Field exercise tests
Jonathan Dakin, Mark Mottershaw, Elena Kourteli in Making Sense of Lung Function Tests, 2017
Field exercise tests are simple performance measures of endurance or maximal capacity, which may be performed at remote sites without reliance upon lab facilities. The primary measurements made during field exercise tests are the distance walked, arterial oxygen saturation, and the endurance time. The most commonly performed field exercise test is the 6MWT or 6-minute walk distance test. The test is performed between two cones over a course which should be as long as possible, preferably about 30 m. The incremental shuttle walk test is performed between two cones 9 m apart to the accompaniment of a series of bleeps, which are sounded at progressively shorter intervals. The endurance shuttle walk test appears exactly the same as the ISWT, except that the pace of the timing bleeps remains constant throughout the test. All walking tests provide strong prognostic and survival stratification for patients with chronic respiratory disease.
Hematologic responses
Andrew M. Luks, Philip N. Ainslie, Justin S. Lawley, Robert C. Roach, Tatum S. Simonson in Ward, Milledge and West's High Altitude Medicine and Physiology, 2021
Following ascent to high altitude, barometric pressure decreases, thereby leading to a decrease in the arterial partial pressure of oxygen and, as a result, a decrease in hemoglobin-oxygen saturation. This chapter examines the primary factors responsible for changes in plasma volume (PV), which play a large role in the initial increase in hemoglobin concentration, and changes in red cell mass, the factor responsible for the continuing rise in oxygen carrying capacity over the following weeks to months at high altitude. Secretion of antidiuretic hormone (ADH) in response to increased plasma osmolality raises PV by decreasing free water loss in the kidney. Increases in vascular volume caused by hydration cause a fall in plasma osmolality that inhibits ADH secretion. The chapter concludes with consideration of other aspects of hematologic function at high altitude including platelet function, the clotting cascade, and white blood cell function.
Cardiac Ischaemia
T.M. Craft, P.M. Upton in Key Topics In Anaesthesia, 2021
Coronary artery disease is the most common cause of premature death in the United Kingdom (UK). Coronary artery disease is common in the surgical population with up to 30% of perioperative complications and 50% of postoperative deaths being due to a primary cardiac event. Overall about 4% of patients suffer serious perioperative cardiac morbidity following non-cardiac surgery. An atheromatous plaque causes stenosis of a coronary artery lumen sufficient to reduce blood flow to the heart resulting in myocardial ischaemia. Plaque rupture results in a focus for platelet aggregation and the formation of a thrombus. Complete occlusion of the lumen will result in irreversible muscle damage and the patient will sustain a myocardial infarction due to lack of muscle perfusion. Myocardial oxygen supply is determined by arterial oxygen saturation, coronary blood flow and myocardial oxygen extraction. Coronary blood flow depends on the difference between diastolic blood pressure and left ventricular end diastolic pressure (LVEDP).
Changes in Memory Performance, Heart Rate, and Blood Oxygen Saturation Due to 30% Oxygen Administration
Published in International Journal of Neuroscience, 2008
Soon-Cheol Chung, Dae-Woon Lim
This study investigated the effect of 30% oxygen administration on memory cognitive performance, blood oxygen saturation, and heart rate. Ten healthy male and female college students (male: 25.8 ± 0.8 years, female: 24.2 ± 1.9 years) participated in the study. The results of the memory performance analysis reveal that word recall rates were enhanced with 30% oxygen administration compared to 21% oxygen. When 30% oxygen was supplied, blood oxygen saturation was increased and heart rate was decreased compared to that with 21% oxygen administration. Significant positive correlations were found between changes in oxygen saturation and heart rate and memory performance. This result supports the hypothesis that 30% oxygen administration would lead to increases in memory performance.
The Retinal Oxygen Saturation Measured by Dual Wavelength Oximetry in Larger Retinal Vessels is Influenced by the Linear Velocity of the Blood
Published in Current Eye Research, 2019
Signe Krejberg Jeppesen, Toke Bek
Purpose: Dual wavelength retinal oximetry allows the quantification of oxygen saturation in the larger retinal vessels. However, the technique might be refined further by identifying factors that are responsible for the different oxygen saturations in first order arterioles from the same eye shortly after their branching from the central retinal artery. The purpose of the present study is to investigate whether these factors involve rheological characteristics in the studied vessels. Materials and Methods: In fourty healthy persons the oxygen saturation was measured by dual wavelength oximetry and the blood flow by Doppler OCT in the upper and lower temporal and nasal arterioles and venules shortly after their branching from the central retinal artery and vein. The relationship of the measured oxygen saturations with age, vessel diameter, and blood linear velocity were assessed. Results: The measured oxygen saturations were (mean± SD) 97.8% ± 6.4% in the arterioles and 60.2% ± 8.8% in the venules. For both the arterioles and the venules the measured oxygen saturation (Sm) correlated significantly with the linear velocity (v) of the blood in mm/s (Sm = 101.6–0.28*v, p
Abnormal fetal heart rate patterns during the active phase of labor: the value of fetal oxygen saturation
Published in The Journal of Maternal-Fetal & Neonatal Medicine, 2002
N. Vitoratos, E. Salamalekis, J. Saloum, E. Makrakis, G. Creatsas
Objective: To determine the predictive value of intrapartum fetal oxygen saturation (SO2) for prediction of an umbilical artery pH less than 7.15 at birth in labors complicated by abnormal fetal heart rate traces. Study design: Eighty-five primigravidas in spontaneous labor complicated by abnormal fetal heart rate traces underwent fetal SO2 monitoring using the fetal pulse oximetry technique. Cases with an SO2 of < 30% were delivered by Cesarean section. Umbilical artery pH was measured at birth in all women. Results: With the value set of 30% as the cut-off point of fetal oxygen saturation, the positive predictive value for umbilical artery pH of < 7.15 was 61.5% and the negative predictive value was 95.8%, with a sensitivity of 72% and a specificity of 93%. Conclusions: Fetal pulse oximetry is a promising technique for assessment of fetal well-being during labor and may decrease the number of unnecessary Cesarean sections.