Respiratory Medicine Some pet peeves and other random topics Kyle Perrin
Overview 1. Acute asthma Severity assessment and management 2. Acute COPD NIV and other management 3. Respiratory problems in the obese patient 4. Antibiotics for respiratory infections Some sweeping generalisations
Acute severe asthma
Problems with assessment Studies show severity assessment is done poorly by SMOs, RMOs and nurses Over-reliance on the end of the bed assessment
Best markers on history Recent hospital admission Previous ICU admission (ever) β-agonist use last 24 hours
4 clinical markers of: 1. Severe asthma 2. Life-threatening asthma
Severe asthma Any one of 1. PEFR < 50% 2. Heart rate > 110/min 3. Resp rate > 24/min 4. Unable to complete a sentence
Any one of Life threatening asthma 1. PEFR < 33% 2. PaO 2 < 55mmHg despite oxygen 3. Normal or elevated PaCO 2 4. Drowsy, confused, exhausted, silent chest
Management Oxygen Bronchodilators Corticosteroids Magnesium IV Salbutamol? IV aminophylline? NIV?
Randomised controlled trial of high concentration versus titrated oxygen therapy in acute severe asthma Perrin et al Thorax 2011; 66: 937-41
The proportion of patients with a rise in PtCO 2 from baseline at 60 minutes High concentration n (%) Titrated n (%) Relative risk (95% CI) P value Change in PtCO 2 4 mmhg 22 (44%) 10 (19%) 2.3 (1.2 to 4.4) 0.006 Change in PtCO 2 8 mmhg 11 (22%) 3 (6%) 3.9 (1.2 to 13.1) 0.016
Improvement in PEF, PaCO 2 and clinical index before and after treatment 200 NEB group IV group PEF PaCO 2 Clinical index 55 15 160 10 120 45 80 5 40 0 1 35 0 1 Time (hours) 0 0 1 Salmeron et al. Am J Respir Crit Care Med 1994; 149: 1466-70.
Acute exacerbations of COPD
What are they? A change in the patient's baseline dyspnea, cough, and/or sputum that is beyond normal day-to-day variations, is acute in onset, and may warrant a change in regular medication
Pneumonia What are they not? LVF PE Pneumothorax
Standard management Titrated oxygen therapy Evidence grade A Short acting bronchodilators Evidence grade C Corticosteroids Evidence grade A Antibiotics Evidence grade B/C
John 68 years with moderately severe COPD FEV1 40% predicted Smokes 2-3 cigarettes a day Works as a petrol station attendant Normally SOB on moderate exertion
John Developed SOB, wheeze and cough with green sputum 4 days ago SOB worsened over the next 3 days By the morning of admission was SOB at rest and called the ambulance
Alert and afebrile Examination RR 32/min, not able to speak in sentences O2 sats 95% on 6L via a Hudson mask Chest hyper-resonant with quiet breath sounds FBC and CRP normal
Diagnosis Acute exacerbation COPD
1 st ABG After 20 minutes in ED (on 6L/min oxygen) ph 6.7 CO 2 81 O 2 122 HCO 3 23
Initial Management Prednisone Oral augmentin Nebulised bronchodilators O2 therapy titrated down to 3-4L/min NP Sats 88%
Review 1 hour later RR remains 30/min Sats 85-89% on 3-4L O2 2 nd ABG ph 6.8 CO2 84 O2 59 HCO3 28
What now? Most appropriate next management is ICU for consideration of invasive ventilation
Management Admitted to HDB, trial of NIV Poorly tolerant of mask, problem with leaks 3 further ABGs with little improvement Referred to ICU at 3am
The risk of serious adverse outcomes associated with hypoxaemia and hyperoxaemia in acute exacerbations of COPD Cameron L, Pilcher J, Weatherall M, Beasley R, Perrin K Postgraduate Medical Journal 2012 (in press)
Results Clinical data for 9716 patients were received from 232 units Overall mean age was 73 Mean FEV 1 % predicted was 42% In-hospital mortality was 7.7% 90day mortality was 13.9%
Results Many had severe acidosis with NIV used as the ceiling of care Some with metabolic acidosis receive NIV inappropriately while a proportion of patients who meet the RCT inclusion criteria of persisting respiratory acidosis do not receive NIV NIV was often given late
Results In 12% of cases managed with NIV who subsequently died there was no plan in the case notes of what the ceiling of treatment was in the event of failure of NIV In 30% of cases who died following NIV a DNR order was not signed
Results The observed mortality in patients treated with NIV was higher than patients matched by arterial blood gas ph who did not receive NIV Only 1% were intubated
Results In contrast, the group of patients for whom there exists the strongest evidence base for the effectiveness of NIV (ph range of 7.26-7.35) form only a minority of those overall receiving NIV
What's going on?
Obesity
Obstructive sleep apnoea Upper airway obstruction during sleep leads to frequent nocturnal arousals Main clinical symptom is daytime somnolence Other adverse physiological effects (cardiovascular) The majority of patients have normal daytime ventilation and gas exchange (normal PaO 2 and PaCO 2 )
Obesity-hypoventilation syndrome Definition Obesity associated with daytime hypercapnia (type 2 respiratory failure) in the absence of pulmonary disease or airflow obstruction May overlap with OSA but some obese people have predominantly OHS
Obesity-hypoventilation syndrome Can lead to Chronic hypoxia Polycythemia Pulmonary hypertension Right heart failure Death
Obesity-hypoventilation syndrome Why do some obese people develop daytime respiratory failure but most don't? Mechanical loading vs. Central control Patients with OHS normalise their PaCO 2 with voluntary hyperventilation with no change in lung mechanics/volumes
Obesity-hypoventilation syndrome Most people with OHS who present acutely will not have an established diagnosis Low threshold for an ABG in obese patients with hypoxaemia A screening serum bicarbonate is a useful test Bi-level NIV is the treatment of choice.
Normal
OSA
OSA with severe OHS
Antibiotics for respiratory infections
Case 1: David 26 year old non-smoking student 2-3 days of fever and malaise, now coughing rusty sputum with left sided pleurisy O/E Temp 39, RR 24/min, HR 90/min, BP 120/82 Sats 93% Left basal crackles WCC 16
Diagnosis and management? Mild CAP CURB65 score 0/5 Discharge on oral antibiotics amoxicillin and roxithromycin (CCDHB guidelines)
Given: IV cefuroxime Oral roxithromycin
Case 2 82 yr old widower lives alone and normally quite well,1 hour per day home help Ex smoker but no COPD 1 week of cough and fatigue then feverish for 2 days so stayed in bed Found by carer on floor.
Case 2 O/E slightly drowsy (GCS 14) but rousable AMT 6/10 BP 98/55, HR 110/min, RR 26/min Sats 90% on 4L/min Bilateral crackles Bloods WCC 24, CRP 228, Cr 124
Diagnosis and management? Severe CAP CURB65 score 4/5 Admit ICU consult to determine ceiling of care IV cefuroxime IV erythromycin
Given: IV cefuroxime Oral roxithromycin
Case 3 57 year old truck driver with longstanding idiopathic bronchiectasis Normally produces 1-2 cups of green sputum per day Unwell for 3 days with increased sputum volume and darker colour. Increased SOB but no fever
Case 3 O/E Afebrile BP and HR normal Sats 95% RA, RR 20/min Coarse crackles both lung bases Bloods all normal
Diagnosis and management? Exacerbation of bronchiectasis with no pneumonia Review previous sputum samples (in his case usually grows haemophillus) Augmentin a reasonable empirical treatment No need for atypical cover if no pneumonia
Given: IV cefuroxime Oral roxithromycin
Case 4 71 year old, lives with husband, diagnosed with COPD (FEV1 around 40% predicted) Manages all daily activities but SOB up stairs Unwell with cold 3 days ago, now coughing green sputum and breathless with daily activities
Case 4 O/E Alert and speaking sentences Fruity cough Afebrile RR 24/min, sats 90% RA, BP and HR normal Hyper-inflated with reduced breath sounds but nothing else
Diagnosis and management? Acute exacerbation of COPD (not pneumonia) Oral antibiotics, choose one from: Augmentin Doxycyline Cefaclor
Given: IV cefuroxime Oral roxithromycin
Message Avoid the term chest infection Be as precise as you can with what you are treating and do a severity assessment in CAP There will always be grey areas, so some patients need broad spectrum IV treatment at the front door, but modify the next day!