Noninvasive ventilation in acute respiratory failure from respiratory syncytial virus bronchiolitis

Abstracts

OBJETIVOS: Analisar se a ventilação não invasiva diminui a necessidade de intubação endotraqueal e se alterou a evolução clínica, relativamente a complicações infecciosas, da bronquiolite por vírus sincicial respiratório com insuficiência respiratória. MÉTODOS: Estudo retrospectivo de coortes: cohorte A, de crianças internadas na unidade de cuidados intensivos e especiais pediátrica antes da introdução da ventilação não invasiva (2003-2005); cohorte B, de crianças internadas após a introdução de ventilação não invasiva (2006-2008). Excluindo a ventilação não invasiva, a terapêutica de suporte foi igual nos dois grupos. Foram incluídas crianças com o diagnóstico de bronquiolite por vírus sincicial respiratório e insuficiência respiratória entre novembro 2003 e março 2008. Analisaram-se variáveis demográficas, clínicas e gasimétricas. RESULTADOS: Incluídas 162 crianças, 75% com idade <3 meses. Grupo A: 64 crianças; Grupo B: 98 (34 necessitaram de ventilação não invasiva). Ambos os grupos apresentaram distribuição semelhante relativamente à idade, antecedentes de prematuridade, cardiopatia congénita, paralisia cerebral e doença pulmonar crónica. Na admissão, os valores da gasimetria e o número de apneias não apresentaram diferenças estaticamente significativas nos dois grupos. No Grupo B, o número de crianças que necessitou de ventilação invasiva foi menor (Grupo A: 12 versus Grupo B: 7; p=0,02), verificando-se uma diminuição do número de casos de pneumonia bacteriana (Grupo A:19/64 versus Grupo B:12/98; p=0,008). Não se registou mortalidade. CONCLUSÃO: Neste trabalho, comparando crianças com a mesma patologia, antes e depois da introdução de ventilação não invasiva como apoio ventilatório inicial, verificou-se diminuição das complicações infecciosas e da necessidade de entubação.

Bronquiolite; Vírus sincicial respiratório humano; Pressão positiva contínua nas vias aéreas

ORIGINAL ARTICLE

Noninvasive ventilation in acute respiratory failure from respiratory syncytial virus bronchiolitis

Zahara Nizarali^I; Marta Cabral^I; Catarina Silvestre^II; Clara Abadesso^II; Pedro Nunes^II; Helena Loureiro^II; Helena Almeida^II

^IDepartment of Pediatrics, Hospital Professor Doutor Fernando Fonseca - Amadora, Portugal

^IIPediatric Intensive and Special Care Unit, Hospital Professor Doutor Fernando Fonseca - Amadora, Portugal

Corresponding author

ABSTRACT

OBJECTIVES: The present study focused on respiratory syncytial virus bronchiolitis with respiratory failure. The aim of the study was to determine whether noninvasive ventilation reduces the need for endotracheal intubation or slows the clinical progression of acute respiratory syncytial virus bronchiolitis by reducing the incidence of infectious complications.

METHODS: The present study was a retrospective cohort study. Cohort A was comprised of children who were admitted to the pediatric intensive and special care unit from 2003-2005 before starting noninvasive ventilation; cohort B was comprised of children who were admitted to the pediatric intensive and special care unit from 2006-2008 after starting noninvasive ventilation. With the exception of noninvasive ventilation, the therapeutic support was the same for the two groups. All children who were diagnosed with respiratory syncytial virus bronchiolitis and respiratory failure between November 2003 and March 2008 were included in the cohort. Demographic, clinical and blood gas variables were analyzed.

RESULTS: A total of 162 children were included; 75% of the subjects were less than 3 months old. Group A included 64 children, and group B included 98 children. In group B, 34 of the children required noninvasive ventilation. The distributions of the variables age, preterm birth, congenital heart disease, cerebral palsy and chronic lung disease were similar between the two groups. On admission, the data for blood gas analysis and the number of apneas were not significantly different between the groups. In group B, fewer children required invasive ventilation (group A: 12/64 versus group B: 7/98; p=0.02), and there was a reduction in the number of cases of bacterial pneumonia (group A: 19/64 versus group B: 12/98; p=0.008). There was no record of mortality in either of the groups.

CONCLUSION: By comparing children with the same disease both before and after noninvasive ventilation was used for ventilation support, we verified a reduction in infectious complications and cases requiring intubation.

Keywords: Bronchiolitis; Respiratory syncytial virus, human; Continuous positive airway pressure

INTRODUCTION

Bronchiolitis is the most common lower respiratory tract infection in infants,⁽¹⁾ and the respiratory syncytial virus (RSV) is its most common agent.^(2,3) There is generally a positive outcome: from 1 to 5% of cases are admitted to inpatient care, and 1.8 to 2.7% of cases are admitted to intensive care units.⁽⁴⁾ In its most severe form, bronchiolitis leads to respiratory failure, requires mechanical ventilation⁽¹⁾ and is an important cause of morbidity and mortality.

The treatment options for bronchiolitis are scant.^(5,6) With the exception of support therapy, including oxygen delivery and mechanical ventilation, there is no scientific evidence to support the use of any treatment.^(6,7)

In recent years, noninvasive ventilation (NIV) has become an important alternative to respiratory support treatment for children with acute respiratory failure.^(8,9) In the United States, NIV was used in children beginning in the early 1990s, and the use of NIV has subsequently spread.⁽¹⁰⁾ In theory, the use of NIV in respiratory failure allows for the recruitment of collapsed or non-ventilated alveoli, increases the functional residual capacity, improves the ventilation/perfusion ratio, optimizes respiratory dynamics, reduces the respiratory load and improves gas exchange.⁽¹¹⁾

McNamara et al. described an improvement in RSV bronchiolitis-related apneas with the use of continuous positive airway pressure (CPAP).⁽¹²⁾ Using such clinical parameters as respiratory rate, heart rate and blood gas analysis, Nunes et al. verified the effectiveness of NIV beginning at the first hour of use.⁽¹³⁾ In two recent French studies, the success rate of NIV in bronchiolitis varied from 75 to 83%.^(14,15)

While several studies have demonstrated the efficacy of NIV in bronchiolitis, the present study evaluated the efficacy of NIV in a specific disease group: RSV bronchiolitis. The exclusion of the remaining disease agents allowed the comparison of cohesive and overlapping samples.

The objective of this study was to determine whether NIV reduces the need for endotracheal intubation or facilitates the clinical progression of children with acute RSV bronchiolitis by reducing the incidence of infectious complications.

METHODS

This study was conducted in a multidisciplinary pediatric intensive and special care unit (UCIEP) at the Hospital Professor Doutor Fernando Fonseca in Portugal. The UCIEP is a mixed medical and surgical unit that admits patients from the first weeks of life to 18 years of age. Patients are typically transferred from the emergency room, pediatric ward, operating room or from other hospitals. The unit has a maximum capacity of 11 patients.

Between November 2003 and March 2008, all children who were admitted to the UCIEP with the diagnosis of RSV bronchiolitis and respiratory failure were included in the study. At the time of the study, ethics committee approval was not required for retrospective studies in Portugal.

The study relied on a longitudinal retrospective design. Two cohorts were used to compare treatment protocols: cohort A was comprised of children who were admitted between January 2003 and December 2005 when NIV was not used, while cohort B was comprised of children who were admitted between November 2006 and March 2008 when the treatment protocol included the use of NIV as the first choice for ventilation support.

Treatment in both groups included oxygen and aerosol therapy with bronchodilators (albuterol) and/or saline. In agitated patients, chloral hydrate (30 to 50 mg/kg) and midazolam (0.1 mg/kg) were used for sedation. Corticosteroids were not used. Chest physiotherapy was conducted to assist in the elimination of respiratory secretions. When possible, nutritional support was provided through enteral feeding with a nasojejunal or orojejunal feeding tube (Table 1).

Bronchiolitis was defined as respiratory signs and symptoms consisting of coughing, tachypnea, chest retraction and wheezes or crackles on pulmonary auscultation, with no consolidation in a chest radiography. It may or may not include fever.

Respiratory failure was defined as a transcutaneous oxygen (O₂) saturation lower than 92% when breathing air or carbon dioxide (CO₂) with a partial pressure of less than 55 mmHg in a capillary blood gas analysis.

To estimate oxygenation, the ratio between pulse oximetry (SatO₂) and the fraction of inspired oxygen (FiO₂) was calculated. This ratio provides a noninvasive alternative to the oxygenation index (arterial oxygen pressure, PaO₂/FiO₂).⁽¹⁶⁾

RSV infection was diagnosed with an immunochromatography test (Coris^®) by identifying the virus in respiratory secretions.

Acute respiratory failure or apneas were indications of NIV.

To establish NIV, the unit protocol was used based on the NIV protocol that was published by the Respiratory Group at the Spanish Society of Pediatric Intensive Care.⁽¹⁷⁾

For NIV, conventional ventilators (Drager Babylog 8000 plus^®) and specific ventilators (Respironics BiPAP Vision^®, Respironics BiPAP Harmony^®, Infant Flow Driver^® and Infant Flow Advance^®) were used. NIV was applied in CPAP or BiPAP (Bilevel Positive Airway Pressure) modes according to the child's age and the availability of a nasal mask, short binasal plug and nasopharyngeal tube (a cut endotracheal tube that is positioned in the nasopharynx).

When CPAP was used, the treatment began at 4 cmH₂O and was progressively increased according to the patient's need and tolerance. With BiPAP, an inspiratory pressure of 8 cmH₂O was added and was progressively increased at 2-cmH₂O intervals according to the patient's need and tolerance. FiO₂ was maintained at the level necessary to maintain saturations of greater than 94%. The variation in expiratory positive airway pressure (EPAP) and inspiratory positive airway pressure (IPAP) was maintained according to the clinical and blood gas analysis progression. A minimum respiratory frequency of 10 to 30 cycles per minute was maintained according to the child's age.

In group A, the indications for invasive mechanical ventilation were acute respiratory failure or apneas. In group B, mechanical ventilation was used when NIV failed. NIV failure was defined as a lack of improvement or deterioration in the blood gas analysis parameters or the clinical state.

The diagnosis of bacterial co-infection was based on the presence of at least two of the following criteria: a fever of more than 38ºC, an increased C-reactive protein of greater than 5 mg/dL and a white blood cell count of greater than 15,000 mm³. These criteria were also used to begin antibiotic treatment.

Bacterial pneumonia was considered when the diagnosis of bacterial co-infection involved consolidation in a chest radiography.

Demographic, clinical and blood gas variables were analyzed. For the statistical analysis, quantitative variables were expressed as means and standard deviations or medians and maximum/minimum values. For categorical variables, chi-square statistics and Fisher's exact tests were used; for continuous variables, Student's t tests were used. Statistical significance was set at p<0.05. The software Statistical Package for the Social Sciences (SPSS: SPSS Inc., Chicago, IL, USA) version 16 was used.

RESULTS

Between November 2003 and March 2008, 212 children were admitted to the UCIEP with the diagnosis of RSV bronchiolitis and acute respiratory failure; 46 of the children were not included in the study because their medical records were unavailable. Of the remaining 166 children, 4 were excluded from group B because they underwent mechanical ventilation with initial ventilation support for cardiorespiratory arrest. Cohort A included 64 children, and cohort B included 98 children. The total sample included 162 children (Figure 1).

A total of 125 children (75%) were older than 3 months, and 53.7% of the children were male. The mean weight was 5.261±2.430 kg (minimum: 2.280 kg; maximum: 13.0 kg; median: 4.440 kg).

Medical histories identified 28 cases of preterm birth (17.3%), 7 cases of congenital heart disease (4.3%), 4 cases of cerebral palsy (2.5%) and 7 cases of chronic lung disease (4.3%).

The distributions of the medical history variables and age were similar between the two cohorts (Table 1).

On admission, differences between the groups for blood gas analysis (pH, pCO₂), SatO₂/FiO₂ and the number of apneas were not statistically significant (Table 1).

The differences between the groups in the number of cases of respiratory failure were not statistically significant. These cases progressed to acute respiratory distress syndrome (ARDS) (group A: 3/64 versus group B: 11/98; p=0.12), pulmonary hypertension (group A: 1/64 versus group B: 0/98; p=0.39), hypotension (group A: 1/64 versus group B: 5/98; p=0.23) and the need for inotropic support (group A: 0/64 versus group B: 3/98; p=0.13) (Table 1).

In group A, 12 children were invasively ventilated. The reasons for ventilation were apneas in two cases (16.6%) and acute respiratory failure in ten cases (83.3%). In the cases of acute respiratory failure, one case involved pulmonary hypertension, and three cases involved ARDS. All children were younger than 6 months, and three were newborn infants. Four children (33.3%) were preterm, one child (8.3%) had chronic lung disease and two children (16.7%) had a congenital heart disease.

At the moment of intubation, a blood gas analysis showed an average pH of 7.22±0.10 (minimum: 7.12; maximum: 7.32), an average pCO₂ of 76.1±16.6 mmHg (minimum: 59.5; maximum: 92.7) and an average oxygenation (using SatO₂/FiO₂) of 3.12±0.86 (minimum: 2.26; maximum: 3.98). Two infants in group A had episodes of apneas.

In group B, 34 children (33.3%) were noninvasively ventilated (Table 2). In 31 children (91.1%), the indications for NIV were acute respiratory failure with or without apneas. Apneas were present in 3 children (8.8%).

All of the 34 children who underwent NIV were younger than 6 months, and 15 were newborn infants. Five children (14.7%) were preterm, three children (8.8%) had chronic lung disease, one child (2.9%) had a congenital heart disease and one child (2.9%) had cerebral palsy.

A blood gas analysis showed an average pH of 7.25±0.3 (minimum: 6.7; maximum: 7.25), an average PCO₂ of 69.1±14 mmHg (minimum: 46.8; maximum: 118) and an average SatO₂/FiO₂ of 2.8±0.99 (minimum: 0.86; maximum: 4.33). Ten infants presented episodes of apneas.

The most frequently applied ventilator mode was BiPAP (20 cases), which was applied through the Infant Flow Advance^® (11 cases), Respironics BiPAP Vision^® (7 cases) and Respironics BiPAP Harmony^® (2 cases). The CPAP modality was used in 14 cases through the Infant Flow Driver^® (13 cases) and the Drager Babylog 8000 plus^® (1 case). A nasopharyngeal tube was used only once, and a nasal interface (nasal mask or short binasal plug) was used in the remaining cases.

Invasive ventilation was necessary in 7 (20.5%) of the 34 children who underwent NIV. The indications for intubation were ARDS (2 cases), ARDS with hemodynamic instability (1 case), hemodynamic instability (3 cases) and cardiorespiratory arrest (1 case).

At the moment of intubation, these children presented an average pH of 7.17±0.24 (minimum: 6.93; maximum: 7.41), an average pCO₂ of 84.5±17.4 mmHg (minimum: 67.1; maximum: 101.9) and an average SatO₂/FiO₂ of 2.4±1.6 (minimum: 0.79; maximum: 4.0).

At the moment of intubation, the differences in the blood gas analysis and SatO₂/FiO₂ values between groups A and B were not statistically significant (Table 2).

In group B, the number of children who required invasive ventilation was significantly lower than the number in group A (group A: 12/64 versus group B: 7/98; p=0.02) (Table 2).

Regarding the response to treatment, the number of co-infections was similar in the two groups (group A: 15/46 versus group B: 12/98; p=0.08). However, in group B, there were fewer cases of bacterial pneumonia (group A: 19/64 versus group B: 12/98; p=0.008) (Table 2).

The average number of days of inpatient care at the UCIEP was 6.73±4.5 days (minimum: 1; maximum: 35). There were no statistically significant differences in the durations of inpatient care between the two groups (Table 2).

There was no record of mortality in either of the groups.

DISCUSSION

Since Akingbola et al.'s 1993 publication of the first paper about pediatric applications of NIV,⁽⁸⁾ many case reports and case series have been published, and there have been many positive results for the use of NIV in several situations of respiratory failure.^(6,13)

Several of these studies have been conducted in adults with chronic obstructive lung disease (COPD), and they have demonstrated that NIV can reduce the rate of bacterial lung infection and improve survival.^(18,19) Additionally, several studies have shown that NIV reduces the need for endotracheal intubation and the incidence of nosocomial infection.^(20-22) Intubation and invasive ventilation are associated with high morbidity, as they are associated with local tissue lesions, pneumonia and extensions of hospital stay. By avoiding intubation, NIV has the potential to avoid these problems. Contrary to invasive ventilation, NIV leaves the respiratory tract intact, which preserves defense mechanisms and allows the patient to eat, speak and eliminate secretions.⁽²³⁾

In the present study, two groups of children with the same disease and causal agent were compared. The only difference between the groups was that they had differential access to NIV. When NIV was used, the need for intubation and the incidence of infectious complications decreased.

The present results are not explained by the inclusion of more severe cases in group A. In fact, the risk factors for severe RSV infection are pre-existing factors;^(24,25) in the present sample, the distributions of age and the presence of preterm birth, chronic lung disease, a congenital heart defect and cerebral palsy were similar in the two groups. Additionally, there were no statistically significant differences between the groups in the severity criteria, including the blood gas analysis at admission, the presence of a bacterial co-infection or the progression to ARDS or hypotension.

The co-infection rates were consistent with previous studies (group A: 23.4% versus group B: 12.2%).^(26,27) The definitions of co-infection and bacterial pneumonia were based on clinical, laboratory and radiographic criteria, rather than microbiological criteria. However, the same criteria were used for both groups, and the absence of microbiological criteria is justified by the fact that identical criteria cannot be obtained for children who are invasively or noninvasively ventilated or who are not ventilated. Because the rate of bacterial co-infection was similar between the two groups at admission, the reduction of the number of children who were noninvasively ventilated most likely led to the occurrence of fewer infections related to the endotracheal tube.

The average duration of inpatient care at the UCIEP was similar to what has been described in other studies,⁽²⁶⁾ and there was no significant reduction in the number of days of inpatient care in group B. The length of hospital stay in children with bronchiolitis can be prolonged for several reasons, such as problems with feeding, social problems and variation in discharge criteria.

The main limitations of this study were its retrospective design with comparisons between historical cohorts, thus limiting data collection and the losses of medical records.

CONCLUSION

In cases of severe RSV bronchiolitis, NIV was effective and avoided the need for conventional mechanical ventilation in a significant number of patients. NIV reduced the number of patients with bacterial pneumonia. Thus, small infants with severe RSV bronchiolitis might benefit from the timely introduction of NIV.

REFERENCES

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Publication Dates

• Publication in this collection
  30 Jan 2013
• Date of issue
  Dec 2012

History

• Received
  02 Aug 2012
• Accepted
  03 Dec 2012