COVID-19 Panel: Helmet CPAP, Pronation Key Tools for Some Patients

Bruce Jancin

April 23, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Noninvasive ventilation with helmet continuous positive air pressure (CPAP) deserves to be embraced as an effective strategy in preventing self-induced lung injury, often a key factor in progression from the early milder expression of COVID-19 disease to classic severe acute respiratory distress syndrome, according to European physicians who have been through what they hope are the worst days of the pandemic in the Lombardy region of Northern Italy.

Dr. Luciano Gattinoni Courtesy Dr. Luciano Gattinoni

Helmet CPAP is a relatively inexpensive, convenient, well-tolerated intervention. It allows patients to remain conscious and responsive to commands such as "Time to roll over," which in turn frees up nursing staff. The purpose of helmet CPAP is to curb the huge inspiratory drive that's a defining feature of this disease and which, unchecked, can lead to self-induced lung injury (SILI), Luciano Gattinoni, MD, explained at a webinar hosted by the European Society of Anaesthesiology.

"Paranoid attention to inspiratory effort – checking it and correcting it – is something where we can make the difference between death and life. It's extremely important," said Dr. Gattinoni, guest professor of anesthesiology and intensive care at the University of Gottingen (Germany).

He and his fellow panelists were in accord regarding the merits of helmet CPAP as the premier method of noninvasive ventilatory assistance. They also addressed the importance of monitoring for hypercoagulation, as well as what they've come to see as the essential role of pronation in what they define as Type H disease, and the need to have detailed respiratory physiotherapy protocols in place.

"COVID-19 doesn't like physiotherapy," explained Paolo Pelosi, MD, professor of anesthesiology and intensive care medicine at the University of Genoa (Italy).

Dr. Gattinoni is credited for identification of two polar phenotypes of what he considers to be a single COVID-19 disease. Early on, many patients present with an atypical form of acute respiratory distress syndrome (ARDS), distinguished by an often-unexpected degree of hypoxia accompanied by high pulmonary compliance and surprisingly little shortness of breath. Dr. Gattinoni and colleagues call this Type L disease, which stands for low elastane, low ventilation to perfusion ratio, low lung weight on CT, and low lung recruitability, which means the patient has a high proportion of aerated lung tissue. Over time, because of either the natural history of the disease or SILI, this may shift to Type H disease, marked by high elastane, high right-to-left shunt, high lung weight, and high recruitability.

"If the pulmonary compliance is above 60 [mL/cm H2O], I'm pretty sure it's Type L. If it's 30 [mL/cm H2O] or less, I'm pretty sure it's Type H. Don't ask me about 45-55 [mL/cm H2O]; it's a grey zone," Dr. Gattinoni said.

Giuseppe Foti, MD, said helmet CPAP in patients with COVID-19 should be free flow, not attached to a ventilator, and the gas flow should be set high – at least 50 L/min – in order to prevent CO2 rebreathing. Although noninvasive ventilation is well accepted for patients with chronic obstructive pulmonary disease or acute cardiogenic pulmonary edema, it hasn't been extensively studied in the setting of ARDS. A notable exception is a single-center randomized trial in which 83 patients with ARDS at the University of Chicago were assigned to noninvasive ventilation delivered by helmet or face mask (JAMA. 2016 Jun 14;315[22]:2435-41). The endotracheal intubation rate was just 18% in the helmet group, compared with 62% in the face mask group. The 90-day mortality rate was significantly lower in the helmet group as well, noted Dr. Foti, director of the department of anesthesia and intensive care at Monza University Hospital in Milan.

Christian Putensen, MD, said he views intubation for mechanical ventilation as wise in moderate or severe ARDS with an arterial oxygen partial pressure/fraction of inspired oxygen (PaO2/FiO2) ratio below 150. But in milder, Type L COVID-19 disease, he also likes helmet CPAP. It spares the patient from the traumatic compressive stress to the lung induced by mechanical ventilation, which may cause alveolar edema and SILI.

There is, however, a caveat: "Watch carefully and do not delay intubation if you see helmet CPAP is not working; that is, if the blood gas analysis doesn't improve, the respiratory rate increases, tidal volume increases, and there is still increased respiratory drive," advised Dr. Putensen, an anesthesiologist at the University of Bonn (Germany).

There is no agreed-upon practical quantitative measure of respiratory drive. A clinical evaluation of the patient's depth of inspiration is the best guide, he added.

Dr. Gattinoni said that, when helmet CPAP can't control respiratory drive in a patient with early-stage disease, he feels the only way to interrupt this destructive process is through early intubation and what he termed "gentle mechanical ventilation," not with a positive end expiratory pressure of 20 cm H2O, but more like 4-5.

Watch for Hypercoagulation

Thromboembolic complications are a common feature in COVID-19 disease.

"I've had occasion to see the autopsy results in more than 100 patients. It's devastating to see the number of thromboses and microthromboses in the lungs, the liver, the kidney, and in the brain," Dr. Gattinoni said.

"COVID-19 is a serial killer, no doubt," Dr. Pelosi agreed. "He has no mercy for anyone. And he has two bullets: The first one is for the lung, the second is on the vascular side."

Dr. Putensen is aggressive in utilizing prophylactic high-dose anticoagulation with heparin. He carefully monitors levels of fibrinogen, Factors V and VIII, and d-dimers. In the setting of COVID-19, he has found thromboelastography to be more reliable than partial thromboplastin time in guiding heparin titration.

Pronation

Panelists agreed that pronation is an especially valuable means of enhancing oxygenation in patients with Type H disease. Dr. Putensen tries for more than 16 hours per day. Dr. Foti is preparing a study of the impact of pronation in 50 awake, nonintubated patients, most of whom were on helmet CPAP. Seven of them couldn't tolerate pronation for even an hour at a time; for the others, the median duration was 3.5 hours at a time.

"We saw a dramatic improvement, a nearly doubling in the PaO2/FiO2 ratio," Dr. Foti said.

The helmet CPAP study was done outside of the ICU because, in March 2020, the Milan hospital was utterly overwhelmed by COVID-19. The university hospital ordinarily has 25 ICU beds. This was expanded to 100 ICU beds in an effort to meet the emergency, but that still wasn't sufficient. Indeed, COVID-19 patients occupied 600 of the hospital's 650 beds. Physicians were forced to do something formerly unthinkable: triage patients for intubation and mechanical ventilation based upon age, comorbidities, and survival prospects.

"We felt schizophrenic. I completely agree with Luciano's idea to intubate early when we cannot control the respiratory drive that's due to the disease. But we couldn't do it because we had too many patients. So we had to triage," Dr. Foti recalled, breaking off with a sob as other panelists wiped away their own tears during the webcast.

Respiratory Physical Therapy

Dr. Pelosi said he believes that optimal care of patients with COVID-19 disease requires a major commitment to physical therapy. He strongly recommends having thoughtfully designed separate written protocols in place for respiratory physiotherapy during mechanical ventilation, weaning, and postextubation. COVID-19 patients typically require 7-10 days of assisted ventilation before weaning, and weaning is a protracted process as well.

"I like to say COVID-19 always requires patience. You have to be very, very patient with this disease," he emphasized. "These patients have a long and difficult weaning. If the patient isn't improving during weaning, look at two issues: superinfection and thrombembolism, macro and micro." The physical therapy measures routinely utilized at his hospital during mechanical ventilation include elevation of the bed head greater than 30 degrees, neuromuscular electrical stimulation, subglottic secretion suctioning, tracheal and oral aspiration, and cough assistance. Separate physical therapy menus are used during before and after extubation.

Dr. Gattinoni offered a final word: "We can do almost nothing with this disease. We try our best to keep the patient alive. What we can do is avoid excessive ventilation of the patient. Applying the typical treatment of ARDS in atypical [Type L] ARDS does not make sense and may be extremely harmful."

This story originally appeared on MDedge.com.

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