Patient Safety Tip of the Week

October 3, 2017

Respiratory Compromise: One Size Does Not Fit All



One of the prime strategies in patient safety is simplification. We always try to come up with solutions for prevention or intervention that are simple and can be applied across multiple settings and patient populations. But sometimes such “one size fits all” approaches are not appropriate.


One recently challenged example is the approach to monitoring for respiratory compromise in hospitalized patients. Because so many of our prior columns have focused on monitoring those at risk for opioid-induced respiratory depression (such as those patients likely to have obstructive sleep apnea), we have often focused on use of capnography for monitoring. But the National Association for the Medical Direction of Respiratory Care (NAMDRC) recently organized a workshop with representation from many national societies to address the unmet needs of respiratory compromise from a clinical practice perspective. At that workshop distinct subsets of respiratory compromise, characterized by the pathophysiological mechanisms they had in common, were identified that present similar opportunities for early detection and useful intervention to prevent respiratory failure (Morris 2017). The subtypes were:


The basic premise is that classification of acutely ill respiratory patients into one or more of these categories may help in selecting the screening and monitoring strategies that are most appropriate for the patient's particular pathophysiology.



Respiratory Compromise Due to Impaired Control of Breathing


This subgroup includes patients with dysfunction due to central nervous system injury, pharmacologic/toxic depressants, metabolic disorders, and sleep-associated breathing disorders. It also includes patients with neuromuscular weakness and sleep-disordered breathing.


Because inappropriate somnolence and markedly decreased breathing effort may represent early signs of respiratory compromise in this subgroup, patients at risk for respiratory compromise due to impaired control of breathing should undergo careful physical examination at regular intervals.


The authors note that monitoring of blood oxygenation is fairly routine but caution that changes in oxygenation are often the fairly abrupt end sequelae of compromised control of breathing. Therefore other monitoring options are appropriate for this subset of respiratory compromise, including continuous measurement of blood pressure, electrocardiogram, transcutaneous PCO2 estimation, and end-tidal capnometry.


They also note promising tools such as airflow measurement by a thermistor, to monitor the depth and frequency of breathing, and actigraphy to provide an indication of a patient’s general activity as a surrogate for the level of consciousness. They also note that periodic arterial blood gas measurements may provide unequivocal evidence of hypercarbia and hypoxemia. They also note the utility of clinical scales to measure consciousness, sedation, delirium, pain, and risk for sleep apnea. We’ve often discussed the RASS (Richmond Agitation-Sedation Scale) or the POSS (Pasero Opioid-Induced Sedation Scale) as useful tools. We’ve also stressed that in patients with sleep-disordered breathing, simply assessing their level of arousal, oxygen saturation or end-tidal CO2 when awake is inadequate. It’s important to observe their respiratory patterns when sleeping.



Respiratory Compromise Due to Impaired Airway Protection


Inability to properly swallow and effectively cough may lead to respiratory compromise due to impaired control of the upper airway. Such impairments are commonly seen in patients with stroke or neuromuscular disorders such as myasthenia gravis, Guillain-Barre syndrome, ALS, and various myopathies but may also occur in multiple sclerosis, Parkinson’s disease, and other CNS disorders. These predispose to aspiration and aspiration pneumonitis. The authors stress the many physical signs of aspiration or aspiration pneumonitis in the article.


Most of you are aware of the need to assess swallowing before attempting to feed stroke patients orally. But many forget to do similar assessment in patients with other neurological conditions. Repeated evaluations of the level of consciousness and the ability to chew, seal the lips, and swallow are recommended. Importantly, the authors note that transient episodes of respiratory status deterioration, even if they are brief and self-limited, may be warning signs of subsequent respiratory failure. They also note the importance of input from observation by family members, who may notice more subtle changes in level of arousal or respiratory drive.



Respiratory Compromise Due to Parenchymal Lung Disease


The authors discuss the many ways that parenchymal lung disease may impact physiological functions and result in respiratory compromise. This subgroup includes not only patients with pre-existing lung diseases but also patients who develop pneumonia or have a systemic inflammatory response. They note that tools like the lung injury prediction score may help identify patients at risk for development of ARDS. Common signs to watch for are hypoxemia and tachypnea and, again, changes in mental status may be clues.


Patients in this subgroup should be monitored continuously for changes in breathing frequency and for decreases in pulse oximetry or oxygen saturation. The authors caution that administration of supplemental oxygen may mask the hypoxemic effects of parenchymal lung disease. Therefore, this type of respiratory compromise is best monitored longitudinally by considering the increases in oxygen supplementation required to maintain adequate oxygenation.



Respiratory Compromise Due to Increased Airway Resistance


This subgroup includes not only patients with asthma and COPD but also those with increased airway resistance due to edema, laryngospasm, stenosis, or collapse of floppy tracheal segments.


A patient’s past history may be helpful. Severity of a patient’s prior exacerbations may be an important clue to identify respiratory compromise in patients with an acute asthma episode and previous ICU admissions and mechanical ventilation episodes are important predictors of respiratory failure in patients hospitalized with asthma. The situation in COPD is more complicated, since it depends upon the severity of the COPD and factors such as whether the patient has had hypercapnic episodes in the past.


Proper monitoring of ventilatory effort will allow earlier recognition of respiratory compromise due to increased airway resistance before the patient manifests deteriorations in gas exchange. Monitoring in this subgroup includes frequent heart rate, breathing frequency, and blood pressure measurement. While continuous oximetry and capnography may be useful, the authors emphasize the pitfalls of each. For example, pulse oximetry will not detect carbon dioxide retention, and can lead to a false sense of security, particularly when supplemental oxygen is being delivered. And capnography measurement may not be straightforward in patients with obstruction to air flow.


The authors note that clinical scales to quantify dyspnea can be followed over time to help detect respiratory compromise when progression of severity is gradual but that subjective scales may be of little value when impairment of cognitive function has occurred.



Respiratory Compromise Due to Hydrostatic Pulmonary Edema


Pulmonary edema is diagnosed on the basis of clinical, radiographic, and laboratory findings. Respiratory compromise from hydrostatic pulmonary edema is identified when oxygen saturation decreases, when FIO2 requirements increase, or when the breathing frequency and overall appearance suggest increased effort of breathing.


Monitoring longitudinally is important to identify the trajectory of the condition. Measurement of breathing frequency, oxygen saturation, FIO2 requirements longitudinally are used to detect escalating severity. Surveillance of ventilatory patterns, the effort required to sustain breathing, and estimation of extravascular lung water currently require frequent subjective evaluations.



Respiratory Compromise Due to Right-Ventricular Failure


Right ventricular failure may occur in pulmonary embolism, pulmonary arterial hypertension, and other causes. Pulmonary edema is characteristically absent in respiratory compromise due to right-ventricular dysfunction, However, the authors stress that, because the right ventricle is much less equipped than the left ventricle to increase its work load, this type of respiratory compromise entails the risk of rapid deterioration and catastrophic cardiac decompensation.


While continuous monitoring of breathing frequency and oxygen saturation may be helpful, the authors stress that hypoxemia from pulmonary vascular diseases may respond well to supplemental oxygen therapy, even as hemodynamics deteriorate. The principal danger is progressive right-ventricular failure so echocardiography and serologic tests of cardiac strain and damage should be checked periodically. Continuous electrocardiogram monitoring may detect new T-wave inversions in the

precordial leads, an ominous sign of right-ventricular worsening.



Overall, we found this article very enlightening. It really makes you understand you can’t just hook up patients to pulse oximetry and capnography and expect to identify all patients with deteriorating respiratory conditions. It really makes you understand that “one size does not fit all”.



Other Patient Safety Tips of the Week pertaining to respiratory issues:








Morris TA, Gay PC, MacIntyre NR, et al. Respiratory Compromise as a New Paradigm for the Care of Vulnerable Hospitalized Patients. Respiratory Care 2017; 62(4): 497-512






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