The effect of normobaric hyperoxia on cardiac index in healthy awake volunteers

Abstract

SummaryWe developed a screening questionnaire to be used by nurses to decide which patients should see an anaesthetist for further evaluation before the day of surgery. Our objective was to measure the accuracy of responses to the questionnaire. Agreement between questionnaire responses and the anaesthetist's assessment was assessed. For questions with a prevalence of 5 to 95%, the Kappa coefficient was used; percentage agreement was used for all other questions. Criterion validity was excellent ⁄ good for all questions with a prevalence between 5 and 95%, except for the question 'Do you have kidney disease?' For questions with prevalence < 5%, all demonstrated adequate criterion validity except the questions 'Has anyone in your family had a problem following an anaesthetic?' and 'If you have been put to sleep for an operation were there any anaesthetic problems?' Therefore, it is reasonable for nurses to use this questionnaire to determine which patients an anaesthetist should see before the day of surgery.Keywords Anaesthesia; pre-operative, assessment, questionnaire. Recent advances in anaesthetic and surgical practice have facilitated the growth of 'fast track' surgery [1, 2]. Careful outpatient assessment is fundamental to the success of this type of surgery and the Association of Anaesthetists of Great Britain and Ireland now recommends assessment at a pre-operative assessment (POA) clinic [3].The provision of a pre-operative screening and assessment service at POA clinics supplies background information about patient's general medical status and fitness for anaesthesia. POA clinics improve patient care by allowing careful pre-operative evaluation and optimisation of coexisting disease [4], reduce costs [5, 6], improve efficiency [7], and lower surgical cancellation rates [8, 9].In POA clinics, nurses increasingly carry out preoperative screening [10]. Although they are not qualified to decide if a patient is fit for anaesthesia, they play a valuable role in identifying patients who are at risk and require further evaluation and optimisation before the day of surgery [11]. Nurses screen patients for risk factors for fitness for anaesthesia and surgery using questionnaires [12]. These can be self-administered by the patient [9], or used during structured interviews [13], or computer programs [14]. Although many locally developed questionnaires exist, few have been formally assessed.We have developed a multi-tiered screening questionnaire to be used by nurses to decide which patients should be seen at a POA clinic by an anaesthetist for further evaluation and optimisation. Using Delphi consensus methods, we have already evaluated content validity for each question [15] to ensure that the questions are relevant to concept being measured.Our objective was to perform item analysis of the screening questionnaire and measure criterion validity [16], that is, is it a true measure of what it is designed to measure?By testing individual questions beyond basic content validity, we were able to put them together in a...

A Pilot Study of Normobaric Oxygen Therapy in Acute Ischemic Stroke

“…27 Decades of research have emphasized the harmful tissue effects of oxygen free radical injury. 28 Our preclinical studies indicate that hyperoxia's benefit in reducing infarct volume outweighs the risk of enhanced free radical injury.…”

Effects of normobaric hyperoxia on haemodynamic parameters of healthy full‐term parturients

“…It has been demonstrated that heart rate and therefore cardiac output are reduced; in parallel, systemic vascular resistance increases by an equal amount. Overall, blood pressure remains unchanged [10,11]. It is unclear whether the reduction in heart rate and cardiac output are the primary effect or occur secondary to increases of systemic vascular resistance.…”

“…Lin's concordance correlation r-value was 0.99 with a bias of 0.07 l.min .m )2 ; there was no significant difference between transthoracic bio-impedance and thermodilution standard deviations. In addition, the fact that, when measured with transthoracic bio-impedance, the cardiovascular changes in response to hyperoxia [11] are similar in magnitude to those demonstrated using a gold standard technique [10] adds to its validity. It seems to be a useful non-invasive tool to study changes in cardiac output.…”

“…Sample size was calculated based on previously published data [10,11]. To detect a clinically significant difference in cardiac output of 0.56 (standard deviation 0.53 l.min )1 ), the sample size required was 12, assuming a power of 0.90 and a of 0.05.…”

The role of regional cerebral oxygen saturation on adjustment of fraction of inspired oxygen during coronary artery bypass graft surgery

“…Animal studies have shown that oxygen reduces the heart rate and cardiac output and increases systemic vascular resistance, [1,2] and this has been confirmed in patients with congestive heart failure in whom the effect is more pronounced. [3] The adverse influences of hyperoxemia (PaO 2 >180 mmHg) on red blood cells and tissue oxygenation during CPB along with subsequent perioperative complications and morbidity have been reported. [4][5][6] Although CPB has been used for more than half a century, there is still no consensus regarding the ideal levels of fraction of inspired oxygen (FiO 2 ) and PaO 2 .…”