The Lifebox oximeter is supplied for US $250 and supported by international donations.The pulse oximeter also has the potential to act as a diagnostic device in respiratory [8] and cardiac diseases [9], as well as systemic diseases such as pre-eclampsia and sepsis that affect multiple body systems including the lungs [10,11].A pulse oximeter works by shining light from two Light Emitting Diodes (LEDs) at different wavelengths, typically 660 nm (visible red) and 910 nm (near infrared), through the arterial blood of a finger or an ear and detecting the transmitted light with a photodiode. Hemoglobin molecules with and without oxygen attached have different optical absorption characteristics at these wavelengths, and the oxygen saturation, SpO2, can be deduced from the ratio of the transmitted light at the two wavelengths.

SpO2 is the percentage of hemoglobin molecules that have oxygen attached compared to those that are not bound to oxygen.A healthy individual has an oxygen saturation level above 95%. A decrease below 95% is a strong indicator of an oxygen delivery or consumption imbalance, for example caused by impeded gas exchange in the lungs resulting from severe respiratory diseases like pneumonia and asthma [12�C15] or due to an increase in consumption as well as impeded gas exchange seen in other systemic inflammatory and infectious diseases [10]. In this way, pulse oximetry can for example be used to differentiate severe pneumonia from the common cold or other mild infections.Pulse oximetry therefore has the potential of being a powerful tool in the prevention of childhood mortality in low- and middle-income countries.

Unfortunately, these areas of the world remain largely without access to the technology. Part of the problem is that conventional pulse oximeters are expensive and bulky devices intended for use in modern hospitals, and are unsuited for use in resource low settings [16�C18].In order to make pulse oximetry more available we have Dacomitinib previously developed a so-called Phone Oximeter [19], that interfaces a commercial microcontroller-based pulse oximeter module with a smartphone. Phones are widely available even in the most remote areas [20], and have become a cornerstone in developing economies and the livelihood of people everywhere. For example, Africa has seen a tremendous growth in mobile phone usage in recent years, with 648.

4 million mobile phone subscriptions in 2011, more than in the United States or the European Union [21]. Furthermore, the smartphone portion of the mobile market is set to surpass that of basic and feature phones, driven mainly by the growth in the emerging markets [22].Usability studies of the Phone Oximeter prototype previously undertaken both in Canada and Uganda gave overall usability scores of 82% and 78% respectively, indicative that a phone can be a functional oximeter interface [23].