Apparatus and method for estimating respiration rate

Monitoring apparatus for measuring the respiratory rate of a subject, the monitoring apparatus comprising an upper arm unit configured for attachment to a subject's upper arm,

• the upper arm unit comprising at least one movement sensor and a photoplethysmograph (PPG) configured to a monitor blood volume within the subject's upper arm while the upper arm unit is worn on the subject's upper arm,
• at least one processor programmed to process both the output of the at least one movement sensor and the output of the photoplethysmograph to thereby calculate and output an estimate of the rate of respiration of the subject,
• (a) a first estimate of the rate of respiration calculated by determining the frequency of a respiratory cycle induced variation in the output of the photoplethysmograph;
• or
• (b) a second estimate of the rate of respiration calculated by determining the frequency of a respiratory cycle induced variation in the output of the at least one movement sensor, and
• wherein the second estimate of the rate of respiration is the estimated respiratory rate induced variation in the output of the at least one movement sensor within the upper arm unit.