Respirator Therapy Research Articles

Asymmetrical pulmonary changes in premature infants with surgical closure of a persistent ductus arteriosus

The chest radiographs of 57 premature infants admitted consecutively with hyaline membrane disease and receiving respirator therapy were reviewed, comparing right and left pulmonary abnormalities. Fifteen infants (Group I) did not develop a persistent ductus arteriosus (PDA). Forty-two infants developed a PDA, which was successfully treated with indomethacin in 17 infants (Group II), while in 25 infants (Group III) the ductus was closed surgically. Analysis of the three groups showed that infants who had undergone surgical closure of their PDA developed significantly more asymmetrical broncho-pulmonary damage. Statistically significant fewer radiological findings of broncho-pulmonary damage were found on the left side in comparison with the right side in the group treated surgically.

Knowledge base design for decision support in respirator therapy.

A knowledge base is built for decision support applied to respirator therapy (the KUSIVAR project). The knowledge representation is object-oriented using frames to store multiple forms of knowledge: variable descriptions, transformation tables, rules and mathematical models. The system is data-driven, generating and displaying advice automatically triggered by changes in data from the respirator and the patient. The inferenceing mechanism is forward-chaining i.e. a rule is evaluated as soon as it's condition is satisfied. Temporal aspects of the reasoning are represented by a number of mechanisms, among others limited validity times for data, trend analysis and mathematical models. The knowledge base is organized according to disease groups and decision situation which simplifies knowledge acquisition and improves response times since it enables the system to focus on a limited set of rules in each situation. To test the feasibility of the system design a prototype has been built using Knowledge Engineering Environment (KEE) from Intellicorp on an Explorer workstation from Unisys. The production system, which is interfaced to a Siemens Elema Servo Ventilator 900C, is currently being implemented under the Microsoft Windows multitasking environment on a microcomputer based on an Intel 80386 processor.

Assessment of patients' experience of discomforts during respirator therapy.

Patients (n = 158) who had been respirator-treated and who could remember the treatment were retrospectively (after greater than 2 months) interviewed about their experiences. Of all patients, 47% had felt anxiety and/or fear during the treatment. These feelings were intimately related to the experience of agony/panic (p less than .001) and insecurity (p less than .001). Inability to talk and communicate was found to be the dominating reason (p less than .001) for evoking such feelings and also made it difficult for the patients to sleep and rest (p less than .05); no correlation to pain was found. Difficulties to synchronize with the respirator in connection with suctioning also caused feelings of anxiety/fear (p less than .01), agony/panic (p less than .01), and insecurity (p less than .001). Even as long as 4 yr after respirator treatment, most patients (90%) who remember the treatment still recall the situation as unpleasant and stress-evoking. The isolation due to communication difficulties was a greater problem than direct airway-related nursing care activities. This relationship between communication difficulties and severe emotional reactions should be considered in the nursing care of respirator-treated patients.

Neurodevelopmental screening of in utero growth-retarded prematurely born children before school age.

As part of a prospective follow-up study of two premature cohorts (gestational age less than or equal to 36 weeks) born between 1976 and 1977, designed to evaluate the effects of IUGR on morbidity, mortality and neurological development in prematurely born children, 71 prematurely born children (48 AGA, 23 IUGR) without major neurological handicaps were subjected to detailed assessment of their neurological and psychological status at the age of 4 years. Thirty-six healthy full-term children formed a control group. The socioeconomic status of the families of the premature groups was similar to that of the families of the control group. The assessment consisted of a neurodevelopmental screening test and four psychological tests. Validation of the NDS test in relation to proven cognitive problems (sensitivity 96%, specificity 64%, relative risk 16.74) and determination of normal ranges were based on findings in the control group. There were significantly more children with moderate to high risk scores (greater than or equal to 10) among the IUGR group than among the AGA group. The neurodevelopmental profile of the preterm IUGR group was characterized by complex deviations of motor, visual and perceptual functions from normal. Preterm AGA children had only slightly higher risk scores in relation to fine motor, upper motor and perceptive functions than control children. Of the various perinatal factors studied, IUGR (especially in relation to boys who needed respirator therapy) was the most likely to be associated with abnormal NDS scores before school age.

Lung perforation by nasogastric feeding tubes

Endotracheal misdirection of narrow bore nasogastric feeding tubes resulted in perforation of the lung, pneumothorax and hydrothorax in two intensive care patients. Both were intubated with cuffed endotracheal low pressure tubes, one patient was on respirator therapy with neuromuscular relaxation. Feeding tubes were inserted by experienced personnel with the assistance of a steel stylet without difficulties. Aspiration of fluid was misinterpreted as proof of correct positioning, the liquid being however pleural effusion and not gastric juice. Similarly auscultation of gurgling sounds in the upper epigastrium was not a reliable sign of intragastric position. Insertion of nasoenteric feeding tubes may be complicated by perforation of the upper gastrointestinal tract and lung in poorly responsive pateints with cuffed endotracheal devices during neuromuscular blockage. In these patients a laryngoscope and forceps should be used to ensure free passage of the tube into the oesophagus. Röntgenographic confirmation of correct positioning of the tube immediately after insertion is mandatory.

Letters to the Editor

Thank you for your letter of inquiry about my article, "Treatment of Haemophilus influenzae Type B Epiglottitis" (Pediatrics 63:402, 1979). Only one child died in the series of 48 children. This child experienced a respiratory and cardiac arrest upon arrival at our hospital and could not be rapidly intubated. After successful intubation, the child failed to breathe spontaneously and required respirator therapy until she died three days later. In each case the respiratory arrests occurred prior to intubation and not during the procedure.

1307 RESPIRATORY INFECTIONS IN INFANTS ON MECHANICAL VENTILATION: THE IMMUNE RESPONSE AS A DIAGNOSTIC AID

Bronchial aspirates for bacterial and viral cultures and bronchial IgM were obtained weekly in 41 patients receiving artificial ventilation. Mean birth weight 1,680 grams ± 875grams GA 32.6 weeks ±4.4. The mean duration of ventilation was 28 days (maximum 137 days). Weekly blood samples were also obtained for serum IgM and hemagglutination antibodies against O antigens prepared from the patient's own microorganisms. Clinicoradiographic evidence of pneumonia was compared with the demonstration of specific immune responses (rise in titer of at least four fold) or a significant rise in serum or bronchial IgM levels. Significant specific immune response was documented in 24% of the patients studied. Altogether there were 35 clinicoradio-graphic pneumonic episodes. Abnormal serum IgM was found in 60%, bronchial IgM in 42% and specific antibodies in 34% of those episodes. Combining the three parameters studied pneumonia was documented in 30 out of the 35 purported episodes. Patients with severe bronchopulmonary dysplasia had significantly elevated levels of both bronchial (p <.001) or serum IgM (p <.001) even during asymptomatic periods. No correlation was found between paired samples of bronchial and serum IgM (r=0.16). The data on bronchial aspirate IgM are compatible with local production by the lung. We conclude that the immune response of the host is helpful in documenting respiratory infections in infants receiving prolonged respirator therapy.

1656 IMPROVEMEMT IN PULMONARY INTEPSTITIAL EMPHYSEMA WITH HIGH FREQUENCY VENTIIATION

We have used high frequency ventilation (8-12 Hz or 480-720 cycles/min) to treat five infants with severe pulmonary interstitial emphysema (PIE). All infants were recovering from severe respiratory distress syndrome when X-ray evidence of PIE and blood gas deterioration were noted. The infants had gestational ages of 28-32 weeks, birthweights of 1.0-1.7 kg, and were treated starting at 3-12 days of age. Four of the infants were maintained on the high frequency ventilator for approximately 48 hours, and one for 26 days. FIO2 averaged 0.74 and peak inspiratory pressure 38 cm H2O during conventional ventilation immediately prior to high frequency ventilation. All infants demonstrated prompt improvement in blood gases reaching an average 60 torr increase in PO2 and a 20 torr decrease in PCO2 within one hour. Peak pressure measured in the trachea near the carina fell from 38 to 20 cm H2O. All infants showed resolution of chest X-ray evidence of PIE. Attempts to reinstitute conventional respirator therapy resulted in reoccurrence of PIE in two cases. Two infants weaned rapidly from all respiratory support, one weaned slowly and two died after two days of initial improvement. We conclude that because of the low airway pressures required, high frequency ventilation can be life saving in the treatment of pulmonary interstitial emphysema.

The role of respirators in the etiology and pathogenesis of bronchopulmonary dysplasia

I N P R O P O S I N G T H E U S E o f the term bronchopulmonary dysplasia, Northway et al' described the occurrence of pulmonary disease following respirator therapy in hyaline membrane disease and proposed the appearance of a new chronic pulmonary syndrome associated with the use of intermittent positive pressure, respirators and high oxygen concentrations for a period exceeding 156 hours. A review of their material also indicates that the patients described were all managed with endotracheal tubes and that the choice of the 156-hour period was dictated simply by what the material itself contained rather than by any predirected time pattern. It is questionable, however, whether what was being described at that point was really a new disease or simply the recognition that respirators, by being able to prolong the course of hyaline membrane disease, were now allowing the appearance of the normal progression of severe cases of the disease, in that all of our previous experience had indicated either death or complete resolution of the changes without any permanent sequelae. There had been previous suggestions that sequelae from the natural course of the disease did occur, 2a and that complete pulmonary recovery could not always be expected, although in both of these instances the management of the infants had been complicated by both oxygen therapy and the use of respirators, thus making it difficult to ascribe these changes to the natural course of severe disease itself. That even mild cases could subsequently lead to both anatomic and functional sequelae in later life was subsequently demonstrated by the report of the occurrence of a much higher incidence of bronchiolitis at an early age in survivors of respiratory distress syndromer an incidence which seems to be independent of either the severity of the initial disease or of the existence of permanent radiographic changes, thus suggesting that functional sequelae and visible anatomic changes may or may not go together in all instances. The suggestion that this is specifically an occurrence confined to the newborn period may be open to question, since changes of similar nature have been described in adults managed with oxygen and positive pressure respirators?

Bronchopulmonary dysplasia: Possible relationship to pulmonary edema

The pathogenesis of bronchopulmonary dysplasia is controversial. Oxygen toxicity, mechanical trauma to the lung secondary to respirator therapy, and congestive heart failure with a left to right shunt through a patent ductus arteriosus have all been implicated. Our data suggest that in addition to these three conditions, all of which are edemagenic, infants with bronchopulmonary dysplasia have a significantly greater mean fluid intake in the first five days of life when compared with infants with respiratory distress syndrome or patent ductus arteriosus alone. We suggest that the addition of a fluid load may potentiate the effects of other factors and increase the risk of bronchopulmonary dysplasia in infants with respiratory distress syndrome who require respiratory support.

Diaphragmatic energy expenditure in chronic respiratory failure: The effect of assisted ventilation with body respirators

Patients with chronic respiratory failure secondary to disorders which increase the work of breathing often benefit from assisted ventilation with body respirators. To test the hypothesis that body respirator therapy works by relieving the respiratory muscles of an excessive load, we recorded diaphragmatic and/or accessory inspiratory muscle electrical activity before and during assisted ventilation in 11 patients. All patients had chronic hypercapnia; seven had advanced obstructive pulmonary disease and four had severe thoracic cage restriction. When these patients used the tank respirator, their diaphragmatic activity fell to 9 ± SD 3 per cent of the level measured during spontaneous breathing. The reduction was highly significant in each patient (P < 0.001). Similar reductions of diaphragmatic activity occurred in the cuirass respirator. The body respirators also reduced accessory muscle activity (P < 0.02). Coincident with loss of diaphragmatic activity, the patients obtained relief from dyspnea. These results were independent of changes in arterial blood carbon dioxide tension (PaC0 2). Seven normal subjects were studied to further investigate the mechanism by which body respirators reduced inspiratory muscle activity. In the tank, these subjects displayed only minor reductions of diaphragmatic activity despite large decrements in end-tidal carbon dioxide pressure (P ETCO 2). However, when their upper airway resistance was increased, diaphragmatic activity promptly ceased in the tank. We conclude that capture of the ventilatory cycle by the body respirator is facilitated by loading the inspiratory muscles. We suggest that the beneficial effects of body respirator therapy for chronic respiratory failure are mediated in part through reduction of excessive inspiratory muscle contractile effort.

Pneumatosis Intestinalis

AS MORE experience is gained with jejunoileal bypass, more unanticipated complications are being discovered. A complication not yet reported is pneumatosis intestinalis in the defunctionalized small-bowel segment. This complication occurred in one patient in our series. <h3>Report of a Case</h3> A 46-year-old man weighing 154.5 kg (340 lb) underwent jejunoileal bypass for morbid obesity. He had prior episodes of severe cardiopulmonary failure. No endocrine abnormalities were discovered during preoperative evaluation. Upper gastrointestinal and small-bowel roentgenographic series, barium enema examination, and oral cholecystogram were normal. After treatment of the cardiac and pulmonary failure with digitalis, diuretics, and respirator therapy, the patient underwent a jejunoileal bypass with 35.5 cm of jejunum, anastomosed end-to-end to the terminal 10 cm of ileum. The defunctionalized small-bowel segment was closed proximally and fixed to the root of the small-bowel mesentery, and the distal segment anastomosed end-to-side to the sigmoid colon. The postoperative course was complicated by

Orogastric supplementation in small premature infants requiring mechanical respiration.

Very small premature infants with severe respiratory disease were managed with early intermittent orogastric feedings combined with infusion of 10% dextrose. Nine infants weighing less than 1,350 gm at birth (mean, 990 gm) who required endotracheal intubation and respirator therapy and who remained in the hospital for at least 40 days were studied retrospectively. The mean weight gain per day was 10.8 gm for the first 40 days of life, 14.1 gm while an endotracheal tube was in place (sometimes longer than 40 days), and 15.7 gm during the growth phase, after initial weight loss. Individual growth curves compared favorably with those reported by others using total parenteral nutrition. The technique described deserves wider application for initial management of the small premature infant receiving mechanical respiration.

Asymmetric lung involvement in bronchopulmonary dysplasia.

The radiographic distribution of pulmonary abnormalities in bronchopulmonary dysplasia (BPD) in all previously reported cases has been bilateral and generalized. The authors studied 11 premature infants who had BPD that was primarily unilateral. The striking feature in each of these patients was the occurrence of an episode of prolonged unilateral atelectasis or tension pneumathorax. Few, if any, radiographic manifestations of BPD developed. Results of a detailed analysis of oxygen exposure and respirator therapy during the periods of unequal lung ventilation further characterizes the protective effect of atelectasis and tension pneumothorax in the development of BPD.

Acute Poisoning with Dextropropoxyphene

Out of 14 cases of poisoning assumed to be due to dextropropoxyphene-containing drugs, propoxyphene and its main metabolite norpropoxyphene could be demonstrated in 11. The concentrations of the drugs were determined shortly after admission and then after 2, 4, 6 and 10 hours (in four cases also after 16 hours). The highest plasma concentration of propoxyphene, 0.74 mug/ml, was found in one case of fatal poisoning. Another patient with a plasma concentration of 0.51 mug/ml showed signs of severe respiratory depression but survived after respirator therapy. In the patients with lower plasma concentrations the poisoning had a benign course. In most cases the plasma concentration of norpropoxyphene exceeded that of propoxyphene even in the first blood sample.

Telencephalic leucoencephalopathy in premature infants dying after prolonged artificial respiration. Report on 6 cases.

This study reports clinical and neuropathological findings in six premature infants dying after prolonged assisted ventilation (IPPB and CPPB) due to pulmonary insufficiency (gestational age: 26.--32. week; birth weight 820--1400 Gm; respirator therapy 41--143 days; survival 104--263 days). During the rspirator therapy the children developed marked extensor rigidity of the trunc and spasticity of the extremities. Postmortem examination revealed cor pulmonale and right ventricular failure. Signs of marked perinatal brain damage were missed. The slightly atrophic brains showed predominant damage to the telencephalic white matter of varying intensity ranging from focal necroses to gliosis and retarded myelination. Constant findings were increased vascularisation and transformation of the premyelinating glia into astrocytes in the deep and subcortical white matter. This form of telencephalic leucoencephalopathy indicates the particular vulnerability of the developing white matter in conditions with chronic hypoxia, hypercapnia, acidosis and vascular congestion. The varying intensity of the lesions suggests that, in principle, minor lesions are either reversible or may be compensated in surviving children.

Clinical applications of thermodilution cardiac output determinations

The pulmonary arterial catheter was shown to be safe and easily positioned in a group of 200 patients. Thermodilution cardiac output measurement was shown to be simple, rapid, and safe. The technic was as accurate as the simultaneously measured indocyanine green cardiac output, and more reproducible, particularly at high and low flows. The construction of myocardial performance curves during a fluid challenge is described. The value of these curves is guiding fluid, drug, and respirator therapy is illustrated by case presentations.

PATENT DUCTUS ARTERIOSUS (PDA) IN INFANTS LESS THAN 30 WEEKS GESTATION: INDICATIONS FOR SURGERY

As intensive respiratory care is provided to more preterm infants with respiratory distress syndrome (RDS), heart failure from an associated PDA is being increasingly recognized. How ever, indications for surgery are not clearly defined. The clinical courses of 21 infants ≤ 30 wks. gestation with RDS and a PDA diagnosed by either single film aortography or surgery were analyzed. Two clinical patterns were identified. One, involving infants with severe RDS (8 cases) requiring high respirator pressures and the other with mild or moderate RDS (13 cases). Those infants with severe RDS showed some improvement by 3 days, but relapsed again requiring continuation of respiratory assistance. Four infants with massive cardiomegaly and pulmonary edema underwent ligation of PDA between 5-9 days. Aortography demonstrated massive left-to-right ductal shunt as early as 3 days. Therefore it is suggested that ligation of PDA should be performed at the time of relapse or a short time later. Those infants with mild or moderate RDS recovered from their disease within a few days. They subsequently developed persistent apnea associated with PDA and heart failure. Ten infants could not be weaned from the respirator and underwent ligation of PDA between 8-32 days. It is suggested that in this group of infants surgery should be performed at the time when respirator therapy is needed to control the heart failure.

THE CONTINUUM OF MORBIDITY AND MORTALITY IN THE LOW BIRTH WEIGHT(LBW) INFANT

Infants with BW <1500gm discharged from LAC-USC nursery during a 15 month period(Oct.72-Dec.73)were followed to assess the continuing morbidity and mortality of the LBW infant. Of 101 infants, 5 were lost to followup, 7 were cared for by private physicians and 89 were followed by a clinic team of pediatric nurse practitioners, pediatricians, and social workers. Four infants died for a mortality of 4.5%. Significant medical morbidity requiring 48 hospitalizations occurred in 19 infants. Failure to thrive and child abuse were found in 9 infants. Outcome morbidity and mortality were related to severity of neonatal respirator disease. 21 of 89(23.6%) infants required respirator therapy in the nursery. 2 of 4 deaths were in infants treated with respirators during the newborn period. Significant morbidity requiring 1 or more hospitalization occurred in 10 or 45% of respirator infants compared with 9 or 13.3% of non-respirator infants. Failure to thrive and child abuse were found in 1(or 4.6%)respirator infant compared with 8(11.7%)non-respirator infants. The LBW newborn continues to be at high risk for morbidity and mortality after discharge. Infants requiring ventilatory assistance had a higher incidence of morbidity and mortality. Mortality seemed less related to nursery course than to post-natal events.

A Method of Securing Orotracheal Tubes in Neonatal Respiratory Care

Endotracheal tubes, employed in respirator therapy or CPAP, must remain in place despite frequent suctioning, manipulation of the baby by x-ray and blood-drawing technicians, and changes in the baby's position. After trying several methods, the following simple inexpensive method of securing endotracheal tubes is now used in our NICU. Materials Figure 1 pictures the materials that are used. The clamp is a Hollister plastic umbilical clamp with a central hole drilled to accommodate the endotracheal tube. The clamp's "safety lock"is beveled on both sides so the clamp can be opened and closed.