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Biomedical subjects

P K Andersen

Publications and source records attributed to P K Andersen.

At least 127 records · Page 7Linked to original sources
PubMed1985

A Cox regression model for the relative mortality and its application to diabetes mellitus survival data.

A Cox-type regression model for the ratio between the mortality in a cohort and that in a reference population is introduced. By means of the model it is possible to include in the survival analysis both individual (possibly time-dependent) characteristics for the study cohort and changing trends in the mortality in the reference population. This is particularly relevant in long-term follow-up studies where there may be considerable changes in the mortality in the reference population. Estimation procedures in the model are discussed and large-sample properties of the estimators are outlined. The model is applied to the analysis of two sets of data concerning the survival among insulin-dependent diabetics in Denmark.

Adolescent↗
PubMed1984

Acid-base interactions with noradrenaline-induced contractile response of the rabbit isolated aorta.

The effect of acidosis and alkalosis on vascular smooth muscle contractions evoked by noradrenaline was studied. Helical strips of rabbit aorta were mounted for isometric tension recording. Acidosis (pH 7.24-6.51) was obtained by either increasing the PCO2 (hypercapnic) and/or lowering the HCO3-concentration (hypobicarbonatic). Acidosis shifted the noradrenaline concentration-response curve to the right in a competitive manner. The maximal developed tension was unchanged at pH 7.24-6.90 and decreased by 30% at pH 6.51. Alkalosis (pH 7.61-8.04) did not alter noradrenaline-evoked contractions. The results suggest that hydrogen ions during acidosis (pH less than 7.40) but not during alkalosis (pH greater than 7.40) exert alpha-adrenoceptor blocking properties.

Acid-Base Equilibrium↗
PubMed1984

Distribution of expiratory gas and rebreathing in a T-piece modification combined with a PEEP valve.

T-piece modifications with PEEP valves are often used in weaning from mechanical ventilation or for intubated patients not requiring ventilatory support. Distribution of expiratory gas and the extent of rebreathing in a T-piece modified with an inspiratory reservoir (ICR) and with a PEEP valve were studied in a model with various fresh gas flows (FGF), tidal volumes and frequencies at three valve settings: 0 cmH2O (ZEEP) and PEEP of 5 and 10 cmH2O (0.490-0.981 kPa). Two types of distribution of expiratory gas were delineated: type one with expiratory gas in the inspiratory limb (IL) and a high ratio of the maximum CO2 content and corresponding end-expiratory CO2 concentration in the expiratory limb (EL) (FmaxCO2/FECO2) and a type 2 with no detectable alveolar gas in the IL and a low ratio of FmaxCO2/FECO2. The use of PEEP did not increase the amount of alveolar gas in the system, and no increase occurred in the end-expiratory CO2 concentration. The investigated system is in fact a Mapleson A system. The ratio of FGF to minute ventilation just preventing rebreathing during spontaneous ventilation is approximately 1, in contrast to 3 in other modifications. These advantages minimize the risk of rebreathing, even when the minute ventilation rises to that of the fresh gas flow. The T-system with a compliant inspiratory reservoir and a PEEP valve can, in most clinical weaning situations, satisfy the inspiratory peak flow of different respiratory patterns with a standard FGF of 15 l X min-1.

Carbon Dioxide↗
PubMed1983

Epidemiological studies of diabetes mellitus in Denmark: 3. Clinical characteristics and incidence of diabetes among males aged 0 to 19 years.

This study presents the clinical-epidemiological analysis of data from 769 individuals, representing greater than 95% of all cases of diabetes mellitus diagnosed during the first 20 years of life among the Danish male birth cohorts 1949-1956 inclusive. It is concluded that except for a very few, all cases of diabetes developing during the first 20 years of life are insulin-dependent with a duration of symptoms less than 2 months before diagnosis in greater than 75% of the cases. The cases were evenly distributed within Denmark at the time of birth as well as of diagnosis, and greater than 98% were admitted to hospital at diagnosis. A relatively higher proportion of cases diagnosed during autumn and winter periods was found, but was not statistically significant. Incidence was analysed in a regression model with age and calendar time as variables; the variation of age at onset was similar to previous studies with a peak at pre-school age and at puberty. Contrary to previous Danish analyses, we found a significant calendar time variation with steadily increasing age-specific incidences from the beginning of 1950s until an apparent maximum in mid-1970s.

Adolescent↗
PubMed1983

Short-term physical training in bronchial asthma.

The effect of two types of physical training on patients with perennial asthma were compared in a blind, controlled, randomized study. Eleven of 27 adults with asthma performed a physical training programme which did not change their oxygen consumption (control group). The remaining 16 asthmatics performed a physical training programme which improved their maximal oxygen consumption (training group). Both of the training programmes were performed for 1 hour, twice a week during a period of 2 months. No complications were reported during the performance of the training programmes. The doses of all medicines apart from beta 2-agonist aerosol were unchanged during the training period. The patients inhaled beta 2-agonist aerosol if their peak expiratory flow (PEF) was less than 60% of their maximal PEF. The training group decreased their use of aerosol from an average of 4.94 puffs per day to 3.41 puffs per day (P less than 0.05). The control group did not change their use of beta 2-agonist aerosol significantly. It is concluded that physical exercise which improves the maximal oxygen consumption decreases the use of beta 2-agonist spray and that heavy exercise is well tolerated by asthmatics.

Adrenergic beta-Agonists↗
PubMed1983

Distribution of expiratory gas and rebreathing in T-piece modifications used in weaning.

The simple T-piece is frequently used as a weaning system during respirator treatment. It is modified with an expiratory non-compliant reservoir (EnCR), an inspiratory compliant reservoir (ICR) and/or an expiratory one-way valve. The distribution of expiratory gases and rebreathing were studied in a model set-up in the corresponding systems at different fresh gas flows (FGF) and tidal volumes (VT). An EnCR produces no change, whereas an ICR causes the expiratory gas to flow into the inspiratory limb, an effect which is intensified by the presence of an expiratory valve. With a falling FGF and a rising VT, increasing amounts of expiratory gas are found in the inspiratory limb in the modifications with an ICR. However, this gives rise to rebreathing in the valve modification with a low FGF and high VT. The modification of the T-piece with an ICR but without a one-way valve is advantageous, as this system combines only slight dilution via the expiratory limb and a minimal risk of rebreathing.

Breath Tests↗
PubMed1982

Survival with malignant melanoma: a regression analysis of prognostic factors.

A Cox's regression model for survival data has been applied to investigate which of the many clinical and histopathologic parameters have a significant influence on the survival probability of the patients with primary malignant melanoma. The thicker the tumor and the deeper the invasion, the poorer the prognosis. Localization of the tumor on the mucous membranes, ulceration, and presence of epithelioid cells are all bad prognostic signs. The stronger the rim of inflammatory cell infiltrate, the better the prognosis for the patient. Females have better prognosis than males and prognosis aggravate with age. Using these parameters it is possible to make a prognosis forecast for the individual patient. Two patients, one with a favorable set of parameters and another with an unfavorable set, are described.

Follow-Up Studies↗
PubMed1982

Catabolism of haemoglobin-haptoglobin complexes in haemolytic uraemia-like syndromes of different etiologies.

The catabolism of haemoglobin-haptoglobin complexes was studied in four patients with increased vascular haemolysis as part of acute or subacute haemolytic uraemic syndromes. The apparent volumic substance elimination rates for haemoglobin (Fe) bound to haptoglobin in plasma were 1.1 mumol/h/l and 2.9 mumol/h/l in two patients suffering from sublimate and hydrochloric acid poisoning, respectively. This is estimated to correspond to a normal catabolism, when the increased haptoglobin synthesis is taken into account. In the other two patients suffering from serum-sickness there was reduced clearance and thereby an accumulation of haemoglobin-haptoglobin complexes in plasma during penicillin administration. When the offending drug was withdrawn the plasma concentration of haemoglobin bound to haptoglobin remained high for about three days and then fell rapidly (approximately with 3.8 mumol/l/h and 1.9 mumol/l/h). Thus, also in these patients the clearance capacity could be normalized after discontinuation of the drug.

Adult↗
PubMed1981

Admixture of atmospheric air in the T-piece used as a weaning system.

Ayre's T-piece may be used for intubated, non-anaesthetized patients requiring an oxygen supplement or humidified gas mixtures. The system has the disadvantage that atmospheric air (VAD) enters through the expiratory leg when the inspiratory flow and therapeutic gas flow (TGF) are not equal. This admixture can be reduced in the simple T-piece by the addition of either a compliant inspiratory reservoir, or a compliant inspiratory reservoir and an expiratory unidirectional valve. These three systems have been studied in a model investigation using different tidal volumes (VT), respiratory frequencies, and therapeutic gas flow. VAD was measured using a pneumotachograph and the inspiratory tidal volume was measured with a Wright Respiratory Monitor. The ratio VAD/VT was employed as an expression of the admixture of atmospheric air during inspiration. The introduction of a compliant inspiratory reservoir to the simple T-piece results under all conditions in a considerable reduction in VAD/VT. A further reduction was obtained by introducing an expiratory unidirectional valve into the system - however, with the result that the previously open system is turned into a closed system. When selecting a weaning system, the risk to the patient of the discontinuation of the gas flow should therefore be weighed against the advantages obtained by a reduction of the admixture.

Intubation↗
PubMed1981

Control of carbon dioxide in modified Mapleson A and D (Hafnia) anaesthetic systems. An experimental model.

The effects of varying ventilations (VE) and fresh gas flows (FGF) on end-expiratory CO2 (FECO2) levels were investigated in an experimental model lung, employing the Hafnia modification of the Mapleson A and D anaesthetic systems during CO2-absorption and CO2-wash-out (rebreathing). Identical results were found in both systems: FECO2 was constant and independent of FGF with CO2-absorption and constant VE, whereas rebreathing resulted in increasing FECO2 levels as FGF was decreased. As control of FECO2 in the rebreathing systems by regulating FGF could only take place within FECO2 levels higher than that determined by VE at complete CO2-absorption, e.g. for the Hafnia A and D rebreathing systems, control of FGF necessitates relative hyperventilation. FECO2 with constant FGF decreased with increasing VE during CO2-absorption, as well as during rebreathing, although this decrease was less in the rebreathing systems. Thus a decrease in FECO2 with rising VE can be avoided and hypocapnia prevented. The results agree with those obtained in clinical studies.

Anesthesiology↗
PubMed1981

Carbon dioxide tensions in manually ventilated, prone patients.

The distribution of arterial carbon dioxide tensions (PaCO2) in 288 anaesthetized, healthy patients in the prone position was investigated during non-monitored manual ventilation. Four equal groups of 72 patients were compared employing a conventional anaesthetic system with and without CO2-absorption and a modified Mapleson D rebreathing system using high and low fresh gas flows. No fundamental difference between the Mapleson D system and the circle system without CO2-absorption could be demonstrated. With the Mapleson D system a high fresh gas flow resulted in a loss of rebreathing characteristics, the scatter of PaCO2-values then approaching that of a conventional circle system with CO2-absorption. The results demonstrate that during manual ventilation a CO2-absorption results in unpredictable levels of PaCO2 with unacceptably wide ranges. On the other hand, prevention of hypocapnia could be obtained with the rebreathing systems using a low fresh gas flow. Hypercapnia was modest and similar in all groups, PaCO2 never exceeding 7.3 kPa. In terms of PaCO2-levels it seems, compared to recent literature, of no importance whether the patient is prone or supine or whether or not ventilation is monitored, performed by hand or by means of anaesthetic ventilators. Accurate levels of PaCO2 can probably only be obtained by frequent analyses of PaCO2, or monitoring of the end-tidal CO2 concentration.

Adult↗