Randomised trial of elective continuous positive airway pressure (CPAP) compared with rescue CPAP after extubation

AIM: To determine if a weaning regimen on flow driver continuous positive airway pressure (CPAP) would decrease the number of ventilator days but increase the number of CPAP days when compared with a rescue regimen. METHODS: Fifty eight babies of 24-32 weeks gestation with respiratory distress syndrome (RDS) were studied prospectively. After extubation they were randomly allocated to receive CPAP for 72 hours (n = 29) according to a weaning regimen, or were placed in headbox oxygen and received CPAP only if present "start CPAP" criteria were met (n = 29, rescue group). RESULTS: There was no difference in successful extubation at 72 hours, 1 and 2 weeks, between the groups in terms of the number of reventilation episodes, reventilation days, or in total days of CPAP. Birthweight, gestational age, race, day of first extubation, antenatal or postnatal steroids, patent ductus arteriosus status and maximal mean airway pressure used were of no value in predicting success or failure at 72 hours, 1, or 2 weeks. CONCLUSION: The weaning regimen did not decrease the number of ventilator days or days on CPAP compared with the rescue regimen. The rescue regimen on flow driver CPAP seems to be a safe and effective method of managing a baby of 24-32 weeks gestation who has been ventilated for RDS or immature lung disease.     

A randomized, controlled trial of aminophylline in ventilatory weaning of premature infants

OBJECTIVES: To determine whether maximal inspiratory force predicts successful neonatal extubation, and whether aminophylline affects maximal inspiratory force or the success rate of extubation. DESIGN: Double-blind, prospective, randomized, placebo-controlled trial. SETTING: Tertiary level neonatal intensive care unit. PATIENTS: A total of 20 ventilated, preterm, newborn infants: birth weight < 2.5 kg; gestation < 35 wks. INTERVENTIONS: Intravenous aminophylline 4 mg/kg bolus followed by 2.5 mg/kg every 6 hrs x three doses, then 1.5 mg/kg every 6 hrs; or placebo. Drug administration began when infants were receiving an FIO2 of < 0.4 and were progressively weaning from assisted mechanical ventilation. A standardized weaning protocol was instituted, and patients were extubated when they were able to tolerate a mechanical ventilatory rate of < 5 cycles/min. MEASUREMENTS AND MAIN RESULTS: Occlusion pressures, including maximal inspiratory force, were measured before aminophylline and daily until endotracheal extubation. Arterial blood gases were measured every 3 hrs, and 24-hr cardiac and respiratory recordings were performed postextubation. Three of ten aminophylline-treated patients failed extubation compared with two of ten placebo infants (p = nonsignificant). Mean apnea frequency postextubation was 0.02/hr in the aminophylline group compared with 0.3/hr in the placebo group (p < .05). Aminophylline had no effect on successful extubation or on maximal inspiratory force. Maximal inspiratory force was not correlated with the success of extubation. Apnea frequency postextubation was significantly reduced by aminophylline. CONCLUSIONS: Aminophylline is an effective prophylaxis for postextubation apnea in the preterm infant but does not affect maximal inspiratory force or increase the success rate of extubation in this patient population.     

Venous leg ulcers. Part 1: Aetiology

Cardiogenic pulmonary edema is a frequent cause of reparatory failure. We investigated the effects of nasal continuous positive airway pressure (CPAP) in patients with severe pulmonary edema associated with acute myocardial infarction. Twenty-nine consecutive patients were divided into 3 groups: firstly, 7 intubated patients who received mechanical ventilation at study entry comprised the intubation group. The rest of the patients were randomly assigned to either of the following 2 groups: 11 patients who received oxygen plus CPAP delivered by a nasal mask (CPAP group), and 11 patients who received oxygen only via face mask (oxygen group). All patients in the intubation group had cardiogenic shock. Two patients (18%) in the CPAP group and 8 patients (73%) in the oxygen group required mechanical ventilation with endotracheal intubation (p=0.03). The hospital mortality rate in the CPAP group (9%) was significantly lower than the oxygen group (64%, p=0.02). The pulmonary artery wedge pressure and heart rate were significantly lower in the CPAP group than in the oxygen group 24 h after study entry (p<0.05 and p<0.01). The mean pulmonary artery pressure 48 h after study entry was 18+/-5 mmHg in the CPAP group and 25+/-8 mmHg in the oxygen group (p<0.05). The PaO2/FiO2 ratio increased in the intubation group (168+/-69 to 240+/-57, p<0.05) and the CPAP group (137+/-17 to 253+/-67, p<0.01) 24 h after study entry. Arterial plasma endothelin-1 concentrations decreased significantly earlier in the CPAP group than in the oxygen group (p<0.05). In patients without cardiogenic shock, nasal CPAP lead to an early improvement in oxygenation and hemodynamics, and decreased the mortality rate. Early and active respiratory management is recommended in patients with pulmonary edema associated with acute myocardial infarction.     

Immunohistochemical demonstration of c-myc oncogene product in middle ear cholesteatoma

Oxygen consumption at intermittent mandatory ventilation (IMV) rates of 10 and 20 breaths per minute was evaluated to determine whether a higher IMV rate in mechanically ventilated premature infants with apnea and respiratory insufficiency would reduce metabolic expenditure. Ten studies were performed in seven infants, with three infants studied twice after a trial of failed elective extubation. The mean birth weight was 952 +/- 183 kg (SD), and the mean postnatal age was 12 +/- 8 days (SD). Mean oxygen consumption per kilogram of body weight was not significantly related to pulmonary resistance, dynamic lung compliance, or resistive work of breathing. Mean oxygen consumption was not altered at the different IMV rates. The oxygen consumption difference at the two IMV rates was not significantly related to dynamic lung compliance, resistance, or work of breathing. These results demonstrate that mechanically dependent premature infants without bronchopulmonary dysplasia do not have significant alteration in oxygen consumption with changes in IMV. This finding suggests that there is no potential metabolic energy balance benefit in use of moderately higher IMV rates to achieve improved growth rates in this population of infants.     

Randomized multicenter trial comparing synchronized and conventional intermittent mandatory ventilation in neonates

OBJECTIVE: To compare synchronized intermittent mandatory ventilation (SIMV) and conventional intermittent mandatory ventilation (IMV) in neonates. STUDY DESIGN: Prospective, multicenter, randomized clinical trial. SETTING: Level III neonatal intensive care units at six university or children's hospitals. PATIENTS: Three hundred twenty-seven infants receiving conventional IMV for respiratory distress syndrome, pneumonia, or meconium aspiration pneumonitis were randomly assigned a 7.5 +/- 6 hours of age to either continue with IMV or change to SIMV. Infants assigned to each mode of ventilation had similar birth weight (BW), gestational age, and Apgar scores at birth, and similar oxygenation indexes at randomization. They received similar surfactant therapy and had similar incidence of sepsis, seizures, secondary pneumonia, and necrotizing enterocolitis. In the infants with BW less than 1000 gm, more infants receiving IMV had surgical ligation of their patent ductus arteriosus than did those receiving SIMV (27 vs. 7 %; p = 0.02). ANALYSIS: Data was analyzed overall for all infants and also separately within three BW groups: less than 1000 gm, 1000 to 2000 gm, and more than 2000 gm. The 1000 to 2000 gm BW group was further analyzed in subgroups weighing 1000 to 1499 gm and 1500 to 2000 gm. RESULTS: In all infants, at 1 hour after randomization, the infants receiving SIMV had a lower mean airway pressure than those receiving IMV (8.08 +/- 2.15 vs. 8.63 +/- 2.59; p<0.05), with similar fractions of inspired oxygen and oxygenation indexes. Infants whose BW was 1000 to 2000 gm at 0.5 hour required a lower fraction of inspired oxygen with SIMV than with IMV (0.52 +/- 0.20 vs. 0.62 +/- 0.27; p<0.05) and had better oxygenation at 1 hour, as shown by lower oxygenation indexes with SIMV than with IMV (6.14 +/- 4.17 vs. 9.42 +/- 8.41; p = 0.01). Infants whose BW was 1000 to 2000 gm received a lower number of unit doses of sedative/analgesic drugs per infant during the first 4 days of SIMV than did infants receiving IMV (3.8 +/- 3.4 vs 6.3 +/- 5.5 unit doses; p = 0.02). Infants whose BW was more than 2000 gm had a shorter duration of mechanical ventilation with SIMV than with IMV (median, 72 vs 93 hours; p = 0.02). Three of the forty-six infants receiving IMV but none of the 47 infants receiving SIMV required extracorporeal membrane oxygenation. In the infants with BW less than 1000 gm, fewer infants treated with SIMV required supplemental oxygen at 36 weeks of postconceptional age than did those treated with IMV (47 vs 72%; p<0.05). In 83 infants whose lungs were mechanically ventilated for 14 days or longer, all with BW less than 2000 gm, those treated with SIMV regained their BW earlier than those treated with IMV (median, 21.5 vs 29 days; p<0.01). There were no differences in the rates of death, intraventricular hemorrhage (grades III and IV), air leak, need for pharmacologic paralysis, or need for supplemental oxygen at 28 days. CONCLUSIONS: We found that SIMV was at least as efficacious as conventional IMV, and may have improved certain outcomes in BW-specific groups.     

Partial cardiopulmonary bypass in rats for evaluating ischemia-reperfusion injury

The authors developed a miniaturized partial cardiopulmonary bypass model in rats by using membrane oxygenators. Sprague-Dawley rats underwent general anesthesia and tracheostomy for ventilation. Partial cardiopulmonary bypass was carried out through the jugular cannula (18 gauge) for venous blood drainage and through the femoral arterial cannula (24 gauge) at a flow of 50 ml/kg/min. Membrane oxygenators used in this study maintained arterial oxygen tensions (PaO2) at 300-500 mmHg and carbon dioxide tensions (PaCO2) at 25-35 mmHg, with a gas mixture of 95% O2 + 5% CO2 (n = 7) for at least 2 hr of bypass circulation. To test the feasibility of this system for investigation of ischemia-reperfusion injury, hypoxic challenges with gas mixtures of different oxygen concentrations were examined. After equilibration of the bypass circulation for 1 hr, the following gases were tested for 15 min: Group I, 95% air + 5% CO2 (FiO2 = 0.21, n = 5); Group II, 10% O2 + 5% CO2 + 85% N2 (FiO2 = 0.1, n = 5); and Group III, 95% N2 + 5% CO2 (FiO2 = 0, n = 5). Equilibrated PaO2 values after challenge with these gases for 15 min were as follows: Group I: 89.6 +/- 3.7, Group II: 53.8 +/- 1.4, Group III: 25.6 +/- 2.0 mmHg (p < 0.01 between Groups I and II, I and III, II and III; p < 0.01 vs. prehypoxic PaO2 values in all groups). PaO2 values returned to the previous level within 15 min after return to the standard gas mixture (95% O2 + 5% CO2) supply. This system provided stable cardiopulmonary bypass in rats for at least 2 hr and may be useful for investigation of ischemia-reperfusion injury.     

Composition of peripheral blood progenitor cell components collected from healthy donors

OBJECTIVES: The purpose of this study was to test the hypothesis that low circulating thyroxine concentrations characteristic of very low birth weight (VLBW) neonates (< 1500 g) are the result of decreased protein binding of thyroid hormones and to elucidate the mechanism(s) responsible and possible significance thereof. DESIGN: Cross-sectional comparison of thyroid related measurements in cord blood specimens from VLBW infants and from full term infants. Longitudinal comparison in cord and 2- and 4-week blood specimens from VLBW infants. PATIENTS: Cord blood specimens were analysed from 47 VLBW and 45 full term infants weighing > or = 2500 g. Repeat analyses in venous bloods from 32 of the VLBW infants were analysed at 2 weeks of age and again at 4 weeks in 23. The first cohort of patients was studied in 1994 and comprised 28 VLBW and 24 full term infants (Cohort A). The studies were repeated in 1995-96 in 19 VLBW infants and 21 full term infants (Cohort B). MEASUREMENTS: T4, free T4 (FT4), T3, thyroxine binding globulin (TBG), and TSH were measured in cord blood and 2- and 4-week venous specimens from VLBW infants and in cord blood specimens of full term infants. Molar ratios of T4/TBG were calculated. RESULTS: (1) Cord blood TBG, T4 and T3 concentrations of VLBW infants were each 60% of those of term infants. TBG concentrations were 397 +/- 111 vs 680 +/- 172 nmol/l (P < 0.0005). T4 concentrations were 76 +/- 22 vs 139 +/- 26 nmol/l (P < 0.0005). FT4 concentrations were in the normal adult range in both neonatal groups. T4/TBG ratios did not differ between the neonatal groups but were significantly less than that of adults (P < 0.001). (2) TSH concentrations in VLBW infants at 2 and 4 weeks were less than 50% of cord blood values. At 2 weeks, TBG concentrations of VLBW infants were unchanged from cord blood concentrations but mean T4 concentration fell by 18% and T4/TBG ratios by 21% (P < 0.005). Mean FT4 rose by 78% (P < 0.02). The changes in mean T4 and FT4 were due largely to FT4 concentrations of 37-113 pmol/l and T4 concentrations of 13-48 nmol/l in 5 infants. These infants also had lower T4/TBG ratios and were smaller and more ill than the remainder of the cohort. The changes disappeared by 4 weeks in 3 of the 4 infants tested. CONCLUSIONS: Cord T4/TBG ratios are the same in very low birth weight and term infants and are significantly lower than in adult blood. These are more than compensated for in term infants by a 236% increase in thyroxine binding globulin concentrations. The lower thyroxine binding globulin concentrations in very low birth weight infants explain their much lower T4 concentrations. Cord FT4 concentrations of full term and very low birth weight infants are in the normal adult range. T4 concentrations are further depressed and free T4 concentrations elevated in the most ill very low birth weight infants at 2 weeks of age in a manner analogous to that of the 'sick euthyroid syndrome'.     

Comparison of alveolar ventilation, oxygenation, pressure support, and respiratory system resistance in response to noninvasive versus conventional mechanical ventilation in foals

OBJECTIVE: To compare the efficacy of positive pressure ventilation applied through a mask versus an endotracheal tube, using anesthetized/paralyzed foals as a model for foals with hypoventilation. ANIMALS: Six 1-month-old foals. PROCEDURE: A crossover design was used to compare the physiologic response of foals to 2 ventilatory techniques, noninvasive mask mechanical ventilation (NIMV) versus endotracheal mechanical ventilation (ETMV), during a single period of anesthesia and paralysis. Arterial pH, PaO2, PaCO2, oxygen saturation, end-tidal CO2 tension, airway pressures, total respiratory system resistance, resistance across the upper airways (proximal to the midtracheal region), and positive end-expiratory pressures (PEEP) were measured. Only tidal volume (VT; 10, 12.5, and 15 ml/kg of body weight) or PEEP (7 cm of H2O) varied. RESULTS: Compared with ETMV, use of NIMV at equivalent VT resulted in PaCO2 and pH values that were significantly higher, but PaO2 was only slightly lower. Between the 2 methods, peak airway pressure was similar, but peak expiratory flow was significantly lower and total respiratory resistance higher at each VT for NIMV. Delivery of PEEP (7 cm of H2O) was slightly better for ETMV (7.1 +/- 1.3 cm of H2O) than for NIMV (5.6 +/- 0.6 cm of H2O). CONCLUSION: These data suggest that use of NIMV induces similar physiologic effects as ETMV, but the nasal cavities and mask contribute greater dead space, manifesting in hypercapnia. Increasing the VT used on a per kilogram of body weight basis, or the use of pressure-cycled ventilation might reduce hypercapnia during NIMV. CLINICAL RELEVANCE: Use of NIMV might be applicable in selected foals, such as those with hypoventilation and minimal changes in lung compliance, during weaning from endotracheal mechanical ventilation, or for short-term ventilation in weak foals.     

Airway occlusion pressure at 0.1 s (P0.1) after extubation: an early indicator of postextubation hypercapnic respiratory insufficiency

OBJECTIVE: To examine variables associated with postextubation respiratory distress in chronic obstructive pulmonary disease (COPD) patients. DESIGN: Prospective, clinical investigation. SETTING: Intensive care unit of a university hospital. PATIENTS: Forty COPD patients, considered ready for extubation. MEASUREMENTS AND MAIN RESULTS: We recorded, from the digital display of a standard ventilator, breathing frequency (f), tidal volume (VT) and f/VT for the respiratory pattern, airway occlusion pressure at 0.1 s (P0.1) for the respiratory drive and measured blood gases: i) before extubation, following 30 min of a 6 cm H2O pressure support (PS) ventilation trial, ii) 1 h after extubation, at the 30th min of a face mask 4 cm H2O PS ventilation trial. According to the weaning outcome, the patients were divided into two groups: respiratory distress, and non-respiratory distress within 72 h of the discontinuation of mechanical ventilation. The respiratory distress was defined as the combination of f more than 25 breaths/min, an increase in PaCO2 of at least 20% compared with the value measured after extubation, and pH lower than 7.35. We determined whether those patients who developed respiratory distress after extubation differed from those who did not. Respiratory pattern data and arterial blood gases recorded, either before or after extubation, and P0.1 recorded before extubation, were inadequate to differentiate the two groups. Only P0.1 recorded 1 h after the discontinuation of mechanical ventilation differentiated the patients who developed respiratory distress from those who did not (4.2+/-0.9 vs 1.8+/-0.8, p < 0.01). CONCLUSIONS: P0.1 recorded after extubation may be a good indicator of postextubation respiratory distress. Measuring P0.1 and/or the analysis of the evolution of this parameter could facilitate decisions during the period following extubation.     

Randomised, controlled trial of nasal continuous positive airway pressure in the extubation of infants weighing 600 to 1250 g

AIM: To determine whether extubation to nasal continuous airway pressure (NCPAP) results in a greater proportion of infants remaining free of additional ventilatory support for one week after extubation compared with those extubated directly to headbox oxygen. METHODS: A randomised, controlled, clinical trial was conducted at the neonatal intensive care unit of the Royal Women's Hospital, Melbourne, of infants with birthweights between 600 and 1250 g, ventilated via an endotracheal tube for more than 12 hours, requiring less than 50% oxygen, a ventilator rate < or = 20/minute, considered by the clinical management team to be ready for extubation. Infants were randomly allocated either to NCPAP or to oxygen administered via a headbox. Success was defined by no requirement for additional ventilatory support over the week following extubation. Failure criteria were (i) apnoea; (ii) absolute increase in oxygen requirement greater than 15% above than required before extubation; or (iii) respiratory acidosis (pH < 7.25 with pCO2 > 6.67 kPa). RESULTS: Thirty one of 47 (66%) infants were successfully extubated to NCPAP compared with 18 of 45 (40%) for headbox oxygen. The increase in failure rate in the headbox group was due primarily to increased oxygen requirements in this group. Of the 27 who failed headbox oxygen, 26 were given a trial of NCPAP and 13 did not require endotracheal reintubation. There was no significant difference between the groups in the total number of days of assisted ventilation or the duration of inpatient stay. CONCLUSIONS: NCPAP applied prophylactically after endotracheal extubation reduces the incidence of adverse clinical events that lead to failure of extubation in the seven days after extubation. This reduction is clinically important. The benefits of NCPAP do not seem to be associated with an increased incidence of unwanted side effects.     

Noninvasive positive pressure ventilation via face mask. First-line intervention in patients with acute hypercapnic and hypoxemic respiratory failure

OBJECTIVES: We have previously reported our experience with noninvasive positive pressure ventilation (NPPV) via face mask in a small group of selected patients with acute respiratory failure (ARF). NPPV was frequently effective (70% success rate) in correcting gas exchange abnormalities and in avoiding endotracheal intubation (ETI); NPPV also had a low rate of complications. We have evaluated the clinical application of NPPV as first-line intervention in patients with hypercapnic and short-term hypoxemic ARF. A dedicated respiratory therapist conducted an educational program with physicians-in-training rotating through the medical ICUs of a university medical center and supervised implementation of a simplified management protocol. Over 24 months, 164 patients with heterogeneous forms of ARF received NPPV. We report on the effectiveness of NPPV in correcting gas exchange abnormalities, in avoiding ETI, and associated complications, in different conditions precipitating ARF. PATIENT POPULATION: One hundred fifty-eight patients completed the study. Forty-one had hypoxemic ARF, 52 had hypercapnic ARF, 22 had hypercapnic acute respiratory insufficiency (ARI), 17 had other forms of ARF, and 26 with advanced illness had ARF and refused intubation. Twenty-five percent of the patients developed ARF after extubation. INTERVENTION: Mechanical ventilation was delivered via a face mask. Initial ventilatory settings were continuous positive airway pressure (CPAP) mode, 5 cm H2O, with pressure support ventilation of 10 to 20 cm H2O titrated to achieve a respiratory rate less than 25 breaths/min and an exhaled tidal volume of 7 mL/kg or more. Ventilator settings were adjusted following arterial blood gases (ABG) results. RESULTS: The mean duration of NPPV was 25 +/- 24 h. When the 26 patients with advanced illness are excluded, NPPV was effective in improving or correcting gas exchange abnormalities in 105 patients (80%) and avoiding ETI in 86 (65%). Failure to improve ABG values was the reason for ETI in 20 of 46 (43%). The overall average predicted and actual mortality were 32% and 16%, respectively. Survival was 93% in non-intubated patients and 79% in intubated patients. NPPV was effective in lessening dyspnea throughout treatment in all but seven patients. Complications developed in 24 patients (16%). In patients with hypercapnic ARF, nonresponders had a higher PaCO2 at entrance (91.5 +/- 4.2 vs 80 +/- 1.5; p < 0.01). In patients with hypercapnic ARF and ARI, arterial blood gases response (pH and PaCO2) within 2 h of NPPV predicted success (p < 0.0001). None of the entrance parameters predicted need for ETI. CONCLUSIONS: We conclude that application of NPPV in clinical practice is an effective and safe alternative to ETI in many hemodynamically stable patients with hypercapnic ARF and in those with hypoxemic ARF in whom the clinical condition can be readily reversed in 48 to 72 h. An educational and supervision program is essential to successfully implement this form of therapy.     

Association of fungal colonization and invasive disease in very low birth weight infants

BACKGROUND: Fungi are common pathogens of nosocomial infections in the very low birth weight (VLBW) infants. The purpose of this study was to investigate the fungal colonization rate in VLBW infants and the association between fungal colonization and systemic fungal diseases. MATERIALS: Between January 1, 1996, and December 31, 1996, 116 infants with birth weight < 1500 g admitted to the neonatal intensive care unit of Chang Gung Children's Hospital in the first day of life were included in this prospective study. METHODS: Cultures from oropharynx, rectum, skin (groin and axilla), bag urine and endotracheal aspirates were obtained in the first 24 h after birth and weekly thereafter throughout their neonatal intensive care unit stay. Medical records were reviewed weekly. RESULTS: Fungal colonization was detected in 25 infants, among whom 17 infants developed colonization by 2 weeks of life. Candida albicans (61%) and Candida parapsilosis (29%) were the 2 most common organisms. The rectum (76%) was the most frequent site of colonization. Factors significantly associated with colonization were prolonged administration of antibiotic therapy, parenteral nutrition and intralipid emulsion. Three of 116 infants developed fungemia. The association between colonization and subsequent fungemia was demonstrated in 1 infant, representing 4% of colonized infants. CONCLUSION: Fungal colonization was detected in one-fifth of VLBW infants and represents a risk factor for fungemia. Because disease occurred in the absence of apparent colonization, factors other than colonization may contribute to invasive candidiasis.     

Gastric intramucosal pH: an indicator of weaning outcome from mechanical ventilation in COPD patients

The aim of this study was to determine whether gastric intramucosal pH (pHim) and/or gastric intramucosal carbon dioxide tension (PCO2,im) measured by tonometry can be used to predict the success of weaning in chronic obstructive pulmonary disease (COPD) patients. Twenty six consecutive COPD patients, undergoing mechanical ventilation for acute respiratory failure and satisfying the criteria of weaning from mechanical ventilation with nasogastric tonometer in place, were studied. Arterial blood gas values and PCO2,im were measured 24 h before (H-24), just before (H0), and after 20 min of a weaning trial on T-piece (H20min). Weaning failure was defined as the development of respiratory distress and/or arterial blood gas impairments during the first 2 h of spontaneous breathing on T-piece, or reintubation within 24 h after extubation. Between the weaning failure (n = 6) and weaning success (n = 20) groups, there were no differences in blood gas analysis readings at H-24 and H0 before the weaning period, age, Simplified Acute Physiology Score (SAPS) on admission, SAPS on the day of weaning trial, and duration of ventilation. Clinical status, tonometric and arterial gasometric data were similar at H-24 and H0 in all patients. During mechanical ventilation, pHim was < or = 7.30 in patients who failed weaning and > 7.30 in patients who were successfully weaned (p < 0.001; 100% sensitivity and specificity). The threshold value for PCO2,im of 8.0 kPa (60 mmHg) represents a clear demarcation with respect to outcome before the weaning trial. PCO2,im values during mechanical ventilation are significantly different (p < 0.001) between patients who were successfully weaned and those who were not (6.9 +/- 0.9 vs 9.9 +/- 1.1 kPa (51.9 +/- 6.7 vs 74.3 +/- 8.0 mmHg, respectively)). At H20min, pHim and PCO2,im were still statistically different between the weaning failure and the weaning success group. We conclude that measurement of gastric intramucosal pH (or gastric intramucosal carbon dioxide tension) represents a simple and accurate index to predict weaning outcome in chronic obstructive pulmonary disease patients before attempting weaning.     

Advantage of rubber over plastic endotracheal tubes for rapid extubation in a laser fire

The occurrence of airway fires during laser airway surgery necessitates the use of special techniques to improve patient safety. For example, it is recommended that the endotracheal tube cuff be inflated with saline. However, in the event of an endotracheal tube fire, the tube must be quickly removed. This study was designed to determine the time necessary for red rubber (RR) or polyvinylchloride (PVC) endotracheal tubes to be removed from a model airway after inflating the cuffs with saline. A model larynx and trachea was suspended vertically. It was intubated with either 7.0 RR or PVC endotracheal tubes. Six milliliters of saline was used to inflate the endotracheal tube cuffs. After inflation, a clamp was used to occlude the pilot tube on the RR endotracheal tubes. A 4-lb weight was then suspended from the endotracheal tube. The time to spontaneous extubation of the model trachea after unclamping the pilot tubes on 12 RR endotracheal tubes was determined. For the PVC endotracheal tubes, the times to spontaneous extubation using the 4-lb weight were determined in 12 endotracheal tubes after cutting the pilot tube and in 12 by maximum aspiration of the saline from the endotracheal tube cuff with a 10-ml syringe. A time of 0.94 +/- 0.10 sec (mean +/- SD) was required for spontaneous extubation of the RR endotracheal tubes after unclamping the pilot tube. For the PVC endotracheal tubes, extubation occurred 3.28 +/- 1.08 and 1.81 +/- 0.60 sec after cutting the pilot tube or deflating the cuff with a syringe, respectively. The mean times for each of the 3 groups were significantly different (p < 0.05) from each other as determined by the ANOVA. This study shows that if PVC endotracheal tubes are used, deflation of the saline-filled cuff by aspiration with a 10-ml syringe is faster than cutting the pilot tube. Unclamping the pilot tube on the RR endotracheal tubes resulted in the fastest time to endotracheal extubation.     

Does airway pressure release ventilation alter lung function after acute lung injury?

BACKGROUND: During airway pressure release ventilation (APRV), tidal ventilation occurs between the increased lung volume established by the application of continuous positive airway pressure (CPAP) and the relaxation volume of the respiratory system. Concern has been expressed that release of CPAP may cause unstable alveoli to collapse and not reinflate when airway pressure is restored. OBJECTIVE: To compare pulmonary mechanics and oxygenation in animals with acute lung injury during CPAP with and without APRV. DESIGN: Experimental, subject-controlled, randomized crossover investigation. SETTING: Anesthesiology research laboratory, University of South Florida College of Medicine Health Sciences Center. SUBJECTS: Ten pigs of either sex. INTERVENTIONS: Acute lung injury was induced with an intravenous infusion of oleic acid (72 micrograms/kg) followed by randomly alternated 60-min trials of CPAP with and without APRV. Continuous positive airway pressure was titrated to produce an arterial oxyhemoglobin saturation of at least 95% (FIO2 = 0.21). Airway pressure release ventilation was arbitrarily cycled to atmospheric pressure 10 times per minute with a release time titrated to coincide with attainment of respiratory system relaxation volume. MEASUREMENTS: Cardiac output, arterial and mixed venous pH, blood gas tensions, hemoglobin concentration and oxyhemoglobin saturation, central venous pressure, pulmonary and systemic artery pressures, pulmonary artery occlusion pressure, airway gas flow, airway pressure, and pleural pressure were measured. Tidal volume (VT), dynamic lung compliance, intrapulmonary venous admixture, pulmonary vascular resistance, systemic vascular resistance, oxygen delivery, oxygen consumption, and oxygen extraction ratio were calculated. MAIN RESULTS: Central venous infusion of oleic acid reduced PaO2 from 94 +/- 4 mm Hg to 52 +/- 9 mm Hg (mean +/- 1 SD) (p < 0.001) and dynamic lung compliance from 40 +/- 6 mL/cm H2O to 20 +/- 6 mL/cm H2O (p = 0.002) and increased venous admixture from 13 +/- 3% to 32 +/- 7% (p < 0.001) in ten swine weighing 33.3 +/- 4.1 kg while they were spontaneously breathing room air. After induction of lung injury, the swine received CPAP (14.7 +/- 3.3 cm H2O) with or without APRV at 10 breaths per minute with a release time of 1.1 +/- 0.2 s. Although mean transpulmonary pressure was significantly greater during CPAP (11.7 +/- 3.3 cm H2O) vs APRV (9.4 +/- 3.8 cm H2O) (p < 0.001), there were no differences in hemodynamic variables. PaCO2 was decreased and pHa was increased during APRV vs CPAP (p = 0.003 and p = 0.005). PaO2 declined from 83 +/- 4 mm Hg to 79 +/- 4 mm Hg (p = 0.004) during APRV, but arterial oxyhemoglobin saturation (96.6 +/- 1.4% vs 96.9 +/- 1.3%) did not. Intrapulmonary venous admixture (9 +/- 3% vs 11 +/- 5%) and oxygen delivery (469 +/- 67 mL/min vs 479 +/- 66 mL/min) were not altered. After treatment periods and removal of CPAP for 60 min, PaO2 and intrapulmonary venous admixture returned to baseline values. DISCUSSION: Intrapulmonary venous admixture, arterial oxyhemoglobin saturation, and oxygen delivery were maintained by APRV at levels induced by CPAP despite the presence of unstable alveoli. Decrease in PaO2 was caused by increase in pHa and decrease in PaCO2, not by deterioration of pulmonary function. We conclude that periodic decrease of airway pressure created by APRV does not cause significant deterioration in oxygenation or lung mechanics.     

Measurement of pulmonary status and surfactant protein levels during dexamethasone treatment of neonatal respiratory distress syndrome

PURPOSE: To study the effect of epidural buprenorphine on minimum alveolar concentration (MAC) of volatile anaesthetics, duration of analgesia and respiratory function in the perioperative period. METHODS: One hundred and twenty patients, ASA I-II undergoing gynaecological surgery were randomly divided into three studies. The forty patients in each study were randomly divided into four groups depending on the dosage; Group I (control), Group II (80 micrograms. kg-1 morphine), Group III (4 micrograms. kg-1 buprenorphine), Group IV (8 micrograms. kg-1 buprenorphine). The MAC of halothane was measured following epidural administration of the agents in each group. The duration of analgesia was assessed by the first request for pentazocine. Postoperative analgesic effects were assessed by the total dosage of pentazocine required for the 48 hr after surgery. Respiratory rate (RR), minute volume (MV), and PaCO2 were measured during surgery and the postoperative period. The MAC of halothane was reduced in Group IV (P < 0.01). The duration of analgesia was 10.0 +/- 5.1 hr (Mean +/- SE) in Group I, 37.7 +/- 4.7 hr in Group II, 27.1 +/- 7.1 hr in Group III, and 44.4 +/- 4.1 hr in Group IV. Total dosage of pentazocine was lower in Group IV (P < 0.05) than in the other groups. The decrease of RR, MV and the increase of PaCO2 were observed within 60 min in Group III and IV dose dependently. CONCLUSION: Epidural buprenorphine administered in a dose of 4 or 8 micrograms. kg-1 provides postoperative analgesia that is no less effective than that of morphine.     

The use of nasal CPAP in newborns with respiratory distress syndrome

The efficiency of applying continuous positive airway pressure (CPAP) by the nasal route was retrospectively nalyzed in 32 newborns with RDS (23 uncomplicated HMD with additional cardiac or pulmonary complications and 7 RDS of non-hyaline membrane etiology) who underwent nasal CPAP treatment at the Kinderspital Zurich from 1972--1974. 16 of the 23 infants with uncomplicated HMD were successfully treated with CPAP. They showed a significant rise in PaO2 as well as a significant drop in respiratory frequency during nasal CPAP application, the PaCO2 did not change significantly. The remaining 7 infants in this group (7/23) had to be intubated and mechanically ventilated owing to a persistent high FIO2 (4 infants), technical difficulties (1) or nasal hypersecretion (2). Two of these 23 infants died, one of meningitis, one of cerebral hemorrhage. The two infants with HMD and additional cardiac or pulmonary complications and 3 of 7 infants with RDS of non-hyaline membrane etiology had to be intubated and mechanically ventilated after failure of nasal CPAP. All 9 infants in these two groups survived. The nasal CPAP system as described is a simple, inexpensive and effective method of applying CPTPP in newborns with uncomplicated HMD, except radiological stage IV. In HMD with additional cardiac or pulmonary complications and in RDS of non-hyaline membrane etiology the results of nasal CPAP treatment were not convincing.     

The content of electrolytes (Na, K, Ca, Mg) in vertebrate otoliths and otoconia

IVOX (intravenous oxygenator and CO2 removal device) augments venous gas exchange in patients with severe respiratory failure. Controlled hypoventilation with permissive hypercapnia reduces airway pressures during mechanical ventilation and augments CO2 exchange through the IVOX. To quantify the additive effects of gradual permissive hypercapnia and IVOX on gas exchange and reduction of airway pressures, 13 adult sheep underwent tracheostomy and severe smoke inhalation injury. Seven were mechanically ventilated alone (control), and six had mechanical ventilation, systemic anticoagulation, and implantation of IVOX (size 7 with 0.21-m2 surface area) (IVOX group). Both groups were anesthetized and paralyzed for 24 hr. In the IVOX group, minute ventilation was decreased in a stepwise fashion to produce a gradual increase in PaCO2, from 30 to 95 mm Hg, over 12 hr, and then sustained for an additional 12 hr. Sodium bicarbonate was given intravenously as necessary to keep arterial pH above 7.25. There were no significant differences in mean arterial pressure, cardiac output, or pulmonary artery pressure between the two groups. In the IVOX/permissive hypercapnia group, IVOX CO2 removal increased as a linear function of PaCO2 (y = 0.87x + 8.99, R2 = 0.80). IVOX CO2 removal was only 40 ml/min at normocapnia (40 mm Hg) but increased to 91 ml/min when PaCO2 was 95 mm Hg. Both peak inspiratory pressure and minute ventilation of the IVOX/permissive hypercapnia group were significantly lower than the control group, 30 +/- 4 mm Hg vs 51 +/- 3 mm Hg and 3.9 +/- 0.3 liters vs 8.4 +/- 0.5 liters (P < 0.05) respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

High-pressure destruction kinetics of Listeria monocytogenes on pork

OBJECTIVE: To define the incidence of complications of endotracheal intubation and the factors associated with these complications. STUDY DESIGN: During a 22-month period, 227 intubated infants weighing <1,501 g were followed prospectively in a neonatal intensive care unit. Detailed records of events associated with airway management were kept after every intubation, in addition to clinical data. RESULTS: Eleven infants (4.8%) developed respiratory stridor after extubation which was treated with either systemic corticosteroids, racemic epinephrine and/or reintubation for respiratory failure. Four infants were submitted for bronchoscopy, mild subglottic stenosis with tracheal edema was found in 1 patient, granulation tissue and airway edema were noted in 3 infants. Traumatic intubation, prolonged ventilation, multiple intubations and bacterial colonization of the endotracheal tube were the factors associated with postextubation stridor. CONCLUSIONS: Subglottic stenosis is an infrequent complication of endotracheal intubation with current airway management of very-low-birth-weight infants. Less severe complications are still common, but they are usually amenable to clinical treatment. Bronchoscopy should be performed selectively only in infants with clinical evidence of airway obstruction after extubation.     

Variants in the growth of meningiomas of the base of the skull spreading into the orbit and paranasal sinuses]

PURPOSE: To determine differences in temperature for very low birth weight (VLBW) infants when swaddled and unswaddled in heated, double-walled incubators. DESIGN: A crossover design was used with infants receiving both the swaddled and unswaddled conditions. SAMPLE: 15 very low birth weight infants (< 1,500 gms) with postconceptional ages of 29.1 +/- 1.5 weeks. MAIN OUTCOME VARIABLE: Infant temperature in swaddled and unswaddled conditions. RESULTS: Abdominal temperatures during swaddling were 0.2 degree C higher than the unswaddled condition. In the swaddled condition, infants required a lower incubator temperature (mean = 26.9 +/- 0.4) than when unswaddled (mean = 29.8 +/- 0.5).