THE EFFECT OF BREATHING 40 PER CENT OXYGEN ON THE ARTERIAL BLOOD GAS TENSIONS OF BABIES WITH BRONCHIOLITIS

Bronchiolitis

Everyone on the planet is exposed to respiratory syncytial virus (RSV) infection by the age of 2 years. Most infants admitted to the pediatric intensive care unit (PICU) for respiratory support during this infection are previously healthy, but their principal risk for needing PICU treatment is young age. That is, if you are born in October/November in the northern hemisphere, then your first winter exposure to RSV is likely to be when you are less than 4 months of age and vulnerable because of poor respiratory mechanical reserve (Alonso et al. 2007). However, if you are born in May/June, then you will be 7–8 months during your first winter exposure to RSV, much bigger and stronger and have more efficient thoracic and diaphragmatic mechanics. In the PICU, the main predictors of severe outcome in previously well infants appear to be young age, presence of apnea, and pulmonary consolidation on admission chest radiograph (Tasker et al. 2000; Lopez Guinea et al. 2007). Taken together, we can say that more severe RSV bronchiolitis in PICU practice is typically a problem of pulmonary consolidation, poor respiratory mechanics, and poor reserve, in the younger infant.

Bronchiolitis: assessment and evidence-based management

Viral bronchiolitis is the commonest cause of hospital admission in young infants. Respiratory syncytial virus is responsible for most cases of bronchiolitis. Secondary bacterial infection is rare and antibiotics are seldom necessary. Most children with bronchiolitis develop only mild illness and can be managed at home. Infants born prematurely, those with pre-existing cardiac or respiratory disease, and infants in the first three months of life are more likely to need hospital admission. On current evidence, nebulised adrenaline, inhaled and systemic corticosteroids, and inhaled bronchodilators do not have a role in the routine management of infants with bronchiolitis.

Hypoxaemia in young Kenyan children with acute lower respiratory infection

OBJECTIVES

To determine the prevalence, clinical correlates, and outcome of hypoxaemia in acutely ill children with respiratory symptoms.

DESIGN

Prospective observational study.

SETTING

Paediatric casualty ward of a referral hospital at 1670 m altitude in Nairobi, Kenya.

SUBJECTS

256 Infants and children under 3 years of age with symptoms of respiratory infection.

MAIN OUTCOME MEASURES

Prevalence of hypoxaemia, defined as arterial oxygen saturation < 90% determined by pulse oximetry, and condition of patient on the fifth day after admission.

RESULTS

Over half (151) of the children were hypoxaemic, and short term mortality was 4.3 times greater in these children. In contrast, the relative risk of a fatal outcome in children with radiographic pneumonia was only 1.03 times that of children without radiographic pneumonia. A logistic regression model showed that in 3-11 month old infants a respiratory rate > or = 70/min, grunting, and retractions were the best independent clinical signs for the prediction of hypoxaemia. In the older children a respiratory rate of > or = 60/min was the single best clinical predictor of hypoxaemia. The presence of hypoxaemia predicted radiographic pneumonia with a sensitivity of 71% and specificity of 55%.

CONCLUSIONS

Over half the children presenting to this referral hospital with respiratory symptoms were hypoxaemic. A group of specific clinical signs seem useful in predicting hypoxaemia. The clear association of hypoxaemia with mortality suggests that the detection and effective treatment of hypoxaemia are important aspects of the clinical management of acute infections of the lower respiratory tract in children in hospital in developing regions.

Acute viral bronchiolitis in infancy: epidemiology and management

Acute bronchiolitis due to viral agents (RSV, parainfluenza, influenza, adenovirus) is a relatively frequent disease of infancy. Seasonal epidemic pattern have been recognized, and nosocomial infections in pediatric wards occur. Until age 2 years most children have experienced some form of airway disease attributable to RSV. Some patients require hospital treatment; about 15% of our patients had to be transferred to the intensive care unit. Bronchiolitis seems to be frequently the first manifestation of asthma and we found higher IgG antibody titers to viruses causing bronchiolitis in children with asthma than in controls. Retrospective analysis of the charts of 147 cases of bronchiolitis revealed considerable uncertainty regarding therapeutic concepts. Mainstays of conservative therapy include oxygen, adequate hydration (often IV), and sometimes bronchodilators (based on the clinical impression of effectiveness in the individual patient). Mist therapy and secretolytic agents remain popular, although no clinical effect has been demonstrated. Attention should be directed toward the relief of upper airway obstruction caused by swelling, secretions, and nasogastric tubes. Oxygen administration in infants with coexisting chronic airway disease (e.g., BPD) and bronchiolitis may cause CO2 retention. Bronchodilators can cause hypoxia and increase bronchial compressibility by reducing smooth muscle tone. However, in severe cases a trial under pulse oximetry control seems worthwhile. Steroids seem to bring no clinical improvement, except in infants with protracted wheezing after bronchiolitis and patients with preexisting BPD.

Lower airway obstruction in the PICU

Lower airway obstruction is one of the most frequent causes of admission to pediatric intensive care unit. A thorough understanding of the pathophysiology underlying the disease will lead to effective management and decreased mortality and morbidity.

Bronchial reactivity in infants in acute respiratory failure with viral bronchiolitis

Airway reactivity and the effects of bronchodilators in infants are controversial. We studied the response to bronchodilator treatment in 14 mechanically ventilated infants (mean age, 2.74 months; range, 0.6-5.9) in respiratory failure caused by respiratory syncytial virus (RSV)-associated bronchiolitis. Sixteen infants without lung disease, undergoing elective surgery, provided normal values. Maximum expiratory deflation flow-volume (DFV) curves were produced by manual inflation of the lungs with an anesthesia bag to a predetermined static airway pressure followed by rapid deflation with a negative airway pressure before and after administration of bronchodilator. At baseline, the bronchiolitis group had a forced vital capacity (FVC) of 34.5 +/- 3.6 ml/kg compared with 41.8 +/- 1.5 ml/kg in the normal group; maximum expiratory flow rate at 25% of FVC (MEF25) was 10.2 +/- 2.0 ml/kg/s compared with 27.3 +/- 2.0 ml/kg/s in the normal group. The clinical and radiologic impression was severe lower airway obstruction and air trapping. After administration of bronchodilator, FVC did not increase significantly, but MEF25isov increased by over 30% in 13 of 14 infants. Mean MEF25 increased by 148 +/- 43.2% to 21.7 +/- 3.9 ml/kg/s (P less than 0.02). These findings indicate that during the acute phase of severe RSV-positive bronchiolitis most infants have airway reactivity that responds positively to bronchodilator treatment.

Acute respiratory failure in bronchiolitis and pneumonia in infancy. Modes of presentation and treatment

The modes of presentation and the management of acute respiratory failure in 11 infants with severe lower respiratory tract infections (due to respiratory syncytial virus in eight) are described. Progressive respiratory difficulties leading to exhaustion, peripheral circulatory collapse, recurrent apnoeic attacks, or generalized convulsions were the main clinical presentations resulting in severe ventilatory failure. In nine infants preventilation carbon dioxide tensions exceeded 65 mm Hg. It seems likely that the use of intermittent positive-pressure ventilation in these patients contributed to the low mortality rate, less than 0.5%, from such illnesses during the 15-month study period.