Respiratory emergencies in the ICU (Proceedings)

Respiratory emergencies should always be triaged quickly and with precision. Avoiding stress in the dyspneic patient is crucial. Oxygen cages can be useful in implementing a phase therapy approach; oxygen masks or nasal oxygen can be more effective in supplying oxygen but patient restraint alone can cause an arrest if traumatic. Minimal restraint and avoiding head and neck manipulation is therefore critical in respiratory diseases. Venipuncture, rectal temperature, and IV catheterization should not be attempted without first allowing the patient to acclimate to its surroundings and breathe more easily, if time allows.

Identifying common respiratory patterns

Developing an acute dyspnea strategy should be foremost in any emergency facility. Aquariums should be ready for the dyspneic pediatric patient, rather than large oxygen set ups, in order to provide an oxygenated environment in a shorter amount of time. Sedation, emergency tracheostomy kits, endotracheal tubes, and forceps should also be readily available if the patient is in respiratory distress or respiratory arrest due to tracheal trauma, foreign body, pulmonary constriction, severe pulmonary contusions or cardiac insufficiency. Patients in oxygen facilities should be monitored for increased body temperature, as the internal environment may become humid.

Auscultation is the single most important nursing triage tool in assessing the dyspneic patient. Proper technique for accuracy and expediency is paramount. The patient should be in sternal recumbency and allowed to inhale oxygen during the exam to facilitate lung expansion and to auscultate lung fields accurately. It is recommended to use the pediatric head of the stethoscope in smaller patients to avoid guttural sounds. The auscultation should include both sides of the chest, ventrally and dorsally, while paying close attention to the respiratory pattern. Respiratory effort should be noted in conjunction with the respiratory component. Clinical signs of respiratory insufficiency include tachypnea, cyanosis, open-mouth breathing, head and neck extension, and abnormal chest movement.

In general, respiratory patterns and lung sounds are subtler in cats than in dogs. In addition, cats have a unique ability to mask abnormal respiratory processes. In general, respiratory patterns should be assessed before restraint or manipulation when at all possible. Note that certain patterns can provide diagnostic information. For example, abdominal components can indicate pleural complications (fluid or air), neurological compromise or trauma (cervical lesions), or chest wall trauma. Paradoxical movements may indicate diaphragmatic hernia or neurological conditions. Chest expansion should be assessed in any respiratory movement, paying close attention to both inhalation and exhalation sounds during auscultation. It is important to note on which side or sides abnormal sounds are heard, and whether they are ventral or dorsal, cranial or caudal. Note that pain alone can cause an abnormal respiratory pattern and respiratory rate.

In the critically ill, it is important to note that the respiratory rate is just a number. The respiratory effort, respiratory component, and the mucous membrane color are more important than a single number. Duration of the respiratory insufficiency is also important to note. Special focus on the patient's body temperature, blood pH, and blood glucose is of particular importance if the respiratory effort is prolonged, particularly to the pediatric patient. Pulse oximetry can also be a useful tool in assessing respiratory function, but should not take place of thorough exam. Pulse oximetry measures oxygen saturation, not content, and keep in mind that the SPO2 is not the PaO2. It is also more difficult to obtain a pulse oximetry reading in the feline patient as opposed to the canine. The recommended site is the tongue, although that is not feasible if the patient is conscious. The mucus membrane is difficult to place the pulse oximeter probe on the feline patient as it is thin and generally has smaller surface area than the dog. An alternate site for pulse oximetry reading in the cat is the ear (often unreliable if the patient is hypothermic) or rectally, which requires a special probe not supplied in most pulse oximeter units.

Identifying the type of respiratory sounds in the critical patient can be difficult. Common respiratory sounds include harsh or static sounding lungs (indicative of trauma, parenchymal disease, early signs of fluid overload), crackles or popping sounds (indicative of parenchymal disease, severe fluid overload, asthma), wheezes or musical sounds (asthma or chronic bronchitis), or upper airway (referred) sounds (indicative of stenosis, elongated soft palate, tracheal collapse, or constriction), muffled or absent lung sounds (pneumothorax, hemothorax, chylothorax, or diaphragmatic hernia) or upper airway obstruction (characterized by severe inspiratory stridor and "noisy" breathing).

Respiratory emergencies can often be further categorized into the type of breathing pattern. There are typically four different breathing patterns commonly seen on emergency. Upper airway obstructions characteristically presents as a paradoxical movement of the abdomen during inspiration. The patient is often cyanotic and stressed. Examples of upper airway obstructions include laryngeal paralysis, tracheal collapse, foreign bodies, or severe upper airway edema. Emergency sedation and intubation is often necessary.

The second type of breathing pattern is classified as pleural space disease, wherein the patient has rapid, shallow breathing and muffled heart sounds. Paradoxical breathing can also be present. Typical cases include the pneumothorax, hemothorax, chylothorax, congestive heart failure or feline cardiomyopathy. Thoracocentesis should be performed immediately to retrieve restrictive fluid or air.

Small airway disease is another common breathing pattern noted in respiratory emergencies, characterized by prolonged expiration with prominent expiratory "push" sounds. In such cases, expiration becomes difficult as bronchoconstriction of the small airways causes air trapping. Inflammation, mucus accumulation, and muscle atrophy can further contribute to expiratory difficulty. Common causes of such breathing patterns are chronic obstructive pulmonary disease, bronchitis, and feline asthma.

Lastly, parenchymal diseases are characterized by both inspiratory and expiratory difficulty. Crackles and wheezes can be auscultated in severe cases. Chest expansion can often be exaggerated due to ventilatory difficulty. Typical cases include patients with pneumonia, pulmonary edema, cardiac disease, metastatic neoplasia, and pulmonary contusions. Diuretics such as furosemide are often administered to facilitate ventilation.

It is important to combine lung sounds with other physical exam findings such as patient mentation, respiratory rate, respiratory effort, respiratory pattern, heart rate, pulse quality, temperature, and mucous membrane color. Monitoring the trends of such exam findings is critical in providing good nursing care. Note that pediatric patients may fluctuate more easily than adults due to a more fragile bodily system.

Critical care techniques and patient monitoring

Triaging also involves proper technical procedures in addition to the physical exam in order to provide efficient care. Respiratory emergencies may require minimal restraint, oxygen therapy in the least stressful but efficient route, possible emergency intubation, thoracocentesis, tracheotomy, or chest tube placement. Implementing the phase strategy, thinking ahead, and preparing for the worst possible situation, will only benefit the critical patient.

A common procedure for the dyspneic patient involves the placement of a nasal oxygen catheter. Proper length and diameter tubing are necessary for effective oxygen delivery. The patient should be sternal and prepped by instilling opthaine drops down one nare and sliding the lubed tubing towards the medial canthus of the opposite eye. Length should be just beyond the medial canthus, and marked appropriately on the outside of the tubing prior to placement. Proper rates of oxygen delivery are at 50-100ml/kg/min. Elizabethan collars should always be utilized if an oxygen catheter is present. Suturing techniques are recommended over tissue glue to avoid skin irritation and sloughing. It is the author's opinion to place 8-10 French catheters in dogs, 5 French tubing catheters in adult cats and small dogs, and 3.5 French tubing catheters in kittens. "Red-Rubber" catheters are recommended for nasal oxygen catheters, and it is the author's opinion never to fenestrate the catheters.

For neonates, it is not recommended to place nasal oxygen catheters. Rather, utilize a small oxygen cage to provide an oxygenated environment. For patients with facial trauma, oral masses, partial obstructions, or stenotic nares, transtracheal catheters or nasotracheal catheters can be placed. Transtracheal oxygen can be placed with through the needle IV catheters and labeled appropriately for oxygen delivery only. Insufflation should be at a lower rate than that of nasal insufflation. Recommended rates are 50-75 ml/kg/min of 40 percent oxygen. Note that high oxygen rates can induce pulmonary damage and will worsen pulmonary function. Long-term use of transtracheal oxygen is not recommended. Nasotracheal catheters can also be placed if the patient is sedated. The catheter should be placed to the bifurcation and not directly into either main stem bronchi. This is a very useful technique for elongated soft palate patients or patients with laryngeal paralysis.

Other critical care techniques for respiratory emergencies include thoracocentesis. Auscultation before and after a chest tap is recommended to note changes and respiratory patterns, and more importantly, to know where the decreased sounds are the most apparent. Often with the critical patient, it is difficult to note decreased lung sounds. If the patient does not improve on oxygen or with medical therapy, the thoracocentesis should be performed to facilitate lung expansion and to help with a diagnosis.

The thoracocentesis should be performed while the patient is sternal to yield the maximum amount of fluid or air. The chest should be sterilely prepped and materials ready for a quick procedure. 20-25 gauge butterfly catheters are recommended for use in felines, in combination with a three-way stopcock and a small size syringe. The sixth to eighth intercostals space is the recommended entry site at either a ventral or dorsal approach, depending on auscultation. Typically, fluid will be collected more ventrally, as opposed to air, which is typically more dorsal. Proper handling of fluid material for analysis is recommended to avoid repeating a diagnostic thoracocentesis. For the small patient, it is recommended to use syringe sizes less than a 20 ml to avoid pain or trauma associated with large syringe evacuation. Frequent monitoring after thoracocentesis is important, as the procedure may actually cause a pneumothorax. If multiple chest taps are performed, placement of a chest tube may be necessary.

Arterial blood gas sampling is another technique utilized in respiratory emergencies. The femoral artery is best accessed when the patient is in lateral recumbency. The pulse is palpated digitally and ventral to the inguinal fold, with the heparinized syringe inserted directly perpendicular to the palpated pulse to obtain the sample. Note that only very small amount of heparin is required, lacing the needle only, for an arterial blood gas sample. The artery can be superficial; therefore, gentle insertion of the needle is recommended. Venous blood gases can also be useful if arterial sampling is difficult, and can give a general idea of global perfusion. In general, the venous P02 should be 40mmHg. Lactate measuring can also be an indication of both perfusion and ventilation, with values less than 2.4mMol considered normal.

The critical patient is more susceptible to respiratory compromise than other hospitalized patients, typically due to compromised immune systems, but often due to mere recumbency. Unfortunately, recumbency is often overlooked as a true medical problem. As recumbency in small animals requires primarily supportive care, a management protocol should be implemented at the onset of dehabilitation in order to prevent complications such as pneumonia or atelectasis.

Summary

Management of the respiratory patient should be accomplished in a step-wise, organized fashion to minimize stress and patient discomfort. Protocols should exist to effectively prevent and manage a patient that has, or is prone to, any respiratory insufficiency. Diagnostic and therapeutic measures should begin with frequent and thorough physical exams of the respiratory system, including respiratory patterns, mucus membrane color, lung auscultation, blood gas analysis and pulse oximetry. Identifying the patient with early signs of compromise will allow a more successful outcome.

References

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2. King, Lesley, Waddell, Lori. (2002) Acute Respiratory Distress Syndrome. ICU Handbook; 582-589.

3. Parent, C, King LG, Van Winkle TJ, Walker LM: Respiratory function and treatment in dogs with acute respiratory distress syndrome: 19 cases (1985-1993). J Am Vet Med Assoc 208:1428, 1996.