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Bilevel positive airway pressure in the treatment of status asthmaticus in pediatrics
American Journal of Emergency Medicine (2007) 25, 6 – 9
www.elsevier.com/locate/ajem
Original Contribution
Bilevel positive airway pressure in the treatment of status asthmaticus in pediatrics Sara L. Beers MDa,b,*, Thomas J. Abramo MDa,b, Andrea Bracken RTT a,b, Robert A. Wiebe MDa,b a
University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA Pediatric Emergency Services, Children’s Medical Center Dallas, Dallas, TX 75235, USA
b
Received 2 September 2005; revised 27 June 2006; accepted 2 July 2006
Abstract Objectives: The aim of this study was to examine the safety, patient tolerance, and possible benefit of bilevel positive airway pressure (BiPAP) in conjunction with b-2 agonist therapy in the treatment of pediatric patients with status asthmaticus who were refractory to conventional medical therapy. Methods: This descriptive retrospective chart review examined all patients with the diagnosis of acute asthma treated with BiPAP in an urban academic pediatric emergency department (ED) from April 1, 2003, to August 31, 2004. Results: Eighty-three patients with status asthmaticus refractory to conventional pharmacological treatment were placed on BiPAP with b-2 agonist nebulization in the ED. The number of subjects tolerating BiPAP was 73 (88%) of 83 patients. All patients placed on BiPAP in the ED were initially designated for admission to the pediatric intensive care unit (PICU). However, only 78% (57/73) were actually admitted to the PICU. Sixteen patients on BiPAP were admitted to a ward service; of these patients, none were subsequently transferred to the PICU. In addition, there was an immediate improvement in subjects’ clinical status upon initiation of BiPAP, with 77% showing a decrease in respiratory rate, averaging 23.6% (range, 4%-50%), and 88% showing an improved oxygen saturation, averaging 6.6 percentage points (1-28 percentage points). There were no adverse events due to the use of BiPAP. Conclusions: These results suggest that the addition of BiPAP in treating pediatric status asthmaticus is safe and well tolerated. This intervention shows promise as a beneficial adjunct to conventional medical treatments. However, further prospective investigation is warranted to confirm these findings. D 2007 Elsevier Inc. All rights reserved.
1. Introduction * Corresponding author. University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235, USA. Tel.: +214 456 2014; fax: +214 456 8132. E-mail address: [email protected] (S.L. Beers). 0735-6757/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.ajem.2006.07.001
The National Institutes of Health guidelines recommend use of continuous or intermittent nebulized b-2 agonist medications and systemic corticosteroids to treat the symptoms of acute asthma [1]. However, approximately
BiPAP in the treatment of status asthmaticus in pediatrics 5% to 10% of patients with acute asthma fail to respond to this conventional therapy and become candidates for other treatment options [2]. When first-line treatment fails, clinicians often add other therapeutic modalities such as aerosolized anticholinergics or epinephrine, and intravenous magnesium, theophylline, or terbutaline. Mechanical airway support such as bilevel positive airway pressure (BiPAP) and, ultimately, intubation with mechanical ventilation can be used if all other medical management has failed. Using BiPAP to treat status asthmaticus is a concept that has its origin from intermittent positive pressure breathing (IPPB). Both IPPB and BiPAP are similar in that they both provide noninvasive positive pressure support. However, BiPAP expands on this concept with continuous flow alternating between a higher inspiratory pressure and a lower end-expiratory pressure. Previous studies have looked at the use of IPPB in patients with an acute asthma exacerbation receiving nebulized b-agonist therapy [3-12]. Most of these studies found no significant benefit with the use of IPPB [6-12]. The problem with these early studies was that the range in disease severity was varied and the studies were not controlled. However, 2 studies concluded there is evidence that in severe asthma failing to respond to other methods of b agonist inhalation, there is benefit of IPPB [3,5]. To date, the information available on the use of BiPAP to treat status asthmaticus in the pediatric population is a limited to a single brief report describing its use in 3 patients. This report in the intensive care setting expressed a positive outcome [13]. It has been our experience that pediatric patients with acute asthma who do not respond to conventional medical management benefit clinically from the implementation of BiPAP. Thus, the purpose of this investigation was to examine the safety, patient tolerance, and possible benefit of BiPAP in conjunction with b-2 agonist therapy in the treatment of pediatric patients with status asthmaticus who were refractory to conventional asthma therapy.
2. Methods The study was approved by the institutional review board of the University of Texas Southwestern Medical Center. The study population was drawn from patients seen in the emergency department (ED) of a large urban pediatric specialty hospital. Charts reviewed were those of all patients with the diagnosis of acute asthma treated with BiPAP from April 1, 2003, to August 31, 2004. These charts were retrospectively identified by reviewing the charts of all patients who were billed for BiPAP. Charts were then reviewed for subjects meeting the inclusion and exclusion criteria. BiPAP was implemented for the treatment of children with status asthmaticus who were in need of an escalation in treatment because they were refractory to conventional
7 medical management. The routine treatment for managing patients with acute asthma in our ED includes up to 3 treatments of inhaled albuterol (2.5 mg for children b10 kg; 5 mg for children N10 kg) and ipratroprium bromide (250 lg for children b10 kg; 500 lg for children N10 kg) and early administration of oral or intravenous corticosteroids (2 mg/kg, maximum 80 mg). If wheezing persists, an hour-long inhalation is provided (albuterol, 15-20 mg). Depending on the severity of respiratory distress, presence of hypoxemia, and clinical concern for respiratory failure, additional therapies used may have included intravenous magnesium sulfate, subcutaneous or intravenous terbutaline, and/or aerosolized epinephrine. It is this population of patients who failed our routine treatment and qualified for BiPAP therapy. In our ED we used nasal BiPAP with a mask that covers only the nose. The patients in this study received BiPAP from one of 2 machines, both made by Repironics (Carlsbad, CA): the S/T-D30 Ventilatory Support System or the BiPAP Vision Ventilatory Support System. All patients who received BiPAP also concurrently received continuous inhaled b-2 agonists. Patients were excluded from the study population if they had any comorbid illnesses including obstructive sleep apnea, congenital heart disease, sickle cell disease, tracheostomy, diabetic ketoacidosis, cystic fibrosis, bronchopulmonary dysplasia, or any chronic lung disease other than asthma. From the patient’s chart, the change in respiratory rate and oxygen saturation, the need for PICU admission, endotracheal intubation, patients admitted to the wards with later transfer to the PICU, duration of BiPAP treatment, tolerance for BiPAP therapy, and complications related to BiPAP use (aspiration, epistaxis, pneumomediastinum, or pneumothorax) were recorded. All of the charts were individually reviewed by the primary investigator. A descriptive analysis of the continuous and categorical data was performed using proportions, frequency distributions, and medians (25th and 75th quartiles). No statistical analysis was performed in this descriptive study.
3. Results Eighty-three patients with acute asthma were placed on BiPAP during the designated period. The median age was 8 years (25th quartile, 5 years; 75th quartile, 11 years) with a range of 2 to 17 years. Sixty-four percent were male. Average length of time on BiPAP was 5.8 hours. Subjects tolerating BiPAP were 73 (88%) of 83. For patients not tolerating BiPAP, intolerance was established within 10 minutes of the nasal mask application. Of the 10 patients not tolerating BiPAP, there were no documented complications. The median age of patients not tolerating BiPAP was 4.5 years (25th quartile, 4 years; 25th quartile, 10.25 years)
8 with a range of 2 to 11 years. In general, it was the younger subjects who did not tolerate BiPAP. Seventy-seven percent showed a decrease in respiratory rate, with an average decrease of 23.6% (range, 4%-50%). The remaining 23% had no change in their respiratory rate while on BiPAP. No patients had an increased respiratory rate while on BiPAP. Eighty-eight percent showed improved oxygen saturation, averaging 6.6 percentage points (1-28 percentage points). These patients with improvement in their oxygen saturation had oxygen saturations before BiPAP therapy of 76% to 99%, averaging 93%. The remaining 12% had no change in their oxygen saturation while on BiPAP. Patients with no change in the oxygen saturation had oxygen saturations before starting BiPAP of 94% to 100%, averaging 98%. No patients had a decrease in oxygen saturation while on BiPAP. Seventy-eight percent (57/73) were admitted to the PICU. Two required intubation. Sixteen patients (22%) were weaned off BiPAP in the ED and qualified for ward admission. None of these ward admissions were subsequently transferred to the PICU. There were no adverse outcomes such as aspiration, pneumothorax, pneumomediastinum, or epistaxis. There were no deaths.
4. Discussion Traditionally, there has been a fear of using BiPAP, particularly in the pediatric population, because of the potential complications. However, our series had no adverse outcomes or deaths. In addition, we showed in our study that BiPAP is very well tolerated with an almost 90% success rate, even in children as young as 2 years. The positive benefit of BiPAP can be attributed to the significant improvement in the child’s work of breathing, which then reduces the level of patient anxiety. The patients in this study received BiPAP from one of 2 machines, both made by Repironics. The respiratory therapists started with an inspired positive airway pressure of 10 cm H2O and an expired positive airway pressure of 5 cm H2O. The rise time and inspiratory time are adjusted for patient comfort. The inspiratory pressure is then adjusted to achieve an exhaled tidal volume of 6 to 9 mL/kg. We use a nasal mask and not a full face mask to reduce the risk of gastric insufflation, vomiting, and aspiration. For the full benefit of nasal BiPAP to be achieved, the child needs to close his or her mouth to maintain the positive pressure. We did not find this to be a problem because the children generally followed the simple instruction of closing their mouths while wearing the BiPAP mask. The in-line aerosolized b-2 agonists are introduced into the circuit between the whisper valve and nasal mask. This is a good location both to minimize the loss of medicine out of the circuit and to minimize adherence to the circuit tubing. There are many theories suggesting the mechanism by which BiPAP works to improve patients with acute asthma.
S.L. Beers et al. It is thought that the positive pressure decreases the workload of fatigued muscle groups used for inspiration, the diaphragm and accessory muscles [14]. The positive pressure of BiPAP relieves the patient’s need for autopositive end expiratory pressure (PEEP), thereby reducing the patient’s energy expenditure for exhalation [14]. In addition, positive pressure has a direct bronchodilator effect and recruits smaller airways and collapsed alveoli, which improves ventilation perfusion mismatch [14,15]. Positive pressure may also improve the delivery of bronchodilators to the smaller airways of the lung [16]. The need for endotracheal intubation and mechanical ventilation in this BiPAP cohort was very low, with only 2 of the 83 patients intubated. Complications associated with intubating a patient with acute severe asthma include sudden and/or prolonged severe bronchospasm barotrauma, pneumothorax, ventilator-induced lung injury, cardiovascular instability, and nosocomial infections [17-19]. BiPAP therapy shows promise as an adjunct to bridge the gap between maximum medical therapy and mechanical ventilation in patients with acute status asthmaticus who are in need of ventilatory support. This noninvasive means of airway support may decrease the need for intubation and mechanical ventilation, thus decreasing the incidence of associated complications. There are several limitations to this study. This is a retrospective chart review with no control group. In addition, the medical management before the initiation of BiPAP varied among study subjects. Although all subjects before starting BiPAP received routine care, some additionally received intravenous magnesium sulfate and/or intravenous terbutaline. Thus, it is difficult to discern between the effect of the BiPAP and the effect of the other interventions. Furthermore, the clinical decision to initiate BiPAP therapy may have differed among the attending physicians, as no clear indications for starting BiPAP was determined prospectively. Lastly, no clinical asthma score was documented to objectively document the severity of the clinical symptoms. However, the authors feel, as a physician group, that BiPAP therapy was only reserved for those patients with whom medical treatment was near its maximum. In conclusion, our investigation is the largest series of pediatric patients that examines the use of BiPAP in the treatment of status asthmaticus. Our findings suggest the use of BiPAP in conjunction with continuous nebulized b-2 agonist therapy is safe and well tolerated. In addition, it may be beneficial in treating acute status asthmaticus in the pediatric population because the subjects generally tolerated the BiPAP, had no complications, had improved oxygenation, and had a decrease in respiratory rate while receiving BiPAP. Because these results show promise, further scientific validation in the form of a prospective study is warranted to determine the true efficacy and safety of BiPAP in the treatment of pediatric status asthmaticus.
BiPAP in the treatment of status asthmaticus in pediatrics
References [1] National Institutes of Health. National Heart Lung and Blood Institute. Expert panel report 2: guidelines for the diagnosis and management of asthma 1997. [2] Busse WW, Banks-Schlegel S, Wenzel SE. Pathophysiology of severe asthma. J Allergy Clin Immunol 2000;106:1033 - 42. [3] Choo-Kang Y, Grant I. Comparison of two methods of administering bronchodilator aerosol to asthmatic patients. Br Med J 1975;2:119. [4] Cayton R, Webber B, Paterson J, et al. A comparison of salbutamol given by pressure packed aerosol or nebulization via IPPB in acute asthma. Br J Dis Chest 1978;72:222. [5] Webber B, Collins J, Branthwaite M. Severe acute asthma: a comparison of three methods of inhaling salbutamol. Br J Dis Chest 1982;76:69. [6] Chang N, Levinson H. The effect of a nebulized bronchodilator administered with or without intermittent positive pressure breathing on ventilatory function in children with cystic fibrosis and asthma. Am Rev Respir Dis 1972;106:867. [7] Webber B, Shenfield G, Paterson J. A comparison of three different techniques for giving nebulized albuterol to asthmatic patients. Am Rev Respir Dis 1974;109:293. [8] Shenfield G, Evans M, Paterson J. The effect of different nebulizers with and without intermittent positive pressure breathing on the absorption and metabolism of salbutamol. Br J Clin Pharmacol 1974;1:295. [9] Loren M, Chai H, Midlich D, et al. Comparison between simple nebulization and intermittent positive pressure breathing in asthmatic children with severe bronchospasm. Chest 1977;72:145.
9 [10] Campbell I, Hill A, Middleton H, et al. Intermittent positive pressure breathing. Br Med J 1978;1:1186. [11] Gupta S, Poddar S, Nath S. Aerosolized bronchodilator therapy with and without IPPB in bronchial asthma—a comparative evaluation. Indian J Chest Dis Allied Sci 1978;20:118. [12] Weber R, Petty W, Nelson H. Aerosolized terbutaline in asthmatics— comparison of dosage strength and method of administration. J Allergy Clin Immunol 1979;63:116. [13] Akingbola O, Simakajornboon N, Hadley E, et al. Noninvasive positive-pressure ventilation in pediatric status asthmaticus. Pediatr Crit Care Med 2002;3:181 - 4. [14] Trill P, McGuire J, Baden H. Noninvasive positive-pressure ventilation in children with lower airway obstruction. Pediatr Crit Care Med 2004;5:337 - 42. [15] Soroksky A, Stav D, Shpirer I. A pilot prospective, randomized, placebo-controlled trial of bilevel positive airway pressure in acute asthmatic attack. Chest 2003;123:1018 - 25. [16] Dolovich M, Killian D, Wolff R, et al. Pulmonary aerosol deposition in chronic bronchitis: intermittent positive pressure breathing versus quiet breathing. Am Rev Respir Dis 1977;115:397. [17] Roberts. Acute severe asthma: differences in therapies and outcomes among pediatric intensive care units. Crit Care Med 2002;30:581- 5. [18] Tuxen D. Detrimental effects of positive end-expiratory pressure during controlled mechanical ventilation of patients with severe airflow obstruction. Am Rev Respir Dis 1987;136:872 - 9. [19] Tuxen D, Lane S. The effects of ventilatory pattern on hyperinflation, airway pressures, and circulation in mechanical ventilation of patients with severe air-flow obstruction. Am Rev Respir Dis 1989;140:5 - 9.
www.elsevier.com/locate/ajem
Original Contribution
Bilevel positive airway pressure in the treatment of status asthmaticus in pediatrics Sara L. Beers MDa,b,*, Thomas J. Abramo MDa,b, Andrea Bracken RTT a,b, Robert A. Wiebe MDa,b a
University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA Pediatric Emergency Services, Children’s Medical Center Dallas, Dallas, TX 75235, USA
b
Received 2 September 2005; revised 27 June 2006; accepted 2 July 2006
Abstract Objectives: The aim of this study was to examine the safety, patient tolerance, and possible benefit of bilevel positive airway pressure (BiPAP) in conjunction with b-2 agonist therapy in the treatment of pediatric patients with status asthmaticus who were refractory to conventional medical therapy. Methods: This descriptive retrospective chart review examined all patients with the diagnosis of acute asthma treated with BiPAP in an urban academic pediatric emergency department (ED) from April 1, 2003, to August 31, 2004. Results: Eighty-three patients with status asthmaticus refractory to conventional pharmacological treatment were placed on BiPAP with b-2 agonist nebulization in the ED. The number of subjects tolerating BiPAP was 73 (88%) of 83 patients. All patients placed on BiPAP in the ED were initially designated for admission to the pediatric intensive care unit (PICU). However, only 78% (57/73) were actually admitted to the PICU. Sixteen patients on BiPAP were admitted to a ward service; of these patients, none were subsequently transferred to the PICU. In addition, there was an immediate improvement in subjects’ clinical status upon initiation of BiPAP, with 77% showing a decrease in respiratory rate, averaging 23.6% (range, 4%-50%), and 88% showing an improved oxygen saturation, averaging 6.6 percentage points (1-28 percentage points). There were no adverse events due to the use of BiPAP. Conclusions: These results suggest that the addition of BiPAP in treating pediatric status asthmaticus is safe and well tolerated. This intervention shows promise as a beneficial adjunct to conventional medical treatments. However, further prospective investigation is warranted to confirm these findings. D 2007 Elsevier Inc. All rights reserved.
1. Introduction * Corresponding author. University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75235, USA. Tel.: +214 456 2014; fax: +214 456 8132. E-mail address: [email protected] (S.L. Beers). 0735-6757/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.ajem.2006.07.001
The National Institutes of Health guidelines recommend use of continuous or intermittent nebulized b-2 agonist medications and systemic corticosteroids to treat the symptoms of acute asthma [1]. However, approximately
BiPAP in the treatment of status asthmaticus in pediatrics 5% to 10% of patients with acute asthma fail to respond to this conventional therapy and become candidates for other treatment options [2]. When first-line treatment fails, clinicians often add other therapeutic modalities such as aerosolized anticholinergics or epinephrine, and intravenous magnesium, theophylline, or terbutaline. Mechanical airway support such as bilevel positive airway pressure (BiPAP) and, ultimately, intubation with mechanical ventilation can be used if all other medical management has failed. Using BiPAP to treat status asthmaticus is a concept that has its origin from intermittent positive pressure breathing (IPPB). Both IPPB and BiPAP are similar in that they both provide noninvasive positive pressure support. However, BiPAP expands on this concept with continuous flow alternating between a higher inspiratory pressure and a lower end-expiratory pressure. Previous studies have looked at the use of IPPB in patients with an acute asthma exacerbation receiving nebulized b-agonist therapy [3-12]. Most of these studies found no significant benefit with the use of IPPB [6-12]. The problem with these early studies was that the range in disease severity was varied and the studies were not controlled. However, 2 studies concluded there is evidence that in severe asthma failing to respond to other methods of b agonist inhalation, there is benefit of IPPB [3,5]. To date, the information available on the use of BiPAP to treat status asthmaticus in the pediatric population is a limited to a single brief report describing its use in 3 patients. This report in the intensive care setting expressed a positive outcome [13]. It has been our experience that pediatric patients with acute asthma who do not respond to conventional medical management benefit clinically from the implementation of BiPAP. Thus, the purpose of this investigation was to examine the safety, patient tolerance, and possible benefit of BiPAP in conjunction with b-2 agonist therapy in the treatment of pediatric patients with status asthmaticus who were refractory to conventional asthma therapy.
2. Methods The study was approved by the institutional review board of the University of Texas Southwestern Medical Center. The study population was drawn from patients seen in the emergency department (ED) of a large urban pediatric specialty hospital. Charts reviewed were those of all patients with the diagnosis of acute asthma treated with BiPAP from April 1, 2003, to August 31, 2004. These charts were retrospectively identified by reviewing the charts of all patients who were billed for BiPAP. Charts were then reviewed for subjects meeting the inclusion and exclusion criteria. BiPAP was implemented for the treatment of children with status asthmaticus who were in need of an escalation in treatment because they were refractory to conventional
7 medical management. The routine treatment for managing patients with acute asthma in our ED includes up to 3 treatments of inhaled albuterol (2.5 mg for children b10 kg; 5 mg for children N10 kg) and ipratroprium bromide (250 lg for children b10 kg; 500 lg for children N10 kg) and early administration of oral or intravenous corticosteroids (2 mg/kg, maximum 80 mg). If wheezing persists, an hour-long inhalation is provided (albuterol, 15-20 mg). Depending on the severity of respiratory distress, presence of hypoxemia, and clinical concern for respiratory failure, additional therapies used may have included intravenous magnesium sulfate, subcutaneous or intravenous terbutaline, and/or aerosolized epinephrine. It is this population of patients who failed our routine treatment and qualified for BiPAP therapy. In our ED we used nasal BiPAP with a mask that covers only the nose. The patients in this study received BiPAP from one of 2 machines, both made by Repironics (Carlsbad, CA): the S/T-D30 Ventilatory Support System or the BiPAP Vision Ventilatory Support System. All patients who received BiPAP also concurrently received continuous inhaled b-2 agonists. Patients were excluded from the study population if they had any comorbid illnesses including obstructive sleep apnea, congenital heart disease, sickle cell disease, tracheostomy, diabetic ketoacidosis, cystic fibrosis, bronchopulmonary dysplasia, or any chronic lung disease other than asthma. From the patient’s chart, the change in respiratory rate and oxygen saturation, the need for PICU admission, endotracheal intubation, patients admitted to the wards with later transfer to the PICU, duration of BiPAP treatment, tolerance for BiPAP therapy, and complications related to BiPAP use (aspiration, epistaxis, pneumomediastinum, or pneumothorax) were recorded. All of the charts were individually reviewed by the primary investigator. A descriptive analysis of the continuous and categorical data was performed using proportions, frequency distributions, and medians (25th and 75th quartiles). No statistical analysis was performed in this descriptive study.
3. Results Eighty-three patients with acute asthma were placed on BiPAP during the designated period. The median age was 8 years (25th quartile, 5 years; 75th quartile, 11 years) with a range of 2 to 17 years. Sixty-four percent were male. Average length of time on BiPAP was 5.8 hours. Subjects tolerating BiPAP were 73 (88%) of 83. For patients not tolerating BiPAP, intolerance was established within 10 minutes of the nasal mask application. Of the 10 patients not tolerating BiPAP, there were no documented complications. The median age of patients not tolerating BiPAP was 4.5 years (25th quartile, 4 years; 25th quartile, 10.25 years)
8 with a range of 2 to 11 years. In general, it was the younger subjects who did not tolerate BiPAP. Seventy-seven percent showed a decrease in respiratory rate, with an average decrease of 23.6% (range, 4%-50%). The remaining 23% had no change in their respiratory rate while on BiPAP. No patients had an increased respiratory rate while on BiPAP. Eighty-eight percent showed improved oxygen saturation, averaging 6.6 percentage points (1-28 percentage points). These patients with improvement in their oxygen saturation had oxygen saturations before BiPAP therapy of 76% to 99%, averaging 93%. The remaining 12% had no change in their oxygen saturation while on BiPAP. Patients with no change in the oxygen saturation had oxygen saturations before starting BiPAP of 94% to 100%, averaging 98%. No patients had a decrease in oxygen saturation while on BiPAP. Seventy-eight percent (57/73) were admitted to the PICU. Two required intubation. Sixteen patients (22%) were weaned off BiPAP in the ED and qualified for ward admission. None of these ward admissions were subsequently transferred to the PICU. There were no adverse outcomes such as aspiration, pneumothorax, pneumomediastinum, or epistaxis. There were no deaths.
4. Discussion Traditionally, there has been a fear of using BiPAP, particularly in the pediatric population, because of the potential complications. However, our series had no adverse outcomes or deaths. In addition, we showed in our study that BiPAP is very well tolerated with an almost 90% success rate, even in children as young as 2 years. The positive benefit of BiPAP can be attributed to the significant improvement in the child’s work of breathing, which then reduces the level of patient anxiety. The patients in this study received BiPAP from one of 2 machines, both made by Repironics. The respiratory therapists started with an inspired positive airway pressure of 10 cm H2O and an expired positive airway pressure of 5 cm H2O. The rise time and inspiratory time are adjusted for patient comfort. The inspiratory pressure is then adjusted to achieve an exhaled tidal volume of 6 to 9 mL/kg. We use a nasal mask and not a full face mask to reduce the risk of gastric insufflation, vomiting, and aspiration. For the full benefit of nasal BiPAP to be achieved, the child needs to close his or her mouth to maintain the positive pressure. We did not find this to be a problem because the children generally followed the simple instruction of closing their mouths while wearing the BiPAP mask. The in-line aerosolized b-2 agonists are introduced into the circuit between the whisper valve and nasal mask. This is a good location both to minimize the loss of medicine out of the circuit and to minimize adherence to the circuit tubing. There are many theories suggesting the mechanism by which BiPAP works to improve patients with acute asthma.
S.L. Beers et al. It is thought that the positive pressure decreases the workload of fatigued muscle groups used for inspiration, the diaphragm and accessory muscles [14]. The positive pressure of BiPAP relieves the patient’s need for autopositive end expiratory pressure (PEEP), thereby reducing the patient’s energy expenditure for exhalation [14]. In addition, positive pressure has a direct bronchodilator effect and recruits smaller airways and collapsed alveoli, which improves ventilation perfusion mismatch [14,15]. Positive pressure may also improve the delivery of bronchodilators to the smaller airways of the lung [16]. The need for endotracheal intubation and mechanical ventilation in this BiPAP cohort was very low, with only 2 of the 83 patients intubated. Complications associated with intubating a patient with acute severe asthma include sudden and/or prolonged severe bronchospasm barotrauma, pneumothorax, ventilator-induced lung injury, cardiovascular instability, and nosocomial infections [17-19]. BiPAP therapy shows promise as an adjunct to bridge the gap between maximum medical therapy and mechanical ventilation in patients with acute status asthmaticus who are in need of ventilatory support. This noninvasive means of airway support may decrease the need for intubation and mechanical ventilation, thus decreasing the incidence of associated complications. There are several limitations to this study. This is a retrospective chart review with no control group. In addition, the medical management before the initiation of BiPAP varied among study subjects. Although all subjects before starting BiPAP received routine care, some additionally received intravenous magnesium sulfate and/or intravenous terbutaline. Thus, it is difficult to discern between the effect of the BiPAP and the effect of the other interventions. Furthermore, the clinical decision to initiate BiPAP therapy may have differed among the attending physicians, as no clear indications for starting BiPAP was determined prospectively. Lastly, no clinical asthma score was documented to objectively document the severity of the clinical symptoms. However, the authors feel, as a physician group, that BiPAP therapy was only reserved for those patients with whom medical treatment was near its maximum. In conclusion, our investigation is the largest series of pediatric patients that examines the use of BiPAP in the treatment of status asthmaticus. Our findings suggest the use of BiPAP in conjunction with continuous nebulized b-2 agonist therapy is safe and well tolerated. In addition, it may be beneficial in treating acute status asthmaticus in the pediatric population because the subjects generally tolerated the BiPAP, had no complications, had improved oxygenation, and had a decrease in respiratory rate while receiving BiPAP. Because these results show promise, further scientific validation in the form of a prospective study is warranted to determine the true efficacy and safety of BiPAP in the treatment of pediatric status asthmaticus.
BiPAP in the treatment of status asthmaticus in pediatrics
References [1] National Institutes of Health. National Heart Lung and Blood Institute. Expert panel report 2: guidelines for the diagnosis and management of asthma 1997. [2] Busse WW, Banks-Schlegel S, Wenzel SE. Pathophysiology of severe asthma. J Allergy Clin Immunol 2000;106:1033 - 42. [3] Choo-Kang Y, Grant I. Comparison of two methods of administering bronchodilator aerosol to asthmatic patients. Br Med J 1975;2:119. [4] Cayton R, Webber B, Paterson J, et al. A comparison of salbutamol given by pressure packed aerosol or nebulization via IPPB in acute asthma. Br J Dis Chest 1978;72:222. [5] Webber B, Collins J, Branthwaite M. Severe acute asthma: a comparison of three methods of inhaling salbutamol. Br J Dis Chest 1982;76:69. [6] Chang N, Levinson H. The effect of a nebulized bronchodilator administered with or without intermittent positive pressure breathing on ventilatory function in children with cystic fibrosis and asthma. Am Rev Respir Dis 1972;106:867. [7] Webber B, Shenfield G, Paterson J. A comparison of three different techniques for giving nebulized albuterol to asthmatic patients. Am Rev Respir Dis 1974;109:293. [8] Shenfield G, Evans M, Paterson J. The effect of different nebulizers with and without intermittent positive pressure breathing on the absorption and metabolism of salbutamol. Br J Clin Pharmacol 1974;1:295. [9] Loren M, Chai H, Midlich D, et al. Comparison between simple nebulization and intermittent positive pressure breathing in asthmatic children with severe bronchospasm. Chest 1977;72:145.
9 [10] Campbell I, Hill A, Middleton H, et al. Intermittent positive pressure breathing. Br Med J 1978;1:1186. [11] Gupta S, Poddar S, Nath S. Aerosolized bronchodilator therapy with and without IPPB in bronchial asthma—a comparative evaluation. Indian J Chest Dis Allied Sci 1978;20:118. [12] Weber R, Petty W, Nelson H. Aerosolized terbutaline in asthmatics— comparison of dosage strength and method of administration. J Allergy Clin Immunol 1979;63:116. [13] Akingbola O, Simakajornboon N, Hadley E, et al. Noninvasive positive-pressure ventilation in pediatric status asthmaticus. Pediatr Crit Care Med 2002;3:181 - 4. [14] Trill P, McGuire J, Baden H. Noninvasive positive-pressure ventilation in children with lower airway obstruction. Pediatr Crit Care Med 2004;5:337 - 42. [15] Soroksky A, Stav D, Shpirer I. A pilot prospective, randomized, placebo-controlled trial of bilevel positive airway pressure in acute asthmatic attack. Chest 2003;123:1018 - 25. [16] Dolovich M, Killian D, Wolff R, et al. Pulmonary aerosol deposition in chronic bronchitis: intermittent positive pressure breathing versus quiet breathing. Am Rev Respir Dis 1977;115:397. [17] Roberts. Acute severe asthma: differences in therapies and outcomes among pediatric intensive care units. Crit Care Med 2002;30:581- 5. [18] Tuxen D. Detrimental effects of positive end-expiratory pressure during controlled mechanical ventilation of patients with severe airflow obstruction. Am Rev Respir Dis 1987;136:872 - 9. [19] Tuxen D, Lane S. The effects of ventilatory pattern on hyperinflation, airway pressures, and circulation in mechanical ventilation of patients with severe air-flow obstruction. Am Rev Respir Dis 1989;140:5 - 9.