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Ventilatory management of acute hypercapnic respiratory failure in adults: BTS , ICS guidelines

Ventilatory management of acute hypercapnic respiratory failure in adults: BTS , ICS guidelines

AHRF ( acute hypercapnic respiratory failure) results from an inability of the respiratory pump, in concert with the lungs, to provide sufficient alveolar ventilation to maintain a normal arterial PCO2. Co-existent hypoxaemia is usually mild and easily corrected. Conventionally, a pH <7.35 and a PCO2 >6.5 kPa define acute respiratory acidosis and, when persisting after initial medical therapy, have been used as threshold values for considering the use of non-invasive ventilation. More severe degrees of acidosis, such as pH<7.25, have been used as a threshold for considering provision of IMV

In April 2016, British Thoracic Society (BTS)/International Continence Society (ICS) issued guidelines on the ventilatory management of acute hypercapnic respiratory failure in adults. Following are its major recommendations :

 Principles of Mechanical Ventilation

Modes of Mechanical Ventilation

Recommendation

  1. Pressure-targeted ventilators are the devices of choice for acute non-invasive (positive pressure) ventilation (NIV) (Grade B).

Good Practice Points

  • Both pressure support (PS) and pressure control modes are effective.
  • Only ventilators designed specifically to deliver NIV should be used.

Choice of Interface for NIV

Recommendation

  1. A full face mask (FFM) should usually be the first type of interface used (Grade D).

Good Practice Points

  • A range of masks and sizes is required and staff involved in delivering NIV need training in and experience of using them.
  • NIV circuits must allow adequate clearance of exhaled air through an exhalation valve or an integral exhalation port on the mask.

Indications for and Contra-indications to NIV in Acute Hypercapnic Respiratory Failure (AHRF)

Recommendation

  1. The presence of adverse features increases the risk of NIV failure and should prompt consideration of placement in high dependency unit (HDU)/intensive care unit (ICU) (Grade C).

Good Practice Points

  • Adverse features should not, on their own, lead to withholding a trial of NIV.
  • The presence of relative contra-indications necessitates a higher level of supervision, consideration of placement in HDU/ICU and an early appraisal of whether to continue NIV or to convert to invasive mechanical ventilation (IMV).

Monitoring during NIV

Good Practice Points

  • Oxygen saturation should be continuously monitored.
  • Intermittent measurement of partial pressure of carbon dioxide (pCO2) and pH is required.
  • Electrocardiogram (ECG) monitoring is advised if the patient has a pulse rate >120 bpm or if there is dysrhythmia or possible cardiomyopathy.

Supplemental Oxygen Therapy with NIV

Recommendations

  1. Oxygen enrichment should be adjusted to achieve oxygen saturation (SaO2) 88% to 92% in all causes of AHRF treated by NIV (Grade A).
  2. Oxygen should be entrained as close to the patient as possible (Grade C).

Good Practice Points

  • As gas exchange will improve with increased alveolar ventilation, NIV settings should be optimised before increasing the fractional inspired concentration of oxygen (FiO2).
  • The flow rate of supplemental oxygen may need to be increased when ventilatory pressure is increased to maintain the same SaO2 target.
  • Mask leak and delayed triggering may be caused by oxygen flow rates >4 L/min, which risks promoting or exacerbating patient-ventilator asynchrony. The requirement for high flow rates should prompt a careful check for patient-ventilator asynchrony.
  • A ventilator with an integral oxygen blender is recommended if oxygen at 4 L/min fails to maintain SaO2 >88%.

Humidification with NIV

Recommendation

  1. Humidification is not routinely required (Grade D).

Good Practice Point

  • Heated humidification should be considered if the patient reports mucosal dryness or if respiratory secretions are thick and tenacious.

Bronchodilator Therapy with NIV

Good Practice Points

  • Nebulised drugs should normally be administered during breaks from NIV.
  • If the patient is dependent on NIV, bronchodilator drugs can be given via a nebuliser inserted into the ventilator tubing.

Sedation with NIV

Recommendations

  1. Sedation should only be used with close monitoring (Grade D).
  2. Infused sedative/anxiolytic drugs should only be used in an HDU or ICU setting (Grade D).
  3. If intubation is not intended should NIV fail, then sedation/anxiolysis is indicated for symptom control in the distressed or agitated patient (Grade D).

Good Practice Point

  • In the agitated/distressed and/or tachypnoeic individual on NIV, intravenous morphine 2.5–5 mg (± benzodiazepine) may provide symptom relief and may improve tolerance of NIV.

NIV Complications

Good Practice Points

  • Minor complications are common but those of a serious nature are rare. Patients should be frequently assessed to identify potential complications of NIV.
  • Care is needed to avoid overtightening of masks.
  • Previous episodes of ventilator-associated pneumothorax warrant consideration of admission to HDU/ICU and use of NIV at lower than normal inspiratory pressures.
  • The development of a pneumothorax usually requires intercostal drainage and review of whether to continue with NIV.

Sputum Retention

Recommendations

  1. In patients with neuromuscular disease (NMD), mechanical insufflation and exsufflation should be used, in addition to standard physiotherapy techniques, when cough is ineffective and there is sputum retention (Grade B).
  2. Mini-tracheostomy may have a role in aiding secretion clearance in cases of weak cough (NMD/chest wall disease [CWD]) or excessive amounts (chronic obstructive pulmonary disease [COPD], cystic fibrosis [CF]) (Grade D).

Modes of IMV

Recommendations

  1. Spontaneous breathing should be established as soon as possible in all causes of AHRF (Grade C).
  2. Controlled IMV may need to be continued in some patients due to severe airflow obstruction, weak muscles leading to poor triggering or to correct chronic hypercapnia (Grade C).

Good Practice Point

  • In obstructive diseases, controlled IMV should be continued until airway resistance falls.

Invasive Ventilation Strategy

Recommendations

  1. During controlled ventilation, dynamic hyperinflation should be minimised by prolonging expiratory time (Inspiratory/expiratory time [I:E] ratio 1: 3 or greater) and setting a low frequency (10–15 breaths/min) (Grade C).
  2. Permissive hypercapnia (aiming for pH 7.2–7.25) may be required to avoid high airway pressures when airflow obstruction is severe (Grade D).
  3. Carbonic anhydrase inhibitors should not be routinely used in AHRF (Grade C).

Positive end Expiratory Pressure

Recommendation

  1. Applied extrinsic positive end expiratory pressure (ePEEP) should not normally exceed 12 cm (Grade C).

Sedation in IMV

Recommendation

  1. Sedation should be titrated to a specific level of alertness (Grade B).

Patient-Ventilator Asynchrony

Recommendations

  1. Ventilator asynchrony should be considered in all agitated patients (including NIV) (Grade C).
  2. As patients recover from AHRF, ventilator requirements change and ventilator settings should be reviewed regularly (Grade C).

Use and Timing of a Tracheostomy

Recommendations

  1. Performing routine tracheostomy within 7 days of initiating IMV is not recommended (Grade A).
  2. The need for and timing of a tracheostomy should be individualised (Grade D).

Good Practice Points

  • In AHRF due to COPD, and in many patients with NMD or obesity hypoventilation syndrome (OHS), NIV supported extubation should be employed in preference to inserting a tracheostomy.
  • In AHRF due to NMD, alongside discussion with the patient and carers, the decision to perform tracheostomy should be multidisciplinary and should involve discussion with a home ventilation unit.

Management of Hypercapnic Respiratory Failure

Prevention of AHRF in Acute Exacerbation of COPD (AECOPD)

Recommendation

  1. In AHRF due to AECOPD controlled oxygen therapy should be used to achieve target saturations of 88% to 92% (Grade A).

Good Practice Points

  • Controlled oxygen therapy should be used to achieve a target saturation of 88% to 92% in ALL causes of AHRF.

Role of NIV in AECOPD

Recommendations

  1. For most patients with AECOPD, the initial management should be optimal medical therapy and targeting an oxygen saturation of 88% to 92% (Grade A).
  2. NIV should be started when pH <7.35 and pCO2 >6.5 kPa persist or develop despite optimal medical therapy (Grade A).
  3. Severe acidosis alone does not preclude a trial of NIV in an appropriate area with ready access to staff who can perform safe endotracheal intubation (Grade B).
  4. The use of NIV should not delay escalation to IMV when this is more appropriate (Grade C).
  5. The practice of NIV should be regularly audited to maintain standards (Grade C).

Starting NIV in COPD

Good Practice Points

  • Arterial blood gas (ABG) measurement is needed prior to and following starting NIV.
  • Chest radiography is recommended but should not delay initiation of NIV in severe acidosis.
  • Reversible causes for respiratory failure should be sought and treated appropriately.
  • At the start of treatment, an individualised patient plan (involving the patient wherever possible) should document agreed measures to be taken in the event of NIV failure.

Prognostic Features Relating to Use of NIV in COPD

Recommendations

  1. Advanced age alone should not preclude a trial of NIV (Grade A).
  2. Worsening physiological parameters, particularly pH and respiratory rate (RR), indicate the need to change the management strategy. This includes clinical review, change of interface, adjustment of ventilator settings and considering proceeding to endotracheal intubation (Grade A).

Good Practice Point

  • If sleep-disordered breathing pre-dates AHRF, or evidence of it complicates an episode, the use of a controlled mode of NIV overnight is recommended.

Duration of NIV in COPD

Recommendation

  1. NIV can be discontinued when there has been normalisation of pH and pCO2 and a general improvement in the patient’s condition (Grade B).

Good Practice Points

  • Time on NIV should be maximised in the first 24 h depending on patient tolerance and/or complications.
  • NIV use during the day can be tapered in the following 2 to 3 days, depending on pCO2 self-ventilating, before being discontinued overnight.

Optimising NIV Delivery and Technical Considerations

Good Practice Point

  • Before considering NIV to have failed, always check that common technical issues have been addressed and ventilator settings are optimal (see Table 3 in the original guideline document).

Indications for IMV in AECOPD

Recommendations

  1. IMV should be considered if there is persistent or deteriorating acidosis despite attempts to optimise delivery of NIV (Grade A).
  2. Intubation should be performed in respiratory arrest or peri-arrest unless there is rapid recovery from manual ventilation/provision of NIV (Grade D).
  3. Intubation is indicated in management of AHRF when it is impossible to fit/use a non-invasive interface, for example, severe facial deformity, fixed upper airway obstruction, facial burns (Grade D).
  4. Intubation is indicated where risk/benefit analysis by an experienced clinician favours a better outcome with IMV than with NIV (Grade D).

Outcome following NIV or IMV in AECOPD

Recommendations

  1. Prognostic tools may be helpful to inform discussion regarding prognosis and with regard to the appropriateness of IMV but with the caveat that such tools are poorly predictive for individual patient use (Grade B).
  2. Clinicians should be aware that they are likely to underestimate survival in AECOPD treated by IMV (Grade B).
  3. Clinicians should discuss management of possible future episodes of AHRF with patients, following an episode requiring ventilatory support, because there is a high risk of recurrence (Grade B).

Acute Asthma

Recommendations

  1. NIV should not be used in patients with acute asthma exacerbations and AHRF (Grade C).
  2. Acute (or acute on chronic) episodes of hypercapnia may complicate chronic asthma. This condition closely resembles COPD and should be managed as such (Grade D).

Non-CF Bronchiectasis

Recommendations

  1. In patients with non-CF bronchiectasis and AHRF, controlled oxygen therapy should be used (Grade D).
  2. In patients with non-CF bronchiectasis, NIV should be started in AHRF using the same criteria as in AECOPD (Grade B).
  3. In patients with non-CF bronchiectasis, NIV should usually be tried before resorting to IMV in those with less severe physiological disturbance (Grade C).
  4. In non-CF bronchiectasis, the patient’s clinical condition prior to the episode of AHRF, and the reason for the acute deterioration, should be evaluated and used to inform the decision about providing IMV (Grade C).

Good Practice Points

  • In patients with non-CF bronchiectasis, the precipitating cause is important in determining short-term prognosis.
  • Health status prior to the episode of AHRF is an important predictor of outcome.

CF

Recommendations

  1. In patients with CF, controlled oxygen therapy should be used in AHRF (Grade D).
  2. In patients with CF, NIV is the treatment of choice when ventilatory support is needed (Grade C).
  3. In patients with CF, specialised physiotherapy is needed to aid sputum clearance (Grade D).
  4. In patients with CF, a mini-tracheostomy combined with NIV may offer greater chance of survival than resorting to IMV (Grade D).

Restrictive Lung Diseases

NMD and CWD

Recommendations

  1. Controlled oxygen therapy should be used in patients with NMD or CWD and AHRF (Grade D).
  2. NIV should almost always be trialled in the acutely unwell patients with NMD or CWD with hypercapnia. Do not wait for acidosis to develop (Grade D).
  3. In patients with NMD or CWD, NIV should be considered in acute illness when vital capacity (VC) is known to be <1 L and RR >20, even if normocapnic (Grade D).
  4. In patients with NMD or CWD, consider controlled ventilation as triggering may be ineffective (Grade D).
  5. In NMD or CWD, unless escalation to IMV is not desired by the patient, or is deemed to be inappropriate, intubation should not be delayed if NIV is failing (Grade D).

Good Practice Points

  • Individuals with NMD and CWD who present with AHRF should not be denied acute NIV.
  • NIV is the ventilation mode of choice because patients with NMD or CWD tolerate it well and because extubation from IMV may be difficult.
  • In patients with NMD or CWD, deterioration may be rapid or sudden, making HDU/ICU placement for therapy more appropriate.
  • In patients with NMD or CWD, senior/experienced input is needed in care planning and is essential if differences in opinion exist or develop between medical staff and patient representatives.
  • In patients with NMD, it should be anticipated that bulbar dysfunction and communication difficulties, if present, will make NIV delivery difficult, and may make it impossible.
  • Discussion about NIV and IMV, and patients’ wishes with respect to cardiopulmonary resuscitation, should occur as part of routine care of patients with NMD or CWD.
  • In patients with NMD or CWD, nocturnal NIV should usually be continued following an episode of AHRF, pending discussion with a home ventilation service.

NIV Failure and Discontinuing NIV following Recovery in NMD and CWD

Good Practice Points

  • In patients with NMD or CWD, intolerance of the mask and severe dyspnoea are less likely to cause NIV failure. Bulbar dysfunction makes NIV failure more likely.
  • Deterioration in patients with NMD or CWD may be very sudden. Difficulty achieving adequate oxygenation or rapid desaturation during a break from NIV are important warning signs.
  • In patients with NMD or CWD, the presence of bulbar dysfunction, more profound hypoxaemia or rapid desaturation during NIV breaks, suggests that placement in HDU/ICU is indicated.

IMV in NMD/CWD

Recommendations

  1. In patients with NMD or CWD, senior staff should be involved in decision-making, in conjunction with home mechanical ventilation specialists, if experience is limited, and especially when the appropriateness of IMV is questioned (Grade D).
  2. Advance care planning, particularly around the potential future use of IMV, is recommended in patients with progressive NMD or CWD. This may best be supported by elective referral to a home ventilation service (Grade D).

IMV Strategy in NMD and CWD

Good Practice Points

  • Patients with NMD usually require low levels of PS.
  • Patients with chest wall deformity usually require higher levels of PS.
  • PEEP in the range of 5 to 10 is commonly required to increase residual volume and reduce oxygen dependency in both patient groups.

Obesity Hypoventilation Syndrome (OHS)

Recommendations

  1. Controlled oxygen therapy should be used in patients with OHS and AHRF (Grade D).
  2. In patients with OHS, NIV should be started in AHRF using the same criteria as in AECOPD (Grade B).
  3. NIV is indicated in some hospitalised obese hypercapnic patients with daytime somnolence, sleep disordered breathing and/or right heart failure in the absence of acidosis (Grade D).

NIV Settings and Placement in OHS

Good Practice Points

  • High inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) settings are commonly required in patients with OHS (e.g., IPAP >30, EPAP >8).
  • Volume control (or volume assured) modes of providing NIV may be more effective when high inflation pressures are required.

NIV Failure in OHS

Good Practice Points

  • Fluid overload commonly contributes to ventilatory failure in patients with OHS, and its degree is easily underestimated.
  • Forced diuresis may be useful.
  • As the risk of NIV failure is greater, and intubation may be more difficult, placement in HDU/ICU for NIV is recommended.

Discontinuing NIV in OHS

Good Practice Points

  • NIV can be discontinued, as in patients with AECOPD.
  • Many patients with AHRF secondary to OHS will require long-term domiciliary support (continuous positive airways pressure [CPAP] or NIV).
  • Following an episode of AHRF referral to a home ventilation service is recommended.

IMV Strategy in OHS

Good Practice Points

  • In patients with OHS, pressure controlled MV is recommended initially.
  • In patients with OHS, high PEEP settings may be needed to recruit collapsed lung units and correct hypoxaemia.
  • In patients with OHS, a forced diuresis is often indicated.

Weaning from IMV

Introduction

Recommendations

  1. Treating the precipitant cause of AHRF, normalising pH, correcting chronic hypercapnia and addressing fluid overload should all occur before weaning is started (Grade D).
  2. A brain natriuretic peptide (BNP)-directed fluid management strategy should be considered in patients with known left ventricular dysfunction (Grade B).

Weaning Methods

Recommendations

  1. Assessment of the readiness for weaning should be undertaken daily (Grade C).
  2. A switch from controlled to assisted IMV should be made as soon as patient recovery allows (Grade C).
  3. IMV patients should have a documented weaning plan (Grade B).

Assessing Readiness for Discontinuation of Mechanical Ventilation

Recommendations

  1. A 30 min spontaneous breathing trial (SBT) should be used to assess suitability for extubation (Grade B).
  2. Factors including upper airway patency, bulbar function, sputum load and cough effectiveness should be considered prior to attempted extubation (Grade D).

Outcome following Extubation

Recommendation

  1. Care is needed to identify factors that increase the risk of extubation failure so that additional support, such as NIV or cough assist, can be provided (Grade B).

Weaning Protocols

Recommendations

  1. Although an organised and systematic approach to weaning is desirable, protocols should be used with caution in patients with AHRF (Grade B).
  2. The use of computerised weaning cannot be recommended in AHRF (Grade D).

Use of NIV in the ICU

Planned NIV to Speed Weaning from IMV

Recommendations

  1. NIV is recommended to aid weaning from IMV in patients with AHRF secondary to COPD (Grade B).
  2. In other causes of AHRF, NIV may have a role in shortening the duration of IMV when local expertise in its use exists (and of cough assist when indicated) and there are features present that indicate extubation is likely to be successful (Grade D).

NIV in High-Risk Patients

Recommendation

  1. Prophylactic use of NIV should be considered to provide post-extubation support in patients with identified risk factors for extubation failure (Grade B).

NIV as ‘Rescue’ Therapy Post-extubation

Recommendations

  1. NIV should not be used routinely for unexpected post-extubation respiratory failure (Grade B).
  2. In COPD, a trial of NIV may be justified for unexpected post-extubation respiratory failure where local expertise exists (Grade D).

Care Planning and Delivery of Care

Appropriate Care Environments for the Delivery of NIV

Recommendations

  1. NIV services should operate under a single clinical lead having formal working links with the ICU (Grade D).
  2. The severity of AHRF, and evidence of other organ dysfunction, should influence the choice of care environment (Grade C).
  3. NIV should take place in a clinical environment with enhanced nursing and monitoring facilities that are beyond those of a general medical ward (Grade C).
  4. Initial care plans should include robust arrangements for escalation, anticipating that around 20% of AHRF cases should be managed in a level 2 or 3 environment (Grade C).

Good Practice Points

  • A 2- to 4-bedded designated NIV unit (located within a medical high dependency area or within a respiratory ward with enhanced staffing levels) provides a sound basis for the provision of NIV in a DGH serving a population of 250 000 and with an average prevalence of COPD.
  • Areas providing NIV should have a process for audit and interdisciplinary communication.

Palliative Care and Advanced Care Planning

Recommendations

  1. Clinicians delivering NIV or IMV should have ready access to palliative medicine (Grade D).
  2. Multidisciplinary advance care planning should be an integral part of the routine outpatient management of progressive or advanced disease and care plans should be reviewed on presentation during an episode of AHRF (Grade D).
  3. The use of NIV may allow time to establish patient preference with regard to escalation to IMV (Grade D).

End of Life Care

Good Practice Points

  • Although removal of the NIV mask may be agreed as preferable, a dignified and comfortable death is possible with it in place.
  • Clinicians delivering NIV or IMV should have training in end-of-life care and the support of palliative care teams.

Novel Therapies

Extracorporeal CO2 Removal (ECCO2R)

Recommendation

  1. If local expertise exists, ECCO2R might be considered:
    • If, despite attempts to optimise IMV using lung protective strategies, severe hypercapnic acidosis (pH <7.15) persists (Grade D)
    • When ‘lung protective ventilation’ is needed but hypercapnia is contra-indicated, for example, in patients with coexistent brain injury (Grade D)
    • For IMV patients awaiting a lung transplant (Grade D)

Good Practice Point

  • ECCO2R is an experimental therapy and should only be used by specialist intensive care teams trained in its use, and where additional governance arrangements are in place, or in the setting of a research trial.

Helium/Oxygen Ventilation

Recommendation

  1. Heliox should not be used routinely in the management of AHRF. (Grade B)

You can read the full Guideline by clicking on the following link :

Davidson AC, Banham S, Elliott M, Kennedy D, Gelder C, Glossop A, Church AC, Creagh-Brown B, Dodd JW, Felton T, Foëx B, Mansfield L, McDonnell L, Parker R, Patterson CM, Sovani M, Thomas L. BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults. Thorax. 2016 Apr;71 Suppl 2:ii1-ii35. [300 references] PubMed

Source: British Thoracic Society (BTS)/International Continence Society (ICS)
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