Discussion of Dialysis Experiment

Q1) What are some reasons as to why a systolic/diastolic blood pressure measurement may be missing in the context of the study? Q2) What are the "normal" ranges for a systolic/diastolic blood pressure measurement? Q3) How large would a unit change in a blood pressure measurement from one hour to the next have to be to be considered unsual?

Q1) Was the blood pressure measured before the study? i.e. Will they consider that some patients might also have hypotension/hypertension problem? Q2) What is the difference in temperature between warm dialysate and the room temperature one? Q3) How many time passes between two consecutive dialysis sessions?

Q1) What other factors were considered for each patient? Ie/ male/female, weight Q2) Do blood pressures change with age/sex/height etc and similarly do blood pressure drops signalling hypotension change with regards to other factors? Q3) What is the expected blood pressure difference between the two and will this change with time?

Q1) What is the expected rate of emphhypotension for patients using dialysis? Q2) Would using warm dialysate cause any adverse or other effects? Q3) Would changing the dialysate temperature for the same patient cause any adverse or other effects?

Q1. Why the previously recorded blood pressure for one subject are so unstable? Q2. Why so many missing values in the 4th record of subject #01? Q3. Does the cold temperature dialysis have long term effect on blood pressure that may affect later experiments?

Q1) Are the missing values in systolic/diastolic blood pressure measurement occurring completely at random, at random or not at random? Q2) How to define "hypotension" under both conditions? Whether the definition are the same in both conditions? Q3) What are the potential reasons that participants drop out? Q4) Whether this study has a "wash-out" time? How long is that? If the side effect does not occur right away, short "wash-out" period may cause a problem.

1) Do you expect their to be any measurement error in your devices? If so, how much would you suspect?

2) Did the same person take the measurements each time?

3) Do you expect the baseline blood pressures of patients to change from session to session due to treatment and/or time of year?

1) Although the data extract is only partial data, are there enough occurrences of hypotension to allow for any statistically insightful conclusions to the hypotension incidence rate?

2) To elaborate on Huiting's & Yifan's questions on missing data, I suspect that the later observations are missing since those patients only require 2-3 hour dialysis treatment. My question, then, is how is a measurement is missing at time 2 when data is available at later time points? Can those patients on a shorter dialysis plan be used in the full analysis or should they be stratified a priori?

3) How do we incorporate an incidence of hypotension with the patients overall (regularly scheduled readings)? ie. can it be treated as an additional measurement, or should the other measurements then be treated differently?

1) Huiting, Vannny and Sean all mentioned the missing data problem. Sean gives a good conjecture about reasons for missing data. My question is, given the fact that missing data can not be recovered, how should we treat those observations. As the number of total observations are limited, I do not think discard missing sample would be a good way.

2) As cross-over study method is applied, do we need to use difference in difference to do analysis?

3) Does human body warmth have effect about the temperature of treatment? What is warm and cold treatment in the other words.