Pulmonary complications of congenital heart disease.

Cardiac and pulmonary pathophysiologies are closely interdependent, which makes the management of patients with congenital heart disease (CHD) all the more complex. Pulmonary complications of CHD can be structural due to compression causing airway malacia or atelectasis of the lung. Surgical repair of CHD can also result in structural trauma to the respiratory system, e.g., chylothorax, subglottic stenosis, or diaphragmatic paralysis. Disruption of the Starling forces in the pulmonary vascular system in certain types of CHD lead to alveolar-capillary membrane damage and pulmonary oedema. This in turn results in poorly compliant lungs with a restrictive lung function pattern that can deteriorate to cause hypoxemia. The circulation post single ventricle palliative surgery (the so called "Fontan circulation") poses a unique spectrum of pulmonary pathophysiology with restrictive lung function and a low pulmonary blood flow state that predisposes to thromboembolic complications and plastic bronchitis. As the population of patients surviving post CHD repair increases, the incidence of pulmonary complications has also increased and presents a unique cohort in both the paediatric and adult clinics.

Maximal static pressures and lung volumes in a child with Guillain-Barré syndrome ventilated by a cuirass respirator.

Serial maximal static pressure and lung volume measurements were made in a child with Guillain-Barré syndrome and respiratory failure. The patient received successfully ventilatory support for seven weeks with the use of a cycled negative-pressure cuirass-type respirator obviating prolonged intubation and tracheostomy. The fall in VC preceded the loss of respiratory muscle strength (RMS) and lagged behind RMS in the return towards normal values. There was a disproportionate loss of lung volume (lowest VC, 220 to 250 ml, 11 to 12 percent of normal) as compared to maximal static pressures (lowest PImax, 60 cm H2O, lowest PEmax, 47 cm H2O). The disproportion was greater than that previously reported in adults. The greater loss in lung volume may be due to greater chest wall compliance in the child, resulting in less outward recoil of the chest wall and subsequently more microatelectasis with denervation of the chest wall musculature. Loss of lung volume resulted in a smaller surface area over which the respiratory muscles exerted their force. Thus, pressure being equal to force divided by surface area, could be relatively maintained and not reflect the extent of the loss of muscle force.

Histamine challenge test in children using forced oscillation to measure total respiratory resistance.

This study analyzed the relationship between total respiratory resistance (Rrs) measured by forced oscillation technique and FEV1 during histamine provocation test in 31 children between seven and 17 years of age. Rrs was measured at frequencies between 6 (R6) and 26 Hz (R26). (R6-R26)/R26 was used as an index of frequency dependency of Rrs. A positive histamine test was defined as PC20 less than 8 mg/ml. Seventeen subjects had a positive test, and all of these had increases from baseline of R6 greater than 50 percent and (R6-R26)/R26 greater than 0.45. Of the 14 subjects whose PC20 was greater than 8 mg/ml, only two had changes in R6 and (R6-R26)/R26 of this magnitude. These two subjects had changes in FEV1 of 16 and 18 percent. There was a strong linear relationship between the changes in FEV1 and both R6 and (R6-R26)/R26 from baseline to the final value at the end of the test (r = 0.87 and 0.91 respectively). In conclusion, this study demonstrated that the evaluation of airway reactivity by histamine challenge may be done by forced oscillation technique. It is easy to administer and may allow testing of children unable to perform spirometry.

Effects of nutritional status on exercise performance in advanced cystic fibrosis.

Initial evaluation of 22 patients with cystic fibrosis (CF) on entry into a trial of home oxygen therapy was used to elucidate the possible effects of poor nutritional status on exercise performance in CF. The patients had advanced lung disease (mean FEV1, 36 percent predicted) and all had a stable resting PaO2 less than or equal to 65 mm Hg. Nutritional status was determined by calculating weight as a percentage of ideal for height (Wt/Ht) for each subject. Exercise testing consisted of a progressive exercise test on a cycle ergometer to measure maximum work capacity (Wmax), and a steady state test at 50 percent of baseline Wmax. During the steady state test, cardiac output (Q) and stroke volume (SV) were computed by the indirect Fick (CO2) method. Wmax, SV, Q and lung function results are expressed as percent predicted. Mean (+/- SD) Wmax was 58 +/- 15 percent predicted. Wmax correlated with both FEV1 and Wt/Ht, but FEV1 and Wt/Ht were not related. During steady state exercise, 12 of 22 patients had a SV less than 80 percent predicted. SV correlated with Wt/Ht, but not with lung function. Thirteen of the 22 patients had a Wt/Ht less than or equal to 90 percent and were considered malnourished. When compared with the well-nourished patients (Wt/Ht greater than 90%), these malnourished subjects had significantly lower mean values for Wmax%, SV% and Q% predicted, but not for lung function parameters. We conclude that: in patients with CF and advanced lung disease, nutritional status plays a significant role in determining exercise capacity; lower exercise tolerance of malnourished patients is an independent effect, as nutritional status and lung function were not related; and malnourished patients with CF have an altered cardiac performance on exercise testing which is due to a reduced SV rather than an impaired heart rate response.

Predictors of sunscreen use in childhood.

OBJECTIVE: To identify risk factors predictive of sunscreen use in children. DESIGN: Cross-sectional review of convenience sample. SETTING: Emergency department of a regional referral pediatric hospital. SUBJECTS: Nine hundred twenty-five parents of children presenting to the emergency department in August 1993. MAIN OUTCOME MEASURES: Parental risk factors assessed were use of sunscreen, tanning behaviors, previous blistering sunburn, knowledge of cancer risk related to sunburn and sun protection factor definition, education level, and other health-promoting behaviors. The parents were asked about perceived risk for their child's being sunburned in the next month or development of skin cancer in their lifetime, as well as an estimation of safe sun exposure time for their child. Child risk factors included a history of previous painful sunburn and parental assessment of their child's skin type based on susceptibility to sunburn. RESULTS: Eighty-four percent of parents reported that their children had used sunscreen at least once in the previous 2 months. The use of sunscreen in children younger than 1 year was 54%, from 1 to 12 years of age was 91%, and older than 12 years was 68%. Factors associated with increased likelihood of sunscreen use were age of 1 to 12 years, parental use of sunscreen, estimation of safe sun exposure of less than 30 minutes, description of child skin type as burns "sometimes," "easily," or "always," and correct definition of sun protection factor. Application of a multivariate model yielded a sensitivity of 96%, specificity of 36%, and positive predictive value of sunscreen use of 89%. CONCLUSIONS: Sunscreen use in parents is predictive of use in their children and relates more to experience with sunburn than with concerns about future skin cancer risk.

A new technique to demonstrate flow limitation in partial expiratory flow-volume curves in infants.

Partial expiratory flow-volume (PEFV) curves in infants are generated by applying a compressive pressure over the chest wall with an inflatable jacket. This study addresses two issues: pressure transmission to and across the chest wall and whether flow limitation can be identified. Eleven infants sedated with chloral hydrate were studied. Pressure transmission to the chest wall, measured with neonatal blood pressure cuffs placed on the infant's body surface, was 72 +/- 4% of jacket pressure during compression maneuvers. The pressure transmission to the air spaces, determined by measuring airway pressure during a compression maneuver against an occluded airway, was 56 +/- 6% of jacket pressure. A significant amount of the applied pressure is therefore lost across both the jacket and chest wall. Rapid pressure oscillations (RPO) were superimposed on static jacket pressures while expiratory flow was measured. Absence of associated oscillations of flow measured at the mouth was taken to indicate that flow was independent of driving pressure and therefore limited. Flow limitation was demonstrable with the RPO technique in all infants for jacket pressures greater than 50 cmH2O; however, it was evident at jacket pressures less than 30 cmH2O jacket pressure in four infants with obstructive airway disease. The RPO technique is a useful adjunct to the compression maneuver utilized to generate PEFV curves in infants because it facilitates the recognition of expiratory flow limitation.

Effect of changes in lung volume on respiratory system compliance in newborn infants.

Total respiratory system compliance (Crs) at volumes above the tidal volume (VT) was studied by use of the expiratory volume clamping (EVC) technique in 10 healthy sleeping unsedated newborn infants. Flow was measured with a pneumotachograph attached to a face mask and integrated to yield volume. Volume changes were confirmed by respiratory inductance plethysmography. Crs measured by EVC was compared with Crs during tidal breathing determined by the passive flow-volume (PFV) technique. Volume increases of approximately 75% VT were achieved with three to eight inspiratory efforts during expiratory occlusions. Crs above VT was consistently greater than during tidal breathing (P less than 0.0005). This increase in Crs likely reflects recruitment of lung units that are closed or atelectatic in the VT range. Within the VT range, Crs measured by PFV was compared with that obtained by the multiple-occlusion method (MO). PFV yielded greater values of Crs than MO (P less than 0.01). This may be due to braking of expiratory airflow after the release of an occlusion or nonlinearity of Crs. Thus both volume recruitment and airflow retardation may affect the measurement of Crs in unsedated newborn infants.

Tracheal stenting improves airway mechanics in infants with tracheobronchomalacia.

The compliance and expiratory resistance of the tracheobronchial tree is increased in infants with tracheobronchomalacia because of a weakness in cartilaginous support of the airway. Life threatening episodes may occur in these patients due to airway collapse. The goals of this study were to compare the effects on respiratory system mechanics of stenting the airway with either continuous positive airway pressure (CPAP) or a long tracheostomy tube. Five infants were studied: two had bronchopulmonary dysplasia (BPD), 2 had associated congenital anomalies, and one had tracheomalacia and polydactyly; none had a tracheoesophageal fistula. All patients required tracheostomy and were treated with CPAP. Lung mechanics were evaluated by measuring transpulmonary pressure, obtained by subtracting airway opening pressure from pleural pressure measured with an esophageal balloon, and flow measured with a pneumotachometer placed in series with the tracheostomy. Dynamic compliance (Cdyn) and total respiratory system resistance (Rt) were calculated by two-factor, least-mean-squares analysis, solving for the equation of motion of the lung with the PeDS system (MAS, Hatfield). In all subjects Cdyn increased and Rt decreased with increasing CPAP. In 4 subjects the airway was stented with a specially designed, long tracheostomy tube which reached to just above the carina; the special tube improved dynamic mechanics sufficiently to permit the discontinuation of CPAP. Speech was improved by fenestrating the tube and the use of a one-way inspiratory valve, placed over the tracheostomy. Inspiration occurred via the tracheostomy and expiration was directed to the larynx.

Maximal static pressures and lung volumes in young female swimmers: one year follow-up.

The relationship between the growth of lung volumes and the development of maximal static pressures was examined in a 1 year follow-up study of 17 female swimmers, initially less than 12 years of age. Lung volumes were measured by body plethysmography, and maximal static inspiratory and expiratory pressures were generated near residual volume, at functional residual capacity and near total lung capacity (TLC). The results were compared to the regressions obtained from cross-sectional data generated on 59 girls randomly selected from a local school. Height was similar in swimmers and controls. Vital capacity and total lung capacity increased during the year to exceed normal limits in 11 of 17 swimmers. The only significant increase of maximal static pressures during 1 year occurred in expiration near TLC in those swimmers initially less than 10 years of age, and all pressures fell within normal limits. We conclude that large lung volumes in swimmers cannot be accounted for by an increased ability to inflate and deflate the lung by the respiratory muscles.

Home oxygen delivery system for infants.

Home oxygen programs have evolved to facilitate the discharge of children who have bronchopulmonary dysplasia from neonatal intensive care units. This report describes a method of oxygen delivery for nighttime that is well suited to the home environment. It consists of an "inverted tent" that lines the walls and floor of the crib into which oxygen is flowed via an air entrainment device. This permits rapid equilibration of oxygen up to an FIO2 of 0.40 with a low flow oxygen source from a concentrator. The system is simple, safe, convenient, and economical.

Transvenous closure of patent ductus arteriosus in a sick 2780g infant.

A three-and-a-half-month-old 2780 g critically ill infant had successful transvenous coil occlusion of a ductus arteriosus. At six-and-a-half months of age the infant died, and autopsy showed coverage of the coil on the aortic aspect and no lumenal narrowing. It was concluded that transvenous coil occlusion of the patent ductus arteriosus in small infants is possible and that th venous route is preferred to be arterial route.

Disclosure of psychosocial concerns of young adults with advanced cystic fibrosis (CF) by a nurse home visiting program.

Twelve patients with advanced cystic fibrosis were enrolled over a 36 month interval in a trial to assess the effect of nocturnal home oxygen therapy. As part of this study, there were repeated home visits by the nurse. Immediately following a visit, the nurse encoded all spontaneous expressions of concern into three general categories: CF management, growth and development and family relations. During the first 6 months, the concerns focused on CF management and over the subsequent year were followed by concerns related to growth and development and, finally to family interactions. This pattern suggests a sequence to the types of interventions accepted by this population.

Abdominothoracic configuration and maximal static pressures in children.

The relationship of abdominothoracic configuration (AT config) to maximal static inspiratory and expiratory mouth pressure (Pimax, Pemax) was studied in 9 children. Pmax manoeuvres were performed from the relaxed end-expiratory position (FRC relax) and after contracting the abdomen (Abd) and expanding the rib cage (RC), (FRC isovol). Anteroposterior diameters (AP) of RC and Abd during Pmax were measured with magnetometers and compared to AT config at FRC relax. During both Pimax and Pemax from FRC relax the RC AP increased and Abd AP decreased. The pressures generated did not correlate with the change in either diameter. Moving to FRC isovol prior to the onset of pressure generation had no effect on AT config obtained for Pemax, but for Pimax resulted in further increase in RC AP and decrease in Abd AP as compared to FRC relax. Despite these differences in AT config, Pimax was not significantly affected. This suggests that changes in AT config expected to place the diaphragm at a mechanical advantage were countered by an opposite effect on the other inspiratory muscles. Because the AT config for Pemax was fixed, there appears to be a unique balance of forces between the expiratory muscles acting on the rib cage and the abdomen during a maximal static expiratory effort.

Maximal static pressures and lung volumes in young female swimmers.

The postulate that lung volumes are increased in swimmers because of a training effect that increases maximal static pressures (Pmax) thus augmenting the ability to inflate and deflate the lung was examined by comparing 38 competitively trained female swimmers to 59 controls between 7 and 13 years of age. Maximal static pressures on inspiration and expiration were generated near residual volume (RV), at functional residual capacity (FRC) and near total lung capacity (TLC). Lung volumes were measured by body plethysmography. The expected increase in lung volumes was present in the swimmers and was most marked in the oldest subjects. However, training did not have the anticipated effect on Pmax. In the younger swimmers training was associated with an increase in Pmax, but in the older swimmers Pmax was actually decreased in comparison to controls. These findings suggest that training may directly enhance lung growth, since the changes in lung volume cannot be accounted for by increases in respiratory muscle strength.

How to modify a volume-cycled home ventilator to satisfy a child's need for pressure-limiting and continuous positive airway pressure during spontaneous breathing.

Piston driven volume-cycled home ventilators increase work of breathing in the synchronized intermittent mandatory ventilation mode. A 2-year-old trisomy 21 patient with chronic lung disease due to recurrent aspiration pneumonia required a ventilator rate of 6-8 breaths per minute awake and 15 asleep, with peak pressure of 32 cm H2O and positive end-expiratory pressure (PEEP) of 10 cm H2O. Two circuits were designed to facilitate breathing and respiratory mechanics of his spontaneous breaths on both were compared. A spring valve on the inspiratory line pressure-limited ventilation and at the end of the expiratory line provided PEEP in both systems. The reservoir system had a 2-liter bag on the inspiratory limb of the circuit, and two one-way valves at the patient connector to direct inspiratory and expiratory flow. The continuous positive airway pressure (CPAP) system provided continuous flow with a CPAP device set to deliver a pressure 2 cmH2O higher than the PEEP valve. On the CPAP system, compared to the reservoir system, dynamic compliance was greater [1.52 (0.14 SD) ml/cm H2O/kg vs. 0.39 (0.02), p < 0.001] and resistance less [8.15 (1.26) cm H2O/l/s vs. 45.86 (0.87), p < 0.001] as measured with a PeDS machine. This is an innovative use of a CPAP device.

Maximal static pressures in healthy children.

Maximal static pressures (Pmax) were measured at the mouth in 119 Caucasian school children aged 7-13 years. Lung volumes were determined by body plethysmography. Pressures were generated near RV, at FRC and near TLC. As in adults, inspiratory Pmax decreased with increasing lung volume, whereas expiratory Pmax increased. At all lung volumes expiratory and inspiratory Pmax increased with age and were greater in males than females. Net respiratory muscle force was derived from the product of pressure and surface area (SA) over which pressure was applied. SA was estimated at different lung volumes on the basis of chest wall measurements. The dimensions obtained were utilized to calculate the SA of a truncated cone. This model was shown to be appropriate at TLC and FRC, but not RV. Since both SA and Pmax increased with age, the derived forces, as compared with pressures, proportionally increased more with age. Thus changes in Pmax underestimated changes in force during growth.

Cough versus chest physiotherapy. A comparison of the acute effects on pulmonary function in patients with cystic fibrosis.

Vigorous cough was compared with complete chest physiotherapy by functional evaluation in 9 patients with cystic fibrosis who had moderate airways obstruction. Pulmonary function tests were performed before and 1 h after treatment on consecutive mornings. The time spent coughing and in sputum production were equivalent for both treatments. There were no significant differences in functional response to either treatment. Static lung volumes and flows at high lung volumes were not affected. The increases in maximal expiratory flows at 50 and 25% of the vital capacity were 14 +/- 10 SEM% and 22 +/- 11 SEM%, respectively, after cough and 18 +/- 8% and 25 +/- 13% after chest physiotherapy. These responses did not correlate with the volume of sputum produced. Because there was no clear-cut benefit of chest physiotherapy over cough alone, and the latter is easier to perform, cough is an attractive alternate method of treatment.

Effects of airway occlusion at functional residual capacity in pentobarbital-anesthetized kittens.

The effects or airway occlusion at the end of inspiration on timing parameters and the "integrated" phrenic activity were studied in 1- to 21-day-old kittens at two levels of pentobarbital anesthesia before and after bilateral vagotomy. In intact kittens during the first 2 wk of life, instead of the classical effects of airway occlusion at functional residual capacity (FRC), shortening of both inspiration and expiration, a decrease in amplitude and rate of rise of the integrated phrenic activity, or augmented breaths were recorded. These effects were not altered by an additional dose of pentobarbital sodium. In kittens of all ages, airway occlusion performed after bilateral vagotomy had no significant effects on either timing and phrenic activity. Therefore, vagally mediated reflexes are probably responsible for the paradoxical effects of airway occlusion at FRC. However, a possible contribution of the chest wall receptors cannot be excluded.