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Heart of the Matter ventilation cardiovascular challenges

Connecting the dots between breathing, ventilation and cardiovascular challenges

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Breathing is work. And while mechanical ventilation can lessen a patient's load, it certainly doesn't turn the work of respiration into a day at the beach. After all, ". . .ventilation is exercise," said Michael R. Pinsky, MD, professor of critical care medicine, University of Pittsburgh, in a summary document. For patients with cardiovascular disease, the stress of breathing is like a stretch of hard time. Even weaning from mechanical ventilatory support is nothing short of ". . . a cardiovascular stress test," he declared. That's not easy for someone with a challenged cardiovascular system.

"Nearly half of everyone seen by respiratory therapists in hospitals will have some cardiovascular issue," said Rami Khayat, MD, associate professor of internal medicine at Ohio State University and director of the Sleep Heart Program at the university's Wexner Medical Center. "Their respiratory muscles require up to 30 % of their cardiac output in many cases. This is a significant portion of what their heart can do."

Use of Noninvasive Ventilation
Often, patients on a cardiac floor, "with coronary syndromes or underlying diastolic or systolic cardiac function, may present with, or develop, respiratory distress," noted Khayat, "and they may show signs of volume overload or pulmonary edema. These patients are perfect candidates for noninvasive ventilation."

The importance of noninvasive ventilation in this population must be emphasized, Khayat told ADVANCE, because benefits are significant. "It allows for minimized sedation, results in less pneumonia and provides for faster liberation from the ventilator. And some studies show that when patients are treated noninvasively, as compared to being on invasive ventilation, they survive longer," said Khayat.

When patients are in the first moments of noninvasive ventilatory therapy, RTs are the providers who can help assure the success of the care. "Their expertise in fitting the mask and assessing initial response to the settings are essentials," said Khayat. He cautioned that sometimes masks are fitted when patients are awake and ".when the patients go to sleep, their mouths [open and loosen] the seal on the mask. The result is a huge amount of leak and loss of pressure." He said masks must be big enough to cover halfway between the lip and the chin so that the mouth will stay within the confines.

Khayat also noted that therapists must be particularly vigilant during the first half hour of a patient's noninvasive therapy. "RTs must make a judgment if the patient is benefitting from treatment very quickly - before we lose 'the magic window,'" said Khayat, referring to that brief honeymoon period when the patient is hopeful and willing to try - and be compliant with - therapy.

"Once CPAP or BiPAP is turned on, respiratory distress should decrease, oxygenation should improve, arterial blood gasses should improve, heart rates should come down, the patients' color should improve and they should be visibly more comfortable. The first half hour is crucial to their eventual success on the mask. RTs should monitor patients constantly during this critical time, making sure they are tolerating treatment and responding." Administration of non-invasive ventilation should be delineated in a protocol with clear benchmarks and role assignments among the RT, nurse and physician.

Keep Sleep Quality in Mind
For many patients with cardiovascular issues, there will also be a sleep component to their health challenges, said Atul Malhotra, MD, who in addition to being chief of pulmonary and critical care medicine at University of California, San Diego will also serve as 2015-2016 president of the American Thoracic Society.

"The main things I often see overlooked, and that are worth emphasizing, are the abnormalities of breathing during sleep which are very common in patients with heart disease," said Malhotra. "In fact, a high percentage of these patients will have an abnormality which could affect their prognosis and their long-term health. Fortunately, we have interventions that can help."

Malhotra noted that there are some forms of central sleep apnea common in patients with heart failure, yet not so common among other patient populations. He said a large study group found that about a third of the patients with heart failure had normal sleep, a third had obstructive sleep apnea, and the remaining third had central sleep apnea. He explained, "When your heart is misbehaving, carbon dioxide levels can vary a lot. If they drop low enough, you stop trying to breathe." It is this absence of respiratory effort that defines central apnea.

One common therapy in use for central apnea is CPAP; however; while it may be helpful, Malhotra said it does not eliminate the situation. "Now there are newer devices that may be more useful in patients with heart failure and central sleep apnea. These are called auto or adaptive servo-ventilation (ASV)," he explained. Noting that ASV devices are designed to help stabilize breathing patterns, he also said, "If the patient is breathing too much, ASV backs off and doesn't worsen the situation, yet if the patient is trying to breathe but is not breathing enough, it offers some back-up support." While ASV devices have been FDA cleared and are in use for some indications, Malhotra said large-scale trials are still ongoing to determine if the therapy improves heart disease and helps improve patient survival.

Invasive Ventilation
While non-invasive ventilation may be an appropriate first ventilatory step for many patients, it does not suit everyone. "Specifically, it is not useable for patients with decreased mental status, patients who are unable to cough or clear the airways, patients who are very weak and cannot remove or interact with their mask. This would put them at risk for aspiration if, for example, if they were to vomit into the mask and were unable to remove it," said Khayat. For these patients, invasive ventilation is indicated.
For patients with heart disease, "the approach to managing mechanical ventilation depends on the underlying reason for respiratory failure," said Khayat. "If they are on invasive ventilation for heart failure, they often do not require high amounts of PEEP. And they often can wean relatively quickly when heart function improves. However, if the patient has underlying respiratory issues - such as pneumonia or ARDS - and coexisting heart failure, then principles of using low tidal volume strategy and high PEEP would be required; it's been shown to improve survival."

However there is a caveat, said Khayat. "Sometimes the use of high PEEP in patients with systolic dysfunction, and low volume status can result in hypotension. It's something RTs have to pay attention to."

As time and therapy progresses and patients are ready to be weaned from invasive ventilation, there are still more considerations specific to patients with cardiovascular challenges. Khayat explained, "At many facilities, RTs use modified breathing trials in which they leave some minimized PEEP on the system as the trial is conducted." Khayat said this may present a problem, because it does not exactly mimic spontaneous breathing and there is no way to really know if the patient can tolerate the complete removal of PEEP.

"Once extubated, some cardiovascular heart failure patients go into pulmonary edema or fail extubation due to the work of breathing and the loss of PEEP. PEEP increases intrathoracic pressure and decreases the venous return in part, decreasing lung volume in general, resulting in less pulmonary edema," Khayat explained. "When PEEP is removed, blood flow into the chest increases and pulmonary edema can occur - especially with underlying low cardiac function." If a spontaneous breathing trial is conducted without any PEEP, however, it can detect a patient's tolerance to true spontaneous breathing.

Studies have also shown that extubating a patient from invasive ventilation to noninvasive ventilation can be an excellent step-down procedure to prepare the way to full spontaneous breathing, according to Khayat. "Some patients who have passed a spontaneous breathing trial and look to be doing reasonably well can be extubated preemptively to noninvasive ventilation for some time before being taken off completely," said Khayat. "Some studies have shown that patients do better and are more likely to be liberated from the ventilator if they follow up extubation with at least a short period of noninvasive ventilation."

Remembering the Human Spirit
Taryn Parker-Delton, RRT, Children's Hospital of Los Angeles, offered yet another view of treating patients with cardiac and respiratory concerns. She, too, reiterated the importance of monitoring patients closely as ventilation begins, and the necessity of being sensitive to the sounds of their breathing, to the height of their chest rise, to their blood gas values, to their vitals signs. But she also stressed that underneath the masks, the vents, the pulse ox clips and the oxygen lines, there is a human spirit in need of care.

"During a procedure or during intubation are you watching to see if a patient is arousing, waking up, moving or showing signs of discomfort?" she asked rhetorically. "If a patient is inadequately sedated and wakes up or is awake while having an ET tube stuck down his throat, and/or may be able to hear and feel everything going on but is unable to talk, respond or move, just imagine the stress. Make sure you are mindful and monitoring your patient's heart rate, blood pressure, respiratory rate and ask if they can squeeze your hand immediately before and when you are doing procedures to make sure they are adequately sedated and stable," said Parker-Delton.

"Yes, we work on machines. Yes, we have excellent tools like catheters to monitor the heart's pressures or the best ventilator technology to find out if we are adequately/inadequately ventilating a patient. But in the greater scheme of things, if you are not tending to the human being - not just the medical portion but the emotional portion as well - you are not completely doing your job. I think it bears repeating."


Valerie Neff Newitt is on staff at ADVANCE. Contact: vnewitt@advanceweb.com



     

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