Baseline Saturation Research Articles

Baseline oxygen saturation predicts exercise desaturation below prescription threshold in patients with chronic obstructive pulmonary disease.

Recent studies of exercise-induced hypoxemia in patients with chronic obstructive pulmonary disease (COPD) have shown that oxygen supplementation during exertion increases exercise tolerance and alleviates dyspnea. Although measurements of forced expiratory volume in 1 second and diffusion capacity for carbon monoxide (DLCO) are known to predict exercise-induced desaturation in patients with COPD, baseline oxygen saturation has never been studied as a predictor of exercise-induced desaturation. A retrospective analysis was performed of 100 consecutive patients with forced expiratory volume in 1 second-forced vital capacity ratio of 70% or less who underwent exercise testing for desaturation. Any desaturation to 88% or less with exercise was considered significant. Nineteen patients with total lung capacity of 80% or less were excluded to avoid evaluating those with combined obstructive and restrictive defects; 81 patients remained available for study. Nineteen (51%) of 37 patients with resting saturation of 95% or less desaturated with exercise as opposed to 7 (16%) of 44 with resting saturation of 96% or greater (P =.001). The sensitivity and the negative predictive value of baseline saturation of 95% or less as a screening test for exercise desaturation were 73% and 84%, respectively. If all patients with DLCO of 36% or less were excluded, 40 patients were left for study. Eight (40%) of 20 patients with baseline saturation of 95% or less compared with 0 of 20 with resting saturation of 96% or greater desaturated with exercise (P =.006). In this subset, the sensitivity and the negative predictive value of baseline saturation of 95% or less as a screening test for exercise desaturation both improved to 100%. In patients with COPD, baseline saturation of 95% or less is a good screening test for exercise desaturation, especially in patients with DLCO greater than 36%. This readily available office screening procedure merits further study in larger prospective patient cohorts.

Noninvasive optical method of measuring tissue and arterial saturation:?an application to absolute pulse oximetry of the brain

We present a frequency-domain optical method for real-time noninvasive measurement of absolute tissue and arterial saturation. This method is based on quantitative measurement of the tissue absorption spectrum (for tissue saturation) and of the amplitude of the arterial-pulsation-induced absorption oscillations (for arterial saturation) at eight wavelengths in the range 633-841 nm. We report results obtained from readings taken from the forehead of a healthy volunteer, showing baseline saturation values of 74.7+/-0.2% (tissue) and 96.9+/-0.5% (arterial). These values dropped to minimum values of 71.6+/-0.2% and 90.0+/-0.2% , respectively, after 1 min of reduced inspired oxygen concentration [10% (by volume) O(2) from a baseline value of 21% O(2) ].

Carbogen-induced changes in rat mammary tumour oxygenation reported by near infrared spectroscopy.

We have evaluated the ability of steady-state, radially-resolved, broad-band near infrared diffuse reflectance spectroscopy to measure carbogen-induced changes in haemoglobin oxygen saturation (SO2) and total haemoglobin concentration in a rat R3230 mammary adenocarcinoma model in vivo. Detectable shifts toward higher saturations were evident in all tumours (n = 16) immediately after the onset of carbogen breathing. The SO2 reached a new equilibrium within 1 min and remained approximately constant during 200–300 s of administration. The return to baseline saturation was more gradual when carbogen delivery was stopped. The degree to which carbogen increased SO2 was variable among tumours, with a tendency for tumours with lower initial SO2 to exhibit larger changes. Tumour haemoglobin concentrations at the time of peak enhancement were also variable. In the majority of cases, haemoglobin concentration decreased in response to carbogen, indicating that increased tumour blood volume was not responsible for the observed elevation in SO2. We observed no apparent relationship between the extent of the change in tumour haemoglobin concentration and the magnitude of the change in the saturation. Near infrared diffuse reflectance spectroscopy provides a rapid, non-invasive means of monitoring spatially averaged changes in tumour haemoglobin oxygen saturation induced by oxygen modifiers. © 1999 Cancer Research Campaign

Factors affecting oxygen saturation during methacholine challenge in a mixed population

Bronchial challenge with methacholine or histamine is associated with a reduction in arterial oxygen tension, which can be appreciable. In this study, oxygen saturation was monitored during methacholine challenge in subjects with and without respiratory disease, over a wide age range, in order to identify factors predicting a large fall in saturation during the challenge. Two hundred and twenty subjects aged 24–86 years were included, comprising 15 healthy adult volunteers, and 205 adults from a random sample of the local adult population taking part in a survey of bronchial responsiveness. Subjects with ischaemic heart disease or baseline FEV 1 <60% predicted were excluded. Methacholine challenge was performed by the Newcastle Dosimeter technique; oxygen saturation (SaO 2) was monitored using a pulse oximeter and finger probe. Of the 220 subjects, 27% were current smokers and 39·5% were ex-smokers; 26% reported asthma or bronchitis. Mean baseline FEV 1 was 100% predicted; mean baseline saturation was 97%. Mean fall in saturation was 3·2% (range 0–17·5%). Multiple regression analysis revealed that fall in saturation during methacholine challenge is related to baseline FEV 1, baseline SaO 2, log of total methacholine dose inhaled, and fall in FEV 1 during challenge. Change in saturation was not related to subject age, smoking history, reported asthma or bronchitis, or the presence of respiratory symptoms. Methacholine challenge produces a significant fall in oxygen saturation, but this is not greater in subjects who are old or have low baseline saturation.

Effect of arterial oxygen desaturation on six minute walk distance, perceived effort, and perceived breathlessness in patients with airflow limitation.

The effect of exercise induced hypoxaemia in determining submaximal exercise capacity, perceived breathlessness, and perceived exertion is not known. The purpose of this study was to investigate the relation of these variables to the results of lung function tests and the degree of hypoxaemia during submaximal exercise in patients with airflow limitation. Forty two patients with chronic obstructive airways disease and 28 patients with chronic severe asthma were studied. Spirometry was performed and gas transfer (TLCO) and lung volumes were measured. Submaximal exercise capacity was assessed with a standardised six minute walk test. Arterial oxygen desaturation during the walk test was monitored by a portable pulse oximeter. Patients rated their perceived degree of respiratory impairment on a Medical Research Council (MRC) breathlessness scale before the walk. Perceived breathlessness was measured by means of a linear visual analogue scale and exertion on the Borg scale after the walk. The six minute walk distance was strongly correlated (r value) with TLCO (0.68), peak expiratory flow (PEF: 0.55), forced expiratory volume in one second (FEV1: 0.53), transfer coefficient KCO: 0.49), age (-0.49), and forced vital capacity (FVC: 0.48) but not with oxygen desaturation during the walk. Walk distance was also correlated with the breathlessness rating on the MRC scale (-0.52), but less strongly with perceived breathlessness (-0.35) and perceived exertion (-0.30). The prediction equation for the six minute walk distance in metres (6MD) generated by multiple regression analysis was 6MD = 387 + 29.7 (TLCO) -3.1 (age) + 0.35 (PEF 1/min), which accounted for 50% of the total variance in walk distance. The mean level of saturation during the walk correlated most significantly with TLCO (0.55), FEV1/FVC (0.54), and PEF (0.48), but not with walk distance or with the rating on any of the analogue scales. The prediction equation produced by multiple regression analysis for the mean level of saturation during the walk was MEANSAT(%) = 1.3(TLCO) + 1.5 (base-line saturation) - 0.01 (6MD) - 54. Oxygen desaturation during the six minute walk is not related to walk distance, nor does it determine the degree of perceived exertion or perceived breathlessness in patients with airflow limitation. Patients who consider themselves the most disabled by breathlessness have the shortest six minute walk distance but do not necessarily have appreciable desaturation.

Age, anemia, and obesity-associated oxygen desaturation during upper gastrointestinal endoscopy.

Although upper gastrointestinal endoscopy is generally a safe procedure, it is known to be associated with arterial oxygen desaturation. We studied 82 patients undergoing diagnostic upper gastrointestinal endoscopy following a standard premedication consisting of xylocaine throat spray and intravenous midazolam. The mean duration of endoscopy was 8.5 +/- 0.42 min and the mean dose of midazolam was 6.3 +/- 0.15 mg. The baseline SaO2 was 94.91 +/- 0.27% and it decreased after pre-medication to 92.84 +/- 0.40% (p < 0.001) and after intubation to 91.21 +/- 0.40% (p < 0.001). A fall greater than 4% saturation occurred for 15.68% of the total endoscopy time. SaO2 < 90% was seen for 16.7% and SaO2 < 85% occurred for 2.33% total endoscopy time. In patients > 65 years old, hemoglobin < 10 g/dl, or body mass index > 28, the baseline saturation was significantly lower and a reduced SaO2 was seen throughout the procedure. We identify old age, anemia, and obesity as independent risk factors for arterial oxygen desaturation. We recommend continuous monitoring before sedation, and giving supplemental oxygen to patients with these risk factors from the outset of upper gastrointestinal endoscopy.

Sleep quality in children with asthma treated with theophylline or cromolyn sodium

The effect of theophylline and cromolyn sodium on sleep was studied in 10 children with asthma who were 10 to 17 years of age (mean 13.5 +/- 2.4 years). Theophylline or cromolyn sodium was taken for 14 days in a double-blind, crossover, placebo-controlled trial. Theophylline blood levels before sleep were 10.2 +/- 4 micrograms/ml during the theophylline period. There was no difference in pulmonary function between the two periods. Theophylline did not disrupt sleep as measured by sleep latency, total sleep time, sleep efficiency, movement time, microarousals, and arousals. Apneic episodes (greater than or equal to 10 seconds) were of central origin and less frequent during the theophylline period (p less than 0.05). Arterial oxygen desaturation (greater than 5% decrease from baseline saturation when awake) was less frequent during the theophylline treatment (p less than 0.05). We conclude that theophylline treatment of the children's asthma did not disrupt sleep and appeared to have a protective effect in regard to apnea, hypopnea, and arterial oxygen saturation.

Mixed venous oximetry during automatic implantable cardioverter-defibrillator placement

Mixed venous oxygen saturation (Sv̄0 2) monitoring was used to assess tissue and circulatory recovery following induced ventricular tachycardia or fibrillation in 17 patients undergoing surgery for automatic implantable cardioverter-defibrillator (AICD) placement. Return of systemic arterial pressure conventionally determines adequate recovery. The duration of circulatory arrest during defibrillator threshold (DFT) testing, measured from the moment of absent phasic pressure at the radial artery until its return, was 18 ± 18 seconds (mean ± SD, n = 118 episodes). The absolute decrease in Sv̄0 2 from baseline to nadir for these 118 episodes was 14% ± 6% absolute, and correlated well with the duration of circulatory arrest ( r = 0.757, P = 0.0001). The time from onset of phasic arterial blood pressure to the nadir of Sv̄0 2, available for 46 episodes, was 28 ± 14 seconds, and did not correlate with the duration of arrest. The time from onset of phasic pressure to the return of Sv̄O 2 to within 1 % (absolute) of baseline saturation, available for 84 episodes, was 52 ± 32 seconds and, in the aggregate, correlated poorly ( r = 0.401) with duration of arrest. Simultaneous recording of arterial pressure and Sv̄0 2 (n = 41) showed that arterial recovery (6 ± 3 seconds) occurred long before Sv̄0 2 recovery (48 ± 16 seconds, P = 0.0001). The authors interpret these data as showing that mixed venous oximetry, compared to arterial blood pressure, provides a more sensitive indicator of tissue recovery following periods of circulatory arrest during DFT testing of AICDs.

Cheyne-Stokes Respiration Presenting as Sleep Apnea Syndrome: Clinical and Polysomnographic Features

This study reports polysomnographic features of five patients with Cheyne-Stokes respiration (CSR). They were referred for evaluation of presumptive sleep apnea syndrome on the basis of history and physical examination, but were found to have predominantly CSR on all-night sleep study. On the initial polysomnographic study, CSR comprised 47 to 86% of all disordered-breathing events. Cheyne-Stokes respiration resulted in considerable oxyhemoglobin desaturation (mean baseline saturation was 95 +/- 4 +/- SD, and lowest saturation was 76 +/- 8). More than one-half of all CSR events resulted in awakenings or arousals. Evidence of upper airway obstruction was noted in the majority of CSR events in three of five patients. Four patients were treated with theophylline; one who refused drug therapy was treated with nasal continuous positive airway pressure (CPAP). Comparison of sleep studies before and after therapy showed a significant decrease in the CSR index (29 +/- 11 versus 2 +/- 2) and in the maximal oxyhemoglobin desaturation associated with CSR (13 +/- 5 versus 3 +/- 2), and an improvement in lowest O2 saturation associated with CSR (76 +/- 8 versus 91 +/- 4). Total disruptions in sleep architecture per hour of sleep improved significantly with therapy (46 +/- 21 versus 20 +/- 8). We conclude that the clinical presentation of CSR can be indistinguishable from that of the "traditional" sleep apnea hypopnea syndrome and can result in major oxyhemoglobin desaturation and sleep fragmentation. Theophylline results in considerable improvement in the disordered breathing of CSR during sleep.

Bile acid feeding and hepatic sterol metabolism: Effect of deoxycholic acid

The effect of deoxycholic acid feeding on hepatic sterol metabolism was studied in 9 subjects with cholesterol gallstones. Fifteen milligrams per kilogram of deoxycholic acid was given daily for 1–2 wk before cholecystectomy. During the study the subjects were maintained on a standard diet containing approximately 500 mg of cholesterol daily. Parameters investigated included bile acid pool composition, HMG-CoA reductase, 7α-hydroxylase, microsomal cholesterol, biliary lipids, and plasma lipids. No relevant side effects were noted. At the end of the treatment the fed bile acid constituted nearly 90% of the bile acid pool. In the treated group hepatic HMG-CoA reductase was reduced by 45%, as compared with the control value (mean ± SD : 40.4 ± 10.3 pmol/min/mg protein vs. 72.9 ± 8.4 pmol/min/mg protein; P < 0.01); 7α-hydroxylase activity did not change, whereas microsomal cholesterol was somewhat reduced (65.2 ± 9.1 nmol/mg protein vs. 76.5 ± 12.4 nmol/mg protein of the controls; P < 0.05). Baseline saturation index of the bile was not different after treatment. Plasma cholesterol was lowered by 20% (184 ± 17 mg/dl vs. 232 ± 27 mg/dl before treatment; P < 0.03), whereas plasma triglycerides were unaffected by DCA feeding. In conclusion, deoxycholic acid administration seems to depress the hepatic synthesis of cholesterol without changing biliary lipid composition and, in addition, it lowers plasma cholesterol.