Persons with sleep disordered breathing (SDB) may, or may not, recognize that they have symptoms of SDB, and/or that they may be at-risk of, or suffering certain health problems associated with SDB, including death. The disclosed Energy Conversion Monitor (ECM) sensor, when embodied, for example, in a wearable upper-armband format, has been demonstrated to be more sensitive and responsive than pulse oximetry monitoring of blood oxygen saturation as an indication of hypoxic stress induced by SDB, and is compatible with: (1) inclusion in sleep laboratory polysomnograph (PSG) testing instrumentation, (2) home-based diagnostic testing for SDB, (3) control of home-use airway therapy devices, (4) continuous remote surveillance and refinement of airway therapy, and (5) spot-check and continuous surveillance of sleep quality in the general population. The disclosed ECM also provides new measurements of physiologic stress during and following exercise. When applied during initial care of premature newborn infants, it offers improved therapeutic guidance during their transition from their limited in utero oxygen supply conditions, to the increased oxygen availability from breathing air. When applied during resuscitation of persons suffering from hypoxia and during reperfusion of ischemic tissue, such as during treatment of ischemic stroke, or ischemic heart attack, the ECM sensor can provide objective guidance regarding the safe and effective resupply of oxygen to the hypoxia-adapted tissue to help reduce or prevent microvascular occlusion and cellular injury. As a continuously worn physiologic surveillance monitor, the ECM offers the potential of early detection of sepsis. With the elderly and infirm, it offers a convenient and comfortable means of continuously assessing variations in status while awake and asleep.