Cases, journal briefs & quizzes
Several users recently asked about EKG training and practice drills. We don’t intend to add such content to this website. We can recommend EKG Academy (https://ekg.academy) for its short courses and a variety of practice drills.
A 69-year-old female is brought into the emergency department by the local EMS. Her husband called 911 when she became minimally responsive at home. He reports that she has experienced an increase in shortness of breath for the past several hours, in spite of increasing the liter flow on her oxygen concentrator and using her albuterol inhaler. She has a long history of COPD. Her most recent hospitalization was three months ago.
Physical examination reveals a cachectic female who is borderline obtunded. Her respirations are rapid and shallow; breath sounds are distant.
Arterial blood is drawn for analysis while the patient is receiving oxygen via nasal cannula at 4 Lpm.
PaCO2 136 mmHg
HCO3 29 mEq
PaO2 94 mmHg
Hgb 10.2 g/dL
Lactate 1.4 mmol/L
1. What is your interpretation of these blood gas data?
2. Why is the SaO2 so low?
3. Do you believe this patient is hypoxic?
4. Based on these data, what would you do at this point?
Continuing from our mid-January blog, we have some additional studies to review.
4) The ACCP and ATS have released new clinical practice guidelines for mechanical ventilation. Specifically, these address liberation from mechanical ventilation. The guidelines were published in this month’s (January) issue of Chest.
A couple of the recommendations caught my attention (although certainly no great epiphany). One was the following (quoted from the review): “Acutely hospitalized patients who have been on mechanical ventilation for more than 24 hours, are at high risk for extubation failure, and have passed a spontaneous breathing trial should be extubated to noninvasive ventilation.” This recommendation goes along with contemporary wisdom that the longer a patient stays in ICU, the greater the risk of developing various complications (e.g. infections, lung injury, etc.).
Another recommendation involves using pressure augmentation during the spontaneous breathing trial. Also included were the recommendations of attempting to minimize sedation and encouraging early mobility. As I indicated above, these are not radical departures from what has been studied and recommended in the past. The recommendations have now been ‘protocolized.’
5) A number of articles and studies have been reported recently dealing with oxygen use. I will review the highlights of a few of these below.
a) A study reported in HealthDay apparently showed: ‘oxygen therapy may not help patients in the less severe stages of COPD.’ The report didn’t fully outline what exactly is meant by ‘less severe stages of COPD. The post hoc analysis of the study was relatively ambivalent as to the clinical implications.
Just as a personal note: I’m not sure that this study is the epiphany the reports seemed to make it out to be. The Medicare guidelines (obviously in the US) for home oxygen have been have very well spelled out.
b) The following was the conclusion of a study in JAMA: “High-flow conditioned oxygen therapy was not inferior to noninvasive ventilation for reducing reintubation and post extubation respiratory failure.” Apparently, this study was done on patients at high-risk.
I have more-or-less believed in the potential of high-flow oxygen therapy since I first saw it (and tried it for myself) many years ago. I would like to know how you’re using it in your institutions.
c) The results of the Oxygen-ICU trial (recently reported at the annual congress of the European Society of Intensive Care Medicine and published in JAMA) were interesting. The trial compared the mortality outcomes of ICU patients when placed on conservatively controlled oxygen therapy versus (what they called) the conventional, more liberal approach (in which patients are often kept in a hyperoxemic state).
The results of the trial showed the rate of mortality was 11.6% with the conservative therapy (defined as maintaining a PaO2 70 and 100 mmHg or a SpO2 between 94% and 98%) whereas the mortality rate for the conventional group (PaO2 up to 150 mmHg or SpO2 between 97% and 100%) was 20.2%. In addition, while there was no difference in ICU length of stay, the patients in the conservative group spent (on average) a day less on mechanical ventilation.
This was a relatively small study (480 patients enrolled), but the results are interesting. In my clinical career, I have noted the majority of patients I saw in the ICU had SpO2s (displayed on the monitor) of between 99% and 100%. We know from looking at the calculation for total oxygen content that there is little difference in content as the PaO2 rises above 70 mmHg or so or the SpO2 is above 95%. What price are these patients paying so that we clinicians can feel good?
d) Finally, the results of the 2015 AVOID trial seem to confirm what researchers have suspected for several years. The following quote is taken from an article recently published Chest Physician that references AVOID: “Results from the AVOID trial report that routine oxygen use in normoxic patients hospitalized with a heart attack was not beneficial and, in fact, was harmful. Patients who received oxygen had more myocardial injury than those who did not.”
It is, perhaps, worth noting the following recommendation from the American Heart Association (updated ACLS standards): “When resources are available to titrate the FiO2 and to monitor oxyhemoglobin saturation, it is reasonable to decrease the FiO2 when oxyhemoglobin saturation is 100%, provided the oxyhemoglobin saturation can be maintained at 94% or greater.”
Based on the c and d above, have you seen a change in the use of oxygen therapy in your ICUs?
This website is only for medical professional education. Contact a healthcare provider for medical care.
2021 © Clinical Skills Education LLC. All Rights Reserved.