Exercise testing and prognosis in adult cystic fibrosis

BACKGROUND: The assessment of prognosis is an important issue in cystic fibrosis. The prognostic value of exercise testing in comparison with other predictors of mortality was examined. METHODS: Ninety two adult patients with cystic fibrosis performed progressive maximal exercise tests and outcome was assessed at five years. The results of exercise testing were examined along with spirometric values, age, sex, body mass index (BMI), and sputum culture. RESULTS: Twenty two subjects died during the five year follow up period and 67 survived. Five subjects received a lung transplant and were excluded from the analysis. There were significant differences between those who survived and those who died: mean (SE) forced expiratory volume in one second (FEV1) 68.9 (2.7) versus 39.7 (3.5)% predicted, BMI 19.0 (0.3) versus 17.1 (0.4) kg/m2, peak oxygen uptake (VO2 peak) 66.6 (2.2) versus (53.7) (3.7)% predicted, peak work rate (Wpeak) 89.4 (3.8) versus 71.2 (5.5)% predicted, peak minute ventilation (VEpeak) 51.3 (2.0) versus 43.3 (3.1) 1/min, and ventilatory equivalent for oxygen (VE/VO2) 32.4 (0.6) versus 38.7 (1.7). Age, sex, oxygen saturation and Burkholderia cepacia colonisation were not found to be significant predictors of mortality. When significant independent factors were entered into a multivariate logistic regression model only FEV1 was found to be a significant correlate of mortality. A cutoff for FEV1 of 55% predicted gave the best combination of specificity and sensitivity with 54% of those below this value dying within five years and 96% of those above it surviving. CONCLUSIONS: The results of maximal exercise testing are correlated with survival but they are not better than the FEV1 as prognostic indicators.


     

Orthostatic increase of respiratory gas exchange in hyperventilation syndrome

BACKGROUND: Hyperventilation syndrome (HVS) is a common disorder which is difficult to diagnose because of somatic symptoms and its episodic nature. In previous studies respiratory alkalosis in arterial blood was often found during orthostatic tests in patients with HVS. The purpose of this study was to assess these orthostatic changes by non-invasive pulmonary gas exchange measurements and to evaluate whether these responses discriminate patients with HVS from healthy subjects. METHODS: Respiratory gases were collected with a face mask and pulmonary gas exchange was measured after 10 minutes at rest and after eight minutes standing upright in 16 patients with HVS and 13 healthy control subjects. In patients with HVS arterial blood samples were also drawn at rest and in the standing position. RESULTS: At rest the variables of respiratory gas exchange did not differ significantly between the groups. As a response to standing, minute ventilation increased in both study groups but significantly more in the patients with HVS (mean difference 5.4 l/min (95% CI 1.1 to 9.6)). The changes in end tidal CO(2) fraction (FETCO(2)) and in ventilatory equivalents for oxygen (VE/VO(2)) and for CO(2) (VE/VCO(2)) during the orthostatic test were also significantly larger in patients with HVS than in healthy controls. During standing FETCO(2) was significantly lower (mean difference -1.1 kPa; 95% CI -1.5 to -0.6) and VE/VO(2) (mean difference 18.4; 95% CI 7.7 to 29.0) and VE/VCO(2) (mean difference 11.7; 95% CI 4.8 to 18.6) were significantly higher in HVS patients than in healthy controls. By using the cut off level of 4% for FETCO(2) the sensitivity and specificity of the test to discriminate HVS were 87% and 77%, respectively, and by using the cut off level of 37 for VE/VO(2) they were 93% and 100%, respectively. In the HVS patients arterial PCO(2) and FETCO(2) were closely correlated during the orthostatic test (r = 0.93, p<0.0001). CONCLUSIONS: As a response to change in body position from supine to standing, patients with HVS have an accentuated increase in ventilation which distinguishes them from healthy subjects. These findings suggest that non-invasive measurements of pulmonary gas exchange during orthostatic tests are useful in the clinical evaluation of patients with hyperventilation disorders.     

Exercise-related ventilatory abnormalities are more specific for functional impairment in chronic heart failure than reduction in peak exercise oxygen consumption.

BACKGROUND: Impaired functional capacity during exercise is used to assess need for transplantation in congestive heart failure patients, although impaired capacity is present in several chronic illnesses. The purpose of this study was to test the hypothesis that ventilatory abnormalities during exercise, rather than functional capacity, are specific to congestive heart failure patients. METHODS: We compared exercise-related gas exchange among a group of congestive heart failure patients and a group of patients who had chronic liver disease and normal cardiac function, matched for functional impairment, and a group of normal controls. RESULTS: Patients with congestive heart failure and patients with chronic liver disease experienced marked reduction in peak exercise oxygen consumption compared with normal controls (14.0 +/- 1.4 and 14.2 +/- 3.7 ml/kg/min, respectively, vs 25.8 +/- 5.6 ml/kg/min, p < 0.01). Minute ventilation at peak exercise was significantly higher in congestive heart failure subjects than in chronic liver disease patients (59.3 +/- 16.8 liter/min vs 41.4 +/- 14.2 liter/min, p < 0.05), although carbon dioxide production was similar (1,380 +/- 308 ml vs 1,180 +/- 389 ml, p = not significant), so that the ratio of minute ventilation to carbon dioxide production (ventilatory equivalent for carbon dioxide, an index of ventilatory drive) was significantly elevated in congestive heart failure subjects (43 +/- 9 vs 36 +/- 7, p < 0.05). CONCLUSIONS: Although functional impairment characterizes both congestive heart failure and chronic liver disease, only congestive heart failure patients exhibit exercise-related ventilatory abnormalities. Exercise-related ventilatory abnormalities may be more specific to the underlying pathophysiology of chronic heart failure and should be considered when evaluating patients for heart transplantation.     

Effect of theophylline on exercise performance in patients with severe chronic obstructive pulmonary disease.

BACKGROUND--Theophylline is a well known bronchodilator which has been used for more than 50 years in the treatment of obstructive pulmonary diseases. In patients with severe chronic obstructive pulmonary disease whose cardiopulmonary performance is limited by their ventilatory capacity the administration of theophylline may improve exercise performance. METHODS--A randomised, placebo controlled, double blind, crossover trial was conducted in 22 patients with severe but stable disease. The patients (mean age 68 years) were studied before and after one month of placebo and one month of treatment with a sustained release preparation of theophylline administered orally. The theophylline dose was adjusted until a blood level above 55.5 mumol/l was achieved. The two treatments were administered in random order and separated by a two week washout period. After theophylline was administered for one month a mean level of 68.2 mumol/l was achieved. Pulmonary function tests, arterial blood gas measurements, maximal voluntary ventilation (MVV), and an incremental exercise test were performed before (baseline) and at the end of the first and second month of treatment. RESULTS--Pulmonary function tests showed no improvement in the flow parameters but showed an improvement in MVV after treatment with theophylline. Pulmonary gas exchange was improved after theophylline (resting arterial PO2 8.91 v 8.59 kPa, PCO2 5.38 v 5.56 kPa). The incremental exercise study showed improvement in maximal work rate (86.5 v 75.0 watts) and maximal ventilation (VEmax) (46.7 v 43.01/min). The dyspnoea index on maximal effort (VEmax/MVV), anaerobic threshold, and oxygen pulse remained unchanged. Resting and exercise heart rate were higher after theophylline. CONCLUSIONS--Theophylline improved cardiorespiratory performance in these patients with severe chronic obstructive pulmonary disease mainly by increasing the ventilatory capacity.     

Pulmonary oxidative stress response in young children with cystic fibrosis

BACKGROUND: It has been suggested that oxidative stress contributes to lung injury in cystic fibrosis. There is, however, no direct evidence of increased pulmonary oxidative stress in cystic fibrosis nor of the effects of inflammation on the major pulmonary antioxidant, glutathione. A study was undertaken to measure these parameters in infants and young children in the presence or absence of pulmonary inflammation. METHODS: Thirty two infants and young children with cystic fibrosis of mean (SD) age 21.4 (15.3) months (range 2-54) and seven non-cystic fibrosis control subjects of mean (SD) age 21.0 (21.2) months (range 2-54) were studied using bronchoalveolar lavage (BAL). On the basis of the BAL findings the cystic fibrosis group was divided into those with (CF-I) and those without pulmonary inflammation (CF- NI). Levels of lipid hydroperoxide, total glutathione, and gamma- glutamyl transpeptidase (gamma-GT) were then measured in the BAL fluid. RESULTS: The concentrations of lipid hydroperoxide and gamma-GT in the epithelial lining fluid were significantly increased in the CF-I group compared with the control and CF-NI groups, each of which had similar values for these parameters (ratio of geometric means for CF-I group versus control for lipid hydroperoxide 5.4 (95% confidence interval (CI) 1.8 to 15.8) and for gamma-GT 5.2 (95% CI 1.4 to 19.4)). The glutathione concentration tended to be lower in the CF-I subjects but the difference did not reach statistical significance. CONCLUSIONS: These results demonstrate that the airways in patients with cystic fibrosis are exposed to increased oxidative stress which appears to be a consequence of pulmonary inflammation rather than part of the primary cystic fibrosis defect. The increase in gamma-GT in the CF-I group suggests a mechanism by which extracellular glutathione could be utilised by airway epithelial cells.


     

Individualised unsupervised exercise training in adults with cystic fibrosis: a 1 year randomised controlled trial

BACKGROUND: Short term studies of exercise training have shown benefits in cystic fibrosis. Transferring exercise programmes to the community and sustaining them long term is a challenge for the patient. The effectiveness of an individualised unsupervised home based exercise programme was examined in adults with cystic fibrosis over a 1 year period. METHODS: Subjects were randomised to undertake three sessions per week of upper and lower body exercise based on individualised preferences (n = 30) or to a control group (n = 18). They were evaluated at baseline and at 12 months. The primary outcome measure was improved fitness as assessed by change in blood lactate concentration at the end of an identical constant work rate for both arm and leg ergometric testing. Secondary outcome measurements were heart rate and pulmonary function. RESULTS: For leg exercise, significant differences were seen at 12 months between the active and control groups in the mean (SE) change in blood lactate levels (-0.38 (0.23) mmol/l v 0.45 (0.25) mmol/l, p<0.05) and heart rate (-4.8 (2.5) bpm v 3.4 (2.5) bpm, p<0.05), confirming a training effect. For arm ergometry there was no change in lactate levels at 12 months but there was a significant difference in forced vital capacity (46 (72) ml v -167 (68) ml, p<0.05). CONCLUSIONS: A training effect, as measured by a reduction in lactate levels and heart rate, can be achieved with unsupervised individualised home exercise in adults with cystic fibrosis. A benefit to pulmonary function was observed and together these findings suggest that exercise programmes should be encouraged as an important component of care in cystic fibrosis.     

Lung function, hypoxic and hypercapnic ventilatory responses, and respiratory muscle strength in normal subjects taking oral theophylline.

Methylxanthines are known to be respiratory stimulants and are thought by some to augment hypercapnic and hypoxic ventilatory drive and improve respiratory muscle strength. Hypoxic and hypercapnic ventilatory responses were measured in 10 normal subjects before, during, and after administration of theophylline for three and a half days. Pulmonary function, carbon dioxide production, and mouth pressures during maximal static inspiratory and expiratory efforts were also measured. The mean (SD) serum theophylline concentration was 13.8 (3.2) mg/l. Lung volumes and flow rates did not change significantly with theophylline. The mean (SD) values for maximum static inspiratory pressure were 152 (27), 161 (25), and 160 (24) cm H2O, respectively before, during, and after theophylline. Neither these values nor peak expiratory pressure measurements were significantly changed. The slopes of the hypercapnic ventilatory responses were 2.9 (0.9), 3.3 (1.2), and 3.3 (1.4) l/min/mm Hg carbon dioxide tension (PCO2) respectively before, during, and after theophylline administration. The respective values for the slopes of the hypoxic response were -1.4 (0.9), -1.3 (0.8), and -1.1 (0.9) l/min/1% oxyhaemoglobin saturation. None of these values changed significantly with theophylline. Theophylline, however, increased carbon dioxide production (200 to 236 ml/min) and alveolar ventilation (4.7 to 5.7 l/min) significantly, with a concomitant fall of end tidal PCO2 (35.5 to 32.9 mm Hg). It is concluded that in man oral theophylline at therapeutic blood concentrations increases carbon dioxide production and ventilation without changing pulmonary function, respiratory muscle strength, or the hypoxic or hypercapnic ventilatory response significantly.     

The Influence of Weight Loss on Anaerobic Threshold in Obese Women

Obesity is associated with decreased physical activity. The aim of the study was to assess the anaerobic threshold in obese and normal weight women and to analyse the effect of weight-reduction therapy on the determined thresholds. Patients and methods: 42 obese women without concomitant disease (age 30.5 ± 6.9y; BMI 33.6 ± 3.7 kg·m^-2) and 19 healthy normal weight women (age 27.6 ± 7.0y; BMI 21.2 ± 1.9 kg·m^-2) performed cycle ergometer incremental ramp exercise test up to exhaustion. The test was repeated in 19 obese women after 12.3 ± 4.2% weight loss. The lactate threshold (LT) and the ventilatory threshold (VT) were determined. Obese women had higher lactate (expressed as oxygen consumption) and ventilator threshold than normal weight women. The lactate threshold was higher than ventilatory one both in obese and normal weight women (1.11 ± 0.21 vs 0.88 ± 0.18 L·min^-1, p < 0.001; 0.94 ± 0.15 vs 0.79 ± 0.23 L·min^{- 1}, p < 0.01, respectively). After weight reduction therapy neither the lactate nor the ventilatory threshold changed significantly. The results concluded that; 1. The higher lactate threshold noted in obese women may be related to the increased fat acid usage in metabolism. 2. Both in obese and normal weight women lactate threshold appears at higher oxygen consumption than ventilatory threshold. 3. The obtained weight reduction, without weight normalisation was insufficient to cause significant changes of lactate and ventilatory thresholds in obese women.

Key points

• Results showed that adolescent young female gymnasts have an altered serum inflammatory markers and endothelial activation, compared to their less physically active peers.
• Physical activities improved immune system.
• Differences in these biochemical data kept significant after adjustment for body weight and height.

Key words: Obesity, anaerobic threshold, lactate threshold, ventilatory threshold     

The effect of posture on the ventilatory response to hypoxia

The ventilatory response to carbon dioxide is known to be uninfluenced by changes in posture. To obtain similar data on the ventilatory response to hypoxia we studied seven subjects in each of two postures, lying and sitting, at a constant PCO2 midway between end-tidal and mixed venous. Minute ventilation was higher in the seated position than supine (p < 0.01) at this isocapnic level, attributable mainly to an increase in tidal volume (p < 0.05). However, there were no statistically significant differences in the ventilatory response, the tidal volume response, or the frequency response to hypoxia between the two postures.     

Cardiorespiratory response to exercise in children after modified fontan operation

OBJECTIVE: Examination of exercise function of Fontan patients and comparison with healthy control subjects. DESIGN: Fourteen patients (6 males, 8 females; age: 5.7-17 years, mean 8.1 years) after Fontan repair in New York Heart Association (NYHA) class I with rest O(2)sat > 85% requiring no cardiovascular medications performed graded exercises on a treadmill 0.5-3.2 years postoperatively (mean 1.8 years). During the tests the heart and respiratory rate, blood pressure, oxygen uptake, carbon dioxide production, minute ventilation, tidal volume and O(2)sat were recorded. Spirometry was performed before and during exercise. RESULTS: The peak VO(2)max in Fontan patients was significantly reduced compared with controls (p = 0.0002). Other parameters: anaerobic threshold (p = 0.0001); pulsO(2) (p = 0.00005); peak minute ventilation (p = 0.0014); physiological dead space to tidal volume ratio at peak exercise (p = 0.0004); maximal work rate (p = 0.00008); exercise time (p = 0.00003) were significantly reduced in univentricular patients. The heart rate at peak exercise was lower in the patients (p = 0.0003) and O(2)sat dropped significantly (p = 0.003). CONCLUSION: The aerobic capacity, work and ventilatory parameters in Fontan patients are markedly reduced compared with controls. The anaerobic threshold was significantly lower. The decreased O(2)sat at peak exercise may suggest intrapulmonary shunting.     

The systemic inflammatory response to exercise in adults with cystic fibrosis.

Exercise is associated with release of inflammatory mediators in the circulation and there is evidence that the exercising muscles and tendons are sources of interleukin-6. Due to the catabolic effects of some cytokines, increased release in circulation might contribute to alterations in body composition in adults with cystic fibrosis. We hypothesised that exercise of moderate intensity would generate increased blood concentrations of some inflammatory mediators. We investigated the change in blood concentrations of interleukin-6, tumour necrosis factor alpha and their soluble receptors after a structured exercise (box stepping) of intensity similar to that encountered during activities of daily living in 12 adults with cystic fibrosis and mean (95% confidence interval) FEV1 55.6 (44.4, 66.8)% predicted, body mass index 23.0 (21.3, 24.6) kg/m2 and 12 healthy subjects. The increments post-exercise for all inflammatory mediators and lactate corrected for the work performed until voluntary exhaustion were greater for patients, while the total work was less for patients (all p<0.01). Daytime variability of the inflammatory mediators was assessed in eight patients and was less than the change due to exercise. We report greater increments in circulating concentrations of some cytokines with moderate exercise in adults with cystic fibrosis compared to healthy subjects.     

Effect of exercise on the nasal transmucosal potential difference in patients with cystic fibrosis and normal subjects.

BACKGROUND--Normal subjects have a negative nasal transmucosal potential difference (TPD) at rest which becomes more negative with exercise. Patients with cystic fibrosis have a more negative resting nasal TPD than controls. The present study was designed to determine the effects of exercise on the TPD of patients with cystic fibrosis. METHODS--Seven subjects with cystic fibrosis and seven control subjects had their usual TPD measured at rest, and during and after a 12 minute period on an exercise bicycle designed to produce a pulse rate of 80% of their maximum predicted value. RESULTS--The normal subjects developed a more negative nasal TPD during exercise which returned towards normal at the completion of the rest period. The patients with cystic fibrosis had higher resting values which became less negative during exercise. At the end of the exercise period there was no difference between the two groups. At the end of the recovery period the results for the patients with cystic fibrosis had returned to their resting values. CONCLUSIONS--Exercise reduces the abnormally high resting values for nasal TPD in patients with cystic fibrosis. Elucidation of the mechanism for this change may help to produce functional improvement for patients with this disease.     

Cardiorespiratory and Metabolic Responses to Loaded Half Squat Exercise Executed at an Intensity Corresponding to the Lactate Threshold

This study was designed to identify the blood lactate threshold (LT2) for the half squat (HS) and to examine cardiorespiratory and metabolic variables during a HS test performed at a work intensity corresponding to the LT2. Twenty-four healthy men completed 3 test sessions. In the first, their one-repetition maximum (1RM) was determined for the HS. In the second session, a resistance HS incremental-load test was performed to determine LT2. Finally, in the third session, subjects performed a constant-load HS exercise at the load corresponding to the LT2 (21 sets of 15 repetitions with 1 min of rest between sets). In this last test, blood samples were collected for lactate determination before the test and 30 s after the end of set (S) 3, S6, S9, S12, S15, S18 and S21. During the test, heart rate (HR) was telemetrically monitored and oxygen consumption (VO₂), carbon dioxide production (VCO₂), minute ventilation (VE), respiratory exchange ratio (RER), ventilatory equivalent for O₂ (VE·VO₂^-1) and ventilatory equivalent for CO₂ (VE·VCO₂^-1) were monitored using a breath-by-breath respiratory gas analyzer. The mean LT2 for the participants was 24.8 ± 4.8% 1RM. Blood lactate concentrations showed no significant differences between sets 3 and 21 of exercise (p = 1.000). HR failed to vary between S6 and S21 (p > 1.000). The respiratory variables VO₂, VCO₂, and VE·VCO₂^-1 stabilized from S3 to the end of the constant-load HS test (p = 0.471, p = 0.136, p = 1.000), while VE and VE·VO₂^-1 stabilized from S6 to S21. RER did not vary significantly across exercise sets (p = 0.103). The LT2 was readily identified in the incremental HS test. Cardiorespiratory and metabolic variables remained stable during this resistance exercise conducted at an exercise intensity corresponding to the LT2. These responses need to be confirmed for other resistance exercises and adaptations in these responses after a training program also need to be addressed.

Key points

• It can be identified lactate threshold at half-squat.
• Exercise intensity is predominantly aerobic.
• The duration of the half-squat can be maintained over time, ~30 min of discontinuous exercise (21 sets, 15 repetitions, 1 min rest).
• Lactate threshold intensity may be suitable for older adults, sedentary individuals, patients or subjects with a lower functional capacity and even for resistance sports athletes.

Key words: Aerobic fitness/VO_2max, anaerobic threshold, exercise physiology, strength training     

Effects of subanaesthetic sevoflurane on ventilation. 1: Response to acute and sustained hypercapnia in humans

We have determined the influence of 0.1 minimum alveolar concentration (MAC) of sevoflurane on ventilation, the acute ventilatory response to a step change in end-tidal carbon dioxide and the ventilatory response to sustained hypercapnia in 10 healthy adult volunteers. Subjects undertook a preliminary 10-min period of breathing air without sevoflurane to determine their normal ventilation and natural end-tidal PCO2. This 10-min period was repeated while breathing 0.1 MAC of sevoflurane. Subjects then undertook two procedures: end-tidal PO2 was maintained at 13.3 kPa and end-tidal PCO2 at 1.3 kPa above the subject's normal value for 30 min of data collection, first with and then without 0.1 MAC of sevoflurane. A dynamic end-tidal forcing system was used to generate these gas profiles. Sevoflurane did not significantly change ventilation: 10.1 (SEM 1.0) litre min-1 without sevoflurane, 9.6 (0.9) litre min-1 with sevoflurane. The response to acute hypercapnia was also unchanged: mean carbon dioxide response slopes were 20.2 (2.7) litre min-1 kPa-1 without sevoflurane and 18.8 (2.7) litre min-1 kPa-1 with sevoflurane. Sustained hypercapnia caused a significant gradual increase in ventilation and tidal volume over time and significant gradual reduction in inspiratory and expiratory times. Sevoflurane did not affect these trends during sustained hypercapnia. These results suggest that 0.1 MAC of sevoflurane does not significantly affect the acute ventilatory response to hypercapnia and does not modify the progressive changes in ventilation and pattern of breathing that occur with sustained hypercapnia.      

Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide

BACKGROUND—Nitricoxide (NO) is released by activated macrophages, neutrophils, andstimulated bronchial epithelial cells. Exhaled NO has been shown to beincreased in patients with asthma and has been put forward as a markerof airways inflammation. However, we have found that exhaled NO is notraised in patients with cystic fibrosis, even during infectivepulmonary exacerbation. One reason for this may be that excess airwaysecretions may prevent diffusion of gaseous NO into the airway lumen.We hypothesised that exhaled NO may not reflect total NO production inchronically suppurative airways and investigated nitrite as anothermarker of NO production.
METHODS—Breathcondensate nitrite concentration and exhaled NO levels were measured in21 clinically stable patients with cystic fibrosis of mean age 26 yearsand mean FEV₁ 57% and 12 healthy normal volunteers of meanage 31 years. Breath condensate was collected with a validated methodwhich excluded saliva and nasal air contamination and nitrite levelswere measured using the Griess reaction. Exhaled NO was measured usinga sensitive chemiluminescence analyser (LR2000) at an exhalation rateof 250 ml/s. Fourteen patients with cystic fibrosis had circulatingplasma leucocyte levels and differential analysis performed on the dayof breath collection.
RESULTS—Nitrite levelswere significantly higher in patients with cystic fibrosis than innormal subjects (median 1.93 µM compared with 0.33 µM). Thiscorrelated positively with circulating plasma leucocytes andneutrophils (r = 0.6). In contrast, exhaledNO values were not significantly different from the normal range (median 3.8 ppb vs 4.4 ppb). There was no correlation between breathcondensate nitrite and lung function and between breath condensatenitrite and exhaled NO.
CONCLUSIONS—Nitritelevels in breath condensate were raised in stable patients with cysticfibrosis in contrast to exhaled NO. This suggests that nitrite levelsmay be a more useful measure of NO production and possibly airwaysinflammation in suppurative airways and that exhaled NO may not reflecttotal NO production.

     

Pericardial fluid gas analysis in hemorrhagic pericardial tamponade.

Nine patients with hemorrhagic pericardial tamponade were studied to determine the localizing value of gas analysis of pericardial fluid in therapeutic pericardiocentesis. The aspirate and the central venous blood was analyzed simultaneously for partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), and hematocrit at the time of pericardiocentesis. In all 9 patients the difference in hematocrit between the pericardial fluid and the central venous blood was not significant. The PCO2 of pericardial fluid was significantly higher than that of central venous blood (p less than 0.025). The PO2 of pericardial fluid was consistently and significantly lower than that of central venous blood (p less than 0.005). We conclude that in patients with hemorrhagic pericardial tamponade, the simultaneous measurement of PO2 and PCO2 of central venous blood and pericardial fluid is a useful rapid bedside method to confirm the site of aspiration during pericardiocentesis. The PO2 determination is statistically the best discriminator between the two fluids in this setting.     

Role of heat shock proteins in the pathogenesis of cystic fibrosis arthritis

BACKGROUND: Arthritis is a well recognised complication of cystic fibrosis. The cause of this arthritis is not yet clear but it is likely to be an immunological reaction to one of the many bacterial antigens to which the lungs are exposed. One such group, the heat shock proteins, (hsp), was investigated. These are immunodominant antigens of a wide variety of infectious microorganisms and have varying amino acid chain sequences, some of which are similar to those found in human tissues. METHODS: Antibodies to human hsp 27 and hsp 90 in the serum of patients with cystic fibrosis, with and without arthritis, and in normal age and sex matched healthy controls were measured. The severity of the cystic fibrosis was assessed by lung function tests and chest radiographs. The nature of the organisms colonising the lungs was determined by bacteriological examination of sputum. RESULTS: Higher mean titres of serum IgG anti-human hsp 27 and hsp 90 antibodies were found in 50 patients with cystic fibrosis than in healthy controls (hsp 27, 0.25 (95% CI 0.19 to 0.33) versus 0.05 (95% CI 0.04 to 0.07); hsp 90, 0.27 (95% CI 0.22 to 0.32) versus 0.11 (95% CI 0.08 to 0.14)). These antibodies were higher in patients in whom the lungs were colonised with Pseudomonas aeruginosa than in those without infection (hsp 27, 0.41 (95% CI 0.17 to 0.63) versus 0.18 (95% CI 0.10 to 0.27); hsp 90, 0.37 (95% CI 0.18 to 0.57) versus 0.22 (95% CI 0.16 to 0.29)). The eight patients with cystic fibrosis with arthritis had higher anti- hsp 27 antibodies (0.48 (95% CI 0.13 to 0.92)) than the 42 patients without arthritis (0.22 (95% CI 0.17 to 0.30)). CONCLUSIONS: These findings suggest that the arthritis associated with cystic fibrosis, despite being seronegative for rheumatoid factor, was associated with more severe lung disease and with a greater inflammatory response to heat shock proteins.


     

Gas exchange as monitored in mixed venous and arterial blood during experimental cardiopulmonary resuscitation

Nineteen anaesthetized piglets were investigated. After catheterization and a stabilization period, ventricular fibrillation was induced with a transthoracic DC shock, after which a 10-min period of cardiopulmonary resuscitation (CPR) took place. CPR included manual chest compression and mechanical ventilation with pure oxygen. After 1 min of CPR, an infusion of alkaline buffer was begun and completed within 5 min. A total of 50 mmol of either sodium bicarbonate (n = 6) or tris buffer mixture (n = 7) were given. These two groups were compared with a third control group (n = 6) receiving the same volume of normal saline. After 8 min of CPR all animals were given 0.5 mg adrenaline i.v., and after 10 min DC shocks were used to revert the heart back to normal sinus rhythm. Our results demonstrate that blood flow and not ventilation is the limiting factor for the efficient disposal of CO2 during CPR. This also applied when the demand for CO2 transport was increased by administration of sodium bicarbonate. The respiratory exchange ratio increased 1.9-fold, indicating that the transport of carbon dioxide was less affected than that of oxygen. The estimated alveolo-arterial oxygen tension difference, shunt, and overall ventilation/perfusion ratio increased, creating an inverse hyperbolic relationship between arterial PCO2 and PO2. The difference between mixed venous and arterial PCO2 correlated well to the mixed venous PCO2, implying more efficient pulmonary elimination of PCO2 when the mixed venous PCO2 was high. Pulmonary gas exchange during CPR appears to be independent of alkaline buffer therapy in the form of sodium bicarbonate or tris buffer mixture.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of a combined oxygen and carbon dioxide transcutaneous electrode in the estimation of gas exchange during exercise.

BACKGROUND--Accurate and reliable measurement of gas exchange during exercise has traditionally involved arterial cannulation. Non-invasive devices to estimate arterial oxygen (O2) and carbon dioxide (CO2) tensions are now available. A method has been devised and evaluated for measuring gas exchange during exercise with a combined transcutaneous O2 and CO2 electrode. METHODS--Symptom limited exercise tests were carried out in 24 patients reporting effort intolerance and breathlessness. Exercise testing was performed by bicycle ergometry with a specifically designed protocol involving gradual two minute workload increments. Arterial O2 and CO2 tensions were measured at rest and during exercise by direct blood sampling from an indwelling arterial cannula and a combined transcutaneous electrode heated to 45 degrees C. The transcutaneous system was calibrated against values obtained by direct arterial sampling before each test. RESULTS--In all tests the trend of gas exchange measured by the transcutaneous system was true to the trend measured from direct arterial sampling. In the 140 measurements the mean difference between the O2 tensions estimated by direct sampling and the transcutaneous method was 0.08 kPa (0.62 mm Hg, limits of agreement 4.42 and -3.38 mm Hg). The mean difference between the methods for CO2 was 0.02 kPa (0.22 mm Hg, limits of agreement 2.20 and -1.70 mm Hg). There was no morbidity associated with the use of the transcutaneous electrode heated to 45 degrees C. CONCLUSIONS--A combined transcutaneous O2 and CO2 electrode heated to 45 degrees C can be used to provide a reliable estimate of gas exchange during gradual incremental exercise in adults.     

Is Blood Lactate Removal During Water Immersed Cycling Faster than During Cycling on Land?

The aim of the present study was to compare lactate removal during active recovery performed during cycling in water immersion (CW) and during cycling on land (CL), after a similar exercise bout in male adults. Eleven healthy and physically active men, aged between 20 and 26 years old participated in the experiment. Before the experimental tests, the ventilatory threshold of the subjects was determined. Each subject completed the experimental tests twice, with one week separating the two periods of experiment. The subjects exercised on the treadmill during 6 min at a speed 10% above the speed corresponding to their ventilatory threshold. Subsequently, the subjects recovered from the exercise bout either on a stationary bike (CL) or on a aquatic-specific bike (CW). On the subsequent week the subjects performed the same protocol but with a different recovery condition. Recovery condition assignment for the first test was counterbalanced (six subjects started with one condition and five with the other). Capillary blood samples were collected after each test and during the recovery period (at 3, 6, 9 and 15 minutes) and blood lactate was measured. The blood lactate values during CW were lower than during CL and significant differences were observed at the 6^th minute (p ≤ 0.05) and at the 15^th minute of recovery (p ≤ 0.05). Therefore, we may conclude that active recovery using cycling in water immersion may be more efficient than cycling on land for blood lactate removal.

Key points

• Previous studies have found positive effects of half liquid environment on blood lactate removal.
• However, few studies have compared lactate removal in half liquid and in dry land conditions with the use of stationary bikes.
• We have compared the lactate removal during active recovery on half-liquid cycling and active recovery on dry land cycling after a similar exercise bout in male adults.
• The blood lactate values during the recovery were lower after half-liquid cycling when compared with dry land cycling and significant differences were observed at the 6^th minute and at the 15^th minute of recovery.
• We may conclude that active recovery using half-liquid cycling may be more efficient than dry land cycling for blood lactate removal.

Key words: Active recovery, water exercise, land exercise