In intubated or tracheostomized patients, endotracheal suctioning consists of aspirating secretions retained within the artificial airway, trachea, and main bronchi via a suction catheter. Suctioning is one of the most common daily procedures. It should be performed only by qualified personnel, namely, physicians, respiratory therapists, or nurses, with appropriate skills and training to recognize the need for suctioning, perform it appropriately, and promptly respond to any potential complication.
Indications and Technical Procedure
The primary indication for endotracheal suctioning is to maintain patency of the airways, but it is also commonly performed to obtain secretions for diagnostic purposes. Current guidelines recommend that suctioning should not be performed routinely79 to minimize the risk of unnecessary complications.
Several parameters have been suggested to detect the need for suctioning (Fig. 52-6). Researchers have focused especially on the typical sawtooth pattern of airflow in patients with secretions (Fig. 52-7). Jubran and Tobin80 first proposed that retained mucus could be detected via the flow-volume loop, and reported that a sawtooth pattern had a good sensitivity and specificity. Guglielmotti et al81 subsequently confirmed that the best predictors of the need of suctioning were (a) respiratory sounds heard via a stethoscope over the trachea, and (b) the sawtooth pattern on a real-time flow-volume loop (sensitivity 0.82, specificity 0.70).
Suggested operative protocol for endotracheal suctioning. ARDS, acute respiratory distress syndrome; ALI, acute lung injury; FIO2, inspiratory fraction of oxygen; ID, internal diameter; MV, mechanical ventilation; OD, outer diameter; PEEP, positive end-expiratory pressure; VT, tidal volume.
Flow waveform during volume-controlled mechanical ventilation. The typical expiratory sawtooth pattern used as an indicator for endotracheal suctioning can be recognized. Of note, the presence of water condensation within the circuit should be excluded before proceeding with suction.
Endotracheal Suctioning Procedure
Endotracheal suctioning begins with inserting a suction catheter into the artificial airway. Because there is no obvious advantage with deep suctioning versus shallow suctioning, the tip of the catheter should be placed in close proximity to the tip of the endotracheal tube before applying vacuum. As the catheter is pulled back, intermittent suction should be applied and the catheter continuously rotated. Shallow suctioning is particularly advisable in infants to minimize complications.82,83 The only goal of suctioning is aspiration of secretions; hence, application of negative pressure, when the catheter is not close to secretions, or when all the mucus has already been aspirated (i.e., prolonged suctioning), only increases the risk of complications with no improvement in efficacy. Suctioning should last no more than 15 seconds79 after inserting a catheter into an artificial airway.
Selection of Suction Methods and Catheters
Open versus Closed Suctioning
Endotracheal suctioning can be performed either by disconnecting the patient from the ventilator (open suctioning) or through use of a suction catheter that does not require ventilator disconnection (closed suctioning), which is located inside a plastic contamination shield and in-line with the ventilator circuit.84,85 Closed suctioning is beneficial in patients who require high levels of PEEP and inspired fractional concentrations of oxygen (FIO2). Several studies in adults with acute lung injury and acute respiratory distress syndrome (ARDS) have confirmed that, unlike open suctioning, closed suctioning prevents reduction of lung volume and desaturation.86–88 These studies suggest that closed suctioning is especially appropriate in patients with most severe lung failure (partial pressure of arterial oxygen [PaO2/FIO2 ≤200), who are intolerant of even brief disconnections from the ventilator. In studies by Cereda et al86 and Maggiore et al,88 open suctioning caused almost 1.5 L volume loss, half of which was secondary to the ventilator disconnection.88 Results of studies assessing open and closed suctioning in newborns with respiratory distress syndrome89–92 are consistent with data from adults.
Closed suctioning is also been introduced to reduce environmental contamination,93,94 exogenous colonization of the airways via suction catheters95 and potentially ventilator-associated pneumonia. Three meta-analyses–98 have compared closed and open suctioning and found no benefits in preventing ventilator-associated pneumonia. Siempos et al97 analyzed data from nine randomized trials, comprising of 1292 patients; data pooled from four showed a higher incidence of respiratory tract colonization using closed suctioning.
During closed suctioning it is important to note that triggered ventilator autocycling partially compensates for the loss of pressure, and investigators99,100 have shown that the distal dispersion of secretions by ventilator airflow may reduce the effectiveness of closed versus open suctioning.
The main features that should be considered when choosing the most appropriate suction catheter are (a) the ratio between catheter outer diameter of the catheter and the internal diameter of the artificial airway; and (b) the size, number, and location of the suction holes. The outer diameter of the suction catheter greatly influences the loss of lung volume during the procedure. A larger catheter increases endotracheal tube resistance and facilitates loss of lung volume, because aspirated gas is not rapidly replaced by gas flowing through the endotracheal tube. These theories were clearly elucidated in early reports by Rosen et al101,102 and confirmed in laboratory studies assessing pediatric103,104 and adult105 catheters. Evidence from those studies strongly suggests that the ratio of suction catheter outer diameter to artificial airway internal diameter should be 0.7 or less in adults and approximately 0.5 in children.
Several investigators have evaluated intrinsic characteristics of the suction catheter to identify factors associated with efficacy and safety.106–109 Sackner et al110 first demonstrated that invagination of the tracheal mucosa into the side holes frequently occurred with all the different catheter designs. In a more recent report, Shah et al109 assessed six suction catheters (Fig. 52-8) with different designs and found that all performed equally with low viscosity mucus simulant; when viscosity resembled airway secretions, larger and nonparallel side holes were more efficient. In certain instances, a curved tipped catheter111–113 may help when suctioning mucus within bronchi difficult to access with a straight catheter.
14 Fr suction catheters studied in vitro by Shah et al employing a mucus simulant with viscoelastic properties similar to human mucus. Nonparallel position and larger diameter of the suction holes were the major determinants of catheter’s efficacy. (Used, with permission, from Shah et al.109)
In ventilated patients, strict monitoring during endotracheal suctioning is strongly advised.79 It is especially important to monitor heart rate, oxygen saturation, arterial pressure, and, in particular cases, intracranial pressure, throughout the procedure.
Vacuum Adjustable Regulator
The level of vacuum should always be adjusted before suctioning, so as to improve efficacy and minimize complications. Few studies have evaluated the efficacy and safety of suctioning at increasing vacuum levels. The latest guidelines79 recommend a vacuum no higher than 150 mm Hg in adults and 80 to 100 mm Hg in neonates, although the lowest level of negative pressure that efficiently removes secretions should always be favored.
Additional Equipment for Sterile Suctioning
Theoretically, during open suctioning there is a risk for environmental contamination from the patient and exogenous colonization of the patient. First and foremost, hand hygiene before and after the procedure is mandatory. Endotracheal suctioning is an invasive procedure and the use of sterile gloves is advisable, although there are no clinical studies specifically investigating the association between the use of unsterile gloves and respiratory infections. Blackwood et al114 reported that gloves are important even during closed suctioning because of potential contamination of staff hands from the flush port.
A quasiclosed suctioning system, via a swivel adapter115 positioned at the proximal tip of the endotracheal tube, is an alternative approach to minimize the loss of lung volume and desaturation during suctioning.88,116 Investigators87,88 found that suctioning through either a swivel adapter or a closed suctioning system similarly limited the decrease in lung volume as compared with open suctioning. Importantly, as during closed suctioning,117 the ventilator should be allowed to autocycle to compensate for the loss of gas.
The use of 2 to 5 mL boluses of saline, instilled into the endotracheal tube before suctioning to induce cough and hydrate inspissated secretions remains controversial and lacks clear evidence. The first concern is that saline instillation, particularly in the semirecumbent position, may drip into the lungs and cause serious adverse effects, such as oxygen desaturation,118,119 tachycardia,119,120 dyspnea, and anxiety.121 Second, several studies122,123 have consistently demonstrated the presence of bacterial biofilm within the endotracheal tube, hence, instillation of saline may dislodge pathogens.124 Caruso et al125 published a report on 262 patients randomized to receive either isotonic saline instillation before suctioning or no treatment. The authors found a lower incidence of ventilator-associated pneumonia, and no significant differences in secondary outcomes. Because of limited evidence and the potential for adverse effects, routine saline instillation cannot be recommended; moreover, when mucus progressively becomes thicker, the humidifier’s performance should be checked.
Complications of Endotracheal Suctioning and Preventive Measures
After discharge from an intensive care unit, patients remember endotracheal suctioning as one of the most unpleasant and painful procedures;126–128 such memories may affect later quality of life.129
Once inside the trachea, the suction catheter frequently adheres to the tracheal mucosa, and may lead to the impairment of mucociliary transport130 and severe mucosal injury.110,131 Sackner et al110 first addressed this problem by devising a novel suction catheter with a modified tip to prevent contact against the tracheal mucosa. In a later report106 the new catheter was compared against standard catheters in dogs, and the investigators demonstrated that the risk of mucosal injury was specifically associated with deep suctioning rather than catheter design or vacuum level. Intermittent suctioning is recommended to prevent mucosal invagination into the suction holes.
Endotracheal suctioning is associated with several cardiovascular, pulmonary, and neurologic complications. Bradycardia and hypertension are the most frequent cardiovascular complications, mostly as a result of a vagal reflex and resulting in increases in parasympathetic and sympathetic activities.132–135
Hypoxemia during suctioning is extremely common, particularly in adults with severe lung disease86,88 or infants.92 As described above, closed or quasiclosed systems have been used to prevent those complications. Hyperoxygenation before the procedure is also used to prevent hypoxia,136,137 and several ventilators now provide a control for automatic preoxygenation and postoxygenation. A meta-analysis,138 based on pooled data from fifteen studies in adults, demonstrated a 49% reduction of suction-related hypoxia when pre-hyperoxygenation and post-hyperoxygenation was applied. There is no clear evidence as to the level of FIO2 that should be used to hyperoxigenate. In adults, FIO2 of 100% is widely used. Hyperoxia, however, may be deleterious,139 particularly in neonates; hence, in these instances, a 10% increase79,140 from baseline is recommended. A recruitment maneuver applied after suctioning in selected patients with ARDS or acute lung injury is associated with more rapid return of baseline lung volume and reversal of hypoxia.88,141,142 Finally, severe bronchoconstriction has been demonstrated during suctioning in animals143,144 and humans.145
In patients with intracranial hypertension, an abrupt burst of coughing provoked by tracheal stimulation could increase the intracranial pressure; if there is not a concomitant increase in cerebral blood flow, brain ischemia may ultimately result.146–148 Several drugs have been tested, mainly in adults, to blunt the responses to suctioning, including barbiturates,149 narcotics,150,151 anesthetic agents,152–155 and neuromuscular blocking agents.149,156,157 These drugs should be indicated on a case-by-case basis and the potential adverse hemodynamic effects of such agents151,158 should be balanced against the perceived benefits.
Lastly, suctioning may increases endogenous and exogenous colonization of the lower airways. Manipulation of the suction catheter before insertion,159 passage of the catheter within the colonized artificial airway,160 and mucosal injury caused by negative pressure110 are possible culprits involved in suctioning-related colonization of the airways. In ventilated newborns, transient bacteremia has been associated with endotracheal suctioning.161 Finally, a number of studies found that closed suctioning catheters were easily colonized and associated with higher incidence of airways colonization;161–165 nevertheless, the evidence is still controversial and, as described above, no increase in incidence of ventilator-associated pneumonia was found, even when the catheter was not changed daily.166