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API'F:NDIX 111-8: MECHANICAL VENTILATION 825

• T-piece: Breathing off of the ventilator, while still intubated, for

increasing periods of time. This technique is sorr of an all-or-none

method. Patients need to have the respiratory drive to breathe

spontaneously and the capability to generate adequate VT to

atrempt this weaning process. The process aims to improve respirarory muscle strength and endurance with prolonged time periods of independent ventilation.

• PSV: The patient spends periods of time with decreased pressure

sllpporr to increase his or her spontaneous ventilation. Two factors

can be manipulated with PSV: (I) to increase the strength load on

the respiratory muscles, PSV can be reduced, and (2) to increase

the endurance requirement on the respiratory muscles, the length

of time that PSV is reduced can be increased.

Recently, it was demonstrated that the T-piece and PSV methods of

weaning were superior to the IMV or SIMV methods."

Five major factors ro consider during a patient'S wean follow6:

I .

Respiratory demand (the need for oxygen for metabolic

processes and the need to remove carbon dioxide produced during

metabolic processes) and the ability of the neuromuscular system

to cope with the demand

2.

Oxygenation

3.

Cardiovascular performance

4.

Psychological factors

5.

Adequate rest and nutrition

The following are signs of increased distress during a ventilator

wean3.6:

• Increased tachypnea (more than 30 breaths per minute)

• Drop in pH to less than 7.25-7.30 associated with an increasing

Paco2

• Paradoxical breathing pattern (refers to a discoordination in

movements of the abdomen and thorax during inhalation) (Refer

to Chapter 2.)

• Oxygen saturation as measured by pulse oximetry less than 900/0

826 AClITE CARE HANDBOOK FOR I'HYSICAL THERAPISTS

• Change in heart rate of more than 20 beats per minute

• Change in blood pressure more than 20 mm Hg

• Agitation, panic, diaphoresis, cyanosis, angina, arrhythmias

Physical Therapy Considerations

A patient who is mechanically ventilated may require ventilatory sup

POrt for a prolonged period of time. Patients who require prolonged

ventilatory support are at risk for developing pulmonary complications, skin breakdown, joint conrractures, and deconditioning from bed rest. Physical therapy intervention, including bronchopulmonary

hygiene and functional mobiliry training, can help prevent or reverse

these complications despite mechanical ventilation.

Bronchopulmonary Hygiene

Patients on ventilatory support are frequently suctioned as parr of

their routine care. Physical therapists working with patients on their

bronchopulmonary hygiene and airway clearance should use suctioning as the last attempt to remove secretions. Encouraging the process of huffing and coughing during treatment will improve or maintain

cough effectiveness (huffing is performed without glottis closure,

which cannot be achieved when intubated), owing to activation of the

expiratory muscles. If patients have difficulry with a deep inspiration

for an effective huff or cough, then the use of manual techniques, postural changes, or assistive devices, such as an adult manual breathing unit (AM BU bag), can be used to facilitate depth of inspiration.

Weaning from Ventilatory Support

During the weaning process, the physical therapist can play a vital role

on an interdisciplinary team responsible for coordinating the wean.

Physical therapists offer a combined understanding of the respiratory

difficulties faced by the patient, the biomechanics of ventilation, the

principles of exercise (weaning is a form of exercise), and the general

energy requirements of functional activities. Physical therapists can

work with the multidisciplinary team to optimize the conditions under