A. complications of intubation:

1. early:

a) hypoxemia due to prolonged attempts

b) right mainstem intubation

c) intubation of esophagus

d) upper airway trauma

e) aspiration

f) hypotension immediately following intubation

(1) this is usually multifactorial and etiologies include:

(a) effect of sedatives and/or paralytics used for intubation

(b) diminished blood return to the thorax due to positive pressure ventilation

(c) auto-PEEP with breath stacking (especially in patients with COPD)

(d) diminished LV output due to compression of the LV by the interventricular septum

(2) treatment:

(a) reduce tidal volume (often gives the most immediate improvement)

(b) fluid bolus (usually all that is required unless breath stacking occurs)

(c) reverse Trendelenburg position (until fluid bolus is given)

(d) reduce PEEP

(e) vasopressors with predominately alpha adrenergic properties (e.g., levarterenol)

 

2. late:

a) cuff leak

b) sinusitis

c) upper airway injury/stenosis

d) unplanned (self) extubation

B. ventilator-related complications:

1. disconnection

2. malfunction

C. suctioning-related complications:

1. hypoxemia

a) patients should always be pre-oxygenated with 100% oxygen prior to suctioning

b) suction time should be limited

2. arrhythmias

D. ventilation-related complications:

1. nosocomial infections (Kollef, 1999)

a) usually gram negative rods and staph

b) factors decreasing pneumonia probability:

1) early removal of NG tubes

2) hand washing

3) semirecumbant positioning of patient

4) adequate nutrition

5) avoid gastric overdistension

6) avoid nasal intubation (as opposed to oral intubation)

7) continuous subglottic suctioning

8) stress ulcer prophylaxis

(a) sucralfate is associated with less pneumonia than H2 blockers

c) early diagnosis of the specific organism(s) is critical for optimal survival

1) in a multicenter study of 413 patients with ventilator-associated pneumonia, compared to use of tracheal aspirates to guide antibiotic selection, early use of quantitative bronchoalveolar lavage or quantitative protected brush cultures to guide antibiotic selection was associated with (Ann Intern Med 2000; 132:621-30):

(a) decreased mortality (16% vs. 26%)

(b) lowered Sepsis Organ Failure Assessment scores (4.9 vs. 5.8)

(c) more antibiotic free days in the first month (11 vs. 7)

 

 

2. hemodynamic effects:

a) decreased cardiac output due to impaired venous return to the right heart and increased pulmonary venous resistance due to positive pressure alveolar distension

b) autoPEEP

3. barotrauma:

a) rare if plateau pressure is < 35

(1) for this reason, we generally use a plateau pressure < 35 as a major goal of mechanical ventilation and check plateau pressures frequently

b) often heralded by interstitial air on the chest x-ray

c) pneumomediastinum & subcutaneous emphysema

(1) does not need to be treated

(2) indicates high risk for pneumothorax

d) pneumothorax

(1) always treat with a chest tube in patients receiving positive pressure ventilation because of the risk of tension pneumothorax

(2) bronchopleural fistula can be difficult to resolve until the patient is off mechanical ventilation - the best treatment for a bronchopleural fistula is treatment of the underlying lung disease

4. oxygen toxicity

a) can occur as early as 24 hours after high oxygen exposure

b) more frequent if the FiO₂ is > 0.5

c) clinically resembles adult respiratory distress syndrome

d) very important to avoid since this often results in an inescapable vicious cycle of high oxygen requirements ultimately resulting in fatal respiratory failure

5. respiratory alkalosis

6. increased intracranial pressure

7. atelectasis (especially the left lower lobe)

 

 

 

III. Weaning from the ventilator (Hess, 2001; Hall, 1987)

A. Factors to consider:

1. non-ventilator derived parameters

a) awake and off sedatives (as much as possible)

(1) be aware of depression as a psychological limitation to weaning

b) proper position (upright, ideally sitting)

c) adequate nutrition

d) optimal fluid status

e) no infection

f) hemodynamically stable

(1) preferably off vasopressors

(2) angina optimally controlled

(3) no active bleeding

g) no metabolic alkalosis

h) normal electrolyte status

(1) calcium

(2) phosphorus

(3) potassium

(4) magnesium

i) afebrile

j) bronchospasm controlled

k) mechanical airway obstruction treated

(1) for lung tumors, placement of a bronchial stent can permit extubation

l) normal thyroid function

m) re-establishment of normal sleep-wake cycling

2. weaning parameters (Yang, 1991)

a) f/Vt < 100 breaths/min./liter

(1) calculation:

(a) disconnect the patient from the ventilator for 1 minute

(b) measure the spontaneous minute ventilation and the respiratory rate

(c) calculate the average tidal volume (in liters) as the minute ventilation ÷ the respiratory rate

(d) f/Vt = respiratory rate ÷ average tidal volume

(2) in one study (Yang, 1991), this was the single best predictor of success in weaning patients from mechanical ventilation

(a) sensitivity 97%, specificity 64%

b) maximal inspiratory pressure (also mistakenly referred to as "NIF") more negative than -20

(1) sensitivity 100%, specificity 14%

c) minute ventilation (VE) < 10 liters/min.

(1) sensitivity 31%, specificity 61%

d) tidal volume (Vt) > 4 ml/kg

(1) sensitivity 94%, specificity 39%

e) vital capacity > 10 ml/kg

f) FiO₂ < 40% with pO₂ > 60 mm Hg

3. intrinsic PEEP

a) common in patients with obstructive lung disease (e.g., COPD)

b) untreated, it can lead to increased work of breathing

c) it can be overcome by adding ventilator-delivered PEEP at pressures less than 85% of the intrinsic PEEP