Endotracheal intubation is a procedure in preparation for the placement of a feeding tube

Noninvasive Ventilation

Invasive mechanical ventilation requires endotracheal intubation to complete the patient circuit. Endotracheal intubation is the insertion of an artificial airway into the trachea by either the oropharyngeal or nasopharyngeal route. Although invasive ventilation is highly effective and reliable in supporting alveolar ventilation, the intubation procedure is associated with occasional adverse events such as pharyngeal/laryngeal/tracheal tissue damage, self-extubation, and aspiration of gastric contents.

Whenever possible, noninvasive ventilation is a preferable option. The upper airway is intact, airway defense mechanisms are preserved, and patients may eat, drink, verbalize, and expectorate secretions. Because of the convenience in using a face mask, NIPPV is the predominant means of administering noninvasive ventilation (Hill, 2006).

For patients with chronic obstructive pulmonary disease (COPD), NIPPV has been demonstrated to reduce complications, duration of ICU stay, and mortality (Plant et al., 2000). Chronic obstructive pulmonary disease is characterized by airflow limitation that is not fully reversible. We discuss an NIPPV clinical trial for COPD patients in the exercises at the end of the chapter. Noninvasive positive pressure ventilation has not been demonstrated to be more efficacious than invasive ventilation for other types of patients. However, numerous other applications are currently under clinical investigation (Hill, 2006).

Noninvasive ventilation

Invasive mechanical ventilation requires endotracheal intubation to complete the patient circuit. Endotracheal intubation is the insertion of an artificial airway into the trachea by either the oropharyngeal or nasopharyngeal route. Although invasive ventilation is highly effective and reliable in supporting alveolar ventilation, the intubation procedure is associated with occasional adverse events such as pharyngeal/laryngeal/tracheal tissue damage, self-extubation, and aspiration of gastric contents.

Whenever possible, noninvasive ventilation is a preferable option. The upper airway is intact, airway defense mechanisms are preserved, and patients may eat, drink, verbalize, and expectorate secretions. Because of the convenience in using a face mask, NIPPV is the predominant means of administering noninvasive ventilation (Hill, 2006).

For patients with chronic obstructive pulmonary disease (COPD), NIPPV has been demonstrated to reduce complications, duration of ICU stay, and mortality (Plant, Owen, & Elliott, 2000). Chronic obstructive pulmonary disease is characterized by airflow limitation that is not fully reversible. We discuss an NIPPV clinical trial for COPD patients in the exercises at the end of the chapter. Noninvasive positive pressure ventilation has not been demonstrated to be more efficacious than invasive ventilation for other types of patients. In the recent Breathe Randomized Clinical Trial, patients from 41 general ICUs in the United Kingdom were randomly assigned to receive weaning via early extubation to noninvasive ventilation (n = 182) or standard weaning (continued invasive ventilation until successful spontaneous breathing) (n = 182). The median time to liberation from any ventilation did not significantly change (4.3 vs. 4.5 days, respectively, P > 0.05) (Perkins et al., 2018).

4.5.1 Culture-based methods

Intra-vascular and urinary catheterization and endotracheal intubation may cause device-associated infection. Confirmation of catheter-associated infection requires isolation of the same organism from the patient's body fluids (blood, urine, tracheal and broncho alveolar aspiration) and from the catheter tips submitted for culture. The three common device-associated infections by biofilm-producing organisms are catheter-associated urinary tract infection (CAUTI), catheter related bloodstream infection (CRBSI) and ventilator associated pneumonia (VAP) (Maki et al., 1977; Mermel et al., 2001; Sheretz et al., 1990; Siegman-Igra et al., 1997; Singh et al., 2010). Central catheter infection may show infection at the site of surgical insertion, or perhaps as bacteremia. Various methods can be employed to diagnose CRBSI, such as semi-quantitative (direct inoculation by pressing device tip on to plate, or culture of catheter fluid), quantitative culture (sonication) and qualitative culture. In the case of CRBSI, two blood samples are collected, one through the catheter itself, and other from a peripheral site. This should be done at the time when the catheter is sent for culture. Following appropriate aseptic and antiseptic procedures, the catheter is removed from the patient with the use of sterile forceps. Two to three inches of catheter tip is cut with sterile scissors and put in a sterile capped container, which should be sent to the laboratory as soon as possible. For confirmation of CAUTI, urine is collected from the sampling port of the urinary catheter using a sterile syringe and needle (Singh et al., 2010). Clinically, a patient is considered to be suffering from VAP if they are on a mechanical ventilator and have developed a fever and cough with purulent expectoration. For VAP, the sample collected is broncho-alveolar lavage (BAL) through endotracheal intubation. (Maki et al., 1977; Mermel et al., 2001; Sheretz et al., 1990; Siegman-Igra et al., 1997; Singh et al., 2010). A majority of microbiology laboratories perform the semi-quantitative method because it is easy to perform, and is usually associated with decreased costs to the laboratories in terms of equipment and personnel training. The requirement for the infection to be diagnosed clinically as a case of CAUTI, is if the patient is catheterized and has developed one or more of the following conditions, such as, fever, supra-pubic pain frequency and urgency of micturition. Urine and/or device samples are cultured on blood and MacConkey's agar and incubated for 24 hours. More than or equal to 105 CFU/ml is considered as significant (Singh et al., 2010). For catheter-associated VAP, the samples (BAL and tracheal aspirate) are inoculated on blood and MacConkey's agar and incubated for 24 to 48 hours. For BAL, 103 CFU/ml and for tracheal aspirates 105 CFU/ml are considered as significant. All the isolates thus obtained are identified by standard microbiological culture techniques and tested for biofilm production. Various culture-based techniques for detection of biofilm are in use, such as the Congo red agar method, tube method and tissue culture plate method (Bose et al., 2009; Mathur et al., 2006).

General Anesthesia

Prolonged or invasive procedures are best conducted under isoflurane anesthesia. Endotracheal intubation is warranted for general anesthesia in swine to protect the airway and allow for controlled ventilation when required. Required equipment for endotracheal intubation of swine includes a laryngoscope with a 20–25 cm straight blade and a selection of cuffed tubes of appropriate size (4.5–8 mm). Endotracheal intubation is possible with the pig in dorsal, ventral or lateral recumbency. Two anatomic characteristics can complicate the procedure. First, the soft palate is long and must be displaced dorsally for visualization of the larynx. Second, the laryngeal diverticulum distal to the larynx may “trap” the tip of the endotracheal tube unless the tube is gently twisted as it passes over the epiglottis. After intubation, maintenance anesthesia usually requires an isoflurane vaporizer setting of 1.5%–2.5% in oxygen. The actual concentration of isoflurane will vary according to the anesthetic induction regimen, type of procedure, and concurrent use of other narcotic and sedative agents. Administration of Telazol® and xylazine for anesthetic induction has a substantial isoflurane-sparing effect that may last for the first 30–60 minutes of anesthesia. Adequate surgical anesthesia is indicated by absence of the pedal withdrawal reflex, minimal jaw tone, and stable heart rate and blood pressure (Thurmon and Smith, 2007; Smith et al., 2008).

1.2.1 Drug-dosing control for anesthesia administration

Anesthesia is mainly used to facilitate invasive and painful clinical procedures such as endotracheal intubation, ventilation, suction, and hemodialysis. Too much or too little anesthetic can cause increased morbidity. Hence, the rate of infusion of anesthetic drugs is critical, requiring continuous monitoring and repeated adjustments (Haddad et al., 2010). Typically, open-loop drug infusion is facilitated by a medical practitioner or via target controlled infusion (TCI) pump (Absalom and Mason, 2017; Absalom et al., 2011; Masui et al., 2010). TCI pumps are programmed to derive the required drug dose for a patient by using a nominal model of the patient. However, recent investigations in the area of anesthetic and analgesic drug dosing have documented several positive outcomes of the closed-loop control approaches compared to open-loop ones (Absalom et al., 2011; Brogi et al., 2017; Kuizenga et al., 2016; Soltesz et al., 2013). Specific advantages of the closed-loop control approaches include improved patient safety, early recovery time, and reduced treatment cost. Moreover, closed-loop control relieves the clinicians from doing frequent mechanical adjustments which in turn allow them to indulge in more critical aspects of therapy to improve overall well being of the patient (Haddad et al., 2010).

Patients admitted to ICU often suffer from multiple illnesses or even organ system failure. Hence, it is necessary to evaluate the health of these patients using various physiological monitors and provide required assistance using life-supporting devices. Some of the life-supporting procedures such as mechanical ventilation involve invasive endotracheal tube insertion which leaves the patient in physical as well as mental distress. Moreover, due to anxiety and discomfort related to these procedures the patients are often restless and in an incoherent state of mind. Hence, in order to comfort the patients and to perform painful clinical procedures in a cooperative and safe manner, often these patients are kept in a state of moderate sedation for a long period of time. Apart from the complications in the normal physiological functioning of the body which arise due to an inherent illness, side effects of the drugs used for treatment can also have an adverse effect on the overall health of these patients. For instance, most of the sedatives and analgesics used these days are identified to impair cardiac and respiratory functions (Absalom et al., 2011; Jacobi et al., 2002; Minto et al., 2000; Robinson et al., 1997). Thus, the critically ill patients in the ICUs who are treated using multiple intravenous drugs for long periods also demand the regulation of multiple physiological variables such as MAP, heart rate, respiratory rate, level of unconsciousness and pain sensation, and other vital parameters within acceptable safe limits (Heusden et al., 2018; Jacobi et al., 2002).

Analyzing drug anesthetic effects requires pharmacokinetic (PK) models to account for the drug disposition and pharmacodynamic (PD) models to capture drug concentration effects. In order to formulate the mathematical equivalent of a human drug disposition system with a time-dependent drug dose as an input signal, several physiological and nonphysiological models have been proposed (Absalom et al., 2009; Haddad et al., 2010). Among these, deterministic PK models, represented by compartmental models, which involve single or multiple compartments to capture the drug distribution and metabolism have gained wide acceptance (Absalom et al., 2009; Masui et al., 2010). In the case of intravenous infusion of anesthetic drugs, the mechanism of drug disposition can be effectively represented using a three-compartmental model with an additional effect-site compartment to model the time-lag in the drug dynamics at the locus of the drug effect (Masui et al., 2010). It should be noted that underlying illness, drug interaction, and other clinical disturbances alter the drug requirements (Absalom et al., 2011; Jacobi et al., 2002; Minto et al., 2000; Robinson et al., 1997).

Advancements in the area of automation and control engineering have fostered human health care in many ways. There exist many control methods that have been successfully used to design controllers for applications that require tracking a certain desired response. However, the requirement for an accurate mathematical model that depicts human physiology and difficulty in measuring certain system parameters that are required for feedback are the two main hurdles that limit the utilization of such control methods in the area of drug dosing. Several clinical and in silico trials conducted to evaluate the efficacy of the fixed-gain and linear controllers for the closed-loop control of anesthesia administration have proved inadequate (Absalom et al., 2011; Bailey and Haddad, 2005; Haddad et al., 2013; Hahn et al., 2012; Soltesz et al., 2013). This set back is mainly due to the complexity and uncertainty involved in the intricate task of anesthesia administration.

Furutani et al. (2010) reported 79 clinical trials conducted to evaluate the performance of model predictive controllers (MPC) for the closed-loop control of anesthesia administration. This study marks improved performance of the closed-loop control approach over manual control in terms of the amount of drug used and tracking error in reference output (BIS). However, the performance of the MPC-based controller was not so good compared to the that reported by Morley et al. (2000), Absalom and Kenny (2003), Liu et al. (2006), and Struys et al. (2001). Even though optimal control methods can account for system state constraints and control constraints, as pointed out by Furutani et al. (2010) such methods demand more accurate mathematical model to improve the tracking ability and robustness of the closed-loop control system. Haddad et al. (2003) documented the improved performance of adaptive disturbance rejection controller in addressing the system uncertainties and system disturbances associated with anesthesia administration. However, adaptive controllers cannot embody optimality requirements of the system optimality. Thus, it is necessary to develop novel methods that are capable of addressing problems that arise due to the system disturbances and system uncertainties, while deriving at optimal control laws to enhance the applicability and safety of automated anesthesia administration.

Anesthesia

Sheep should be fasted preoperatively to decrease the likelihood of regurgitation on induction of anesthesia and ET intubation. The reticulum, the most proximal rumen, has no sphincter mechanism at its oral end and often needs intubation and suction decompression to prevent regurgitation and aspiration (Holmberg and Olsen, 1987; Carroll and Hartsfield, 1996). Orogastric intubation is especially important if preoperative fasting does not occur. Typically, a sedative is administered IM to allow easy and safe placement of IV catheters for controlled administration of medication. Several sedatives are useful in the pre- and postoperative periods to aid in animal handling, and for performing minor procedures as shown in Table II.3.7.3. Large named veins such as the internal or external jugular or femoral veins can be used to secure IV access for fluid administration and frequent blood draws. Specialized catheters such as pulmonary artery catheters or long-term tunneled venous catheters (Hickman) may also be placed in these easily accessible, large veins (Tobin and Hunt, 1996). Following placement of a secure IV catheter and the administration of short-acting relaxing agents, ET intubation can be safely accomplished using standard cuffed ET tubes 5–10 mm in internal diameter. Anticholinergics or parasympatholytics, especially atropine, have been used on induction of anesthesia to decrease salivary and respiratory tract secretions. Use of these agents, however, is controversial in ruminants such as sheep, goats, and cattle because they inhibit gastrointestinal smooth muscle activity, which can cause rumen stasis in sheep (Carroll and Hartsfield, 1996). Table II.3.7.3 lists the recommended dosing of anesthetic agents.

First Aid

There is no antidote for phosphine toxicidty. Brush all visible particles from clothes, skin, and hair. Remove and double-bag contaminated clothing and personal belongings. Thoroughly flush exposed skin and hair with water for 3 to 5 minutes, then wash with mild soap. Rinse thoroughly with water. Use caution to avoid hypothermia when decontaminating children or the elderly. Use blankets or similar warmers when appropriate. If phosphides have been ingested, do not induce vomiting. Phosphides will release phosphine in the stomach; therefore, watch for signs similar to those produced by phosphine inhalation. Administer a slurry of activated charcoal at 1 g/kg (adult). Note to physician or authorized medical personnel: Advanced treatment; In cases of respiratory compromise, secure airway and respiration via endotracheal intubation. If not possible, perform cricothyroidotomy if equipped and trained to do so. Treat patients who have bronchospasm with aerosolized bronchodilators. The use of bronchial sensitizing agents in situations of multiple chemical exposures may pose additional risks. Consider the health of the myocardium before choosing which type of bronchodilator should be administered. Cardiac sensitizing agents may be appropriate; however, the use of cardiac sensitizing agents after exposure to certain chemicals may pose enhanced risk of cardiac arrhythmias (especially in the elderly). Consider racemic epinephrine aerosol for children who develop stridor. Dose 0.25–0.75 mL of 2.25% racemic epinephrine solution in 2.5 cc water, repeat every 20 minutes as needed, cautioning for myocardial variability. Patients who are comatose, hypotensive, or having seizures or cardiac arrhythmias should be treated according to advanced life support protocols. If evidence of shock or hypotension is observed, begin fluid administration. For adults, bolus 1000 mL/hour intravenous saline or lactated Ringer’s solution if blood pressure is under 80 mmHg; if systolic pressure is over 90 mmHg, an infusion rate of 150 to 200 mL/hour is sufficient. For children with compromised perfusion, administer a 20 mL/kg bolus of normal saline over 10 to 20 minutes, then infuse at 2 to 3 mL/kg/hour.

End-tidal carbon dioxide

End-tidal CO2 monitoring, or capnography, is a noninvasive alternate for measuring the partial pressure of arterial CO2 (PaCO2). Capnography measures the partial pressure of exhaled carbon dioxide (Ortega et al., 2012). It is commonly used when the patient is intubated (Tobias, 2009). An illustration of end-tidal with endotracheal intubation is shown in Fig. 15A. Colorimetric scales, such as litmus paper, are commonly used to show an approximate range of EtCO2 values, shown in Fig. 15B. Spectroscopy provides a more accurate, quantitative measurement of EtCO2 than the colorimetric scale, shown in Fig. 15C (Masimo, 2013; Ortega et al., 2012; Rhein et al., 2018). EtCO2 monitoring is valuable during cardiopulmonary resuscitation, the confirmation of endotracheal tube position, and procedural sedation-analgesia.

The primary advantage of EtCO2 monitoring is that it immediately identifies apnea or airway obstruction. EtCO2 is an effective way to monitor intubated patients. Unfortunately, with non-intubated patients, the accuracy of EtCO2 is reduced significantly by confounding factors such as expired gas by mouth breathing and ambient air. Correlation between PaCO2 and EtCO2 can be affected because of alterations in ventilation-perfusion ratios and patient positioning (Tobias, 2009). EtCO2 accuracy can be reduced in neonates and small children due to smaller tidal volumes (Dix et al., 2017).

End-tidal capnography is not commonly used in the NICU due to poor perfusion-ventilation matching in neonates as well as problems like leakage around poorly fitting endotracheal tubes (Fawke and Wyllie, 2019; Kugelman et al., 2016). Kugelman et al. (2016) performed an experiment to assess if distal EtCO2 is effective in helping keep infants in a safe CO2 range while ventilated. A cohort of 55 neonates participated in the study. Ventilated infants whose EtCO2 was monitored showed they spent significantly less time in unsafe CO2 levels. Additionally, monitored infants showed lower occurrences of intraventricular hemorrhaging or periventricular leukomackiat rates. Even though EtCO2 is not as effective for neonates as adults, it still does help with managing CO2 levels in ventilated neonates.

28.1.2 Technical Skills

Technical skills are also frequently deficient because of lack of exposure. For example, few pediatric intubations are performed by each pediatric emergency provider, even in high-volume centers.1,2 This is one of the techniques that must be practiced repeatedly for mastery and maintenance of skills. It is particularly true in pediatrics with the variability of the airways related to the growth and development of the patient over time.32 Unique physiologic concerns of the pediatric patient and syndromic features may increase the challenges in airway management. In fact, the success rate of intubation is not good, and complications are frequent, with around 20% of patients undergoing endotracheal intubation suffering harm (ranging from mild hypoxemia to death) due to provider performance deficiencies.33 This leads us to believe that students and physicians should be able to practice more.5,34 Sudikoff et al.35 demonstrated that simulation-enhanced educational strategies are effective in teaching pediatric residents’ airway skills and teamwork fundamentals required to efficiently manage an acute airway situation.

Defibrillation is another rare clinical event that should be practiced in simulation for maintenance of skills.6 It is well known that delay in delivering the shock may be fatal. Healthcare providers must be perfectly comfortable and competent in the interpretation of the cardiac rhythm and delivery of electrical therapy to reduce the time to defibrillation and increase the chances of conversion of a shockable unstable rhythm. Bootcamp-style courses have been demonstrated to increase participant knowledge, skills, and confidence in many fields of medicine.36 Burns et al.37 demonstrated that students improved their performance on lumbar puncture during a pediatric bootcamp with a day of intensive practice of technical skills.

Because trauma is the leading cause of death in children, Hunt et al.38 identified deficiencies in the stabilization of children presenting to emergency departments, revealing that mistakes are ubiquitous. It was observed that simple tasks such as estimation of a child’s weight, preparation for the insertion of the intraosseous needle, ordering intravenous (IV) fluid boluses, application of warming measures, and ordering dextrose for hypoglycemia were not correctly completed. All these actions are easy to integrate into a resuscitation simulation and could potentially greatly improve the outcome of children.