(Heliox) Mixture in Airway Obstruction

CASE REPORT

Helium-Oxigen (Heliox) mixture in airway obstruction

Cristina A.G. Ulhôa,1 Lyle Larner2

Abstract Objective: to demonstrate the effectiveness and the positive outcome of patients treated with helium- oxygen (heliox) mixture. Heliox has been used in patients with airway obstruction of different etiologies who do not respond to a conventional treatment with oxygen. Methods: report of four cases of patients who received heliox as treatment for airway obstruction. All of them presented good results, presenting almost no side effects during the treatment. Conclusion: Heliox is a promising treatment for severe airway obstructions, presenting positive outcomes in a short period of time, until the final treatment is established.

J Pediatr (Rio J) 2000; 76(1): 73-8: heliox, gas flow, airway obstruction.

Introduction The use of the helium-oxygen mixture (heliox) in cases The objective of presenting the following clinical cases of airway obstruction of different etiologies has become is to demonstrate that, in our service, we observed results increasingly frequent, presenting satisfactory results and similar to those presented in literature. being virtually free from side effects. Helium is a gas of low molecular weight; its main Heliox promotes a greater diffusion of oxygen through therapeutic property is its low density. Helium acts the airways, resulting in clinical and laboratory diminishing the resistance of gas flow by increasing the improvements within a short period of time, due to its low laminar flow and decreasing the turbulent flow. density and to the fact that it does not combine with active The use of heliox has become a palliative measure in the membranes. treatment of airway obstruction, with a quick response by This report was divided according to the airway anatomy the patient until a definitive treatment is established, or until and their respective pathologies. In all reviewed cases, the there is a natural outcome of the disease. authors showed excellent results treating their patients with heliox. Case 1 SH, female, 16 years old, presenting cerebral palsy, 1. Fellow, Neonatal Intensive Care Unit, University of California Los Angeles (UCLA), U.S.A.. admitted with aspiration pneumonia. Thoracic X-ray showed 2. Physical Therapist, UCLA, U.S.A. opacification of the entire right lung.

73 74 Jornal de Pediatria - Vol. 76, Nº1, 2000 Mistura de hélio-oxigênio (heliox) em obstrução... - Ulhôa CAG et alii

The patient was admitted to the children’s intensive care patient was directed to the emergency room, where he unit with important respiratory effort, RR= 52irpm, PCO2= presented an 80% oxygen saturation in 100% of O2 with a 65mmHg, and intercostal recession; the case evolved to mask, RR=60/min, gasometry displaying Ph=7.41, respiratory failure, and required endotracheal intubation PO2=37mmHg, PCO2=65mmHg, HCO3= 23meq/l, and (for 4 weeks) and venous therapy with antibiotics. BE=-1.2meq/l. The child received standard medication for After the extubation, the patient presented important the treatment of asthma, but did not show improvement. inspiratory stridor, and then she began to receive continuous Then, the patient was intubated and transferred to children’s nebulization with racemic epinephrine and venous corticoid; intensive care unit. Thoracic X-ray showed hyperinsufflation there was very little improvement in the clinical status. The and atelectasis at the left upper lobe. The patient remained patient remained presenting respiratory effort, with RR=35- stable, did not present any improvement. Terbutaline was then administered, as well as a continuous nebulization with 42/min and PaCO2=56-62 mmHg. albuterol, magnesium sulfate, and two doses of ketamine. We introduced heliox at 70/30 (70% helium : 30% Solumedrol and aminophylline were kept. Later, a transfer oxygen) with an inhaling mask. Clinical and laboratory to the medical center of the University of California was improvement occurred approximately 30 minutes later, solicited, so that the child could receive better care. with a decrease in the respiratory effort (RR=22-25/min), The patient was admitted to this service presenting a and an improvement in hypercapnia (PaCO2=40-45mmHg). Heliox was raised to 80/20 (80% helium : 20% oxygen), and severe clinical status, with rare wheezes and great ventilatory administered for 48 hours. After suspending heliox, the difficulty. He presented hypocalcemia and a decrease in patient was released from the intensive care unit. bicarbonate - both were corrected. Since his glucose level was high (375 mg/ml), he received a dose of insulin. He was kept in continuous sedation, receiving dopamine, cefuroxime (computed tomographic scan showed sinusitis, with an Case 2 increased production of mucus), and 60/40 heliox (60% DB, male, 3 months old. The patient presented history helium : 40% oxygen) through mechanical ventilation to of prematurity and bronchopulmonary dysplasia. improve gas exchanges, thus decreasing PaCO2. Initial Four days prior to admission, the child developed a viral gasometry indicated Ph=7.18, PaCO2=74mmHg, status, presenting nasal obstruction, respiratory distress, PaO2=70mmHg, HCO3=27meq/l, BE=-3meq/l, and O2 and laryngeal stridor; this status had worsened during the Sat=80%. Fifteen minutes after the administration of heliox, last 24 hours. We collected material from the oral and nasal gasometry showed Ph=7.32, PaCO2=35mmHg, cavities for culture. The assessment was positive for PaO2=58mmHg, HCO3=25meq/l, BE=+ 2meq/l, and O2 respiratory syncytial virus. Sat=93%. We started nebulization with racemic epinephrine, but The patient was kept intubated for 36 hours. After the patient did not respond. The child continued with extubation, he received 75/25 heliox, with an inhaling mask respiratory effort, intercostal recession and nasal flaring. during 12 hours. Later, he was dismissed from the intensive Laboratory exams presented arterial gasometry with acidosis, care unit. hypercapnia, and low saturation (Ph= 7.29, PaCO2= 65mmHg, PaO2=70mmHg, O2Sat=65-70%); so, mechanical ventilation was required at FiO2 0.7. The patient presented a slight improvement in hypercapnia; however, the low Case 4 saturation (80%) remained unchanged. We introduced heliox at 60/40 through mechanical ventilation, obtaining improved CB, female, 7 years old, consciously asthmatic. She was admitted to the hospital’s emergency room with a history of Ph (7.38), decreased PCO2 (40mmHg), and improved saturation (92%) in 1 hour. The patient remained intubated respiratory distress, cough and wheeze for the previous 24 for 7 days. After extubation, he received 80/20 heliox with hours. On physical exam, the patient presented RR=60/min an inhaling mask for 72 hours, without complications. The with the use of accessory respiratory muscles, accentuated patient was released from the intensive care unit 24 hours wheezes, and pulse oxymetry at 80% in room air. after the interruption of the use of heliox. The initial therapy was albuterol and venous methylprednisone at 2 mg/kg; nebulization was continually administered with albuterol at 0.6 mg/kg/h, and Case 3 methylprednisone dose at 1 mg/kg 6/6 h. MT, 10 years old, male, consciously asthmatic since the Arterial gasometry presented Ph=7.3, PCO2=50mmHg, age of 6, presenting a status of cough, mucus production, PO2=60mmHg, HCO3=25meq/l, BE=-2meq/l, and and wheezes for 1 week. Twenty-four hours prior to Sat=78%. admission, the patient began to present symptoms of The child was transferred to the pediatric intensive care respiratory distress and tiredness. He had been using albuterol unit for continuous monitoring and to begin therapy with three times a day, and Atrovent twice a day for 1 month. The 60/40 heliox (60% helium : 40% oxygen). Mistura de hélio-oxigênio (heliox) em obstrução... - Ulhôa CAG et alii Jornal de Pediatria - Vol. 76, Nº1, 2000 75

The patient started to receive nebulization with albuterol The use of heliox has demonstrated decrease in in the heliox mixture, instead of the standard oxygen and barotrauma, since the patient is ventilated with less volume nitrogen. After 30 minutes using heliox, a considerable and less pressure than in the conventional oxygen/nitrogen improvement was noticed in the respiratory frequency rate, mixture. Helium has also been used to improve the relation which fell to 30-35/min, and in the gasometry, which between ventilation/perforation, in order to equal both of 17 presented Ph=7.35, PCO2=38mmHg, PO2=65mmHg, them. HCO3=23meq/l, BE=0meq/l, and Sat=92%. The patient received heliox for 24 hours, and did not require mechanical ventilation. She was held in the intensive Side effects care unit for more than 24 hours, and then she was dismissed Heliox, despite all the advantages presented, must be to the ward. Dismissal occurred after 24 hours. carefully used, since the low density may reduce lung volume and increase intrapulmonary shunts.18,19 Also, helium has a high thermal conductivity, four or Comments five times higher than nitrogen. This may configure a risk Helium is a biologically inert gas of low molecular for hypothermia when its temperature is below 36 ºC.20 weight. It is insoluble in tissues at 1 atmosphere, and it does not react with biological membranes.1 Helium was discovered in 1895 by Ramsey, and later Heliox availability introduced to the medical community by Barach, in 1935, Helium is available in tanks of several sizes. It costs 2,3 aiming at treating airway obstruction. approximately 15 times more than oxygen. The main therapeutic property of helium is its low Helium can be connected to oxygen through an Y, density (0.179 micropoise) - compared with 1.293 of the air providing the desired quantity of heliox by adjusting both and, 1.429 of oxygen. Due to this low density, helium is gases. A ready-made mixture of these gases in a tank can 4 used to facilitate gas flow in narrow orifices. also be found in different concentrations. Reynolds’s number, defined as Re=pdV/m, indicates Helium must be moisturized and heated at body turbulent flow when the result goes over 2,000. In this temperature so that the patient does not lose heat, since - as equation, p indicates the density of the gas, d, the diameter, we mentioned before - helium has a high conductivity. v, the linear velocity of the gas, and m, the gas viscosity. Patients can receive heliox either being intubated or not. According to Reynolds’s number, the proportion between In nonintubated patients, the mixture must be supplied to kinetic power and viscosity indicates whether the flow is them in a way that the contact with room air is kept to a laminar or turbulent. Turbulent flow is said to occur when minimum, so that the mixture does not dilute. Patients may the result of this equation is higher than 2,000. Helium acts receive heliox by an inhaling mask, with a container for the reducing the gas flow resistance if compared to air or 5 mixture, unidirectional flow, and a small opening for oxygen, since it is known that helium increases laminar releasing carbon dioxide. Patients may also receive heliox flow and decreases turbulent flow due to its low density. In by a mask with continuous positive pressure. the absence of turbulent flow, helium improves flow and decreases the effort to breathe wherever an airway In intubated patients, the helium tank must be connected obstruction is found.6-9 in the place of the compressed air. In this case, the measure of FiO will not be exact, since the ventilator is calibrated In medicine, helium is used in association with oxygen; 2 to receive air and oxygen. Oxygen must be controlled. The therefore, the final density will depend on the percentage of running volume will not be exact either, since the measure both gases. The 80/20 heliox mixture (80% helium and 20% of the flow is set for oxygen and nitrogen, not for oxygen and oxygen) has a final density of 0.429 micropoise. This helium. mixture will be the least dense, and thus the one providing the greatest reduction in airflow resistance.10-12 In intubated patients, special attention must be given to the risk for thoracic expansion. Heliox rate must be high The breathing of 70/30 heliox mixture presents a lower enough so that the total airflow is adequate to satisfy and flow resistance than the breathing of any concentration of 13 exceed the minute volume needed by the patient. oxygen (in nitrogen), including a FiO2 of 1. The use of heliox in concentrations inferior to 60/40 has not been demonstrating a satisfactory therapeutic effect due to its high density.14,15 Heliox in the respiratory tract Helium increases the diffusion effect of carbon dioxide, Upper airways since it diffuses four or five times faster in an oxygen and Heliox is mainly used in cases of upper airway helium mixture than in a standard mixture of nitrogen and obstruction. Syrinskas et al.21 demonstrated the use of oxygen. For the same partial pressure, a larger amount of heliox in ten patients with upper airway obstruction of carbon dioxide will be eliminated with the use of heliox.16 different etiologies, including endotracheal post-intubation 76 Jornal de Pediatria - Vol. 76, Nº1, 2000 Mistura de hélio-oxigênio (heliox) em obstrução... - Ulhôa CAG et alii subglottic edema (n=4), post-radiotherapy obstruction (n=3), partially occluded, but it did not cause hypoxemia or and primary tumors of the airways (n=3). The result obtained bradycardia. by these authors with heliox was successful in nine out of the Heliox was introduced at 20% (20% helium : 80% ten patients. The success of the treatment was based on oxygen), and then gradually increased up to 80% (80% clinical and laboratory improvements. Clinically, patients helium : 20% oxygen). Tidal volume or ventilatory time presented a decrease in the respiratory rate, ventilation and remained unaltered; however, a progressive decrease of the saturation improvement, and a decrease in the use of rates of peak of inspiratory pressure and PaCO2 was observed accessory muscles. Laboratory evaluation was based on while the percentage of helium was being increased. This improvement in PaO2 and decrease in PaCO2. Seven out of change became statistically significant when the the ten patients included in the study did not need concentration of helium reached 60/80. The authors noticed endotracheal intubation, due to their satisfactory response that no hemodynamic alterations occurred in the studied to heliox. animals, including cardiac index, mean arterial pressure, Duncan22 showed the efficacy of heliox as a temporary volume, and cardiac compromise. therapy in patients with respiratory distress caused by post- Mizrahi et al.25 demonstrated the successful use of extubation or by a viral subglottic edema. Seven patients heliox in a 43 year-old patient presenting mediastinal were in this situation. The evaluation of these patients was Hodgkin’s disease compromising the airways by the based on respiratory sounds, degree of stridor, cough, enlargement of the hilar node. The authors noticed a intercostal recession and cyanosis. Patients initially received significant improvement in this patient, whose rates of the standard treatment with oxygen by a mask and racemic PaCO2 decreased after the introduction of heliox. The epinephrine, and did not present any response. Then, 80/20 mixture was used for 72 hours, and then the patient started heliox was introduced in replacement with oxygen and air. to receive radiotherapy, with the eventual resolution of Patients presented a significant clinical improvement, with enlarged nodes and respiratory symptoms. reduction of respiratory distress (7.9 +/- 0.4 to 3.9 +/- 0.3; Tobias13 demonstrated a significant improvement in the P<0.001), and PaCO 46 mmHg +/ - 3.9 to 40.4 mmHg +/ 2 respiratory function with the administration of heliox in a 4- - 2; respiratory rate 51 irpm+/-7 to 44.7 irpm+/-6.7). None month old child who presented anteroposterior obstruction of the patients needed mechanical ventilation. of the trachea, which was extended up to the carina 23 Kemper et al. obtained a similar result using heliox in (tracheomalacia), with positive diagnosis for respiratory the treatment of post-extubation stridor in patients with syncytial virus. This child was intubated and received 70/30 burns who presented lesions in the upper airways. Since this heliox through mechanical ventilation, presenting was the first report of heliox in burned patients, the same progressive improvement (clinical and laboratory), and group of authors is now working on a prospective, double- being extubated 5 days later. The child received 60/40 blind study to verify the efficacy of heliox in these group of heliox with an inhaling mask, and presented positive patients. evolution of the clinical status. The results found in our services are similar to those The use of heliox in the treatment of children with distal observed in the literature, with a 90% success rate. One airways is more restricted, since these pathologies are rare example of this is patient number 1, who presented a in this age group. significant gradual improvement in a short period of time.

Peripheral airways (bronchospasm) Distal airways (trachea and bronchi) Bronchospasm causes decrease in ventilation and Lu et al.24 demonstrated the successful use of heliox in perfusion, leading to hypoxia caused by difficulty in gas a 49 year-old patient with bronchogenic squamous cell exchanges. carcinoma, which led to an extrinsic obstruction. This patient was submitted to a right pneumectomy, and developed The use of helium, due to its low density, converts a condition that narrowed the left bronchial tree (4 mm in turbulent flow into laminar flow; in the absence of turbulent diameter). flow, helium improves flow and decreases respiratory effort in the bronchoconstricted areas, facilitating gas exchanges. During bronchoscopy, the patient progressively Helium improves the ventilation/perfusion ratio by equaling presented dyspnea, which evolved to respiratory failure, them.26,27 and required endotracheal intubation. Heliox was introduced at 70/30 (70% helium : 30% oxygen) through mechanical Carbon dioxide is diffused four or five times faster in an 28-30 ventilation with progressive increase of pulmonary heliox mixture than in conventional air and oxygen. ventilation, volume, and peak of inspiratory pressure. Several clinical studies have suggested the therapeutic The authors investigated these findings in an animal efficacy of helium in patients with status asthmaticus, since model. The study was performed with dogs of the Mongrel it allows beta-2 and corticoid to have enough time to act. breed. Six dogs underwent a ligature of the right pulmonary Kudukis et al.31 studied 18 patients with status artery and of the right lung. The left bronchial tree was asthmaticus who were being treated with continuous Mistura de hélio-oxigênio (heliox) em obstrução... - Ulhôa CAG et alii Jornal de Pediatria - Vol. 76, Nº1, 2000 77 inhalation of beta-agonist and methylprednisone. In a double- while breathing heliox. The change of peak inspiratory blind study, these patients were randomized in two groups: pressure was early noticed (2.5 minutes), with a maximal ten were treated with heliox, and eight, with oxygen and air. fall of PaCO2 registered at 22 minutes. Patients presented pulsus paradoxus greater than 15 mmHg. The results presented by the cited authors are similar to In all patients, data included pulsus paradoxus, those observed in our service, where, if the conventional respiratory rate, cardiac index, dyspnea score, and oxygen treatment for status asthmaticus does not present clinical or saturation. These values were obtained during the laboratory improvement, a 60/40 mixture of heliox is intervention and 15 minutes after it. In some patients, peak introduced to assist the treatment. We obtain positive results flows were measured before and after receiving heliox or in 85% of the cases, which has made it become a routine in oxygen and air. our service, as we observed in patients number 3 and 4. Anderson et al.35 evidenced that the deposition of The observed results showed that pulsus paradoxus (in medication particles in aerosol increases when a 50/50 mmHg) fell significantly from an initial mean value of 23.3 mixture of heliox is administered, compared to room air. +/- 6.8 to 10.6 +/- 2.8 in heliox breathing (P<0.001), and The authors concluded that the inhalation of drugs in heliox increased again to 18.5+/ -7.3 after heliox was suspended. has a favorable effect on patients with severe obstructive Peak flow increased 69.4%+/-12.8% during the use of disease of the airways. heliox (P<0.05). Paret et al.36 attested in a case report that the use of Dyspnea index decreased from a initial measure of 5.7 heliox presents benefic effect in the treatment of children +/- 1.3 to 1.9 +/- 1.7 with heliox breathing (P<0.0002), and with acute bronchiolitis secondary to respiratory syncytial increased again to 4.0+/- 0.5 after its cessation. virus. The use of heliox may prevent mechanical ventilation and reduce morbidity. In control patients, there was no significant difference in pulsus paradoxus or dyspnea at any time during the study A similar result was observed in patient number 2. The period. use of heliox in patients with diagnosis of respiratory syncytial virus has shown a great clinical and laboratory Mechanical ventilation was averted in three patients improvement in these patients, as well as a better evolution breathing heliox, due to the improvement in dyspnea; this of the disease. patients did not present side effects. The authors concluded that during acute status asthmaticus, patients who inhaled heliox significantly decreased pulsus paradoxus, increased peak flow, and Conclusion decreased the dyspnea index. Moreover, heliox reduced The heliox mixture has been presented as a new option respiratory effort, prevented respiratory failure, and also for patients who do not respond to conventional treatment the need for mechanical ventilation. with oxygen therapy. Kass et al.32 demonstrated the use of heliox in 12 Helium should be used as a palliative measure for the patients with status asthmaticus and respiratory acidosis treatment of airway obstruction of different etiologies. (Ph<7.35 and PaCO2>45mmHg). Five patients inhaled Presenting a quick response by the patient, the function heliox through a ventilator, and seven received it via of helium is to work as a temporary solution in these cases, facemask. The therapeutic result with heliox was the decrease until a definitive treatment is established, or until a natural of PaCO2 from 57.9 mmHg +/- 8.3 to 47.5 mmHg +/- 4.3, outcome of the disease occurs. and the increase of Ph from 7.23 +/- 0.07 to 7.32 +/- 0.04, which promoted a significant clinical improvement in these patients. Manthous et al.33 demonstrated that heliox improves References expiratory flow and decreases pulsus paradoxus while studying 27 adults with status asthmaticus. In the control 1. Downes JJ, Raphaely RC. Pediatric intensive care. Anesthesiology 1975;43:238-50. group, improvement in expiratory flow and decrease in 2. Barach AL. The therapeutic use of helium. JAMA 1936; pulsus paradoxus was also observed (using beta-agonist 107:1273-80. and corticoid), although a clinically significant improvement 3. Barach AL. The use of helium as a new therapeutic gas. Anesth was noticed only among patients breathing heliox. Analg 1935;14:210-13. 34 4. 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