Table 5. Theme2 Doctor’s attitudes and culturally-constrained norms for TIV decision-making.

Category	Subcategory	Quote
2-a The relationship between the patient and the others in the decision-making process	Patients’ right for decision-making	So, a patient has a right to refuse any medical intervention. And if a patient does refuse a medical intervention, as long as it is their capacitous decision, then we as medical professionals, healthcare professionals have to obey that and to not do so would be illegal. It would be assault to continue to give an intervention that the patient had decided he did not want. (UK5) I think if it’s his capacitous decision and we’re clear that he’s making it in a capacity way, I think we can just do without the consent of the family or assent of the family. (US5)
	The role for the patient family in decision-making	And occasionally we see mistakes made where people just follow blindly what the family say but I think we also often see mistakes made where people disregard what the family say and fail to notice that they’re actually telling us something really important about the person in the bed... What can you tell me about the patient that will help me to make the right decision, not what do you want me to do for him. (UK4)
2-b Patient’s decision-decision making capacity and competency	The doctor’s concern for the decision-making capacity of ALS patients requiring TIV	Even if some research said most ALS patients did not lose cognitive function, I had some patients with mild cognitive dysfunction. Moreover, the longer they suffered ALS, the more they got the mood disorder or mild depression. I can’t believe they are competent for the very difficult decision making for withholding TIV at any point of their disease. (JP1)
		It is natural for humans to change or fluctuate their wishes. I can’t believe ALS patients can decide firmly. Because it might change later. (JP5)
	The patient’s decision-making capacity assessment system	Yeah, so that’s important. That’s why you need to make sure that he has capacity. So, capacity in the UK you don’t need to do a cognitive assessment to assess capacity you assess their ability to understand the information that you’re giving them to make an informed decision, check that they’re remembering the decision, that it’s a consistent decision. So, people can have cognitive impairment, but depending on the level of cognitive impairment, it won’t necessarily affect their ability to make a capacitous decision. So, you do a capacity assessment that is decision specific. Yes, each decision has its own, you would check capacity, particularly for such an important decision, you would check they have the capacity and there is a capacity assessment framework that we would use to ensure that the individual, regardless of their cognitive abilities, that they have capacity to make the decision. (UK5)
2-c Doctor’s communication and attitude at the decision-making process for TIV	The process of decision-making for starting and withdrawing TIV	I wouldn’t just say " Okay, Let’s do it." I would say this could have major consequences, meaning that you could die pretty quickly. Some people find over time they’re much more able to accept this new quality of life. What I would recommend is we try this for a little longer and revisit. (US4) Yes, so I would use the same framework that I’ve described. It wouldn’t be a quick, like I wouldn’t do it then and then. There would be a whole process we go through but if at the end of that process that we were certain that he was communicating clearly a capacitous decision and was not under any undue influence, then yes, we would manage him the same way. (UK5)
	Holding the TIV option back to the patient	I mean, we didn’t say, "Well, therefore, would you like a tracheostomy?" Because we respond to what the patient is saying. I mean, you could argue that maybe we’re avoiding that discussion sometimes. But it comes from I think a deep understanding and knowledge of the disease. And having looked after many, you know, several thousand patients, I feel I can instinctively go with the patient on that sort of journey and understand what they want. I mean, if they want a tracheostomy, we have that discussion, but we don’t have any kind of systematic way of triggering the discussion if that’s what you’re asking. (UK1)
		I don’t tend to say, do you want NIV 24/7 or not, that’s too threatening. (UK2)
	Providing the TIV option to the patient with the detailed information about the hardship of the life with TIV	In the US, a few famous ALS patients with TIV are always active, young and positive...most of them are wealthy... however, not all the patients with TIV can be like that, the patients should know that. (JP6)
	Requiring the patient’s firm purpose to start TIV	I don’t want hold on to my life with TIV. ("Do you think that the patient with TIV hold on to their life?") Yes, they tend to have a firm belief for their life with TIV. However, if the reason is to see their kids graduate from school, I am worried about their life with TIV after kid’s graduation. Most ALS active patients want to pursue their goal to speak out their thoughts in media, but not all the ALS patients are like that. (JP1)
	Requiring the patients’ consent that they can never stop TIV regardless their wish before starting TIV	Before starting TIV, I always ask the patient to confirm that they can never stop TIV, even if they really want to stop it. (JP2)
	Doctor’s weighing on a particular option based on professional perspective at decision-making	Even though it’s not the standard, approach here, I usually do add some color to the discussion of my own opinions with the caveat that, like, you know, obviously, it’s personal. But I think on medical side, we have responsibility to do that because we’re the ones who have medical training. We understand the natural history. We understand the prognosis better. We’ve seen this before. We have way more information. I think it’s unfair not to offer a bit of guidance on, "I think this might be the better option." I think there’s a balance between being the Irish approach, which is, "We made a decision," versus the US approach, which is, "You could pick x, y, or z. They are all equivalent."(US1)
2-d Doctor’s concerns regarding TIV withdrawal under cultural constraints	Doctor’s paternalistic attitude to ALS patients requiring TIV Doctor’s concerns for patient’s misunderstanding between withdrawing TIV and assisted dying	Particular doctors would provide TIV for the patients, and others would not. In the most part of decision-making process, only doctors have critical role for decision-making. I am suspicious that they might give biased information for the patient. (JP4) But with that caveat, it’s not guaranteed when you remove it that somebody will necessarily die quickly and they need to understand that, really. And I think certainly we wouldn’t want to do it if they stated that the reason was that  then they would be able to decide when they died. We’d have to sort of talk about that and understand what it was that they were worried about happening. It definitely probably does create the situation really where it’s easier for them to be in control (UK3)
	Legal concern for agreement with the patient’s wish to withdraw TIV	I think that in Japan today, it’s difficult to stop TIV, it’s illegal. I don’t think that all lawyers will necessarily say that if it’s all ethically OK, then it’s legally OK. (JP7)
	Doctors’ expressivist concerns for showing supportive stance for withdrawal of TIV, euthanasia, or assisted dying	If we show our support for withdrawing TIV in public, we may make enemies. Some doctors think that discontinuing TIV is absolutely unacceptable. We have to be careful. (JP6)