![]() When setting up a ventilator for an adult patient, the only calculation you will have to do is determine their ideal body weight and then use that weight to choose a safe tidal volume for your patient. IBW is calculated based on a patient’s sex and height to ensure the weight used to estimate the tidal volumes is correct based on what the patient should be getting. To fix this problem once and for all, ventilation is now completely based on Ideal Body Weight (IBW). Notice that the lung size is smaller in the shorter person on the right (there is a bit of lung collapse here as well). These two x-rays show two males of comparative age, sex and body fat, but different heights. The size of the lungs does not change based on the body weight of the patient. Regardless of body habitus, a bariatric patient’s lungs are not larger than another patient that is the same sex and height. By ventilating heavier patients with larger volumes, clinicians were overinflating the alveoli in the lungs and causing barotrauma and volutrauma, leading to VILI.įun fact: If you see a full body CT scan or MRI of a bariatric patient, this concept is clear. A person’s lung size is based on skeletal structure, which means the only relevant variables are sex and height. After bariatric patients were getting VILI at a higher incidence when the larger tidal volumes were used, further investigation revealed that the size of the lungs do not alter based on body weight of the patient. It was still common practice to assume patients with a higher weight required a larger volume to satisfy their ventilation needs (O 2 in and CO 2 out) because they had more habitus, meaning more cells in the body creating CO 2 and needing oxygen to function. The smaller the patient, the smaller the tidal volumes and the larger the patient, the larger the tidal volumes. What happens? It pops! The same thing can happen to the alveoli.Ī weight-based approach to choosing tidal volumes started to be used. Think of inflating a balloon to the point that the pressure and volume are too high. The terms barotrauma and volutrauma can be used interchangeably and they mean the same thing-volume equals pressure, and pressure equals volume. Health care providers were directly harming their patients with this high volume/low RR ventilation strategy. The conclusions were very clear that using large tidal volumes directly related to increased incidence of VILI by causing barotrauma (too much pressure in the alveoli) and volutrauma (too much volume in the alveoli). When it was identified that mechanical ventilation was seeming to cause bilateral damage to the lungs, multiple studies were carried out to determine if the settings on the ventilator were contributing to this. ![]() Acute Respiratory Distress Syndrome: New Definition, Current and Future Therapeutic Options.If you would like some basic knowledge regarding ARDS, refer to these two links for a brief overview (the first link is more basic, and the second link provides more advanced information): These patients can become very sick and difficult to ventilate. It can be caused by other processes in addition to VILI. It is usually identified on a chest x-ray after other pathophysiologies are ruled out. ARDS is a complex pathology that is recognized as diffuse bilaterally inflammation and damage to the lungs.
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