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Biomedical subjects

K E Finucane

Publications and source records attributed to K E Finucane.

At least 19 recordsLinked to original sources
PubMed1995

Application of a cervical stimulating apparatus for bilateral transcutaneous phrenic nerve stimulation.

Transcutaneous bilateral phrenic nerve stimulation (tPNS) is frequently used to assess diaphragmatic function in humans. Commonly, stimulation is performed with hand-held electrodes; however, these are unsuitable for studies requiring repeated PNS and where recruitment of rib cage and neck muscles may shift the probes in relation to the nerves. In this study we describe the design of a cervical neck brace and electrode probes that maintain stimulating electrodes in constant position relative to the phrenic nerves and facilitates studies requiring repeated maximal PNS. The effectiveness of the apparatus was examined by 1) reviewing the reproducibility of the transdiaphragmatic pressure response to 0.1 ms tPNS (PdiT) at relaxed functional residual capacity in four subjects studied on 25 +/- 8 (SD) occasions (> or = 24 h apart) over a 4-yr period, and 2) measuring peak-to-peak amplitude of the left and right diaphragmatic compound muscle action potentials (surface electrodes) during two prolonged studies (38 +/- 9 min) in each subject, when tPNS was performed during repeated submaximal and maximal inspiratory efforts. PdiT was reproducible in each subject when measured repeatedly within a single study [coefficient of variation (CV) of 3.8 +/- 0.8%] and over separate days (CV of 11.5 +/- 3.5%). The peak-to-peak amplitudes of the left and right compound muscle action potentials were also reproducible (CV of 8.4 +/- 4.3 and 8.4 +/- 2.9%, respectively) and independent of the degree of effort. The apparatus appears effective for the maintenance of maximal stimulation under varied conditions for long periods and provides reproducible measurements of PdiT both within and between studies.

Action Potentials↗
PubMed1992

Comparison of balloon and transducer catheters for estimating lung elasticity.

Pleural pressure is usually estimated with a balloon catheter (BC) positioned in the middle third of the esophagus. An alternate method, which avoids potential inaccuracies associated with changes in balloon volume, is a catheter-mounted transducer (CMT) system. To assess the accuracy of a CMT system in defining the elastic properties of the lungs, we compared the static pressure-volume (PV) properties of the lungs measured sequentially with CMT and BC systems in six healthy subjects each on two occasions, relating static transpulmonary pressure (Pst,L) to lung volume during interrupted exhalations from total lung capacity (TLC). PV data were fitted with an exponential function (least-squares method), and the exponent (k) was used to define the shape of the PV curve; position was defined by Pst,L at TLC and at 90 and 60% TLC. These data were examined for agreement (paired t test) and repeatability (coefficient of repeatability). No significant differences were demonstrated: k was 0.10 +/- 0.02 and 0.11 +/- 0.03 (SD) and Pst,L at 60% TLC was 8.27 +/- 2.09 and 8.37 +/- 1.63 cmH2O for the CMT and BC systems, respectively. The coefficient of repeatability for each parameter was not significantly different but was consistently less with the BC, suggesting better repeatability. We conclude that a CMT system is an acceptable alternative to a BC system for defining the elastic properties of lungs.

Adult↗
PubMed1990

Effect of abdominal compression on maximum transdiaphragmatic pressure.

Transdiaphragmatic pressure (Pdi) is lower during maximum inspiratory effort with the diaphragm alone than when maximum inspiratory and expulsive efforts are combined. The increase in Pdi with expulsive effort has been attributed to increased neural activation of the diaphragm. Alternatively, the increase could be due to stretching of the contracted diaphragm. If this were so, Pdi measured during a combined maximum effort would overestimate the capacity of the diaphragm to generate inspiratory force. This study determined the likely contribution of stretching of the contracted diaphragm to estimates of maximum Pdi (Pdimax) obtained during combined inspiratory and expulsive effort. Three healthy trained subjects were studied standing. Diaphragmatic Mueller maneuvers were performed at functional residual capacity and sustained during subsequent abdominal compression by either abdominal muscle expulsive effort or externally applied pressure. Measurements were made of changes in abdominal (Pab) and pleural (Ppl) pressure, Pdi, rib cage and abdominal dimensions and respiratory electromyograms. Three reproducible performances of each maneuver from each subject were analyzed. When expulsive effort was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 86 +/- 12 to 148 +/- 14 (SD) cmH2O within the 1st s and was 128 +/- 14 cmH2O 2 s later. When external compression was added to maximum diaphragmatic inspiratory effort, Pdimax increased from 87 +/- 16 to 171 +/- 19 cmH2O within the 1st s and was 152 +/- 16 cmH2O 2 s later.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1989

Preoperative assessment as a predictor of mortality and morbidity after lung resection.

To refine the functional guidelines for operability for lung resection, we prospectively studied 55 consecutive patients with suspected lung malignancy thought to be surgically resectable. Lung function and exercise capacity were measured preoperatively and at 3 and 12 months postoperatively. Preoperative pulmonary scintigraphy was used to calculate the contribution to overall function by the affected lung or lobe and to predict postoperative lung function. Pneumonectomy was performed in 18 patients, lobectomy in 29, and thoracotomy without resection in six. No surgery was attempted in two patients who were considered functionally inoperable. Cardiopulmonary complications developed in 16 patients within 30 days of surgery, including three deaths. The predictions of postoperative function correlated well with the measured values at 3 months. For FEV1, r = 0.51 in pneumonectomy (p less than 0.05) and 0.89 in lobectomy (p less than 0.001). Predicted postoperative FEV1 (FEV1-ppo), diffusing capacity (DLCO), predicted postoperative DLCO (DLCO-ppo) and exercise-induced arterial O2 desaturation (delta SaO2) were predictive of postoperative complications including death and respiratory failure. In patients who underwent pneumonectomy, the best predictor of death was FEV1-ppo. The predictions were enhanced by expressing the value as a percentage of the predicted normal value (% pred) rather than in absolute units. For the entire surgical group a FEV1-ppo greater than or equal to 40% pred was associated with no postoperative mortality (n = 47), whereas a value less than 40% pred was associated with a 50% mortality (n = 6), suggesting that resection is feasible when FEV1-ppo is greater than or equal to 40% pred.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Bronchial responsiveness, lung mechanics, gas transfer, and corticosteroid response in patients with chronic airflow obstruction.

Thirty patients with stable chronic airflow obstruction receiving regular bronchodilator treatment were studied to determine whether the level of bronchial responsiveness, transfer factor for carbon monoxide (TLCO), or the mechanical properties of the lung predicted a bronchodilator response to oral corticosteroid treatment. Before treatment mean (SD) FEV1 was 48% (16%) of the predicted value (% pred); the geometric mean concentration of methacholine required to produce a 20% fall in FEV1 (PC20) was 0.44 (range 0.07-3.32) mg/ml; and TLCO was 59% (21%) predicted. The exponential constant (k) defining the shape of the static volume-pressure curve was 146% (66%) predicted and pulmonary conductance relative to predicted lung volume at a transpulmonary pressure of 5 cm H2O (sGL5) was 72% (37%) predicted. After prednisolone treatment (0.6 mg kg-1 day-1 for two weeks) FEV1 increased by 8% (19%) (p less than 0.05) and daily mean peak flow (PEF) by 3% (10%) (p less than 0.01) over pretreatment values. Three patients had an increase in FEV1 of more than 30%, two of whom had sputum eosinophilia (p less than 0.05). The three were among the 13 patients with a reduced sGL5. The increase in FEV1 did not correlate with initial PC20 (r = 0.16), k (r = -0.12), or TLCO (r = -0.14). Thus measurements of bronchial responsiveness, lung distensibility, and TLCO did not predict corticosteroid response in patients with stable chronic airflow obstruction. Patients with sputum eosinophilia or reduced pulmonary conductance may be more likely to respond.

Airway Resistance↗
PubMed1988

Functional similarities of asbestosis and cryptogenic fibrosing alveolitis.

The pathological features in the lung in asbestosis and cryptogenic fibrosing alveolitis are similar. Patients with asbestosis, however, appear to have less severe impairment of transfer factor (TLCO) than those with fibrosing alveolitis for a given level of radiographic abnormality when assessed on the basis of the International Labour Organisation (ILO) profusion score. The impairment of lung function in the two disorders has been compared in more detail in 29 patients with asbestosis and 25 with fibrosing alveolitis, arterial oxygen desaturation during exercise being used to define the severity of the disorders. Arterial oxygen saturation (ear oximeter) and oxygen uptake were measured during incremental exercise on a cycle ergometer. TLCO (single breath technique) and total lung capacity (TLC, plethysmograph) were measured. Chest radiographs were graded for profusion according to the ILO international classification. Patients with asbestosis had significantly higher mean values for TLCO and TLC and lower mean profusion scores than those with fibrosing alveolitis. When stratified for the degree of arterial oxygen desaturation, however, no significant differences were found in TLCO, TLC, or profusion score between the two disorders. To the extent that arterial oxygen desaturation with exercise reflects the morphological severity of the disease, these results suggest that, for a given degree of interstitial lung disease, asbestosis and cryptogenic fibrosing alveolitis are functionally and radiologically similar.

Asbestosis↗
PubMed1988

Respiratory pressure partitioning during quiet inspiration in unilateral and bilateral diaphragmatic weakness.

To compensate for diaphragmatic weakness, intercostal/accessory muscles may be recruited in inspiration and/or abdominal muscles in expiration with relaxation during subsequent inspiration. As a consequence, for a given decrease in pleural pressure (Ppl) during quiet inspiration (qi), abdominal pressure (Pab) should either undergo a smaller increase than normal or, in severe cases, decrease. If so, the ratio of change in Pab to Ppl during qi (delta Pab/delta Ppl(qi], which is normally less than -1 when upright, should increase, approaching +1 in profound diaphragmatic weakness. To examine the relationship between degree of diaphragmatic weakness and delta Pab/delta Ppl(qi), we measured (erect and supine) anteroposterior rib cage and abdominal motion, Pab, Ppl, and transdiaphragmatic pressure (Pdi) during qi, maximal inspiration (Pdi(max)mi) and maximal inspiratory effort at FRC (Pdi(max)FRC) in 10 patients with bilateral and 8 with unilateral diaphragmatic weakness. Pdi(max)mi and Pdi(max)FRC were low in all patients. delta Pab/delta Ppl(qi) (erect) was increased in all patients (0.28 +/- 0.7; mean +/- SD) and correlated closely with both Pdi(max)mi (r = -0.89, p less than 0.001) and Pdi(max)FRC (r = -0.76, p less than 0.001). There was extensive overlap in the data between unilateral and bilateral diaphragmatic weakness. The ratio of delta Pdi during qi to Pdi(max)FRC was less than 0.31 in all patients. The results suggest that delta Pab/delta Ppl(qi) is a useful index of the degree of diaphragmatic weakness and that the functional consequences of unilateral and bilateral weakness are not rigidly separable.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1988

Arterial oxygen saturation in anaesthetised patients during transfer from induction room to operating room.

There is no published study that examines oxygenation of anaesthetised patients during transport from anaesthesia induction room to operating room. Arterial oxygen saturation (SaO2) was measured in twenty-five anaesthetised patients before and during transfer to an adjacent operating room and continuously recorded on a calibrated chart recorder. A telemetry ECG recorder was used to detect cardiac dysrhythmias. All anaesthetists followed their usual anaesthetic practice. Patients ventilated via face-mask and via endotracheal tube were studied. During transfer patients were either apnoeic (n = 8) or breathing room air spontaneously (n = 17). Mean SaO2 before induction was 95.4 (SD 2.5)%, was higher after induction of anaesthesia, 98.5 (SD 1.4)% and fell after transfer, 95.7 (SD 2.6)%. A fall in SaO2 was recorded for 21 patients. No SaO2 value below 90% was seen. The decrease in SaO2 was related to the time taken to transfer the patients and spontaneous ventilation (Multiple regression analysis); it was not related to the body mass index although two of the greatest decreases were seen in obese patients. Transfer time averaged 51 seconds (range: 24-97 s). No changes in cardiac rhythm were seen. Transfer of anaesthetised patients was accompanied by variable falls in SaO2 which related to duration of transfer and spontaneous breathing of room air and which were not associated with new dysrhythmias.

Adult↗
PubMed1987

Minimizing work of breathing with continuous positive airway pressure and intermittent mandatory ventilation: an improved continuous low-flow system.

Minimizing work of breathing (WOB) during intermittent mandatory ventilation (IMV) and continuous positive airway pressure (CPAP) is important as it facilitates weaning from mechanical ventilation. To minimize WOB, we devised a simple, continuous-flow CPAP-IMV system that uses a weighted, partially filled reservoir bag and operates efficiently at low fresh gas flow (FGF). We compared both the pattern and WOB of our system (FGF at 15 L/min) with a conventional continuous-flow CPAP/IMV system (FGF at 15 and 30 L/min) as well as with two relatively efficient demand-value systems, the Servo 900 B and 900 C. Six healthy male subjects were studied; tidal volumes (VT), flow, mouth pressure, and pleural pressure (Ppl) were measured. Ten breaths, matched for VT, from each subject on each system were selected for analysis. Mechanical WOB was estimated by integrating Ppl with respect to VT. The conventional continuous-flow system was associated with a high work/breath relative to the other systems (p less than .001). The weighted reservoir system was associated with a significantly lower work/breath (p less than .001), its performance approaching that of the Servo 900B. Work/breath was least with the Servo 900C (p less than .001). As breathing frequency was higher with the demand valve than continuous-flow systems (p less than .001), the difference in work/time was minimal between the weighted reservoir bag and demand-valve systems. These systems were all associated with significantly (p less than .001) lower work/time than the conventional system at both FGF.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

A model of the respiratory pump.

The interaction of forces that produce chest wall motion and lung volume change is complex and incompletely understood. To aid understanding we have developed a simple model that allows prediction of the effect on chest wall motion of changes in applied forces. The model is a lever system on which the forces generated actively by the respiratory muscles and passively by impedances of rib cage, lungs, abdomen, and diaphragm act at fixed sites. A change in forces results in translational and/or rotational motion of the lever; motion represents volume change. The distribution and magnitude of passive relative to active forces determine the locus and degree of rotation and therefore the effect of an applied force on motion of the chest wall, allowing the interaction of diaphragm, rib cage, and abdomen to be modeled. Analysis of moments allow equations to be derived that express the effect on chest wall motion of the active component in terms of the passive components. These equations may be used to test the model by comparing predicted with empirical behavior. The model is simple, appears valid for a variety of respiratory maneuvers, is useful in interpreting relative motion of rib cage and abdomen and may be useful in quantifying the effective forces acting on the rib cage.

Animals↗
PubMed1986

The pattern of breathing in acute severe asthma.

The pattern of breathing was studied in 8 patients with acute severe asthma on admission to hospital and during recovery to determine how chest wall motion varied with the degree of air-flow obstruction (AO), the relationship between degree of AO and respiratory timing and ventilation, and whether the pattern suggested respiratory muscle fatigue when asthma was most severe. Pattern was assessed by simultaneous measurement of respired volumes (pneumotachygraph) and anteroposterior (AP) motion of lower rib cage and abdomen (magnetometers). There was a phase lag of AP rib cage relative to AP abdominal motion that was greatest in those with lowest FEV1 and progressively decreased during recovery. Fractional inspiratory time was decreased in severe asthma. Mean inspiratory flow was increased in moderately severe asthma but decreased when FEV1 was less than 25% predicted. Breathing pattern was no more variable during severe asthma than during recovery. We conclude that during severe AO the magnitude of phase lag of AP rib cage relative to AP abdominal motion reflects severity of asthma; respiratory drive is increased but is not associated with increased ventilation below an FEV1 of 25% predicted, and analysis of the breathing pattern provides no clear evidence of respiratory muscle fatigue.

Abdominal Muscles↗
PubMed1985

Irreversible airflow obstruction. Evolution in asthma.

To determine whether asthma can cause irreversible airflow obstruction (IAO) 89 subjects with uncomplicated asthma received intensive treatment for four weeks. FEV1 was measured at 0, two and four weeks; pulmonary elasticity and flow resistance was measured in 46 of the subjects at four weeks. Severity of asthma and cigarette consumption were ascertained by a questionnaire. The mean difference between the predicted and highest FEV1 during treatment was 0.29 L (P less than 0.001). The highest FEV1% predicted correlated (P less than 0.001) with the duration and severity of asthma in the entire group, in the 51 nonsmokers, and in the 47 subjects with the adult onset of asthma. Pulmonary resistance, but not elastic recoil, correlated with the duration and severity of asthma (P less than 0.01). The results show that chronic asthma can cause narrowed airways and IAO, and suggest that this may be prevented by improved control of asthma.

Adrenal Cortex Hormones↗
PubMed1985

Continuous positive airway pressure: a breathing system to minimize respiratory work.

During continuous positive airway pressure (CPAP) the work of breathing is least when there is no change of airway pressure measured at the mouth (delta Paw) during respiration. In this study we consider the physical properties of CPAP circuits which determine the magnitude of delta Paw, and apply this information to the design of a simple, reliable CPAP system that minimizes delta Paw and incorporates the additional advantages of low-flow rates and the use of commonly available proven components. Using a weighted reservoir bag and threshold CPAP valve to maintain pressure, we found that delta Paw may be reduced to less than 1.0 cm H2O during quiet breathing, at a tidal volume of 700 ml and maximum inspiratory flow of 1.35 L/sec. delta Paw was dependent on both the resistance and the reactance of the circuit components; it was increased when resistance or flow rates were high, and when delivery pressure depended on the elastic tension in the wall of the reservoir bag or on compression of the bag with springs or elastic bands.

Equipment Design↗
PubMed1984

Asthma and irreversible airflow obstruction.

To determine whether asthma alone can cause irreversible airflow obstruction 42 men and 47 women with chronic asthma (mean duration 22 (SD 13) years) without evidence of other disease likely to cause irreversible airflow obstruction were treated with theophylline orally and a beta agonist both orally and by inhalation for four weeks. After two weeks of treatment the FEV1 was less than 85% of the predicted normal value (%P) in 48 patients and these individuals then received prednisolone 0.6 mg/kg/day for two weeks. Duration and severity of asthma and smoking history were quantified by questionnaire; 38 patients were current smokers or ex-smokers. FEV1 was measured at 0, 2, and 4 weeks. The mean difference between the best FEV1 during the study and the predicted normal value was 0.29 l (p less than 0.001); FEV1 %P decreased with age (r = -0.30, p less than 0.01) and with the duration (r = -0.47, p less than 0.001) and severity (r = -0.55, p less than 0.001) of asthma. Similar findings were noted when the results for non-smokers and those whose asthma started in adult life were analysed separately. We conclude that asthma alone can cause irreversible airflow obstruction and that the degree of obstruction is a function of the duration and severity of previous asthma. The results suggest the possibility that irreversible airflow obstruction in asthma may be preventable by minimising the degree of persistent asthma.

Adult↗
PubMed1984

Lung function in diffuse interstitial lung disease of unknown cause.

To examine the role of lung function tests in diagnosis and management of patients with diffuse interstitial lung disease (DILD) we measured total lung capacity (TLC), gas transfer (Tl), lung distensibility and arterial saturation (SaO2) and ventilation during progressive exercise in 24 patients with DILD including 18 with biopsy confirmation. Tl was decreased in all patients, in 21/24 there was progressive hypoxia with exercise, in 12/24 TLC was greater than 80% predicted and in 6/18 lung distensibility was normal. Tl and the change of SaO2 with work output during exercise were highly correlated (r = -0.65, p less than 0.001). In serial studies, the change of SaO2 with work output altered most with clinical improvement or deterioration. The clinical course and response to treatment was not related to a particular pattern of abnormal function. These results and those of previous studies indicate that in DILD the most sensitive index of abnormal parenchymal function is Tl, that lung volumes and distensibility may be normal so that the term "restrictive lung disease" can be misleading, that the fall of SaO2 with work output and Tl are the most sensitive parameters for assessing severity and following the course of the disease and that lung function alone does not predict outcome.

Adult↗