Ventilation and Tidal Volume in Hypoxic Patients

· Student Corner,Clinical Education

Words By Hannah Dumbleton

The ability to provide adequate ventilatory support to a patient is a vital skill required by paramedics. Without sufficient airway management skills, patient safety and advocation becomes compromised. During clinical placement preperation, a paramedicine student and crew were presented with an adult male who was found unconscious following a suicide attempt involving the ingestion of rat poison and a subsequent hanging. On arrival to the scene, the patient was found actively seizing, and managed appropriately with midazolam and high flow oxygen administration through a non-rebreather mask.  

Once seizure activity had ceased, the patient remained hypoxic indicating the presence of a potential hypoxic brain injury. Accordingto Lacerte et al., (2020), a hypoxic brain injury can occur when oxygen delivery to the brain is compromised, with cardiac arrest and strangulation often contributing to an increased likelihood of developing this condition. Cinar et al., (2012) concluded that epileptic seizures are often detected following an unsuccessful hanging attempt due to the hypoxic brain injuries suffered by these patients. Therefore, the lack of neurological oxygen supply during this patient’s suicide attempt makes the likely reversible cause of his seizure hypoxia.

Following the cessation of the seizure, the patient was apnoeic, hypoxic and hypercapneic, and therefore required Intermittent Positive Pressure Ventilation [IPPV]. Whilst the crew recognised the need for IPPV administration and identified a proficient strategy to correct the reversible cause of hypoxia, the implementation by the student was less than adequate. Nehme & Boyle (2010) conducted a study to determine the ability of paramedicine students to retain respiratory ventilation knowledge. The results concluded that 90% of surveyed paramedicine students had poor knowledge of current ventilation guidelines. This lack of clinical understanding may result in students being unable to recognise patients at risk of hypoxic cardiac arrest, therefore potentially undermining patient safety.  

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Furthermore, during a case reflection, the student recognised that it was likley that they did not check for the adequate rise and fall of the patient’s chest whilst ventilating. According to the Victorian Ambulance Service [VAS], a patient’s tidal volume should be assessed to ensure ventilation is adequate irrespective of oxygen saturations (SPO2). Without continuous tidal volume checks, paramedicine students are unable to ascertain if the patient’s hypoxia is being corrected. Additionally, the student failed to recognise changes in the patient’s oxygen saturations or end tidal carbon dioxide (ETCO2) levels on the monitor. Whilst the SPO2 probe may provide somewhat inadequate readings of a patient’s level of hypoxia, the patient’s ETCO2 levels provide precise information pertaining to a patient’s metabolic and respiratory function. Without regular monitor checks for updated SPO2 and ETCO2 levels, paramedicine students are unable to determine if their ventilation therapy is sufficient enough to reverse the patient’s hypoxia. The culmination of these issues resulted in the patient being at increased risk of suffering a hypoxic cardiac arrest. A study conducted by Farrell et al., (2017) concluded that up to 8% of seizure patients who experience hypoxia during the postictal phase will also experience sudden cardiac arrest and death. This results in diminished positive patient outcomes and limited patient advocation. 

In conclusion, adequate ventilatory support is vital for all patients following the cessation of a seizure, particularly those induced by hypoxia. Paramedicine students should regularly check for adequate rise and fall of the chest whilst ventilating, as well as conducting proficient SPO2 and ETCO2 checks to ensure patient hypoxia is being corrected (VAS, 2020). Without these assessments, paramedicine students are unable to ascertain if they are making a positive impact on haemodynamic stability, often subjecting patients to increased risks of hypoxic cardiac arrest.  


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