A three species model to simulate application of hyperbaric oxygen therapy to chronic wounds

Chronic wounds are a significant socioeconomic problem for governments worldwide. Approximately 15% of people who suffer from diabetes will experience a lower-limb ulcer at some stage of their lives, and 24% of these wounds will ultimately result in amputation of the lower limb. Hyperbaric Oxygen Therapy (HBOT) has been shown to aid the healing of chronic wounds; however, the causal reasons for the improved healing remain unclear and hence current HBOT protocols remain empirical. Here we develop a three-species mathematical model of wound healing that is used to simulate the application of hyperbaric oxygen therapy in the treatment of wounds. Based on our modelling, we predict that intermittent HBOT will assist chronic wound healing while normobaric oxygen is ineffective in treating such wounds. Furthermore, treatment should continue until healing is complete, and HBOT will not stimulate healing under all circumstances, leading us to conclude that finding the right protocol for an individual patient is crucial if HBOT is to be effective. We provide constraints that depend on the model parameters for the range of HBOT protocols that will stimulate healing. More specifically, we predict that patients with a poor arterial supply of oxygen, high consumption of oxygen by the wound tissue, chronically hypoxic wounds, and/or a dysfunctional endothelial cell response to oxygen are at risk of nonresponsiveness to HBOT. The work of this paper can, in some way, highlight which patients are most likely to respond well to HBOT (for example, those with a good arterial supply), and thus has the potential to assist in improving both the success rate and hence the costeffectiveness of this therapy.

Fear of oxygen therapy for children in Malawi

BACKGROUND: Although pneumonia is a common cause of death in children in Malawi, healthcare staff frequently encounter patients or carers who refuse oxygen therapy. This qualitative study documents factors that influence acceptance or refusal of oxygen therapy for children in Malawi.

METHODS: Nine group interviews involving 86 participants were held in community and hospital settings in rural and urban Malawi. Eleven in-depth interviews of healthcare staff providing oxygen were held in a central hospital. Thematic analysis of transcripts of the audio recordings was carried out to identify recurring themes.

RESULTS: Similar ideas were identified in the group interviews and in-depth staff interviews. Past experiences of oxygen use (direct and indirect, positive and negative) had a strong influence on views of oxygen. A recurrent theme was fear of oxygen, often due to a perceived association between death and recent oxygen use. Fears were intensified by a lack of familiarity with equipment used to deliver oxygen, distrust of medical staff and concerns about cost of oxygen.

CONCLUSIONS: This study identifies reasons for refusal of oxygen therapy for children in a low-income country. Findings from the study suggest that training of healthcare staff to address fears of parents, and information, education and communication (IEC) approaches that improve public understanding of oxygen and provide positive examples of its use are likely to be helpful in improving uptake of oxygen therapy in Malawi.

Effects of hyperbaric oxygen therapy on facial nerve regeneration

Conclusion. Hyperbaric oxygen treatment (HBOT) promoted an increase of the mean axonal diameter in the group evaluated 2 weeks after lesion induction, which suggests a more advanced regeneration process. However, the number of myelin nerve fibers of the facial nerve of the rabbits was similar when compared to the control and treatment groups, in both evaluation periods. Objective. To evaluate the effect of HBOT on the histological pattern of the facial nerve in rabbits exposed to a nerve crush injury. Materials and methods. Twenty rabbits were exposed to facial nerve crush injury. Ten rabbits received HBOT, 10 rabbits comprised the control group. The rabbits were sacrificed 2 and 4 weeks after the trauma. Qualitative morphological analysis, measurement of the external axonal diameters and myelin fiber count were carried out in an area of 185 000 mu m(2). Results. There was an increase in the area of the axons and thicker myelin in the 2 weeks treatment group in comparison with the control group. The mean diameter of the axons was of 2.34 mu m in the control group and of 2.81 mu m in the HBOT group, with statistically significant differences. The 2 week control group had a mean number of myelin fibers of 186 +/- 5.2664, and the HBOT group had a mean number of 2026.3 +/- 302; this was not statistically significant. The 4 week control group presented a mean of 2495.1 +/- 479 fibers and the HBOT group presented a mean of 2359.9 +/- 473; this was not statistically significant.

Low-flow oxygen therapy: selecting the right device

The authors provide and overview of oxygen therapy principles, describing the indications and care requirements of three low flow oxygen therapy devices and providing an algorithm for managing refractory hypoxaemia.

Use of medical orders in acute care oxygen therapy

The life of every living organism is sustained by the presence of oxygen and the acute deprivation of oxygen will, therefore, result in hypoxia and ultimately death. Although oxygen is normally present in the air, higher concentrations are required to treat many disease processes. Oxygen is therefore considered to be a drug requiring a medical prescription and is subject to any law that covers its use and prescription. Administration is typically authorized by a physician following legal written instructions to a qualified nurse. This standard procedure helps prevent incidence of misuse or oxygen deprivation which could worsen the patients hypoxia and ultimate outcome. Delaying the administration of oxygen until a written medical prescription is obtained could also have the same effect. Clearly, defined protocols should exist to allow for the legal administration of oxygen by nurses without a physicians order because any delay in administering oxygen to patients can very well lead to their death.

Evaluation of nasopharyngeal oxygen, nasal prongs and facemask oxygen therapy devices in adult patients: a randomised crossover trial

Nasopharyngeal oxygen (NPO) therapy may overcome some of the difficulties associated with nasal prongs and facemask oxygen delivery devices. In response to a lack of published studies of NPO therapy in adults, we conducted a prospective randomised crossover trial to compare the effectiveness of NPO, nasal prongs (NP) and facemasks (FM) when used in an adult population (n=37) from the intensive care unit and general hospital wards. We measured oxygen saturation (Sp[O.sub.2]) using pulse oximetry, oxygen flow (litres per minute), respiration rate (per minute) and comfort using a horizontal visual analogue scale. All three devices were effective in maintaining a Sp[O.sub.2] of [greater than or equal to]95% (NP 97.0[+ or -]1.9, NPO 97.7[+ or -]1.7, FM 98.8[+ or -]1.3%). NPO therapy consumed less oxygen than NP and FM therapy (NP 2.6[+ or -]1.0, NPO 2.2[+ or -]0.9, FM 6.1[+ or -]0.4 l/min, P <0.001). There was no significant difference in patients' respiratory rates (NP 19.9[+ or -]3.2, NPO 19.9[+ or -]3.0, FM 19.8[+ or -]3.1 per minute, P=0.491). In terms of comfort, patients rated NP higher than NPO and FM using a horizontal visual analogue scale (100 mm=most comfortable) (NP 65.5[+ or -]14.3, NPO 62.8[+ or -]19.4, FM 49.4[+ or -]21.4 mm, P <0.001). We conclude that for adult patients, nasal prongs and nasopharyngeal oxygen therapy consume less oxygen and provide greater comfort than facemasks while still maintaining Sp[O.sub.2] [greater than or equal to]95%.

Patients and nurses' perspective on oxygen therapy : a qualitative study

Aim. This paper is a report of a study to describe patients' and nurses' perspectives on oxygen therapy.
Background. Failure to correct significant hypoxaemia may result in cardiac arrest, need for mechanical ventilation or death. Nurses frequently make clinical decisions about the selection and management of low-flow oxygen therapy devices. Better understanding of patients' and nurses' experiences of oxygen therapy could inform clinical decisions about oxygen administration using low-flow devices.
Methods. Face-to-face interviews with a convenience sample of 37 adult patients (17 cardio-thoracic: 20 medical surgical) and 25 intensive care unit nurses were conducted from February 2007 to September 2007. Interviews were audio-taped, transcribed verbatim and then analysed using a thematic analysis approach.
Findings. The patients identified three key factors that underpinned their compliance with oxygen therapy: (i) device comfort; (ii) ability to maintain activities of daily living; and (iii) therapeutic effect. The nurses identified factors, such as: (i) therapeutic effect, (ii) issues associated with compliance, (iii) strategies to optimize compliance, (iv) familiarity with device, (v) triggers for changing oxygen therapy devices, as being key to the effective management of oxygen therapy.
Conclusion. Differences between the patients' and nurses' perspective of oxygen therapy illustrate the variety of factors that impact on effective oxygen administration. Further research should seek to provide a further in-depth understanding of the current oxygen administration practices of nurses and the patient factors that enhance or hinder effectiveness of oxygen therapy. Detailed information about nurse and patient factors that influence oxygen therapy will inform a sound evidence base for nurses' oxygen administration decisions.

Oxygen therapy management for patients at risk of respiratory dysfunction

Oxygen therapy is a major intervention used to manage respiratory dysfunction. Research findings revealed a need for health care professionals to review oxygen device selection in specific clinical settings, the importance of involving patients in their care decisions and to document appropriately care that is provided associated with oxygen therapy.

Potentially modifiable predictors of mortality in patients treated with long-term oxygen therapy

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