REPOBLACIONES DE OTRAS CONÍFERAS

The physiotherapist must understand intra- cranial dynamics and the effect of physiotherapy in order to assess accurately and treat effectively. The following factors should be considered: • conscious level, as measured on the Glasgow

Coma Scale (GCS)

• pupil response before and after intervention • vital signs including ICP, SABP and CPP and

how these are influenced by turning, pressure relief and oral hygiene procedures.

Prior to physiotherapy, sedation or painkillers may be given. The timing of the drug adminis- tration is vital and close liaison with the nursing staff is essential.

Suctioning

Suction is a necessary adjunct to ventilator ther- apy. It ensures airway patency, removes pul- monary secretions and promotes ventilatory exchange (Brucia & Rudy 1996, Kerr et al 1997). Suction causes a progressive increase in ICP with each insertion of the suction catheter. In most patients, elevations in ICP are transient and return to baseline level within minutes (Kerr et al 1998). Induced hypercapnia and hypoxia may cause ICP to rise during suction (Chudley 1994).

While coughing assists with removal of secre- tions, increased intrathoracic pressure reduces cerebral venous return and increases CBV and ICP (Wainwright & Gould 1996, Kerr et al 1998).

Findings from several studies show that increased ICP during suctioning occurs due to direct tracheal stimulation (Brucia & Rudy 1996, Fisher et al 1982). Transient increases in ICP result from direct carina stimulation but a sus- tained rise in ICP is due to the increase in ITP associated with coughing. Patients with reduced intracranial compliance have the most pro- nounced elevations in ICP on suctioning and are less able to tolerate these elevations. Care must be taken when suctioning patients with an ICP above 20 mmHg (Kerr et al 1998).

Considerations when suctioning

• Hyperoxygenation, for example, 100% Oz for

2 minutes prior to suctioning, minimises tran- sient periods of hypoxia and hypercapnia (Rudy et al 1986, Chudley 1994, Kerr et al 1997). • Crosby & Parsons (1992) recommend at least

60 seconds of manual hyperventilation between each suction with 2 minutes undisturbed rest to allow ICP, MAP and CPP to return to baseline. • Disconnection from the ventilator during

suctioning causes a rapid drop in ITP and sudden loss of PEEP. A reduction in ICP, due to an increase in cerebral venous return, or an increase in ICP,_due to abrupt elevations of the SABP, may result. Disconnection may also cause hypoxia, resulting in cerebral vaso- dilation (Kerr et al 1993, Imle et al 1997). Suctioning via a port adaptor on the catheter mount, or using a closed suction circuit is therefore recommended. Suction should not exceed 10-15 seconds (Kerr et al 1993).

• The catheter should pass beyond the endo- tracheal tube (ETT) but not contact the carina to minimise irritant receptor stimulation. The ETT must be stabilised to avoid any unnecess- ary tracheal stimulation (Kerr et al 1993, Brucia & Rudy 1996)

• Suction passes should be limited to a maxi- mum of 2-3 (Garradd & Bullock 1986, Rudy et al 1991, Kerr et al 1993, Arbour 1998).

• Suction pressure should be high enough to remove secretions but not reduce functional residual capacity or cause tracheal mucosal trauma: 120 mmHg pressure is recommended (Kerr et al 1993).

• The external diameter of the catheter should not exceed half the internal diameter of the ETT to minimise the changes in airway resist- ance and negative pressure (George 1983, Young 1984).

• Intratracheal or intravenous lignocaine may be used to blunt ICP responses to suctioning (Rudy et al 1986).

• Neuromuscular blocking agents suppress the cough reflex and induce paralysis of the inter- costal muscles and diaphragm, increasing chest wall compliance. This may be respons- ible for the attenuation of expected increases in ICP occurring during suction (Kerr et al 1998). Suctioning usually increases ICP but the MAP may also increase. It therefore follows that what may be a dangerous increase in ICP may be offset by a rise in MAP maintaining an adequate CPP. Suctioning should only be performed when clinically indicated (Wainwright & Gould 1996, Imle et al 1997).

Manual hyperinflation

Manual hyperinflation (MH) provides artificial ventilation by means of a rebreathing (Water's) or non-rebreathing (Ambu) bag attached to an oxygen source. The aim is to mobilise and assist the clearance of excess bronchial secretions, to increase lung volumes and re-expand areas of lung collapse (Pryor & Webber 1998).

A larger tidal volume is delivered, producing an increase in ITP, which leads to a reduction in cerebral venous return and increase in CBV and ICP (Snyder 1983, Imle et al 1997). If the SABP is low, the induced increase in ITP reduces systemic venous return, lowering the cardiac output, further lowering the SABP and compromising the CPP (Ersson et al 1990, Prasad & Tasker 1990). If SABP is high, MH can increase it to a critical level (Ada et al 1990). The increased levels of PaOz induced by MH may have a slight vaso-

constrictive effect on the cerebral vasculature, reducing the CBV and ICP (Rudy et al 1991, Kerr & Brucia 1993). Hyperinflation should be inter- spersed with short-duration hyperventilation to lower P a C 02 prior to or following suction (Kerr

et al 1997). Application of MH should be brief, as ICP may increase over time (Garradd & Bullock 1986, Paratz & Burns 1993).

Manual techniques

Shaking and vibrations. These are intermittent coarse or fine compressions of the chest wall during expiration, usually combined with MH. They augment the expiratory flow and facilitate large and small airway clearance by mobilising and advancing secretions (Ciesla 1989, Pryor & Webber 1998). Manual techniques with shaking may increase ICP over time; vibrations in isola- tion have no effect on ICP (Prasad & Tasker 1990, Imle et al 1997).

Chest clapping. These are slow rhythmical movements of the cupped hands over affected lung segments to mobilise secretions (Pryor & Webber 1998). Chest clapping does not adversely affect ICP and may even lower it (Garradd & Bullock 1986, Paratz & Burns 1993, Imle et al 1997).

Positioning

Patients with high ICP should be nursed in 30 degrees head and trunk elevation as this increases cerebral venous return and lowers ICP, without a significant decrease in CBF (Brimioulle et al 1997). Head elevations above 30 degrees may cause a decrease in SABP, which may com- promise the CPP (March et al 1990, Imle et al 1997, Simmons 1997). The head and trunk should be in alignment, as neck flexion and rotation may increase ICP by compressing the internal jugular vein (Williams & Coyne 1993, Chudley 1994).

Postural drainage is a means of positioning that enables gravity to assist the clearance of bronchial secretions. Positions such as a head down tilt may cause an increase in ICP; however, they can be performed safely when strict guide- lines are followed and effects of treatment care- fully monitored (Lee 1989, Imle et al 1997).

Turning patients into side-lying may increase ICP, with only small changes in CPP (Mitchell et al 1981, Lee 1989, Rising 1993). If the baseline ICP is less than 15 mmHg and the CPP is greater than 50 mmHg, it is considered safe to turn the patient with TBI (Parsons & Shogan 1984). Hip flexion greater than 90 degrees limits venous drainage and will increase ICP (Arbour 1998).

In summary:

• Patients' positioning is individually deter- mined by ICP, SABP and CPP (March et al 1990, Simmons 1997).

• Care should be taken with cervical collars and ETT ties: if too tight, these may impair cerebral venous drainage (Arbour 1998).

• Adequate time should be given to allow ICP to return to baseline (Chudley 1984). The cumu- lative effect of increased ICP is a major deter- mining factor in prognosis (Shalit & Umansky 1977).

Passive movements

Passive movements to monitor range of motion and assess muscle tone are performed routinely on patients in intensive care units. They can be performed safely on patients with normal or elevated levels of ICP (Brimioulle et al 1997). Stereotyped patterns of hypertonus, producing isometric contractions with pressure of the feet against a foot board, are associated with eleva- tions in ICP (Andrus 1991).

Conclusion

Physiotherapy usually increases ICP, but the positive benefits often outweigh the transient increase. Cerebral perfusion pressure may remain unchanged due to a corresponding increase in the SABP (Garradd & Bullock 1986, Paratz & Burns 1993). The decision whether or not to treat must be made in conjunction with the nursing and medical staff.

Physiotherapists have a role to play in the pre- vention of secondary brain damage, which may result from hypoxia or hypercapnia arising from respiratory dysfunction. It is essential that

physiotherapists understand the relationship between brain and lung function, intracranial dynamics and how all aspects of physiotherapy are integrated with intracranial physiology.

RESPIRATORY MUSCLE