VentMedic Posted October 8, 2009 Posted October 8, 2009 (edited) CBHare: the 100% SpO2 with a high A-a gradient... how does he have a high A-a gradient but still good sats? How does tubing fix the A-a gradient? Look at the oxyhemoglobin dissociation curve to see the correlation between mmHg and SaO2. One might expect the PAO2 to be at 450 mmHg and the PaO2 to be 440 mgHg on a healthy patient on a NRBM. If the PaO2 is at 90 mmHg, that is what one might expect on a healthy person on room air and would give you an SpO2 in the high 90s. However, if the patient is on a NRBM with an FiO2 of 0.90, that gives you an A-a gradient of 350 mmHg which is very significant. Intubating may not immediately fix the problem. The patient may even die because of the oxygenation problems such as what we are seeing with the Influenza A patients and ARDS. This is part of the discussion Tnuigs and I were having on the Ventolin/H1N1 thread. It may take the serious RT technology such as High Frequency Ventilation, Nitric Oxide or ECMO to oxygenate a patient. But, we would hope that the direct route to the lungs with a closed circuit, PEEP can do its job to improve oxygenation. Check out the Respiratory Failure link here: http://www.ccmtutorials.com/ In the All about Oxygen section, you'll find some information on absorption atelectasis and that will explain about nitrogen. Read about ARDS under Acute Lung Injury and you will learn about damage to the various cells. There is also the O2 toxicity concern from high concentrations of O2 for a long period of time. Usually we try to lower the FiO2 within 24 hours to below at least 0.60 with 0.50 being preferred. However, we must also look at other factors that may still require significant O2 to maintain adequate PaO2 or SvO2 which is venous saturation. Patients with sepsis and some TBIs are monitored closely and may need more ventilatory support, pressors or fluids to maintain an adequate range. For some patients such as those with PNA from Influenza A, they may be on special ventilators for several days or even weeks until the lungs heal well enough to have the FiO2 at a reasonable number. The same for patients that develop ARDS due to trauma or sepsis. Edited October 8, 2009 by VentMedic 1
RavEMTGun Posted October 8, 2009 Posted October 8, 2009 http://www.ccmtutorials.com/ Great info and a great link... sometimes I really think I should go RRT instead of RN... 1
Recommended Posts