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Helmet NIV (NIPPV) ventilation on adult COVID-19 patients

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作者: Bernhard Schmitt; Mirko Belliato, MD (Pavia, Italy)

日期: 29.11.2022

Last change: 29.11.2022

English additions made in German version

All Hamilton Medical ventilators are able to deliver noninvasive ventilation through a helmet.

Helmet NIV (NIPPV) ventilation on adult COVID-19 patients

NIPPV with Hamilton Medical ventilators

The turbine-driven ventilators are able to provide higher continuous flow levels, and the air supply is fed by filtered room air (HEPA filter) with ambient humidity. Below you will find step-by-step instructions for using a helmet to apply NIPPV ventilation therapy to adult COVID-19 patients with a Hamilton Medical ventilator.

NOTE! Hamilton Medical ventilators must not be used for helmet CPAP therapy. Instead, the recommendation is to use a valveless continuous flow system connected on both sides of the helmet (Taccone P, Hess D, Caironi P, Bigatello LM. Continuous positive airway pressure delivered with a "helmet": effects on carbon dioxide rebreathing. Crit Care Med. 2004;32(10):2090-2096. doi:10.1097/01.ccm.0000142577.63316.c06​).

Step 1: Setup and preparation

  • Use a low-compliance, dual limb breathing circuit, preferably with active humidification (can lead to significant condensation in the helmet). Do not use a coaxial circuit!
  • Insert a bacterial/viral filter at the inspiratory and expiratory port of the ventilator.
  • If available, activate and prepare the mainstream or sidestream CO2 sensor with the necessary airway adapters.
  • Carry out all the required preoperational checks.
  • Connect the flow sensor directly to one of the helmet connection ports with a 22-mm ID connector or the calibration adapter.
  • Close the second helmet connection port with a plug.

Step 2: Mode selections and alarm settings

  • If available on your ventilator, select NIV mode.
  • If there is no NIV option installed, consider using PCV+/PCMV.
  • Adjust the alarm limits to avoid unnecessary alarms.
Ventilator alarms window showing settings
Alarm settings
Ventilator alarms window showing settings
Alarm settings

Step 3: Mode controls

ATTENTION! Two ventilated compartments in sequence = helmet + lungs.

Pressure ramp Set to the fastest speed possible
PEEP Target PEEP + 30%–50%
Minimum PEEP = 10 cmH2O to increase helmet stiffness
Psupport Target Psupport + 30%–50%
Minimum Psupport = 12 cmH2O
Inspiratory trigger Start with 2 l/min and maintain as low as possible
ETS Start with default ETS of 25%, monitor for cycling asynchronies and adapt accordingly
TI max Set to 1.5 s to avoid late cycling
Oxygen Start with Oxygen = 60% and titrate based on SpO2
Note: Single gas source (100% oxygen) may limit peak flow capacities

Step 4: Monitoring

Tidal volume Between 1,000 and 1,500 ml
Note: ~ 50%–75% of the VT delivered is distributed to the helmet! (12)
ExpMinVol > 25 l/min to have sufficient CO2 washout
Efficiency can be monitored with PCO2 monitoring inside the helmet - see Tips and tricks below.

Tips and tricks

  • Measure partial pressure of CO2 inside the helmet (PCO2h) in a “silent” part of the helmet (e.g., place the sensor directly above the inflated collar) to detect CO2 rebreathing. Use a mainstream or sidestream CO2 sensor from the ventilator or the monitoring system. PCO2h should not be above 5 mmHg/0.6 kPa.
  • If CO2 rebreathing is suspected, add a supplemental flow of > 10 l/min via the feeding/support port on the helmet.
  • Increase pressurization by activating TRC (100%).

(Images below courtesy of Dr. Mirko Belliato, Policlinico San Matteo Pavia Fondazione IRCCS s.c. Anestesia e Rianimazione II Pavia, Italy.)

Diagram - supplemental flow if CO2 rebreathing suspected
If CO2 rebreathing is suspected, add a supplemental flow of > 10 l/min (right) 
Diagram - supplemental flow if CO2 rebreathing suspected
If CO2 rebreathing is suspected, add a supplemental flow of > 10 l/min (right) 

Why use a helmet for NIPPV?

When oxygen is delivered by means of a nasal catheter, mask or non-invasive ventilation (NIV), substantial exhaled air is released into the surrounding air. This can increase dispersion of the virus, and subsequently increase the risk of nosocomial infection (Guan L, Zhou L, Zhang J, Peng W, Chen R. More awareness is needed for severe acute respiratory syndrome coronavirus 2019 transmission through exhaled air during non-invasive respiratory support: experience from China. Eur Respir J. 2020;55(3):2000352. Published 2020 Mar 20. doi:10.1183/13993003.00352-20208​).

There is hope that helmet-based ventilation may help reduce the risk of nosocomial infection: In this instance, the helmet replaces a face mask as the mode of delivering noninvasive ventilation. In a simulated environment using an ICU ventilator with a dual limb circuit and filter on the exhalation port of the ventilator, a comparison of NIPPV with a helmet and NIPPV with a face mask showed the leakage of exhaled air when ventilating with a helmet to be negligible (Hui DS, Chow BK, Lo T, et al. Exhaled air dispersion during noninvasive ventilation via helmets and a total facemask. Chest. 2015;147(5):1336-1343. doi:10.1378/chest.14-193412​).

Nevertheless, some experts have sounded notes of caution regarding the use of helmets. The ESICM guidelines describe them as an “attractive option” because they have “been shown to reduce exhaled air dispersion”, but the authors emphasize that they are “not certain” about the safety or efficacy of helmets in COVID-19 patients. Therefore, they were “not able to make a recommendation regarding the use of helmet NIPPV compared with mask NIPPV” (Alhazzani W, Møller MH, Arabi YM, et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19). Intensive Care Med. 2020;46(5):854-887. doi:10.1007/s00134-020-06022-513​).

My Hamilton Medical ventilator doesn’t allow for a flow-by setup...

Due to its much larger volume (always larger than the tidal volume), a helmet is similar to a semi-closed environment such as a closed room with an air exchange system. In such an environment - assuming a homogeneous distribution of CO2 - the CO2 concentration depends primarily on two factors: the amount of CO2 produced by the subject (V˙CO2), and the flow of fresh gas that flushes the environment (Taccone P, Hess D, Caironi P, Bigatello LM. Continuous positive airway pressure delivered with a "helmet": effects on carbon dioxide rebreathing. Crit Care Med. 2004;32(10):2090-2096. doi:10.1097/01.ccm.0000142577.63316.c06​). The most important considerations for the use of helmet NIPPV are as follows: 

  • The helmet is a closed environment, but ventilated
  • The presence of CO2 in the helmet is inevitable
  • Helmet volume does not influence rebreathing
  • PCO2h (partial pressure of CO2 in the helmet) does not depend on helmet size
  • Continuous high flow (minute volume) limits CO2 rebreathing
  • With a total minute volume of around 30 l/min, the amount of CO2 rebreathing should be within acceptable limits
  • Supplemental flow (if possible) and the (intended small) leaks help to reduce PCO2h

Disclaimer:

While the information contained herein is believed to be accurate, it does not represent an official recommendation from Hamilton Medical, nor may it substitute an opinion, assessment, or instructions provided by a trained healthcare professional

Full citations below: (Racca F, Appendini L, Gregoretti C, et al. Effectiveness of mask and helmet interfaces to deliver noninvasive ventilation in a human model of resistive breathing. J Appl Physiol (1985). 2005;99(4):1262-1271. doi:10.1152/japplphysiol.01363.20041​, Mojoli F, Iotti GA, Gerletti M, Lucarini C, Braschi A. Carbon dioxide rebreathing during non-invasive ventilation delivered by helmet: a bench study. Intensive Care Med. 2008;34(8):1454-1460. doi:10.1007/s00134-008-1109-52​, Racca F, Appendini L, Gregoretti C, et al. Helmet ventilation and carbon dioxide rebreathing: effects of adding a leak at the helmet ports. Intensive Care Med. 2008;34(8):1461-1468. doi:10.1007/s00134-008-1120-x3​, Patel BK, Wolfe KS, Pohlman AS, Hall JB, Kress JP. Effect of Noninvasive Ventilation Delivered by Helmet vs Face Mask on the Rate of Endotracheal Intubation in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2016;315(22):2435-2441. doi:10.1001/jama.2016.63384​, Mojoli F, Iotti GA, Currò I, et al. An optimized set-up for helmet noninvasive ventilation improves pressure support delivery and patient-ventilator interaction. Intensive Care Med. 2013;39(1):38-44. doi:10.1007/s00134-012-2686-x5​, Vargas F, Thille A, Lyazidi A, Campo FR, Brochard L. Helmet with specific settings versus facemask for noninvasive ventilation. Crit Care Med. 2009;37(6):1921-1928. doi:10.1097/CCM.0b013e31819fff937​, Antonelli M, Conti G, Pelosi P, et al. New treatment of acute hypoxemic respiratory failure: noninvasive pressure support ventilation delivered by helmet--a pilot controlled trial. Crit Care Med. 2002;30(3):602-608. doi:10.1097/00003246-200203000-000199​, Navalesi P, Costa R, Ceriana P, et al. Non-invasive ventilation in chronic obstructive pulmonary disease patients: helmet versus facial mask. Intensive Care Med. 2007;33(1):74-81. doi:10.1007/s00134-006-0391-310​, Moerer O, Herrmann P, Hinz J, et al. High flow biphasic positive airway pressure by helmet--effects on pressurization, tidal volume, carbon dioxide accumulation and noise exposure. Crit Care. 2009;13(3):R85. doi:10.1186/cc790711​,) 

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参考文献

  1. 1. Racca F, Appendini L, Gregoretti C, et al. Effectiveness of mask and helmet interfaces to deliver noninvasive ventilation in a human model of resistive breathing. J Appl Physiol (1985). 2005;99(4):1262-1271. doi:10.1152/japplphysiol.01363.2004
  2. 2. Mojoli F, Iotti GA, Gerletti M, Lucarini C, Braschi A. Carbon dioxide rebreathing during non-invasive ventilation delivered by helmet: a bench study. Intensive Care Med. 2008;34(8):1454-1460. doi:10.1007/s00134-008-1109-5
  3. 3. Racca F, Appendini L, Gregoretti C, et al. Helmet ventilation and carbon dioxide rebreathing: effects of adding a leak at the helmet ports. Intensive Care Med. 2008;34(8):1461-1468. doi:10.1007/s00134-008-1120-x
  4. 4. Patel BK, Wolfe KS, Pohlman AS, Hall JB, Kress JP. Effect of Noninvasive Ventilation Delivered by Helmet vs Face Mask on the Rate of Endotracheal Intubation in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2016;315(22):2435-2441. doi:10.1001/jama.2016.6338
  5. 5. Mojoli F, Iotti GA, Currò I, et al. An optimized set-up for helmet noninvasive ventilation improves pressure support delivery and patient-ventilator interaction. Intensive Care Med. 2013;39(1):38-44. doi:10.1007/s00134-012-2686-x
  6. 6. Taccone P, Hess D, Caironi P, Bigatello LM. Continuous positive airway pressure delivered with a "helmet": effects on carbon dioxide rebreathing. Crit Care Med. 2004;32(10):2090-2096. doi:10.1097/01.ccm.0000142577.63316.c0
  7. 7. Vargas F, Thille A, Lyazidi A, Campo FR, Brochard L. Helmet with specific settings versus facemask for noninvasive ventilation. Crit Care Med. 2009;37(6):1921-1928. doi:10.1097/CCM.0b013e31819fff93
  8. 8. Guan L, Zhou L, Zhang J, Peng W, Chen R. More awareness is needed for severe acute respiratory syndrome coronavirus 2019 transmission through exhaled air during non-invasive respiratory support: experience from China. Eur Respir J. 2020;55(3):2000352. Published 2020 Mar 20. doi:10.1183/13993003.00352-2020
  9. 9. Antonelli M, Conti G, Pelosi P, et al. New treatment of acute hypoxemic respiratory failure: noninvasive pressure support ventilation delivered by helmet--a pilot controlled trial. Crit Care Med. 2002;30(3):602-608. doi:10.1097/00003246-200203000-00019
  10. 10. Navalesi P, Costa R, Ceriana P, et al. Non-invasive ventilation in chronic obstructive pulmonary disease patients: helmet versus facial mask. Intensive Care Med. 2007;33(1):74-81. doi:10.1007/s00134-006-0391-3
  11. 11. Moerer O, Herrmann P, Hinz J, et al. High flow biphasic positive airway pressure by helmet--effects on pressurization, tidal volume, carbon dioxide accumulation and noise exposure. Crit Care. 2009;13(3):R85. doi:10.1186/cc7907
  12. 12. Hui DS, Chow BK, Lo T, et al. Exhaled air dispersion during noninvasive ventilation via helmets and a total facemask. Chest. 2015;147(5):1336-1343. doi:10.1378/chest.14-1934
  13. 13. Alhazzani W, Møller MH, Arabi YM, et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19). Intensive Care Med. 2020;46(5):854-887. doi:10.1007/s00134-020-06022-5

Effectiveness of mask and helmet interfaces to deliver noninvasive ventilation in a human model of resistive breathing.

Racca F, Appendini L, Gregoretti C, et al. Effectiveness of mask and helmet interfaces to deliver noninvasive ventilation in a human model of resistive breathing. J Appl Physiol (1985). 2005;99(4):1262-1271. doi:10.1152/japplphysiol.01363.2004

The helmet, a transparent latex-free polyvinyl chloride cylinder linked by a metallic ring to a soft collar that seals the helmet around the neck, has been recently proposed as an effective alternative to conventional face mask to deliver pressure support ventilation (PSV) during noninvasive ventilation in patients with acute respiratory failure. We tested the hypothesis that mechanical characteristics of the helmet (large internal volume and high compliance) might impair patient-ventilator interactions compared with standard face mask. Breathing pattern, CO(2) clearance, indexes of inspiratory muscle effort and patient-ventilator asynchrony, and dyspnea were measured at different levels of PSV delivered by face mask and helmet in six healthy volunteers before (load-off) and after (load-on) application of a linear resistor. During load-off, no differences in breathing pattern and inspiratory muscle effort were found. During load-on, the use of helmet to deliver pressure support increased inspiratory muscle effort and patient-ventilator asynchrony, worsened CO(2) clearance, and increased dyspnea compared with standard face mask. Autocycled breaths accounted for 12 and 25% of the total minute ventilation and for 10 and 23% of the total inspiratory muscle effort during mask and helmet PSV, respectively. We conclude that PSV delivered by helmet interface is less effective in unloading inspiratory muscles compared with PSV delivered by standard face mask. Other ventilatory assist modes should be tested to exploit to the most the potential benefits offered by the helmet.

Carbon dioxide rebreathing during non-invasive ventilation delivered by helmet: a bench study.

Mojoli F, Iotti GA, Gerletti M, Lucarini C, Braschi A. Carbon dioxide rebreathing during non-invasive ventilation delivered by helmet: a bench study. Intensive Care Med. 2008;34(8):1454-1460. doi:10.1007/s00134-008-1109-5



OBJECTIVE

To define how to monitor and limit CO(2) rebreathing during helmet ventilation.

DESIGN

Physical model study.

SETTING

Laboratory in a university teaching hospital.

INTERVENTIONS

We applied pressure-control ventilation to a helmet mounted on a physical model. In series 1 we increased CO(2) production (V'CO(2)) from 100 to 550 ml/min and compared mean inhaled CO(2) (iCO(2),mean) with end-inspiratory CO(2) at airway opening (eiCO(2)), end-tidal CO(2) at Y-piece (yCO(2)) and mean CO(2) inside the helmet (hCO(2)). In series 2 we observed, at constant V'CO(2), effects on CO(2) rebreathing of inspiratory pressure, respiratory mechanics, the inflation of cushions inside the helmet and the addition of a flow-by.

MEASUREMENTS AND RESULTS

In series 1, iCO(2),mean linearly related to V'CO(2). The best estimate of CO(2) rebreathing was provided by hCO(2): differences between iCO(2),mean and hCO(2), yCO(2) and eiCO(2) were 0.0+/-0.1, 0.4+/-0.2 and -1.3+/-0.5%. In series 2, hCO(2) inversely related to the total ventilation (MVtotal) delivered to the helmet-patient unit. The increase in inspiratory pressure significantly increased MVtotal and lowered hCO(2). The low lung compliance halved the patient:helmet ventilation ratio but led to minor changes in MVtotal and hCO(2). Cushion inflation, although it decreased the helmet's internal volume by 33%, did not affect rebreathing. A 8-l/min flow-by effectively decreased hCO(2).

CONCLUSIONS

During helmet ventilation, rebreathing can be assessed by measuring hCO(2) or yCO(2), but not eiCO(2). It is directly related to V'CO(2), inversely related to MVtotal and can be lowered by increasing inspiratory pressure or adding a flow-by.

Helmet ventilation and carbon dioxide rebreathing: effects of adding a leak at the helmet ports.

Racca F, Appendini L, Gregoretti C, et al. Helmet ventilation and carbon dioxide rebreathing: effects of adding a leak at the helmet ports. Intensive Care Med. 2008;34(8):1461-1468. doi:10.1007/s00134-008-1120-x



OBJECTIVE

We examined whether additional helmet flow obtained by a single-circuit and a modified plateau valve applied at the helmet expiratory port (open-circuit ventilators) improves CO(2) wash-out by increasing helmet airflow.

DESIGN AND SETTING

Randomized physiological study in a university research laboratory.

PARTICIPANTS

Ten healthy volunteers.

INTERVENTIONS

Helmet continuous positive airway pressure and pressure support ventilation delivered by an ICU ventilator (closed-circuit ventilator) and two open-circuit ventilators equipped with a plateau valve placed either at the inspiratory or at the helmet expiratory port.

MEASUREMENTS AND RESULTS

We measured helmet air leaks, breathing pattern, helmet minute ventilation (Eh)), minute ventilation washing the helmet (Ewh)), CO(2) wash-out, and ventilator inspiratory assistance. Air leaks were small and similar in all conditions. Breathing pattern was similar among the different ventilators. Inspiratory and end-tidal CO(2) were lower, while (Eh) and (Ewh) were higher only using open-circuit ventilators with the plateau valve placed at the helmet expiratory port. This occurred notwithstanding these ventilators delivered a lower inspiratory assistance.

CONCLUSIONS

Additional helmet flow provided by open-circuit ventilators can lower helmet CO(2) rebreathing. However, inspiratory pressure assistance significantly decreases using open-circuit ventilators, still casting doubts on the choice of the optimal helmet ventilation setup.

Effect of Noninvasive Ventilation Delivered by Helmet vs Face Mask on the Rate of Endotracheal Intubation in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial.

Patel BK, Wolfe KS, Pohlman AS, Hall JB, Kress JP. Effect of Noninvasive Ventilation Delivered by Helmet vs Face Mask on the Rate of Endotracheal Intubation in Patients With Acute Respiratory Distress Syndrome: A Randomized Clinical Trial. JAMA. 2016;315(22):2435-2441. doi:10.1001/jama.2016.6338



IMPORTANCE

Noninvasive ventilation (NIV) with a face mask is relatively ineffective at preventing endotracheal intubation in patients with acute respiratory distress syndrome (ARDS). Delivery of NIV with a helmet may be a superior strategy for these patients.

OBJECTIVE

To determine whether NIV delivered by helmet improves intubation rate among patients with ARDS.

DESIGN, SETTING, AND PARTICIPANTS

Single-center randomized clinical trial of 83 patients with ARDS requiring NIV delivered by face mask for at least 8 hours while in the medical intensive care unit at the University of Chicago between October 3, 2012, through September 21, 2015.

INTERVENTIONS

Patients were randomly assigned to continue face mask NIV or switch to a helmet for NIV support for a planned enrollment of 206 patients (103 patients per group). The helmet is a transparent hood that covers the entire head of the patient and has a rubber collar neck seal. Early trial termination resulted in 44 patients randomized to the helmet group and 39 to the face mask group.

MAIN OUTCOMES AND MEASURES

The primary outcome was the proportion of patients who required endotracheal intubation. Secondary outcomes included 28-day invasive ventilator-free days (ie, days alive without mechanical ventilation), duration of ICU and hospital length of stay, and hospital and 90-day mortality.

RESULTS

Eighty-three patients (45% women; median age, 59 years; median Acute Physiology and Chronic Health Evaluation [APACHE] II score, 26) were included in the analysis after the trial was stopped early based on predefined criteria for efficacy. The intubation rate was 61.5% (n = 24) for the face mask group and 18.2% (n = 8) for the helmet group (absolute difference, -43.3%; 95% CI, -62.4% to -24.3%; P < .001). The number of ventilator-free days was significantly higher in the helmet group (28 vs 12.5, P < .001). At 90 days, 15 patients (34.1%) in the helmet group died compared with 22 patients (56.4%) in the face mask group (absolute difference, -22.3%; 95% CI, -43.3 to -1.4; P = .02). Adverse events included 3 interface-related skin ulcers for each group (ie, 7.6% in the face mask group had nose ulcers and 6.8% in the helmet group had neck ulcers).

CONCLUSIONS AND RELEVANCE

Among patients with ARDS, treatment with helmet NIV resulted in a significant reduction of intubation rates. There was also a statistically significant reduction in 90-day mortality with helmet NIV. Multicenter studies are needed to replicate these findings.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01680783.

An optimized set-up for helmet noninvasive ventilation improves pressure support delivery and patient-ventilator interaction.

Mojoli F, Iotti GA, Currò I, et al. An optimized set-up for helmet noninvasive ventilation improves pressure support delivery and patient-ventilator interaction. Intensive Care Med. 2013;39(1):38-44. doi:10.1007/s00134-012-2686-x



OBJECTIVE

To test the effects on mechanical performance of helmet noninvasive ventilation (NIV) of an optimized set-up concerning the ventilator settings, the ventilator circuit and the helmet itself.

SUBJECTS AND METHODS

In a bench study, helmet NIV was applied to a physical model. Pressurization and depressurization rates and minute ventilation (MV) were measured under 24 conditions including pressure support of 10 or 20 cm H(2)O, positive end expiratory pressure (PEEP) of 5 or 10 cm H(2)O, ventilator circuit with "high", "intermediate" or "low" resistance, and cushion deflated or inflated. In a clinical study pressurization and depressurization rates, MV and patient-ventilator interactions were compared in six patients with acute respiratory failure during conventional versus an "optimized" set-up (PEEP increased to 10 cm H(2)O, low resistance circuit and cushion inflated).

RESULTS

In the bench study, all adjustments simultaneously applied (increased PEEP, inflated cushion and low resistance circuit) increased pressurization rate (46.7 ± 2.8 vs. 28.3 ± 0.6 %, p < 0.05), depressurization rate (82.9 ± 1.9 vs. 59.8 ± 1.1 %, p ≤ 0.05) and patient MV (8.5 ± 3.2 vs. 7.4 ± 2.8 l/min, p < 0.05), and decreased leaks (17.4 ± 6.0 vs. 33.6 ± 6.0 %, p < 0.05) compared to the basal set-up. In the clinical study, the optimized set-up increased pressurization rate (51.0 ± 3.5 vs. 30.8 ± 6.9 %, p < 0.002), depressurization rate (48.2 ± 3.3 vs. 34.2 ± 4.6 %, p < 0.0001) and total MV (27.7 ± 7.0 vs. 24.6 ± 6.9 l/min, p < 0.02), and decreased ineffective efforts (3.5 ± 5.4 vs. 20.3 ± 12.4 %, p < 0.0001) and inspiratory delay (243 ± 109 vs. 461 ± 181 ms, p < 0.005).

CONCLUSIONS

An optimized set-up for helmet NIV that limits device compliance and ventilator circuit resistance as much as possible is highly effective in improving pressure support delivery and patient-ventilator interaction.

Continuous positive airway pressure delivered with a "helmet": effects on carbon dioxide rebreathing.

Taccone P, Hess D, Caironi P, Bigatello LM. Continuous positive airway pressure delivered with a "helmet": effects on carbon dioxide rebreathing. Crit Care Med. 2004;32(10):2090-2096. doi:10.1097/01.ccm.0000142577.63316.c0



OBJECTIVE

The "helmet" has been used as a novel interface to deliver noninvasive ventilation without applying direct pressure on the face. However, due to its large volume, the helmet may predispose to CO2 rebreathing. We hypothesized that breathing with the helmet is similar to breathing in a semiclosed environment, and therefore the PCO2 inside the helmet is primarily a function of the subject's CO2 production and the flow of fresh gas through the helmet.

DESIGN

Human volunteer study.

SETTING

Laboratory in a university teaching hospital.

SUBJECTS

Eight healthy volunteers.

INTERVENTIONS

We delivered continuous positive airway pressure (CPAP) with the helmet under a variety of ventilatory conditions in a lung model and in volunteers.

MEASUREMENTS AND MAIN RESULTS

Gas flow and CO2 concentration at the airway were measured continuously. End-tidal PCO2, CO2 production, and ventilatory variables were subsequently computed. We found that a) when CPAP was delivered with a ventilator, the inspired CO2 of the volunteers was high (12.4 +/- 3.2 torr [1.7 +/- 0.4 kPa]); b) when CPAP was delivered with a continuous high flow system, inspired CO2 of the volunteers was low (2.5 +/- 1.2 torr [0.3 +/- 0.2 kPa]); and c) the inspired CO2 calculated mathematically for a semiclosed system model of CO2 rebreathing was highly correlated with the values measured in a lung model (r = .97, slope = 0.92, intercept = -1.17, p < .001) and in the volunteers (r = .94, slope = 0.96, intercept = 0.90, p < .001).

CONCLUSIONS

a) The helmet predisposes to CO2 rebreathing and should not be used to deliver CPAP with a ventilator; b) continuous high flow minimizes CO2 rebreathing during CPAP with the helmet; and c) minute ventilation and Pco2 should be monitored during CPAP with the helmet.

Helmet with specific settings versus facemask for noninvasive ventilation.

Vargas F, Thille A, Lyazidi A, Campo FR, Brochard L. Helmet with specific settings versus facemask for noninvasive ventilation. Crit Care Med. 2009;37(6):1921-1928. doi:10.1097/CCM.0b013e31819fff93



OBJECTIVE

To compare the physiologic effects of noninvasive pressure-support ventilation (NPSV) delivered by a facemask, a helmet with the same settings, and a helmet with specific settings. Inspiratory muscle effort, gas exchange, patient-ventilator synchrony, and comfort were evaluated.

DESIGN

Prospective crossover study.

SETTING

A 13-bed medical intensive care unit in a university hospital.

PATIENTS

Eleven patients at risk for respiratory distress requiring early NPSV after extubation.

INTERVENTION

One hour after extubation, three 20-minute NPSV periods were delivered in a random order by facemask, helmet, and helmet with 50% increases in both pressure support and positive end-expiratory pressure and with the highest pressurization rate (95% max).

MEASUREMENTS AND MAIN RESULTS

Flow and airway, esophageal, and gastric pressure signals were measured under the three NPSV conditions and during spontaneous breathing. Compared with the facemask, the helmet with the same settings resulted in a greater inspiratory muscle effort, but this difference was abolished by the specific settings (pressure-time product in cm H2O.s.min, 63.8 [27.3-85.9], 81.8 [36.0-111.5], and 58.0 [25.4-79.5], respectively, p < 0.05, compared with 209.3 [29.8-239.6] during spontaneous breathing). Compared with the facemask, the helmet with the same settings worsened patient-ventilator synchrony, as indicated by longer triggering-on and cycling-off delays (0.14 [0.11-0.20] seconds vs. 0.32 [0.26-0.43] seconds, p < 0.05; and 0.20 [0.08-0.24] seconds vs. 0.27 [0.25-0.35] seconds, p < 0.01, respectively). The specific settings significantly improved the triggering-on delay compared with the helmet without specific settings (p < 0.01). Tolerance was the same with the three methods.

CONCLUSIONS

Our results suggest that increasing both the pressure-support level and positive end-expiratory pressure and using the highest pressurization rate may be advisable when providing NPSV via a helmet.

More awareness is needed for severe acute respiratory syndrome coronavirus 2019 transmission through exhaled air during non-invasive respiratory support: experience from China.

Guan L, Zhou L, Zhang J, Peng W, Chen R. More awareness is needed for severe acute respiratory syndrome coronavirus 2019 transmission through exhaled air during non-invasive respiratory support: experience from China. Eur Respir J. 2020;55(3):2000352. Published 2020 Mar 20. doi:10.1183/13993003.00352-2020

New treatment of acute hypoxemic respiratory failure: noninvasive pressure support ventilation delivered by helmet--a pilot controlled trial.

Antonelli M, Conti G, Pelosi P, et al. New treatment of acute hypoxemic respiratory failure: noninvasive pressure support ventilation delivered by helmet--a pilot controlled trial. Crit Care Med. 2002;30(3):602-608. doi:10.1097/00003246-200203000-00019



OBJECTIVE

To assess the efficacy of noninvasive pressure support ventilation (NPSV) using a new special helmet as first-line intervention to treat patients with hypoxemic acute respiratory failure (ARF), in comparison to NPSV using standard facial mask.

DESIGN AND SETTING

Prospective clinical pilot investigation with matched control group in three intensive care units of university hospitals.

PATIENTS AND METHODS

Thirty-three consecutive patients without chronic obstructive pulmonary disease and with hypoxemic ARF (defined as severe dyspnea at rest, respiratory rate >30 breaths/min, PaO2:FiO2 < 200, and active contraction of the accessory muscles of respiration) were enrolled. Each patient treated with NPSV by helmet was matched with two controls with ARF treated with NPSV via a facial mask, selected by simplified acute physiologic score II, age, PaO2/FiO2, and arterial pH at admission. Primary end points were the improvement of gas exchanges, the need for endotracheal intubation, and the complications related to NPSV.

RESULTS

The 33 patients and the 66 controls had similar characteristics at baseline. Both groups improved oxygenation after NPSV. Eight patients (24%) in the helmet group and 21 patients (32%) in the facial mask group (p = .3) failed NPSV and were intubated. No patients failed NPSV because of intolerance of the technique in the helmet group in comparison with 8 patients (38%) in the mask group (p = .047). Complications related to the technique (skin necrosis, gastric distension, and eye irritation) were fewer in the helmet group compared with the mask group (no patients vs. 14 patients (21%), p = .002). The helmet allowed the continuous application of NPSV for a longer period of time (p = .05). Length of stay in the intensive care unit, intensive care, and hospital mortality were not different.

CONCLUSIONS

NPSV by helmet successfully treated hypoxemic ARF, with better tolerance and fewer complications than facial mask NPSV.

Non-invasive ventilation in chronic obstructive pulmonary disease patients: helmet versus facial mask.

Navalesi P, Costa R, Ceriana P, et al. Non-invasive ventilation in chronic obstructive pulmonary disease patients: helmet versus facial mask. Intensive Care Med. 2007;33(1):74-81. doi:10.1007/s00134-006-0391-3



RATIONALE

The helmet is a new interface with the potential of increasing the success rate of non-invasive ventilation by improving tolerance.

OBJECTIVES

To perform a physiological comparison between the helmet and the conventional facial mask in delivering non-invasive ventilation in hypercapnic patients with chronic obstructive pulmonary disease.

METHODS

Prospective, controlled, randomized study with cross-over design. In 10 patients we evaluated gas exchange, inspiratory effort, patient-ventilator synchrony and patient tolerance after 30 min of non-invasive ventilation delivered either by helmet or facial mask; both trials were preceded by periods of spontaneous unassisted breathing.

MEASUREMENTS

Arterial blood gases, inspiratory effort, duration of diaphragm contraction and ventilator assistance, effort-to-support delays (at the beginning and at the end of inspiration), number of ineffective efforts, and patient comfort.

MAIN RESULTS

Non-invasive ventilation improved gas exchange (p<0.05) and inspiratory effort (p<0.01) with both interfaces. The helmet, however, was less efficient than the mask in reducing inspiratory effort (p<0.05) and worsened the patient-ventilator synchrony, as indicated by the longer delays to trigger on (p<0.05) and cycle off (p<0.05) the mechanical assistance and by the number of ineffective efforts (p<0.005). Patient comfort was no different with the two interfaces.

CONCLUSIONS

Helmet and facial mask were equally tolerated and both were effective in ameliorating gas exchange and decreasing inspiratory effort. The helmet, however, was less efficient in decreasing inspiratory effort and worsened the patient-ventilator interaction.

High flow biphasic positive airway pressure by helmet--effects on pressurization, tidal volume, carbon dioxide accumulation and noise exposure.

Moerer O, Herrmann P, Hinz J, et al. High flow biphasic positive airway pressure by helmet--effects on pressurization, tidal volume, carbon dioxide accumulation and noise exposure. Crit Care. 2009;13(3):R85. doi:10.1186/cc7907



INTRODUCTION

Non-invasive ventilation (NIV) with a helmet device is often associated with poor patient-ventilator synchrony and impaired carbon dioxide (CO2) removal, which might lead to failure. A possible solution is to use a high free flow system in combination with a time-cycled pressure valve placed into the expiratory circuit (HF-BiPAP). This system would be independent from triggering while providing a high flow to eliminate CO2.

METHODS

Conventional pressure support ventilation (PSV) and time-cycled biphasic pressure controlled ventilation (BiVent) delivered by an Intensive Care Unit ventilator were compared to HF-BiPAP in an in vitro lung model study. Variables included delta pressures of 5 and 15 cmH2O, respiratory rates of 15 and 30 breaths/min, inspiratory efforts (respiratory drive) of 2.5 and 10 cmH2O) and different lung characteristics. Additionally, CO2 removal and noise exposure were measured.

RESULTS

Pressurization during inspiration was more effective with pressure controlled modes compared to PSV (P < 0.001) at similar tidal volumes. During the expiratory phase, BiVent and HF-BiPAP led to an increase in pressure burden compared to PSV. This was especially true at higher upper pressures (P < 0.001). At high level of asynchrony both HF-BiPAP and BiVent were less effective. Only HF-BiPAP ventilation effectively removed CO2 (P < 0.001) during all settings. Noise exposure was higher during HF-BiPAP (P < 0.001).

CONCLUSIONS

This study demonstrates that in a lung model, the efficiency of NIV by helmet can be improved by using HF-BiPAP. However, it imposes a higher pressure during the expiratory phase. CO2 was almost completely removed with HF-BiPAP during all settings.

Exhaled air dispersion during noninvasive ventilation via helmets and a total facemask.

Hui DS, Chow BK, Lo T, et al. Exhaled air dispersion during noninvasive ventilation via helmets and a total facemask. Chest. 2015;147(5):1336-1343. doi:10.1378/chest.14-1934



BACKGROUND

Noninvasive ventilation (NIV) via helmet or total facemask is an option for managing patients with respiratory infections in respiratory failure. However, the risk of nosocomial infection is unknown.

METHODS

We examined exhaled air dispersion during NIV using a human patient simulator reclined at 45° in a negative pressure room with 12 air changes/h by two different helmets via a ventilator and a total facemask via a bilevel positive airway pressure device. Exhaled air was marked by intrapulmonary smoke particles, illuminated by laser light sheet, and captured by a video camera for data analysis. Significant exposure was defined as where there was ≥ 20% of normalized smoke concentration.

RESULTS

During NIV via a helmet with the simulator programmed in mild lung injury, exhaled air leaked through the neck-helmet interface with a radial distance of 150 to 230 mm when inspiratory positive airway pressure was increased from 12 to 20 cm H2O, respectively, while keeping the expiratory pressure at 10 cm H2O. During NIV via a helmet with air cushion around the neck, there was negligible air leakage. During NIV via a total facemask for mild lung injury, air leaked through the exhalation port to 618 and 812 mm when inspiratory pressure was increased from 10 to 18 cm H2O, respectively, with the expiratory pressure at 5 cm H2O.

CONCLUSIONS

A helmet with a good seal around the neck is needed to prevent nosocomial infection during NIV for patients with respiratory infections.

Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19).

Alhazzani W, Møller MH, Arabi YM, et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19). Intensive Care Med. 2020;46(5):854-887. doi:10.1007/s00134-020-06022-5



BACKGROUND

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of a rapidly spreading illness, Coronavirus Disease 2019 (COVID-19), affecting thousands of people around the world. Urgent guidance for clinicians caring for the sickest of these patients is needed.

METHODS

We formed a panel of 36 experts from 12 countries. All panel members completed the World Health Organization conflict of interest disclosure form. The panel proposed 53 questions that are relevant to the management of COVID-19 in the ICU. We searched the literature for direct and indirect evidence on the management of COVID-19 in critically ill patients in the ICU. We identified relevant and recent systematic reviews on most questions relating to supportive care. We assessed the certainty in the evidence using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach, then generated recommendations based on the balance between benefit and harm, resource and cost implications, equity, and feasibility. Recommendations were either strong or weak, or in the form of best practice recommendations.

RESULTS

The Surviving Sepsis Campaign COVID-19 panel issued 54 statements, of which 4 are best practice statements, 9 are strong recommendations, and 35 are weak recommendations. No recommendation was provided for 6 questions. The topics were: (1) infection control, (2) laboratory diagnosis and specimens, (3) hemodynamic support, (4) ventilatory support, and (5) COVID-19 therapy.

CONCLUSION

The Surviving Sepsis Campaign COVID-19 panel issued several recommendations to help support healthcare workers caring for critically ill ICU patients with COVID-19. When available, we will provide new recommendations in further releases of these guidelines.