Pusle-oxymeter.....little gizmo placed on finger that instantly shows pulse-rate and blood-oxygen saturation level. VERY useful for management of elderly with pulmonary issues, chronic or acute.
These have been available for more than a decade but used to cost hundreds of dollars. Due to recent troubles here, I needed one and was pleased to find there are MANY available for 15-40 dollars. Managing current situation (supplemental oxygen required) without it would have been very difficult. Little, cheap device takes all the mystery away and makes competent management much less stressful.
Highly recommended. Google "pulse oxymeter" many available.