How can a more complete description of oxygen transport be achieved?
Thus, a more complete description of oxygen transport can be achieved by considering simultaneous chemical reactions between oxygen, hemoglobin, carbon monoxide, carbon dioxide, hydrogen ions, and intermediate compounds in the corresponding reactions.
What is the equation for oxygen transport in tissue?
3 Oxygen in the tissue is not bound to a carrier, e.g., to myoglobin in muscle. Under these assumptions, the equation governing oxygen transport in the tissue can be written in the form αt∂Pt∂t=K[1r∂∂rr∂Pt∂r+∂2Pt∂z2]-M (69)
How can we optimise the delivery of oxygen to the body?
Oxygen delivery would be optimised by maintaining cardiac output and haemoglobin concentration and ensuring oxygen is released to tissues by manipulating the oxygen-haemoglobin dissociation curve.
Does oxygen transport occur in the pre and postcapillary microcirculation?
There is experimental evidence that significant precapillary loss of oxygen occurs in the cerebral circulation. In order to include transport in the pre- and postcapillary microcirculation, Sharan et al.167modified the compartmental model of Roth and Wade147and applied it to oxygen transport in the brain.
How does cellular tolerance to hypoxia affect the survival of tissues?
Cellular tolerance to hypoxia may involve “hibernation” strategies which reduce metabolic rate, increased extraction of oxygen from surrounding tissues, and adaptations of enzymes to allow metabolism at low partial pressures of oxygen. Anaerobic energy production is important to the survival of some tissues despite its inefficiency. Skeletal muscle increases glucose uptake by 600% during hypoxia and bladder smooth muscle can generate up to 60% of total energy requirement by anaerobic glycolysis. In cardiac cells anaerobic glucose use protects the integrity of cell membranes by maintaining energy dependent potassium channels.
What is the extraction ratio of oxygen?
In healthy resting adults the overall extraction ratio of oxygen from capillary blood is about 25% but may increase to 70-80% during maximal exercise in well trained athletes. Although the oxygen content of blood is linearly related to saturation, the relation between partial pressure of oxygen (Pao2) and saturation is non-linear. Various physicochemical factors affect the position of this sigmoid relation, which is defined by the oxygen concentration at which 50% of the haemoglobin is saturated (P50)—normally 3.5 kPa. A shift in the capillary oxygen-haemoglobin dissociation curve to the right enhances release of oxygen to tissues and improves oxygen availability. Provided that Pao2does not fall much below 8 kPa the loss of oxygen uptake in the lungs is small but the increased release in the tissues is significant and the net effect is beneficial, increasing venous and tissue oxygen concentrations.
What causes tissue hypoxia?
Rate of use of oxygen by cells. During critical illness tissue hypoxia is often caused by capillary microthrombosis after endothelial damage and neutrophil activation rather than by arterial hypoxaemia. Manipulation of the coagulation system using low molecular weight heparins may reduce microthrombosis.
Why does tissue hypoxia occur?
In many critically ill patients tissue hypoxia is due to disordered regional distribution of blood flow both between and within organs.
Why is tissue oedema more severe than cellular oxygen?
Thus, tissue oedema due to increased vascular permeability or excessive fluid loading may cause impaired oxygen diffusion and cellular hypoxia, particularly in conditions associated with arterial hypoxaemia. In such cases careful fluid balance may prevent tissue hypoxia.
How does skeletal muscle increase glucose uptake?
Skeletal muscle increases glucose uptake by 600% during hypoxia and bladder smooth muscle can generate up to 60% of total energy requirement by anaerobic glycolysis. In cardiac cells anaerobic glucose use protects the integrity of cell membranes by maintaining energy dependent potassium channels.
What does the concentration of inorganic phosphates in red cells affect?
The concentration of inorganic phosphates in red cells, notably 2,3-diphosphoglycerate, affects the structure of the haemoglobin molecule and its affinity for oxygen. Reduced concentrations (as found in old blood from blood banks) reduce the P50.
Abstract
ReBound continuous shortwave diathermy (ReGear Life Sciences, Inc., Pittsburgh, PA) is designed to heat deep tissues via anatomically designed garments. Research shows MegaPulse II pulsed shortwave diathermy (EMS Physio Ltd., Oxfordshire, England) can vigorously heat deep tissues. There is limited research on ReBound's heating capabilities.
Introduction
Diathermy is a therapeutic modality and literally means “to heat through.” 1 Once an obsolete therapeutic modality, diathermy is making a comeback into the clinical setting.
Methods
A repeated-measures counterbalanced (cross-over) design was used where each participant received both treatment conditions: MegaPulse II pulsed shortwave diathermy (EMS Physio Ltd., Oxfordshire, England) and ReBound continuous shortwave diathermy.
Results
There was no significant treatment-by-time interaction during the heating period (F 2,35 = 1.40, P = .221), but there was a significant treatment effect during the heating period (F 1,17 = 9.04, P = .008), with MegaPulse II causing a statistically significant greater increase in intramuscular tissue with an average of 3.47 ± 0.92°C over the 30-minute treatment period compared to the ReBound's average increase of 3.08 ± 1.19°C over the 45-minute treatment period.
Discussion
The purpose of our study was to compare the deep heating of two modalities: Megapulse II pulsed shortwave diathermy and ReBound continuous shortwave diathermy. We found that the MegaPulse II produced the greatest temperature increase. In terms of intramuscular temperature decay, there was no difference between the MegaPulse II and the ReBound.
Implications for Clinical Practice
MegaPulse II pulsed shortwave diathermy is an effective heating modality to vigorously heat muscles at a depth of 3 cm. There is an approximately 15-minute stretching window clinicians should use immediately following a 30-minute MegaPulse II treatment, during which the tissues are in an ideal state of extensibility for stretching and elongation.
Conclusion
Due to the fixed power output of the ReBound, vigorous heating in muscle tissue 3 cm deep may not be possible. Future research should focus on different areas of the body and structures most often heated in clinical practice.
