Pulse oximetry in a cohort study of sickle cell disease

Oxygen saturation was determined by pulse oximetry in a representative sample of Jamaican patients with steady state sickle cell disease in a cohort study from birth. There were 220 with homozygous sickle cell (SS) disease and 142 with sickle cell-haemoglobin C (SC) disease aged 9-18 years, and 122 with a normal haemoglobin (AA) genotype aged 15-18 years. Pulse oximetry (SpO2) values were lower in SS disease (mean [95 percent confidence interval]), 92.5 [92.0-93.3]. Inhalation of 100 percent oxygen in SS patients with 02 saturations below 90 percent consistency increased saturation to 99-100 percent. In SS disease, Sp02 correlated positively with haemoglobin and fetal haemoglobin and negatively with reticulocyte counts but not MCHC, MCV or bilirubin level. Mean Sp02 in SS subjects with a normal alpha globin gene complement (mean[SD], 91.7 [3.9]percent) was lower than in heterozygotes (93.4 [4.0] percent) or homozygotes (96.1 [3.0] percent) for alpha+thalassaemia, the effects of alpha-thalassaemia not being explained by differences in haemoglobin or MCHC. In SS disease, Sp02 levels were not associated with age (within this age range), sex, number of sick clinic visits or number of hospital admissions. Higher Sp02 levels were associated with greater heights and weights, more frequent painful crises and less frequent acute chest syndrome, but these associations were not significant after adjustment for haemoglobin level. Desaturation is common in steady-state SS disease and knowledge of the individual's steady-state value may be important in the interpreting low value during acute complications.(AU)

Pulse oximetry in cohort study of sickle cell disease

Oxygen saturation was determined by pulse oximetry in a representative sample of Jamaican patients with steady-state sickle cell disease in a cohort study from birth. There were 220 with homozygous sickle cell (SS) disease and 142 with sickle cell- haemoglobin C (SC) disease aged 9-18 years, and 122 with a normal haemoglobin (AA) genotype aged 15-18 years. Pulse oximetry (SpO2) values were lower in SS disease (mean [95 percent confidence interval], 92.5 [92.0-93.0]) than in SC disease (96.7 [96.9-96.9]) or AA controls (97.1 [96.8-97.3]). Inhalation of 100 percent oxygen in SS patients with O2 saturations below 90 percent consistently increased saturation to 99-100 percent. In SS disease, SpO2 correlated positively with haemoglobin and fetal haemoglobin and negatively with reticulocyte counts but not with MCHC, MCV or bilrubin level. Mean SpO2 in SS subjects with a normal alpha globin gene complement (mean [SD], 91.7 [3.9] percent) was lower than in heterozygotes (93.4 [4.0] percent) or homozygotes (96.1 [3.0] percent) for O+ thalassaemia, the effects of O-thalassaemia not being explained by differences in haemoglobin or MCHC. In SS disease, SpO2 levels were not associated with age (within this age range), sex, number of sick clinic visits or number of hospital admissions. Higher SpO2 levels were associated with greater height and weight, more frequent painful crises and less frequent acute chest syndrome, but these associations were not significant after adjustment for haemoglobin level. Desaturation is common in steady-state SS disease and knowledge of the individual's steady-state value may be important in the interpreting low values during acute complications.(AU)

What is the prevalence and significance of oxygen desaturation in clinically well patients with sickle-cell disease? - abstract

The prevalence and significance of oxygen desaturation (SaO2) is unknown in asymptomatic patients with sickle-cell disease (SCD). Because of the invasive nature of measuring SaO2, until recently, insufficient data have been obtained on clinically well subjects with SCD. SaO2, was measured by pulse oximetry, on 913 occasions in 485 asymptomatic children (112 AA, 143 SC and 220 SS) aged 9.1-17.5 years during routine clinic visits. The SpO2 in SS disease (mean ñ SD 92.5 ñ 4.3 percent) was significantly lower than in AA (97.1 ñ 1.3 percent) or SC (96.7 ñ 1.4 percent) genotypes (0<0.001) and within genotype and within patient variance was greater. SpO2 did not correlate with age, sex or growth patterns nor with the frequency or "sick" visits to the clinic or with hospital admissions. Only a weak positive correlation with painful crisis and a negative one with acute chest syndrome were noted but none with the other major clinical manifestations of the disease. Oxygen desaturation < 95 percent was present in 74 percent of asymptomatic patients, and desaturation between 80 and 90 percent in 25 percent. The apparent lack of correlation with clinical severity casts doubt on the significance of these levels of desaturation in SCD, which may be a reflection of compensatory mechanisms (AU)

The supply of oxygen to the Queen Elizabeth Hospital - abstract

The Queen Elizabeth Hospital gets its oxygen supplies as compressed gas in cylinders from the sole producer in Barbados. Expenditure on oxygen will have risen to B$500,000 per annum in 1988. The rising use and cost of oxygen, stimulated the Queen Elizabeth Hospital Administration to consider generation of its oxygen. A cost analysis revealed that by doing this, it may be possible to save B$250,000 in expenditure on oxygen annually. An oxygen concentrator was installed at the Hospital and put into use in November, 1988 (AU)

Should air-oxygen nitrous oxide-oxygen in general anaesthesia?

The use of compressed air-oxygen mixtures to replace nitrous oxide-oxygen in general anaesthesia was investigated in 378 patients. There were neither prolongations of recovery time nor instances of awareness under anaesthesia. The cost of general anaesthesia using compressed air-oxygen was about half that for nitrous oxide-oxygen mixtures.(AU)

Can compressed air/oxygen replace nitrous oxide/oxygen in general anaesthesia? a preliminary survey - abstract

The use of compressed air/oxygen mixtures to replace nitrous oxide/oxygen in general anaesthesia is investigated in 378 patients. There was no prolongation of recovery time nor instances of awareness under anaesthesia. The cost of general anaesthesia, using compressed air/oxygen mixtures was BDS$10.05 per patient while the cost of using nitrous oxide/oxygen mixtures was BD$20.11 per patient (AU)

Some medical and economic implications of oxygen therapy - abstract

Oxygen is widely used in hospital practice. This paper documents critically its use in a 500-bed teaching hospital in Kingston, Jamaica. Three aspects of oxygen therapy were examined, namely, the prescription and administration of oxygen, the condition and maintenance of oxygen equipment and lastly the supplies of oxygen to the hospital. It was apparent that the same thought and precision normally accorded the prescribing of drugs was not exercised in the case of oxygen, which often seemed to be given as a routine measure. It was also noted that both medical and nursing staff were often unfamiliar with the performance of oxygen equipment and not always able to supervise its use. Little awareness of the likely inspired concentrations delivered by oxygen equipment was found. Much of the equipment used for oxygen therapy, including anaesthetic machines, was found to be defective and no regular preventive maintenance was being carried out. As a result, there was an enormous wastage of oxygen as well as deficient therapy. There was an enormous rise in the cost of oxygen. The cost of a 100-cubic foot oxygen was found to have increased from J$3.3 in 1977 to J$14.8 in 1984, and its transportation cost from the manufacturing plant to the hospital from J$1,000 to J$4,000 per month. Since the cost of oxygen is likely to rise even further, serious consideration should be given to the installation of oxygen concentrators or possibly to the use of industrial grade oxygen. In addition, there is clearly a need for further education in the use of oxygen and for improved maintenance and operation of equipment used for oxygen therapy (AU)

Oxygen, its supply and usage at the University Hospital of the West Indies - a cost-benefit approach

A survey of the literature dealing with the administration of oxygen with respect to the administration of oxygen with respect to the historical development and techniques used in different types of institutions, countries and environments has been presented. Against this background, a descriptive study of the administration of oxygen at the University Hospital of the West Indies (U.H.W.I.) in terms of methodology and cost-efficiency was carried out. It was found that U.H.W.I. spends $38,000 per month in purchasing and transporting oxygen, and the purchase and transportation rates are increasing exponentially. The soaring costs are only aggravated by the high incidence of wastage occurring throughout the hospital. The most frequent cause of wastage is leakage from defective equipment. However, the greatest rate of measured wastage (in volume per unit time) is due to inadequate supervision of oxygen equipment. It was revealed that the total rate of oxygen wastage due to poor supervision approximately doubles that being wasted because of leakage from outlets. Based on such findings, it is suggested that stringent steps be put in force to minimise wastage as a result of defective equipment or unsatisfactory administration at the bedside. Simultaneously it is advised that the Hospital Administration reinforce the modes of quality and quantity control already in existence. It is proposed that special consideration be given to the investing in techniques and equipment which in the long term, would prove to be cost-saving. Examples of these are the routine use of compressed air or industrial oxygen and the institution of a "Modular System" such as a compressor-concentrator-storage tank system or any modification of this to meet the specific needs of the Hospital

Determinants of haemoglobin level in sickle cell-haemoglobin C disease

The determinants of steady state haemoglobin levels in sickle cell-haemoglobin C (SC) disease were investigated by measuring routine haematological and biochemical indices, red cell survival, oxygen affinity, pitted erythrocytes, and red cell and plasma volumes in 31 adult patients (15 male; 16 female). Red cell survival was shortened in all subjects, and was positively correlated with haemoglobin level. However, many haemoglobin values were within the normal range, especially in male subjects. Palpable splenomegaly, which occurred in 53 percent of patients, did not appear to effect haemoglobin levels, red cell survival, plasma volume, but was associated with lower platelet counts and decreased pitted red cells. Sex related differences were found in total haemoglobin, packed cell volume, conductivity cell volume, red cell count, and in the blood volume measurements. Red cell, plasma and total blood volumes in patients varied with weight and cube of height in manner observed in normal subjects, although red cell volumes were lower and plasma volumes were greater than in normal subjects of given height and weight. Anaemia in SC disease is related to the haemolytic rate but the major determinant appears to be an inappropriate increase in plasma volume (Summary)

Oxygen transport in sickle cell anemia

Oxygen transport and delivery in sickle cell anemia are discussed in terms of hemodynamics and blood oxygen affinity. The current concepts of the regulation of the hematocrit value by the oxygen pressure on the venous side of the renal capillary are reviewed, and the concept of 'anemia' redifined. The marked right shift in the oxygen dissociation curve of sickle cell anemia blood is analyzed in terms of the sickling process, the hemolytic anemia, and increase in 2.3 diphosphoglycerate. The clinical implications of this right shift in perpetuating sickling are discussed in the light of its possible correction by treatment with sodium cyanate (AU)

Epidemic of suicide by malathion poisoning in Guyana

Malathion, an organic phosphate insecticide, has become the agent most commonly used for suicides attempts in Guyana. The clinical characteristics of 264 cases are described. As with other types of organic phosphate poisoning, atropine is the mainstay of therapy after exposure to the toxin is terminated. The value of oximes in the treatment of malathion poisoning is not clear. The increase in malathion suicides is related to sociocultural factors.(Summary)

Cardio-pulmonary responses and gas exchange during exercise in adults with homozygous sickle-cell disease (sickle-cell anaemia)

Cardio-pulmonary responses and gas exchange during progressive exercise, the ventilatory response to hypercapnia and anthropometric indices were measured in twenty-two Jamiacan adults with homozygous sickle-cell disease. Their anthropometric indices and exercise performances were compared with those observed in healthy but sedentary adults in the Caribbean. The patients had long lower limbs for their height; their body fat, proportion of lean body mass as muscle and vital capacity reduced. Haemoglobin concentration ranged from 4 to 10g/100ml. Heart rate and ventilation were normal at rest. During exercise in the male patients haemoglobin concentrations below about 8g/100ml were associated with an increased demand for anaerobic metabolism. This resulted in excessive lac ticacidaemia and increased ventilation at standard oxygen uptake (hyperpnoea). The ventilation-tidal volume relationship was normal. When allowance was made for differences in body muscle, anaemia did not appear to affect the heart-rate response to exercise. Hyperventilation with respect to carbon dioxide output, increased alveolar-arterial oxygen-tension gradients and abnormal deadspace ventilation during exercise indicated a pulmonary perfusion disturbance with mixed venous shunting. The most likely basis for this disorder was considered to be the sickling phenomenon. Arterial hypoxaemia produced by the pulmonary shunt probably accounted for some of the exercise hyperpnoea, partly by increasing the chemoreceptor drive and partly by encouraging lacticacidaemia. Reduced arterial carbon dioxide tensions and bicarbonate concentrations had lowered the threshold and increased the sensitivity of the ventilatory response to carbon dioxide as measured by rebreathing. Increased chemosensitivity was not thought to have contributed towards the exercise hyperpnoea since arterial carbon dioxide tensions were below the threshold value for ventilatory drive. Exertional dyspnoea in sickle-cell disease was attributed to the combination of hyperpnoea and reduced maximum breathing capacity (MBC) owing to small lung volumes. The fraction of (MBC) used at standard work was therfore abnormally large, and the increased ventilatory effort produced a sensation of breathlessness in some patients (Summary)

Erythrocyte Hb-S concentration: an important factor in the low oxygen affinity of blood in sickle cell anemia

The blood in sickle cell anemia has a very low oxygen affinity and, although 2,3-diphosphoglycerate (2,3-DPG) is increased, there is doubt as to whether this is the only factor responsible. In this study of 15 patients with sickle cell anemia (Hb SS) no correlation was found between oxygen affinity (P 50 at pH 7.13) and 2,3-DPG in fresh venous blood. Whole populations of Hb SS erythrocytes were therefore separated, by an ultracentrifuge technique, into fractions of varying density. The packed red cell column was divided into three fractions; a bottom fraction rich in deformed cells or irreversibly sickled cells (ISC), with a very high mean corpuscular hemoglobin concentration (MCHC); a middle fraction containing cells but free of deformed cells. Oxygen affinity was shifted to the right in all layers (mean P 50 (pH 7.13)ñ1SD: top 46.3ñ2.9 mm Hg; middle 49.8ñ4.9 mm Hg; bottom 61.0ñ5.8mm Hg) compared with normal blood (top 32.1ñ0.7 mm Hg; bottom 30.1ñ0.5 mm Hg). 2,3-DPG was increased in the top fraction, but was low or normal in the bottom fraction (top 21.8ñ3.4 æmol/g Hb; middle 17.7ñ2.2 æmol/g Hb; bottom 13.8ñ3.1 æmol/g Hb; normal whole blood 14.3ñ1.2 æmol/g Hb). The level of 2,3-DPG in top fractions could not account for the degree of right shift of P 50, and in the middle and bottom fractions the even greater right shifts were associated with lower levels of 2,3-DPG had a higher, but still abnormally low, oxygen affinity. A strong relationship was found between oxygen affinity and MCHc. The fractions with the greatest right shift in P 50 had the highest MCHC (top 32.4ñ2.0; middle 36.2ñ3.1; bottom 44.6ñ3.2 g/100 ml, respectively) and the plot of P 50 vs. MCHC showed a positive corelation (r=0.90,P<0.001). The red cell popualtion in sickle cell anemia is not homogeneous but contains cells of widely varying HB F content, 2,3-DPG, but they also have the highest concentration of Hb S. The dense, deformed cell called the ISC is but the end stage in a process of membrane loss and consequent increase in hemoglobin concentration. The P 50 of Hb SS blood is, to a large extent, determined by the presence of these cells (r=0.85, P<0.001). Increased concentration of Hb S in the cell favors deoxygenation and crystallization even at relatively high Poý. Lowered affinity for oxygen appears to be closely associated with Hb S concentration and not with 2,3-DPG content (AU)

The in vivo sickle phenomenon: a reappraisal

Previous studies elsewhere have cast doubt on the in vivo relationship between oxygen saturation and red cell sickling. We have reinvestigated this relationship and find the expected correlation to occur at a variety of in vivo sampling sites. The correlation is apparent within data from single individuals, but may be lost when individual susceptibility to sickle cell formation is overlooked by pooling data from different patients. Samples from the hepatic vein did not usually fit the correlation and the unusual factors at this site are discussed (AU)

Hemoglobin O Arab in four negro families and its interaction with hemoglobin S and hemoglobin C

Hemoglobin O Arab (O2á2 121 Glu leads to Lys) was found in 25 members of four apparently unrelated Negro families in the West Indian island of Jamaica. In each family the propositus had Hb SO disease. Two cases had been mistakenly diagnosed as Hb SC disease. Two persons heterozygous for both Hb C and Hb O Arab were found in these families, and Hb O Arab á thalassemia in one other relative. The clinical course and symptomatology of Hb SO disease is comparable to that in Hb SD(O2á2 121 Glu leads to GluNH2) disease and more severe than Hb SC disease. In vitro mixtures of Hb O Arab and Hb S change from a liquid to a gel phase at total hemoglobin concentrations weaker than those required to gel pure Hb S, whereas mixtures of Hb C require a stronger total hemoglobin concentration before gelling will occur. Oxygen dissociation studies on red cells containing Hb SO show a homozygous sickle-cell anemia and outside the range for subjects with sickle-cell Hb C disease.(AU)