Page 32 - Škrgat, Sabina, ed. 2023. Severe Asthma Forum - Monitoring and Treatable Traits in Severe Asthma. Koper: University of Primorska Press. Severe Asthma Forum, 2
P. 32
point in rapid shallow breathing, as seen in h y- PaO2, alveolar-arterial pressure gradient of
perventilation type of DB, typically induces oxygen, dead space volume/tidal volume and
severe asthma forum 2: severe asthma - monitoring and treatable traits in severe asthma ventilatory inefficiency characterized by high arterial-ETCO2 pressure gradient at end-ex-
minute ventilation/CO2 output (VE/VCO2 ercise. These findings can help differentiate
slope), with generally a normal dead volume/ from other conditions in which chronic h y-
tidal volume ratio. Important to notice is that perventilation occurs, as in patients with in-
increase in end-inspiratory and end-expira- creased dead space ventilation, such as those
tory lung volumes, as seen in hyperinflation, with heart failure or pulmonary hyperten-
therefore reduces inspiratory capacity and sion. Similarly, an identified marker of disease
possibly contributes to the troublesome dysp- severity in patients with heart failure due to
noea sensation regardless of the existence of left ventricular systolic dysfunction is period-
true hypocapnia.2 However, other types of ic breathing. As happens in DB, it may devel-
DB with normal PaCO2 and VE/VCO2 have op at rest or during exercise and last through-
been described, in particular, erratic ventila- out the entire period of incremental workload
tion with wide and irregular variations of tid- or disappear facing the end of exercise. How-
al volumes and breathing frequency over the ever, the characteristic periodicity of waxing
progression of effort during CPET.52 Bould- and waning of tidal volumes (minute venti-
ing and colleagues suggested a classification of lation, as well) present in periodic breathing
DB patterns according to incremental CPET is in sharp contrast to the unpredictable and
data, as well as change in breathing frequen- irregular breathing pattern of DB. Further,
cy, tidal volumes, and respiratory muscle me- thoracic-dominant patterns may be present
chanics before and after exercise.2 Analysis of in morbidly obese patients in response to their
ventilation patterns on CPET may contrib- low abdominal compliance. At last, one must
ute in differentiating types of breathing dys- consider asthma and COPD, where patients
regulation in people with dyspnoea present may develop thoracic-dominant and forced
in the absence of deconditioning as a post– expiratory breathing patterns as a physio-
acute-phase sequelae of mild infection with logical adaptive response to pulmonary hy-
SARS-CoV2 virus. Nonetheless, one should perinflation, in which case they should not be
consider its highly demanding resources and regarded as dysfunctional.12 Ionescu and col-
setups in the context of the high prevalence of leagues proposed a diagnostic and therapeu-
post-COVID-19, as well as the fact that “ex- tic algorithm for patients with unexplained
ercising at physiological limits may exacer- dyspnoea. Starting with high clinical suspi-
bate symptoms in these patients, also referred cion of DB, electrocardiography, chest radi-
to as postexercise malaise”.12,53 An example ography and spirometry test should be one
of CPET in a normal subject compared with of the first tools to exclude or prove possi-
a person with limited tidal volume and high ble cardiopulmonary etiologies of dyspnoea.
breathing frequency and a person with dys- If symptoms persist after adequate manage-
functional breathing is showed in Figure 4.51 ment, the next step is CPET. If there is good
fitness on CPET with no evidence of DB, reas-
Differential diagnosis should always and sure the patient and discharge. If there are ab-
firstly include all diseases that can be the cause normalities present in terms of cardiac, venti-
of dyspnoea in the first place, and also, may latory, gas exchange or metabolic parameters
be associated with DB. The finding of erratic on CPET, proceed to targeted management.
breathing on CPET cannot exclude accompa- If there are, in addition or alone, one or more
nying disease, nor can it precisely confirm DB features of DB identified on CPET, refer the
diagnosis. Most frequently patients with DB patient to a chest physiotherapist, with target-
present with resting hypocapnia and normal ed therapeutic intervention.12
perventilation type of DB, typically induces oxygen, dead space volume/tidal volume and
severe asthma forum 2: severe asthma - monitoring and treatable traits in severe asthma ventilatory inefficiency characterized by high arterial-ETCO2 pressure gradient at end-ex-
minute ventilation/CO2 output (VE/VCO2 ercise. These findings can help differentiate
slope), with generally a normal dead volume/ from other conditions in which chronic h y-
tidal volume ratio. Important to notice is that perventilation occurs, as in patients with in-
increase in end-inspiratory and end-expira- creased dead space ventilation, such as those
tory lung volumes, as seen in hyperinflation, with heart failure or pulmonary hyperten-
therefore reduces inspiratory capacity and sion. Similarly, an identified marker of disease
possibly contributes to the troublesome dysp- severity in patients with heart failure due to
noea sensation regardless of the existence of left ventricular systolic dysfunction is period-
true hypocapnia.2 However, other types of ic breathing. As happens in DB, it may devel-
DB with normal PaCO2 and VE/VCO2 have op at rest or during exercise and last through-
been described, in particular, erratic ventila- out the entire period of incremental workload
tion with wide and irregular variations of tid- or disappear facing the end of exercise. How-
al volumes and breathing frequency over the ever, the characteristic periodicity of waxing
progression of effort during CPET.52 Bould- and waning of tidal volumes (minute venti-
ing and colleagues suggested a classification of lation, as well) present in periodic breathing
DB patterns according to incremental CPET is in sharp contrast to the unpredictable and
data, as well as change in breathing frequen- irregular breathing pattern of DB. Further,
cy, tidal volumes, and respiratory muscle me- thoracic-dominant patterns may be present
chanics before and after exercise.2 Analysis of in morbidly obese patients in response to their
ventilation patterns on CPET may contrib- low abdominal compliance. At last, one must
ute in differentiating types of breathing dys- consider asthma and COPD, where patients
regulation in people with dyspnoea present may develop thoracic-dominant and forced
in the absence of deconditioning as a post– expiratory breathing patterns as a physio-
acute-phase sequelae of mild infection with logical adaptive response to pulmonary hy-
SARS-CoV2 virus. Nonetheless, one should perinflation, in which case they should not be
consider its highly demanding resources and regarded as dysfunctional.12 Ionescu and col-
setups in the context of the high prevalence of leagues proposed a diagnostic and therapeu-
post-COVID-19, as well as the fact that “ex- tic algorithm for patients with unexplained
ercising at physiological limits may exacer- dyspnoea. Starting with high clinical suspi-
bate symptoms in these patients, also referred cion of DB, electrocardiography, chest radi-
to as postexercise malaise”.12,53 An example ography and spirometry test should be one
of CPET in a normal subject compared with of the first tools to exclude or prove possi-
a person with limited tidal volume and high ble cardiopulmonary etiologies of dyspnoea.
breathing frequency and a person with dys- If symptoms persist after adequate manage-
functional breathing is showed in Figure 4.51 ment, the next step is CPET. If there is good
fitness on CPET with no evidence of DB, reas-
Differential diagnosis should always and sure the patient and discharge. If there are ab-
firstly include all diseases that can be the cause normalities present in terms of cardiac, venti-
of dyspnoea in the first place, and also, may latory, gas exchange or metabolic parameters
be associated with DB. The finding of erratic on CPET, proceed to targeted management.
breathing on CPET cannot exclude accompa- If there are, in addition or alone, one or more
nying disease, nor can it precisely confirm DB features of DB identified on CPET, refer the
diagnosis. Most frequently patients with DB patient to a chest physiotherapist, with target-
present with resting hypocapnia and normal ed therapeutic intervention.12
