Initial Ventilator Setup

Warren Isakow

The initiation of mechanical ventilation is a critical period during the course of a patient’s stay in the intensive care unit. The clinician is encouraged to monitor the patient closely during initiation of mechanical ventilation as this period often provides important answers regarding a patient’s underlying pathophysiologic abnormality. This simple bedside process allows for verification of the underlying cause of the decompensation requiring ventilatory support, assessment of severity of the disease process, the likely response to standard therapies, and it helps with planning of care during the next few days to weeks.

Table 8.1 provides a general guideline to the initial ventilator settings in different clinical circumstances. The table is simply a guide, and the reader should understand that every patient is unique and should have the ventilator adjusted according to the individual’s clinical status.

Algorithm 8.1 is a management algorithm for troubleshooting the situation of a patient with persistent high peak airway pressures, a common ventilator-related problem in the intensive care unit. Table 8.2 provides potential causes for an alarm resulting from a low exhaled tidal volume/low minute ventilation.

TABLE 8.1 Guidelines for Initial Ventilator Settings in Different Clinical Scenarios

Indication for mechanical ventilation	Mode of choice	Respiratory rate (breaths/min)	Tidal volume (mL/kg)	FiO₂	PEEP	Additional ventilator issues	Adjunctive therapies	Additional comments
Airway protection, spontaneously breathing patient (e.g., hepatic encephalopathy, upper airway obstruction)	AC (volume) SIMV PSV	10-14	8-10	100%, obtain ABG and wean for sats >92% to goal Fio₂ of 40%	5	Peak flow 60 L/min Trigger sensitivity -2 cm H₂O	DVT GI	Maintain on MV until upper airway issues resolved Patients with hepatic encephalopathy are prone to develop a respiratory alkalosis, so TV may need to be reduced
Asthma exacerbation	AC (volume)	Set rate low, 8-12	6-8	100%, obtain ABG and wean for sats >92% to goal Fio₂ of 40%	0-5	Set peak flows high, allow adequate expiratory time Consider square wave ventilation. Use flow-by for easier triggering	BD ST AB SDN DVT GI	Tolerate hypercarbia, higher peak airway pressures Monitor for auto-PEEP and barotrauma Do not ventilate for a “normal” ABG Apply external PEEP to overcome intrinsic PEEP when triggering Often need heavy sedation initially Once bronchospasm and acute issues adequately resolved do not do prolonged weaning trials, consider trial of extubation
COPD exacerbation	AC (volume)	Set rate low, 8-12	6-8	100%, obtain ABG and wean for sats >92% to goal FiO₂ of 40%	0-5	Set peak flows high, allow adequate E time Use flow by for easier triggering	BD ST AB DVT GI NUTR	Monitor for auto-PEEP Avoid posthypercapnic alkalosis Tolerate hypercarbia; do not ventilate for a “normal” ABG Monitor for barotrauma Apply external PEEP to overcome intrinsic PEEP when triggering Consider extubation to NIPPV
Hypoxemic respiratory failure with pneumonia or pulmonary edema	AC (volume)	Often need high rates, 16-24 because of high V_E requirements	6-8	100%, obtain ABG and wean for sats >92% to goal FiO₂ of 40%	5-10	Often have high V_E requirements	BD AB DVT GI NUTR	Secretion management is important In septic patients, allow full MVS to divert CO from the respiratory muscles to other vital organs Follow improvement clinically as improved pulmonary compliance
ALI/ARDS	AC (volume) PCV, high-frequency oscillator, APRV	Often need high rates, up to 30, because of high V_E requirements	6	100%, obtain ABG and wean for sats >92% to “safe” FiO₂ of <60%	5-15	May need I:E of 1:1 or 1.5:1 (IRV) Need higher mean airway pressures Allow permissive hypercarbia to pH of 7.20	BD DVT GI NUTR SDN	Consider nebulized prostacyclin, nitric oxide, or oscillator Monitor for barotrauma Often require heavy sedation Try to avoid neuromuscular blockade if possible Consider adjunctive steroids Monitor for septic complications
Postoperative respiratory failure	AC (volume)	Set rate at 10-16	8-10	100%, wean rapidly for sats >92% to goal FiO₂ of 30%	5	Verify placement of all lines, tubes placed in OR Peak flow 60 L/min	DVT GI	Await sedatives, paralytics to be cleared and perform weaning rapidly Prone to hypoventilation after extubation Prone to atelectasis and splinting due to pain that can cause hypoxemia
Hypoventilation from CNS depression, neuromuscular weakness	AC (volume)	Set rate at 10-16	8-10	100%, obtain ABG and wean rapidly for sats of <92% to goal FiO₂ of 30%	5	Peak flow 60 L/min	GI DVT NUTR	Avoid sedatives Prone to atelectasis Follow NIF in patients with weakness
PEEP, positive end-expiratory pressure; AC, assist control; SIMV, synchronized intermittent mandatory ventilation; PSV, pressure support ventilation; ABG, arterial blood gas; sats, hemoglobin oxygen saturation; DVT, deep venous thrombosis; GI, gastrointestinal; MV, mechanical ventilation; TV, tidal volume; BD, bronchodilator; ST, steroids; AB, antibiotics; SDN, sedation; COPD, chronic obstructive pulmonary disease; NIPPV, noninvasive positive pressure ventilation; V_E, minute ventilation; MVS, mechanical ventilator support; CO, cardiac output; PCV, pressure control ventilation; I:E, expiratory time ratio; IRV, inverse ratio ventilation; NUTR, nutritional support; OR, operating room; NIF, negative inspiratory force, APRV, airway pressure release ventilation.