Abstract Introduction The SleepImage is an HSAT device (sHSAT) that uses photoplethysmography and oxygen saturation data to generate an apnea hypopnea index (AHI). This sHSAT has been FDA cleared as a software-as-a-medical-device for use in children 2 years and older for diagnosing obstructive sleep apnea (OSA). To our knowledge this sHSAT has not been tested on children concurrent with the gold standard polysomnography (PSG). Methods This study evaluated 50 children 2-6 years of age with tonsillar hypertrophy and OSA symptoms with sHSAT during simultaneous in-lab PSG. Aims were to determine the technical feasibility of using sHSAT in this population and to compare sHSAT results to PSG. The primary endpoint was AHI by sHSAT compared to AHI by PSG and presence of OSA. Sensitivity analysis was performed for presence or absence of OSA diagnosis based on sHSAT versus PSG. Bland-Altman and concordance correlation calculations were used for comparisons. Results 50 patients, median age 4 (IQR 3-5), met criteria; 39 completed PSG and HSAT. The sensitivity with sHSAT for OSA prevalence based on proprietary categorization was 94.1%, specificity 22.7%, LR+ 1.22, and LR- 0.26, with PSG OSA prevalence of 43.6%. There was a 9% sHSAT total failure rate, and the device frequently fell off, resulting in TST difference of -226.9 ±182.8 min between sHSAT and PSG. PSG was trimmed to include only segments where HSAT was confirmed to be on before comparisons. Concordance correlation coefficient between sAHI and AHI-PSG was 0.52. The Bland-Altman analysis comparing sAHI and PSG AHI revealed a mean difference of 0.73 (95% confidence limits: -3.47 to 4.93). Considering only obstructive events, the Bland-Altman the sAHI vs the AHI-PSG shows a mean difference of 1.52 (95%CI -5.40 to 8.44). Conclusion This pilot study demonstrated challenges with feasibility in using the sHSAT in this age group given likelihood of technical difficulties leading to absent or truncated data. When compared with PSG, sHSAT demonstrated a high false-positive rate for diagnosis of OSA, particularly concerning if guiding surgical management. This topic is of considerable importance to the practice of pediatric sleep medicine; further investigation of technological advances in this area is imperative. Support (if any)