs. The aim of the study is to conduct an economical analysis comparing total cost of heliox therapy using an open versus a semi-closed circuit in spontaneously breathing patients with airway obstruction.
Four different systems for heliox administration were analyzed: an open circuit and three alternatives of a semi-closed circuit involving a custom made semi-closed circuit and two standard anesthesia machines. Total costs of heliox therapy were calculated for all the systems. For calculation of gas consumption, the clinical procedures limiting continuous heliox therapy including the aerosol therapy, personal hygiene and nutrition were taken into account. A sensitivity analysis was conducted for main input variables that may influence the results of the study.
Price of gases consumed by a semi-closed system represents less than 20 % of price of gases when a standard open circuit is used. This represents a saving of approximately 540 EUR per patient. The initial cost of the custom-made semi-closed circuit recuperates after treatment of 18 patients. The corresponding number of patients is 32 when a low-cost anesthesia machine is initially acquired and rises to 69 when a highly advanced anesthesia machine is considered.
Heliox therapy in spontaneously breathing patients using a semi-closed circuit becomes more cost-effective compared to the open circuit, currently used in clinical practice, when applied in a sufficient number of cases. The impact of finding a cheaper way of heliox administration on the clinical practice needs to be ascertained.
Severe airway obstruction accompanies many diseases of various etiologies. Nosological units characterized by airway obstruction include bronchial asthma, chronic obstructive pulmonary disease (COPD), epiglottitis, laryngitis, tracheitis, bronchiolitis, tracheal or bronchial stenosis. Severe airway obstruction induces increased work of breathing, decreased alveolar ventilation and development of respiratory insufficiency leading to respiratory failure, often treated by mechanical ventilation. Invasive mechanical ventilation is associated with pulmonary and extrapulmonary complications and complications caused by the upper airway management .
Inhalation of heliox (a mixture of oxygen and helium) instead of air significantly reduces airway resistance due to the very low density of helium compared with nitrogen as the main component of air . Therefore, heliox reduces work of breathing and improves gas exchange in a variety of respiratory conditions .
Despite lack of large, adequately powered, randomized controlled clinical studies, heliox is believed to postpone intubation and reduce intubation rate . This represents the main benefit of heliox compared to the standard therapy using invasive ventilation which necessitates intubation.
In spontaneously breathing patients, heliox is administered using an open circuit via a facemask connected to a reservoir bag with a sufficient inflow to keep it inflated . The consumption of heliox is very high in the open circuit, typically more than 18 L/min, in order to prevent rebreathing of the expired gas. Heliox therapy using the open circuit is associated with high costs. Heliox is relatively expensive compared to oxygen, but is much less expensive than mechanical ventilation . Thus, the high cost of heliox represents a disadvantage of heliox therapy and contributes to limitation of its routine clinical use.
In order to reduce costs of heliox therapy, a semi-closed circuit for heliox administration has been developed . This way of heliox administration in patients with airway obstruction allows a decrease in heliox consumption to even less than 1 L/min. However, one should consider higher initial cost of the equipment, additional nursing time and other requirements while using a semi-closed circuit.
The aim of the study is to investigate whether the administration of heliox using a semi-closed circuit represents a cost effective alternative to a standard way of heliox administration in spontaneously breathing patients with severe airway obstruction.
The second alternative is to use a standard anesthesia machine. In order to compare all the possibilities, four different systems for heliox administration were compared: a standard open circuit with a mask for non-invasive ventilation, a custom made semi-closed circuit and two standard anesthesia machines differing in their acquisition costs: a low-cost anesthesia machine and an advanced anesthesia machine.
Data used for the cost analysis
Custom made circuit
Low-cost anesthesia machine
Advanced anesthesia machine
Initial costs and service (EUR)
Price of device
Service for 10 years
Total initial and service costs (EUR), CTIS
Costs per patient (EUR)
Cost of consumables per a patient
Cost of sterilization per a patient
Cost of gases per a patient
Total costs per patient (EUR), CTPP
Costs of training for the open circuit and both the anesthesia machines are fixed by the manufacturers. The cost of training for the custom made semi-closed circuit was estimated as an average value of the training costs for both the anesthesia machines.
The cost of service for the open circuit and both the anesthesia machines represent the real prices of Safety technical inspections of the corresponding devices calculated for the whole lifetime which is considered to be 10 years. The cost of service for the custom-made circuit is equal to the service cost of the low-cost anesthesia machine as the complexity of these two systems is comparable.
Cost of consumables calculated per patient is also presented in Table 1. For an open circuit, the price of consumables per patient comprises prices of a T-piece, a piece of hose, and a high concentration face mask (Hi-Ox80, Viasys Healthcare, Yorba Linda, CA, USA). For a semi-closed circuit, the costs per patient comprise prices of a Y-piece, soda lime and an NIV face mask (NIV 7500 series V2 mask, Hans Rudolph, Shawnee, KS, USA) divided by the maximum sterilization cycles recommended by its manufacturer plus one additional time.
Cost of sterilization per patient related to a semi-closed circuit encompasses sterilization costs of an oro-nasal mask for non-invasive ventilation (NIV 7500) and components of the whole patient breathing system comprising of CO2 absorber, one-way valves, breathing bag and an expiratory valve.
where VOC (L) stands for the total volume of gas consumed by a patient during the whole therapy using an open circuit, VSCC (L) stands for the total volume of gas consumed by a patient during the whole therapy using a semi-closed circuit, qOC (L/min) is gas flow rate during the high flow therapy using an open circuit, qINH (L/min) is gas flow rate during the inhalation, qDEN (L/min) is gas flow rate during the denitrogenation, qSCC (L/min) is gas flow rate during the low flow therapy, tOC (min) is duration of high flow therapy, tINH (min) is duration of inhalation, tDEN (min) is duration of denitrogenation, and tSCC (min) is duration of low flow therapy.
Price of gases
Price per cylinder (EUR)
Volume at A.T.P.D. (L)
Price per liter at A.T.P.D. (EUR)
50 L at 200 bar
50 L at 200 bar
where CHTPP is the resultant cost of heliox therapy per patient, CTIS stands for the initial and service costs, CTPP for total costs per patient and NP stands for a total number of expected therapy cycles provided with the assessed system, i.e., a number of patients when no repeated applications are assumed. Values of CTIS and CTPP were taken from Table 1. Dependence of the total cost of heliox therapy per patient, CHTPP, was presented in a form of graph for all fours assessed heliox administration systems in order to allow for comparison.
Only two parameters may change and affect CHTPP significantly and were studied during the consequent sensitivity analysis. The first variable studied was the price of heliox. CHTPP were computed for heliox prices if they were increased or decreased by 25 %. The second variable studied was the patient’s minute ventilation. The average minute ventilation of 7.5 L/min which corresponds to healthy patients was increased to 10 L/min, 12.5 L/min and 15 L/min during the sensitivity analysis.
Price of gases consumed by a patient is significantly higher when a standard way of heliox administration using an open circuit is used compared to a semi-closed circuit. Price of gases consumed by a semi-closed system represents less than 20 % of price of gases when a standard open circuit is used which represents a saving of approximately 540 EUR per patient.
The main finding of this study is that a semi-closed circuit for heliox administration in spontaneously breathing patients reduces cost of heliox therapy significantly to one-fifth the cost compared to the standard way of heliox administration using an open circuit. If a new semi-closed circuit is needed, the initial cost of such a system is recuperated after heliox application in 18 patients when the system is assembled from standard components of anesthesia circuits. When a standard anesthesia machine is initially acquired, the cost is recuperated in 32–69 patients depending on the initial cost of the anesthesia machine.
The specified reduction in cost of the heliox therapy per patient using a semi-closed circuit is calculated while taking into account standard procedures, such as aerosol therapy, personal hygiene and nutrition, which disrupt the low-flow heliox therapy and thereby increase heliox consumption and cost.
As there are many possibilities how to acquire a suitable semi-closed system, three possibilities are considered in this study. The cheapest possibility is to assemble a semi-closed system from standard commercially available components of anesthesia machines. The calculated cost also includes the system assembly by a biomedical company. Use of a commercially available anesthesia machine represents a more expensive alternative. Since the modern anesthesia machines contain features that would not be utilized during the desired heliox therapy, the simplest system would be the most cost-effective option.
Airflow resistances of the inspiratory and expiratory limbs of a semi-closed circuit should be minimized as they increase patient’s imposed work of breathing, which represents a disadvantage of a semi-closed circuit. A substantial part of the imposed work of breathing may be caused by the high resistance of the expiratory valve (Adjustable Pressure Limiting valve). We reached the lowest resistance with a simple water seal, which is used for bubble continuous positive airway pressure . Bacterial and viral breathing filters have relatively high airflow resistance that even increases when the filters become wet . Therefore, the analyzed semi-closed systems did not contain any breathing filter. As a consequence, all components of the semi-closed circuits require sterilization after each patient. The costs of sterilization are therefore included in the cost analysis conducted in this study.
The custom-made semi-closed circuit was used in COPD patients and tested in a clinical trial approved by the State Institute for Drug Control, Czech Republic (EudraCT number: 2008-008274-31). For analysis conducted in this study we used published input data and our experience from the clinical trial. Since this study is a theoretical cost analysis, it does not describe the clinical trial and its evaluation.
The average length of heliox therapy was considered to be 25 h per patient in this study in concordance with the estimated time to onset of a steroid response to be as early as 2 to 4 h and as late as 1 to 2 days . The duration was also determined based on our clinical experience with typical length of heliox therapy in COPD exacerbation patients.
Based on our previous clinical experience, the phase of denitrogenation should be approximately 5 min which was an average length of denitrogenation by a fresh gas flow rate of 8 L/min resulting in a concentration of helium higher then 70 % measured in the inspiratory limb of the semi-closed circuit. Even though the complete denitrogenation cannot be accomplished within 5 min, the traces of nitrogen washed out from the body are effectively eliminated from the semi-closed circuit during the subsequent ventilation with a relatively high heliox fresh gas flow rate of 3 L/min.
The basic economic calculations for the open circuit were conducted assuming standard condition that the fresh gas flow through an open circuit should be three times higher than the minute ventilation of a patient in order to avoid rebreathing of expired gas . Considering the average minute ventilation in a healthy adult of 7.5 L/min , the basic fresh gas flow through the open circuit was assumed to be 22.5 L/min. In respiratory diseases such as COPD and bronchial asthma the minute ventilation increases significantly [13–15]. Therefore, the economic simulations for the open circuit were conducted for minute ventilations which were increased to 10 L/min, 12.5 L/min and 15 L/min. In contrast, an increase in minute ventilation of a patient does not affect the required fresh gas flow into the semi-closed circuit due to the rebreathing principle and exhaled CO2 removal.
During the low-flow heliox therapy, usage of a leak-free semi-closed circuit allows reduction of fresh gas flow to less then 1 L/min. Even though a high-quality sealed face mask is used, contamination of the semi-closed circuit by ambient air may decrease the helium concentration. A fresh gas flow of 3 L/min is high enough to compensate for the leak in the face mask. Based on our previous clinical experience, 3 L/min fresh gas flow assures that helium concentration in the semi-closed circuit is always higher than 70 % thus maximizing the positive helium effect in the obstructed airways.
Heliox 80:20 (80 % of helium and 20 % of oxygen mixture) was considered during the analysis. Oxygen fraction higher than 20 % reduces helium concentration and thereby has a negative effect on the airway resistance improvement caused by heliox. Although the lowest effective helium concentration is unknown, it is generally accepted to be more than 60 % to have positive physiological effects . The system is designed for patients previously breathing room air spontaneously. We speculated that they will not require increased oxygen concentration because airway resistance reduction and improved gas exchange are expected immediately after heliox therapy initiation . Therefore, we conducted all calculations using helium concentration of 80 %.
In some patients, multiple masks may be used in order to find a mask that properly fits and is comfortable for the patient. This fact increases costs of consumables and costs of sterilization. These extra costs have a negligible effect on the results of the study. Considering that 20 % of patients may require multiple masks, our cost analysis does not change.
The costs of electricity in all the fours assessed systems are very low (between 0.02 – 0.05 EUR/hour) and thus inconsequential. Therefore, we did not included it in our analysis.
The medical staff should be present in the ward throughout the whole heliox therapy regardless of the system used for heliox administration. The same is true even when an alternative therapy is employed. Therefore, the personal costs of the medical staff are identical in all the evaluated systems and were therefore not considered in this study.
The conducted sensitivity analysis showed that the semi-closed circuit will be more advantageous if there is an increase in price of heliox. On the other hand, if the price of heliox decreases, a semi-closed circuit will still be beneficial but will require additional patients to recuperate the initial cost. However, decrease in price of heliox is unexpected due to the increasing prices of medicinal gases and due to the fact the world’s helium resources are limited .
Usage of a semi-closed circuit decreases the consumption of heliox and thus reduces the cost of heliox therapy. This might boost a wider use of heliox in clinical practice and support clinical studies devoted to heliox applications in various clinical situations . Despite physiologically favorable properties of heliox treatment for the patients with airway obstruction as compared to the air and oxygen treatment, there is still not sufficient evidence that it is suitable for the large scale use. Therefore, the impact of finding a theoretic cheaper way of heliox administration on the clinical practice needs to be ascertained.
Heliox therapy in spontaneously breathing patients using a semi-closed circuit becomes more cost-effective compared to the open circuit, currently used in clinical practice, when applied in a sufficient number of cases. This effect is enhanced with increasing number of patients treated.
The study was supported by grant IGA MZ CR No. NT11532 and by grant GS14/216/OHK4/3 T/17.
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