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Critical Care and Trauma: Case Report

Helmet Ventilation for Acute Respiratory Failure and Nasal Skin Breakdown in Neuromuscular Disorders

Racca, Fabrizio MD*; Appendini, Lorenzo MD; Berta, Giacomo MD*; Barberis, Luigi MD*; Vittone, Ferdinando MD*; Gregoretti, Cesare MD; Ferreyra, Gabriela RT*; Urbino, Rosario MD*; Ranieri, V Marco MD*

Author Information
doi: 10.1213/ane.0b013e3181a1f708

Noninvasive ventilation (NIV) has been successfully used to support patients with Duchenne-type muscular dystrophy (DMD).1 However, NIV applied by mask often fails when high levels of support and/or long periods of ventilation are required to manage acute respiratory failure (ARF).2,3

A helmet may be an effective interface to deliver NIV in patients with ARF, avoiding skin breakdown and optimizing comfort.4 However, data suggest that noninvasive pressure support ventilation (N-PSV) delivered by helmet may worsen the patient–ventilator interaction compared with standard masks, eventually leading to NIV failure.5

We describe the drawbacks and a possible solution for two DMD patients with ARF and nasal ulceration treated with helmet ventilation.


Case 1

A 19-yr-old DMD patient on long-term nocturnal nasal NIV was admitted to the emergency room with severe septic shock. In a couple of hours, he was transferred to the intensive care unit (ICU), where he was tracheally intubated and his lungs mechanically ventilated (Evita4 ventilator, Draeger, Lubeck, Germany).

Six days later his trachea was extubated and mask N-PSV 24 h/d was initiated, using the same ICU ventilator with the leak compensation facility switched on. His arterial blood gases (ABGs) remained satisfactory (Table 1). Two different types of nasal mask, a Profile Lite nasal gel mask (Respironics, PA) and a Mirage nasal mask (ResMed, Australia), were alternated. A barrier dressing (a hydrocolloid sheet) was used to reduce the risk of skin breakdown. The masks were secured to avoid air leaks although allowing enough space to pass two fingers beneath the head strap.

Table 1:
Ventilator Modes, Ventilator Settings, and Arterial Blood Gases in One of the Patients (Case 1) Over Time

Four days later the patient developed nasal ulceration. Various interfaces were tried (nasal pillows, full face mask, and mouthpiece), and a bilevel ventilator (BiPAPVision—Respironics, Murrysville, PA) replaced the ICU ventilator without any success in terms of patient tolerance to mechanical ventilation. Subsequently, N-PSV was applied via a helmet interface (CaStar“R” StarMed, Italy). With this setting (Table 1) the patient showed poor clinical tolerance to helmet N-PSV, severe dyspnea and paradoxic respiratory motion.

Several ineffective efforts were also disclosed by the simultaneous analysis of airway opening pressure (Pao) and respiratory inductive plethysmography (RIP) (RespitracePlus, NIMS, FL) tracings (Fig. 1). This occurred despite the fact that the ventilator (Evita4 ventilator) was set at the highest trigger sensitivity that did not induce auto-triggering. The Evita4 ventilator was switched to BIPAP set with the same inspiratory-expiratory pressures used during N-PSV, with respiratory rate (RR) and inspiratory time (TI) set as close as possible to the patient’s RR and timing (Table 1) as measured during a helmet continuous positive airway pressure (CPAP) trial. With these ventilator settings, dyspnea, patient-ventilator synchrony (Fig. 1), and ABGs improved (Table 1).

Figure 1.:
Experimental record from patient 1. Airway opening pressure (Pao), ribcage (RC), abdomen (AB), and respiratory inductive plethysmography (RIP) tidal volume (VT) signals during helmet pressure support ventilation (PSV) and biphasic positive airway pressure (BIPAP) are shown. Respiratory pattern, ribcage–abdominal motion and major patient–ventilator asynchrony were measured by means of simultaneous recording of RIP (RespitracePlus, NIMS, FL) and Pao. Pao was measured at the helmet inspiratory port with a differential transducer (Digima-Clic, ±100 cm H2O, Special Instruments, Germany). Vt was reported in arbitrary units. All signals were collected on a personal computer through a 12-bit analog-to-digital converter (National Instrument DAQCard 700; TX) at a sampling rate of 200 Hz (ICU-lab, KleisTEK Engineering, Bari, Italy). The horizontal dashed line indicates the nominal inspiratory pressure level delivered by the ventilator. T I is the inspiratory time. During BIPAP, most of the mechanical breaths were not triggered by the patient (VT begins after start of mechanical assistance). The percentage of ventilator inspiratory assistance, defined as the percentage of T I spent at nominal pressure level (time elapsed between the first and the second vertical dashed lines), is greater during BIPAP than during PSV. Ineffective efforts (VT without any mechanical assistance identified by arrows), associated with paradoxical AB motion, are prevalent during PSV.

The patient was kept on helmet ventilation for 8 days until the nasal ulceration healed and the ABGs were stable. Eighteen days after admission to the ICU he was returned to nocturnal nasal NIV, and 3 days later he was discharged to the neurological ward. The patient was eventually discharged from the hospital and is living at home on nasal N-PSV.

Case 2

An 18-yr-old DMD patient on long-term nocturnal nasal NIV was admitted comatose to the emergency room with decompensated respiratory acidosis. He was immediately transferred to the ICU, where he was tracheally intubated and his lungs mechanically ventilated for 48 h.

After improvement in ABGs, the patient’s trachea was extubated and he was switched to mask ventilation. Two different types of nasal mask and a hydrocolloid sheet were used to reduce the risk of skin breakdown. His ABGs remained satisfactory (pH 7.35, Pao2/fraction of inspired oxygen [Fio2] 275, Paco2 52 mm Hg). However, the patient failed N-PSV after 72 h because of nasal ulceration.

A ventilator strategy similar to that used in Case 1 was attempted, without any success in terms of patient tolerance to mechanical ventilation. Next, N-PSV was applied using a helmet interface. The patient showed severe dyspnea, paradoxic respiratory motion, and several ineffective efforts. Subsequently, the ventilator was switched to BIPAP, set at the same inspiratory-expiratory pressures used during N-PSV, with a RR and TI set as close as possible to the patient’s RR and timing (RR 18 min, TI 1.3 s). With these ventilator settings, dyspnea, patient-ventilator synchrony, and ABGs (pH 7.38, Pao2/Fio2 240, Paco2 49 mm Hg) improved.

The patient remained on helmet ventilation for 6 days until skin breakdown healed and his ABGs were stable. Seven days after beginning helmet ventilation he was returned to nocturnal nasal NIV, and 1 wk later he was discharged to the neurological ward. The patient was eventually discharged from the hospital and lived at home on nasal N-PSV. He died 1 yr later because of a primary nonrespiratory cause (abdominal sepsis).


In both clinical cases presented here, we attempted to overcome the nasal mask-related complications that precluded NIV effectiveness by using a helmet interface. The N-PSV irreversible intolerance to conventional ventilator management was successfully treated with helmet ventilation in an assist-controlled (synchronized BIPAP) mode.

We confirm previous reports that the risk of facial lesions and other side effects associated with the use of a standard interface may be increased because of high ventilator dependence in DMD patients with ARF.3 Notwithstanding this risk, our DMD patients were switched early to NIV when they were still completely ventilator-dependent, according to current guidelines and clinical practice,1,6 to decrease the complications associated with tracheal intubation in mechanically ventilated patients. Until the onset of skin lesions, NIV proved to be effective in reversing ARF in both patients (Table 1). Despite efforts made to avoid it, skin breakdown on the nose bridge occurred after 72–96 h of continuous NIV. Thus alternative patient-ventilator interfaces were evaluated in an attempt to avoid invasive mechanical ventilation.

Studies suggest that N-PSV delivered by helmet is better tolerated than N-PSV delivered by conventional masks and is similarly effective in reducing the need for endotracheal intubation.4 These data warranted the choice of helmet ventilation in the two DMD patients.

At first, based on the literature,4 assisted mechanical ventilation in the form of PSV was used with the helmet. In this condition, both patients showed poor patient–ventilator synchrony and several unassisted inspiratory efforts (Fig. 1), despite the fact that the ventilator was set with very high trigger sensitivity. Furthermore, the percentage of inspiratory assistance, defined as % of inspiratory time spent at nominal pressure level,7 was very low, suggesting quite poor respiratory muscle unloading (Fig. 1). In both cases, ABGs could not be measured during helmet PSV because of very severe clinical intolerance to the ventilator mode.

These findings confirm previous reports in the literature showing significant patient–ventilator asynchrony, discomfort and inefficacy in unloading the respiratory muscles during helmet N-PSV as a result of helmet characteristics conflicting with the algorithms governing PSV.5 In particular, the present case report confirms that patients with DMD may be exposed to severe asynchrony during N-PSV.8

Assist-controlled modalities are commonly used in the ICU to assure triggering and cycling of the ventilator in the presence of persistent patient–ventilator asynchrony.6,9 During BIPAP provided by the Evita4 ventilator, a positive pressure breath is delivered regardless of the patient’s trigger capability, TI of the mechanical breaths is preset, and spontaneous breathing is permitted in any phase of the mechanical cycle.10 In our study, to optimize patient–ventilator interactions, TI and RR during BIPAP were matched with those obtained during a helmet CPAP trial. The inspiratory triggering threshold was set at the most sensitive level that did not induce auto-triggering, although pressure rise time was set at the ventilator’s fastest ramp. With these changes, major patient-ventilator asynchrony and the ineffective efforts during synchronized BIPAP mode disappeared, and percentage of inspiratory assistance increased (Fig. 1).

Some technical aspects merit discussion. First, the assessment of patient–ventilator asynchrony requires at least an esophageal catheter system in place to record inspiratory muscle efforts11 or diaphragm recordings12 coupled with flow and Pao tracings. Esophageal catheters to record pressure or diaphragm electromyography and a mouthpiece to record airflow were not used in the two patients presented here because of swallowing dysfunction and dyspnea. As an alternative, we used RIP to detect patient–ventilator asynchrony and tidal volume. According to the criteria used in sleep medicine, ineffective inspiratory efforts were defined as thoracic-abdominal displacements not assisted by the ventilator positive pressure boost (Fig. 1). Second, RIP tracings and Pao were recorded in each patient only during the first hour of helmet ventilation. Subsequently, RR was clinically assessed13 and TI extrapolated from RR assuming an inspiratory- to-expiratory ratio of 1:2. Third, the pathophysiology of ARF can change quite quickly, making NIV assistance inadequate. To avoid ventilator over-assistance or under-assistance, patient RR, and TI were screened daily during a CPAP trial to reset ventilator parameters as close as possible to the patient’s own values. Moreover, a weaning protocol based on progressive airway pressure reduction was implemented.13 This approach allowed nasal lesions to heal and patients to recover quickly from ARF (8 and 6 days, respectively).

In conclusion, the two clinical cases presented and discussed here show that helmet ventilation can be considered to manage intolerance to a nasal mask during NIV in patients with DMD and ARF. However, because difficult triggering and poor patient ventilator synchrony occur during helmet N-PSV, assist pressure-controlled mode may be more indicated to provide helmet ventilation.


The authors would like to thank Michele Mele for his technical support in preparing the manuscript.


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