Biphasic Cuirass Ventilation (BCV) is a plastic chest cuirass shell that uses a pressure source capable of providing both positive and negative pressure. BCV supports spontaneous breathing in a more physiological manner compared with positive pressure ventilation. Following the natural breathing pattern outlined in Boyle’s Law, the BCV uses negative pressure to cause extrathoracic expansion, decreasing the alveolar pressure, creating a gradient for air to move. Utilizing negative pressure with multiple modes, the BCV has a varied range of pathologies that it can treat. The Biphasic portion is a two phase system that allows for subatmospheric cuirass pressure for inhalation, while exhalation can maintain a positive pressure for alveolar recruitment.
Poliomyelitis is over so why bring up BCV now?
Alternative application and therapy may be applicable to current day scenarios. Patients on HFNC still in a hypoxic state with secondary atelectatic issues may benefit from continuous negative external chest pressure (CNECP). CNECP is known to increase FRC while maintaining or in some cases improving cardiac output. CNECP mode maintains a continuous negative pressure during both inspiration and expiration. The continuous pull produces an effective inflation of the lung throughout the breath cycle without hemodynamic compromise. This steady state of negative pressure has been shown to increase stroke volume and cardiac index while reducing wedge pressures. CNECP in conjunction with the patient’s current oxygen therapy has shown an increase in oxygenation with the ability to wean FiO2. Weaning from CNECP is done by conducting stand by trials with clinical assessments. CNECP’s goal is alveolar recruitment without the risk of positive pressure therapy.
BCV also has ventilation modes that use an inspiratory pressure and expiratory pressure for increased thoracic mobility and improved minute ventilation. These ventilation modes can vary based on patient comfort and need. The control mode will give a mandatory respiratory rate while triggered mode can either be through the cuirass or through the airway tube placed at or near the patient’s airway. Respiratory synchronization mode fully synchronizes with the patient’s own respiration, automatically adjusting to the patient’s demand. Intermittent use of BCV has been shown to reduce muscle fatigue in patients with respiratory distress. Lessening the load on the respiratory muscles while simultaneously increasing tidal volume is thought to decrease the need for endotracheal intubation. If the patient is hypoxic they will need a source of oxygen therapy. This intermittent approach uses the BCV as a therapeutic respiratory therapy. Application of this therapy for 60 minutes showed an increase of maximum inspiratory pressure, maximum expiratory pressure, vital capacity, arterial oxygen tension, pH and a decrease of residual volume, total lung capacity of and arterial carbon dioxide tension. BCV has also been shown to decrease cardiac load to reduce excess work of breathing associated with chronic lung disease patients and decreased serum NT-proBNP. BCV intermittent sessions for two weeks were also studied in patients with pulmonary hypertension (PH) caused by chronic lung disease, significantly decreased mPAP was seen after two weeks of therapy.
BCV has a diverse portfolio, ranging from neonate to adults. Its use can be continuous or intermittent therapy. Novel approaches have been studied, always concluding more studies are needed but benefits were seen. BCV definitely has a role in respiratory therapy with many possibilities. One may need to take a fresh look at this old technology, especially with this new healthcare landscape.
- BCV utilizes negative pressure in various modes to improve lung function.
- BCV has been shown to decrease respiratory muscle fatigue while improving minute ventilation
- BCV has been shown to improve cardiac output and decrease mPAP
*Frequent assessment of the patient’s skin is necessary for long term use. It should also be noted that a cloth barrier should be placed between the patient and cuirass.
- Grasso, F., Engelberts, D., Helm, E., Frndova, H., Jarvis, S., Talakoub, O., McKerlie, C., Babyn, P., Post, M., & Kavanagh, B. P. (2008). Negative-pressure ventilation: Better oxygenation and less lung injury. American Journal of Respiratory and Critical Care Medicine, 177(4), 412– 418. https://doi.org/10.1164/rccm.200707-1004OC
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- Glérant JC, Jounieaux V, Parreira VF, Dury M, Aubert G, Rodenstein DO. Effects of intermittent negative pressure ventilation on effective ventilation in normal awake subjects. Chest. 2002 Jul;122(1):99-107. doi: 10.1378/chest.122.1.99. PMID: 12114344.
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