Ear oximetry: a noninvasive method for detection of patent foramen ovale: a study comparing dye dilution method and oximetry with contrast transesophageal echocardiography.
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BACKGROUND AND PURPOSE: Patent foramen ovale (PFO) may play an important role as a risk factor for ischemic stroke and some other neurological conditions. There is a need for low-cost and noninvasive methods for the detection of PFO. This study evaluates the accuracy of two simple bedside tests, the dye dilution method and ear oximetry, in the detection of PFO. METHODS: Dye dilution curves and ear oximetry recordings with a noninvasive ear densitometer were obtained from consecutive cryptogenic stroke patients referred for contrast transesophageal echocardiography (TEE). All test results were blindly assessed for the presence of PFO. Sensitivity and specificity were calculated with TEE used as a reference method. kappa statistics were used to measure interrater agreement. RESULTS: Dye dilution curves were obtained from 67 patients. Dye dilution correctly diagnosed 35 of the 46 patients who had PFO in TEE and all the 21 patients without PFO. Thus, the sensitivity (95% CI) of the dye dilution method was 76% (61% to 87%) and its specificity 100% (84% to 100%). Ear oximetry was done on 83 patients. Oximetry correctly diagnosed 45 of the 53 patients who had PFO in TEE and all of the 30 patients without PFO. Thus, the sensitivity of ear oximetry was 85% (72% to 93%) and its specificity 100% (88% to 100%). The interrater agreement was excellent (kappa value 0.94 for dye dilution and 0.90 for oximetry). CONCLUSIONS: Dye dilution and oximetry are both sensitive and specific methods for the detection of PFO. Oximetry has the following primary advantages over the currently available diagnostic methods: it is noninvasive, safe, and inexpensive and causes no discomfort for the patient. We suggest that oximetry could be used as a first-line screening method for PFO in patients with cryptogenic stroke. Ear oximetry also has potential use in epidemiological studies. (+info)
Carbon dioxide contributes to the beneficial effect of pressurization in a portable hyperbaric chamber at high altitude.
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Regional cerebral oxygenation (rSO2) and peripheral oxygen saturation (SpO2) have been studied in subjects inside a portable hyperbaric chamber at altitude during pressurization. The effects of the accumulation of carbon dioxide within the chamber on rSO2 and SpO2 have also been investigated. Three studies of cerebral regional oxygenation were undertaken, using near-IR spectroscopy, in subjects who had ascended to 3475 m in the Alps, 4680 m in the Andes or 5005 m in the Himalayas. At 3475 m and 5005 m the effects of the removal of inspired carbon dioxide by a soda lime scavenger were also studied. On pressurization of the chamber to 19.95 kPa, inspired carbon dioxide rose within the chamber from 0.03% (0.06 kPa) ambient to over 1% (1.3 kPa). At 5005 m, SpO2 rose from a baseline of 79.5% (S.D. 4.5%) to 95.9% (2.0%) (P<0.0001), and cerebral rSO2 rose from 64.6% (3.4%) to 69.4% (3.6%) (P<0.0001). The introduction of a soda lime CO2 scavenger into the breathing circuit resulted in a drop in SpO2 from 95.9% (2.03%) to 93.6% (2.07%) (P<0.001) and a fall in rSO2 from 69.4% (3.64%) to 68.5% (3.5%) (P<0.01). Chamber pressure was maintained throughout at 19.95 kPa. Similar changes were seen at the other altitudes. Cerebral rSO2 increased rapidly following pressurization at all three altitudes. Scavenging of inspired carbon dioxide was associated with a significant fall in cerebral rSO2 and SpO2, and we estimate that the contribution of carbon dioxide may account for up to one-third of the beneficial effect of the portable hyperbaric chamber. (+info)
The combination of bedside swallowing assessment and oxygen saturation monitoring of swallowing in acute stroke: a safe and humane screening tool.
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BACKGROUND: dysphagia is common in acute stroke. Accurate detection of the presence or absence of aspiration by bedside swallowing assessment is difficult without objective methods, tending to over-diagnose aspiration. As a result, some patients suffer restricted oral intake unnecessarily. OBJECTIVE: we examined the predictive values of pulse oximetry and speech and language therapy bedside swallowing assessment in the detection of aspiration compared with videofluoroscopy. DESIGN: a double-blind observational study. SETTING: two university teaching hospitals. SUBJECTS: we studied 53 patients whose acute strokes were confirmed by computed tomography scan. METHODS: Each subject had initial standard bedside swallowing assessment, closely followed by simultaneous and mutually blinded pulse oximetry, swallowing assessment and videofluoroscopy. RESULTS: 15 of 53 subjects aspirated. Bedside swallowing assessment and saturation assessment at > or = 2% desaturation gave good sensitivity (80% and 87% respectively), but low positive predictive values (50% and 36% respectively). Both assessments mistook laryngeal penetration for aspiration. Re-analysis with aspiration +/- penetration as a new endpoint improved bedside swallowing assessment positive predictive values to 83% (chi2 =3.59, P=0.032). Sensitivity of saturation assessment was maintained at 86%, positive predictive values of saturation assessment improved to 69% (chi2=6.74, P=0.009). The combination of bedside swallowing assessment and saturation assessment versus aspiration + penetration gave a positive predictive value of 95%. CONCLUSIONS: screening by saturation assessments detects 86% of aspirators/penetrators and should be followed immediately by bedside swallowing assessment, as the combination of the two assessments gives the best positive predictive value. For patients with acute stroke, we advocate a 10 ml water-swallow screening test with simultaneous pulse oximetry by suitably trained medical and nursing staff. Use of this screening test would improve dysphagia detection whilst minimizing unnecessary restriction of oral intake in stroke patients. (+info)
Influence of patient posture on oxygen saturation during fibre-optic bronchoscopy.
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This study was designed to investigate the effect of posture on oxygen saturation during fibre-optic bronchoscopy (FOB). Thirty-eight consecutive patients requiring diagnostic FOB were randomized into two groups according to the initial posture in which the FOB was performed. In group 1 (20 patients), FOB was commenced supine, and in group 2 (18 patients) in a semi-recumbent position (45 degrees from horizontal). Sedation with midazolam was titrated according to clinical response. All patients received atropine 0.6 mg intravenously and topical lignocaine. Observations of peak, trough and plateau oxygen saturation and pulse rate were recorded during six study periods, each lasting 3 min. Periods 1 and 2 were pre- and post-sedation without supplemental oxygen, respectively. The bronchoscope was then inserted into the distal end of the trachea and observations taken during periods 3 and 4 (no supplemental oxygen) and periods 5 and 6 (2 l oxygen by nasal cannulae). In group 1, posture was changed from supine to semi-recumbent from periods 3-4 and reversed in periods 5 and 6. In group 2, posture changes were in reverse sequence. Patients with initial oxygen saturation of less than 90% or showing a fall below 85% during FOB were excluded. Five patients from each group were withdrawn because of hypoxia. In both groups, oxygen saturation fell significantly (P<0.001) following sedation. There was no significant change in saturation (peak, trough or plateau) with change in posture from supine to semi-recumbency (group 1) or the reverse (group 2). These correspond to periods 3-4 and 5 6 in both groups. Supplemental oxygen was associated with a significant rise in oxygen saturation in both postures, attaining levels close to presedation levels. (+info)
Pulse oximetry, severe retinopathy, and outcome at one year in babies of less than 28 weeks gestation.
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AIM: To determine whether differing policies with regard to the control of oxygen saturation have any impact on the number of babies who develop retinopathy of prematurity and the number surviving with or without signs of cerebral palsy at one year. METHODS: An examination of the case notes of all the 295 babies who survived infancy after delivery before 28 weeks gestation in the north of England in 1990-1994. RESULTS: Babies given enough supplemental oxygen to maintain an oxygen saturation of 88-98%, as measured by pulse oximetry, for at least the first 8 weeks of life developed retinopathy of prematurity severe enough to be treated with cryotherapy four times as often as babies only given enough oxygen to maintain an oxygen saturation of 70-90% (27.2% v 6.2%). Surviving babies were also ventilated longer (31.4 v 13.9 days), more likely to be in oxygen at a postmenstrual age of 36 weeks (46% v 18 %), and more likely to have a weight below the third centile at discharge (45% v 17%). There was no difference in the proportion who survived infancy (53% v 52%) or who later developed cerebral palsy (17% v 15%). The lowest incidence of retinopathy in the study was associated with a policy that made little use of arterial lines. CONCLUSIONS: Attempts to keep oxygen saturation at a normal "physiological" level may do more harm than good in babies of less than 28 weeks gestation. (+info)
Autonomic neuropathy is linked to nocturnal hypoxaemia and to concentric hypertrophy and remodelling in dialysis patients.
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BACKGROUND: Autonomic dysfunction and sleep apnoea are frequent complications of chronic renal failure. Since nocturnal hypoxaemia in sleep apnoea dampens autonomic reflexes, we postulated that altered autonomic control is in part linked to nocturnal hypoxaemia in uraemic patients. METHODS: To test the hypothesis we performed continuous monitoring of O(2) saturation during night by pulse oximetry (Ohmeda-Biox) as well as echocardiography, 24-h ambulatory blood pressure monitoring, and standard tests of autonomic function in 50 patients on chronic dialysis (40 on haemodialysis and 10 on CAPD). For haemodialysis patients all studies were performed during a mid-week non-dialysis day. RESULTS: Twenty-five patients had at least one episode of nocturnal hypoxaemia (median 13, interquartile range 4-31) while the other 25 patients had no episodes at all. Minimal and average SaO(2) were strongly interrelated (r = 0.64, P = 0.0001). In a multiple regression model, besides age, average nocturnal SaO(2) was the only independent predictor of the parasympathetic function. Similarly, average nocturnal SaO(2) was the only independent predictor of the autonomic response to standing. Sex, 24-h mean arterial pressure, body mass index, haematocrit, serum albumin, serum parathyroid hormone and duration of dialysis treatment had no independent effect on the autonomic tests. Interestingly, the average nocturnal SaO(2) and the interaction between the responses to the autonomic tests were independently related to posterior-wall thickness. This interaction term represented also the stronger independent predictor of the relative wall thickness of the left ventricle. In a multiple logistic regression model the interaction parasympathetic-sympathetic function was the only independent predictor of concentric remodelling or hypertrophy, while average nocturnal SaO(2) entered into this model (P = 0.03) only after exclusion of the autonomic function interaction term. CONCLUSIONS: Thus, altered cardiovascular autonomic control appears to be linked to nocturnal hypoxaemia and to concentric hypertrophy or remodelling in dialysis patients. Since nocturnal hypoxaemia is an established cardiovascular risk factor, altered autonomic control is a potential mechanism whereby hypoxaemia may trigger cardiovascular events in dialysis patients. It remains to be seen whether the link between nocturnal hypoxaemia and autonomic dysfunction is a causal one. (+info)
Neutrophil defensins mediate acute inflammatory response and lung dysfunction in dose-related fashion.
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High concentrations of neutrophil defensins from airway and blood have been reported in patients with inflammatory lung diseases, but their exact role is unclear. We investigated the direct effect of defensins on the lungs of mice. Intratracheal instillation of purified defensins (5-30 mg/kg) induced a progressive reduction in peripheral arterial O(2) saturation, increased lung permeability, and enhanced the lung cytochrome c content. These indexes of acute lung dysfunction were associated with an increased total cell number and a significant neutrophil influx into the lung [5.1 +/- 0.04% in control vs. 48.6 +/- 12.7% in the defensin (30 mg/kg) group, P < 0.05]. Elastase concentrations in the bronchoalveolar lavage (BAL) fluids increased from 38 +/- 11 ng/ml (control) to 80 +/- 4 ng/ml (defensins, P < 0.05). Five hours after defensin instillation, concentrations of tumor necrosis factor-alpha and macrophage inflammatory protein-2 in BAL fluid were significantly increased. High levels of monocyte chemoattractant protein-1 in BAL fluid and plasma were also found after defensin stimulation. We conclude that intratracheal instillation of defensins causes acute lung inflammation and dysfunction, suggesting that high concentrations of defensins in the airways may play an important role in the pathogenesis of inflammatory lung diseases. (+info)
A survey of nocturnal hypoxaemia and health related quality of life in patients with cryptogenic fibrosing alveolitis.
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BACKGROUND: A survey of overnight oximetry was conducted to estimate the prevalence of nocturnal hypoxaemia in patients with cryptogenic fibrosing alveolitis and to establish whether nocturnal hypoxaemia is related to quality of life. METHODS: All patients with cryptogenic fibrosing alveolitis attending Nottingham City Hospital were invited to enter the study. Spirometric measurements and capillary blood gas tensions were obtained and overnight oxygen saturation was recorded at home. Quality of life was assessed using the Short Form-36, Chronic Respiratory Questionnaire, Hospital Anxiety Depression Scale, and Epworth Sleepiness Score questionnaires. RESULTS: Sixty seven eligible patients were identified and 50 agreed to enter the study, although two were subsequently excluded because they already used oxygen overnight. In the remaining 48 the mean (SD) overnight oxygen saturation (SaO(2)) was 92.5 (4.3)% and the median number of dips greater than 4% per hour was 2.3 (interquartile range 1.5-5.3). Daytime oxygen level predicted mean overnight SaO(2) (1.94%/kPa, 95% CI 1.22 to 2.66, p<0.001) but percentage predicted forced vital capacity (FVC) did not (0.018%/% predicted FVC, 95% CI -0.04 to 0.08, p=0.5). Nocturnal hypoxaemia was associated with decreased energy levels and impaired daytime social and physical functioning, and these effects were independent of FVC. CONCLUSIONS: Nocturnal hypoxaemia is common in patients with cryptogenic fibrosing alveolitis and may have an impact on health related quality of life. (+info)