publications

2024

1. arXiv

   Personalized language modeling from personalized human feedback

   Xinyu Li, Zachary C Lipton, and Liu Leqi

   arXiv preprint arXiv:2402.05133, 2024

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   Reinforcement Learning from Human Feedback (RLHF) is commonly used to fine-tune large language models to better align with human preferences. However, the underlying premise of algorithms developed under this framework can be problematic when user preferences encoded in human feedback are diverse. In this work, we aim to address this problem by developing methods for building personalized language models. We first formally introduce the task of learning from personalized human feedback and explain why vanilla RLHF can be ineffective in this context. We then propose a general Personalized-RLHF (P-RLHF) framework, including a user model that maps user information to user representations and can flexibly encode our assumptions on user preferences. We develop new learning objectives to perform personalized Direct Preference Optimization that jointly learns a user model and a personalized language model. We demonstrate the efficacy of our proposed method through (1) a synthetic task where we fine-tune a GPT-J 6B model to align with users with conflicting preferences on generation length; and (2) an instruction following task where we fine-tune a Tulu-7B model to generate responses for users with diverse preferences on the style of responses. In both cases, our learned models can generate personalized responses that are better aligned with the preferences of individual users.

2. AAAI

   Adapting Animal Models to Assess Sufficiency of Fluid Resuscitation in Humans (Student Abstract)

   Ryan Schuerkamp, Xinyu Li, Brian Kunzer, Leonard S Weiss, and 4 more authors

   In Proceedings of the AAAI Conference on Artificial Intelligence, 2024

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   Fluid resuscitation is an initial treatment frequently employed to treat shock, restore lost blood, protect tissues from injury, and prevent organ dysfunction in critically ill patients. However, it is not without risk (e.g., overly aggressive resuscitation may cause organ damage and even death). We leverage machine learning models trained to assess sufficiency of resuscitation in laboratory animals subjected to induced hemorrhage and transfer them to use with human trauma patients. Our key takeaway is that animal experiments and models can inform human healthcare, especially when human data is limited or when collecting relevant human data via potentially harmful protocols is unfeasible.

2022

1. Sensors

   Automated Assessment of Cardiovascular Sufficiency Using Non-Invasive Physiological Data

   Xinyu Li, Michael R Pinsky, and Artur Dubrawski

   Sensors, 2022

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   For fluid resuscitation of critically ill individuals to be effective, it must be well calibrated in terms of timing and dosages of treatments. In current practice, the cardiovascular sufficiency of patients during fluid resuscitation is determined using primarily invasively measured vital signs, including Arterial Pressure and Mixed Venous Oxygen Saturation (SvO2), which may not be available in outside-of-hospital settings, particularly in the field when treating subjects injured in traffic accidents or wounded in combat where only non-invasive monitoring is available to drive care. In this paper, we propose (1) a Machine Learning (ML) approach to estimate the sufficiency utilizing features extracted from non-invasive vital signs and (2) a novel framework to address the detrimental impact of inter-patient diversity on the ability of ML models to generalize well to unseen subjects. Through comprehensive evaluation on the physiological data collected in laboratory animal experiments, we demonstrate that the proposed approaches can achieve competitive performance on new patients using only non-invasive measurements. These characteristics enable effective monitoring of fluid resuscitation in real-world acute settings with limited monitoring resources and can help facilitate broader adoption of ML in this important subfield of healthcare.

2021

1. IEEE JBHI

   Deep survival machines: Fully parametric survival regression and representation learning for censored data with competing risks

   Chirag Nagpal, Xinyu Li, and Artur Dubrawski

   IEEE Journal of Biomedical and Health Informatics, 2021

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   We describe a new approach to estimating relative risks in time-to-event prediction problems with censored data in a fully parametric manner. Our approach does not require making strong assumptions of constant proportional hazards of the underlying survival distribution, as required by the Cox-proportional hazard model. By jointly learning deep nonlinear representations of the input covariates, we demonstrate the benefits of our approach when used to estimate survival risks through extensive experimentation on multiple real world datasets with different levels of censoring. We further demonstrate advantages of our model in the competing risks scenario. To the best of our knowledge, this is the first work involving fully parametric estimation of survival times with competing risks in the presence of censoring.

2019

1. MLHC

   Dynamically personalized detection of hemorrhage

   Chirag Nagpal, Xinyu Li, Michael R Pinsky, and Artur Dubrawski

   In Machine Learning for Healthcare Conference, 2019

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   Rapid detection of hemorrhage is of major interest to the critical care community, enabling clinicians to take swift actions to mitigate adverse outcomes. In this paper, we describe a model that allows rapid detection of the onset of hemorrhage by monitoring the Central Venous Pressure (CVP). As opposed to prior work in the domain, our model does not rely on prior availability of a stable physiology of a patient as a baseline of reference, and it makes generative assumptions on the monitored vital sign. This allows for rapid on-the-fly personalization to a previously unseen patient’s physiology. This property makes the proposed approach particularly relevant to e.g. trauma care and other scenarios where reference hemodynamic data may not be readily available for any new patient. We compare our model against strong discriminative alternatives and demonstrate its potential utility through empirical evaluation.

2018

1. ML4H

   Leveraging Routine Pre-Operative Blood Draws to Predict Hemorrhagic Shock During Surgery

   Xinyu Li, Michael R Pinsky, Gilles Clermont, and Artur Dubrawski

   NeurIPS Machine Learning for Health (ML4H) Workshop, 2018

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   We investigate the utility of machine learning to estimate the likelihood of surgical patients to develop a hemorrhagic shock during surgery. We use hemodynamic responses to routine blood draws as virtual indicators of future shock. Our results suggest that by capturing sequential patterns in vital signs waveform data observed in pre-surgical settings, it is possible to predict which patients will likely get into shock in the course of surgery. These findings, after further validation, can enable building clinically useful screening tools to preempt complications in surgical patients and to inform medical resource allocation and planning, with the use of only already performed diagnostic procedures: routine lab test blood draws.