Biomedical subjects

A L Coates

Publications and source records attributed to A L Coates.

At least 73 records · Page 4Linked to original sources

PubMed1990

A very low dead space pneumotachograph for ventilatory measurements in newborns.

In premature and full-term neonates, technical limitations hamper the measurements of pulmonary mechanics. Current commercially available pneumotachographs (PNT) either increase the dead space, causing hyperventilation, or increase resistance, thus altering the mechanics of breathing. We modified a previously described low dead space PNT for infants to increase the linear range and frequency response. The mean resistance of the new PNT was 2.44 cmH2O.1-1.s compared with 2.65 cmH2O.1-1.s for the Fleisch no. 0 PNT. The added dead space over the standard endotracheal connector was 0.6 ml compared with 4.7 ml for the Fleisch PNT. Like the Fleisch PNT, the flow resistance was linear from 0 to 15 l/min. In response to a sinusoidal waveform, the new PNT had a phase angle of 21 degrees at 5 Hz and 50 degrees at 16 Hz compared with 19 degrees and 43 degrees, respectively, for the Fleisch PNT. The change in attenuation for both systems was zero until 20 Hz. In summary, the new PNT is lightweight and provides accuracy and low resistance with a very small dead space.

Airway Resistance↗

PubMed1990

The effects of nutritional status and hyperinflation on respiratory muscle strength in children and young adults.

Malnutrition and hyperinflation may both lead to respiratory muscle weakness. To assess separately the effects of chronic hyperinflation and malnutrition on respiratory muscle strength (RMS), 22 subjects with cystic fibrosis (CF) with both hyperinflation and malnutrition were compared to 10 asthmatic patients, a group with hyperinflation without malnutrition, 9 subjects with anorexia nervosa (AN), a group with malnutrition without lung disease, and 14(6 males and 8 females) control subjects with neither compromise. Nutritional status was assessed by body mass percentile (BMP) and percentage ideal weight (PIWT). RMS was diminished in the AN and CF groups (PImax 90 +/- 27, 88 +/- 31 versus 124 +/- 40 cm H2O, p less than 0.05; PEmax 87 +/- 12, 93 +/- 39 versus 121 +/- 32 cm H2O, p less than 0.05), but no difference was found when the AN group was compared with only the female controls. The decrease in PImax in the CF group was primarily due to the mechanical disadvantage placed on the diaphragm by their marked hyperinflation, a mean RV/TLC ratio of 50 +/- 23%. As older CF subjects had previously been shown to have decreased RMS when malnourished, a CF subgroup in the same age range as the controls was evaluated. RMS in this group did not differ from controls despite the presence of malnutrition and hyperinflation. RMS is mildly influenced by nutritional status as assessed by BMP and PIWT but not to any degree of clinical significance.

Adolescent↗

PubMed1989

Nocturnal home oxygen in the treatment of hypoxemic cystic fibrosis patients.

The effect of nocturnal oxygen therapy on mortality and morbidity rates and on progression of disease was tested in a double-blind, randomized trial of 28 subjects with advanced cystic fibrosis. Patients were selected on the basis that their awake arterial oxygen tension was less than 65 mm Hg when they were clinically stable. Oxygen was prescribed in 1 L/min increments to obtain an awake arterial oxygen tension of greater than or equal to 70 mm Hg. Subjects received humidified oxygen or room air from modified concentrators. They were enrolled over a 3-year period and followed for an average (+/- SD) of 26 +/- 9 months. The average number of hours per night of concentrator use was 5.3 +/- 3.2 hours in the air group and 7.0 +/- 1.9 hours in the oxygen group. Over the follow-up period there were four deaths in each group, and oxygen therapy had no significant effect on the frequency of hospitalizations. Progression of disease was ascertained from nutritional status, pulmonary function, blood gas values, exercise ability, and right ventricular ejection fraction response to exercise (as measured by equilibrium-gated radionuclide angiocardiography), and psychologic status was measured by standardized tests of mood, self-esteem, and cognitive function; group comparisons for the first year revealed no significant differences; however, school or work attendance was maintained in the oxygen group but deteriorated in the air group. Clinical signs of cor pulmonale were documented during follow-up in 10 patients in toto, and all lived at least 9 months from the onset of these signs. The lack of association between the onset of these signs and imminent death, or the usefulness of measurements of the maximal oxygen uptake during progressive exercise and the right ventricular ejection fraction response to exercise as prognostic indicators, suggest that death may not be the result of cor pulmonale. We conclude that nocturnal oxygen treatment in patients with cystic fibrosis did not appear to affect mortality rates, the frequency of hospitalizations, or the progression of disease; oxygen use should be instituted only after the development of symptoms related to hypoxemia.

Adult↗

PubMed1989

Liquid-filled esophageal catheter for measuring pleural pressure in preterm neonates.

The precise measurement of esophageal pressure (Pes) as a reflection of pleural pressure (Ppl) is crucial to the measurement of lung mechanics in the newborn. The fidelity of Pes as a measurement of Ppl is determined by the occlusion test in which, during respiratory efforts against an occlusion at the airway opening, changes in pressure (delta Pao) (Pao is assumed to be equal to alveolar pressure) are shown to be equal to changes in Pes (delta Pes). Eight intubated premature infants (640-3,700 g) with chest wall distortion were studied using a water-filled catheter system to measure Pes. During the occlusion test, all patients had a finite region of the esophagus where delta Pes equaled delta Pao, which corresponded to points in the esophagus above the cardia but below the carina. In conclusion, even in the presence of chest wall distortion, a liquid-filled catheter with the tip between the cardia and carina can provide an accurate measurement of Ppl, even in the very small premature infant with chest wall distortion.

Catheterization, Peripheral↗

PubMed1988

Measurement of pulmonary mechanics in the newborn lamb: a comparison of three techniques.

Although recent interest in neonatal respiratory mechanics has led to the development of a plethora of techniques for measuring lung compliance and resistance, a critical appraisal of the limitations of these techniques in the newborn has not been performed to date. We evaluated three techniques of measuring respiratory mechanics in the newborn lamb, with the reference method (method 1) being the Mead-Whittenberger technique using flow, volume, and esophageal pressure (Pes) by water-filled catheter, and the other two methods entailing the measurement of mouth pressure (Pm) during airway occlusion (method 2 using end-expiratory occlusion; method 3 using end-inspiratory occlusion). Each technique was evaluated during eupnea and tachypnea in intubated and nonintubated newborn lambs. We found that the use of Pes for the measurement of resistance and compliance gave the most reliable results during both eupnea and tachypnea in both the intubated and nonintubated subjects. The airway occlusion techniques that use Pm to derive resistance and compliance (methods 2 and 3) gave more variable results under all conditions of testing. Method 2 was the least precise method of measurement with a variability of greater than 30% compared with a variation of less than 20% for method 1. For all three methods, it was found that the number of breaths needed for reproducible measurements of mechanics was four to six during eupnea and seven to nine during tachypnea.

Airway Resistance↗

PubMed1988

Direct measurement of static chest wall compliance in animal and human neonates.

The measurement of pulmonary mechanics has been developed extensively for adults, and these techniques have been applied directly to neonates and infants. However, the compliant chest wall of the infant frequently predisposes to chest wall distortion, especially when there is a low dynamic lung compliance (CL,dyn). We describe a technique of directly measuring the static chest wall compliance (Cw,st), developed initially in the newborn lamb and subsequently applied to the premature neonate with chest wall distortion. The mean CL,dyn in seven intubated newborn lambs in normoxia was 2.45 +/- 0.41 ml.cmH2O-1.kg-1, whereas Cw,st was 11.81 +/- 0.25 ml.cmH2O-1.kg-1. These values did not change significantly in seven animals breathing through a tight-fitting face mask or with hypercapnia-induced tachypnea. For the eight premature infants the mean CL,dyn was 1.35 +/- 0.36 ml.cmH2O-1.kg-1, whereas the mean Cw,st was 3.16 +/- 1.01 ml.cmH2O-1.kg-1. This study shows that, under relaxed conditions when measurements of static compliance are performed, the chest wall is more compliant than the lung. The measurement of Cw,st may thus be used to determine the contribution of the respiratory musculature in stabilizing the chest wall.

Animals↗

PubMed1988

The mechanical effects of expiratory airflow limitation on cardiac performance in cystic fibrosis.

The influence of altered lung mechanics on cardiac performance in cystic fibrosis (CF) was examined in an analysis of cardiorespiratory performance during exercise. The stroke volume (SV) response to exercise, derived from an indirect Fick (CO2) determination of cardiac output during submaximal steady-state exercise served as the index of cardiac performance. The relationship between exercising SV and forced expiratory volume in one second (FEV1), inspiratory duty cycle during exercise (Tl/Ttot) and exercising systemic arterial oxygen tension (PaO2) was examined in 15 studies involving 11 individuals with CF. The subjects were 12 to 25 yr of age and the FEV1 ranged from 15 to 72% predicted. Although a relationship existed between the SV expressed as a percentage of the mean predicted from height and gender (SV%) and PaO2 (r = 0.61, p less than 0.02), a more striking relationship was noted between SV% and either FEV1 or Tl/Ttot (r = 0.79 and 0.73, p less than 0.002). A multiple regression analysis of SV% identified an element of the relationship between FEV1 or Tl/Ttot and cardiac performance which was distinct from the influence of the coexisting hypoxia (p less than or equal to 0.05). The limitation in the SV response to exercise was noted to be in part reversible, coincident with an improvement in ventilatory mechanics that had occurred in 2 of the 4 persons in whom repeated studies were available. These observations suggest that in individuals with CF and a moderately severe degree of expiratory airflow limitation, there is a mechanical element of cardiopulmonary interdependence.

Adolescent↗

PubMed1988

An alternate method for the determination of functional residual capacity in a plethysmograph.

The validity of measuring thoracic gas volume using a single inspiratory effort against an occlusion (Vtginsp) was determined in children and young adults (8 normal control subjects and 17 patients with cystic fibrosis [CF] or asthma). In addition, the validity of the measurement of Vtg at FRC in children at a low panting frequency (Vtgpant) was also determined. During both the panting (encouraged to be about 1 Hz) and inspiratory maneuvers, mouth pressure (Pm) and esophageal pressure (Pes) were measured simultaneously. Hence, Vtgpant and Vtginsp were determined using both delta Pm and delta Pes. Vtginsp using delta Pm was found to be similar to Vtginsp using delta Pes. Values for Vtgpant using either delta Pm or delta Pes were also found to be similar. The percent difference between Vtginsp (using delta Pm) and the average of Vtgpant and Vtginsp (using delta Pes for both) was calculated as an indication of the error of the inspiratory method. The error ranged from -13 to +13% and did not correlate with indices of air-flow limitation or hyperinflation. We have found that Vtginsp can be used to determine FRC in normal children and young adults as well as in those with CF or asthma. In addition, we have also validated the use of Vtgpant at a low panting frequency in these subjects.

Adolescent↗

PubMed1988

The effects of chronic airflow limitation, increased dead space, and the pattern of ventilation on gas exchange during maximal exercise in advanced cystic fibrosis.

Although exertional hypercapnea has been observed in patients with advanced cystic fibrosis (CF), the causes have not been fully elucidated. In 14 patients aged 15 to 35 yr of age with advanced CF, the effects of chronic airflow limitation (CAL), increased physiologic dead space (VD), and the timing components of ventilation (VE) on gas exchange during maximal exercise were assessed. The patients were divided into those who retained CO2 during exercise, the CO2R group, and those who did not, the CO2NR group. CO2 retention was defined as a rise in end-tidal CO2 tension of 5 mm Hg or more or to a value greater than 50 mm Hg during a progressive exercise test on a cycle ergometer. CO2 retention occurred in half the subjects, usually by the halfway mark of the test, and did not rise progressively as exercise continued. It was associated with a low VE caused by a low tidal volume (VT) that was the result of a short inspiratory time to total respiratory time ratio (0.33 +/- 0.03 versus 0.38 +/- 0.04, p less than 0.02), whereas there was no difference in mean inspiratory flow or respiratory rate. Although the CO2R group had the worst CAL, with a FEV1 of 28 +/- 7 versus 41 +/- 12% predicted (p less than 0.5) and a FVC of 42 +/- 12 versus 61 +/- 9% predicted (p less than 0.01), the VT at maximal work expressed as a percentage of FVC was lower (45 +/- 13 versus 60 +/- 11, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1988

Sources of error in flow-volume curves. Effect of expired volume measured at the mouth vs that measured in a body plethysmograph.

The popularity of the maximum expiratory flow-volume curve (FVC) is in part due to the effort independence of expiratory flow. Of interest are expiratory flow rates at specific lung volumes, usually 50 and 25 percent of vital capacity (VC); Vmax50 and Vmax25, which make accurate assessment of lung volumes essential. Changes in lung volume during the test are due to both the volume of gas expired and the volume change due to gas compression (Vcomp). In normal subjects, Vcomp is small but may be considerable in those with airflow obstruction. When the FVC is measured in a plethysmograph (FVCp), both expired volume and Vcomp are measured. When the volume of the FVC is derived from gas expired at the mouth (FVCm), Vcomp is not considered and differences in Vmax25 or Vmax50 may occur. The magnitude of these errors was assessed in 30 children and young adults: nine normal subjects, ten with cystic fibrosis (CF) and 11 with asthma. For Vmax50, use of FVCm instead of FVCp resulted in an error of 8 +/- 7 percent (mean +/- 1 SD) in the normal subjects compared to 32 +/- 23 in those with CF (p less than 0.01) and 24 +/- 18 for those with asthma (p less than 0.05). For Vmax25, the errors were similar. These errors were not predictable from FEV1 or RV/TLC but were related to a combination of expiratory effort, the shape of the FVCp, and the absolute volume of gas that was being compressed (p less than 0.0001). These findings suggest that expiratory flows in the FVCm are not effort-independent in the face of significant airflow obstruction and that comparisons of values derived from an FVCp with those from an FVCm may not be valid.

Adult↗

PubMed1987

Diffusion capacity and oxygen desaturation effects on exercise in patients with cystic fibrosis.

Although a fall in arterial oxygen saturation (SaO2) during exercise has been reported in patients with advanced lung disease due to cystic fibrosis (CF), not every patient with advanced disease desaturates, and pulmonary function tests have not been considered predictive as to which patient will desaturate. This study evaluated oxygen desaturation by ear oximetry during a progressive exercise test in 21 patients with CF and compared it to forced expiratory volume in one second (FEV1), the forced vital capacity (FVC) and the single breath diffusing capacity for carbon monoxide (DCO), all expressed as percent predicted. During exercise, the SaO2 fell less than 0.25 percent per ml of the maximal O2 consumption per kilogram of body weight to values never less than 90 percent in 15 patients (group A), whereas it fell more than this and always to values at the end of exercise of less than 90 percent in six others (group B). The FEV1 ranged from 103 percent predicted to 37 percent for group A compared to 28 to 17 percent in group B, while the range of FEV1/FVC was 87 to 52 percent for group A and 54 to 40 percent for group B. The range of DCO for group A was 129 to 84 percent compared to 64 to 54 percent. In conclusion, this study found that both the FEV1 and the DCO could separate those that had significant desaturation from those that did not and that no patient with a DCO of 80 percent or greater had significant desaturation during exercise.

Adolescent↗

PubMed1987

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.

Adolescent↗

PubMed1987

Pharmacotherapy in bronchopulmonary dysplasia.

This article reviews the current data available on the most frequently used drugs in bronchopulmonary dysplasia. Oxygen, diuretics, bronchodilators, steroids, ribavirin, and antioxidants, as well as medication available for pulmonary hypertension, systemic hypertension, and gastroesophageal reflux are discussed, with emphasis on known advantages, side effects, and current dosage.

Antioxidants↗

PubMed1986

Measuring the oxygen cost of breathing in normal adults and patients with cystic fibrosis.

It has been suggested that the oxygen consumption of the respiratory muscles (VO2 resp) may play a role in limiting exercise performance in both healthy subjects and those with chronic airflow limitation (CAL). In order to measure VO2 resp reproducibly at both rest and on exercise, ventilation (VE) and total oxygen consumption (VO2) in 3 normal subjects and in 3 patients with cystic fibrosis were measured while breathing air and again when VE was stimulated by the addition of CO2 to the inspired gas. Since external work was the same it was assumed that any changes in VO2 would be due to the increase in VO2 resp during stimulated breathing allowing for the calculation of VO2 resp. The oxygen cost of breathing was higher in the patients with the increasing ventilation of exercise. These values were reproducible on repetitive measurements. It is concluded that the method employed is applicable in normal subjects and in patients with CAL, and that the O2 cost of breathing is higher in patients with CAL. The O2 cost of breathing increases as VE increases but even during exercise the VO2 resp is only a small fraction of the total VO2 and is unlikely to be a determining factor limiting exercise performance in either normal subjects or those with CAL.

Adult↗

PubMed1986

Family support system in newborn medicine: does it work? Follow-up study of infants at risk.

Acute illness in early childhood generates chronic anxiety in parents, which may manifest itself in part by inappropriate use of health care. To minimize this and the development of other psychosocial sequelae associated with neonatal illness, a family support system (FSS) was developed and implemented in a neonatal intensive care unit. The effectiveness of the FSS was assessed by the evaluation of emergency room and inpatient hospital service utilization in 80 patients born before, and 90 patients born after the institution of the program. At the outset, the groups had similar medical and social characteristics. There was no difference between the two groups in the utilization of emergency services in the first year after discharge. However, during the second year the control group used the emergency room twice as often as the study group did (P less than 0.025). During the first 2 years, half of the control group was readmitted, compared with less than a third of the study group (P less than 0.005). Overall, after discharge from the neonatal intensive care unit the control group spent an average of 9 days per patient in hospital, compared with a mean of 3 days per patient in the study group (P less than 0.025). It appears, therefore, that the FSS may be an effective way to reduce some of the psychosocial sequelae of illness in newborn infants requiring intensive care.

Adolescent↗

PubMed1986

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.

Adolescent↗

PubMed1985

The long-term pulmonary sequelae of prematurity: the role of familial airway hyperreactivity and the respiratory distress syndrome.

Respiratory distress syndrome of the newborn, prematurity, and familial airway hyperreactivity may contribute to long-term pulmonary sequelae. We assessed the role of each by testing pulmonary function and airway reactivity in 11 prematurely born children who survived the respiratory distress syndrome and in 11 prematurely born children who had no neonatal respiratory disease, each of whom was paired with a sibling born at term. The subjects were between 7 and 12 years of age when studied. Airway reactivity was also assessed in their mothers. The group who had had the respiratory distress syndrome had higher ratios of residual volume to total lung capacity and lower values for forced expiratory volume in one second than did their siblings or normal controls (P less than 0.01). Expiratory flow was decreased in both groups born prematurely (P less than 0.02) and was related to neonatal exposure to oxygen (r = -0.71, P less than 0.02). The incidence of airway hyperreactivity was elevated in all groups, including the mothers. These data suggest that long-term pulmonary sequelae of the respiratory distress syndrome of the newborn are related to the disease, its treatment, or both, and to airway hyperreactivity. In prematurely born children without neonatal lung disease, the sequelae are related to airway hyperreactivity. The possibility of a relation between familial airway hyperreactivity and premature birth is suggested.

Airway Obstruction↗

PubMed1985

Simplified oxygen administration in tracheostomized patients with bronchopulmonary dysplasia.

The report describes a simple effective system of meeting the oxygen requirements of tracheostomized infants in the home setting. It consists of oxygen tubing which may be run under the infant's clothing and connected to the tracheostomy tube through a specially created hole. This allows a continuous administration of oxygen while minimizing the risk of accidental decannulation of disconnection by the infant grabbing the oxygen tubing. This has been used successfully in the management of infants with tracheostomies and chronic oxygen needs due to bronchopulmonary dysplasia.

Bronchopulmonary Dysplasia↗