Noninvasive positive pressure ventilation in acute asthmatic attack

Table. 1—

Previous reports of noninvasive positive pressure ventilation(NPPV) in asthmatic patients

First author [Ref.]	Type of study	Patients n	Study design	Mode of ventilatory support/duration of application	Outcome
Meduri [44]	Prospective observational	17	A report of 17 episodes of status asthmaticus treated with NPPV over 3 yrs	CPAP mask with pressure support using commercial ventilator for 16 h	NPPV improved gas exchange in status asthmaticus
Fernandez [45]	Retrospective observational	33	Retrospecrive comparison of 22 patients treated with NPPV versus 11 patients treated with invasive mechanical ventilation	CPAP with or without pressure support, using commercial ventilators for 12 h	Improved gas exchange in both groups, with the possibility of prevented endotracheal intubation in NPPV group
Soroksky [46]	Prospective, randomised, sham controlled	30	15 patients on BiPAP compared with sham BiPAP with standard treatment	BiPAP circuit for 3 h	Improved FEV₁ and decreased hospitalisation rate in NPPV group
Soma [47]	Prospective randomised	44	Prospective comparison of low- and high-pressure groups to standard medical group	BiPAP circuit for 1 h	Improved FEV₁ with increasing pressure support

BiPAP: bilevel positive airway pressure; CPAP: continuous positive airway pressure; FEV₁: forced expiratory volume in 1 s.

Table. 2—

Risk factors and diagnostic criteria of severe asthma exacerbation

Patients at risk for respiratory failure who could benefit from NPPV trial

Diagnostic criteria of severe asthma (at least one of the following)

Use of accessory muscles

Paradoxical pulse >25 mmHg

f_C >110 beats·min⁻¹

Respiratory rate >25–30 breaths·min⁻¹

Limited ability to speak

PEF or FEV₁ <50% pred

Arterial oxygen saturation <91–92% with oxygen flow of ≤10 L·min⁻¹

Risk factors for severe asthma exacerbation

Recent hospitalisation

Prior ICU admission with mechanical ventilation

Poor adherence to therapy

High allergen exposure

NPPV: noninvasive positive pressure ventilation; f_C: cardiac frequency; PEF: peak expiratory flow; FEV₁: forced expiratory volume in 1 s; % pred: % predicted; ICU: intensive care unit.

Table. 3—

Absolute and relative contraindications for noninvasive positive pressure ventilation(NPPV) trial

Contraindications for NPPV trial

Absolute contraindications

Need for immediate endotracheal intubation

Decreased level of consciousness

Excess respiratory secretions and risk of aspiration

Past facial surgery precluding mask fitting

Relative contraindications

Haemodynamic instability

Severe hypoxia and/or hypercapnia, P_a,O₂/F_I,O₂ ratio of <200 mmHg, P_a,CO₂>60 mmHg

Poor patient cooperation

Severe agitation

Lack of trained or experienced staff

P_a,O₂: arterial oxygen tension; P_a,CO₂: arterial carbon dioxide tension; F_I,O₂: inspiratory oxygen fraction.

Table. 4—

Criteria for use of noninvasive positive pressure ventilation(NPPV)

Criteria for selecting severe asthmatic patients for NPPV trial^#

Tachypnea with respiratory rate >25 breaths·min⁻¹

Tachycardia with f_C >110 breaths·min⁻¹

Use of accessory muscles of respiration

Hypoxia with a P_a,O₂/F_I,O₂ ratio >200 mmHg

Hypercapnia with P_a,CO₂ <60 mmHg

FEV₁ <50% pred^¶

f_C: cardiac frequency; P_a,O₂: arterial oxygen tension; F_I,O₂: inspiratory oxygen fraction; P_a,CO₂: arterial carbon dioxide tension; FEV₁: forced expiratory volume in 1 s; % pred: % predicted. ^#: in the absence of absolute contraindication the presence of at least one criterion would suffice for an NPPV trial; ^¶: FEV₁ <50% pred after at least two consecutive nebulisations with salbutamol 2.5 mg and ipratropium 0.25 mg.