Caring for the patient receiving mechanical ventilation.
A. Monitoring and Assessing the Ventilator Patient
1. Vital signs and patient assessment.
a. Heart rate (pulse).
b. Respiratory rate.
c. Blood pressure.
d. Temperature.
e. ECG monitor (heart rate and rhythm).
f. Sensorium (level of consciousness).
g. Breath sounds.
h. Response to the ventilator.
i. CBC, intake and output.
j. ABG, pulse oximetry, capnography.
k. Hemodynamic measurements (BTFDC).
2. Measurements taken with the patient spontaneously breathing.
a. Tidal volume (V1).
b. Respiratory rate (f).
c. Minute ventilation (V s).
d. Vital capacity (VC).
e. Maximum inspiratory pressure (MlP).
f. Maximum expiratory pressure (MEP).
3. Measurements taken during ventilatory support.
a. Exhaled tidal volume
b. Respiratory rate (f).
c. Minute ventilation
d. Inspiratory flow (l:E ratio).
e. Alveolar minute ventilation.
1) Use the estimate of 1 mL per lb of ideal bodv weiqht for Vd.
2) Alveolar ventilation is best increased by increasing tidal volume.
f. Deadspace ventilation (Vd).
1) Mechanical deadspace - amount of common circuit tubing between the patient and wye adapter in the ventilator circuit.
a) Approximately 10 mL per inch of flex tubing. (5' = 50 mL Vp).
b) Can be used to adjust PaCO2 levels.
2) Anatomic deadspace - amount of the inspired tidal volume that does not enter the alveoli.
a) Approximately 1 mL per lb. of ideal body weight (150 lb. = 150 mL Vd). Used to approximate alveolar ventilation.
3) Alveolar deadspace - amount of alveolar ventilation that has no blood perfusion. Occurs with a pulmonary embolism.
4) Physiologic deadspace is the sum of anatomic and alveolar deadspace. Estimated by the Vd/Vt ratio.
g. Airway pressures.
1) Dynamic Compliance
2) Static Compliance
a) Plateau pressure is measured at the end of inspiration while the patient is forced to hold the volume momentarily (using inflation hold,
pause, or plateau).
b) Normal static lung compliance is 60 - 100 ml/cm H2O. 3) Increasing Airway Pressures.
a) Indicates the lung is becoming more difficult to ventilate.
b) Two reasons for airway pressure to increase on mechanical ventilation.
i. lncreasing aintray resistance (Raw).
a. Peak inspiratory pressure (PIP) INCREASES.
b. Plateau pressure (Ppl) REMAINS SAME
c. Raw can be estimated: (PlP - PPI).
d. Common causes.
1) Secretions in airway.
2) Bronchospasm.
e. Treatment.
1) Suction.
2) Bronchodilator.
ii. Decreasing lung compliance (CL).
a. Peak inspiratory pressure (PIP) INCREASES.
b. Plateau pressure (Ppl) INCREASES.
c. Common causesi
1) Atelectasis.
2) Pulmonary edema.
3) ARDS.
4) Pneumonia.
d. Treatment: increase PEEP, treat underlying cause.
B. Adjusting Ventilator Settings - Primary Controls
1. Modes of ventilation.
a. Although most ventilating modes will provide adequate ventilation, some modes offer advantages in certain circumstances.
b. Assist mode.
1) Patient initiates all breaths. No minimum respiratory rate.
2) Used during IPPB therapy.
3) Not recommended for continuous ventilation.
c. Controlmode.
1) Ventilator will initiate breaths at a preset rate.
2) Does not allow patient to initiate breaths.
3) Non-Apneic, non-sedated patients will often fight the ventilator (patient-ventilator dysynchrony), requiring sedation and/or muscular
paralysis.
4) Indicated for head trauma/surgery patients (for induced hypocarbia), status asthmaticus, flail chest, etc.
d. Assist Control mode.
1) Allows patient to set the respiratory rate.
2) The ventilator will maintain a minimum rate.
3) May be used with most patients in most cases.
4) Ventilator controls tidal volume for every breath.
e. SIMV mode.
1) Allows patient to breathe spontaneously.
2) Ventilator provides a minimum minute ventilation.
3) Used for patients with COPD to normalize ABG.
4) Used with tachypnea (>20 breaths per min)to avoid hyperventilation (pulmonary emboli).
5) Used for weaning patients from the ventilator.
6) Used instead of assisVcontrol to reduce barotrauma.
7) Used with PEEP to reduce barotrauma.
8) Combative patients (not due to hypoxia) can be first changed from assis/control to SIMV, then sedated and controlled.
f. Pressure Control Ventilation (PCV).
1) Pressure controlled breaths.
2) Used when peak inspiratory pressure (PlP) is very high (> 50 cmH2O).
3) Often combined with inverse ratio ventilation (lRV).
4) May improve oxygenation and reduce barotrauma.
5) Recommended for:
a) Patients requiring high F1O2 (>60%) and PEEP (> 15 cm H2O).
b) High PIP (> 50 cmH2O).
c) Low PaO2 and decreased compliance (ARDS).
6) Exhaled tidal volume will vary. Adjust lT or PIP as necessary.
C. High Frequency Ventilation
D. Independent Lung Ventilation (lLV)
E. Gorrecting an Arterial Blood Gas (PaCO2 and PaO2)
F. Adjusting Ventilator Settings - Secondary Controls