Hypoxia during upper gastrointestinal endoscopy with and without sedation and the effect of pre-oxygenation on oxygen saturation

In Study A, the incidence of arterial oxygen desaturation was studied using pulse oximetry (SaO2) in 100 sedated and 100 nonsedated patients breathing room air who underwent diagnostic upper gastrointestinal endoscopy. Hypoxia (SaO2 92% or less of at least 15 s duration) occurred in 17% and 6% of sedated patients and nonsedated patients, respectively (p < 0.03). Mild desaturation (SaO2 94% or less and less than 15 s duration) occurred in 47% of sedated patients compared with 12% of nonsedated patients (p < 0.001). In Study B, the effects of supplementary oxygen therapy and the effects of different pre-oxygenation times on arterial oxygen saturation (SaO2) in sedated patients were studied using pulse oximetry. One hundred and twenty patients who underwent diagnostic upper gastrointestinal endoscopy with intravenous sedation were studied. Patients were randomly allocated to one of four groups: Group A (n = 30) received no supplementary oxygen while Groups B-D received supplementary oxygen at 4 1 x min(-1) via nasal cannulae. The pre-oxygenation time in Group B (n = 30) was zero minutes, Group C (n = 30) was 2 min and Group D (n = 30) was 5 min before sedation and introduction of the endoscope. Hypoxia occurred in seven of the 30 patients in Group A and none in groups B, C and D (p < 0.001). We conclude that desaturation and hypoxia is common in patients undergoing upper gastrointestinal endoscopy with and without sedation. Sedation significantly increases the incidence of desaturation and hypoxia. Supplementary nasal oxygen at 4 1 x min(-1) in sedated patients abolishes desaturation and hypoxia. Pre-oxygenation confers no additional benefit.     

The 12-min walk test as an assessment criterion for lung transplantation in subjects with cystic fibrosis.

Timing for the evaluation and listing of patients with cystic fibrosis who are candidates for lung transplantation is still uncertain. Our study goal was to determine the value of the 12-min walk test as a simple and easy-to-use adjunctive assessment tool for pre-transplant evaluation. A total of 34 cystic fibrosis patients (17 male, mean age 22 years) with end-stage lung disease were evaluated in this retrospective analysis. The 12-min walk test was carried out according to an established protocol. Before walking, body plethysmography was performed and a capillary sample was taken for blood gas analysis. Walking distance and SaO(2) via continuous pulse oximetry were recorded online. There was a strong correlation between survival time and walking distance (r=0.7, P=0.003). No other single parameter, such as FEV(1), SaO(2,) pCO(2) or BMI, showed a statistically significant correlation with survival time. Subjects who walked < or =700 m had a lower cumulative survival (P=0.02). There was a statistically significant positive correlation between walking distance and SaO(2) at rest and after 12 min of walking (r=0.5, P=0.001; and r=0.5, P=0.04, respectively). There was no correlation between walking distance and pCO(2) at rest, BMI, FEV(1), or degree of change in SaO(2) during the walk test. This study demonstrates that in CF patients with end-stage lung disease, walking distance during a 12-min walk test is more informative with respect to survival than single parameters such as SaO(2,) pCO(2), FEV(1) or BMI.     

Effects of breathing supplemental oxygen before progressive exercise in patients with chronic obstructive lung disease.

A study was carried out to determine whether supplemental oxygen before exercise would improve maximum exercise performance and relieve exertional dyspnoea in 20 patients with chronic obstructive lung disease (mean FEV1 0.79 l; forced vital capacity 2.30 l). Patients performed two progressive treadmill exercise tests to a symptom limited maximum, with at least 30 minutes rest between tests. They received compressed air or supplemental oxygen from nasal prongs for 10 minutes before exercise in a double blind randomised trial with a crossover design. Heart rate and breathlessness score on a visual analogue scale were compared between tests at 75% of the maximum distance walked in the compressed air test. The mean arterial oxygen saturation (SaO2) after oxygen (93%) was significantly higher than after compressed air (91%). There was no significant change, however, in maximum distance walked or maximum heart rate, or in the breathlessness score or heart rate at 75% of maximum distance walked. The study had a power of 93% for detecting an increase of 50 metres in maximum distance walked. There was an order effect, with better performance on the second test; but the magnitude of the difference was small. It is concluded that administration of supplemental oxygen sufficient to raise SaO2 above 90% for 10 minutes before exercise is unlikely to improve maximum exercise performance or breathlessness on exertion in patients with chronic obstructive lung disease.     

Portable liquid oxygen and exercise ability in severe respiratory disability.

BACKGROUND: The development of portable liquid oxygen systems, capable of delivering high flow rate oxygen for long periods, justifies reassessment of the value of supplemental oxygen to aid exercise tolerance in patients with chronic respiratory insufficiency. The type of exercise test and the low oxygen flow rates previously used may account for the variable and often poor responses to supplemental oxygen reported in earlier studies. METHODS: The walking tolerance of 30 patients with severe respiratory disability was measured while they were breathing air and increasing doses of supplemental oxygen (2, 4, 6 1/min) by using both the standard six minute walking test and an endurance walking test. To assess the initial learning effect and repeatability of the walking tests, three six minute walks and three endurance walks were performed on day 1 and a single walk of each type on days 2, 3, and 14. In addition, oxygen dosing studies were performed on days 2 and 3 after the initial baseline walking tests. Each dosing study comprised four endurance walking tests or four six minute walking tests with patients breathing either air at a flow rate of 4 1/min from a portable cylinder or supplemental oxygen at a flow rate of 2, 4 or 6 1/min from a portable liquid oxygen supply. The order of the tests was randomised. Walking distance with each flow rate of oxygen was compared with walking distance with patients carrying cylinder air and for the initial unburdened walks. Breathlessness was assessed by visual analogue scoring on completion of each walk. RESULTS: Exercise ability and breathlessness were significantly improved with supplemental oxygen and this benefit outweighed the reduction in performance resulting from carrying the portable device. Supplemental oxygen at flow rates of 2, 4, and 6 1/min increased mean endurance walking distances by 37.9%, 67.7% and 85.0% and six minute walking distances by 19.2%, 34.5%, and 36.3% by comparison with distances when the patient was carrying air with a flow rate of 4 1/min. The additional work of carrying the portable gas supply reduced endurance walking distance by 22.2% and six minute walking distance by 14.1% by comparison with a baseline unburdened walk. Comparison of supplemental oxygen at 2, 4, and 6 1/min with the baseline unburdened performance showed increased endurance walking distances of 7.3%, 30.4%, and 43.9% and six minute walking distances of 2.3%, 15.5%, and 17.0%. Walking distance was increased by more than 50% by comparison with an unburdened walk in seven patients with the endurance walking test but in only three patients with the six minute walking test. The benefit was similar in patients with obstructive and with interstitial lung disease. Individual responses were variable and only desaturation during the baseline walk in patients with obstructive lung disease had any predictive value for benefit with oxygen. CONCLUSION: As there was no clear relation between response to oxygen therapy and the patients' characteristics, assessment for supplemental oxygen therapy will depend on exercise testing. It is suggested that portable oxygen should be considered only if a patient shows a 50% improvement in exercise ability with high flow rate oxygen (4-6 1/min) by comparison with an unburdened walk.     

Effect of simulated commercial flight on oxygenation in patients with interstitial lung disease and chronic obstructive pulmonary disease

BACKGROUND: Commercial aircraft cabins provide a hostile environment for patients with underlying respiratory disease. Although there are algorithms and guidelines for predicting in-flight hypoxaemia, these relate to chronic obstructive pulmonary disease (COPD) and data for interstitial lung disease (ILD) are lacking. The purpose of this study was to evaluate the effect of simulated cabin altitude on subjects with ILD at rest and during a limited walking task. METHODS: Fifteen subjects with ILD and 10 subjects with COPD were recruited. All subjects had resting arterial oxygen pressure (PaO2) of >9.3 kPa. Subjects breathed a hypoxic gas mixture containing 15% oxygen with balance nitrogen for 20 minutes at rest followed by a 50 metre walking task. Pulse oximetry (SpO2) was monitored continuously with testing terminated if levels fell below 80%. Arterial blood gas tensions were taken on room air at rest and after the resting and exercise phases of breathing the gas mixture. RESULTS: In both groups there was a statistically significant decrease in arterial oxygen saturation (SaO2) and PaO2 from room air to 15% oxygen at rest and from 15% oxygen at rest to the completion of the walking task. The ILD group differed significantly from the COPD group in resting 15% oxygen SaO2, PaO2, and room air pH. Means for both groups fell below recommended levels at both resting and when walking on 15% oxygen. CONCLUSION: Even in the presence of acceptable arterial blood gas tensions at sea level, subjects with both ILD and COPD fall below recommended levels of oxygenation when cabin altitude is simulated. This is exacerbated by minimal exercise. Resting sea level arterial blood gas tensions are similarly poor in both COPD and ILD for predicting the response to simulated cabin altitude.     

Ventilation and gas exchange during sleep in patients with interstitial lung disease.

Ventilation and gas exchange during overnight sleep was studied in a group of seven patients with severe interstitial lung disease (mean vital capacity 50%, mean diffusing capacity 46% predicted), to see whether clinically significant oxygen desaturation occurred. Patients with a history of loud snoring or clinically significant airflow obstruction were excluded. Sleep was fragmented in these patients, but all achieved rapid eye movement (REM) sleep. All patients showed episodes of oxygen desaturation during sleep--mean (SEM) awake arterial oxygen saturation (SaO2) was 92.9% (0.3%) compared with a mean minimum SaO2 during sleep of 83.2% (2.1%) (p less than 0.01). These episodes were, however, transient, and mean SaO2 showed only a slight fall between wakefulness and sleep (non-REM 91.5%, REM 90.4%; NS). Furthermore, SaO2 during non-REM sleep correlated well (p less than 0.001) with SaO2 during wakefulness. Respiratory frequency showed a significant fall between wakefulness and sleep--21.1 (1.8) versus 17.3 (1.5) breaths per minute (p less than 0.02). Our data suggest that nocturnal oxygen treatment need not be considered in patients with interstitial lung disease unless the level of oxygenation while they are awake indicates the need for such treatment.     

Supplemental oxygen during pulmonary rehabilitation in patients with COPD with exercise hypoxaemia

BACKGROUND: Supplemental oxygen in patients with chronic obstructive pulmonary disease (COPD) and exercise hypoxaemia improves exercise capacity and dyspnoea. However, the benefit of oxygen during pulmonary rehabilitation in these patients is still unknown. METHODS: Twenty five patients with stable COPD (mean (SD) forced expiratory volume in one second (FEV(1)) 0.76 (0.29) l and 30.0 (9.89)% predicted, arterial oxygen tension (PaO(2)) 8.46 (1.22) kPa, arterial carbon dioxide tension (PaCO(2)) 6.32 (1.01) kPa) and significant arterial desaturation on exercise (82.0 (10.4)%) were entered onto a pulmonary rehabilitation programme. Patients were randomised to train whilst breathing oxygen (OT) (n = 13) or air (AT) (n = 12), both at 4 l/min. Assessments included exercise tolerance and associated dyspnoea using the shuttle walk test (SWT) and Borg dyspnoea score, health status, mood state, and performance during daily activities. RESULTS: The OT group showed a significant reduction in dyspnoea after rehabilitation compared with the AT group (Borg mean difference -1.46 (95% CI -2.72 to -0.19)) but there were no differences in other outcome measures: SWT difference -23.6 m (95% CI -70.7 to 23.5), Chronic Respiratory Disease Questionnaire 3.67 (95% CI -7.70 to 15.1), Hospital Anxiety and Depression Scale 1. 73 (95% CI -2.32 to 5.78), and London Chest Activity of Daily Living Scale -2.18 (95% CI -7.15 to 2.79). At baseline oxygen significantly improved SWT (mean difference 27.3 m (95% CI 14.7 to 39.8) and dyspnoea (-0.68 (95% CI -1.05 to -0.31)) compared with placebo air. CONCLUSIONS: This study suggests that supplemental oxygen during training does little to enhance exercise tolerance although there is a small benefit in terms of dyspnoea. Patients with severe disabling dyspnoea may find symptomatic relief with supplemental oxygen.     

Prediction of oxygenation during sleep in patients with chronic obstructive lung disease.

The accuracy of a prediction equation for assessing the lowest arterial oxygen saturation (SaO2) during sleep was determined in 24 consecutive patients with chronic obstructive lung disease referred for assessment for home oxygen therapy. Subjects had a mean (SD) FEV1 of 0.81 (0.31) litre and an FEV1/FVC of 37% (12%). There was reasonable agreement between predicted and measured values (mean difference [predicted-measured] = -2.5%) but the prediction was not precise as the 95% confidence interval for the difference was +8% to -13%. The duration of arterial oxygen desaturation, defined as the percentage of total sleep time spent below a given SaO2, was not predicted accurately. It is concluded that nocturnal arterial oxygen desaturation in individual patients with chronic obstructive lung disease cannot be predicted from "awake" measurements with sufficient accuracy to be clinically useful.     

Nocturnal hypoxaemia and quality of sleep in patients with chronic obstructive lung disease.

Fifty patients with chronic obstructive lung disease were questioned about their sleep quality and their responses were compared with those of 40 similarly aged patients without symptomatic lung disease. Patients with chronic obstructive lung disease reported more difficulty in getting to sleep and staying asleep and more daytime sleepiness than the control group. More than twice as many patients (28%) as controls (10%) reported regular use of hypnotics. In a subgroup of 16 patients with chronic obstructive lung disease (mean FEV1 0.88 (SD 0.44) sleep, breathing, and oxygenation were measured to examine the relationship between night time hypoxaemia and sleep quality. Sleep architecture was disturbed in most patients, arousals occurring from three to 46 times an hour (mean 15 (SD 14)/h). Arterial hypoxaemia during sleep was common and frequently severe. The mean (SD) arterial oxygen saturation (SaO2) at the onset of sleep was 91% (7%). Nine patients spent at least 40% of cumulative sleeping time at an SaO2 of less than 90% and six of these patients spent 90% of sleeping time below this level. Only four of 15 patients did not develop arterial desaturation during sleep. The mean minimum SaO2 during episodes of desaturation was less in rapid eye movement (REM) sleep (72% (17%)) than in non-REM sleep (78% (10%), p less than 0.05). The predominant breathing abnormality associated with desaturation was hypoventilation; only one patient had obstructive sleep apnoea. Arousals were related to oxygenation during sleep such that the poorer a patient's arterial oxygenation throughout the night the more disturbed his sleep (arousals/h v SaO2 at or below which 40% of the total sleep time was spent: r = 0.71, p less than 0.01). Hypoxaemia during sleep was related to waking values of SaO2 and PaCO2 but not to other daytime measures of lung function.     

Short term effect of oxygen on renal haemodynamics in patients with hypoxaemic chronic obstructive airways disease.

BACKGROUND: Oxygen therapy is effective in the prevention and treatment of oedematous exacerbations of cor pulmonale. As renal blood flow is reduced in cor pulmonale a study was designed to investigate whether one of the beneficial effects of oxygen was to increase renal blood flow. The effect of oxygen therapy on renal haemodynamics measured noninvasively was examined in patients with chronic obstructive airways disease and previous episodes of oedema. METHODS: Renal blood flow waveforms were recorded in a single vessel by colour flow Doppler ultrasound in nine hypoxaemic patients (PaO2) (arterial oxygen tension < 8 kPa while they were breathing air) with chronic obstructive airways disease and previous oedema and eight age matched normoxaemic volunteers (arterial oxygen saturation (SaO2) 97% or more when breathing air) while they were breathing air and oxygen. SaO2 and transcutaneous PaO2 (TcPO2) and PaCO2 (TcPCO2) were monitored. Five renal velocity profile recordings were made from the same segmental vessel with the patient breathing room air for one hour followed by oxygen titrated to achieve an oxygen saturation of 95% or more without a rise in TcPCO2 for 15 minutes. Control subjects breathed 35% oxygen. RESULTS: No significant change in the pulsatility index (a measure of distal vascular resistance) or mean height of the waveform (Tamx, a measure of renal blood flow) occurred in the control subjects while they were breathing air or oxygen. The pulsatility index of the patients with chronic obstructive airways disease was significantly greater than that in the control subjects breathing air (1.44 (SD 0.28) v 1.03 (0.14). Breathing oxygen was associated with an increase in TcPO2 in the patients (from 6.9 (1.9) to 11.5 (0.7) kPa), a fall in pulsatility index (from 1.44 (0.28) to 1.26 (0.14) and an increase in Tamx (from 0.187 (0.055) to 0.234 (0.087) m/s). CONCLUSIONS: The results suggest that renal vascular resistance is increased in patients with chronic obstructive airways disease and hypoxaemia and that short term oxygen therapy reduces renal vascular resistance and increases blood flow. Some of the benefits of oxygen therapy in cor pulmonale may be due to improvements in renal haemodynamics.     

Arterial desaturation in HIV positive patients undergoing sputum induction.

Arterial oxygen saturation (SaO2) was monitored continuously during and immediately after sputum induction in 41 HIV positive patients with respiratory symptoms and in 20 symptomless medical and nursing staff, who acted as control subjects. Arterial oxygen desaturation (defined as SaO2 less than or equal to 92%) occurred during sputum induction and persisted for up to 20 minutes after the end of the procedure in 11 of the 20 patients with Pneumocystis carinii pneumonia and in nine of the 21 patients with other respiratory diagnoses. None of the control subjects showed oxygen desaturation. Neither the severity of chest radiographic abnormalities, the alveolar-arterial oxygen gradient (both measured before sputum induction), nor baseline SaO2 prospectively identified the patients who developed oxygen desaturation. Two patients, one with pneumocystis pneumonia, developed dyspnoea and had a fall in arterial oxygen saturation to 84% within 10 minutes of starting sputum induction. The procedure was abandoned in both patients and in two further patients, who developed severe nausea and reaching but no oxygen desaturation. Sputum induction in HIV positive patients with respiratory symptoms may induce a fall in SaO2 that persists after this procedure. This may be important if other procedures are performed soon after sputum induction.     

Clinical assessment of oxygen conserving devices in chronic bronchitis and emphysema.

We have studied the efficacy of three devices designed to conserve oxygen delivered to patients with hypoxic chronic bronchitis and emphysema. Devices A and B are valve systems, which deliver oxygen only during inspiration. Device C is a modified nasal prongs system incorporating a "moustache reservoir" (Oxymizer, Chad Therapeutics Inc, Woodland Hills, California), which is claimed to produce a higher arterial oxygen saturation (SaO2) from a given flow of oxygen than does continuous delivery through nasal prongs. Devices A and B were found to give the same oxygen saturation as continuous flow oxygen, but only device B reduced the flow of oxygen significantly (p less than 0.01). The flow characteristics of device A were likely to be the cause of this failure to conserve oxygen. Device C produced a higher mean rise in SaO2 than did standard nasal prongs at all oxygen flow rates, and was able to achieve the same rise in SaO2 as standard nasal prongs with a small (25-33%) saving in oxygen delivery. There was, however, considerable variation between patients in the oxygen saving efficiency of device C, with little or no oxygen saving in seven of the 12 patients studied.     

Effect of inspiratory pressure support on exercise tolerance and breathlessness in patients with severe stable chronic obstructive pulmonary disease.

BACKGROUND--In patients with chronic obstructive pulmonary disease exercise tolerance is commonly limited by breathlessness. These patients have an increased ventilatory load at rest which is exacerbated during exercise. The purpose of this study was to investigate the effect of supporting ventilation by non-invasive inspiratory pressure support (IPS) during submaximal treadmill exercise in such patients to see if they would experience less breathlessness and improve their exercise capacity. METHODS--Eight men with disabling breathlessness due to chronic obstructive pulmonary disease (COPD) (mean (SD) FEV1 0.73 (0.2) 1) were studied. Patients walked on a treadmill until their sensation of breathlessness, scored at one minute intervals, reached level 5 ("severe") on the 10-point Borg scale. Studies were performed with IPS (mean airway pressure 12-15 cm H2O), continuous positive airway pressure (CPAP 6 cm H2O), and with oxygen (2 l/min via a mask) in random order on three separate days. Each of these walks was compared with a control walk using a sham circuit (breathing air via an oxygen mask at 2 l/min from an unlabelled cylinder), and with a baseline walk in which patients walked freely on the treadmill. On cessation of exercise, distance achieved and a leg fatigue score were recorded. RESULTS--No patients stopped due to leg fatigue, all stopping only when their sensation of breathlessness had reached level 5 on the Borg scale. IPS improved median walking distance by 62% compared with the control walk (sham circuit). There was no change in walking distance with either CPAP or oxygen at 2 l/min. There was no difference between the control and the baseline walks. CONCLUSIONS--Inspiratory pressure support can reduce breathlessness and increase exercise tolerance to submaximal treadmill exercise in patients with COPD. This could have implications for the rehabilitation of these severely disabled patients.     

Oxygen desaturation during sleep and exercise in patients with interstitial lung disease.

The relations between mean and maximum fall in arterial oxygen saturation (SaO2) during sleep, hypoxaemia during moderate and maximum exercise, and lung mechanics were studied in 16 patients with interstitial lung disease. Mean and minimum SaO2 during sleep were significantly related to each other and to daytime oxygenation but not to lung mechanics. Although the maximum fall in SaO2 during sleep was similar to the fall during maximum exercise (a level seldom achieved during normal daily activities), profound hypoxaemic episodes during sleep were rare and brief and therefore contributed little to the mean SaO2. The fall in mean SaO2 during sleep was not significant and was considerably less than during moderate exercise (average 0.5 v an estimated 4.5%, p less than 0.05). It is therefore concluded that in patients with interstitial lung disease oxygen desaturation during sleep is mild and less severe than hypoxaemia during exercise.     

Continuous monitoring of jugular venous oxygen saturation in head-injured patients.

The continuous measurement of jugular venous oxygen saturation (SjvO2) with a fiberoptic catheter is evaluated as a method of detecting cerebral ischemia after head injury. Forty-five patients admitted to the hospital in coma after severe head injury had continuous and simultaneous monitoring of SjvO2, intracranial pressure, arterial oxygen saturation, and end-tidal CO2. Cerebral blood flow, cerebral metabolic rates of oxygen and lactate, arterial and jugular venous blood gas levels, and hemoglobin concentration were measured every 8 hours for 1 to 11 days. Whenever SjvO2 dropped to less than 50%, a standardized protocol was followed to confirm the validity of the desaturation and to establish its cause. Correlation of SjvO2 values obtained by catheter and with direct measurement of O2 saturation by a co-oximeter on venous blood withdrawn through the catheter was excellent after in vivo calibration when there was adequate light intensity at the catheter tip (176 measurements: r = 0.87, p less than 0.01). A total of 60 episodes of jugular venous oxygen desaturation occurred in 45 patients. In 20 patients the desaturation value was confirmed by the co-oximeter. There were 33 episodes of desaturation in these 20 patients, due to the following causes: intracranial hypertension in 12 episodes, hypocarbia in 10, arterial hypoxia in six, combinations of the above in three, systemic hypotension in one, and cerebral vasospasm in one. The incidence of jugular venous oxygen desaturations found in this study suggests that continuous monitoring of SjvO2 may be of clinical value in patients with head injury.     

Comparison of the efficacy of a demand oxygen delivery system with continuous low flow oxygen in subjects with stable COPD and severe oxygen desaturation on walking.

BACKGROUND: Provision of ambulatory oxygen using an intermittent pulsed flow regulated by a demand oxygen delivery system (DODS) greatly increases the limited supply time of standard portable gaseous cylinders. The efficacy of such a system has not previously been studied during submaximal exercise in subjects with severe chronic obstructive pulmonary disease (COPD) in whom desaturation is likely to be great and where usage is often most appropriate. METHODS: Fifteen subjects with severe COPD and oxygen desaturation underwent six minute walk tests performed in random order to compare the efficacy of a demand oxygen delivery system (DODS) with continuous flow oxygen. Walk distance, breathlessness, oxygen saturation, resting time, and recovery time (objective and subjective) were recorded and compared for each walk. RESULTS: Breathing continuous oxygen compared with baseline air breathing improved mean walk distance (295 m versus 271 m) and recovery time (47 seconds versus 112 seconds), whilst the lowest recorded saturation (81% versus 74%) and time desaturated below 90% (201 seconds versus 299 seconds) were reduced. When the DODS was compared with air breathing only the walk distance changed (283 m versus 271 m). A comparison of the DODS with continuous oxygen breathing showed the DODS to be less effective at oxygenating subjects with inferior lowest saturation (78% versus 81%), time spent below 90% (284 seconds versus 201 seconds), time to objective recovery (83 seconds versus 47 seconds), and walk distance (283 m versus 295 m). CONCLUSIONS: Neither of the delivery systems was able to prevent desaturation in these subjects. The use of continuous flow oxygen, however, was accompanied by improvements in oxygenation, walk distance, and recovery time compared with air breathing. The DODS produced only a small increase in walk distance without elevation of oxygen saturation, but was inferior to continuous flow oxygen in most of the measured variables when compared directly.     

Body composition and exercise performance in patients with chronic obstructive pulmonary disease.

To investigate whether a compromised nutritional state may limit exercise performance in patients with chronic obstructive pulmonary disease we studied 54 such patients (FEV1 less than 50% and arterial oxygen tension (PaO2) greater than 7.3 kPa) whose clinical condition was stable and who were admitted to a pulmonary rehabilitation centre. Fat free mass was assessed anthropometrically (from skinfold measurements at four sites) and by bioelectrical impedance; creatinine height index and arm muscle circumference were also assessed. The mean (SD) distance walked in 12 minutes was 845 (178) m. No association was established between the distance walked and spirometric measures. A good correlation was found between the distance walked and fat free mass in the whole group (r = 0.73 for impedance measurements and 0.65 for skinfold thickness) and in a subgroup of 23 lean patients (body weight less than 90% of ideal weight; r = 0.66 for impedance measurements and 0.46 for skinfold thickness). Body weight correlated with the distance walked only in the whole group (r = 0.61). On stepwise regression analysis fat free mass measured by bioelectrical impedance, maximal inspiratory mouth pressure, and PaO2 accounted for 60% of the variation in the distance walked in 12 minutes. We conclude that fat free mass, independently of airflow obstruction, is an important determinant of exercise performance in patients with severe chronic obstructive pulmonary disease.     

The shuttle walking test: a reproducible method for evaluating the impact of shortness of breath on functional capacity in patients with advanced cancer

BACKGROUND: Breathlessness leading to exercise limitation is common in patients with advanced cancer and is ineffectively treated. There are few research data to guide clinicians on best practice. The shuttle walking test has been validated for some conditions such as chronic obstructive pulmonary disease but not for advanced cancer. One of the well documented difficulties of doing clinical research in palliative care is the acceptability of assessment tests. This study examined the reproducibility of the shuttle walking test in patients with advanced cancer to help facilitate the systematic evaluation of interventions designed to improve breathlessness. METHODS: Patients performed three shuttle walks on separate days with continuous monitoring of arterial oxygen saturation and heart rate; simple pulmonary function (FEV(1)) was also recorded. Data on quality of life, anxiety, and depression were collected throughout the study period using appropriate questionnaires. Breathlessness was measured before and after exercise using a visual analogue scale. RESULTS: Data from 22 patients were compared between visits 2 and 3. There were no significant differences between the FEV(1) (1.89 v 1.90, p=0.73), distance walked on each test (245 m v 256 m, p=0.14), end-exercise levels of heart rate (107/min v 108/min, p=0.11), oxygen saturation (93.4% v 93.2%, p=0.38), or breathlessness scores (p=0.62) on the two occasions. Indices of quality of life, anxiety, and depression were also not different between the two tests. The investigation was very acceptable to patients, families, and staff. CONCLUSIONS: The shuttle walking test is a reproducible test of functional capacity in ambulant patients with advanced cancer, WHO performance status 1 or 2. The data indicate that a practice session is needed. It is easy to carry out and acceptable for patients with advanced cancer.     

Obstructive sleep apnea, continuous positive airway pressure, and surgery

Patients with obstructive sleep apnea (OSA) who have undergone upper airway surgery could be expected to improve if surgery alleviated some or all of the anatomic obstructions, or continue to desaturate at preoperative levels if the surgery was not corrective. Factors such as morbid obesity, general anesthesia recovery, and operative edema can potentially cause desaturations below preoperative levels. Because of this risk, patients with severe OSA have been considered for protective tracheostomy. The findings of our study suggest that selected patients who would have been past candidates for protective tracheostomy while undergoing surgery for severe OSA can, as an alternative, be considered for immediate postoperative use of nasal continuous positive airway pressure (CPAP). Ten surgical patients with severe OSA who elected surgical treatment were successfully treated with CPAP immediately after extubation and postoperatively to assist with airway patency and hemoglobin saturation. Postoperative followup included monitoring of continuous pulse oximetry, cardiac activity, and intermittent arterial blood gases. Preoperatively, all ten patients had marked decrease in oxygen desaturation levels during sleep, with a mean nadir oxygen saturation (SaO2) to 51.5%. After surgery, all patients in this group maintained SaO2 levels to no lower than 90%, with a mean SaO2 level of 93% while using CPAP on room air (F10(2) 21%) only.