Respiratory Conditions (Sources: Revision notes) Flashcards
What is asthma?
Chronic disease of the airways associated with airway hyper-reactivity and inflammation
What are the risk factors for fatal asthma?
Previous life-threatening asthma Hospital admission within the past year 3 or more asthma medications Heavy beta agonist use Brittle asthma Evidence of adverse psycho-social circumstances (alcohol abuse, non-compliance with treatment, social isolation)
What are the types of brittle asthma?
Type 1 - wide PEFR variability
Type 2 - sudden severe attackes depsite appearing well controlled
What are the clinical features of a moderate exacerbation of asthma?
PEFR 50-75% predicted
What are the clinical features of a severe exacerbation of asthma?
PEFR 33-55% Resp rate > 25 Heart rate > 110 Low or normal PaCO2 Unable to complete a sentence
What are the clinical features of life-threatening asthma?
PEFR < 33% Silent chest Arrythmias Hypotension Bradycardia Hypoxia (sats < 92%, PaO2 < 8kPa) Hypercapnia Altered neurological status
In what circumstances are ABG and CXR indicated in asthma?
If there are any features of life-threatening asthma
How is an exacerbation of asthma managed?
Beta 2 agonist - first line treatment, neb or inhaled. IV should be reserved for those in whom inhaled cannot be delivered effectively
Anti-cholinergic agents
Steroids - reduce mortality, give early. 40mg pred and 100mg hydrocort are equally efficacious
Mag sulphate - a single dose 2g is recommended in severe or life-threatening asthma
Theophylline - doesn’t add any benfit and associated with increased side-effects
Heloix - no evidence for it’s benefit
What is dynamic hyperinflation and what effect does it have on ventilation?
In severe airflow limitation, the expiratory time may be insufficient to allow complete expiration
The residual volume may increase with each breath resulting in gas-trapping
This shifts the lungs up the compliance curve, decreasing compliance and thereby places the resp system at a mechanical disadvantage
Compensatory tachypnoea increases the work of breathing and decreases time available for expiration
Results in a vicious cycle of deteriorating resp function
How can you recognize dynamic hyperinflation on a ventilated patient?
- Failure of expiratory flow to return to baseline before the ventilator triggers
- May be quantified by measuring intrinsic PEEP
- In the absence of any spontaneous resp effort an expiratory hold is perfomredon the venitlator and end expiratory alveolar pressure allowed to equilibrate with upper airway pressure. The measured pressure minus the PEEP equals intrinsic pressure
In the presence of patient respiratory effort intrinsic PEEP can only be measured by an oesophageal balloon
Discuss NIV in asthmatics
Traditionally has a limited role
In theory IPAP will reduce work of breathing, whilst EPAP splints open small airways
Should only occur in a critical care area capable of escalating ventilation
Discuss induction of anaesthesia in asthmatics
The bronchodilatory effects of ketamine may be beneficial
Hypotension on induction may be significant as high intrathoracic pressures impede preload
Discuss the maintenance of sedation in asthmatics
Ketamine infusion may be useful providing sedation and bronchodilation
Inhalational anaesthetic agents have bronchodilatory properties
Delivery of anaesthetic inhalants on ICU is problematic in terms of scavenging
How should you ventilate someone having an acute exacerbation of asthma?
Prolonged I:E ratio
Slow resp rate
What bugs are typically responsible for an exacerbation of COPD?
Up to 80% of exacerbations of COPD are caused by viruses of bacteria
Haemophilus influenzae
Moraxella catarrhalis
Strep pnuemonia
Virus - rhinovirus, influenza, parainfluenza
