Wow,  my heart goes out to all of you. I assume that they have the alarm equipment and so on in place. I know there are socks that measure heart rate and oxygen levels, but not sure that this actually helps (or know if they are reliable in your opinion).

(Not all this info fits your exact example but when I use quotes, I prefer not to edit the quoted material.)

> Emotional & psychological symptoms:
>
> - Shock, denial, or disbelief
> - Confusion, difficulty concentrating
> - Anger, irritability, mood swings
> - Anxiety and fear
> - Guilt, shame, self-blame
> - Withdrawing from others
> - Feeling sad or hopeless
> - Feeling disconnected or numb
> 
> Physical symptoms:
> 
> - Insomnia or nightmares
> - Fatigue
> - Being startled easily
> - Difficulty concentrating 
> - Racing heartbeat
> - Edginess and agitation
> - Aches and pains
> - Muscle tension

What might help: 

 1. exercise
 2. maintaining  relationships
 3. take care of your own health -- eat properly and sleep as well as possible. Enlist family members who can watch baby and allow for uninterrupted (or only for feeds) parental sleep
 4. Self-regulate your nervous system:

> No matter how agitated, anxious, or out of control you feel, it’s
> important to know that you can change your arousal system and calm
> yourself. Not only will it help relieve your anxiety but it will also
> engender a greater sense of control.
> 
> Mindful breathing.  If you are feeling disoriented, confused, or
> upset, a quick way to calm yourself is through mindful breathing.
> Simply take 60 breaths, focusing your attention on each out breath.
> 
> Sensory input. Does a specific sight, smell or taste quickly make you
> feel calm? Or maybe petting an animal or listening to music works to
> quickly soothe you? Everyone responds to sensory input a little
> differently, so experiment to find what works best for you. 
> 
> Staying grounded. To feel in the present and more grounded, sit on a
> chair. Feel your feet on the ground and your back against the chair.
> Look around you and pick six objects that have red or blue in them.
> Notice how your breathing gets deeper and calmer.
> 
> Allow yourself to feel what you feel when you feel it. Acknowledge
> your feelings about the trauma as they arise and accept them.

[LINK](https://www.helpguide.org/articles/ptsd-trauma/emotional-and-psychological-trauma.htm)

Meditation has worked for me and my family for years. Many people think it is 'silly' -- but it can literally take me from panic to being able to cope. When my daughter was six, she wandered off the school property and was found asleep (she was ill and we had not known before school) by a school neighbour on her chaise two hours later. I could hardly breathe. My heart was racing and I very nearly fainted. I was lucky as the police officer knew me from my own school (where I taught) and told me to "Breathe!" That reminded me to centre myself and got me restarted and though I was terrified beyond explanation, I was functioning again. I called the school for weeks at lunch -- just to make sure my daughter was there. 

They [could be suffering from PTSD](http://www.medscape.com/viewarticle/746071)

> Post-traumatic stress disorder (PTSD) has recently been noted in
> parents after traumatic childbirth, with premature infants in the
> NICU, after a child has experienced acute trauma or a life-threatening
> illness and when a child develops a chronic illness. The reported
> incidence of PTSD in parents in these situations ranges from 1.5% to
> 6% with traumatic childbirth (Ayers & Pickering, 2001; Menage, 1993)
> to 21% to 23% when a child has been in the NICU or PICU (Balluffi et
> al., 2004; Vanderbilt, Bushley, Young, & Frank., 2009), to as high as
> 30% for parents of children with leukemia (Kazak et al., 1997). In a
> study by Landolt, Vollrath, Laimbacher, Gnehm, and Sennhauser (2005),
> all mothers of children who had experienced an episode of severe
> hypoglycemia developed PTSD.