Mr Khan Chronic Obstructive Pulmonary Disease Salbutamol Antimuscarinics For Respiratory Diseases Oxygen Transport Taking An Arterial Blood Sample Positive Airway Pressure Ventilation Arterial Blood Gas Basics C O P D Quick Reference Guide Acute C O P D Exacerbations The Alveolar Gas Equation Inhaled C O P D Therapy Guide Respiratory Pharmacology

I saw my first COPD exacerbation in my second week as a FY1 doctor in the emergency department. I’d barely found my feet working in this environment.

I entered the cubicle to find Mr Khan, his wife and two young men who introduced themselves as his sons. Mr Khan was too breathless to speak (I estimated his respiratory rate to be about 40 shallow breaths/minute), so his wife explained that he was 64 and had been diagnosed with COPD two years ago but had never been to hospital before. He’d quit smoking soon after diagnosis. ^{Chronic Obstructive Pulmonary Disease}

He’d suffered from a very heavy chest cold in the previous fortnight and his GP had prescribed him amoxicillin in addition to his usual inhalers, which she showed me and I recognised as tiotropium and salbutamol. His breathing had become more difficult the previous evening and subsequently worsened and despite his protestations his wife and sons had convinced him to go to hospital. ^{Acute C O P D Exacerbations}

The blood test results ordered by the triage nurse showed that he had an elevated CRP and white cell count with a haemoglobin level of 18 g/100 ml. Meanwhile, I gave him 100 µg of hydrocortisone IV and put a venturi mask on him to deliver 28% O₂ (0.28 FiO₂) and started a nebuliser to deliver salbutamol and ipratropium back to back. ^{Salbutamol ◦ Antimuscarinics For Respiratory Diseases ◦ Inhaled C O P D Therapy Guide}

After a few minutes he looked a little more settled, but the pulse oximeter attached to his finger showed that his O₂ saturation was continuing to drop, and now low at 89%. I bleeped for senior help. ^{Oxygen Transport}

The registrar, Shariq, arrived within a few minutes and I briefed him as best I could. He sent for a portable X-ray machine and asked me to take an arterial blood sample for gas analysis. I explained to Mr Khan what I was going to do and why and then proceeded to take the second unassisted arterial blood sample of my career. Shariq smiled as I got my sample at the first attempt, and I ran off to the blood gas analyser. ^{Taking An Arterial Blood Sample}

Upon my return, the portable X-ray unit was being wheeled away and I showed Shariq the ABG results, which he asked me to interpret: ^{Arterial Blood Gas Basics}

“Everything is a bit border-line. There’s hypoxaemia, a little hypercapnia perhaps and the mild acidosis you might expect from that. Base excess is normal and lactate is a touch high”, I said confidently. I glanced at the pulse oximeter readout and tapped it to draw Shariq’s attention to it. Mr Khan’s oxygen saturation had fallen to 86%. ^{The Alveolar Gas Equation}

Shariq nodded as he examined the X-ray on the screen. “Look here”, he said”, “there’s a little hyperinflation but no sign of pneumothorax, pneumonia or anything else. His ABG doesn’t show any signs that he’s been retaining CO₂ chronically. This looks like a relatively simple COPD exacerbation. Prepare an aminophylline infusion at the usual 0.5 mg/kg/hr. It will be a good exercise for you to work out the right flow rate yourself.”

I injected a 500 mg ampule of aminophylline into a 500 ml bag of normal saline and then scratched my head a little working out the right flow rate for Mr Khan (whose weight couldn’t have been much more than 70 kg):

Once we’d established the IV infusion, Shariq asked me to additionally inject a bolus of Co-amxoiclav (1.2 g) as additional antibiotic cover. “We’ve done all we can for now. Let’s admit him to the HDU for observation”, he said. I went on to the next case.

Later, during one of those unpredictable early-morning lulls in the emergency department, I thought of Mr Khan and wondered how he was getting on. While strolling to the HDU, I ran into Shariq who was moving very quickly in the same direction with his bleep in his hand.

“If you’ve got a moment, this might be your patient,” he spurted. When we got there we could see the nurses escorting Mr Khan’s wife and sons to the relatives’ room and we started sprinting. Our initial management of his case had clearly failed, and Mr Khan was panting for breath under the mask. “He needs ventilatory support urgently,” said Shariq, running off to a store room, “take another ABG!”

By the time I’d got my ABG and was heading back from the blood gas analyser, Shariq and one of the HDU nurses, Dawn, were wheeling a bilevel PAP machine down the corridor towards the patient. I showed the ABG results to Shariq, who frowned and nodded while putting the PAP mask over Mr Khan’s face: ^{Positive Airway Pressure Ventilation}

Mr Khan was clearly hypoventilating, retaining CO₂ and both his acidaemia and hypoxaemia were worsening badly. “We’ll start him at 35% O₂ on IPAP/EPAP of 12/5 cmH₂O to see if he tolerates it, then start ramping the pressures up”, Shariq explained as Dawn adjusted the PAP machine accordingly. I stood out of the way while Shariq and Dawn expertly inserted an arterial line for further ABG analyses.

“Talk to his relatives and then you’d better get back to the ED”, Shariq said softly. Passing the relatives’ room on my way, I briefly explained to Mrs Khan and her sons that we had put Mr Khan on non-invasive ventilation because he wasn’t currently able to breathe adequately for himself due to the infection in his airways, and how this procedure would help him.

We had a serious road accident in the area later that morning and the ED was frantic for the rest of my shift. It was an hour or more after handover when things had settled down enough for me to leave for the day. I passed through the HDU to see how Mr Khan was getting on. After I’d left, Shariq and Dawn had ramped up the bilevel PAP pressures to 18/6 cmH₂0 IPAP/EPAP, where they remained. An ABG in the notes taken around that time showed some clinical improvement after the bilevel PAP had been administered:

He remained on PAP and the nebuliser and his most recent ABG - several hours later - showed fairly normal readings. The challenge ahead was to wean him off the ventilation and the drugs, but things were looking good for Mr Khan, who was now looking comfortable and relaxed. His future management would need reviewing to minimise the risks of further exacerbations.^{C O P D Quick Reference Guide}

I held his hand briefly and he managed a smile under his mask before I headed away to my car and home.