What are the principles, expected benefits, risks, and points for attention of the different CPT techniques used in MV patients?

In all studies, the CPT arm consisted of various combinations of body positioning, chest wall vibration or compression, and manual lung hyperinflation. One study used IPV-ADD as CPT in one of the comparator arms. Control patients mostly received standard nursing care and airway suctioning.

All CPT techniques aimed to dislodge secretions and to facilitate their transport in and removal from the airways. Body positioning and chest mobilization included frequent posture changes, maintenance of a 30° upright position most of the time, in-bed rotations, proper chest alignment, and passive range-of-motion limb exercises. Another major CPT goal was to improve gas exchange and oxygenation by enhancing alveolar ventilation, augmenting ventilation/perfusion matching, and redistributing body fluid on a gravitational basis. Standardized protocols for chest mobilization, however, do not exist. Manual lung hyperinflation (aka “bagging” or “bag-squeezing”) promotes alveolar recruitment by delivering larger than baseline and peak pressure-limited tidal volumes, thereby enhancing lung compliance and gas exchange. It is also suggested that it mimics a cough so that airway secretions are mobilized towards the larger airways. IPV physiotherapy creates a convective gas front to the distal airways by delivering very small bursts of tidal volume within a frequency range of 60 to 600 cycles/minute. As such, temporary alveolar recruitment and ventilation is provided while mucus is cleared from middle-sized airways and propelled cephalad by generating peak expiratory flows that largely exceed inspiratory flows. The effect of IPV is enhanced by adding ADD whereby secretions are loosened and collected at low to mid lung volumes and subsequently expelled by the IPV expiratory flow. IPV was found to be as effective as “standard care” CPT for improving lung function and enhancing sputum expectoration in ambulatory older children and adults with cystic fibrosis. ICU patients thought to benefit from IPV are those with relapsing atelectasis, “copious” secretions, or inhalation injury.

As long as the patient’s hemodynamic and respiratory parameters are stable before the start of CPT, all manual techniques can be safely applied. Intensive chest mobilization may occasionally be complicated by endotracheal tube or intravascular catheter disconnection, hemodynamic intolerance, increased intracranial pressure, and cardiac arrhythmias. Manual hyperinflation and IPV physiotherapy involve disconnecting the patient from the ventilator. Both techniques might significantly interfere with currently used sedation and ventilation protocols and methods (e.g. low level sedation, sedation breaks, gas anesthesia, low tidal volume/high PEEP ventilation, …). Possible physiological side effects of delivered air volume, flow rates and airway pressure must be carefully considered. IPV, in particular, is expensive and handling requires good knowledge of respiratory (patho) physiology because the patient is placed on a dedicated “high-frequency ventilator” device. Driving pressure must be set appropriately and adapted to the patient’s chest excursion. During IPV physiotherapy, the patient’s heart rate, respiratory rate, blood pressure, pulse oximetry and end-tidal CO₂ must be observed closely for signs of intolerance. Supplemental oxygen must be provided if needed. To minimize the risk of barotrauma, a pressure pop off must be utilized and peak airway pressures carefully monitored. Performing IPV on a 24/7 basis is labor-intensive and necessitates a skilled physiotherapist team operating under close supervision of ICU physicians.

CPT-induced changes in the patient’s general, hemodynamic or respiratory condition must be immediately notified and anticipated conveniently. Specific contra-indications for any form of CPT are undrained pneumothorax, shock or severe hemodynamic instability, recent pulmonary surgery, hemoptysis or active pulmonary hemorrhage, unstable chest wall (e.g. multiple rib or vertebral fractures), acute bronchospasm, and increased intracranial pressure.