Hi, I'm Doctor Mahadevan and I'm joined by Dr. Andrea Dreyfuss and we're going to be speaking on the approach to mild dyspnea. In this lecture, we will be covering the following topics, the proper position for patients with respiratory distress. How to provide supplemental oxygen to these patients. How to reassess the patient's condition and determine if your interventions are working. and finally, avoidable pitfalls and safety issues. The three keys to managing the patient with mild dyspnea are proper patient positioning, the provision of supplemental oxygen, and then reassessing the patient to decide if they need additional interventions. The traditional approach to patients in respiratory distress is to place them in the upright position. Dr. Dreyfuss, why do patients with shortness of breath seem to benefit from this position? Patients with shortness of breath tend to prefer the sitting upright because they can generally maximize their lung volumes and improve their air exchange. In patients who are breathing on their own, are hypoxic and are at risk for COVID-19 infections, a new approach to patient positioning has emerged, specifically placing patients in the prone position, which means having the patient turn onto their stomachs. Dr. Dreyfuss, is there a precedent for placing dyspneic patients in the prone position? Interestingly, there is. Awake proning has been demonstrated to decrease rates, of intubation and improve outcomes in patients with ARDS. Typical protocols include 30 to 120 minutes in the prone position, followed by the left lateral decubitus position, then the right lateral decubitus position, and then back to the upright position. That's right. Typically, you'll begin to see the benefits of the new position in five to ten minutes. And it's important not to maintain any position if the patient's breathing and comfort do not improve. In a recent study conducted in New York, the epicenter for COVID infections in the United States, they examined 50 patients with a median oxygen saturation of 80% on presentation. After placement of supplemental oxygen, their median oxygen saturation improved 84%. So they were still hypoxic inspite of supplemental oxygen? Yes, that's right. They were still hypoxic after the traditional therapies for hypoxemia. But amazingly, five-minutes after assuming the prone position, their O2 saturations improved all the way up to 94%. So early self proning was simple and cost effective in addressing hypoxia in these patients with COVID-19 infections. After positioning the patient with mild dyspnea, the next step is to provide supplemental oxygen Gibbs supplemental oxygen therapy immediately to patients with respiratory distress, hypoxemia, or shock. There are no absolute contraindications to the administration of supplemental oxygen. Supplemental oxygen therapy is ineffective for patients who are not breathing. A patient who was not breathing needs bag mask ventilation followed by endotracheal intubation. There are three requirements to provide supplemental oxygenation. First and oxygen source such as an O2 tank wall source or oxygen concentrator, a pressure regulator with a flow meter, and a delivery device such as a nasal canula, simple face mask, or non-rebreather mask. An oxygen cylinder or wall source is going to deliver 99 to 100% oxygen, whereas the percentage of oxygen coming from a portable oxygen concentrator can vary, but is generally greater than 90%. The pressure regulator controls the pressure coming out of an oxygen cylinder. The flow meter controls the rate at which the oxygen flows. Flow rates can be set from one liter per minute to 25 liters per minute. The exact flow rate will depend on the type of delivery device you are using. This is a pressure compensated flow meter attached to a wall source of oxygen. The rate of oxygen flow can be turned on or off or adjusted by turning the knob on the flow meter. A float ball rises or falls based on the flow of oxygen. and the maximum flow rate is 15 liters per minute. We're going to discuss three delivery devices, the nasal cannula, simple face mask, and non-rebreather mask. With nasal cannula, the oxygen is delivered through two small prongs inserted into the nostrils. The oxygen flow rates are typically one to six liters per minute, which delivers an FiO2 of 24 to 44%. The reason we don't exceed six liters per minute when using a nasal cannula is that higher flow rates will irritate the nasal mucosa, which can lead to bleeding. If you're going to use a nasal cannula for a prolonged period of time, consider using an oxygen humidifier to simple face mask has ports on each side which allow room air to be drawn in during inhalation and mixed with the oxygen being supplied to the mask. At flow rates of six to ten liters per minute, a simple face mask can deliver an if FiO2 of 40 to 60%. The non-rebreather mask combines a mask with a reservoir bag, which is filled with oxygen. When the patient inhales, they draw pure oxygen from the reservoir bag. When they exhale, air escapes through the small exhalation ports on the side of the mask, not back into the reservoir bag. That's right. That ensures that the reservoir bag is always filled with oxygen. Remember, the oxygen flow rate needs to be 12 to 15 liters per minute to ensure that the reservoir bag does not collapse during inhalation. Another approach is to place a non-rebreather mask over a nasal cannula, which delivers an effective FiO2 of a 100% by preventing the inadvertent accumulation of carbon dioxide in the hypopharynx and nasopharynx. When considering a stepwise approach to providing supplemental oxygen, start with either a nasal cannula or simple face mask, and if the patient fails to improve with either of these devices, then apply a non-rebreather mask. or a non-rebreather mask over a nasal cannula. Following any interventions to treat dyspnea, such as positioning the patient or providing supplemental oxygen, is very important to reassess the patient's clinical condition and vital signs, particularly their oxygen Saturation. The clinical reassessment includes evaluating the patient's own assessment of their condition, whether they feel better or not, their work of breathing and their vital signs, specifically their respiratory rate and oxygen saturation. If they're improving, it suggests that your interventions are working, at least for the moment. If they're not improving, it means that you need to think about additional interventions like repositioning the patient or high flow nasal cannula or intubation and mechanical ventilation. As part of the WHO guidelines following positioning, supplemental oxygen, and stabilization, the target oxygen saturation in adults is greater than 90%. The target oxygen saturation for pregnant adults is greater than or equal to 92 to 95%. It 's not necessary to achieve an oxygen saturation of 100%. So titrate the amount of oxygen to achieve these O2 saturation targets. If you're unable to achieve these oxygen saturation targets, the next step would be consideration of high flow nasal cannula or non-invasive ventilation. These modalities will be discussed in the next lecture. Next we are going to discuss some avoidable pitfalls in the management of patients with mild dyspnea. First, avoid benzodiazepines or narcotic analgesic agents in the initial treatment of agitated patients. If a patient with dyspnea is agitated, think of hypoxia or respiratory failure first and ensure that you are appropriately evaluating and treating these conditions. That's right. Administering a benzodiazepine or narcotic analgesic medication to a patient with agitation from hypoxia or respiratory failure could be lethal in patients with obstructive pulmonary disorders like emphysema or COPD, or chronic respiratory insufficiency, be careful when administering oxygen. These patients often have hypercarbia, so the over administration of oxygen, especially for an extended period of time, can reduce their respiratory drive, and this can lead to further hypercarbia, altered mental status, and even complete respiratory collapse. Remember, it's okay to administer oxygen to these patients, but you need to titrate the oxygen to their specific needs rather than just apply the maximum amount of oxygen. Finally, it's important to ensure that the oxygen is flowing to the patient. Masks and nasal cannulas can become disconnected from their oxygen supplies. And oxygen tanks have a limited supply of oxygen that can run out over time. Replace the oxygen cylinder when the pressure falls to 200 PSI or lower. When administering oxygen, there are some serious safety issues to be aware of. First, be careful when using oxygen cylinders and do not stand them upright unless they are well secured. Under the right conditions, if they fall over, they have the potential to become a rocket and cause injuries. That's right. In this video, we see an oxygen canister fall off a moving truck and shoot across the road like a rocket and strike and innocent motorist on a scooter. Oxygen represents a fire hazard because it allows other materials to ignite at a lower temperature and burn hotter and faster. So always keep combustible materials away from the oxygen cylinder regulators, fittings, valves, and tubing. Never let anyone to smoke in light of flame in the vicinity of oxygen cylinders. Finally, in theory, all forms of supplemental oxygen and respiratory support may potentially aerosolized respiratory pathogens, such as Coven 19. That means that a patient on auction from a nasal cannula, face mask, or non-river. Either mask could spread viral particles into the air around them. A study published in the Hong Kong medical journal in 2014 suggests that a nasal cannula at five liters could dispersed particles about 42 centimeters from the patient. That is, simple face masks at ten liters could dispersed particles about 40 centimeters from the patient. And that a non-rebreather, mask at 12 liters could disperse particles about ten centimeters from the patient. In another study from 2020 this year found that dispersion of particles was 11 to 12 centimeters for A simple mask at 15 liters, and 25 to 27 centimeters for a non-rebreather mask at ten liters. So what is the significance of all these studies? Well, first of all, it doesn't mean that we should not administer supplemental oxygen to our patients with dyspnea. What we can learn from these studies is that there is potential for dispersion and that we need to take the necessary measures to protect ourselves and our patients. Another recent study that modeled the velocity of exhaled gas flow found that a well-fitting standard surgical mask can significantly reduce aerosolization when placed over low or high flow nasal cannulas. As seen in this first image, a patient on a nasal cannula at six liters, has the potential to disperse viral particles on exhalation as far as one meter or three feet. However, following the placement of a surgical mask over their nasal cannula, you can see that there is a significant reduction in particle dispersion. For this reason, consider placing a surgical mask over any patient receiving oxygen therapy by nasal cannula to significantly reduce the degree of dispersion of viral particles from exhalation. In summary, the approach to a patient with mild dyspnea includes positioning, especially prone positioning, which could save the patient's life. Then supplemental oxygen, starting with the nasal cannula or simple mask and progressing to a non-rebreather. And then next, reassessing the patient to ensure they are responding to these measures. Be aware of potential pitfalls like failing to monitor COPD patients on high flow oxygen, and finally, being aware of the dispersion of different forms of supplemental oxygen
