Respiratory Management Following Spinal Cord Injury - 14

RESPIRATORY MANAGEMENT FOLLOWING SPINAL CORD INJURY

secondary to hypoxemia or hypotension. The authors suggested hourly clinical and respiratory volume and negative inspiratory pressure assessments, if indicated. They advocated early transfer to experienced spinal cord injury centers.

Intractable Atelectasis
The patient’s chest radiographs may indicate persistent atelectasis or pneumonia, intractable to noninvasive treatment. Serial chest radiographs may also indicate worsening atelectasis. If there is intractable or worsening atelectasis, particularly if the symptoms, vital signs, physical examination, vital capacity, peak expiratory flow rate, FEV1, and NIF are deteriorating, the patient is a candidate for assisted ventilation. 11. If the patient needs mechanical ventilation, use a protocol that includes increasing ventilator tidal volumes to resolve or prevent atelectasis.
(Scientific evidence–V; Grade of recommendation–C; Strength of panel opinion–Strong)

Indications for Mechanical Ventilation
Respiratory failure, atelectasis, and recurrent pneumonia are common problems in the tetraplegic patient (Bellamy et al., 1973; Carter, 1987; Kiwerski, 1992; Reines and Harris, 1987). In tetraplegic patients, the forces favoring airway closure are greater than the forces favoring opening of airways. The factors favoring airway closure are: Weakness of inspiratory musculature. Loss of surfactant. Water in the alveoli (which can occur because of aggressive fluid resuscitation in the initial phase of the injury, when the patient may have been hypotensive). Pressure of subdiaphragmatic organs on the lung. The major factor favoring opening of the airways is the negative force generated during inhalation. This force is greatly reduced in the tetraplegic patient due to paralysis. Mucus can also block the inflow of air, and the paralyzed patient has trouble keeping the airways free of mucus because of the weakness of the cough. When the airways close, lung compliance reduces because of the loss of surfactant production. Atelectatic lung produces no surfactant, but hyperinflation enhances surfactant production. If the compliance of the lung is reduced because of airway closure or plugging by mucus, it becomes more difficult for the patient to generate a breath. If it is more difficult to breathe, the patient fatigues and develops respiratory failure. If the airways can be kept open or can be reexpanded with treatment, it becomes easier for the patient to breathe. Therefore, it is very important to keep the lungs expanded, and efforts need to be maximized to effect deep breaths and clear the airways of mucus.

Respiratory Failure
Respiratory failure is an indication for ventilation. This is defined as pO2 less than 50, or pCO2 over 50, by arterial blood gas testing, while the patient is on room air.

The reason for ventilating patients is their inability to take a deep breath, resulting in hypoventilation, but ventilating them with small tidal volumes only perpetuates the underlying reason for initiating mechanical ventilation. Lung tissue in patients with acute spinal cord injury is usually healthy, except for atelectasis or pneumonia. Treatment on the ventilator should be designed to overcome the hypoventilation of lung tissue. ARDS (acute or adult respiratory distress syndrome) patients have a problem with diffuse lung injury. For patients with ARDS, it is very appropriate to ventilate the patient with small breaths to avoid barotrauma. If a tetraplegic patient develops ARDS, treatment should follow a protocol for ARDS. The incidence of barotrauma and ARDS in tetraplegia has not been studied. Peterson et al. (1999) studied patients treated during a 10-year time period who were either ventilated with relatively low tidal volumes or ventilated by means of a protocol that gradually increased their tidal volume over a period of approximately 2 weeks. All of the patients were ventilator dependent on arrival at a tertiary care facility. The average ventilator tidal volume on discharge from their previous hospital(s) was 900–1000cc for all of the patients. In the patients subsequently ventilated by means of the protocol, the incidence of atelectasis decreased from 84% on admission to 16% in 2 weeks, whereas those patients ventilated with small tidal volumes had an increase in incidence of atelectasis from 39% to 52% after 2 weeks. These data suggest that low ventilator tidal volumes are a cause of atelectasis and that cautious implementation of larger ventilator tidal volumes can successfully treat atelectasis.

Respiratory Management Following Spinal Cord Injury

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