Hemodynamic Responses to Ventilator Hyperinflation Technique

The World Health Organization reported that Thailand ranked third for number of road fatalities at 38.1 per 100,000 inhabitants in 2010. Most of these cases were admitted to the intensive care unit (ICU) for respiratory interventions such as intubation and mechanical ventilation that can lead to a common problem of pulmonary complications such as pneumonia and atelectasis.

Evidence supports the effectiveness of chest physical therapy technique (CPT) to improve alveolar collapse and remove pulmonary secretion. A previous study has shown that the positive airway pressure technique reduced work of breathing (WOB) and re-inflated lung atelectasis. The use of positive pressure devices has been part of physiotherapy intervention since intermittent positive pressure breathing was introduced in clinical practice. In intensive care settings, the use of positive pressure by physiotherapists includes manual hyperinflation (bagging or bag squeezing), which has been shown to increase oxygenation and mobilize excessive bronchial secretions, and to re-inflate collapsed areas.

Manual hyperinflation technique (MHI) is provided for use in patients with lung atelectasis. Several studies demonstrated the short-term effects of increased oxygenation and pulmonary compliance, improved lung collapse, and removed pulmonary secretions. To apply MHI technique, patients were disconnected from the ventilator which lead to the adverse effect of losing positive end expiratory pressure (PEEP) corresponding to loss of functional residual capacity, decreased oxygenation, and shear stress of distal lung units.

An alternative method of performing pulmonary hyperinflation uses the mechanical ventilator. Although there is evidence that positive pressure interventions such as continuous positive airway pressure (CPAP) and intermittent positive pressure breathing IPPB) can improve lung expansion and mobilize secretions in the airway, there are few studies examining ventilator-induced hyperinflation as a physiotherapy intervention in intensive care.

A previous study showed that the ventilator hyperinflation technique (VHI) was as effective as MHI to improve pulmonary complications such as secretion retention and lung atelectasis. Especially, VHI technique using applied by the mechanical ventilator, patient was not disconnected from the ventilator and therefore did not result in loss of PEEP and its adverse effect.

Atelectasis is a common pulmonary complication in acute trauma patients maintained on ventilator support who would benefit from VHI but even though recent studies indicate that VHI technique is an improvement on the MHI technique there are relatively few study of the hemodynamic responses to VHI. There is controversy in hemodynamic responses to VHI, Ventilator hyperinflation technique (VHI) is especially valuable in treating patients in the ICU because other techniques such as percussion and postural drainage may not be possible because of wounds, broken bones or surgical drains. However, the technique is very rarely used by physical therapists in the ICU, possibly because they are concerned that increasing in the intra-thoracic pressure by uses VHI to inflate lung will result in dangerous changes in heart rate and blood pressure; that any such changes may persist after the treatment leading to complications such as pulmonary edema and, lastly, the positive pressure to the patient may precipitate episodes of cardiac arrhythmia.

Recent study demonstrated that heart rate and blood pressure were changed after VHI in ICU patients but the condition of patients in their study were mixed, not only traumatic patients. Previous study showed that basal heart and blood pressure were increased in patients underwent traumatic conditions. The hemodynamic responses to VHI were required for safety and increasing physiotherapist's confidences to use this technique in ICU. Therefore, the purpose of this study is to explore acute hemodynamic responses to VHI technique in critical traumatic patients with pulmonary complications in the intensive care unit.