Table 1 Studies on the health effects of various HVAC interventions for inpatients

Burch & DePasquale 1959, [31],

“Influence of air conditioning on hospitalized patients”

Clinical trial & report of four exemplary cases

Analysis of the clinical course of patients depending on admission to an air-conditioned ward or non-air-conditioned ward

• (I) Ward no°1: Air conditioning (24 °C)

• (C) Ward no°2: No air conditioning (30 °C)

• (S) General ward

• (D) Whole hospital stay

• Intervention: n = 88*

• Control:

n = 75*

Positive Effects:

• Lower blood pressure & lower heart rate (statistically non-significant)

• Favourable effects in 71 of 88 patients

• Patients with congestive heart disease, asthma and chronic debilitation profited most

• Easier nursing, reduction of odours, noise reduction (closed ward), improved morale

• Cases 1–3: Improved walking, improved oedema, improved sleep, improved dyspnea, improved thermal comfort

Negative Effects:

• Reports of “getting a cold”, non-optimal thermal comfort, case 4: Development of a “cold”

• *Some patients were shifted between intervention groups

• Only Afro-American women were included in the study

• Various confounders are reported in the discussion

Burch & Hyman 1959, [32],

“Influence of a hot and humid environment on the patient with coronary heart disease”

Clinical trial

Analysis of cardiac output/cardiac function either in a hot, non-air-conditioned ward or on an air-conditioned ward

• (I) Ward no°1: Air conditioning (23.3 °C)

• (C) Ward no°2: No air conditioning (33.8 °C)

• (S) General ward

• (D) At least 1 h in each experimental condition

N = 5*

• Cardiac volume output and cardiac function were greater in all patients in the hot ward. Big individual differences were observed

• Air-conditioned ward had a resting/recovery effect on the heart even if patients were acclimatised to hot weather conditions

• *All 5 patients were sequentially analysed in the hot and also in the air-conditioned ward

-All patients were initially admitted to the hot ward

− 2 patients were analysed first in the cold and subsequently in the hot ward

− 3 patients were analysed in the hot ward and subsequently in the cold ward

-Patients had at least 1 h to acclimatise on both wards

• No patient with congestive heart failure was enrolled

• No cardiological diagnosis was stated as a primary diagnosis for all patients

Carli et al. 1986, [33],

“An investigation of factors affecting postoperative rewarming of adult patients”

Clinical trial

Analysis of the influence of a controlled environment in the recovery room on the rewarming rate of post-surgical patients

• (I) “Controlled ventilation and humidification system”, hospital 1, (22.9 °C)

• (C) Regular recovery room without air conditioning, hospital 2, (22.4 °C)

• (S) Post-surgery recovery room

• (D) At least 1 h

• Intervention: n = 100

• Control:

n = 100

• HVAC use had no significant influence on the rewarming rate

• No difference in entrance or transfer to ward temperature was found

• Age and type of anaesthesia were significant variables for the rewarming rate

• Older patients rewarm slower after surgery than young patients

• No difference found for shivering

• No correlation between rewarming, duration of surgery and body fat

• No matching; allocation to intervention on a pragmatic basis

• Only minor temperature difference between the two interventions

• Exclusion of patients with endocrine abnormalities, extreme obesity and fever

Witt et al. 2018 [34],

“Climate-controlled hospital patient rooms reduce indoor heat stress in patients with chronic obstructive pulmonary diseases and prevent an increased cardiorespiratory coupling”

Clinical trial

Analysis of the influence of an air-conditioned patient room on cardio-respiratory parameters in COPD patients

• (I) Regular patient room with convection free air conditioning (radiant cooling)

(23 °C)

• (C) Regular patient room without air conditioning

(24.9° - 30.5 °C)

• (S) General ward

• (D) While 3-day heat waves

• Intervention: n = 13

• Control:

n = 7

• Lower heart rate, lower respiratory rate

• Increased heart rate variability

• Decreased cardiorespiratory coupling

• No matching; allocation to intervention on a pragmatic basis

• Only patients with COPD exacerbation were included

Witt et al. 2019 [30],

“Accelerated patient recovery through improved indoor environment in hospital patient rooms - an adaptation strategy to urban heat in view of climate change”

Clinical trial

Analysis of the influence of an air-conditioned patient room on the clinical course, vital signs and mobility of patients with respiratory disease

• (I) Convection free air conditioning (radiant cooling)

(23 °C)

• (C) Regular patient room without air conditioning

(15.9° - 28.2 °C)

• (S) General ward

• (D) Whole hospital stay

• Intervention: n = 63

• Control:

n = 53

• Statistically significant reduction in length of stay (2 days)

• Lower body temperature, lower diastolic blood pressure, lower fluid intake

• Higher heart rate

• No matching; allocation to intervention on a pragmatic basis

• Only patients with respiratory disease are included

Misset et al. 2006 [35],

“Mortality of patients with heatstroke admitted to intensive care units during the 2003 heat wave in France: A national multiple-center risk-factor study”

Cross-sectional

Analysis of risk factors for positive or negative outcomes in heat stroke

• (I) Not fully applicable: Intensive care units with air conditioning*

• (C) Not fully applicable: Intensive care units without air conditioning*

• (S) Intensive care unit

• (D) Whole intensive care unit stay

• Intervention: n = 158

• Control:

n = 187

• Treatment of heat illness patients in wards without air conditioning leads to a 76% increased risk of death

• Factors associated with survival of heat illness: Intensive care unit with air conditioning, psychiatric co-morbidity, use of antidepressant drugs, alcohol abuse

• The positive effect of air conditioning is not confounded by university status of hospitals, urban or rural location, number of beds and medical staff or number of admissions while study period

• *Use of “external body cooling methods” was reported in all cases

Charoenpong et al. 2013, [36],

“Complication of active rewarming in hypothermia from hypothyroidism”

Case report

Describing the clinical course and clinical adverse effects of rewarming a patient in the context of hypothermia due to hypothyroidism

• (I) Air conditioning (warm humidified air) and other methods

• (C) Not applicable

• (S) Intensive care unit

• (D) Six hours

N = 1

• Rewarming was successful

• Close monitoring for clinical deterioration is necessary

• The temperature of conditioned air was not specified